S. cerevisiae

Biochimie, 1977, 59(11-12), 947 - 9
{The autonomic transfer of mitochondrial factors (cytoduction) during crossing of Saccharomyces cerevisiae cells}; Zakharov IA et al.; When crossing the genetically marked yeast strains obtained from the Gif collection we observed the appearance of haploid nucleo-cytoplasmic hybrids carrying the 3 nuclear markers of the rho- parent and the mitochondrial markers (rho+ ER CR) of the other parent . The frequency of such cytoduction was about 1 per cent . The mitochondrial markers ER and CR were transmited to cytoductants together and did not segregate . The possible mechanisms of the cytoduction and its significance are discussed.

Genetika, 1977, 13(7), 1237 - 45
{Multiple mutants of Saccharomyces cerevisiae . IV . Mutability of yeast cultures at different growth stages}; Aref'eva AIa et al.; Mutability at different stages of culture growth in liquid media of two yeast strains, which revealed a property of "multiple mutability" and one strain of wild type for this property, was studied . One strain that possessed the property of "multiple mutability" showed at stationary phase a very high frequency of mutability, which reached 3.5% . It was found that multiple mutants arose in both strains, that possessed the property under investigation, at lag- and log-growth phases, and only in one strain -- at the stationary phase of growth . The possible reasons of "multiple mutability" display are discussed.

Mikrobiologiia, 1977 Jan-Feb, 46(1), 161 - 4
{Cytomorphologic characteristics of Saccharomyces cerevisiae and Candida utilis as an index of the physiologic state of the culture}; Vrana D et al.; The dimensions of daughter cells without scars, and of mother cells with 1--4 scars, of Saccharomyces cerevisiae and Candida utilis were studied in the one-stage chemostat at D equal to 0.05, 0.1, 0.25, and 0.35 hr-1 . The average dimensions of the cells increased with the specific growth rate . At low values of the specific growth rate, "immature" daughter cells separate and attain reproductive ability as independent individual organisms . A twofold increase in the biomass of yeast cells occurs at the account of growth of the buds and small daughter cells.

Mutat Res, 1977 Jan, 42(1), 45 - 50
Genetic effects of some new bifunctional and water-soluble analogs of the anti-cancer agent 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) in Saccharomyces cerevisiae; Siebert D et al.; A series of 1,1'-polymethylenebis-3-(2-chloroethyl)-3-nitrosoureas, 1-(omega-hydroxyalkyl)-3-(2-chloroethyl)-3-nitrosoureas, 1,1'(4-methyl-m-phenylenebis)-3-(2-chloroethyl)-3-nitrosourea, 2-{3-(2-chloroethyl)}-3-nitrosoureido-2-deoxy-D-glycopyranose (chlorozotocin and 1-(2-methanesulfonyloxyethyl)-3-(2-chloroethyl)-3-nitrosurea were examined for their genetic activities . BCNU was simultaneously tested as an established, clinically used reference compound . A diploid strain of Saccharomyces cerevisiae, heteroallelic at the gene loci ade2 and trp5, was used as a test system for the induction of mitotic gene conversion (intragenic recombination) . All compounds showed strong genetic effects . In the series of aliphatic bifunctional nitrosoureas, 1,1'-ethylenebis-3-(2-chloroethyl)-3-nitrosourea (1) was the most active compound . The water-soluble derivatives, including chlorozotocin, displayed all genetic effects of the same order of magnitude . There was no correlation between genetic activity and chemotherapeutic potential of the test compounds.

J Bacteriol, 1977 Jan, 129(1), 97 - 100
Fractionation of Saccharomyces cerevisiae cell populations by centrifugal elutriation; Gordon CN et al.; An exponential population of Saccharomyces cerevisiae cells was fractionated by centrifugal elutriation, using water as the elutriating liquid . Evidence that the population had been fractionated according to age in the cell cycle was obtained by examining the fractions for their size distribution, their microscopic appearance after Giemsa staining, and their ability to initiate synchronous growth.

J Bacteriol, 1977 Jan, 129(1), 47 - 51
Size and turnover of polyadenylic acid-containing ribonucleic acids in a fragile mutant of Saccharomyces cerevisiae; Venkov PV et al.; Ribonucleic acid-containing polyadenylic acid {poly(A)+-RNA} was studied in lysates from an osmotic-sensitive mutant of Saccharomyces cerevisiae characterized by low nuclease activity . The poly(A)+-RNA fraction, analyzed by electrophoresis in polyacrylamide-formamide gels, constitutes a heterogeneous population of molecules, with molecular weights ranging from 0.2 X 10(6) to 3 X 10(6) and having an average of 1.2 X 10(6) . The turnover rate of poly(A)+-RNA was determined by the decay of radioactivity after a cold uracil chase, and the observed half-life of 21 min corresponds to about 10% of the cell doubling time . Poly(A)+-RNA was analyzed by gel electrophoresis under denaturing and non-denaturing conditions . A correlation was established between the apparent secondary structure and the turnover rate of poly(A)+-RNA species.

Folia Microbiol (Praha), 1977, 22(1), 19 - 29
Activities of mitochondrial enzymes during aerobic synchronous growth of aerobically and anaerobically grown Saccharomyces cerevisiae; Nejedly K et al.; The mitochondrial enzymes cytochrome-c:O2-oxidoreductase (E.C.1.9.3.1), NADH:cytochrome-c-oxidoreductase (E.C.1.6.2.1), NADH: ferricyanide oxidoreductase (E.C.1.6.2.99), L-malate hydrolase (E.C.4.2.1.2) and L-malate:NADH-oxidoreductase (E.C.1.1.3.7) increase their activities during the aerobic synchronous growth of aerobically grown Saccharomyces cerevisiae in discrete steps and only once during the cell cycle . An identical phenomenon was observed during the aerobic synchronous growth of anaerobically grown yeast . The mechanism of completization of mitochondrial membranes is thus likely to be discontinuous and the same during both mitochondrial multiplication and the conversion of promitochondria to fully functioning mitochondria.

C R Seances Soc Biol Fil, 1977, 171(4), 879 - 82
{Autoradiography of the exchanges that can occur between murine sarcoma cells (BP 8) and yeast cells (Saccharomyces cerevisiae, complete or protoplast)}; Miegeville M et al.; We can tell after observing the resulting negative that yeasts are able, in our experimental conditions, to collect a sequence of ADN and of ARN proceeding from the cancerous cells . Then, those yeasts could turn their synthesis towards the production of new materials . If those informed yeasts were introduced into a mouse, they would induce at the level of the immunocompetent cells a specific immunizing antitumoral power.

C R Seances Soc Biol Fil, 1977, 171(4), 814 - 7
{Metabolism of nucleoside Y in a mutant strain auxotrophic for guanine (gua 2 su+) of Saccharomyces cerevisiae}; Lacharme J et al.; The study of free nucleoside Y metabolism in a mutant strain of Saccharomyces cerevisiae seems to indicate that this component is not only provided by t-RNA Phe turnover . A peculiar physiologic activity-mitogenic type - may be connected with this observation.

Eur J Biochem, 1976 Dec 11, 71(2), 393 - 8
Catalase biosynthesis in yeast: formation of catalase A and catalase T during oxygen adaptation of Saccharomyces cerevisiae; Zimniak P et al.; Catalase A from Saccharomyces cerevisiae and its biosynthetic precursors can specifically be immunoprecipitated from extracts obtained from yeast cells grown in the presence of L-{3H}leucine or 59FeCl3 . The enzyme and its precursors recognized by a specific antiserum are absent from anaerobic cells . During oxygen adaptation of yeast pre-grown on 0.3% glucose under anaerobic conditions catalase A is formed via a heme-less precursor, probably the apomonomer of the protein, and a heme-containing intermediate . When cells are grown in the presence of Tween 80 the amount of catalase A, but not of catalase T, increases 4-fold . Comparison of the mode of synthesis of catalase T and A shows that no precursor-product relationship exists between the two proteins.

Mol Gen Genet, 1976 Dec 8, 149(2), 125 - 30
Recombined molecules of mitochondrial DNA obtained from crosses between cytoplasmic petite mutants of Saccharomyces cerevisiae: the stoichiometry of parental DNA repeats within the recombined molecule; Michaelis G et al.; We have studied recombination between repetitive mitochondrial DNAs from cytoplasmic petite mutants of Saccharomyces cerevisiae . Mitochondrial DNA was isolated from two parental p- mutants, carrying respectively the CR and the ER mitochondrial genetic markers, and from two p- CRER diploid genetic recombinants . These two recombinants, obtained from the same parental petites, differ in their degrees of suppressiveness . The p- mitochondrial DNAs were analyzed by DNA-DNA hybridization, high resolution melting and reassociation kinetics . It was found that the repeating unit of the CR parental p- DNA is 3 to 4 times longer than that of the ER parent . There is very little sequence homology between these two p- mitochondrial DNAs and almost all parental sequences are integrated into the recombined molecules . Mitochondrial DNA from both types of recombinants seems to contain the two parental repeating units in the ratio 1:1.

Arch Microbiol, 1976 Dec 1, 111(1-2), 13 - 9
Correlation among turnover of nucleic acids, ribonuclease activity and sporulation ability of Saccharomyces cerevisiae; Tsuboi M; The turnover of nucleic acids and changes in ribonuclease activity during sporulation of Saccharomyces cerevisiae were studied . In the sporulating strains, 37-58% of vegatatively synthesized RNA were degraded during the sporulation process . The degree of degradation of vegetative RNA was proportional to the sporulation ability . In the non-sporulating strains, the degradation of vegetative RNA was less than 28% in the sporulation medium . Accompanied by the degradation of vegetative RNA, a ribonuclease activity increased several times during sporulation . We have found a close relation among the sporulation rate, the degree of the degradation of vegetative RNA and the increase in ribonuclease activity in the sporulation medium, using cells of which sporulation ability was repressed by changing the age or carbon source in various degrees.

Mutat Res, 1976 Dec, 41(2-3), 241 - 8
The relation between repair of DNA and radiation and chemical mutagenesis in Saccharomyces cerevisiae; Prakash L; The effect of various genes involved in DNA repair functions on radiation and chemical mutagenesis in Escherichia coli is discussed and compared to similar studies done in yeast . Results of the effect of various genes conferring radiation-sensitivity on mutation induction in yeast are presented and related to current ideas of mutagenesis.

J Gen Microbiol, 1976 Dec, 97(2), 323 - 9
Plasma membrane ultrastructural differences between the exponential and stationary phases of Saccharomyces cerevisiae as revealed by freeze-etching; Takeo K et al.; Ultrastructural changes in the plasma membrane of Saccharomyces cerevisiae during the exponential and stationary growth phases were studied by freeze-etching . In the exponential phase, plasma membrane-intercalated particles were distributed randomly . In the stationary phase, several areas of the plasma membrane showed a hexagonal arrangement of particles; these areas appeared to increase with the age of the culture . The polarity of the particles also changed partially: the E-face of the plasma membrane was only sparsely embedded with particles in exponential phase cells, but relatively densely embedded in stationary phase cells . Invaginations of the plasma membrane on the P-face were devoid of particles during both growth phases . Invaginations of the E-face were sparsely embedded with particles in exponential phase cells, but densely embedded with particles in stationary phase cells.

Genetics, 1976 Dec, 84(4), 697 - 721
Gene conversion and intragenic recombination at the SUP6 locus and the surrounding region in Saccharomyces cerevisiae; Dicarprio L et al.; Spontaneous secondary mutations of the ochre suppressor SUP6 were selected in a haploid strain of Saccharomyces cerevisiae . Unselected tetrads were dissected from crosses heterozygous for one of three allleles of SUP6 and for three other loci in this region which span a length of 14 map units (his2, cdc14 and met10) . The study showed that all of these markers were characterized by high frequency of meiotic gene conversion and long conversion lengths which frequently extended into adjacent marked loci . Despite the high conversion frequency of SUP6, recombination between alleles of this locus reached a maximum frequency of only 2 x 10(-3) protrophs/spore . Although the allelic recombination frequencies were not distance dependent and consequently could not be used to order the alleles, the inequality between the two recombinant outside marker combinations among selected intragenic recombinants produced an internally consistent map of the suppressor locus . Recombination at SUP6 (whether detected as conversion in tetrads or the production of recombinants among random spores) was accompanied by significantly less than 50% outside marker recombination.

Proc Natl Acad Sci U S A, 1976 Dec, 73(12), 4623 - 7
Genetic analysis of a transposable suppressor gene in Saccharomyces cerevisiae; Laten HM et al.; We have demonstrated in Saccharomyces cerevisiae the transposition of a gene coding for an efficient ochre (UAA) suppressor from a centromere-linked site on chromosome III to two new sites in the yeast genome . One site is on chromosome VI, very close to, if not allelic with, SUP11, one of eight genes coding for a tyrosine-inserting suppressor . The second site is on chromosome III, unlinked to the centromere and distal to the mating type locus . This site is very close to those mapped for the recessive lethal amber suppressors, SUP-RL1 and SUP61.

J Bacteriol, 1976 Dec, 128(3), 855 - 7
Regulation of thiamine transport in Saccharomyces cerevisiae; Iwashima A et al.; Yeast cells were found to be repressed for the uptake of both thiamine and pyrithiamine by growth with exogenous thiamine, and they appeared to regulate the activity of the binding protein for these compounds.

J Biol Chem, 1976 Nov 25, 251(22), 7278 - 80
Selective inhibition of protein synthesis initiation in Saccharomyces cerevisiae by low concentrations of cycloheximide; Cooper TG et al.; We have previously determined the amounts of time required to complete various macromolecular synthetic processes needed for induction of allophanate hydrolase in Saccharomyces cerevisiae . This information provided a means of testing, in vivo, an early hypothesis suggesting that cycloheximide inhibited the initiation as well as elongation steps of protein synthesis . Our data suggest that initiation of protein synthesis in yeast may be inhibited by low concentrations of cycloheximide which do not significantly affect polypeptide chain elongation.

Mol Gen Genet, 1976 Nov 17, 148(3), 251 - 61
A novel class of Saccharomyces cerevisiae mutants specifically UV-sensitive to "petite" induction; Moustacchi E et al.; A mutant of Saccharomyces cerevisiae has been isolated which, though exhibiting a normal response to nuclear genetic damage by ultraviolet light (UV), is more sensitive than its wild type specifically in the production of the cytoplasmic (rho-) mutation by this agent . Some of the features of this mutation which has been designated uvsrho 5 are: i) The mutation is recessive, it exhibits a Mendelian, and hence presumably nuclear, pattern of segregation, but manifests its effects specifically and pleiotropically on mitochondrial functions . ii) Mutant cells resemble their wild type parents in a) growth characteristics on glucose; b) in their UV induced dose response to lethality or nuclear mutation and c) the ability of their mitochondrial genome, upon mating with appropriate testers, of transmitting and recombining various markers, albeit with enhanced efficiency . Similarly, d) they are able to modulate the expression of mitochondrial mutagenesis by ethidium bromide . Thus their mitochondrial DNA appears genetically as competent as that of the wild type . iii) Mutant cells differ from their wild type parents in a) growth characteristics on glycerol; b) susceptibility to induction of the mitochondrial (rho-) mutation by various mutagens, in that the rate of spontaneous mutation is slightly and that by UV is significantly enhanced, whild that by ethidium bromide is greatly diminished . Conversely, c) modulating influences resulting in the repair of initial damage are diminished fro UV and stimulated in the case of Berenil . iv) The amount of mitochondrial DNA per cell appears elevated in the mutant, relative to wild type, and its rate of degradation subsequent to a mutagenic exposure to either UV or ethidium bromide is diminished . v) A self-consistent scheme to account for this and all other information so far available for the induction and modulation of the (rho-) mutation is presented . In a previous study it was shown that some nuclear mutants of Saccharomyces cerevisiae, more sensitive to lethal damage induced by ultraviolet light (rad) than their parent wild type (RAD), also exhibit a concomitant modification in sensitivity to both nuclear and cytoplasmic genetic damage (Moustacchi, 1971) . However, another class of rad mutants respond to the induction of the cytoplasmic "petite" also designated as rho- (or rho-) mutation by UV in a manner indistinguishable from that of the RAD strain . One possible interpretation of this last observation is that some of the steps in the expression of the UV damage on mitochondrial (mt)DNA may be governed by other nuclear and cytoplasmic genetic determinants, the products of which may then act specifically on mitochondrial lesions . If this assumption is correct, it should be possible to find mutants with a normal response to nuclear damage but specifically UV-sensitive towards induction of (rho-)...

Mol Gen Genet, 1976 Nov 17, 148(3), 233 - 41
Restriction endonuclease analysis of ribosomal DNA from Saccharomyces cerevisiae; Cramer JH et al.; The size and degree of homogeneity of the repetitive units in purified ribosomal DNA (gamma DNA) from Saccharomyces cerevisiae have been analyzed by restriction endonuclease digestion and heteroduplex mapping . Digestion of the gamma DNA with EcoRI yields seven fragments, digestion with Hind II+III yields five fragments, digestion with Hind III alone yields two fragments, and digestion with Sma I yields one fragment . The sum of the fragment molecular weights after digestion with each of the endonucleases is 5.5-5.6 x 10(6) . When the DNA strands of the Sma I fragment are dissociated and reannealed, only homoduplexes are formed . We have concluded from these results that the repeating units in yeast ribosomal DNA are 5.6 x 10(6) datons and are homogeneous in size and composition.

Mutat Res, 1976 Nov, 37(2-3), 201 - 12
Genetic effects induced in Saccharomyces cerevisiae by cyclophosphamide in vitro without liver enzyme preparations; Mayer VW et al.; Cyclophosphamide induced forward mutation in Saccharomyces cerevisiae strain S288C and mitotic recombination in strains D3 and D5 but not in strain D4 . The yeast cells were treated with the compound in phosphate buffer without recourse to metabolic activation protocols . Elevation of the treatment temperature increased the genetic activity of cyclophosphamide . Respiration-deficient isolates of strains S288C and D3 were more sensitive than the respiratory competent parent strains were for inducing forward mutation and mitotic recombination, respectively . Cyclophosphamide was incubated in phosphate buffer alone for increasing time intervals; strain D3 cells were added to aliquots for each time interval and incubated for an additional 30 min . The frequency of induced recombination increased as the time of compound incubation increased, showing that spontaneous degradation of cyclophosphamide to genetically active breakdown products was responsible for the genetic damage induced in the yeast cells.

J Cell Sci, 1976 Nov, 22(2), 219 - 42
Electron-microscopic study of the spindle and chromosome movement in the yeast Saccharomyces cerevisiae; Peterson JB et al.; Mitosis in yeast Saccharomyces cerevisiae was investigated in thick (0-25-I mum) serial sections with a high voltage electron microscope and in preparations of spheroplasts spread on a water surface . Spindle microtubules originate from a plaque-like structure called the spindle pole bosis the SPB duplicates and a set of long and short microtubules develops on each SPB . The spindle arises as the SPBs separate on the nuclear membrane adense and are not individually visible . Genetic studies, however, have indicated that there are 17 linkage groups . The number of microtubules was determined in diploid and haploid spindles on serial stereo micrographs . In diploid mitosis about 40 microtubules issue from a SPB . Most are non-continuous and often they are visibly associated with a chromatin fibre . The spindle in haploid cells is similar except that the number of microtubules is about half that in diploid cells and the SPB is smaller . The pole-to-pole microtubules vary in number from spindle to spindle, but in each case enough microtubules are present to account for each linkage group being associated with a single non-continuous microtubule . We conclude that mitosis in yeast is comparable in its general aspect to that observed in typical eukaryotes.

J Bacteriol, 1976 Nov, 128(2), 689 - 91
Adenosine utilization in cordycepin-sensitive mutants of Saccharomyces cerevisiae; Anderson JM et al.; A purine-requiring, wild-type yeast strain was cordycepin resistant and failed to grow in medium containing adenosine; in contrast, a cordycepin-sensitive mutant (also purine requiring) grew well in medium containing adenosine . The cordycepin-sensitive mutant incorporated {8-14C}adenosine at nine times the wild-type rate, and adenosine completely fulfilled the purine requirement of the cells . Exogenous adenosine rapidly entered the mutant cells, apparently as free nucleoside, and was phosphorylated; uptake displayed concentration-dependent saturation kinetics (Km, 6 mM) . Within 10 min 14C radioactivity was being incorporated into nucleic acids.

Mol Gen Genet, 1976 Oct 18, 148(2), 165 - 70
The induction of mitotic gene conversion by chemical and physical mutagens as a function of culture age in the yeast, Saccharomyces cerevisiae; Davies PJ et al.; Cultures of yeast progressing from the exponential to the stationary phase of growth show increased resistance to the lethal effects of the chemical mutagens nitrous acid, ethyl methane sulphonate and mitomycin C and increased sensitivity to the lethal effects of UV light . Induced mitotic intragenic recombination produced by gene conversion also shows variation in its response to the growth phase after mutagen treatment . Higher frequencies of recombination per surviving cell were found after nitrous acid and ethyl methane sulphonate treatment of stationary phase cells whereas identical frequencies were produced by UV and mitomycin C treatment in both growth phases . The results were consistent with the hypothesis that the more nitrous acid and ethyl methane sulphonate resistant stationary phase cells were more active in postreplication repair . The sensitivity of exponential phase cells to nitrous acid and ethyl methane sulphonate may result from both increased mutagen uptake and reduced postreplication repair activity . In contrast, irrespective of growth phase all cells surviving UV and mitomycin C treatment appear to have undergone identical levels of post-replication repair.

J Gen Microbiol, 1976 Oct, 96(2), 263 - 8
Amino-acid pool composition of Saccharomyces cerevisiae as a function of growth rate and amino-acid nitrogen source; Watson TG; The composition of the amino-acid pool of Saccharomyces cerevisiae is markedly influenced by the amino-acid nitrogen source . The yeast tends to accumulate the amino acid supplied and those closely related to it metabolically . A relatively high concentration of glutamic acid is maintained in the pools of all cultures irrespective of the nitrogen source, reflecting the central role of glutamic acid in nitrogen metabolism . The total amino-acid pool concentration increases as a function of growth rate, although differences exist in the behaviour of individual amino acids.

Proc Natl Acad Sci U S A, 1976 Oct, 73(10), 3651 - 5
A mutant of Saccharomyces cerevisiae defective for nuclear fusion; Conde J et al.; A mutant unable to fuse nuclei during mating has been isolated from standard wild-type Saccharomyces cerevisiae . Tetrad analysis of the mutation responsible for this defect (kar1-1) shows that it segregates as a single Mendelian factor . The defect kn kaf1-1 appears to be nuclear limited . Cytological and genetic evidence shows that in this mutant the events associated with zygote formation are normal until the point of nuclear fusion . The consequence of this defect is the formation of a multinucleate zygote which in subsequent divisions can segregate heterokaryons and haploid heterplasmons.

J Bacteriol, 1976 Oct, 128(1), 49 - 55
Regulation of arginine biosynthesis in Saccharomyces cerevisiae: isolation of a cis-dominant, constitutive mutant for ornithine carbamoyltransferase synthesis; Messenguy F; A cis-dominant mutation linked to argF, the structural gene specifying ornithine carbamoyltransferase, and affecting the control of the synthesis of this enzyme has been obtained . The level of ornithine carbamoyltransferase in this mutation is depressed and less repressible by addition of L-arginine than it is in the wild-type strain . Of 38 tetrads analyzed, resulting from a cross of a strain harboring this mutation with a strain carrying an argF- mutation, none was a tetratype or a nonparental ditype . This operator mutation helps to define a negative mode of control of the synthesis of the arginine biosynthetic enzymes, as had been suggested earlier upon the isolation of argRI- (arg80), argRII- (arg81), and argRIII- (arg82) specific regulatory mutations.

Genetics, 1976 Sep, 84(1), 27 - 42
A study of the transmission and structure of double stranded RNAs associated with the killer phenomenon in Saccharomyces cerevisiae; Sweeney TK et al.; Killer strains contain two double stranded RNAs, L and M.The M dsRNA appears to be necessary for production of a toxin and for resistance to that toxin . Mutant strains have been found that are defective in their ability to kill and in their resistance to toxin . These sensitive, non-killer strains have altered dsRNA composition . One class has no M dsRNA.Another class of sensitive, non-killers called suppressives has no M dsRNA but instead has smaller dsRNAscalledS.Indiploidsresulting from a cross of a wild-type killer by a suppressive the transmission of the M dsRNA is suppressed by the S dsRNA.When a suppressive is crossed by a strain with no M dsRNA, the diploids and all four meiotic spores have the S dsRNA characteristic of the parental suppressive strain . Suppressive strains do not suppress each other . Intercrosses between two different suppressives yields diploids with both parental S dsRNAs . These two S dsRNAs are transmitted to all 4 meiotic progeny . Another class of mutants has been found which is defective for one of the traits but retains the other . One type, temperature-sensitive killers, has a normal dsRNA composition but is unable to kill at 30 degrees . The other type, immunity-minus, has a complex dsRNA pattern . The immunity-minus strain is extremely unstable during mitotic growth and segregates several different types of non-killers . Analysis of the dsRNAs from wild type and the mutants by electron microscopy shows that the L, M, and S dsRNAs are linear . All strains regardless of killer phenotype appear to have the same size L dsRNA.

Arch Microbiol, 1976 Sep 1, 109(3), 221 - 5
Inactivation by glucose of phosphoenolpyruvate carboxykinase from Saccharomyces cerevisiae; Gancedo C et al.; Phosphoenolpyruvate carboxykinase showed high activity in Saccharomyces cerevisiae grown on gluconeogenic carbon sources . Addition of glucose to such cultures caused a rapid loss of the phosphoenolpyruvate carboxykinase activity . Fructose or mannose had the same effect as glucose, while 2-deoxyglucose or galactose were without effect . The inactivation was an irreversible process, since the regain of the activity was dependent of de novo protein synthesis . Cycloheximide did not prevent inactivation . All strains of the genus Saccharomyces tested showed inactivation of their phosphoenolpyruvate carboxykinase upon addition of glucose; this behaviour was not restricted to this genus.

J Gen Microbiol, 1976 Sep, 96(1), 165 - 74
Role of wall phosphomannan in flocculation of Saccharomyces cerevisiae; Jayatissa PM et al.; Treatment with 60% hydrofluoric acid (HF) removed most of the phosphorus and small amounts of mannan, glucan and protein from walls of two non-flocculent strains (NCYC366 and NCYC1004) and two flocculent strains (NCYC1005 and NCYC1063) of Saccharomyces cerevisiae . Organisms of all strains showed increased flocculating ability following HF treatment . Flocculation of untreated organisms of NCYC1005 and NCYC1063, and of HF-treated organisms of all four strains, declined appreciably when they were washed in deionized water, with or without EDTA, and the flocculation was measured in deionized water instead of in 0-05 M-sodium acetate containing Ca2+ . Treatment with 1,2-epoxypropane also caused a decrease in the flocculating ability of these organisms . Extracting the lipids from organisms of strains NCYC366 and NCYC1004 had no effect on their flocculating ability, but decreased the flocculating ability of organisms of strains NCYC1005 and NCYC1063 . pH-electrophoretic mobility curves of untreated and HF-treated organisms confirmed the loss of wall phosphate by HF treatment, and indicated that HF treatment had little effect on the content of protein carboxyl groups in the outer wall layers . Mannose at 0-22 M completely prevented floc formation by organisms of strain NCYC1063; but, even at 0-33 M, it had very little effect on floc formation by HF-treated organisms of strains NCYC366 and NCYC1063 . Organisms of all four strains bound fluorescein-conjugated concanavalin A to the same extent after treatment with HF as before, but this treatment led to a greatly diminished binding of of fluorescein-conjugated antiserum raised against organisms of strain NCYC366 . The results indicate that phosphodiester linkages in yeast-wall mannan are not involved in bride formation through Ca2+ during floc formation and that this arises principally through carboxyl groups.

Biochim Biophys Acta, 1976 Aug 23, 441(2), 294 - 301
Isolation and characterization of the liponucleotides of Saccharomyces cerevisiae; Schneider EG et al.; The liponucleotide fraction of Saccharomyces cerevisiae was isolated from cells grown on tritiated uracil and identified as CDPdiacylglycerol on the basis of (1), its behavior as a single compound upon DEAE-cellulose and thin-layer chromatography; (2), its extreme lability to mild alkaline methanolysis; and (3), its hydrolysis by the CDPdiacylglycerol hydrolase of Escherichia coli to yield tritiated 5'-CMP . At most, only about 5% of yeast liponucleotide could be dCDPdiacylglycerol, in contrast to the presence of nearly equimolar amounts of CDP-and dCDPdiacylglycerols in E . coli . Although no CDPceramide could be detected in the liponucleotide fraction of this organism, the possibility still exists that it may be an intermediate in the biosynthesis of sphingolipids in systems yet to be examined.

Mol Gen Genet, 1976 Aug 19, 147(2), 209 - 15
A simple method for the isolation and characterization of thymidylate uptaking mutants in Saccharomyces cerevisiae; Brendel M; The mutant tmpl--10ts which confers thermosensitive auxotrophy for thymidylate is employed for the selection of 5'-dTMP uptaking mutants . At the nonpermissive temperature yeast cells phenotypically wild type for thymidylate uptake can grow for only 3 to 4 generations in the presence of 10(-2) M 5'-dTMP . Thymidylate utilizing mutants (tum mutants) were isolated which can grow in the presence of 12 to 24 mug 5'-dTMP/ml . Genetical analysis revealed one of these mutant strains to be a double mutant, tuml tum2 . For normal growth haploid thymidylate auxotrophic strains require approximately 360 mug 5'-dTMP/ml when tuml and 24 mug 5'-dTMP when tum2 is present, respectively . Cells prototrophic for thymidylate (TMP) harbouring tuml tum2 will also take up 5'-dTMP and incorporate it specifically into their DNA . Thymidylate utilization in such strains is independent of functional mitochondria, as similar incorporation of labelled 5'-dTMP is found in isogenic strains with rho+, rho- and rho0 status . Optimal stimulation of the 5'-dTMP uptaking principle in haploid TMP strains is found at 4 mug5'-dTMP/ml when tuml and tum2 are present.

Genetics, 1976 Aug, 83(4), 655 - 66
Mutators in Saccharomyces cerevisiae: MUT1-1, MUT1-2 and MUT2-1; Gottlieb DJ et al.; The purpose of this study was to characterize two mutator stocks of yeast which were induced and selected on the basis of high spontaneous reversion rates of the suppressible "ochre" nonsense allele lys1-1 . In the mutator stock VA-3, a single mutation, designated mut1-1, is responsible for the increase in the reversion rate of the ochre alleles lys1-1 and arg4-17 . In stock VA-105, there are two separate mutator mutations . Tetrad analysis data showed these two loci are loosely linked . Based on complementation data, one of these mutations is at the same locus as mut1-1 and designated mut1-2 . The second mutator of stock VA-105 was designated mut2-1 . All three mutators are recessive . Both mut1-1 and mut1-2 give a high mutation rate for ochre nonsense suppressor (SUP) loci, but not for the ochre nonsense alleles . On the contrary, the mutation rates of the ochre alleles are greatly reduced . With the mutant mut2-1 there were mutations at both the lys1-1 site and its suppressors; mut2-1 is as effective as mut1-2 but not as effective as mut1-1 in inducing reversions of a missense mutant, his1-7 . Neither mut1-1, mut1-2 nor mut2-1 were effective in inducing reversions of a putative frameshift mutation, hom3-10, or in inducing forward mutations to canavanine resistance.

Genetics, 1976 Aug, 83(4), 645 - 53
Mutator activity of petite strains of Saccharomyces cerevisiae; Flury F et al.; Petite strains in Saccharomyces exhibit enhanced spontaneous mutation rates of nuclear genes regardless of whether they are cytoplasmically or nuclearly inherited, or whether or not the cytoplasmic petite strains have mitochondrial DNA . In petite strains, the mutation rate for the nonsense allele lys1-1 is enhanced by a factor of 3-6 and for the missense allele his1-7 by a factor of 2 as compared with their grande counterparts . The reversion of a third allele, the putative frameshift mutation, hom3-10, is not enhanced in a petite background . The results indicate that the spontaneous mutation rate of an organism can be altered by indirect intracellular influences.

Proc Natl Acad Sci U S A, 1976 Aug, 73(8), 2828 - 32
Recombination in Saccharomyces cerevisiae: a DNA repair mutation associated with elevated mitotic gene conversion; Boram WR et al.; A mutant haploid strain of Saccharomyces cerevisiae has been isolated that is sensitive to the alkylating agent methyl methanesulfonate at a concentration of 0.01% (vol/vol) . The strain also shows sensitivities to x-rays and ultra-violet light, which cosegregate with sensitivity to methyl methanesulfonate as a single gene defect . An analysis of the sensitivity to ultraviolet light indicates that the mutation interferes with the excision of pyrimidine dimers . Diploids homozygous for the mutant gene exhibit elevated frequencies of spontaneous mitotic recombination at the ade6 locus . The results indicate that all the events are due to gene conversion . Mitotic recombination was also found to be elevated for three loci other than ade6 . Thus, the recombinational effect seems not to be locus specific . Linkage and allelism tests indicate that the mutation is an allele of the known radiation-sensitive gene rad18 . The various effects of this new rad18 allele (rad18-3) are discussed in terms of a defect in DNA repair mechanisms.

Heredity, 1976 Aug, 37(1), 129 - 34
The genetic control of DS-RNA virus-like particles associated with Saccharomyces cerevisiae killer yeast; Mitchell DJ et al.; Previous results have indicated that laboratory strains of yeast possessing two types of dsRNA virus-like particles, V1 and V2, are capable of producing a killer toxin which kills sensitive strains . This paper reports on genetic crosses which correlate the presence of these particles both with a host nuclear gene +/-/mak1 and with the production of a killer toxin . The results show that: (i) V1 particles are inherited independently of the +/-/mak1 gene . (ii) V2 particles are present only in combination with those of V1 and the +/- allele of the +/-/mak1 nuclear gene.

Mol Gen Genet, 1976 Jul 23, 146(2), 133 - 7
Cytoplasmic inheritance of antimycin A resistance in Saccharomyces cerevisiae; Michaelis G; Three antimycin resistant mutants of Saccharomyces cerevisiae are characterized genetically . The mutations have been shown to be cytoplasmically inherited by four criteria . The phenotype persists in diploids formed by a cross with a pO strain of yeast of the opposite mating type . Diploids heterozygous for the antimycin marker, however, show segregation of the resistance and sensitivity during mitosis . Tetrad analysis indicates a non-Mendelian segregation (4:0 and 0:4) of the mutations . The antimycin marker can be eliminated by ethidium bromide treatment under conditions that should have deleted all of the mitochondrial DNA.

Mol Gen Genet, 1976 Jul 23, 146(2), 117 - 32
Mapping of mitochondrial genes in Saccharomyces cerevisiae . Populations and pedigree analysis of retention or loss of four genetic markers in Rho-cells; Schweyen RJ et al.; 1 . Retention or loss of mitochondrial markers CR321, OR1, PR454, TR (gene loci RIB1, OLI1, PAR1, TSM1 respectively has been analysed in a large number of ethidium bromide induced primary rho-clones . Retention of one or more of the four markers with a single clone was observed frequently, only 20 to 25% of clones were found to be (TOCOOOPO) . Primary clones retaining two or more of the four markers were found to be mixed, i.e . the primary rho- cell contained a heterogeneous population of variously deleted mitDNA molecules which segregated into different cell lines in the corresponding primary clone . 2 . A representative sample of the population of ethidium bromide induced rho- mutants has been analysed by a first subcloning performed after some 30 cell generations of vegetative multiplication in the abscence of the drug . At this level the heterogeneous population of mitDNA molecules, generated by the mutagenic treatment in the primary cell, has been sorted out . The cells forming secondary clones are thus essentially homoplasmic . In contrast to primary clones, genotypes of secondary clones therefore could be determined unambiguously, and the frequency of cell types can be regarded as a faithful representation of the frequency of mitDNA molecules . Retention of markers was low, in less than 2% of secondary clones one or several markers have been found . This observation has been interpreted as indicating that induction of rho-mutants by ethidium bromide is accompanied by deletion of very large sequences of mitDNA in a very large fraction of mitDNA molecules . 3 . Five individual rho-clones retaining the four markers TRCRORPR have been isolated and analysed for spontaneous deletion of one or several of these markers during successive subclonings (pedigree analysis) . High genetic stability (98-99.5% per cell generation) has been observed in these clones . 4 . A method has been developed allowing an unambiguous determination of the order of the four markers on a circular map . It is based on the concomitant loss of two markers and retention of the other two markers (double loss/double retention analysis) . The results of four out of five pedigrees of individual rho-clones analysed (spontaneous deletion) and the results of the analysis of populations of secondary rho-clones (ethidium bromide induced deletion) were in full agreement and the order of genes has been determined as being P-T-C-O-P . In the fifth pedigree results suggest an inversion of the T and C markers . 5 . Relative distances between pairs of markers have been derived from the frequencies of separation of markers by deletion and were found to be C-T less than C-O less than T-O less than T-P less than C-P less than O-P . Linkage of the four markers could be established, and distances calculated are additive . 6 . The general relevance of this approach of mapping by deletion and the methods used for the determination of order and distances of mitochondrial genes has been discussed . (ABSTRACT TRUNCATED)

Mol Gen Genet, 1976 Jul 5, 146(1), 95 - 100
Differential effects of nalidixate on the cell growth of respiratory competent strains and cytoplasmic petite mutants of Saccharomyces cerevisiae; Carnevali F et al.; Sodium nalidixate inhibited the cell growth and division of several respiratory competent strains of Saccharomyces cerevisiae . A number of cytoplasmic petite strains (both spontaneous and induced by ethidium bromide) were shown to be more resistant to sodium nalidixate than the wild-type strains from which they were derived . There was considerable variation in sensitivity of different petites derived from the same wild-type . Usually petite strains which were induced by ethidium bromide were more resistant than spontaneously arising petites . The susceptibility of a wild-type strain to nalidixate was found to be least when the mitochondrial respiratory system was maximally repressed . It was also noted that sodium nalidixate (100 mug/ml) induced petite mutants.

Mol Gen Genet, 1976 Jul 5, 146(1), 89 - 93
Effect of caffeine on the rho- -induction with ethidium bromide in Saccharomyces cerevisiae; Wolf K et al.; It is shown that caffeine antagonizes petite-induction with ethidium bromide under non-growth conditions when administered during or after mutagenic treatment . Caffeine itself is shown to be a petite-inducing agent when cells are grown in liquid glucose-complete-medium in the presence of the drug . A possible mode of action of caffeine in the ethidium bromide induced petite-mutagenesis is discussed.

Mol Gen Genet, 1976 Jul 5, 146(1), 55 - 9
DNA Degradation and reduced recombination following UV irradiation during meiosis in yeast (Saccharomyces cerevisiae); Salts Y et al.; Irradiation of meiotic yeast cells with moderate doses of ultraviolet irradiation (1,600 erg/mm2) leads to the arrest of premeiotic DNA synthesis, massive (5-40%) DNA degradation, and a 40-50% loss of cell viability . In contrast, such doses of UV irradiation had a minor effect on viability (15-20% loss) of logarithmically growing cells, and no comparable DNA degradation was observed in irradiated synchronized vegetative cells . Meiotic recombination is also affected by UV irradiation . When administered at a stage comparable to meiotic prophase, low doses of irradiation result in a reduction in recombination frequency without significantly affecting cell viability.

Mol Gen Genet, 1976 Jul 5, 146(1), 27 - 35
The effects of "cell age" upon the lethal effects of physical and chemical mutagens in the yeast, Saccharomyces cerevisiae; Parry JM et al.; Yeast cultures progressing from the exponential to the stationary phase of growth showed changes in cell sensitivity to physical agents such as UV light, heat shock at 52 degrees C and the chemical mutagens ethyl methane sulphonate, nitrous acid and mitomycin C . Exponential phree chemicals . The increased resistance of exponential phase cells to UV light was shown to be dependent upon the functional integrity of the RAD50 gene . Treatment of growing yeast cultures with radioactively labelled ethyl methane sulphonate indicated the preferential uptake of radioactivity during the sensitive exponential stage of growth . The results indicated that the differential uptake of the chemical mutagens was responsible for at least a fraction of the variations in cell sensitivity observed in yeast cultures at different phases of growth.

Biokhimiia, 1976 Jul, 41(6), 1121 - 6
{Degradation of intracellular proteins at different stages of growth of Saccharomyces cerevisiae}; Bakalkin GIa et al.; The rate of degradation of intracellular proteins at different growth stages of Saccharomyces cerevisiae yeast was determined . It has been demonstrated that the rate of degradation of intracellular proteins increases 2--3-fold at the late exponential phase . The increase was accompanied by corresponding changes in the activities of yeast proteinases A and B . In the presence of specific yeast proteinase inhibitors (pepstatin and phenylmethylsulfonyl fluoride) the rate of protein degradation in vivo decreased . The intermediate products of cell protein degradation have been found . These TCA-insoluble products could be extracted by various solvent systems . Their subsequent brakdown was suppressed by specific proteinase inhibitors.

Hoppe Seylers Z Physiol Chem, 1976 Jul, 357(7), 961 - 70
Localization of catalase A in vacuoles of Saccharomyces cerevisiae: evidence for the vacuolar nature of isolated "yeast peroxisomes"; Susani M et al.; The subcellular distribution of catalase A in the yeast Saccharomyces cerevisiae has been investigated . The enzyme was found to be bound to large particles, whereas most of the activity of catalase T was located in a 38 000 X g supernatant . Under various isolation conditions catalase A always showed a distribution among subcellular fractions virtually identical to that of two markers for vacuoles, proteinase B and alpha-mannosidase . More than 80 percent of the catalase A activity of a crude vacuole fraci-onercent of the catalase A activity of a crude vacuole fraction has been detected in purified vacuoles . Malate synthase, isocitrate lyase and glyoxylate reductase (NADP), three peroxisomal markers, showed a subcellular distribution significantly different from that of catalase A . It is concluded from these results that catalase A is specifically associated with the vacuoles of yeast . Like vacuoles, "peroxisomal" fractions isolated from yeast spheroplasts as described by Avers{1} contain only one catalase protein, catalase A . It could be shown by isopycnic and sedimentation velocity separations of crude mitochondrial fractions that catalase A in "peroxisomal" fractions is accompanied by considerable activities of proteinase B and alpha-mannosidase . From all our results it seems that the catalase-active particles isolated under such conditions are not typical peroxisomes but vesicles formed from vacuoles during the isolation procedure.

Int J Radiat Biol Relat Stud Phys Chem Med, 1976 Jul, 30(1), 13 - 24
The genetic control of liquid-holding recovery and U.V.-induced repair resistance in the yeast, Saccharomyces cerevisiae; Parry EM et al.; Liquid-holding treatment in non-nutrient solutions after U.V.-exposure results in an increased resistance of wild-type (RAD) yeast cells to a second U.V.-treatment (repair resistance) . U.V.-sensitive (rad) mutants of yeast which show variation in their response to liquid-holding treatment and a second U.V.-dose-range have been classified into two groups . Mutants of Group 1 show increased viability after post-U.V.-liquid-holding treatment and show repair resistance . In contrast, mutants of Group 2 which show reduced viability during post-U.V.-liquid-holding treatment have the same U.V.-sensitivity, both before and after liquid-holding treatment . Genetic analysis of crosses of the rad mutants to wild-type cultures indicate that the phenotype of repair resistance to U.V.-treatment is under genetic control and depends on the presence of alleles of radiation sensitivity genes, which also confer the property of liquid-holding recovery.

Mutat Res, 1976 Jul, 36(1), 49 - 66
The detection of monosomic colonies produced by mitotic chromosome non-disjunction in the yeast Saccharomyces cerevisiae; Parry JM et al.; A diploid yeast strain, D6 is described which monitors mitotic non-disjunction by the phenotypic expression of a set of coupled and recessive markers flanking the centromere of chromosome VII . These markers are not expressed in the heterozygous condition prevailing in D6 . The left arm of chromosome VII carries a tightly centromere linked marker, leu1 (leucine requirement), distal to leu1 in this order: trp5 (tryptophan requirement), cyh2 (recessive resistance to cycloheximide) and met 13 (requirement for methionine) . The right arm is marked with ade3 (simultaneous requirement for adenine and histidine) . D6 is homozygous for ade2 and consequently, forms red rather than the normally white colonies . It shows no requirement for the above amino acids and it is sensitive to cycloheximide . Unmasking of all the markers on chromosome VII leads to colonies that are white because ade3 sets a block preceding the ade2 block (which causes the accumulation of a precursor of the red pigment), they require leucine, tryptophan and methionine, and grow on media with cycloheximide . Cells are plated on a cycloheximide medium where red and white colonies are formed . Colonies of spontaneous origin were tested . The majority of the white colonies expressed all the recessive markers whereas only few of the red colonies expressed all the markers on the left arm of chromosome VII . Basically expression of recessive markers on both sides of the centromere can be explained as a result of two coincident events of mitotic crossing over . However, the frequency of colonies expressing centromere linked leu1 was 14 times higher among the white types than the red ones . This suggested that the white, cycloheximide resistant, leucine requiring colonies arose by mitotic non-disjunction and not only by two coincident mitotic crossing over events . Presumptive spontaneous monosomic segregants were placed on sporulation medium . Only 8 out of 30 isolates sporulated, which showed that these eight segregants were diploid at the time of sporulation . They could have arisen by two coincident crossover events or through restoration of a normal disomic condition after non-disjunction had occurred . The genetic data thus leaves us with only its statistical argument in favour of non-disjunction . Further confirmation of monosomic nature of the white cycloheximide resistant colonies was provided by the estimates of their DNA contents . Compared to the stock wild type diploids the presumptive monosomics showed a reduction in DNA content . We have utilized D6 to investigate the possible induction of mitotic non-disjunction after treatment with gamma rays, heat shock at 52 degrees C and ultraviolet irradiation . In all cases white, cycloheximide resistant colonies were produced at levels significantly higher than that found in untreated cultures . In order to detect the production of monosomic cells, treated cultures were grown for 48 h in non-selective medium after exposure to allow for "expression" of the monosomic condition.

J Bacteriol, 1976 Jul, 127(1), 67 - 75
Fragility of plasma membranes in Saccharomyces cerevisiae enriched with different sterols; Hossack JA et al.; Saccharomyces cerevisiae NCYC 366, grown under strictly anaerobic conditions to induce requirements for an unsaturated fatty acid (supplied by Tween 80) and a sterol, contained free sterol fractions enriched to the extent of 67 to 93% with the exogenously supplied sterol (campesterol, cholesterol, 7-dehydrocholesterol, 22, 23-dihydrobrassicasterol, beta-sitosterol, or stigmasterol) . Cells enriched in any one of the sterols did not differ in volume, growth rate, contents of free sterol, esters and phospholipids, or phospholipid composition . Cholesterol-enriched cells contained about 2% more lipid than cells enriched in any of the other sterols, which was largely accounted for by increased contents of triacylglycerols and, to a lesser extent, esterified sterols . Phospholipids were enriched to the extent of about 52 to 63% with C18:1 residues . Cells enriched in ergosterol or stigmasterol were slightly less susceptible to the action of a wall-digesting basidiomycete glucanase than cells enriched with any one of the other sterols . The capacity of the plasma membrane to resist stretching, as indicated by the stability and volume of spheroplasts suspended in hypotonic solutions of buffered sorbitol (particularly in the range 0.9 to 0.7 M), was greater with spheroplasts enriched in sterols with an unsaturated side chain at C17 (ergosterol or stigmasterol) than with any of the other sterols . Plasma membranes were obtained from spheroplasts enriched in cholesterol or stigmasterol and had free sterol fractions containing 70 and 71%, respectively, of the sterol supplied exogenously to the cells . The sterol-phospholipid molar ratios in these membranes were, respectively, 1:7 and 1:8.

J Bacteriol, 1976 Jul, 127(1), 610 - 8
Morphogenic effects of alpha-factor on Saccharomyces cerevisiae a cells; Lipke PN et al.; Saccharomyces cerevisiae mating type a cells enlarged and elongated when exposed to alpha-factor, a sex pheromone produced by mating-type alpha cells . This morphogensis required exogenous-D-glucose, nitrogen, and phosphate, and cells in exponential phase responded better than stationary-phase cells . Morphogenesis was blocked by cycloheximide and by inhibitors of cell wall biosynthesis such as 2-deoxy-D-glucose, 2-deoxy-2-fluoro-D-glucose, and 2-deoxy-2-fluoro-D-mannose, but not by polyoxin D . One to two hours after addition of pheromone, a cells became more susceptible to lysis by glucanases, a change that was dependendent on the dose of alpha-factor and was blocked by drugs that block morphogenesis . On the other hand, treatment with alpha-factor did not increase susceptibility to attack by trypsin, subtilisin, or exo-alpha-mannanase . Radioactive label, incorporated into cell wall polysaccharides during treatment with alpha-factor, was not secreted into the medium during morphogenesis . Analysis of the labeled wall polymers showed that alpha-factor-treated cells contain more glucan and less mannan than control cells, and that the mannan of treated cells contains an increased proportion of shorter side chains and unsubstituted backbone mannose units . Thin-section electron microscopy of treated cells revealed that the cell wall possesses a diffuse outer layer in the extension and is thinner at the tip.

J Bacteriol, 1976 Jul, 127(1), 128 - 34
Influence of pH on the rate of ribosomal ribonucleic acid synthesis during sporulation in Saccharomyces cerevisiae; Wejksnora P et al.; The rate of synthesis of ribosomal RNA (rRNA) is much slower during sporulation than during vegetative growth of yeast . If sporulating cells are transferred from normal incubation conditions at pH 8.8 to the same medium adjusted to pH 7.0, the rate of rRNA synthesis increased to approach that observed in vegetative cells . The response to the pH change is quite rapid, occurring within 10 min . THE PH-dependent, rate-limiting step appears to be in the processing of 35S ribosomal precursor RNA to the final 26S and 18S RNA species . A similar pH effect also was found for the rate of protein synthesis . However, no change in respiration was observed when the pH was lowered . These results indicate that the observed differences in rate of rRNA synthesis in vegetative and sporulating cells are a consequence of pH and are not intrinsic to sporulation . The results also support the correlation between rRNA processing and protein synthesis.

Mol Gen Genet, 1976 Jun 15, 145(3), 327 - 33
Cis-dominant regulatory mutations affecting the formation of glucose-repressible alcohol dehydrogenase (ADHII) in Saccharomyces cerevisiae; Ciriacy M; The formation of ADHII in Saccharomyces cerevisiae is regulated by carbon catabolite repression . There are two genes involved in the formation of ADHII: ADR2, the structural gene as identified by electrophoretic variants and ADR1, possibly a regulatory gene . A new genetic element involved in the regulation of ADHII was identified by three allelic mutants insensitive to strong glucose repression . They were called ADR3c (wild type designation ADR3) and found to be tightly linked to the structural gene, ADR2 . The alcohol dehydrogenase found in ADR3c mutants could not be distinguished electrophoretically from the ADHII of the glucose-sensitive wild type, ADR3 . Dominance relations between ADR3c and ADR3 were established in diploids heterozygous for ADR3 and the two alleles of ADR2 (ADR2-S: slow ADHII, ADR2-F: fast ADHII) . During growth on 10% glucose, an ADR3c adr2-F/ADR3 ADR2-Sheterozygous diploid formed only the fast ADHII variant wheras an ADR3c ADR2-S/ADR3 ADR2-F heterozygote produced only the slow form . This was taken as evidence of the cis-dominance of all ADR3c alleles . The cis-effect of ADR3c was also demonstrated in glucose-derepressed diploids . The ADR3c mutations do not only cause glucose-insensitive ADHII frmation, but also reduce the activity of the adjacent structural gene during derepression . Thus ADR3c alleles were considered to be controlling site mutations . No pleiotropic effects were observed on the formation of enzymes related to the function of ADHII . An adr1 ADR2 ADR3 single mutant did not form ADHII . In contrast to this, an adr1 ADR2 ADR3c double mutant formed ADHII at a similar level as double mutant formed ADHII at a similar level as an ADR1 ADR2 ADR3c mutant . This showed that ADR3c was epistatic over adr1 (previously suggested as a positive regulatory gene) . From this it was concluded that ADR1 is the fact a positive regulatory gene the function of which is required for the expression of the structural gene for ADHII, ADR2 . ADR3 is the controlling site for the structural gene ADR2 . Mutations at this site, ADR3c, alleviate the requirement for the ADR2 gene product . Adr3c is discussed as a promotor or operator site.

Mol Gen Genet, 1976 Jun 15, 145(3), 287 - 91
Division delay and DNA degradation after mutagen treatment of the yeast, Saccharomyces cerevisiae; Wilmore PJ et al.; The treatment of the yeast mutant TMP1-1, which is capable of incorporating low levels of 3H-thymidine-5' - monophosphate with UV light and ethyl methane sulphonate resulted in division delay when cultures were reinnoculated into fresh medium . The initiation of cell division was accompanied by the degradation of up to 20% of the nuclear DNA fraction . The period of DNA degradation correlates closely with the time at which yeast cultures undergo mitotic recombination and appears to represent the degradation of DNA during a post-replication repair process.

Mol Gen Genet, 1976 Jun 15, 145(3), 259 - 71
Fine structure of the URA2 locus in Saccharomyces cerevisiae . II . Meiotic and mitotic mapping studies; Denis-Duphil M et al.; The URA2 locus codes for a multifunctional enzyme complex carrying aspartate transcarbamylase (ATCase) and carbamyly phosphate synthetase (CPSase) activities . Three different types of ura2 mutants were tested in meiotic and mitotic recombination experiments: ura2A mutants devoid of ATCase activity, ura2C mutants devoid of CPSase activity and ura2B mutants devoid of both activities . All the ura2A mutations were found to be clustered at one end of the URA2 locus, called zone A, while the ura2C mutations were localized in a region at the other end, called zone C . All but two ura2B mutations (most of them suppressible) were distributed throughout zone C; the two ura2B exceptions which are small deletions, mapped in zone A . On the meiotic as well as on the mitotic map an intermediary or dead-space zone is located between zones A and C . No mutation has yet been found to map in this zone . The relative lengths of the three zones A, intermediary and C are 1 :2-3 :3-4, respectively . These data are consistent with the hypothesis that the URA2 locus consisting of at least two cistrons: C (CPSase) and A (ATCase), is transcribed into a single polycistronic message in the direction C to A . However, alternative hypotheses in reference to Peterson and MacLaughlin's observations (1973) are discussed.

J Biol Chem, 1976 Jun 10, 251(11), 3367 - 74
The activating system of chitin synthetase from Saccharomyces cerevisiae . Purification and properties of the activating factor; Ulane RE et al.; The yeast proteinase that causes activation of the chitin synthetase zymogen has been purified by a procedure that includes affinity chromatography on an agarose column to which the proteinaceous inhibitor of the enzyme had been covalently attached . The purified enzyme yielded a single band upon disc gel electrophoresis at pH 4.5 in the presence of urea . At the same pH, but without urea, a faint band was detected in coincidence with enzymatic activity, whereas at pH 9.5, either in the absence or in the presence of sodium dodecyl sulfate, no protein zone could be seen . From sedimentation and gel filtration data, a molecular weight of 44,000 was estimated . The proteinase was active within a wide range of pH values, with an optimum between pH 6.5 AND 7 . Titraton of the activity with the protein inhibitor from yeast required 1 mol of inhibitor/mol of enzyme . A similar result was obtained with phenylmethylsulfonyl fluoride, an indication that 1 serine residue is required for enzymatic activity . The enzyme exhibited hydrolytic activity with several proteins and esterolytic activity with many synthetic substrates, including benzoylarginine ethyl ester and acetyltyrosine ethyl ester.A comparison of the properties of the enzyme with those of known yeast proteinases led to the conclusion that the chitin synthestase activating factor is identical with the enzyme previously designated as proteinase B (EC 3.4.22.9) . This is the first time that a homogeneous preparation of proteinase B has been obtained and characterized.

Biochim Biophys Acta, 1976 Jun 2, 435(1), 21 - 9
A nonspecific inhibitory effect of tRNA on the activity of 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase from Saccharomyces cerevisiae; Bell JB et al.; The inhibitory effect of tRNA on yeast 3-deoxy-D-arabino-heptulosonate-7-phosphate (DAHP) synthase (EC 4.1.2.15) has been reinvestigated . From earlier studies the inhibition by tRNAPhe appeared to be quite specific . This study shows that tRNAPhe is indeed a potent inhibitor but so is unfractionated tRNA, as well as ribosomal RNA and heparin . Complete digestion to mononucleotides relieves the inhibition . Since the enzyme requires a metal ion (Co2+) we suggest that the RNA and heparin are inhibitory by virtue of their capacity to chelate the Co2+.

Proc Natl Acad Sci U S A, 1976 Jun, 73(6), 2072 - 6
Characterization of 2-mum DNA of Saccharomyces cerevisiae by restriction fragment analysis and integration in an Escherichia coli plasmid; Hollenberg CP et al.; Electrophoretic analysis of EcoRI and HindIII restriction fragments of 2-mum supercoiled DNA of Saccharomyces cerevisiae indicated that this class of DNA is heterogeneous and probably consists of two types of molecules . Integration of the 2-mum yeast DNA in E . coli plasmid pCR1 directly showed that existence of two types of molecules as each of these could be individually inserted into separate bacterial plasmids . The difference between the two types of 2-mum circles is due to an inversion of about 1.6 X 10(6) daltons . The inversion is flanked by a reversed duplicated sequence of 0.45 X 10(6) daltons . Possible implications of this structure are dicussed.

Proc Natl Acad Sci U S A, 1976 Jun, 73(6), 2061 - 5
A chromosomal gene required for killer plasmid expression, mating, and spore maturation in Saccharomyces cerevisiae; Leibowitz MJ et al.; "Killer" strains of Saccharomyces cerevisiae are those that harbor a double-stranded RNA plasmid and secrete a toxin that kills only strains not carrying this plasmid (sensitives) . Two chromosomal genes (kex1 and kex2) are required for the secretion of toxin by plasmid-carrying strains . The kex2 gene, which maps at a site distinct from the mating-type locus, is also required for normal mating by alpha strains and meiotic sporulation in all strains . Strains that are alpha mating-type and kex2 fail to secrete the pheromone alpha-factor or to respond to the alpha-factor II pheromone which causes a morphological change, but they do respond to alpha-factor I which causes G1 arrest in alpha cells . Strains that are alpha mating-type and kex2 show no defect in mating; pheromone secretion, or response to alpha-factor . Diploids that are homozygous for the kex2 mutation, unlike wildtype or heterozygous diploids, fail to undergo sporulation, with the defect occurring in the final spore maturation stage . These same defects in the sexual cycle are present in all kex2 mutants independent of the presence of the "killer" plasmid.

J Cell Sci, 1976 Jun, 21(1), 119 - 27
Subcellular localization of diffusible ions in the yeast Saccharomyces cerevisiae: quantitative microprobe analysis of thin freeze-dried sections; Roomans GM et al.; In yeast cells, of which the intracellular potassium had been partly replaced by rubidium or caesium, the intracellular ion distribution was studied by means of energy-dispersive X-ray microanalysis . The cells were rapidly frozen and thin sections were cut at low temperature on a cryo-ultramicrotome without the use of a trough liquid . By this dry cryosectioning procedure, complete retention of the diffusbile ions in the cells was obtained . Unless the sections had been exposed to moisture, no signs of redistribution were apparent . For quantitative determinations a gelatin standard, containing known amounts of the elements of interest, was prepared in the same way as the cells . The concentrations of potassium, rubidium, caesium and chloride in the nucleus, the cytoplasm and the vacuole could be measured . The intracellular distributions of potassium, rubidium and caesium were very similar . The concentrations of these ions in the cytoplasm were about equal to those in the nucleus and twice those in the vacuole . The total concentration in the cytoplasm was 180-190 mmol/kg fresh weight, in the nucleus 190-200 mmol/kg fresh weight and in the vacuole 75-90 mmol/kg fresh weight . The permeability of the yeast cell for chloride is markedly lower than for the cations.

Arch Microbiol, 1976 Jun, 108(2), 211 - 5
Biosynthesis of sulphur amino acids in Saccharomyces cerevisiae II . Analysis of suplhite-producing strains; Romano P et al.; A number of strains of Saccharomyces which produce sulphite by sulphate reduction were examined from an enzymatic and genetic point of view . There are a number of mechanisms that regulate this activity . All of these mechanisms involve the sulphite-reducing activity . In the strains examined, reduced function as a result of mutation in the Sr-locus (affecting H2S-NADP oxidoreductase EC 1.8.1.2), repression of biosynthesis of the enzyme because of a mutation below the specific locus, and inhibition of the enzyme by endogenous factors were found to be responsible . The production of sulphite can also be connected with a complex state of heterozygosity . It is probably this multiplicity of biochemical and genetic mechanisms that accounts for the frequency with which the production of sulphite is observed in wild strains in nature.

Arch Microbiol, 1976 Jun, 108(2), 149 - 52
Promotion of sporulation by caffeine pretreatment in Saccharomyces cerevisiae . II . Changes in ribonuclease activity during sporulation; Tsuboi M et al.; Changes in RNase activity during sporulation of a homothallic diploid strain of Saccharomyces cerevisiae were measured in caffeine-treated and non-treated cells . 1 . In caffeine-treated cells soon after the transfer to the sporulation medium a significant increase in RNase activity was observed; in control cells the rise of RNase activity was less and started after a lag period of 5 h . The final activity of RNase activity was about twice as high in caffeine-treated cells as in control cells . 2 . Increase in RNase activity during sporulation was sensitive to cycloheximide in control cells, but insensitive in caffeine-treated cells . 3 . RNases from vegetative cells and from sporulating ones are different in their Km values . Relation of the changes in RNase activity to premeiotic DNA synthesis is discussed.

Can J Microbiol, 1976 Jun, 22(6), 873 - 83
Characterization of a temperature-sensitive mutant of Saccharomyces cerevisiae that undergoes uncontrolled protein synthesis; Gentile JM et al.; A mutant of Saccharomyces cerevisiae, DW137, isolated after treatment of a wild-type strain with ICR-170 . The mutant was respiration-deficient and showed abnormal cell division when grown at 30 degrees C . In addition, the mutant was temperature-sensitive and underwent lysis when grown at 37 degrees C . Random spore analysis, induced reversion profiles, and complementation analysis indicated that the abnormal phenotypes were under the control of a single recessive mutation caused by a base-pair substitution in a nuclear gene . Macromolecular analysis of the mutant at permissive and restrictive temperatures showed that at restrictive temperatures the mutant cannot synthesize DNA . Surprisingly, at restrictive temperatures, protein synthesis in the mutant continued at a rate greater than that observed at permissive temperatures . Cell death and lysis of the mutant could be prevented by treatment of cultures with cycloheximide, an inhibitor of protein synthesis . The data suggest that the abnormally high rate of protein synthesis and the inability to synthesize DNA are jointly responsible for death of the cells, and most probably play and integrating role in the incipient cell lysis.

Eur J Biochem, 1976 May 17, 65(1), 257 - 62
Isolation and characterization of four related peptides exhibiting alpha factor activity from Saccharomyces cerevisiae; Stotzler D et al.; The molecular structure of alpha factor, a mating hormone produced by alpha mating type cells of Saccharomyces cerevisiae has been investigated . From culture filtrates of alpha cells four oligopeptides exhibiting alpha factor activity have been isolated . These peptides, designated as alpha1, alpha2, alpha3, and alpha4 are structurally closely related, being composed of thirteen (alpha1 and alpha3) and twelve (alpha2 and alpha4) amino acids, respectively . The peptides were found to be composed of the following amino acids: 2 glutamic acid or glutamine, 2 proline, 1 glycine, 1 methionine or methionine sulfoxide, 2 leucine, 1 tyrosine, 1 lysine, 1 histidine, 1 or 2 tryptophan . The tridekapeptides differ from the dodekapeptides by an additional NH2-terminal tryptophan residue . Tyrosine was identified as the C-terminal amino acid in all four peptides . alpha3 and alpha4 are oxidation products containing an internal methionine sulfoxide instead of methionine . The mechanisms which could introduce the observed heterogeneity of the peptides are discussed.

Arch Microbiol, 1976 May 3, 108(1), 27 - 33
Mating reaction in Saccharomyces cerevisiae . IX . Regulation of sexual cell agglutinability of a type cells by a sex factor produced by alpha type cells; Shimoda C et al.; A diffusible sex-specific substance called alpha substance-I (alphaS-I) was isolated from culture filtrate of alpha type strains of the yeast Saccharomyces cerevisiae . The isolated alphaS-I, an oligopeptide, induced sexual cell agglutinability in inducible alpha type strains and enhanced the agglutinability in constitutive a type strains . The induction of sexual agglutinability was detected in 30 min and reached maximum in 90 min, when 0.2 mug/ml of alphaS-I was added to inducible a type cells . The a type-specific factor responsible for sexual cell agglutination, called a type agglutination factor (aAF), was shown to be produced during the induction or the enhancement of agglutinability of a type cells by alphaS-I . The aAF produced in response to alphaS-I was not different in the susceptibility to proteolytic enzymes and disulfide-cleaving agents from those produced constitutively in the absence of alphaS-I.

Z Naturforsch {C}, 1976 May-Jun, 31(5-6), 298 - 303
{Effect of N-methyl-N-beta-chloroethylhydrazine and its benzaldehydhydrazone on RNA-and protein synthesis as well as metabolism of synchronously growing yeast cells (Saccharomyces cerevisiae) (author's transl)}; Braun R et al.; N-methyl-N-beta-chloroethylhydrazine and its benzaldehydhydrazone inhibit the influx of {6-3H}-uracil and L-{U-14C}leucin in yeast cells as well as the incorporation in RNA and protein . Experiments with synchronously and asynchronously growing cells showed the N-methyl-N-beta-chloroethylhydrazine essentially influences the dividing phase while the benzaldehydhydrazone is more effective in the growth phase . The effect of these two substances on respiration, glycolysis and the concentration of fructose-1,6-diphosphate, triose phosphate, and adenosine triphosphate is small.

Z Naturforsch {C}, 1976 May-Jun, 31(5-6), 292 - 7
{Effect of N-methyl-N-beta-chloroethyl-hydrazine-HCl on the growth and multiplication of yeast cells (Saccharomyces cerevisiae) (author's transl)}; Braun R et al.; N-Methyl-N-beta-chloroethyl-hydrazine-HCl and its benzaldehydhydrazone inhibit growth and multiplication of yeast cells . The DNA-synthesis is partially blocked . After removal of the substances the rate of this synthesis is much more increased than that of RNA and protein . The both substances we tested are more effective than simple alkylhydrazines.

Can J Microbiol, 1976 May, 22(5), 762 - 4
Regulation of acetyl-CoA synthetase of Saccharomyces cerevisiae; Coleman JS et al.; Acetyl-coenzyme A synthetase (EC 6.2.1.1) activity of Saccharomyces cerevisiae was determined by a radioactive assay procedure . The activity in vitro was inhibited significantly by NADPH, NADH, or AMP and to a lesser extent by NADP, NAD, or ADP . Glutamic acid and alpha-ketoglutaric acid were not inhibitory . The enzyme level was repressed when the cells were grown in a complex nutrient medium as opposed to the minimal medium . However, a glutamic acid auxotroph glul, when grown in excess glutamic acid, demonstrated a fivefold increase of acetyl-CoA synthetase.

J Bacteriol, 1976 May, 126(2), 661 - 7
Ribonucleic acid synthesized in meiotic cells of Saccharomyces cerevisiae: effect of culture medium pH; Curiale MS et al.; Pulse-labeled ribonucleic acid (RNA) was extracted from polysomes of sporulating cells of Saccharomyces cerevisiae and characterized in sucrose gradients and by sodium dodecyl sulfate-polyacrylamide gel electrophoresis . Transfer RNA, ribosomal RNA, and heterodisperse RNA, presumed to be messenger RNA, were synthesized during a 20-min pulse at T4 and T6 when labeling was performed in sporulation medium adjusted to pH 6.0 . Furthermore, ribosomal RNA was processed into functional ribosomes during the pulse . The specific activity of pulse-labeled RNA of cells labeled in sporulation medium where the pH was unadjusted at T4 (pH 7.8) and T9 (pH 8.6) was 20- to 50-fold lower than RNA from cells labeled at pH 6.0 . The low specific activity resulted from a 50-fold reduction in uptake of labeled precursors when the medium pH was greater than 7.2 . However, heterodisperse RNA ranging from 4-17S in size and transfer RNA were synthesized during the pulse at T4 (pH 7.8),but the low specific activity of ribosomal RNA prevented a thorough analysis of its synthesis . Cellular impermeability at T9 (pH 8.6) resulted in minimal uptake of label, and an analysis of pulse-labeled transcripts was impossible . A comparison of the percantage of polysomal material indicate, however, that these cells were at least as active in translation as cells pulse-labeled at pH 6.0.

Genetics, 1976 Apr, 82(4), 645 - 63
Genetic analysis of petite mutants of Saccharomyces cerevisiae: transmissional types; Perlman PS; We have studied a number of petite {rho-} mutants of Saccharomyces cerevisiae induced in a wild-type strain of mitochondrial genotype {ome- CHL(R) ERY(S) OLI(S) (1, 2, 3) PAR(S)} by Berenil and ethidium bromide, all of which have retained two mitochondrial genetic markers, {CHL(R)} and {ERY(S)}, but have lost all other known markers . Though stable in their ability to retain these markers in their genome, these mutants vary widely among themselves in suppressiveness and in the extent to which the markers are transmitted on crossing to a common wild-type tested strain . In appropriate crosses all of the strains examined in this study demonstrate mitochondrial polarity, and thus have also retained the {ome-} locus in a functional form; however, five different transmissional types were obtained, several of them quite unusual, particularly among the strains originally induced by Berenil . One of the most interesting types is the one that appears to reverse the parental genotypes with {CHL(R) ERY(S)} predominating over {CHL(S) ERY(R)} in the diploid {rho+} progeny, rather than the reverse, which is characteristic of analogous crosses with {rho+} or other petites . Mutants in this class also exhibited low or no suppressiveness . Since all of the petites reported here are derived from the same wild-type parent, and so have the same nuclear background, we have interpreted the transmissional differences as being due to different intramolecular arrangements of largely common retained sequences.

Genetics, 1976 Apr, 82(4), 639 - 44
Mutants of Saccharomyces cerevisiae resistant to the alpha mating-type factor; Manney TR et al.; Mutants that are resistant to alpha-factor have been isolated from a mating-type haploid strains of yeast by direct selection on agar medium containing partially purified alpha-factor . All resistant mutants isolated were found to be sterile . They were characterized and compared with mutants previously isolated as non-mating . Among 93 able to mate at low frequency and to sporulate, none showed linkage to the mating-type locus . The results support the hypothesis that the response to alpha-factor by cells of mating-type a is essential for mating.

Biotechnol Bioeng, 1976 Apr, 18(4), 449 - 63
Influence of salts and gelatin on disintegration of Saccharomyces cerevisiae by freeze-pressing; Magnusson KE et al.; The disintegration by freeze-pressing of a low concentration of Saccharomyces cerevisiae suspended in aqueous solutions of gelatin and different salts has been studied at different temperatures . In the freeze-pressing process deionized water and salt solutions flow in pulses, whereas samples with increasing concentrations of gelatin or cells tend to flow more smoothly . This smooth flow enhances the disruption efficiency particularly at lower temperatures, which seems to be of great practical importance . The addition of salts also promotes disintegration . The presence of both gelatin and salts works antagonistically on disintegration presumably because of different modes of action at disruption of cells.

J Bacteriol, 1976 Apr, 126(1), 243 - 50
Control of inositol biosynthesis in Saccharomyces cerevisiae; inositol-phosphate synthetase mutants; Culbertson MR et al.; Inositol-requiring mutants of Saacharomyces cerevisiae were tested in cell extracts for the ability to convert glucose-6-phosphate to inositol-phosphate (IP synthetase) and inositol (IP phosphatase) . Mutants representing any one of 10 unlinked loci conferring the inositol requirement were unable to synthesize either compound in an assay with glucose-6-phosphate as the substrate . These results indicate that the mutants lack IP synthetase activity and that at least 10 genes control the conversion of glucose-6-phosphate to inositol-phosphate . In addition, a mutation known to be unlinked with the ino1 locus interacts with a leaky ino1 allele and may play a role in the regulation of IP synthetase . This mutation causes a 47% reduction in wild-type IP synthetase activity and, when combined in a haploid strain with the leaky ino1 allele, it reduced IP synthetase activity to a level below that which is growth supporting . Wild-type and IP synthetase-deficient strains were tested for reduced nicotinamide adenine dinucleotide (NADH) accumulation, since NAD+ is required in the conversion of glucose-6-phosphate to inositol . No detectable accumulation of NADH was observed in the wild-type strain, presumably because the NADH generated is rapidly oxidized during subsequent partial reactions of IP synthetase . Mutants representing three different loci accumulate NADH and may, therefore, lack the NADH-mediated reductase activity of IP synthetase . Other mutants tested fail to accumulate NADH and may, therefore, lack the NAD+-mediated oxidase activity of IP synthetase . Phospholipid synthesis was studied by 32P pulse labeling in one mutant under conditions of inositol supplementation and starvation . Starved cells incorporate 32P into phospholipids normally for 2 h, followed by a period in which the rate of phosphatidylinositol synthesis decreases and the rate of phosphatidylcholine synthesis increases . After 5 to 6 h starvation, all cellular phospholipid synthesis ceases.

J Bioenerg, 1976 Apr, 8(2), 93 - 107
Genetic analysis of mitochondrial biogenesis and function in Saccharomyces cerevisiae; Michaelis G et al.; Different mitochondrial mutants have been isolated that affect mitochondrial ribosome function . These mutants were used to establish most of the known methods and principles of mitochondrial genetics in yeast . Another class of mitochondrial mutants have been shown to affect mitochondrial ATPase and, more specifically, the "membrane factor" of mitochondrial ATPase . These mutants might be very useful in studying the energy-conserving function, and the interaction between the hydrophobic and hydrophylic parts, of the ATPase complex . New types of mitochondrial point mutations, concerning cytochrome a-a3 or b, will soon open up new fields of investigation . The biochemical and genetic analysis of numerous mutants belonging to that category and recently obtained {31} is being currently pursued in Tzagoloff's and Slonimski's laboratories.

Mol Gen Genet, 1976 Mar 30, 144(3), 301 - 6
Macromolecule synthesis in a mutant of Saccharomyces cerevisiae inhibited by S-adenosyimethionine; Lipinski C et al.; Saccharomyces cerevisiae strain 83384-B3 carries the sai-1 mutation which confers sensitivity to S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) . It was shown that the mutant is impermeable to precursors of ribonucleic acid (RNA) and protein during inhibition by SAM (0.2 mM) . Inhibition of uptake of adenine and uracil was nearly complete 3 h after growth in the presence of SAM and the uptake of leucine was at least 10-fold lower . The incorporation of 3H-adenine into ribosomal RNA, transfer RNA and heterodisperse RNA, believed to be messenger, was reduced 10-fold when measured after 1 h inhibition . The inhibition of growth was completely reversed by methionine (2.0 mM) in cells previously exposed to SAM for 90 min . The polysome content in cells inhibited by SAM was 25% less than the control after 4 h inhibition . Ribosome synthesis increased only about 40% in the presence of SAM and about 5-fold in the control over an 8 h period . All classes of RNA were synthesized during inhibition.

Mol Gen Genet, 1976 Mar 30, 144(3), 289 - 99
Cytoplasmic inheritance in Saccharomyces cerevisiae: comparison of zygotic mitochondrial inheritance patterns; Aufderheide KJ et al.; Mitochondrial movements in Saccharomyces cerevisiae (Sc) zygotes were monitored with phase-contrast microscopy and compared to known mitochondrial inheritance systems . The mitochondria of Sc were convincingly identified by integrated use of phase-contrast, cytochemical and electron microscopic observations . Mitochondria in Sc appear to move by saltatory jumps, which appear to be oriented towards movement of mitochondria into developing buds . Tracking of mitochondria of different genotypes was made possible by positive identification of each mitochondrial population before zygosis, and by the low degree of mixing (less than 10%) of mitochondrial populations before first bud septation . A grande by grande cross demonstrated equal numbers of mitochondria from each haploid moving into the first zygotic bud . A grande by neutral petite cross gave a 2:1 ratio of grande to petite mitochondria . However, a grande by suppressive petite cross gave equal numbers of grande and petite mitochondria . Using drug resistance systems, a comparison was made of highly biased (97%) and moderately biased (71%) chloramphenicol resistant inheritance patterns . In both cases, the ratios of drug resistant to sensitive mitochondria were 1:1 . When numbers of mitochondria moving into an individual bud were compared to the phenotypic content of the clone of that bud, no model could be constructed which could predict the latter from the former . The data indicate (with the exception of the neutral petite by grande cross) that the numbers of each mitochondrial type "inserted" into the first zygotic bud are equal, regardless of the degree of asymmetry of inheritance of mitochondrial markers.

Mol Gen Genet, 1976 Mar 30, 144(3), 281 - 8
Some physiological alteration associated with pleiotropic cross resistance and collateral sensitivity in Saccharomyces cerevisiae; Rank GH et al.; A mutant strain (2-20) isolated by growth on medium containing oligomycin and cycloheximide was also found to be cross resistant to antimyicn, cerulenin, chloramphenicol, tetracycline, triethyltin and triphenylmethylphosphonium bromide, but collaterally sensitive to dequalinium chloride, gentamycin, neomycin, paromomycin and thiolutin . Growth of 2-20, compared to the parental strain and 2 complete revertants, under a variety of environmental conditions revealed that strain 2-20 had an enhanced sensitivity to increased osmolality, elevated pH, and high temperature; in addition, strain 2-20 was unable to polymerize aminoimidazole ribotide at 37 degrees C as shown by the failure to develop a red colony in the presence of ade 2 . Four complex solid media (glucose--KCI, galactose, ethanol, ethanol--KCI, Table 1) unable to sustain the growth of strain 2-20 were arbitrarily chosen to monitor cellular growth under different physiological conditions . Tetrad analysis indicated that the complex phenotype (cross resistance, collateral sensitivity, inablity to polymerize aminoimidazole ribotide, absence of growth under adverse physiological conditions) was inherited by an allele of a locus previously shown to result in a permeability barrier of the plasma membrane to chloramphenicol . 582 of 640 subclones used to isolate revertants of 2-20, under four different physiological conditions, were observed to produce a complete revertant of the complex phenotype . It is proposed that the pleiotropic phenotype could result from an alteration of the plasma membrane and mitochondrial inner membrane by a single nuclear gene mutation.

Genetics, 1976 Mar 25, 82(3), 429 - 42
Two chromosomal genes required for killing expression in killer strains of Saccharomyces cerevisiae; Wickner RB et al.; The killer character of yeast is determined by a 1.4 X 10(6) molecular weight double-stranded RNA plasmid and at least 12 chromosomal genes . Wild-type strains of yeast that carry this plasmid (killers) secret a toxin which is lethal only to strains not carrying this plasmid (sensitives).--We have isolated 28 independent recessive chromosomal mutants of a killer strain that have lost the ability to secrete an active toxin but remain resistant to the effects of the toxin and continue to carry the complete cytoplasmic killer genome . These mutants define two complementation groups, kex1 and kex2 . Kex1 is located on chromosome VII between ade5 and lys5 . Kex2 is located on chromosome XIV, but it does not show meiotic linkage to any gene previously located on this chromosome.--When the killer plasmid of kex1 or kex2 strains is eliminated by curing with heat or cycloheximide, the strains become sensitive to killing . The mutant phenotype reappears among the meiotic segregants in a cross with a normal killer . Thus, the kex phenotype does not require an alteration of the killer plasmid.--Kex1 and kex2 strains each contain near-normal levels of the 1.4 x 10(6) molecular weight double-stranded RNA, whose presence is correlated with the presence of the killer genome.

Biochim Biophys Acta, 1976 Mar 25, 428(1), 182 - 92
A gene controlling the synthesis of non specific alkaline phosphatase in Saccharomyces cerevisiae; Toh-E A et al.; Recessive mutants defective in the formation of non-specific alkaline phosphatase (EC 3.1.3.1) could be selected by staining colonies on a plate with p-nitrophenylphosphate after treatment with chloroform vapour . Since no complementation was observed among the nine mutants so far tested, all the mutations might occur in the same locus, phoH . The non-specific alkaline phosphatase was repressible, although a significant basal level of the enzyme activity was observed in the repressed condition.

J Biol Chem, 1976 Mar 25, 251(6), 1799 - 807
The ribosomal proteins of Saccharomyces cerevisiae . Phosphorylated and exchangeable proteins; Zinker S et al.; Sixty-seven ribosomal proteins of the yeast Saccharomyces cerevisiae have been distinguished by two-dimensional polyacrylamide gel electrophoresis . Five of the ribosomal proteins are phosphorylated in vivo . One of the phosphorylated proteins appears to correspond to the phosphorylated ribosomal protein, S6, of rat liver . Another of the yeast-phosphorylated proteins, which is highly acidic, may be related to the protein L7/L12 of Escherichia coli . The phosphorylation of four of the five ribosomal proteins depends on protein synthesis . Ribosome synthesis, however, is not necessary for the phosphorylation of any of them . Three proteins of the 60 S ribosomal subunit are "exchangeable" in vivo . Two of these are phosphoproteins, one of which is the very acidic protein possibly related to L7/L12 of E . coli . The possible significance of this phosphorylated, exchangeable protein in protein synthesis is discussed.

Mol Gen Genet, 1976 Mar 22, 144(2), 213 - 5
Mutational properties of supP amber-ochre supersuppressors in Saccharomyces cerevisiae; Gerlach WL; Mutational properties of the supP amber-ochre supersuppressor locus in Saccharomyces cerevisiae are described . They are consistent with the proposition that the supP locus encodes a protein.

Mol Gen Genet, 1976 Mar 22, 144(2), 131 - 40
The effect of dose and time on the induction of genetic alterations in Saccharomyces cerevisiae by aminoacridines in the presence and absence of visible light irradiation in comparison with the dose-effect-curves of mutagens with other type of action; Fahrig R; Aminoacridines induce frameshift mutations and are photodynamically active, depending on whether visible light is absent or present . Therefore, a test system which allows to compare quantitatively the genetic effects of aminoacridines irradiated or unirradiated by visible light ought to be susceptible to the different DNA alterations which can be induced by these substances . For this reason in most experiments mitotic gene conversion and only in some selected experiments reverse mutation was chosen as the indicator of genetic activity . In contrast to mutation systems mitotic gene conversion has never shown a response specific to only some types of mutagens . The three aminoacridine derivatives used-acridine orange (AO), proflavine (PF), and acridine yellow (AY)-were successful in the induction of convertants at two different loci . No locus-specificity could be observed . The time-dependent induction of convertants proceeds quickly but soon reaches-especially after treatment without light-a saturation point . The dose/effect-curve after treatment in the dark has a slope increasing with increasing concentration . Irradiation with visible light results in a dose/effect-curve consisting of three parts . Af first the increase of convertants is nearly linear extending one (AY) to three (AO) orders of magnitude . After a saturation effect begins at the point at which an effectiveness of the acridines in the dark is apparent . At high concentrations an induction of convertants can again be observed which is nearly the same as that after treatment in the dark . To determine whether the dose/effect-curves obtained for gene conversion refer to similar curves for gene mutations after treatment with AO at the same locus not only gene conversions but also reverse mutations were scored for . AO-treatment in the dark is ineffective in inducing reverse mutations . Irradiation with visible light results in a dose/effect-curve beeing parallel only in its first part to the dose/effect-curve obtained for gene conversion, while in its second part a mutation frequency decline can be observed . Comparing the dose/effect-curves of AO resulting from the induction of gene conversion and gene mutation, and taking into account that no mutants can be induced by AO-treatment in the dark, the increase in convertants at high acridine-concentrations can be explained as an addition of light-dependent and light-independent effects . That means, in mutation systems at low concentrations of aminoacridines irradiation with visible light should cause transitions, transversions and microlesions, at intermediate concentrations frameshift lesions should begin to appear, and at very high concentrations nearly exclusively frameshift lesions should occur . The dose/effect-curves of aminoacridines compared with those of other mutagens are very complex . The dose/effect-curves of the mutagens of other type of action tested are linear in a double logarithmic scale, and parallel for induced gene conversion and induced gene mutation...

Arch Microbiol, 1976 Mar 19, 107(2), 207 - 14
Free tryptophan pool and tryptophan biosynthetic enzymes in Saccharomyces cerevisiae; Fantes PA et al.; The free tryptophan pool and the levels of two enzymes of tryptophan biosynthesis (anthranilate synthase and indoleglycerolphosphate synthase)have been determined in a wild type strain of Saccharomyces cerevisiae and in mutants with altered regulatory properties.

C R Acad Sci Hebd Seances Acad Sci D, 1976 Mar 15, 282(11), 1141 - 3
{Genetic effects of the gaseous phase of cigarette smoke on Saccharomyces cerevisiae}; Izard C et al.; The gaseous phase of cigarette smoke is active on Saccharomyces cerevisiae . A toxic effect and several genetic alterations were observed . Mitotic segregants are induced and the cytoplasmic "petite" mutation is selected and induced . These effects vary according to the growth phase of the culture and to the brand of cigarettes tested . Stationary phase cells are more resistant than exponentially growing ones.

Biochem J, 1976 Mar 15, 154(3), 751 - 63
Distribution of membranes, especially of plasma-membrane fragments, during zonal centrifugations of homogenates from glucose-repressed Saccharomyces Cerevisiae; Nurminen T et al.; 1 . The distributions of several enzymes and other marker components were examined after zonal centrifugations of whole homogenates from glucose-repressed Saccharomyces cerevisiae on sucrose and iso-osmotic Ficoll, and the composition and morphology of the fractions were investigated . 2 . After high-speed zonal centrifugation most of the protein, acid and alkaline phosphatases, alkaline pyrophosphatase, adenosine monophosphatase, beta-fructofuranosidase, alpha-mannosidase, NADPH-cytochrome c oxidoreductase and an appreciable amount of phospholipid and sterol were non-sedimentable, i.e . were at densities below 1.09 (g/cm3) . Most of the RNA was at p=1.06-1.08 in Ficoll and at p=1.09-1.11 in sucrose . 3 . The bulk of the Mg2+-dependent adenosine triphosphatase (Mg-ATPase) was coincident with the main peak of phospholipid and sterol, at median density 1.10, which was also rich in smooth-membrane vesicles . In Ficoll, a minor peak of phospholipid and sterol at p-1.12-1.15 contained a smaller part of the oligomycin-insensitive Mg-ATPase and heavy membrane fragments . In sucrose, several minor peaks of Mg-ATPase were in the mitochondrial density range, and a peak of oligomycin-insensitive Mg-ATPase coincident with a minor peak of phospholipid and sterol at around p-1.25 contained heavy membrane fragments of high carbohydrate content, especially mannose . 4 . Further purification of the oligomycin-insensitive Mg-ATPase containing membrane preparations was performed on Urografin gradients . 5 . It is argued that the oligomycin-insensitive Mg-ATPase containing membranes are fragments of the plasma membrane, but have different densities because they contain different amounts of glycoprotein particles.

J Bacteriol, 1976 Mar, 125(3), 999 - 1004
Utilization of D-asparagine by Saccharomyces cerevisiae; Dunlop PC et al.; Yeast strains sigma1278b and Harden and Young, which synthesize only an internal constitutive form of L-asparaginase, do not grow on D-asparagine, as a sole source of nitrogen, and whole cell suspensions of these strains do not hydrolyze D-asparagine . Strains X2180-A2 and D273-10B, which possess an externally active form of asparaginase, are able to grow slowly on D-asparagine, and nitrogen-starved suspensions of these strains exhibit high activity toward the D-isomer . Nitrogen starvation of strain X218O-A2 results in coordinate increase of D- and L-asparaginase activity; the specific activity observed for the D-isomer is approximately 20% greater than that observed for the L-isomer . It was observed, in studies with cell extracts, that hydrolysis of D-asparagine occurred only with extracts from nitrogen-starved cells of strains that synthesize the external form of asparaginase . Furthermore, the activity of the extracts toward the D-isomer was always higher than that observed with the L-isomer . A 400-fold purified preparation of external asparaginase from Saccharomyces cerevisiae X218U-A2 hydrolyzed D-asparagine with an apparent Km of 0.23 mM and a Vmax of 38.7 mumol/min per mg of protein . D-Asparagine was a competitive inhibitor of L-asparagine hydrolysis and the Ki determined for this inhibition was approximately equal to its Km . These data suggest that D-asparagine is a good substrate for the external yeast asparaginase but is a poor substrate for the internal enzyme.

J Bacteriol, 1976 Mar, 125(3), 887 - 91
Kinetics of labeling of the S-adenosylmethionine pool of Saccharomyces cerevisiae; Warner JR et al.; A method has been developed for studying the specific activity of the pool of S-adenosylmethionine in yeast . The pool reaches half-maximal specific activity within 30 s after the addition of {methyl-3H}methionine . After addition of an excess of nonradioactive methionine, the specific activity of S-adenosylmethionine is reduced by half within 20 s . During that period there is a substantial expansion of the pool . A logarithmically growing cell in synthetic medium contains about 2 X 10(6) molecules of S-adenosylmethionine, of which only 10% is used for the methylation of ribonucleic acid molecules.

J Bacteriol, 1976 Mar, 125(3), 864 - 71
Regulation of lysine transport by feedback inhibition in Saccharomyces cerevisiae; Morrison CE et al.; A steady-state level of about 240 nmol/mg (dry wt) occurs during lysine transport in Saccharomyces cerevisiae . No subsequent efflux of the accumulated amino acid was detected . Two transport systems mediate lysine transport, a high-affinity, lysine-specific system and an arginine-lysine system for which lysine exhibits a lower affinity . Preloading with lysine, arginine, glutamic acid, or aspartic acid inhibited lysine transport activity; preloading with glutamine, glycine, methionine, phenylalanine, or valine had little effect; however, preloading with histidine stimulated lysine transport activity . These preloading effects correlated with fluctuations in the intracellular lysine and/or arginine pool: lysine transport activity was inhibited when increases in the lysine and/or arginine pool occurred and was stimulated when decreases in the lysine and/or arginine pool occurred . After addition of lysine to a growing culture, lysine transport activity was inhibited more than threefold in one-third of the doubling time of the culture . These results indicate that the lysine-specific and arginine-lysine transport systems are regulated by feedback inhibition that may be mediated by intracellular lysine and arginine.

J Bacteriol, 1976 Mar, 125(3), 1048 - 56
Urea transport-defective strains of Saccharomyces cerevisiae; Sumrada R et al.; Experiments characterizing the urea active transport system in Saccharomyces cerevisiae indicate that (i) formamide and acetamide are strong competitive inhibitors of urea accumulation, (ii) uptake is maximal at pH 3.3 and is 80% inhibited at pH 6.0, and (iii) adenosine 5'-triphosphate generated by glycolysis in conjunction with formation of an ion gradient is likely the driving force behind urea transport . Mutant strains were isolated that are unable to accumulate urea at external concentrations of 0.25 mM . These strains also exhibit a depressed growth rate on 10 mM urea, indicating existence of a relationship between the active transport and facilitated diffusion modes of urea uptake.

J Bacteriol, 1976 Feb, 125(2), 595 - 600
Turnover of polyadenylate-containing ribonucleic acid in Saccharomyces cerevisiae; Hynes NE et al.; We examined the kinetics of incorporation of {3H}adenine into polyadenylate-containing ribonucleic acid {poly(A)-containing RNA} in yeast . The total poly(A)-containing RNA from spheroplasts and intact cells and the polysomal poly(A)-containing RNA exhibited similar incorporation kinetics . At 30 C half-saturation of the pool of poly(A)-containing RNA with label occurred in approximately 22 min . Since precursor pools appeared to require 5 min to saturate with label, we conclude that at 30 C messenger RNA molecules in yeast decay with an average half-life of 17 min.

Genetics, 1976 Feb, 82(2), 273 - 85
Mutants of the killer plasmid of Saccharomyces cerevisiae dependent on chromosomal diploidy for expression and maintenance; Wickner RB; Mutants of the killer plasmid of Saccharomyces cerevisiae have been isolated that depend upon chromosomal diploidy for the expression of plasmid functions and for replication or maintenance of the plasmid itself . These mutants are not defective in any chromosomal gene needed for expression or replication of the killer plasmid.--Haploids carrying these mutant plasmids (called d for diploid-depen;ent) are either unable to kill or unable to resist being killed or both and show frequent loss of the plasmid . The wild-type phenotype (K+R+) is restored by mating the d plasmid-carrying strain with either (a) a wild-type sensitive strain which apparently has no killer plasmid; (b) a strain which has been cured of the killer plasmid by growth at elevated temperature; (c) a strain which has been cured of the plasmid by growth in the presence of cycloheximide; (d) a strain which has lost the plasmid because it carries a mutation in a chromosomal mak gene; or (e) a strain of the opposite mating type which carries the same d plasmid and has the same defective phenotype, indicating that the restoration of the normal phenotype is not due to recombination between plasmid genomes or complementation of plasmid or chromosomal genes.--Sporulation of the phenotypically K+R+ diploids formed in matings between d and wild-type nonkiller strains yields tetrads, all four of whose haploid spores are defective for killing or resistance or maintenance of the plasmid or a combination of these . Every defective phenotype may be found among the segregants of a single diploid clone carrying a d plasmid . These defective segregants resume the normal killer phenotype in the diploids formed when a second round of mating is performed, and the segregants from a second round of meiosis and sporulation are again defective.

Nucleic Acids Res, 1976 Feb, 3(2), 465 - 76
Comparison of the fine structure of mitochondrial DNA from Saccharomyces cerevisiae and S . carlsbergensis: electron microscopy of partially denatured molecules; Christiansen G et al.; Denaturation-maps of mitochondrial DNA from Saccharomyces cerevisiae and S . carlsbergensis have been derived from electron microscopic observations of partially denatured complete circular molecules and large fragments of these circles . The mitochondrial DNA from the two species differ by 6% in total length, but seems from the maps to contain some regions of apparent close homology . The cleavage pattern of the two DNAs by the restriction endonuclease EcoRI is compared by gel electrophoresis.

J Virol, 1976 Feb, 17(2), 472 - 6
Virus-like particles from killer, neutral, and sensitive strains of Saccharomyces cerevisiae; Adler J et al.; Procedures were developed for purification of virus-like particles (VLPs) from killer, neutral, and sensitive strains of Saccharomyces cerevisiae . Morphologically similar spherical VLPs measuring 40 nm in diameter were extracted from all three phenotypes . The particles were partially purified by high-speed centrifugation through a layer of CsCl (1.26 g/cm3) and sucrose density gradient centrifugation . Gradient-purified preparations contained three centrifugal species that sedimented at approximately 43, 102, and 162S . The 43S component is considered to be an artifact . Preparations from killer strains contained three double-stranded RNA (ds-RNA) components with molecular weights of 1.19 x 10(6), 1.29 x 10(6) and 2.54 x 10(6) . VLPs from neutral and sensitive strains contained only the largest ds-RNA species . VLP preparations were subsequently separated into two major density components by CsCl equilibrium gradient centrifugation . The light component banding at 1.28 to 1.30 g/cm3 was void of nucleic acid, and the heavy component banding at 1.40 g/cm3 contained only the largest ds-RNA species.

Mutat Res, 1976 Feb, 34(2), 201 - 16
Induction of mitotic recombination with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in Saccharomyces cerevisiae . A comparison between treatment in vitro and in the host-mediated assay; Ryttman H et al.; Two methods, treatment in vitro and the host-mediated assay method, were compared in their ability to demonstrate the induction of MNNG of nitotic recombination in a diploid strain of Saccharomyces cerevisiae . MNNG had a strong activity in vitro but not in the host-mediated assay at the concentrations tested . When the genetic effects of MNNG have been tested in different test systems, sometimes negative, sometimes positive results have been obtained . The relevance of different tests for risk evaluation is discussed, and it is concluded from the data on MNNG that tests on whole mammals may sometimes give false negative results because the cells tested are, in parts of the body, less accessible to the mutagen . Increasing doses of MNNG by treatment in vitro gave decreasing frequencies of mitotic recombination, indicating damage to the recombinational system in the cells . Dose-response relationships for recombination and mutation are discussed.

Arch Microbiol, 1976 Feb, 107(1), 63 - 70
The intramitochondrial location of cytochrome c peroxidase in wild-type and petite Saccharomyces cerevisiae; Williams PG et al.; Cytochemical and ultrastructural analysis of wild-type cells of Saccharomyces cerevisiae, grown aerobically in a glucose-limited chemostat, shows that cytochrome c peroxidase is localized between the membranes of the cristae, that is, in the intracristal space . This enzyme is thus positioned appropriately within the organelle to act as an alternate terminal oxidase for the respiratory chain . The proximity of the peroxidase to major sites of generation of its two substrates may account for the small leakage of hydrogen peroxide from yeast mitochondria, as compared with the larger outflow from mammalian mitochondria . In the cytoplasmic petite mutant, gross distortion of promitochondrial membrane arrangement is evident . Nevertheless, cytochrome c perioxidase activity is present in the same amounts as is found in wild-type cells, and is localized predominantly within annuli of membrane which constitute the promitochondria in these cells . No unequivocal evidence was obtained for the localization of catalase in microbodies or other organelles in either wild-type or petite cells.

Mol Gen Genet, 1976 Jan 16, 143(2), 131 - 65
Mitochondrial genetics . XI . Mutations at the mitochondrial locus omega affecting the recombination of mitochondrial genes in Saccharomyces cerevisiae; Dujon B et al.; 1 . A series of CS revertants has been selected from various strains (both omega+ and omega-) carrying a CR mitochondrial mutation at the RIB1 locus . The properties of mitochondrial recombination exhibited by these CS revertants in various crosses, have been examined systematically . The omega allele of the CS revertants has been defined in crosses with omega+ and omega- tester strains using two criteria: the polarity of recombination and a new criterium called relative output coefficient . We found that mutations of omega appear frequently associated with the mutations at the RIB1 locus selected from omega- strains but not with those selected from omega+ strains . A new allelic form of omega (omega n) which had not been found amongst wild type yeast strains is characterised . Similarly omega n mutation was found frequently associated with CR mutants at the RIB1 locus selected from omega- CS strains but not with those selected from omega+ CS strains . The omega n mutants, and the omega+ and omega- strains, explain the groups of polarity previously observed by Coen et al . (1970) . 2 . Main features of mitochondrial crosses with omega n strains (omega+ x omega n, omega- x omega n and omega n x omega n) are analysed . Recombination is possible between the different mitochondrial genetic markers . No high polarity of recombination is observed and the frequency of recombinants are similar to those found in homosexual crosses (omega+ x omega+ and omega- x omega-) . A striking property, observed for the first time, exists in crosses between zota+ omega n CS strains and some zota- CREO mutants: the zota- CREO are unable to integrate by recombination their CR allele into the zota+ mit-DNA of omega n CS strains while being capable of integrating it into omega+ CS or omega- CS genomes . 3 . It is proposed that the omega locus is the site of initiation of non reciprocal recombination events, the omega+/omega- pairing specifically initiates the non-reciprocal act while omega+/omega n or omega-/omega n pairings do not . 4 . The molecular nature of the omega n mutation and its bearing on the structure of the omega locus are discussed . It is suggested that omega n mutations correspond to macrolesions (probably deletions) of a segment of the mit-DNA covering the omega and RIB1 loci . If omega n is a partial deletions of the omega- sequence the omega+ could be an additionnal deletion of the omega n sequence . 5 . The occurrence of spontaneous CR and ER mitochondrial mutations has been analysed by the Luria and Delbruck fluctuation test in omega- and omega n isonuclear strains . Results of these tests indicate that an intracellular selection of resistant copies preexisting the action of the anttibiotic occurs.

Mol Gen Genet, 1976 Jan 16, 143(2), 119 - 29
The repair of double-strand breaks in the nuclear DNA of Saccharomyces cerevisiae and its genetic control; Resnick MA et al.; With the use of neutral sucrose sedimentation techniques, the size of unirradiated nuclear DNA and the repair of double-strand breaks induced in it by ionizing radiation have been determined in both wild-type and homozygous rad52 diploids of the yeast Saccharomyces cerevisiae . The number average molecular weight of unirradiated DNA in these experiments is 3.0 X 10(8)+/-0.3 Daltons . Double-strand breaks are induced with a frequency of 0.58 X 10(-10) per Daltonkrad in the range of 25 to 100 krad . Since repair at low doses is observed in wild-type but not homozygous rad52 strains, the corresponding rad52 gene product is concluded to have a role in the repair process . Cycloheximide was also observed to inhibit repair to a limited extent indicating a requirement for protein synthesis . Based on the sensitivity of various mutants and the induction frequency of double-strand breaks, it is concluded that there are 1 to 2 double-strand breaks per lethal event in diploid cells incapable of repairing these breaks.

C R Acad Sci Hebd Seances Acad Sci D, 1976 Jan 12, 282(2), 227 - 30
{Biosynthesis of long chain fatty acids and alkanes in Saccharomyces cerevisiae}; Blanchardie P et al.; Cell-free extracts of Saccharomyces cerevisiae catalyse the formation of very long chain fatty acids with an even number of carbon atoms . These acids may be alpha-oxidated leadint to odd-chain acids . Both even and odd chain acids may be subjected to reductive decarboxylation giving rise to alkanes with respectively odd or even aliphatic chains.

J Biol Chem, 1976 Jan 10, 251(1), 124 - 8
A revised preparation of yeast (Saccharomyces cerevisiae) pyruvate kinase; Yun SL et al.; A revised preparation of pyruvate kinase from saccharomyces cerevisiae is reported . By purifying this cold-labile enzyme at room temperature, an improved recovery and specific activity was obtained . More than 350 mg of pure enzyme with a specific activity of 350 to 400 units/mg at 30 degrees were obtained from a pound of fresh yeast . The last step of the preparation, passage of the enzyme over Sephadex G-100, was required to remove a contaminating protease . The molecular parameters of the new preparation are: molecular weight, 209,000; four subunits of identical size; E 280 nm, 0.51; pI 6.6; and pH optimum, 6.28 . Kinetic parameters are: Km for P-enolpyruvate and ADP, 0.09 and 0.18 mM in the presence of saturating Fru-1,6-P2, and 1.8 and 0.34 mM in the absence of Fru-1,6-P2; Ka for Fru-1,6-P2, 0.014 mM . No free NH2-terminal amino acid could be detected . Amino acid composition was determined and compared with other pyruvate kinase preparations.

J Gen Microbiol, 1976 Jan, 92(1), 207 - 220
On the nature and formation of the fibrillar nets produced by protoplasts of Saccharomyces cerevisiae in liquid media: an electronmicroscopic, x-ray diffraction and chemical study; Kreger DR et al.; The nets produced by protoplasts of Saccharomyces cerevisiae in liquid culture media consisted of microfibrils about 20 nm wide, forming flat, fairly straight bundles of variable width and length, up to about 500 nm wide and 4 mum long . Ends of microfibrils were seldom found . They were not attacked by chitinase or dilute acids, but the net structure disappeared in 3% (w/v) NaOH, leaving about 60% dry wt of the nets as partly microfibrillar clusters . The X-ray powder pattern from the nets, in contrast to that from normal walls, exhibited a set of well-defined rings which identified two micro-crystalline constituents: chitin and unbranched chains of beta-(I leads to 3)-linked D-glucose residues . These latter were the alkali-soluble fraction . The X-ray diagram of the glucan, corresponding to that of paramylon, indicated an in vivo crystal modification . Up to 15% dry wt was chitin which was formed de novo by the protoplasts . A fine net structure of microfibrils about 7-5 to 10 nm thick with meshes about 20 to 60 nm wide was demonstrated in normal walls, forming the entire inner layer and consisting mainly of yeast glucan . This glucan and chitin were only slightly crystalline in these walls . The features of the glucan and chitin of the protoplast nets indicate that enzymes active in normal wall formation were differentially removed or inactivated by the liquid medium.

J Gen Microbiol, 1976 Jan, 92(1), 207 - 20
On the nature and formation of the fibrillar nets produced by protoplasts of Saccharomyces cerevisiae in liquid media: an electronmicroscopic, X-ray diffraction and chemical study; Kreger DR et al.; The nets produced by protoplasts of Saccharomyces cerevisiae in liquid culture media consisted of microfibrils about 20 nm wide, forming flat, fairly straight bundles of variable width and length, up to about 500 nm wide and 4 mum long . Ends of microfibrils were seldom found . They were not attacked by chitinase or dilute acids, but the net structure disappeared in 3% (w/v) NaOH, leaving about 60% dry wt of the nets as partly microfibrillar clusters . The X-ray powder pattern from the nets, in contrast to that from normal walls, exhibited a set of well-defined rings which identified two micro-crystalline constituents: chitin and unbranched chains of beta-(1 leads to 3)-linked D-glucose residues . These latter were the alkali-soluble fraction . The X-ray diagram of the glucan, corresponding to that of paramylon, indicated an in vivo crystal modification . Up to 15% dry wt was chitin which was found de novo by the protoplasts . A fine net structure of microfibrils about 7-5 to 10 nm thick with meshes about 20 to 60 nm wide was demonstrated in normal walls, forming the entire inner layer and consisting mainly of yeast glucan . This glucan and chitin were only slightly crystalline in these walls . The features of the glucan and chitin of the protoplast nets indicate that enzymes active in normal wall formation were differentially removed or inactivated by the liquid medium.

J Bacteriol, 1976 Jan, 125(1), 25 - 32
Thermosensitive mutations affecting ribonucleic acid polymerases in Saccharomyces cerevisiae; Thonart P et al.; Among 150 temperature-sensitive Saccharomyces cerevisiae mutants which we have isolated, 15 are specifically affected in ribonucleic acid (RNA) synthesis . Four of these mutants exhibit particularly drastic changes and were chosen for a more detailed study . In these four mutants, RNA synthesis is immediately blocked after a shift at the nonpermissive temperature (37 C), protein synthesis decays at a rate compatible with messenger RNA half-life, and deoxyribonucleic acid synthesis increases by about 40% . All the mutations display a recessive phenotype . The segregation of the four allelic pairs ts-/ts+ in diploids is mendelian, and the four mutants belong to three complementation groups . The elution patterns (diethylaminoethyl-Sephadex) of the three RNA polymerases of the mutants grown at 37 C for 3.5 h show very low residual activities . The in vitro thermodenaturation confirms the in vivo results; the half-lives of the mutant activities at 45 C are 10 times smaller than those of the wild-type enzymes . Polyacrylamide gel electrophoresis shows that the synthesis of all species of RNA is thermosensitive . The existence of three distinct genes, which are each indispensable for the activity of the three RNA polymerases in vivo as well as in vitro, strongly favors the hypothesis of three common subunits in the three RNA polymerases.

Gene, 1976, 1(1), 33 - 47
Synthesis of high molecular weight polypeptides in Escherichia coli minicells directed by cloned Saccharomyces cerevisiae 2-micron DNA; Hollenberg CP et al.; The minicell-producing Escherichia coli strain P 678-54 was transformed with a series of defined PTY chimeric plasmids consisting of yeast 2-micron DNA and E . coli plasmid pCR1 . In minicells the integrated 2-micron DNA from yeast directed specifically the synthesis of six polypeptides with apparent molecular weights of 15,000, 17,500, 20,000, 22,000, 37,000, AND 48,000 . The specificity of five other polypeptides, which cover a molecular weight range of 19,000 to 28,000, has not yet been established with certainty . Neither the orientation of the integrated DNA, nor the inversion which distinguishes the two structural forms of 2-micron DNA affected the polypeptides synthesized . However, integration at a given EcoRI site appeared to be correlated with the absence of one particular polypeptide band; this suggests that at least one of these sites is located in an expressed region of the DNA.

Antonie Van Leeuwenhoek, 1976, 42(4), 397 - 410
The influence of conditions of growth on the endogenous metabolism of Saccharomyces cerevisiae: effect on protein, carbohydrate, sterol and fatty acid content and on viability; Wilson K et al.; The nature of the endogenous reserves of Saccharomyces cerevisiae was examined with respect to conditions of growth, specifically extremes of oxygen tension and carbon source . Cells were grown in batch culture at 30 C under aerobic conditions on a galactose or glucose carbon source and under anaerobic conditions on glucose . The greatest effect of growth conditions on the chemical composition of the cells was on their fatty acid and sterol content . Cells grown under both aerobic and anaerobic conditions mobilised concurrently protein, glycogen, trehalose and fatty acids during a period of 72 hours' starvation under aerobic conditions . The viability of both types of the aerobically grown cells declined to 75% during this period and was not influenced by the initial fatty acid and sterol content of the cells . Cells grown anaerobically showed a more rapid decline in viability which was only 17% after 72 hours' starvation . This loss of viability was not due to a lack of available endogenous reserves but was probably due to an impaired membrane function caused by a deficiency of sterols and unsaturated fatty acids.

Antonie Van Leeuwenhoek, 1976, 42(3), 293 - 7
The substrate constant for the ammonium ion of growing Saccharomyces cerevisiae; Middelhoven WJ et al.; The relation between ammonium concentration and growth rate was studied in steady state continuous cultures of Saccharomyces cerevisiae in nitrogen-limited glucose ammonium medium . This relation could be described by the Monod equation . A maximum specific growth rate of 0.41 h-1 and a substrate constant for ammonium of 5-11 muM were calculated . Ammonium was determined by a modification of the phenol hypochlorite method . A discussion of the results in view of literature data on the substrate constants for other nutrients is given.

Acta Microbiol Acad Sci Hung, 1976, 23(2), 109 - 20
Regulation of methionine synthesis in Saccharomyces cerevisiae operates through independent signals: methionyl-tRNAmet and S-adenosylmethionine; Surdin-Kerjan Y et al.; The synthesis of at least six enzymes implicated in methionine biosynthesis in Saccharomyces cerevisiae is regulated pleiotropically by two independent regulatory systems . Repression of enzyme synthesis is promoted either by exogenous methonine or by exogenous S-adenosylmethionine (SAM) . The regulatory system acting in methionine mediated repression seems to comprise methionyl-tRNA-met as a co-repressor and the other system, acting in SAM repression, comprises SAM as a co-repressor . This concept gives a role in regulation to the two activated forms of methionine . Moreover, evidence is presented that the "SAM repressor" probably acts at a post-transcriptional level while the "met-tRNAmet repressor" would be active at the transcriptional level . These conclusions have been based on two series of experiments: one using a mutant bearing a modified methionyl-tRNA synthetase {L-methionine: tRNA-met ligase (AMP-forming) E.C.6.1.1.10} and one studying the kinetics of depression of synthesis of one of the biosynthetic enzymes after repression either by exogenous methionine or by exogenous SAM . Our results are strengthened by the use of two different drugs: one inhibiting messenger RNA synthesis and the other inhibiting protein synthesis.

Biochimie, 1976, 58(1-2), 225 - 32
Purification and properties of threonine deaminase from Saccharomyces cerevisiae; Ahmed SI et al.; Threonine deaminase (L-theonine hydro-lyase (deaminating), E.C . 4.2.1.16) has been purified to homogeneity from extracts of Saccharomyces cerevisiae . When purified 1200-fold, the enzyme is homogeneous by the criterion of sodium dodecyl sulfate-polyacrylamide electrophoresis . The reduced and alkylated protein has a molecular weight of approximately 50,000 daltons, one-fourth the value determined previously for the intact enzyme . The purified enzyme exhibits homotropic effects with the substrate; these effects are descresed in the presence of DL-allothreonine, a competitive inhibitor . Half-maximal velocity is achieved at 34 mM L-threonine in the absence of other effectors . L-isoleucine both stimulates at low (0.01-0.05 mM) concentrations and inhibits at high (0.1-1.0 mM) concentrations . Valine activates the enzyme in the absence of isoleucine ; in the presence of isoleucine it reverses inhibition.

Biochimie, 1976, 58(1-2), 219 - 24
Control of enzyme synthesis and stability during sporulation in Saccharomyces cerevisiae; Klar AJ et al.; Studies were undertaken to understand the control of synthesis, stability and modification of UDP galactose epimerase and DNA-dependent RNA polymerase during sporulation of Saccharomyces cerevisiae . When a pre-induced culture of an inducible strain (wild type) is transferred to sporulation medium, the epimerase is inactivated to an undetectable level within 16 hours . Surprisingly, the addition of cycloheximide, a protein synthesis inhibitor, during sporulation stabilizes the epimerase activity . However, in a constitutive strain, the epimerase continues to be synthesized de novo during sporulation . Since the enzyme is synthesized during both vegatative growth and sporulation constitutively, the controls for synthesis of epimerase must be similar under these physiologically different conditions . After chromatography on DEAE Sephadex, there is no change observed in the elution patterns of RNA polymerase forms extracted from acetate growth vegetative cells, sporulating cells or from mature asci ; in all cases RNA polymerase consists of three forms, Ib, II and III . However, single spore suspension obtained from asci by treatment with zymolase contains a new form with chromatographic properties similar to those of form Ia . Our data suggests that form Ia may be a modification product of from Ib.

Biochimie, 1976, 58(1-2), 207 - 11
Non specific induction of arginase in Saccharomyces cerevisiae; Dubois EL et al.; Some aminoacids metabolically and structurally unrelated with arginine catabolic compounds induce arginase . This effect designated as non specific induction procedes by a mechanism distinct from three others acting on the synthesis of arginase : specific induction, nitrogen catabolite repression and catabolic synergism.

Mutat Res, 1976 Jan, 34(1), 123 - 30
Use of snail enzyme for the selection of glucose-and mannose-negative mutants in Saccharomyces cerevisiae; Herrera LS; The relationship between growth and sensitivity of Saccharomyces cerevisiae cells to snail enzyme led us to work out the conditions for using this enzyme to isolate mannose-negative and glucose-negative mutants . The technique is based on a prior growth on a glycerol medium in which any cell becomes resistant to snail enzyme, followed by a period of growth in a medium in which only the wild-type cells can grow, thereby becoming sensitive to the enzyme . This technique was very effective in both tested cases . This result suggests that the method described might also be applied to isolate other kinds of mutant.

Acta Physiol Lat Am, 1976, 26(5), 303 - 9
Mitochondrial production of hydrogen peroxide in Saccharomyces cerevisiae; Boveris A; Intact mitochondria isolated from bakers' yeast and showing respiratory control by ADP, released H2O2 to the suspending medium at rates of 1.2.2.2 nmol/min per mg of protein depending on the mitochondrial metabolic condition . Release of H2O2 from mitochondria increased 1.3 times in swollen mitochondria and 1.2 times after osmotic shock, i.e., when the outer membrane was damaged . Under physiological conditions, yeast cytochrome c peroxidase, mainly located in the intermembrane space, utilized about 53-55% of the H2O2 generated by the respiratory chain at the inner membrane, partially preventing H2O2 diffusion to the cytosol . Apparently, the outer mitochondrial membrane was highly permeable to H2O2 . It is claimed that the risk of cell injury due to H2O2, O-2 and HO is slightly higher in the stationary phase than in the logarithmic phase of growth.

Rev Ig Bacteriol Virusol Parazitol Epidemiol Pneumoftiziol Bacteriol Virusol Parazitol Epidemiol, 1976 Jan-Mar, 21(1), 33 - 6
{Study of the incorporation of radioactive zinc in Saccharomyces cerevisiae aldolase}; Rabega C et al.; Saccharomyces cerevisiae aldolase concentrates from the culture medium containing ZnSO4 a large amount of Zn which becomes a component part of the enzyme molecular structure . This was made evident by adding to the culture medium 65ZnSO4 and measuring the radioactivity of the aldolase extracted by a Phillips single channel analyzer.

Z Naturforsch {C}, 1976 Jan-Feb, 31(1-2), 85 - 90
{Size comparison of poly (A)-RNA from polysomes and from nuclei of the yeast Saccharomyces cerevisiae (author's transl)}; Angermann K et al.; The size of poly (A)-RNA from polysomes and cell nuclei of the yeast Saccharomyces cerevisiae was investigated . Pulslabelled cells ({14C} adenin) were cracked by the French press; polysomes and nuclei were separately isolated and the RNA was finally extracted with phenol . The separation of poly (A)-containing and poly (A)-lacking fractions was achieved by oligo (dT) cellulose . These fractions were characterized by sedimentation analysis . The main portion of polysomal poly (A)-RNA sedimented with a rate of 8 to 14S, whereas the poly (A)-RNA of nuclei exhibited a sedimentation rate of 12 to 17S . Thus nuclear poly (A)-RNA is about 20-30% larger than polysomal poly (A)-RNA.

Acta Microbiol Acad Sci Hung, 1976, 23(4), 377 - 85
{Remarks on the modifications of cell wall during the sporulation of Saccharomyces cerevisiae Hansen (author's transl)}; Boudier D et al.; Evolution of cell wall during sporulation was studied by means of scanning electron microscopy and by immunological techniques . Experiments were done simultaneously with a strain a/alpha able to sporulate and a strain alpha/alpha unable to sporulate . Under such conditions it was possible to clarify whether the changes observed were related to the sporulation or to the culture conditions . Cell wall structure modifications during sporulation were not obvious morphologically but have been revealed by immunological methods . During vegetative growth, antigenic sites of strains a/alpha and alpha/alpha were different . During incubation in the sporulation medium, antigenic structure of the cell wall was modified . Some antigenic sites seem to be specific of sporulation.

Acta Microbiol Pol, 1976, 25(4), 295 - 305
Survival and liquid holding recovery in UV-sensitive strains of Saccharomyces cerevisiae after treatment with chemical mutagens and radiation; Swietlinska Z et al.; Two UV-sensitive mutants of Saccharomyces cerevisiae rad 3 and rad 6 were tested for sensitivity to X-rays, MMS, EMS, HNO2 and DEB . Rad 3 mutant is more sensitive than the wild type strain only to HNO2 and DEB, while rad 6 is cross sensitive both to X-rays and all chemicals tested . Liquid holding recovery (LHR) was studied by comparison of cell survival immediately after mutagen treatment and after 5 days of storage in phosphate buffer . LH greatly increases cell survival of rad 3 mutant after DEB and slightly after EMS, MMS and HNO2, while after UV treatment LH significantly decreases survival of this mutant . LH increases survival of rad 6 mutant after exposure to UV, MMS and HNO2, but decreases survival of DEB-treated cells . Exposure of wild type strain to LH results in an increase of survival after UV, and DEB but not after MMS and HNO2 . The results suggest that LHR is a strain- and mutagen-specific phenomenon and cannot be explained within the present knowledge of repair processes in yeast.

Antonie Van Leeuwenhoek, 1976, 42(4), 511 - 21
Mating reaction in Saccharomyces cerevisiae . X . Agglutinability-inactivating factor: a factor which destroys sexual agglutinability of a mating-type cells; Shimoda C et al.; From cells of Saccharomyces cerevisiae a factor has been extracted that destroys the agglutinability of a mating-type cells specifically . It was found in the cell extracts of diploid and tetraploid strains as well as haploid strains of a and alpha mating types . It is heat-labile and the molecular weight is about 50,000 . It is adsorbed by neither a cells nor alpha cells . Its biological activity is dependent on the incubation temperature and the pH, and is completely inhibited by phenylmethylsulfonyl fluoride, a potent inhibitor of the serine proteases . All the results described in this paper indicate that this factor is a proteolytic enzyme.

Arch Microbiol, 1975 Dec 31, 106(3), 159 - 64
Promotion of sporulation by caffeine pretreatment in Saccharomyces cerevisiae . I . Metabolism of nucleic acids and protein during sporulation; Tsuboi M et al.; Cells cultured in the presence of caffeine had high sporulation ability . The sporulation-promotive effect of caffeine was studied, special attention being paid upon changes in nucleic acid metabolism . When transferred to a sporulation medium, the breakdown of RNA, the synthesis of protein, RNA and DNA, commitment to sporulation and the appearance of mature asci took place in caffeine-treated cells significantly earlier than in control cells . Commitment to sporulation occurred before the completion of premeiotic DNA synthesis in both caffeine-treated and control cells.

Mol Gen Genet, 1975 Dec 30, 143(1), 65 - 70
Genes coding for the structure of the acid phosphatases in Saccharomyces cerevisiae; Toh-e A et al.; The phoE locus, one of the loci in which mutations lack the activity for repressible acid phosphatase, was found to be the structural gene for the enzyme by examining the enzymic characteristics of repressible acid phosphatase activity using cell extracts prepared from the leaky phoE mutants, the PHOE revertants and the PHOE recombinants between the different phoE mutants . Other evidence which strongly suggests that the phoC locus is coding for the constitutive acid phosphatase was obtained by a similar investigation . Although the phoC and phoE loci are tightly linked, they were separable by meiotic recombination.

Mol Gen Genet, 1975 Dec 23, 142(1), 13 - 7
Cytogenetic demonstration of mitotic chromosomes in the yeast Saccharomyces cerevisiae; Wintersberger U et al.; A cytogenetic study of the nuclear material of the yeast Saccharomyces cerevisiae as it appears during mitosis was undertaken using a technique which combines light and electron microscopic examination of spheroplasts . Condensation of chromatin into separate chromosomes is observed . The most frequent chromosome number counted is 18.

Biochim Biophys Acta, 1975 Dec 19, 414(3), 263 - 72
Abundant species of poly(A)-containing RNA from Saccharomyces cerevisiae; Shalitin C et al.; Hybridization experiments using uniformly labeled poly(A) RNA derived from Saccharomyces cerevisiae strains carrying the "killer character" showed that (1) these molecules appear to be transcribed from repetitive DNA sequences . (2) there are approximately 35 DNA template sequences that are transcribed into poly(A) RNA . It is concluded that under the RNA extraction procedure used, most of the poly (A) RNA represents killer-RNA as judged by the dependence of the kinetic complexity of poly(A) RNA on the genomic complexity of killer-RNA.

J Biol Chem, 1975 Dec 10, 250(23), 9130 - 6
Requirements for unsaturated fatty acids for the induction on respiration in Saccharomyces cerevisiae; Walenga RW et al.; Unsaturated fatty acids provided during the release from glucose repression were shown to be essential for derepression of respiration in an unsaturated fatty acid auxotroph of Saccharomyces cerevisiae (KD115) . Cells derepressed in the presence of oleic acid contained three to six times as much cytochrome per cell as those derepressed in the absence of unsaturated fatty acid or those derepressed with eicosaenoic acid . The delta9 isomer was the most efficient of the cis-octadecenoic acid isomers in supporting that increase, and eicosaenoic acid supported an increase at only 15% the rate observed with oleic acid . Derepression, even in the presence of oleic acid, proceeded only after a lag of 3 hours . When glucose was removed prior to the addition of oleate, the lag was reduced by the time of the preincubation with glycerol . This result suggests that some processes necessary for increased respiration can proceed in the absence of an added unsaturated fatty acid, but these processes apparently require certain levels of unsaturated acids in the pre-existing lipids, since they occurred in cells whose membranes contained 50 mol % oleate, but not in cells containing only 20 mol % . These processes leading to eventual increased respiration were inhibited by cycloheximide but not chloramphenicol, suggesting that protein synthesis on cytoplasmic ribosomes but not mitochondrial ribosomes were required . Derepression in the absence of oleate for 3 hours lessened the inhibition or respiration induction by ethidium bromide . This result indicates that the transcription of mitochondrial DNA necessary for the induction of respiration may have occurred in the absence of added unsaturated fatty acid, but that some subsequent event required added esterified unsaturated fatty acid.

J Biol Chem, 1975 Dec 10, 250(23), 9121 - 9
Effectiveness of various unsaturated fatty acids in supporting growth and respiration in Saccharomyces cerevisiae; Walenga RW et al.; The saturated fatty acid auxotroph of Saccharomyces cerevisiae, KD115, was used to determine the efficiency of various unsaturated fatty acids in supporting growth . The efficiency, as the number of cells produced per fmol of unsaturated fatty acid, ranged from zero for a number of acids to over 26 cells per fmol of eicosapentaenoic acid . Efficiencies tended to be higher for acids with fewer carbons or more double bonds . In a series of positional isomers of cis-octadecenoic acid, the delta9 isomer had the greatest efficiency (12 cells per fmol) . Exogenous oleic acid was taken up and incorporated into cellular lipid early in the growth of the cells . Further growth proceeded with a decrease in the relative content of oleate in lipids until a minimum value of 9 mol % was reached at stationary phase . The initial concentration of supplemental acid did not affect the final mole % value . Other unsaturated fatty acids reached limiting values of mole % in phospholipid at stationary phase that were characteristic for the acid used . When cells were grown with glycerol as the carbon source, the efficiencies of most acids in supporting growth were one-third to one-fifth the value with glucose and the final mole % of supplement acid in phospholipid at stationary phase was two to five times greater . Apparently, mitochondrial energy transduction necessary for glycerol utilization requires higher levels of unsaturated fatty acids in membrane lipids than do extramitochondrial functions . The respiratory rate of mitochondria was not decreased at lower levels of oleic or palmitoleic acid in lipids, although respiratory control was lower when the mole % of unsaturated fatty acid was lower . Mitochondria from cells supplemented with eicosaenoic acid were found to have both low respiration and respiratory control . The decreased respiration of these mitochondria coincided with a decreased cytochrome content, not a decrease in respiration per mol of cytochrome.

Mol Gen Genet, 1975 Dec 9, 141(4), 285 - 90
The restriction of the recombination of mitochondrial DNA molecules in the zygotes of Saccharomyces cerevisiae; Waxman MF; Crosses were made between strains carrying a nuclear control factor (NC) and strains classified with respect to their omega allele (omega+ or omega-) . The characteristic asymmetrical transmission was always observed (as was seen) in crosses not involving the omega factor . The analysis of functional recombinants in a cross involving an NC factor has indicated that the absence of the omega effect may be caused by a restriction in the zygote of the recombination of mitochondrial DNA molecules.

Proc Natl Acad Sci U S A, 1975 Dec, 72(12), 5056 - 60
Electron microscopic observations on the meiotic karyotype of diploid and tetraploid Saccharomyces cerevisiae; Byers B et al.; Certain strains of Saccharomyces cerevisiae contain visible segments of synaptonemal complex which are apparent components of bivalents in pachytene of meiotic prophase . The synaptonemal complex has the typical width in the frontal plane but is unusually thin in the sagittal plane, thus accounting for its poor visibility . Amorphous densities situated adjacent to the central element occur at intervals suggesting their coincidence with sites of crossing over . Reconstruction of the synaptonemal complex from serial sections has permitted karyotypic analysis . The number of segments of synaptonemal complex and the distribution of their legths is consistent with the genetic map . Two, possibly three, segments enter the nucleolus as if bearing sequences encoding ribosomal RNA . Reconstruction of tetraploid nuclei reveals an approximate doubling of the diploid chromosome number and confirms the pattern of nucleolar entry . Quadrivalent pairing is evident between the pairs of synaptonemal complex segments in the tetraploid nuclei.

J Gen Microbiol, 1975 Dec, 91(2), 217 - 24
Genetical and biochemical aspects of resistance to p-fluorophenylalanine in Saccharomyces cerevisiae; Rhodes PM et al.; Growth of haploid yeast strains was inhibited by the phenylalanine (PA) analogue DL-p-fluorophenylalanine (FPA) in yeast extract media containing 0-2 mg PA/ml . Most strains had a maximum FPA tolerance of about 0-25 mg/ml when glycerol was the carbon source and 0-5 mg/ml in in glucose medium . Spontaneous FPA-resistant mutants isolated on glucose medium showed little or no increase in FPA tolerance over that of the parent when metabolizing glycerol . Resistance was controlled by a different nuclear gene in each of four mutants analysed . In a proportion of the mutants the amount of FPA incorporated into cellular proteins in competition with PA was less than into the proteins of sensitive parental cells, whether glucose or glycerol was used as carbon source . This suggests that the mutational change allowed the cytoplasmic system to descriminate against the analogue without affecting its incorporation into mitochondrially-synthesized proteins . Although attempts to measure the latter were not made, the observed decrease in respiratory activity of cells grown in the presence of FPA suggests such incorporation . In other mutants showing resistance to FPA in glucose medium, the amount of FPA incorporated into cellular proteins varied with the carbon source, less analogue being incorporated in glucose medium than in glycerol medium.

Mutat Res, 1975 Dec, 30(3), 335 - 42
Induction of rho- mutants in Saccharomyces cerevisiae by guanidine hydrochloride . II . Conditions that prevent rho- induction; Juliani MH et al.; The induction of rho- "petite" mutants by guanidine hydrochloride (GuHCl) is inhibited in several conditions . Anaerobiosis inhibited the induction either with or without cell multiplication . Both nalidixic acid (NA) and cycloheximide (CH) inhibited the induction of mutants . On the other hand, chloramphenicol (CAP) produced a dual effect: at low concentration it stimulated, at high concentration it inhibited, the induction . The effect of these different inhibitors on the transformation of rho+ mother cells into rho- by GuHCl is discussed.

Mutat Res, 1975 Dec, 30(3), 327 - 34
Induction of DNA double-strand breaks by X-rays in a radiosensitive strain of the yeast Saccharomyces cerevisiae; Ho KS; Sedimentation profiles for chromosomal DNA from unirradiated and X-irradiated yeast cells of wild type and rad 52 strains are presented . These profiles indicate that, whereas wild type strains rejoin DNA double-strand breaks, rad 52 strains apparently do not . These data suggest that the rad 52 mutant lacks a repair system for X-ray induced damage and are consistence with the proposal that an unrepaired chromosome break leads to reproductive cell death.

J Bacteriol, 1975 Dec, 124(3), 1041 - 5
Gene dosage effects in polyploid strains of Saccharomyces cerevisiae containing gua-1 wild-type and mutant alleles; Reichert U et al.; Triploid and tetraploid Saccharomyces strains containing different combinations of a gua-1 mutant allele and the corresponding wild type were prepared . The cultivation of the different strains in media upon which the mutant fails to grow leads to a pronounced growth rate response to the dosage of the wild-type allele . Proportionality between the specific activity of the guanosine 5'-monophosphate synthetase and the wild-type dosage was reavealed . Inosine 5'-monophosphate dehydrogenase, the precursor enzyme in the pathway, is derepressed in a sigmoid manner when the wild-type dosage is reduced, whereas the activity of cytosine deaminase, investigated as a reference enzyme, is less affected.

Mutat Res, 1975 Dec, 33(2-3), 173 - 8
Effect of caffeine on recovery from DEB-induced cell inactivation in UV-sensitive mutants of Saccharomyces cerevisiae; Zuk J et al.; The UV-sensitive yeast mutants rad3 and rad6 are highly sensitive to diepoxybutane (DEB) as compared with the RAD strain . The two mutants show differential response to liquid holding (LH) after exposure to DEB and UV . The survival of rad3 increases markedly after DEB and decreases after UV . Caffeine significantly affects LH recovery of DEB-treated RAD strain, slightly decreases recovery of rad3 and has almost no effect on survival of rad6 . When DEB-treated cultures are plated immediately on caffeine-containing medium, survival of rad3 decreases more significantly than that of the RAD strain, whereas survival of rad6 is only slightly decreased as compared with the untreated cultures . Possible mechanisms of recovery from DEB-induced cell damage are discussed.

Mutat Res, 1975 Dec, 33(2-3), 157 - 64
Two mutations which confer temperature-sensitive radiation sensitivity in the yeast Saccharomyces cerevisiae; Ho KS et al.; X-ray survival curves for two mutations, rad54 and rad55, in the yeast Saccharomyces cerevisiae are presented . These mutations confer temperature sensitive X-ray sensitivity; that is rad54 and rad55 strains display a wild type X-ray survival response at permissive temperatures and a radiosensitive X-ray survival response at restrictive temperatures . The survival response of cells which were shifted from a permissive to a restrictive temperature or vice versa at various post-irradiation times indicates that repair and fixation of X-ray induced lesions is largely complete three hours after X-irradiation . Experiments to determine the utilization sequence of the rad54 and rad55 gene products in the repair of X-ray induced damage suggest that the two products are required in an interdependent manner.

Eur J Biochem, 1975 Nov 15, 59(2), 373 - 6
Isolation and properties of an arginine-binding protein from Saccharomyces cerevisiae; Opekarova M et al.; Transfer of exponentially growing cells of Saccharomyces cerevisiae epsilon 1278 b to a fresh medium (or simply to distilled water) resulted in the loss of ability to transport arginine (and lysine), accompanied by the release of several proteins from the membrane surface or periplasmic space . Fractionation by ultrafiltration, Sephadex G-50 chromatography and freeze-drying yielded a homogeneous protein (55 mg per 100 g dry weight of cells) with specific binding ability for L-arginine (Kd = 3.8 X 10(-1) M) and L-lysine (Ki = 4.2 X 10(-4) M) . The protein contains over 40 amino acid residues and has a molecular weight of about 5,000 . In solution, it appears to aggregate as its concentration is raised, thereby decreasing the overall binding capacity for arginine . Addition of the protein to a depleted culture does not restore the transport of arginine . It is apparently the recognition protein for the specific arginine-transporting system of Saccharomyces cerevisiae but it occurs in almost identical amounts in the MG 168 mutant with impaired arginine transport.

Mol Gen Genet, 1975 Nov 3, 141(1), 81 - 3
Two new genes controlling the constitutive acid phosphatase synthesis in Saccharomyces cerevisiae; Toh-e A et al.; Two new classes of mutants, phoF and phoG, lacking the constitutive acid phosphatase activity, were isolated . They both complemented each other and the phoC mutation . No linkage was detected among these three complementary genes.

Mol Gen Genet, 1975 Nov 3, 141(1), 9 - 22
Biogenesis of mitochondria 36, The genetic and biochemical analysis of a mitochondrially determined cold sensitive oligomycin resistant mutant of Saccharomyces cerevisiae with affected mitochondrial ATPase assembly; Trembath MK et al.; The isolation and characterisation of a mutant affecting the assembly of mitochondrial ATPase is reported . The mutation confers resistance to oligomycin and venturicidin and sensitivity of growth on nonfermentable substrates to low temperature (19degrees) . Genetic analysis indicates that the phenotype is due to a single mutation located on the mitochondrial DNA which is probably allelic with the independently isolated oligomycin resistance mutation {oli1-r} . Growth of the mutant at the non-restrictive temperature (28degrees) yields mitochondria in which the ATPase appears more sensitive to oligomycin than that of the sensitive parental strain . However, when the enzyme is isolated free from the influence of the membrane strong resistance to oligomycin is evident . These data suggest that the component responsible for the oligomycin resistance of the ATPase is part of or subject to interaction with the mitochondrial inner membrane . Measurements of the ATPase content of mitochondria indicate that ATPase production is impaired during growth at 19degreesC . In addition, studies of the maximum inhibition of mitochondrial ATPase activity by high concentrations of oligomycin suggest a selective lesion in ATPase assembly at low temperature . The nett result is that during growth at 19degrees only about 10% of the normal level of ATPase is produced of which less than half is membrane integrated and thus capable of oxidative energy production . We propose that the mutation affects a mitochondrially synthesised membrane sector peptide of the ATPase which defines the interaction of F1ATPase with specific environments on the mitochondrial inner membrane.

Proc Soc Exp Biol Med, 1975 Nov, 150(2), 503 - 9
Evidence for the dark repair of ultraviolet damage in Saccharomyces cerevisiae mitochondrial DNA; Hixon SC et al.; Evidence for the dark repair of ultraviolet damage to yeast mitochondrial DNA has been observed . The ultraviolet dose necessary to inflict significant damage to both nuclear and mitochondrial DNA was determined . Cell survival at large doses of ultraviolet light was observed after immediate and delayed plating of yeast onto 1% pyruvate and 1% glucose media . In the highly lethal dose ranges of irradiation an increase in the number of normal colonies appeared after a period of liquid holding and delayed plating . This increase, demonstrated separately on 1% glucose and 1% pyruvate media suggested that the repair of both mitochondrial and nuclear DNA had occurred . After low doses of ultraviolet light an actual decrease in the number of petite survivors was seen after delayed plating, even though the total number of survivors increased . When a known repair inhibitor, caffeine, was added to the liquid holding buffer prior to the delayed plating of yeast, a marked decrease in the number of petites did not occur after delayed plating . Therefore, the decrease in the number of petite survivors after delayed plating following low doses of ultraviolet light is attributed to the repair of yeast mitochondrial DNA.

J Bacteriol, 1975 Nov, 124(2), 863 - 9
Proteinase activities of Saccharomyces cerevisiae during sporulation; Klar AJ et al.; Sporulation in Saccharomyces cerevisiae occurs in the absence of a exogenous nitrogen source . Thus, the internal amino acid pool and the supply of nitrogen compounds from protein and nucleic acid turnover must be sufficient for new protein synthesis . Since sporulation involves an increased rate of protein turnover, an investigation was conducted of the changes in the specific activity of various proteinases . A minimum of 30% of the vegetative proteins was turned over during the course of sporulation . There was a 10- to 25-fold increase in specific activity of various proteinases, with a maximum activity around 20 h after transfer into the sporulation medium . The increase in activities was due to de novo synthesis since inhibition of protein synthesis by cycloheximide blocks both an increase in proteinase activities and sporulation . There was no increase observed in proteinase activities of nonsporogenic cultures (a and alpha/alpha strains) inoculated into the sporulation medium, suggesting that the increase in proteinase activities is "sporulation specific" and not a consequence of step-down conditions . The elution patterns through diethylaminoethyl-Sephadex chromatography of various proteinases extracted from T0 and T18 cells were similar, and no new species was observed.

J Bacteriol, 1975 Nov, 124(2), 718 - 23
Factors affecting the palmitoyl-coenzyme A desaturase of Saccharomyces cerevisiae; Klein HP et al.; The activity and stability of the palmitoyl-coenzyme A (CoA) desaturase complex of Saccharomyces cerevisiae was influenced by several factors . Cells, grown nonaerobically and then incubated with glucose, either in air or under N2, showed a marked increase in desaturase activity . Cycloheximide, added during such incubations, prevented the increase in activity, suggesting de novo synthesis . The stability of the desaturase from cells grown nonaerobically was affected by subsequent treatment of the cells; enzyme from freshly harvested cells, or from cells that were then shaken under nitrogen, readily lost activity upon washing or during density gradient analysis, whereas aerated cells, in the presence or absence of glucose, yielded stable enzyme preparations . The loss of activity in nonaerobic preparations could be reversed by adding soluble supernatant from these homogenates and could be prevented by growing the cells in the presence of palmitoleic acid and ergosterol, but not with several other lipids tested.

Mikrobiologiia, 1975 Nov-Dec, 44(6), 1005 - 9
{Effect of cultivation conditions on the electrophoretic spectrum of various dehydrogenases in Saccharomyces cerevisiae}; Popova MV et al.; The activity and electrophoretic spectrum of glucose-6-phosphate dehydrogenase, alcohol dehydrogenase, and malate dehydrogenase in Saccharomyces cerevisiae 14 depended on the conditions of cultivation, i . e . the sources of carbon and their concentration, the content of nitrogen, and aeration of the medium . A heterogeneous tris-buffer protein fraction was isolated after disintegration of the cells; the dehydrogenases were represented by several molecular forms whose number, electrophoretic mobility, and activity depended on the conditions of cultivation.

Z Naturforsch {C}, 1975 Nov-Dec, 30(6), 804 - 10
An improved assay of UV-induced thymine-containing dimers in Saccharomyces cerevisiae; Fath WW et al.; The method for assaying thymine-containing dimers in yeast is based on highly efficient ({3H}-deoxythymidine-5'-monophosphate) DNA-specific labelling and employs ascending thin layer chromatography . It allows satisfactory quantitative analysis down to UV-doses of 500 erg/mm2.

Arch Microbiol, 1975 Oct 27, 105(2), 83 - 6
Comparative studies on sporulation-promotive actions on cyclic AMP, theophylline and caffeine in Saccharomyces cerevisiae; Tsuboi M et al.; Cyclic AMP, theophylline and caffeine promoted sporulation when added to a presporulation medium containing glucose . Caffeine promoted sporulation even when added to a presporulation medium containing acetate as the carbon source, but cyclic AMP and theophylline did not . Caffeine did not increase the intracellular cyclic AMP level, while theophylline did significantly when added to a presporulation medium containing glucose . Caffeine inhibited the vegatative DNA synthesis with little effect on RNA and protein synthesis, resulting in the increase in cell volume, dry weight, and RNA and protein contents, but cyclic AMP and theophylline did not show such effects.

J Biol Chem, 1975 Oct 25, 250(20), 8236 - 42
Assembly of the mitochondrial membrane system . Cytoplasmic mutants of Saccharomyces cerevisiae with lesions in enzymes of the respiratory chain and in the mitochondrial ATPase; Tzagoloff A et al.; Mutants of Saccharomyces cervisiae with defects in enzymes of the electron transfer chain and in the rutamycin-sensitive ATPase have been isolated . Some of the mutants are specifically affected in either cytochrome oxidase, coenzyme QH2-cytochrome c reductase or ATPase . Other strains are deficient in both cytochrome oxidase and coenzyme QH2-cytochrome c reductase but still have rutamycin-sensitive ATPase . All the mutants reported in this study fail to be complemented by a rho0 tester derived from a respiratory competent strain . The meiotic spore progeny obtained by mating the mutants to a respiratory competent haploid yeast, when scored for growth on glycerol, show a non-Mendelian segregation of the phenotype . These two genetic tests indicate the mutations to be cytoplasmically inherited.

J Biol Chem, 1975 Oct 25, 250(20), 8228 - 35
Assembly of the mitochondrial membrane system . Characterization of nuclear mutants of Saccharomyces cerevisiae with defects in mitochondrial ATPase and respiratory enzymes; Tzagoloff A et al.; Mutants of Saccharomyces cereviaiae showing defects in cytochrome oxidase, coenzyme QH2-cytochrome c reductase, and rutamycin-sensitive ATPase are described . The mutations have been established to be nuclear, based on complementation with a cytoplasmic petite tester strain and 2:2 segregation of tetrads . Genetic analysis indicate the coenzyme QH2-cytochrome c reductase and cytochrome oxidase mutants fall into 9 and 10 different complementation groups, respectively . The mutants also form distinct classes based on absorption spectra of the mitochondrial cytochromes . Two of the ATPase mutants lack detectable F1 ATPase, while the third synthesizes F1 but does not integrate it into a membrane complex . The latter mutant is missing one of the mitochondrially synthesized subunits of the rutamycin-sensitive ATPase complex.

Mol Gen Genet, 1975 Oct 22, 140(4), 361 - 70
Genetic control of invertase formation in Saccharomyces cerevisiae . I . Isolation and characterization of mutants affecting sucrose utilization; Hackel RA; Nine sucrose nonfermenting mutants have been isolated from yeast strain EK-6B, carrying the tightly linked SUC3 and MAL3 genes . These mutants are allelic to the SUC3 gene recessive in nature and none of them has detectable levels of either internal or external invertase . A single point mutation leading to the loss of both invertases suggests that either SUC3 is a control gene or codes for a polypeptide which is shared by both invertases.

Mol Gen Genet, 1975 Oct 22, 140(4), 333 - 7
Biogenesis of mitochondria 40 . Phenotypic suppression of a mitochondrial mutation by a nuclear gene in Saccharomyces cerevisiae; Trembath MK et al.; A mutant has been isolated which carries a nuclear mutation capable of suppressing certain aspects of the phenotype imposed by a specific mitochondrial mutation . The mitochondrial mutation {tso-r} confers cold sensitivity to growth on nonfermentable substrates and resistance to oligomycin . When both the mitochondrial and nuclear mutations are present in the same cell the cell is phenotypically cold resistant but retains a high level of oligomycin resistance . The extent of cold sensitivity suppression is dependent upon other unspecified nuclear genes . The molecular basis for the suppression may involve interactions between cytoplasmic and mitochondrial ATPase.

Eur J Biochem, 1975 Oct 15, 58(2), 533 - 8
Interaction between arginase and L-ornithine carbamoyltransferase in Saccharomyces cerevisiae . The regulatory sites of arginase; Penninckx M; The inhibition of ornithine carbamoyltransferase by arginase in Saccharomyces cerevisiae, which is under the control or arginine and ornithine, involves a regulatory site for arginine on the arginase distinct from its catalytic site . This regulatory site is responsible for the reinforcement effect of arginine on the inhibition of ornithine carbamoyltransferase by arginase . The binding site of ornithine carbamoyltransferase on arginase is also shown by our analysis.

Mol Gen Genet, 1975 Oct 3, 140(3), 231 - 41
Cytoplasmic inheritance in Saccharomyces cerevisiae: comparison of first zygotic budsite to mitochondrial inheritance patterns; Aufderheide KJ; Zygotic first budsite in Saccharomyces cerevisiae was studied in relation to defined mitochondrial inheritance systems: both petite and drug resistance . It was hypothesized that a highly asymmetric inheritance pattern would be correlated to a high frequency of first budsites on the petite or drug resistant end of the zygote (i.e., that portion of the zygote which was originally the drug resistant or petite haploid before zygote formation) . The data collected did not support the hypothesis . For drug resistance, the budsite pattern is identical for a highly biased and a moderately biased inheritance pattern . In a grande by grande cross there is a high probability of the first bud appearing on the conjugation bridge, with lower but equal probabilities of the first bud appearing on one end or the other of the zygote . A grande by petite cross changes this pattern to a high probability of the first bud appearing on the grade end of the zygote, with a lesser probability of the first bud appearing on the conjugation bridge and virtually no budding of the petite end . This phenomenon is independent of degree of neutrality or suppressiveness of the petite strain used, however . The difference between a grande and a grande by petite pattern may be due to the relative functional ability of the mitochondria in each end of the zygote . Tests using antimitochondrial drugs suggest that selection of first budsite on a zygote is a complex phenomenon, not simply dependent upon mitochondrial phenotype . In conclusion, selection of the first zygotic budsite appears to be independent of mitochondrial inheritance patterns.

Proc Natl Acad Sci U S A, 1975 Oct, 72(10), 3868 - 72
Restriction endonuclease analysis of mitochondrial DNA from grande and genetically characterized cytoplasmic petite clones of Saccharomyces cerevisiae; Morimoto R et al.; Digestion of grande mitochondrial DNA (mtDNA) BY EcoRI restriction endonuclease gives rise to nine fragments with a total molecular weight of 51.8 x 10(6) . HindIII digestion yields six fragments with a similar total molecular weight . Specific restriction fragments can be detected despite the fact that yeast mtDNA consists of a heterogeneous distribution of randomly broken molecules . Digestion patterns of 10 genetically characterized petite clones containing various combinations of five antiobiotic resistance markers indicate that the petite mtDNA predominantly represents deletion of the grande genome . The petite mtDNAs contained up to seven EcoRI restriction fragments which comigrate with grande restriction fragments, and at least one fragment that did not correspond to any in the grande . Some strains contained multiple fragments with mobility different from that of grande; these fragments were usually present in less than molar concentrations . The genetic markers were associated with individual sets of restriction fragments . However, several internal inconsistencies prevent the construction of a definitive genetic fragment map . These anomalies, together with the digestion patterns, provide strong evidence that, in addition to single contiguous deletion, other changes such as multiple deletion and heterogeneity of mtDNA populations are present in some of the petite mtDNAs.

Nucleic Acids Res, 1975 Oct, 2(10), 1777 - 86
Heterogeneity of mitochondrial DNA from Saccharomyces cerevisiae and genetic information for tRNA; Baldacci G et al.; Mitochondrial DNA from wild-type Saccharomyces cerevisiae and from an "extreme" petite mutant were analyzed by hybridization of several tRNAs on DNA fragments of different buoyant density, obtained by sonication and fractionation on a CsCl gradient . The hybridization patterns show that the genes for tRNAser, tRNAphe, tRNAhis, tRNAval, tRNAileu are present on wild-type mitochondrial DNA, while only genes for tRNAser and tRNAhis are present on petite mitochondrial DNA; moreover the hybridization patterns indicate that these genes are not clustered and suggest that more than one gene might exist for tRNAser and tRNAhis.

J Bacteriol, 1975 Oct, 124(1), 511 - 23
Behavior of spindles and spindle plaques in the cell cycle and conjugation of Saccharomyces cerevisiae; Byers B et al.; The interdependence of spindle plaque with other aspects of cell division and conjugation in Saccharomyces cerevisiae has been investigated . Three forms of the spindle plaque appear sequentially before the formation of the complete, intranuclear spindle . The single plaque is present initially in the mitotic cycle; it becomes transformed into a satellite-bearing single plaque during the latter part of G1 . Subsequently, plaque duplication yields the double plaque characteristic of the early phase of budding, which coincides with the period of chromosome replication (S) . The eventual separation of these plaques to form a complete spindle, with a single plaque at each pole, is nearly coincident with the completion of S . The form of the plaque differs in two independent cases of G1 arrest: the single plaque is found in a cell in stationary arrest of growth, whereas a cell arrested by mating factors in preparation for conjugation contains a satellite-bearing single plaque . The latter form is retained during zygote formation, where it serves as the initial site of fusion of each prezygotic nuceus with the other . This fusion results in the formation of a single zygotic nucleus with a satellite-bearing single plaque, which is subsequently transformed into a double plaque as the zygote buds . The double plaque is situated adjacent to the site of bud emergence in both vegetative cells and zygotes.

J Bacteriol, 1975 Oct, 124(1), 290 - 5
"Killer" character does not influence the transmission of mitochondrial genes in Saccharomyces cerevisiae; Young RA et al.; Three cytoplasmic genetic elements have been shown to be separate from mitochondrial deoxyribonucleic acid (DNA), {rho}, in Saccharomyces cerevisiae: the killer character {k}, omicron-DNA, and psi {psi} . Griffiths has suggested genetic interactions between {VENR} and {TETR} mutants possibly located on omicron-DNA and mitochondrial genetic markers, but possible interactions between the best characterized of the three, the killer character, and mitochondrial DNA have not been investigated . To test this we isolated cycloheximide-induced nonkiller segregants (NKS) of killer cells with suitable genetic markers and mated them in {k} x {k}, {k} x {k}, and (NKS) x (NKS) combinations . No differences in quantitative mitochondrial marker transmission between these groups were found in crosses illustrating the mitochondrial phenomena of bias, polarity, and suppressiveness . Our studies show that no intercellular interactions between {k} and (NKS) cells influence mitochondrial transmission genetics . Intracellular interactions between the smaller double-stranded ribonucleic acid of {k} and mitochondrial DNA also were not detected.

Eur J Biochem, 1975 Oct 1, 58(1), 177 - 84
Control of fatty-acid synthetase biosynthesis in Saccharomyces cerevisiae; Dietlein G et al.; 143 out of 308 fas1 mutants (47%) and 139 out of 443 fas2-mutants (32%) genetically studied in this laboratory fail to complement with any other fas-mutant (deficient in fatty acid synthetase) of the same gene locus . From these noncomplementing fas-mutants no mutant fatty acid synthetase can be isolated using the wild-type enzyme purification procedure . Furthermore the noncomplementing fas-mutants generally contain no material immunologically crossreacting with a specific fatty acid synthetase antiserum . However, subunits obtained after dissociation of the complex with sodium dodecylsulfate still cross react with this antiserum . Therefore, it is concluded that noncomplementing fas-mutants contain no fatty acid synthetase component proteins, though one of the two fas-loci is mutationally unaffected . This conclusion was further confirmed by 14C-labeled amino acid incorporation studies which indicated that in noncomplementing fas-mutants, other than in wild type and complementing fas-mutant cells, no label was incorporated into fatty acid synthetase subunits or precursor proteins . At nonpermissive temperature, the same biochemical and immunological characteristics were observed with temperature-sensitive non-complementing fas-mutants . These results suggest that noncomplementing fas-mutants either represent regulatory mutants unable to induce the mutationally unaffected other fas-gene locus or that they are association-defective mutants . In both cases the resulting individual subunits of the complex may be rapidly degraded by intracellular proteases.

Appl Microbiol, 1975 Oct, 30(4), 503 - 6
Mechanism of benzoic acid uptake by Saccharomyces cerevisiae; Macris BJ; A fast uptake of the preservative benzoic acid was observed in Saccharomyces cerevisiae, reaching saturation in about two min and then remaining constant at this level . The strong dependence of benzoic acid uptake on pH was due to the relative distribution of molecular and ionic forms in solution and not to the pH itself . The molecular form was the only one taken up by the cells . The specificity of the uptake mechanism was evidenced by the pattern of irreversible heat inactivation of the uptake system resembling protein denaturation by heat . Furthermore, the effect of temperature on the uptake was similar to that observed in enzymic reactions, whereas the kinetic data of uptake conformed to the Michaelis-Menten curve of saturation with a Km of 1.54 X 10(-2) M and Vmax of 3 X 10(-3) M/10s . The evidence presented in this paper indicates that compounds of protein nature are involved in the uptake of this preservative.

J Bacteriol, 1975 Oct, 124(1), 325 - 31
Inhibition of amino acid transport by ammonium ion in Saccharomyces cerevisiae; Roon RJ et al.; The rate of transport of L-amino acids by Saccharomyces cerevisiae epsilon 1278b increased with time in response to nitrogen starvation . This increase could be prevented by the addition of ammonium sulfate or cycloheximide . A slow time-dependent loss of transport activity was observed when ammonium sulfate (or ammonium sulfate plus cycloheximide) was added to cells after 3 h of nitrogen starvation . This loss of activity was not observed in the presence of cycloheximide alone . In a mutant yeast strain which lacks the nicotinamide adenine dinucleotide phosphate-dependent (anabolic) glutamate dehydrogenase, no significant decrease in amino acid transport was observed when ammonium sulfate was added to nitrogen-starved cells . A double mutant, which lacks the nicotinamide adenine dinucleotide phosphate-dependent enzyme and in addition has a depressed level of the nicotinamide adenine dinucleotide-dependent (catabolic) glutamate dehydrogenase, shows the same sensitivity to ammonium ion as the wild-type strain . These data suggest that the inhibition of amino acid transport by ammonium ion results from the uptake of this metabolite into the cell and its subsequent incorporation into the alpha-amino groups of glutamate and other amino acids.

J Bacteriol, 1975 Oct, 124(1), 127 - 33
Site of initial glycosylation of mannoproteins from Saccharomyces cerevisiae; Ruiz-Herrera J et al.; The cellular site of initial glycosylation of proteins from Saccharomyces cerevisiae has been studied . Short pulses of {U-14C}mannose label the ribosomal fraction of the yeast . Most of the label was associated with polysomes; monosomes contained only a small amount of radioactivity . All of the radioactivity present in the polysomal fraction was accounted by mannose and smaller amounts of glucose and glucosamine . Puromycin treatment detached more than 50% of the radioactivity from the polysomes; treatment of polysomes at pH 10.0 also caused the release of radioactivity . These results indicate that initial sugar binding occurs while the nascent polypeptide chains are still growing on the ribosomes . When the cells were preincubated with 2-deoxy-D-glucose, incorporation of {U-14C}mannose into the polysomes and the cell wall was inhibited, whereas its incorporation into membrane fractions was unimpaired . It was concluded that 2-deoxy-D-glucose inhibited the synthesis of glycoproteins by interference with the initial glycosylation steps at the ribosomal level.

Mol Gen Genet, 1975 Sep 29, 140(2), 149 - 58
Studies on a temperature sensitive nuclear petite mutant of Saccharomyces cerevisiae: phenotypic reversibility of the mitochondrial functions; Guerrini AM et al.; 1 . We have studied the pleiotropic effect of a single-gene mutation of the pts mutant strain 1511 grown at 23 degrees C and 36 degrees C . 2 . Growth of the mutant at the non-permissive temperature results in a decrease of respiration rate to about 50% after one generation and to less than 5% after five generations . The cytochrome spectra analysis revealed that only cytochrome c was present after growth at 36 degrees C . 3 . Mitochondrial protein synthesis experiments in vivo demonstrated that the protein synthesizing system was not as rapidly inactivated by high temperature as the respiratory system . 4 . The recovery of the respiratory capacity of the cells at 23 degrees C is complete but dependent on the de novo synthesis of a temperature sensitive protein.

Eur J Biochem, 1975 Sep 15, 57(2), 371 - 8
Binding studies of NADPH to NADP-specific L-glutamate dehydrogenase from Saccharomyces cerevisiae; Venard R et al.; Optical characteristics of enzyme-reduced coenzyme complexes of yeast NADP-specific glutamate dehydrogenase have been investigated in the presence and absence of product (L-glutamate) and in the presence or absence of phosphate . The phosphate effect, pointed out in a previous work, is found again: inorganic phosphate (Pi) destabilizes the binary complex (E - NADPH), the dissociation constant of which is equal to 14 muM, a value much higher than that determined in Tris-HCl buffer: Kd = 0.9 muM . Concerning the role of phosphate some assumptions are drawn up with respect to a similar behaviour of Pi toward yeast glutamate dehydrogenase and ADP toward the beef liver enzyme . In the same way, L-glutamate induces a stabilization of the binary complex; this latter effect is unchanged in the presence of phosphate, yet it is less marked than in the case of beef liver glutamate dehydrogenase . Protein fluorescence, nucleotide fluorescence and circular dichroism measurements allowed the determination of three identical and independent NADPH binding sites per hexameric active unit . In analogy with beef liver enzyme, it seems that yeast glutamate dehydrogenase is a good model to study anticooperativity in ligand binding.

Mol Gen Genet, 1975 Sep 8, 139(4), 303 - 9
Citrate synthaseless glutamic acid auxotroph of Saccharomyces cerevisiae; Burand JP et al.; Relationship of citrate synthase (EC 4.1.3.7) to the biosynthesis of glutamic acid was investigated by characterizing a new glutamic acid auxotroph FL100-D1 (glu 3) of Saccharomyces cerevisiae . Nutritional requirement of the mutant was satisfied by L-glutamic acid, L-glutamic acid peptide as well as several analogs of glutamic acid, but not by proline, ornithine, arginine, lysine or aspartic acid . The mutant was unable to utilize nonfermentable carbon sources, glycerol, acetate or lactate . Mutant glu3 unlike aconitaseless glutamic acid auxotroph glu 1, failed to accumulate 14C-citric acid in vivo from 1-14C-sodium acetate or U-14C-glutamic acid . Both spectrophotometric and radioactive assay procedures demonstrated a lack of significant citrate synthase activity in the dialysed extract of the mutant compared to the wild type strain . Mutant glu 3 complemented with glu 1 and glu 2 individually in vivo and exhibited a significant aconitase (EC 4.2.1.3) activity in vitro.

Genetics, 1975 Sep, 81(1), 75 - 97
Genetic and physiological characterization of met15 mutants of Saccharomyces cerevisiae: a selective system for forward and reverse mutations; Singh A et al.; One hundred and thirty-three spontaneous and induced mutants of the met15 locus in Saccharomyces cerevisiae were characterized with respect to temperature sensitivity, osmotic remediability, interallelic complementation, and suppressibility by amber and ochre suppressors . Forty mutants are osmotic remedial; 17 of these, and no others, are also temperature-sensitive . Seven of 133 mutations are suppressible by an amber suppressor and 11 are suppressible by an ochre suppressor . Seventy percent of the mutants exhibited interallelic complementation, suggesting that the functional gene product of the met15 gene is a multimeric protein . Relative map positions of 30 met15 were estimated from the frequencies of X-ray-induced mitotic reversion of various heteroallelic diploids . All complementing nonsense mutations are located near one end of the gene in contrast to other nonsense mutations which span most of the gene, thus relating the direction of translation of the mRNA with respect to the fine-structure map . Recombination studies indicated that two of 30 mutants contained deletions of the entire met15 locus . -- It was established that a variety of mutational types, including missense, nonsense, and deletions, are recovered with this unique system in which both forward and reverse mutations can be selected on the basis of methyl mercury resistance and methionine requirement of the met15 mutants.

Can J Genet Cytol, 1975 Sep, 17(3), 395 - 9
Action of "colonie lisse" mutation on cell morphology of Saccharomyces cerevisiae; Bizeau C et al.; The mutation of one of the genes of the series PLi in Saccharomyces cerevisiae Hansen brings about a reduction in the size of the cells . Besides, the mutation of some genes (PLi 5 and PLi 7) induces a change in the scanning microscopy appearance of the cell wall.

Can J Genet Cytol, 1975 Sep, 17(3), 381 - 9
Saccharomyces cerevisiae petite mitochondrial DNA of suppressive and neutral haploids and of {rho-} diploids obtained from crossing {rho+} to a neutral petite; Robertson AJ et al.; An unusual property of GR25a {rho+} was the production of 20 to 30 percent {rho-} zygote colonies when crossed to a tester strain lacking mitochondrial DNA . Spontaneous {rho-} isolates of GR25a {rho+} were observed to be highly suppressive and to contain mitochondrial DNA of a parental buoyant density (1.685 g/cm3) . Three ethidium bromide induced neutral petites of GR25 a {rho+} did not have detectable mitochondrial DNA and were neutral in crosses to {rho+} strains . Seven {rho-} zygote colony isolates obtained from crossing GR25a {rho+} to a neutral peptite were shown to contain abnormal mitochondrial DNA . Six zygote colony isolates had mitochondrial DNA of a buoyant density less than, or equal to, GR25a (1.682 - 1.685 g/cm3), whereas one isolate had a buoyant density greater than GR25a (1.688 g/cm3) . It was suggested that abnormal mitochondrial DNA is generated during the mating reaction.

Prikl Biokhim Mikrobiol, 1975 Sep-Oct, 11(5), 657 - 61
{Production of the methyl ether of 8,14-seco-delta,3,5,(10),9(11)-estratetraendiol-3,17beta-one-14 using a culture of Saccharomyces cerevisiae BKMU-488}; Gulaia VE et al.; The culture Saccharomyces cerevisiae BKMU-499 was selected from 100 strains of different Saccharomyces species to obtain an optically active methyl ester 8,14-seco-delta1,3,5(10),9(11)-estratetraendiol-3-17beta-on-14 . Various conditions of the transformation were examined . The yield of this keto-alcohol depended on the following factors: level of aeration, method of steroid administration, physiological state of the culture, and composition of the cultivation medium . The optimal yeild of the optically active product was 84%.

Eur J Biochem, 1975 Sep 1, 57(1), 231 - 9
The regulation of arginine biosynthesis in Saccharomyces cerevisiae . The specificity of argR- mutations and the general control of amino-acid biosynthesis; Delforge J et al.; The regulation of arginine biosynthetic enzymes in yeast is subjected to a double control . One level of arginine enzyme synthesis is under the control of an apo-repressor, called ARGR . ARGR molecules control specifically the arginine pathway . A second level of control of arginine biosynthesis has been disclosed . It also controls tryptophan, histidine, lysine, isoleucine-valine and probably many more biosyntheses . The general mechanism is turned on in leaky mutants in any of the amino acid pathways mentioned above.

J Bacteriol, 1975 Sep, 123(3), 1144 - 9
Localization of acid phosphatase in protoplasts from Saccharomyces cerevisiae; van Rijn HJ et al.; The localization of acid phosphatase (EC 3.1.3.2) in secreting protoplasts prepared from Saccharomyces cerevisiae is reported for the first time . Using a Gomori technique we were able to show acid phosphatase at those organelles in the protoplasts which are generally involved in the processes of biosynthesis and secretion of glycoproteins in eukaryotic cells.

Mol Gen Genet, 1975 Aug 27, 139(3), 255 - 68
Mutagen specificity in the induction of mitotic crossing-over in Saccharomyces cerevisiae; Zimmermann FK et al.; A diploid yeast strain, D81, was constructed heterozygous for seven recessive markers linked on the left arm of chromosome VII to study the localization of induced mitotic crossing over . The mutagens used were carofur also called nifurprazinum (1-(5-nitro-2-furyl)-2-(6-amino-3-pyridazyl)-ethylene hydrochloride), diepoxybutane, ethylmethanesulfonate, nitrous acid and 1-nitrosoimidazolidinone-2 . All agents induced high frequencies of mitotic crossing over at doses exerting only a low degree of killing . The distribution of recombinational events was compared for five intervals . The distribution pattern of spontaneous mitotic crossing over was different from all the patterns obtained after mutagenic treatments . Nitrous acid and diepoxybutane induced the same pattern, which was different from the patterns induced by carofur, EMS and 1-nitrosoimidazolidinone-2 . The patterns induced by the latter three mutagens were again different amongst each other . Repeat experiments showed that the patterns induced by a given mutagen were reproducible . Tetrad analysis with a representative sample of segregants induced by diepoxybutane and carofur showed that the treatments actually induced mitotic crossing-over . The pattern of meiotic recombinational events was different from those of spontaneous and mutagen induced mitotic recombination . Inducibility of mitotic crossing-over was low at the proximal and distal ends of the chromosome arm and highest in the middle . Each interval showed a different response to those mutagens that differed in their patterns of induced mitotic crossing over . The observed mutagen specific effects are considered as an indication of mutagen specificity . No plausible explanation for mutagen specificity could be given . However, the data presented reveal the same situation as found in induction of chromosome breaks, as reported by other authors . Apparently, mutagen specificity is quite a general phenomenon even for genetic effects in larger intervals of a chromosome.

Eur J Biochem, 1975 Aug 15, 56(2), 533 - 8
Isolation and properties of a thymidylate-less mutant in Saccharomyces cerevisiae; Luzzati M; A mutant, tmp3, has been isolated in Saccharomyces cerevisiae . Genetic and physiological analysis show that a single mendelian gene controls the multiple requirements for thymidylate, methionine, adenine and histidine and a neutral cytoplasmic petite character . Crude extracts of this mutant present a 60% decrease of serine transhydroxymethylase specific activity as compared to a wild-type strain.

Genetics, 1975 Aug, 80(4), 695 - 709
Effects of glucose repression of the transmission and recombination of mitochondrial genes in yeast (Saccharomyces cerevisiae); Birky CW Jr; Matings of a number of Saccharomyces cerevisiae stocks give different output ratios of mitochondrial genotypes depending on whether the cells are glucose-repressed or derepressed . The effects of glucose repression are independent of cellular mating type and mitochondrial genotype, and take place at least in part after zygotes are formed . An explanation is proposed in terms of changes in the relative numbers of mitochondrial DNA molecules contributed by the a and alpha parents, modified by selective replication or destruction of molecules inside the zygote.

Mol Gen Genet, 1975 Aug 5, 139(2), 121 - 32
Methionine biosynthesis in Saccharomyces cerevisiae . I . Genetical analysis of auxotrophic mutants; Masselot M et al.; In order to analyse how many structural genes are implicated in the specific steps of the biosynthesis of methionine in Sacch . cerevisiae, a hundred mutants were studied by complementation . 21 groups were defined named MET1 to MET25 . Neither recombination between independent mutants of the same complementation group nor linkage between different groups was found . Preliminary to biochemical studies, mutants of each complementation group were tested for their capacity to utilize various precursors of methionine.

J Bacteriol, 1975 Aug, 123(2), 637 - 41
Derepression in Saccharomyces cerevisiae can be dissociated from cellular proliferation and deoxyribonucleic acid synthesis; Mahler HR et al.; A method has been developed that permits precise control of release from catabolite repression in Saccharomyces cerevisiae . It consists of transferring cells growing exponentially on 5% glucose to derepression medium at high cell density . Derepression then proceeds with reproducible kinetics and is complete within 6 to 7.5 h for various intra- and extramitochondrial markers, in the absence of any substantial increase in cellular dry weight or protein . Nuclear (and mitochondrial) deoxyribonucleic acid synthesis can be interrupted in certain thermosensitive (cdc) mutants at the nonpermissive temperature; a shift to this temperature before the onset of derepression has no effect on its outcome.

J Bacteriol, 1975 Aug, 123(2), 428 - 35
Methionine-and S-adenosyl methionine-mediated repression in a methionyl-transfer ribonucleic-acid synthetase mutant of Saccharomyces cerevisiae; Cherest H et al.; A Saccharomyces cerevisiae mutant strain unable to grow at 38 C and bearing a modified methionyl-transfer ribonucleic acid (tRNA) synthetase has been studied . It has been shown that, in this mutant, the percentage of tRNAmet charged in vivo paralleled the degree of repressibility of methionine biosynthetic enzymes by exogenous methionine . On the contrary, the repression mediated by exogenous S-adenosylmethionine does not correlate with complete acylation of tRNAmet . Althought McLaughlin and Hartwell reported previously that the thermosensitivity and the defect in the methionyl-tRNA synthetase were due to the same genetic lesion (1969), no diffenence could be found in the methionyl-tRNA synthetase activity or in the pattern of repressibility of methionine biosynthetic pathway after growth at the premissive and at a semipermissive temperature . It appears that the mutant also exhibits some other modified characters that render unlikely the existence of only one genetic lesion in this strain . A genetic study of this mutant was undertaken which led to the conclusion that the thermosensitivity and the other defects are not related to the methionyl-tRNA synthetase modification . It was shown that the modified repressibility of methionine biosynthetic enzymes by methionine and the lack of acylation of tRNAmet in vivo follow the methionyl-tRNA synthetase modification . These results are in favor of the idea that methionyl-tRNAmet, more likely than methionine, is implicated in the regulation of the biosynthesis of methionine.

Cell, 1975 Aug, 5(4), 423 - 8
Mitochondrial DNA synthesis in cell cycle mutants of Saccharomyces cerevisiae; Newlon CS et al.; Mitochondrial DNA replication was examined in mutants for seven different Saccharomyces cerevisiae genes which are essential for nuclear DNA replication . In cdc8 and cdc21, mutants defective in continued replication during the S phase of the cell cycle, mitochondrial DNA replication ceases at the nonpermissive temperature . Replication is temperature sensitive even when these mutants are arrested in the G1 phase of the cell cycle with alpha factor, a condition where mitochondrial DNA replication continues for the equivalent of several generations at the permissive temperature . Therefore the cessation of replication results from a defect in mitochondrial replication per se, rather than from an indirect consequence of cells being blocked in a phase of the cell cycle where mitochondrial DNA is not normally synthesized . Since the temperature-sensitive mutations are recessive, the products of genes cdc8 and cdc21 must be required for both nuclear and mitochondrial DNA replication . In contrast to cdc8 and cdc21, mitochondrial DNA replication continues for a long time at the nonpermissive temperature in five other cell division cycle mutants in which nuclear DNA synthesis ceases within one cell cycle: cdc4, cdc7, and cdc28, which are defective in the initiation of nuclear DNA synthesis, and cdc14 and cdc23, which are defective in nuclear division . The products of these genes, therefore, are apparently not required for the initiation of mitochondrial DNA replication.

J Bacteriol, 1975 Aug, 123(2), 616 - 9
Genetic control of yeast mannan structure: mapping genes mnn2 and mnn4 in Saccharomyces cerevisiae; Ballou DL; Two mutations concerned with mannan biosynthesis in the yeast Saccharomyces cerevisiae have been mapping . The mnn2 mutation, which affects the addition to the polysaccharide backbone of the first side-chain D-mannose unit in alpha1-leads to2 linkage, was located on chromosome II linked to the centromere and the gall locus . The mn4 locus, which regulates the synthesis of mannosylphosphate groups on the mannan side chains, was placed on chromosome XI near trp3 and ural and a locus previously reported to regulate the ability of a S . diastaticus strain to bind alcian blue (Friis and Ottolenghi, 1970) . The mnn4 mutant also fails to bind alcain blue, but the gene responsible for alcian blud binding in this strain segregates independently from the dye-binding locus of S . diastaticus, and therefore must be a different gene . A diploid heterozygous for mnn4 fails to bind dye, indicating dominance of this mutant genotype . The alcian blue dye binding locus dbll, reported to Friis and Ottolenghi (1970), is also dominant . Thus, there are at least two independent genes that control the formation of the mannosylphosphate units in the mannan side chains, and both have the property of dominance in the mutant form.

J Bacteriol, 1975 Aug, 123(2), 516 - 22
Specificity and genetics of S-adenosylmethionine transport in Saccharomyces cerevisiae; Petrotta-Simpson TF et al.; The specificity of a transport system for S-adenosylmethionine was determined through the use of structurally related derivatives . Of the compounds tested, the analogues S-adenosylethionine and S-inosylmethionine and the naturally occurring compounds S-adenosyl-(5')-3-methylthiopropylamine and S-adenosylhomocysteine competitively inhibited uptake of the sulfonium compound . Ki values for these compounds indicate that the order of affinity for the transport protein is S-adenosylmethionine congruent to S-adenosyl-(5')-3-methyl-thiopropylamine greater than S-adenosylethionine greater than S-inosylmethionine greater than S-adenosylhomocysteins . S-adenosyl-(2-hydroxy-4-methylthio)butyric acid exerted inhibition of a mixed type . S-insoyl-(2-hydroxy-4-methylthio)butyric acid, S-inosylhomocysteine, and S-ribosylhomocysteine were without effect . On the basis of the inhibition data, the methionine-amino, adenine-amino, and methyl groups were identified as group important in the binding of S-adenosylmethionine to the transport protein . Comparison is made with the specificities of various transmethylating enzymes utilizing S-adenosylmethionine . In addition, a number of conventional and temperature-sensitive S-adenosylmethionine transport mutants were isolated and analyzed in an attempt to identify the structural character of the specific transport protein(s) . The data obtained suggest that only a single gene (a single polypeptide) is involved in specific S-adenosylmethionine transport . Apparent interallelic complementation supports the assumption that the functional form of the protein is composed of two or more copies of a monomer.

J Bacteriol, 1975 Aug, 123(2), 497 - 504
Nuclear and mitochondrial deoxyribonucleic acid replication during mitosis in Saccharomyces cerevisiae; Sena EP et al.; To study nuclear and mitochondrial deoxyribonucleic acid (DNA) synthesis during the cell cycle, a 15N-labeled log-phase population of Saccharomyces cervisiae was shifted to 14N medium . After one-half generation, the cells were centrifuged on a sorbitol gradient in a zonal rotor to fractionate the population according to cell size and age into fractions representing the yeast cell cycle . DNA samples isolated from the zonal rotor cell samples were centrifuged to equilibrium in CsC1 in an analytical ultracentrifuge to separate the nuclear and mitochondrial DNA components . The amount of 14N incorporated into each 15N-labeled DNA species was measured . The extent of nuclear DNA replication per sample was obtained by measuring the amount of hybrid DNA . The percentage of hybrid nuclear DNA increased from 6 to 68% and then decreased to 44% during the cell cycle . Upon ultracentrifugation, mitochondrial DNA banded as a unimodal peak in all zonal rotor samples . Mitochondrial DNA replication could be ascertained only by the 14N level in each mitochondrial peak and not, as with nuclear DNA, by hybrid DNA level . In contrast to the nuclear incorporation pattern, the 14N percentage in mitochondrial DNA remained effectively constant during the cell cycle . Comparison of the data to theoretical distributions showed that nuclear DNA was replicated discontinuously during the cell cycle, whereas mitochondrial DNA was replicated continuously throughout the entire mitotic cycle.

J Biol Chem, 1975 Jul 25, 250(14), 5640 - 6
Polyadenylate metabolism in the nuclei and cytoplasm of Saccharomyces cerevisiae; Groner B et al.; A procedure has been designed for the simultaneous isolation, in a single step, of the nuclei and cytoplasm of Saccharomyces cerevisiae alphas288c spheroplasts . We have examined the polyadenylate poly(A)-containing RNA in these fractions and their kinetics of synthesis . Nuclear RNA saturates with {3H} adenine within 10 min . Labeled RNA appears very quickly in the cytoplasm, exceeding the amount of labeled nuclear RNA within 2 min after the addition of {3H} adenine . Nuclear poly(A)-containing RNA is approximately 10% of the total cellular poly(A)-containing RNA obtained from spheroplasts labeled for 15 min . Nuclear poly(A)-containing RNA is not as large as the giant heterogeneous nuclear RNA of animal cells . The distribution of molecular size in nuclear and cytoplasmic populations of poly(A)-containing RNA is very broad with the average size of the nuclear species being moderately larger than the cytoplasmic species . Three distinct size classes of poly(A), with different apparent kinetic properties, are obtained from yeast poly(A)-containing RNA . Their electrophoretic mobility suggests molecular lengths of approximately 20, 40, and 60 nucleotides (Groner, G., Hynes, N., and Phillips, S . (1975) Biochemistry, 13, 5378-5383) . Each of these poly(A) classes are present in the mRNA from large and small polyribosomes.

Mol Biol Rep, 1975 Jul, 2(2), 101 - 6
Evidence for a functional association of DNA synthesis with the membrane in mitochondria of Saccharomyces cerevisiae; Hall RM et al.; We have studied the effect of membrane fatty acid composition on replicative DNA synthetic activity in mitochondria isolated from Saccharomyces cerevisiae . Cells containing different levels of membrane unsaturated fatty acids were obtained by growth of a fatty acid desaturase mutant of Saccharomyces cerevisiae in glucose-limited chemostat cultures supplemented with various concentrations of Tween 80 . Arrhenius plots of DNA synthetic activity in isolated mitochondria show a discrete discontinuity at specific temperature which are dependent on the membrane unsaturated fatty acid content of the mitochondria . This indicates a functional association of DNA replication with the mitochondrial membrane in Saccharomyces cerevisiae.

Nucleic Acids Res, 1975 Jul, 2(7), 1023 - 42
Studies on deoxyribonucleases from Saccharomyces cerevisiae . Characterization of two endonuclease activities with a preference for double-stranded DNA; Pinon R et al.; Two new endonuclease activities, endonuclease B and endonuclease C, obtained from yeast nuclear preparations have been separated and partially characterized . Endonuclease B has a primary requirement for Mn2+ which cannot be replaced by Mg2+ or Ca2+, and makes single-strand scissions in double-stranded DNA . Endonculease C is activated by either Mn2+ or Mg2+, and makes single-strand scissions with Mg2+, while with Mn2+, scissions are made which result in double-strand breaks . Neither enzyme is active on denatured DNA, and both are inhibited by yeast RNA . Both enzymes exhibit pH optima at pH 5.0 and PH 7.2, and leave 5'-phosphoryl termini.

Arch Microbiol, 1975 Jun 20, 104(1), 23 - 8
Dependence of the maximum temperature for growth of Saccharomyces cerevisiae on nutrient concentration; Van Uden N et al.; Saccharomyces cerevisae was grown in a chemostat under glucose limitation at three superoptimal temperatures . In each steady state the specific growth rate was the sum of the dilution rate and the specific death rate, exponential death occurring with exponential growth . The specific death rate was a function of both the temperature and the concentration of the limiting nutrient . Each superoptimal temperature was characterized by a critical glucose concentration below which net growth was not possible . The critical glucose concentration increased with the temperature . Consequently the maximum temperature for growth was a function of the concentration of the limiting nutrient and approached the optimum temperature for growth with decreasing glucose concentrations.

Biochim Biophys Acta, 1975 Jun 17, 387(3), 451 - 60
Two mechanisms of near-ultraviolet lethality in Saccharomyces cerevisiae: a respiratory capacity-dependent and an irreversible inactivation; Fong F et al.; Near-ultraviolet irradiation of actively growing yeast cells leads to cell death by two distinct mechanisms . The first type of cell death is evident after low doses of near-ultraviolet light (3 times 10-4 ergs times mm- minus 2) and is due to a reversible inactivation of the respiratory capacity of the cell . In studies with yeast mitochondrial membranes the quinones were identified as the site of inactivation by determining the relative levels of the following oxidase activities after irradiation: exogenous NADH, endogenous NADH (via isocitrate dehydrogenase), succinate, and D-lactate oxidases . A second type of cell death is caused after high doses (1.8 times 10-5 ergs times mm- minus 2) and is irreversible . The mechanism of this inactivation is unknown.

Biochim Biophys Acta, 1975 Jun 17, 387(3), 441 - 50
EPR studies on the respiratory chain of wild-type Saccharomyces cerevisiae and mutants with a deficiency in succinate dehydrogenase; Kok J DE et al.; 1 . Three nuclear mutants of Saccharomyces cerevisiae deficient in succinate dehydrogenase have been isolated . Two of these mutants are allelic . 2 . The amount of covalently bound flavin of submitochondrial particles of the two allelic mutants is about 14% and that of the third mutant about 50% of the amount in wild-type particles . The turnover number of succinate dehydrogenase of particles is decreased in all mutants . The turnover number of fumarate reductase is increased in the two allelic mutants, but decreased in the third mutant . 3 . EPR spectra, measured at 82 degrees K, show that the amplitude of the g equals 1.93 signal in particles of the two allelic mutants is less than 10% of that in wild-type particles . It is concluded that iron-sulphur centres other than those of succinate dehydrogenase make only a negligible contribution to the line at g equals 1.93 in wild-type particles . 4 . EPR measurements below 20 degrees K show that the amplitude of the signal at g equals 2.01 detected in oxidized particles is decreased in particles of the two allelic mutants . 5 . A signal with lines at g equals 2.027 and g equals 1.933 is detected at low temperatures in all particle preparations, even in those from a cytoplasmic petite mutant . It is suggested that this signal is derived from a contaminant and not from the inner membrane.

J Biol Chem, 1975 Jun 10, 250(11), 4087 - 94
Cytochrome synthesis in synchronous cultures of the yeast, Saccharomyces cerevisiae; Cottrell SF et al.; The synthesis of cytochromes aa3, b, and c has been investigated during synchronous growth in the yeast, Saccharomyces cerevisiae . These cytochromes increase in concentration continuously throughout each cell cycle, with an approximate doubling in rate during successive cycles . The rates of cytochrome formation are considerably higher in galactose-grown cultures than in cells grown in glucose . Although cytochrome aa3 increases at a continuous rate, its functional counterpart, cytochrome c oxidase, increases in stepwise fashion, with the increments occurring at the beginning of each new cell cycle . Chloramphenicol, a specific inhibitor of intramitochondrial protein synthesis, inhibits the formation of cytochrome aa3 at all stages of the cell cycle, but does not inhibit cytochrome c . Chloramphenicol exhibits a somewhat intermediate effect on cytochrome b synthesis, with transient inhibition occurring only when the drug is added prior to or during the initial part of the first cell cycle . After this time, chloramphenicol had no effect on the rate of cytochrome b synthesis . The data indicate that under our conditions of cell synchrony mitochondrial membrane formation as reflected by increments in mitochondrial cytochromes occurs by continuous accretion of new material throughout the cell cycle . Intramitochondrially synthesized polypeptide products, responsible for the formation of new cytochrome aa3, appear to be synthesized throughout the cell cycle.

Hoppe Seylers Z Physiol Chem, 1975 Jun, 356(6), 767 - 76
A naturally occurring Cu-thionein in Saccharomyces cerevisiae; Prinz R et al.; A naturally occurring monodisperse Cu-thionein was prepared using ammonium sulfate precipitation followed by ion exchange (DEAE 23) and gel chromatography (Sephadex G-75) . The chromatographic steps were repeated at least twice, or until the Cu-thionein remained homogeneous when subjected to analytical polyacrylamide disc electrophoresis . The molecular weight of this copper protein was 9500+/-500 . Up to 24.3% cysteine residues were determined, indicating the relationship to the metallothioneins . Aromatic amino acids were virtually absent, while there were about three times as many acidic amino acid residues, including aspartate and glutamate, as in metallothioneins . 10 g atoms of Cu were measured per mole of protein . The copper binding strength of thionein was extremely high . Displacement by protons (pH 1.5) and gel chromatography or dialysis employing EDTA were not effective . Dialysis against diethyldithiocarbamate produced a protein essentially free of copper . Both the ultraviolet properties and the circular dichroism measurements proved identical with those properties reported for artificially prepared Cu-thionein (see ref.{1} . The major absorption was in the far ultraviolet region with a weak shoulder at 270 nm attributable to copper charge-transfer transititions . 6 Cotton extrema were seen at 213, 283 and 302 nm (negative) and 245, 328 and 359 nm (positive) . The possible role of Cu-thionein as an electron transport system was discussed.

Eur J Biochem, 1975 Jun, 54(2), 459 - 67
Mechanism of 2-deoxy-D-glucose inhibition of cell-wall polysaccharide and glycoprotein biosyntheses in Saccharomyces cerevisiae; Kratky Z et al.; The mechanism of inhibition by 2-deoxy-D-glucose of the synthesis of yeast wall polysaccharides and glycoproteins was investigated in Saccharomyces cerevisiae cells and protoplasts . The extent of the inhibition of mannan and glucan synthesis was found to be dependent on whether glucose or mannose was used as the carbon source in the medium . During growth on glucose, 2-deoxy-D-glucose inhibited more intensively mannan than glucan formation . Biosynthesis of wall glucan was strongly suppressed in mannose medium . Selective incorporation of 2-deoxy-D-glucose occurred into that polysaccharide, synthesis of which was more inhibited under given conditions . Suggestive evidence has been obtained that the decisive factor for the proportion of glucan and mannan in the walls is the direction of glucose 6-phosphate/mannose 6-phosphate interconversion dependent on the exogeneous hexose . No close correlation was found between the inhibition of mannan synthesis and the appearance of the mannan-protein enzymes invertase and acid phosphatase . Effect of 2-deoxy-D-glucose was therefore investigated on the parallel synthesis of protein, mannan and several extracellular and intracellular enzymes in protoplasts grown on glucose and mannose . The results obtained pointed out that the hindrance of the secretion of mannan-protein enzymes is of a complex nature and related more to the inhibition of synthesis of the protein moiety than to the inhibition of glycosylation . Synthesis of several enzymes was found to be a subject of a metabolic control by 2-deoxy-D-glucose or its metabolites.

J Bacteriol, 1975 Jun, 122(3), 911 - 22
Isolation and characterization of recessive, constitutive mutations for repressible acid phosphatase synthesis in Saccharomyces cerevisiae; Ueda Y et al.; Two new classes of mutants containing recessive constitutive mutations, phoT and phoU, that affect the repressible acid phosphatase (EC 3.1.3.2) in Saccharomyces cerevisiae were isolated along with many previously known phoR mutants . These loci segregated independently from each other, from the phoS gene, and from another regulatory gene, phoD, that exerts positive control for acid phosphatase synthesis . The phoR and phoU mutations showed the same genetic behavior in the double mutants, which also contained the phoS or phoD mutation . In contrast, the phoT mutation could not suppress the phoS mutation, which caused a loss of enzyme activity . Many mutant alleles of phoR and phoU were found to be temperature sensitive (ts), whereas those of phoT were not . These ts mutants were constitutive at 35 C but severely repressible at 25 C . These facts strongly suggest that both the phoR and phoU genes are cooperatively concerned with the production of the repressor, whereas the phoT gene might be involved in another mechanism distinct from that in which phoR and phoU are involved . No single mutation of phoR, phoT, or phoU result in an enzyme level comparable to that of fully derepressed enzyme activities, and the temperature sensitivity of the ts phoR and ts phoU mutations in such combinations almost disappeared . In addition to these observations, since the ts phoR phoS and ts phoU phoS double mutants showed some enzyme synthesis at 25 C under derepressing conditions, a defect in the ts mutant repressors was strongly suggested, even at 25 C.

J Bacteriol, 1975 Jun, 122(3), 847 - 54
Dominant and semidominant mutations leading to thermosensitivity of ribonucleic acid biosynthesis in Saccharomyces cerevisiae; Lacroute F et al.; Different dominant thermosensitive mutations affecting the same gene were selected in Saccharomyces cerevisiae . Ribonucleic acid (RNA) synthesis decreased rapidly and markedly at 37 C in all the mutants whether they were in a homozygous or a heterozygous state . Protein biosynthesis was at first unaffected and then decreased slowly, stopping after 5 h . Measurements of RNA biosynthesis in isolated nuclei as well as in vitro activities of RNA polymerases A and B at 22 and 37 C failed to reveal any difference between mutants and the wild type . Analysis of the nature of the residual RNAs synthesized at the high temperature in the mutants showed a small relative increase in the messenger RNA fraction, but it was not sufficient to indicate a specific inactivation of RNA polymerase A activity . The results suggest an impairment in a common regulatory element for all RNA polymerases acting at the level of the initiation of transcription . Similar mutants with a semidominant phenotype were obtained in which the lesions were in two other unlinked loci.

Can J Microbiol, 1975 Jun, 21(6), 802 - 6
A new method of obtaining zygotes in Saccharomyces cerevisiae; Lee EH et al.; Experiments leading to a simple method of mass zygote formation in Saccharomyces cerevisiae are described . This method ordinarily requires only about 3 h of incubation, and consistently yielded 55-65% zygotes in seven different crosses among six different strains . Matings involving one strain required about 4 h of incubation but otherwise the results were comparable.

Nucleic Acids Res, 1975 Jun, 2(6), 831 - 8
Number of genes and base composition of mitochondrial tRNA from Saccharomyces cerevisiae; Schneller JM et al.; Increasing amounts of mitochondrial {32P} tRNA (4S fraction), were hybridized with mitochondrial DNA OF Saccharomyces cerevisiae . At saturation, the calculated number of genes for 4S mitochondrial RNA was 20 . Mitochondrial {32P} tRNA eluted from the hydrids obtained either with an excess of tRNA or an excess of DNA showed, after alkaline hydrolysis and chromatography, a G+C content of 28 and 35 p . cent respectively . This last value is similar to that found with the total 4S fraction . The odd nucleotides T (about 1T per sequence), U, hU are present in mitochondrial tRNA . Some sequence may begin with pG.

J Bacteriol, 1975 Jun, 122(3), 826 - 31
Assembly of the mitochondrial membrane system: isolation of nuclear and cytoplasmic mutants of Saccharomyces cerevisiae with specific defects in mitochondrial functions; Tzagoloff A et al.; A selection procedure is described which permits a large number of Saccharomyces cerevisiae mutants to be screened for specific lesions in mitochondrial respiratory enzymes and the adenosine triphosphatase . The method has been used to isolate nuclear mutant strains with specific lesions in coenzyme QH2-cytochrome c reductase, cytochrome oxidase, and adenosine triphosphatase . In addition, two cytoplasmic mutants have been found whose primary defect is in cytochrome oxidase, and others have been found that show variable degrees of abnormalities in their mitochondrial translation products.

Proc Natl Acad Sci U S A, 1975 Jun, 72(6), 2054 - 7
Properties of cytoplasmic mutants of Saccharomyces cerevisiae with specific lesions in cytochrome oxidase; Tzagoloff A et al.; Two mutants with specific defects in cytochrome c oxidase (ferrocytochrome c:oxygen oxidoreductase; EC 1.9.3.1) have been isolated from cultures of Saccharomyces cerevisiae exposed to the mutagens ethyl-methane sulfonate and Mn++ . The mutations have been shown to be extranuclear by two criteria . The phenotype persists in diploids formed by a cross with a p-o strain of yeast of the opposite mating type . Tetrad analysis indicates a non-Mendelian segregation (4:0 and 0:4) of the mutations . Both mutants show a total absence of cytochrome oxidase activity and of spectral cytochromes a and as . One of the mutants has been shown to be missing a polypeptide synthesized by mitochondria . The migration of this protein on polyacrylamide gels corresponds to the highest-molecular-weight subunit of cytochrome oxidase.

Genetics, 1975 May, 80(1), 23 - 40
Inositol-requiring mutants of Saccharomyces cerevisiae; Culbertson MR et al.; Fifty-two inositol-requiring mutants of Saccharomyces cerevisiae were isolated following mutagenesis with ethyl methanesulfonate . Complementation and tetrad analysis revealed ten major complementation classes, representing ten independently segregating loci (designated ino1 through ino10) which recombined freely with their respective centromeres . Members of any given complementation class segregated as alleles of a single locus . Thirteen complementation subclasses were identified among thirty-six mutants which behaved as alleles of the ino1 locus . The complementation map for these mutants was circular . - Dramatic cell viability losses indicative of unbalanced growth were observed in liquid cultures of representative mutants under conditions of inositol starvation . Investigation of the timing, kinetics, and extent of cell death revealed that losses in cell viability in the range of 2-4 log orders could be prevented by the addition of inositol to the medium or by disruption of protein synthesis with cycloheximide . Mutants defective in nine of the ten loci identified in this study displayed these unusual characteristics . The results suggest an important physiological role for inositol that may be related to its cellular localization and function in membrane phospholipids . The possibility is discussed that inositol deficiency initiates the process of unbalanced growth leading to cell death through the loss of normal assembly, function, or integrity of biomembranes . - Part of this work has been reported in preliminary form (CULBERTSON and HENRY 1974).

J Bacteriol, 1975 May, 122(2), 375 - 84
Biochemical and regulatory effects of methionine analogues in Saccharomyces cerevisiae; Colombani F et al.; The effect of three methionine analogues, ethionine, selenomethionine, and trifluoromethionine, on the biosynthesis of methionine in Saccharomyces cerevisiae has been investigated . We have found the following to be true . (i) A sharp decrease in the endogenous methionine concentration occurs after the addition of any one of these analogues to growing cells . (ii) All of them can be transferred to methionine transfer ribonucleic acid in vitro as well as in vivo with, as a consequence, their incorporation into proteins . In the absence of radioactive trifluoromethionine, this conclusion results from experiments of an indirect nature and must be taken as an indication rather than a direct demonstration . (iii) Ethionine and selenomethionine can be activated as homologues of S-adenosylmethionine, whereas trifluoromethionine cannot . (iv) All of them can act as repressors of the methionine biosynthetic pathway . This has been shown by measuring the de novo rate of synthesis of methionine in a culture grown in the presence of any one of the three analogues.

J Bacteriol, 1975 May, 122(2), 359 - 66
Reduced plasma membrane permeability in a multiple cross-resistant strain of Saccharomyces cerevisiae; Rank GH et al.; Single nuclear gene inheritance was shown to be responsible for increased resistance to: eight diverse inhibitors of mitochondrial function (antimycin, carbonylcyanide-m-chlorophenylhydrazone, chloramphenicol, oligomycin, tetracycline, triethyltin bromide, triphenylmethylphosphonium bromide and triton-X-165); and an inhibitor of cytoplasmic protein synthesis (cycloheximide) . Continuous monitoring of oxygen uptake during respiratory adaptation showed that anerobic pretreatment of resistant cells sensitized respiratory adaptation to chloramphenicol and antimycin . However, since a depression of mitochondrial function by catabolite repression did not result in sensitization to antimycin, alteration of the mitochondrial membrane does not appear to be responsible for resistance to mitochondrial inhibition . Alteration of cellular binding sites was not responsible for resistance since in vitro mitochondrial protein synthesis was sensitive to chloramphenicol and in vitro mitochondrial respiration was sensitive to oligomycin, carbonylcyanide-m-chlorophenylhydrazone, and antimycin . Autoradiography of an ethylacetate-ethanol extract of {14C}chloramphenicol-treated resistant cells indicated that resistance was not due to enzymatic modification of inhibitors . The maintenance of an antimycin-resistant respiration by protoplasts of resistant cells ruled out the involvement of the cell wall in cellular resistance . The reduced transport of {14C}chloramphenicol by resistant cells (1% of normal cells) indicated that a single nuclear gene mutation can alter the permeability of the plasma membrane to many diverse inhibitors.

J Bacteriol, 1975 May, 122(2), 629 - 41
Characterization of cytosine permeation in Saccharomyces cerevisiae; Chevallier MR et al.; Cytosine permeation in Saccharomyces cerevisiae has been studied . Cytosine uptake is mediated by a permease which is also responsible for purines transport . The Km for the transport of various substrates of this permease have been determined . By means of appropriate selective techniques, mutants with altered Km and mutants lacking the permease have been selected . Cytosine transport is active and is inhibited by 2,4-dinitrophenol, an uncoupler of oxidative phosphorylation, and by N-ethylmaleimide, a reagent of--SH group . Internal labeled cytosine is chased by addition of unlabeled cytosine in the medium . These results support the hypothesis of a carrier-mediated transport, with reduced internal affinity, allowing the release and accumulation of cytosine in the inner compartment . The efflux of cytosine from cytosine permease-less cells has also been studied and shows first order kinetics . A diffusion coefficient of 5.7 per 10- minus 8 cm per S- minus 1 has been evaluated for this efflux.

C R Acad Sci Hebd Seances Acad Sci D, 1975 Apr 28, 280(16), 1903 - 6
{The polyphosphate synthetase of Saccharomyces cerevisiae}; Felter MS et al.; The polyphosphate-synthetase, isolated from a homogenate of phosphate starved cells, catalyses the synthesis of linear polyphosphates from orthophosphate . It is localized in the membrane fraction which deposits between 400 and 1000 X g; its optimal pH is 7.1; its KM toward orthophosphate is 4.0 X 10(-4) M; ATP stimulates the reaction . The enzyme synthezises especially polyphosphates with short chain length.

C R Acad Sci Hebd Seances Acad Sci D, 1975 Apr 7, 280(13), 1559 - 62
{Evolution of cytoplasmic tRNAphe in a haploid strain of Saccharomyces cerevisiae}; Seigle-Murandi F et al.; The fluorescent modified Y nucleoside of phe-t-RNA has been evaluated during the development of a haploid of yeast . Free Y nucleoside has been found in the cells during the growing logarithmic phase . It seems that the evolution of this compound is probably concerned with cellular division processes.

Mutat Res, 1975 Apr, 31(2), 71 - 86
Procedures used in the induction of mitotic recombination and mutation in the yeast Saccharomyces cerevisiae; Zimmermann FK; Techniques are described for the use of various yeast strains to detect the induction of (1) mitotic crossing-over, (2) mitotic gene conversion, (3) forward mutation and (4) reverse mutation . The technique for the detection of mitotic crossing over is based on a diploid that carries two different alleles of the gene locus ade2 . These alleles differ in their extent of colony pigmentation engendered on low-adenine media, and they complement each other to the effect that the diploid is white . Mitotic crossing over results in the formation of twin-sectored colonies with a red and a pink sector . The technique for the detection of mitotic gene conversion is based on the use of a heteroallelic diploid carrying two non-complementing alleles that cause a nutritional requirement . Mitotic gene conversion leads to the restoration of intact and dominant wild-type alleles that alleviate the nutritional requirement so that convertant cells can be selected on a minimal medium . The forward mutation technique is based on the use of a haploid strain with a defect in the ade2-gene locus which causes the formation of red colonies . Induction of forward mutation in a number of other loci prevents the accumulation of this red pigment so that induction of mutation can be detected by the formation of pink and white colonies . The reverse mutation technique is based on the restoration or compensation of a mutational defect causing a growth requirement . Mutants can be selected for on a minimal medium.

J Biol Chem, 1975 Mar 25, 250(6), 2003 - 7
Small ribonucleic acid molecules produced during ribosome biosynthesis in Saccharomyces cerevisiae; Helser TL et al.; A 5.8 S ribosomal RNA (rRNA) is found noncovalently bound to the 25 S RNA in the 60 S subunit of yeast ribosomes . Both molecules appear to be derived from the 27 S RNA, a ribosomal precursor species (Uden, S . A., and Warner, J . R . (1972) J . Mol . biol . 65, 227-242) . We have detected two other RNA species by pulse labeling which may also be produced during 27 S RNA processing . The first is approximately 5.9 S and appears by kinetics of synthesis to be a direct precursor of 5.8 S rRNA . The second species is about 7 S, is absent from uniformly labeled RNA preparations, and is produced coincidentally with the 5.8 S rRNA . Both the 5.9 S RNA and the 7 S RNA are not produced in mutants defective in ribosome biosynthesis (Hartwell, L . H., McLaughlin, C . S., and Warner, J . R . (1970) Mol . Gen . Genet . 109, 42-56) which are unable to make the 25 S-5.8 S rRNA complex from 27 S RNA . Thus, the maturation of 27 S RNA appears to involve the production of a 7 S RNA, which could be either a precursor or a nonconserved RNA region, and a 5.9 S RNA, most of which is trimmed to give the mature 5.8 S rRNA in the 25 S-5.8 S rRNA complex of 60 S subunits.

J Bacteriol, 1975 Mar, 121(3), 975 - 82
Adenylate energy charge in Saccharomyces cerevisiae during starvation; Ball WJ Jr et al.; Bakers' yeast cells, Saccharomyces cerevisiae, if grown aerobically on ethanol or if grown aerobically on glucose and allowed to pass into stationary phase, with utilization of accumulated ethanol, maintain a normal value (0.8 to 0.9) of the adenylate energy charge during prolonged starvation . In contrast, cells grown anaerobically on glucose and cells in the early stages of aerobic growth on glucose exhibit a rapid decrease of energy charge if transferred to medium lacking on energy source . These results suggest that functional mitochondria or enzymes of balance of adenine nucleotides during starvation . Yeast cells remain viable at energy charge values below 0.1, in marked contrast to results previously obtained with Escherichia coli . In other respects, the engery charge responses of yeast to starvation and refeeding are generally similar to those previously reported for E . coli.

Biochemistry, 1975 Mar 11, 14(5), 1038 - 46
Translation of poly(riboadenylic acid)-enriched messenger RNAs from the yeast, Saccharomyces cerevisiae, in heterologous cell-free systems; Gallis BM et al.; Poly(riboadenylic acid) {poly(A)} enriched messenger RNAs from yeast have been used to direct the synthesis of yeast polypeptides in mouse Krebs II ascites and wheat embryo extracts . Both cell-free systems, synthesize polypeptides over a molecular weight range of 10,000-100,000 . Autoradiograms of sodium dodecyl sulfate-polyacrylamide slab gels used to fractionate {35S}methionine-labeled in vitro products reveal that about 25 major bands (each of them possibly representing multiple polypeptides) are produced by each cell-free system . Each of these coelectrophoreses with a major polypeptide labeled in vivo or in a yeast lysate . These results suggest that cell-free translational machinery from eukaryotes is not able to discriminate in an all or none fashion against messenger RNAs which are available to it . While yeast poly(A)-enriched messenger RNA directs the synthesis polypeptides over approximately the same molecular weight range in both cell-free systems, the wheat germ system directs the incorporation of 45 times the amount of {3H}serine into Cl3CCOOH-precipitable polypeptides . This is in contrast to the 2.5-fold more efficient translation of hemoglobin mRNA in the wheat embryo extract . Thus, the extract from mammalian cells is able to translate mRNA from a lower plant with a much lower efficiency than it translates hemoglobin mRNA, and at a lower efficiency than is observed using a cell-free system from wheat embryos . This indicates that the wheat embryo system is the one of choice for translation of yeast messenger RNA.

Arch Microbiol, 1975 Mar 10, 102(3), 247 - 51
Biosynthesis of sulphur amoni acids in Saccharomyces cerevisiae . I . Genetic analysis of leaky mutants of sulphite reductase; Zambonelli C et al.; The hypothesis of an alternative pathway of sulphur amino acid synthesis as the basis of the prototrophy of sulphite reductase negative (Sr--) strains of Saccharomyces cerevisiae has been rejected . Met- mutants obtained after phenylmercuric nitrate treatment of Sr- strains accumulate H2S as the consequence of a metabolic block which leads to methionine auxotrophy . This mutation has been shown to be independent of the Sr locus . We assume that the molecular basis of the prototrophy of Sr- mutant resides in a leaky missense induced in the Sr gene.

Proc Natl Acad Sci U S A, 1975 Mar, 72(3), 794 - 8
The relationship between enzyme activity, cell geometry, and fitness in Saccharomyces cerevisiae; Weiss RL et al.; The relationship between enzyme activity, cell geometry, and the ploidy levels has been investigated in Saccharomyces cerevisiae . Diploid cells have 1.57 times the volume of haploid cells under nonlimiting growth conditions (minimal medium) . However, when diploid cells are grown under conditions of carbon limitation, they have the same volume as haploid cells . Thus, by altering the environmental conditions, cell size can be varied independently of the degree of ploidy . The results indicate that the basic biochemical parameters of the cell are primarily determined by cell geometry rather than ploidy level . RNA content, protein content, and ornithine transcarbamylase (carbamoylphosphate: L-ornithine carbamoyltransferase, EC 2.1.3.3), tryptophan synthetase {L-serine hydro-lyase (adding indole), EC 4.2.1.20}, and invertase (alpha-D-glucoside glucohydrolase, Ec 3.2.1.20) activity are related to cell volume, whereas acid phosphatase (orthophosphoric-monoester phosphohydrolase, EC 3.1.3.2) activity, a cell surface enzyme, is related to the surface area of the cells . Fitness is determined by the activity of certain cell surface enzymes, such as acid phosphatase, diploids would be expected to have a lower fitness than haploids because of the lower surface area/volume ratio . However, when fitness is determined by the activity of an internal enzyme, diploids would be expected to have the same fitness as haploids . Results from competition experiments between haploids and diploids are consistent with these predictions . The significance of these results to the evolution of diploidy as the predominant phase of the life cycle of higher plants and animals is discussed.

Genetics, 1975 Mar, 79(3), 383 - 96
Mitotic chromosome loss in a disomic haploid of Saccharomyces cerevisiae; Campbell DA et al.; Experiments designed to characterize the incidence of mitotic chromosome loss in a yeast disomic haploid were performed; The selective methods employed utulize the non-mating property of strains disomic for linkage group III and heterozygous at the mating type locus . The principal findings are: (1) The grequency of spontaneous chromosome loss in the disome is of the order 10- minus 4 per cell; this value approximates the frequency in the same population of spontaneous mitotic exchange resulting in homozygosity at the mating type locus . (2) The recovered diploids are pure clones, and thus represent unique events in the disomic haploid . (3) Of the euploid chromosomes recovered after events leading to chromosome loss, approximately 90% retain the parental marker configuration expected from segregation alone; however, the remainder are recombinant for marker genes, and are the result of mitotic exchanges in the disome, especially in regions near the centromere . The recombinant proportion significantly exceeds that expected if chromosome loss and mitotic exchange in the disome were independent events . The data are consistent with a model proposing mitotic nondisjunction as the event responsible for chromosome loss in the disomic haploid.

J Bacteriol, 1975 Mar, 121(3), 901 - 6
Dose dependence of the excision of ultraviolet-induced pyrimidine dimers from nuclear deoxyribonucleic acids of haploid and diploid Saccharomyces cerevisiae; Waters R et al.; The yield of ultraviolet-induced dimers is similar for a fixed dose in both haploid and diploid Saccharomyces cerevisiae . The excision of these photo-products from the nuclear deoxyribonucleic acids of cells of both ploidies after ultraviolet incident doses of 2 times 10-3 to 4 times 10-3 ergs/mm2 decreased with the corresponding increasing dose . Postirradiation incubation in saline followed by a further incubation in nutrient medium increases the excision as compared to that seen in either nutrient medium or saline alone . Previous data regarding both pyrimidine dimer removal and the survival of haploid and diploid cells after ultraviolet irradiation and either immediate or delayed plating are discussed.

J Bacteriol, 1975 Mar, 121(3), 1064 - 73
Kinetics of induced and repressed enzyme synthesis in Saccharomyces cerevisiae; Lawther RP et al.; Our previous work has shown that both induction, after addition of inducer, and loss of ability to produce allophanate hydrolase, after removal of inducer, proceed more rapidly than expected from the reported half-life of messenger ribonucleic acid in Saccharomyces cerevisiae . As a basis of rectifying these observations, we have characterized induction and repression of allophanate hydrolase synthesis and find that: (i) induction of the hydrolase begins immediately upon addition of inducer, (ii) once induction has been initiated removal of inducer does not result in immediate loss of synthetic capacity, (iii) induction of the capacity to produce hydrolase can occur in the absence of protein synthesis, (iv) the half-life of hydrolase synthetic capacity increases if protein synthesis is inhibited, (v) allophanate hydrolase itself is not degraded upon removal of inducer, and (vi) induction and repression of allophanate hydrolase synthetic capacity likely occurs at the level of transcription.

Z Naturforsch {C}, 1975 Mar-Apr, 30(2), 248 - 52
{Characterisation of RNA from synchronously growing yeast cells (Saccharomyces cerevisiae) as separated by columns of methylated albumin on Kieselgur (MAK) (author's transl)}; Braun R; Total RNA, extracted from synchronously growing yeast cells by the method of Georgiev-Mantieva, was separated by columns of methylated albumin on Kieselgur (MAK) . By comparison with definited RNA's in discelectrophorese and after pulse labelling with {3H}methionine the following fractions are identified: t-RNA, 5.8S RNA, m-RNA, 18S and 25S R-RNA and their precursors 20S, 27S and 35S . High molecular fractions of RNA between 40S and 70S were also found.

J Biol Chem, 1975 Feb 25, 250(4), 1269 - 74
The enzymic conversion of protoporphyrinogen IX to protoporphyrin IX . Protoporphyrinogen oxidase activity in mitochondrial extracts of Saccharomyces cerevisiae; Poulson R et al.; The oxidation of protoporphyrinogen IX to protoporphyrin IX in yeast cells is enzyme-dependent . The enzyme, protoporphyrinogen oxidase, associated with purified mitochondria isolated from Saccharomyces cerevisiae was solubilized by sonic treatment in the presence of detergent and partially purified . The molecular weight of the enzyme was 180,000 plus or minus 18,000 . The purified preparation could be stored at -20 degrees in the presence of 20% glycerol for several months without loss of activity . Enzyme activity was destroyed by heating above 40 degrees and by proteolytic digestion and irreversible inactivation occurred outside the pH range of 4.0 to 9.5 . The pH optimum of the enzymic reaction was 7.45 and the value of the Michaelis constant was approximately 4.8 muM . Protoporphyrinogen oxidase did not catalyse the oxidation of coproporphyrinogen I or III or uroporphyrinogen I or III and the rate of enzymic oxidation of mesoporphyrinogen IX was less than 20% of that observed with protoporphyrinogen IX . The presence of thiol groups in the enzyme system was indicated but no metal ion or other cofactor requirement was demonstrated . Enzyme activity was insensitive to cyanide, 2,4-dinitrophenol, and azide whereas it was inhibited in the presence of Cu-2+ or Co-2+ ions, high ionic strength, heme, or hemin.

Biochim Biophys Acta, 1975 Feb 14, 375(3), 446 - 61
The biogenesis of mitochondrial membranes in the yeast Saccharomyces cerevisiae; Janki RM et al.; Membrane lipids of yeast mitochondria have been enriched by growing yeast cells in minimal medium supplemented with specific unsaturated fatty acids as the sole lipid supplement . Using the activity of marker enzymes for the outer (kynurenine hydroxylase) and inner (cytochrome c oxidase and oligomycin-sensitive ATPase) mitochondrial membranes, Arrhenius plots have been constructed using both promitochondria and mitochondria obtained from O2-adapting cells in the presence of a second unsaturated fatty acid (i.e . linoleate (N2) to elaidic (O2)) . Transition temperatures which reflect the unsaturated fatty acid enrichment of the new membranes reveal interesting features involved in the mechanism of the assembly of these two mitochondrial membranes . This approach was further enforced with both lipid depletion and mitochondrial protein inhibition studies . Kynurenine hydroxylase which does not require fatty acid for its continued synthesis during aerobiosis seems to be incorporated into the preformed linoleate-anaerobic outer membrane . The newly synthesized activities of inner mitochondrial membrane enzymes on the other hand, appear to integrate their activity into newly formed aerobic-elaidic-rich inner membrane . These latter enzymes show a distinct dependence on fatty acid supplement for their continued synthesis during their aerobic phase . This suggests that O2-dependent proteo-lipid precursors are formed before these enzymes are integrated into their membrane mosaic . Two separate models are proposed to explain these results, one for the lipid-rich outer mitochondrial membrane and another for the protein-rich inner mitochondrial membrane.

J Biol Chem, 1975 Feb 10, 250(3), 863 - 6
Prenyltransferase from Saccharomyces cerevisiae . Purification to homogeneity and molecular properties; Eberhardt NL et al.; Prenyltransferase (EC 2.5.1.1) has been purified to homogeneity from the supernatant fraction of yeast by ammonium sulfate fractionation, diethylaminoethyl-cellulose and hydroxylapatite chromatography, and column isoelectric focusing techniques . The active enzyme from isoelectric focusing columns emerged as a single symmetrical peak with specific activities 15- to 35-fold higher than previously reported preparations . The enzyme was found to be homogeneous by continuous polyacrylamide gel electrophoresis at pH 8.4 and discontinuous polyacrylamide gel electrophoresis at pH 6.9 as well as sodium dodecyl sulfate polyacrylamide electrophoresis at pH 7.0 . By means of gel chromatography and sodium dodecyl sulfate polyacrylamide gel electrophoresis, the protein was shown to be a dimer with a molecular weight of 84,000 plus or minus 10% . The isoelectric point of the enzyme was determined to be 5.3 . The enzyme synthesizes farnesyl and geranylgeranyl pyrophosphates from dimethylallyl, geranyl, and farnesyl pyrophosphates . Michaelis constants for the enzyme were 4, 8, and 14 mu M for isopentenyl, dimethylallyl, and geranyl pyrophosphates, respectively.

J Bacteriol, 1975 Feb, 121(2), 571 - 6
Urea transport in Saccharomyces cerevisiae; Cooper TG et al.; Urea transport in Saccharomyces cerevisiae occurs by two pathways . The first mode of uptake is via an active transport system which: (i) has an apparent Km value of 14 muM, (ii) is absolutely dependent upon energy metabolism, (iii) requires pre-growth of the cultures in the presence of oxaluric acid, gratuitous inducer of the allantoin degradative enzymes, and (iv) is sensitive to nitrogen repression . The second mode of uptake which occurs at external urea concentrations in excess of 0.5 mM is via either passive or facilitated diffusion.

J Bacteriol, 1975 Feb, 121(2), 429 - 33
Cellular content of ribonucleic acid and protein in Saccharomyces cerevisiae as a function of exponential growth rate: calculation of the apparent peptide chain elongation rate; Boehlke KW et al.; The average cellular content of ribonucleic acid and protein was determined in cultures of Saccharomyces cerevisiae growing exponentially at different rates in a variety of media . Estimations of the proportion of total cellular ribonucleic acid that is made up of ribosomal ribonucleic acid were used to calculate the average number of ribosomes per cell at the different growth rates . The fraction of ribosomes actively engaged in translation was estimated by sucrose gradient centrifugation of ribosomes and polysomes . These data were used in a calculation of the apparent time taken for the addition of an amino acid to the growing polypeptide chain; this value was found to vary linearly with growth rate over a fivefold range of doubling times.

Appl Microbiol, 1975 Feb, 29(2), 195 - 200
Dichlorofluoromethane inactivates Saccharomyces cerevisiae; Middleton JL et al.; Saccharomyces cerevisiae was incubated in aerosol cans containing YM broth and dichlorofluoromethane (f-21) . The presence and number of viable cells were determined by inoculating (1% vol/vol) YM broth and by the plate count procedure (YM agar) . Inactivation of the yeast was greater or more rapid when: (i) the thermodynamic activity (saturation value) of f-21 became greater through increasing the concentration of chemical from 0.5 to 1.5% (wt/wt) in a given volume (20, 40, or 80 ml) of broth, or by holding the concentration of chemical constant but increasing the volume of broth in the test vessel, (ii) the temperature of treatment was increased (7, 22, 37, and 47 C), (iii) samples with 1.5% (wt/wt) f-21 were agitated, (iv) young (8 h) rather than old (36 h or 10 days) cells were treated, and (v) cells were grown in YM broth without, rather than with, glucose . Adjusting the pH (6.3 to 4.0) of broth before treatment, pretreating the substrate with f-21, or distilling the chemical before use had no effect on viability of cells when treated with f-21 . Yeast cells inactivated by f-21, chlorine, or heat were more resistant to disruption by sonic treatment than were viable cells.

Biochem J, 1975 Feb, 146(2), 401 - 7
Phase transitions in yeast mitochondrial membranes . The effect of temperature on the energies of activation of the respiratory enzymes of Saccharomyces cerevisiae; Watson K et al.; The effect of temperature on the activation energies of mitochondrial enzymes of the yeast Saccharomyces cerevisiae was examined . Non-linear Arrhenius plots with discontinuities in the temperature range 14-19 degrees C and 19-22 degrees C were observed for the respiratory enzymes and mitochondrial ATPase (adenosine triphosphatase) respectively . A straight-line Arrhenius plot was observed for the matrix enzyme, malate dehydrogenase . The activation energies of the enzymes associated with succinate oxidation, namely, succinate oxidase, succinate dehydrogenase and succinate-cytochrome c oxidoreductase, were in the range 60-85kJ/mol above the transition temperature and 90-160kJ/mol below the transition temperature . In contrast, the corresponding enzymes associated with NADH oxidation showed significantly lower activation energies, 20-35kJ/mol above and 40-85kJ/mol below the transition temperature . The discontinuities in the Arrhenius plots were still observed after sonication, treatment with non-ionic detergents or freezing and thawing of the mitochondrial membranes . Discontinuities for cytochrome c oxidase activity were only observed in freshly isolated mitochondria, and no distinct breaks were observed after storage at -20 degrees C . Mitochondrial ATPase activity still showed discontinuities after sonication and freezing and thawing, but a linear plot was observed after treatment with non-ionic detergents . The results indicate that the various enzymes of the respiratory chain are located in a similar lipid macroenvironment within the mitochondrial membrane.

Biochim Biophys Acta, 1975 Jan 31, 376(1), 27 - 41
The respiratory chain in a ubiquinone-deficient mutant of Saccharomyces cerevisiae; De Kok J et al.; 1 . Two allelic mutants of Saccharomyces cerevisiae with a deficiency in the biosynthesis of ubiquinone have been isolated . The properties of one particular mutant strain were investigated . Submitochondrial particles of this strain contain maximally 3% of the amount of ubiquinone in wild-type particles; the amounts of other components of the respiratory chain are essentially normal . 2 . The respiratory rates of mutant cells, mitochondria and submitochondrial particles are low with ubiquinone-dependent substrates, but are restored to normal levels by addition of Q-1; the restored respiration is antimycin sensitive . Intact cells and mitochondria show respiratory control both in the absence and presence of Q-1 . 3 . The NADH:Q-1 oxidoreductase of submitochondrial particles of the mutant followspseudo first-order kinetics in {Q-1} . QH2-1 inhibits competitively with respect to Q-1, the Ki for QH2-1 being equal to the Km for Q-1 . 4 . Succinate dehydrogenase in both wild-type and mutant submitochondrial particles can be activated by NADH . 5 . The turnover number of succinate dehydrogenase in the mutant, measured with phenazine methosulphate as primary electron acceptor, is about one-half that of wild-type particles . The turnover numbers measured with Q-1 as electron acceptor are about the same in the two types of particles . 6 . The kinetics of redox changes in cytochrome b, in the presence of antimycin and oxygen, are distinctly different in the mutant and wild-type particles . They indicate that ubiquinone plays an important role in the phenomenon of the increased reducibility of cytochrome b induced by antimycin plus oxygen.

J Biol Chem, 1975 Jan 25, 250(2), 775 - 82
Mitochondrial assembly in respiration-deficient mutants of Saccharomyces cerevisiae . IV . Effects of nuclear amber suppressors on the accumulation of a mitochondrially made subunit of cytochrome c oxidase; Ono BI et al.; Earlier studies from this laboratory have shown that cytochrome c oxidase from bakers' yeast contains seven subunits, three of which are made in the mitochondrion (Mason, T . L., and Schatz, G . (1973) J . Biol . Chem . 248, 1355) . Moreover, a cytochrome c oxidase-less yeast mutant (pet 494-1) was isolated which lacked one of the mitochondrially made subunits (Ebner, E., Mason, T . L., and Schatz, G . (1973) J . Biol . Chem . 248, 5369) . Surprisingly, the mutated gene was localized in the nucleus . The results presented here demonstrate that this mutant phenotype can be suppressed by nuclear amber suppressors which affect translation on cytoplasmic ribosomes . This fact was established by two methods, (a) By constructing pet 494-1 strains possessing various amber and ochre markers, isolating respiring revertants from these strains, and demonstrating co-reversion of the amber (but not of the ochre) markers . (b) By coupling the pet 494-1 allele with the well characterized amber suppressor gene SUP 4-3 . These data show that suppressor genes located on nuclear chromosomes may control the accumulation of a mitochondrially synthesized polypeptide . The present results also allow some tentative conclusions about the mechanism of the pet 494 mutation . Because it is highly unlikely that the cytoplasmic and the mitochondrial translation system share a common suppressor, the pet 494 locus probably does not code for the missing mitochondrially made subunit, but for a cytoplasmically made protein . This as yet unidentified protein seems to control the synthesis or the integration of the mitochondrially made subunit . Nuclear suppressor genes may thus be useful tools for studying the role of cytoplasmic protein synthesis in mitochondrial formation.

Mol Gen Genet, 1975, 138(2), 157 - 64
Genetics of alcohol dehydrogenase in Saccharomyces cerevisiae . II . Two loci controlling synthesis of the glucose-repressible ADH II; Ciriacy M; Two unlinked loci controlling the glucose-repressible alcohol dehydrogenase (ADH II) in Saccharomyces cerevisiae were investigated . One locus (AD R2) was characterized by electrophoretically slow and fast alleles and by inactive adr2 mutant alleles . The ADH II pattern of heteroallelic slow X fast diploids indicates a tetrameric structure of the enzyme . AD R2 was considered as the structural gene, which codes for the ADH II subunits . Allelic adr2-f mutants could be classified by their response to the slow wild type allele (AD RS-S) in heterozygous diploids . In most cases, only the slow band appeared . In three adr2-f/ADR2-S crosses hybrid enzymes between inactive fast and active slow enzymes were formed . It was demonstrated, that allelic interactions at the protein level are not restricted to electrophoretical behaviour of hybrid enzymes . They also influence specific activities and substrate affinities . The other locus investigated, AD R1, was characterized by ADH II negative mutants (adr1) and by allelic mutants which generate only very low activity (ADR1-L) . ADR1 does not influence the electrophoretic properties of slow and fast ADH II proteins . adr1 mutants have an intact structural gene, which is not expressed . The gene has probably a regulatory function with respect to ADH II synthesis.

Folia Microbiol (Praha), 1975, 20(5), 371 - 8
The chitin-glucan complex of Saccharomyces cerevisiae . III . Electron-microscopic study of the prebudding stage; Seichertova O et al.; Differentiation of the cell wall of Saccharomyces cerevisiae at the site of the future bud was followed . A lentil-like structure originates on the inner side of the cell wall during the first phase . At the same time, an electron-dense layer occurs at the boundary between the inner layer of the cell wall and the lentil-like structure . During the second phase granular material is accumulated at the lower side of the lentil-like structure . During the third phase the lentil-like structure is split apart due to proliferation of the granular material resulting in formation of the base of the encircling region . The marked electron-dense layer observed from the first phase is attached to the surface of the encircling region during differentiation of the latter . During the budding proper the outer layers of the cell wall protrude and the end of the encircling region, together with the adjacent electron-dense layer, acquire their definitive appearance of rings, observed as marked electron-transparent and electron-dense tears on ultrathin sections.

Basic Life Sci, 1975, 5B, 557 - 65
The fate of UV-induced pyrimidine dimers in the nuclear and mitochondrial DNAs of Saccharomyces cerevisiae on various postirradiation treatments and its influence on survival and cytoplasmic "petite" induction; Waters R et al.; The photoreactivability of UV-induced pyrimidine dimers in the nuclear and mitochondrial DNAs of Saccharomyces cerevisiae has been investigated in conjunction with the fate of these photoproducts following postirradiation dark incubation in saline and nutrient media . In all instances, survival and "petite" induction were measured . An attempt has been made to relate these results to present ideas on the repair of UV damages in DNA.

Acta Microbiol Pol A, 1975, 8(3), 161 - 7
Ultrastructural changes in zygote formation and autoradiographic study of DNA replication during conjugation in Saccharomyces cerevisiae; Zaborowska D et al.; The following stages of mating reaction were analysed in electron micrographs: initial contact of the conjugating cells, formation of a tube-like structure between the mating partners, nuclear fusion and formation of first diploid bud . Nuclear fusion was observed to take place within the conjugation tube, the fusion nucleus, however, was often localised in one of the initial conjugants . The stage of fusion nucleus, preceding the first diploid bud formation, is of longest duration in the mating process . The second longest stage is the formation of a tube-like structure . The whole conjugation process lasts at 25 degrees approximately 60 min . According to the autoradiographic data, DNA synthesis begins after nucelar fusion and proceeds during formation of the first diploid bud.

Mol Gen Genet, 1975, 138(1), 53 - 63
Genetic properties of some amber-ochre supersuppressors in Saccharomyces cerevisiae; Gerlach WL; 21 amber-ochre supersuppressor alleles have been isolated in a strain of Saccharomyces cerevisiae . Their dominance-recessiveness, temperature sensitivity, allelism, intergenic and intragenic complementation properties and their effect on cell viability and colony growth rate have been characterized . They are compared with the yeast amber-ochre supersuppressors described by Inge-Vechtomov and Andrianova (1970a, b) and Hawthorne and Leupold (1974) . The possible molecular basis of their suppressor activity is discussed in relation to their genetic properties.

Microbios, 1975, 12(49), 103 - 9
Effect of pyrimethamine on the morphology and ultrastructure of Saccharomyces cerevisiae; Stone AB et al.; Sub-lethal levels of the folate analogue, pyrimethamine, caused pronounced cell elongation in Saccharomyces cerevisiae strain B41 when grown in glycerol medium . The orientation of bud development was also altered . Electron microscopy of thin sections showed an increase in cell wall thickness, but apart from this and the overall cell shape, the ultrastructure of the cells was normal . The structural abnormalities are attributed to alterations in the plasmalemma caused by protein synthesis inhibition in the mitochondria.

Acta Microbiol Pol A, 1975, 7(2), 77 - 85
Specificity and origin of the Mod2- mutation which restores respiratory sufficient phenotype in some pet mutants in Saccharomyces cerevisiae; Ulaszewski S et al.; It has been found that Mod2- mutation restores respiratory sufficient phenotype in cytochrome b less mutant MB127-20C . Mod2- gene when present in the same haploid cell with mutant gene pet25 causing deficiency in cytochromes a+a3 and b seems to be responsible for reappearance of cytochrome b in the cytochrome spectrum as well partial respiratory activity . However, the restored respiratory activity seems to be inefficient as growth on unfermentable carbon sources is still impossible . Evidences are presented that the Mod2- mutation originates from respiratory sufficient strain 18-27 in which op1 mutation has been induced.

Biochimie, 1975, 57(1), 49 - 59
tRNAs undermethylation in a met-regulatory mutant of Saccharomyces cerevisiae; Fesneau C et al.; A study of in vivo and in vitro methylation of tRNAs in regulatory mutants affected in methionine-mediated repression (eth2, eth3, eth10) has led to the following results: 1) The eth2-2 carrying strain presents a great undermethylation of its tRNAs of the same order of magnitude as observed during methionine starvation of methionine auxotrophs . 2) This undermethylation leads to a shift of the tRNAIII met peak on a BD cellulose column, while tRNAIII met peak is unchanged . 3) The study of a double mutant strain carrying eth2 and met2 mutations has shown that this undermethylation is a consequence of the high internal pool of methionine . 4) Undermethylation unequally affects the different bases and the different tRNA species.

Acta Microbiol Pol A, 1975, 7(1), 25 - 32
A search for Saccharomyces cerevisiae mutants with an increased sensitivity to nitrous acid; Baranowska H et al.; Six strains with an increased nitrous acid sensitivity were isolated (Fig . 1) . The putative HNO2-sensitive mutants, as well as the parental strain 55R5 behaved abnormally in crosses, so that studies on the segregation of the sensitivity were difficult and unreliable . During 1.5 years the oversensitivity of the mutants gradually decreased to disappear completely (Tab . V) . The differences in HNO2 sensitivity between respiratory-sufficient and cytoplasmic respiratory-deficient strains (Tab . I), as well as between different respiratory-sufficient strains (Tab . II-IV) are analysed.

Biochimie, 1975, 57(5), 647 - 55
Studies on protoporphyrin biosynthetic pathway in Saccharomyces cerevisiae ; characterization of the tetrapyrrole intermediates; Brouillet N et al.; An acellular extract of the yeast, Saccharomyces cerevisiae, incubated with ALA, is able to synthesize protoporphyrin from this precursor . Several tetrapyrrole intermediates were extracted from the medium and purified by silica gel chromatography . The chromatographic behaviour and the spectral properties of the isolated seven free carboxylic porphyrins (and of the corresponding esters), show that each product has a different carboxyle number, varying from eight (uroporphyrin) to two (protoporphyrin) . The identification of five of them (octa- to tetracarboxymethyl-porphyrinester) is confirmed by mass spectrometry . The effect of physical factors (temperature, pH, time) on the protoporphyrin biosynthesis system indicates that the enzymes catalysing the first steps of the pathway (ALA leads to Coproporphyrin) are more stable than those catalysing the last steps (Coproporphyrin leads to Protoporphyrin) . Results obtained with some enzymatic inhibitors (EDTA, OP, pCMB) show the sensitivity of the ALA dehydratase to OP and to pCMB (confirming therefore its nature as a metallo- and sulfhydryl enzyme) and also of the overall porphyrin synthesis system to these three agents.

Genetika, 1975, 11(3), 122 - 6
{Co60 gamma-ray sensitivity of a series of strains of Saccharomyces cerevisiae yeasts bearing different mutations . I . Radiosensitivity of haploid strains}; Sokurova EN; Sensitivity to gamma-rays Co60 of haploid strains of Saccharomyces cerevisiae carrying ade1-6 mutations and dominant, semidoninant and recessive suppressors was investigated . It was shown that 3 out of 4 studied strains with ade1-6 mutation had reliable increased radioresistance . The increased radioresistance was observed also in strains carrying, beside ade1-6 mutation, dominant and semidominant suppressors . However the strain carrying a recessive suppressive mutation turned to be radiosensitive . A conclusion is drawn that rediosensitivity of yeast cells can be influenced by different mutations affecting the process of cell metabolism.

Genetika, 1975, 11(8), 96 - 103
{Dominant nonsense suppressors restricting the killer activity in Saccharomyces cerevisiae}; Nesterova GF et al.; Dominant suppressors of the first type nonsense mutations, ade1-6, hisX, lys9-A21 and leu2-2, inhibit the killer activity in Peterhoff genetic stocks of Saccharomyces cerevisiae . Phenotypes CN (weak killer at 20 degrees, neutral at 32 degrees) and N (neutral at both temperatures) arising in the presence of the suppressors in killer strains are dominant toward S phenotype and toward K phenotype.

Genetika, 1975, 11(8), 108 - 14
{Nuclear suppression of a mitonchondrial mutation of tetracycline resistance in Saccharomyces cerevisiae}; Nevzgliadova OV; Nuclear suppression of the mitochondrial mutation of tetracycline resistance (Tr) is found . The suppressor mutation (i) is monogenous and recessive . Besides phenotypical suppression of mitochondrial resistance to tetracycline, it causes "the arrest" of the Tr plasmagene transmission . The effect of the suppressor is specific.

Genetika, 1975, 11(7), 104 - 12
{Genetic-biochemical study of acid phosphatases from Saccharomyces cerevisiae yeasts . IV . Genetic control of acid phosphatase II activity}; Kozhin SA et al.; Genetic control of exocellular acid phosphatase of yeast Saccharomyces cerevisiae (acph 2) is studied . 64 mutants with the impaired activity of acid phosphatase have been obtained by UV-irradiation . All the mutations have been distributed among 4 genes: ACP1, ACP2, ACP3, ACP4 using functional and recombinational tests for allelism . It is shown that mutations in genes ACP1--ACP3 are recessive, but in the gene ACP4--dominant . The gene ACP4 is found to be located 0.41+/-0.064 in strains from centromere and to have no linkage with ACP1 . Possible functions of genes studied are under discussion.

Genetika, 1975, 11(6), 119 - 27
{Single-parent inheritance of mitochondrial mutations resistant to tetracycline in Saccharomyces cerevisiae}; Nevzgliadova OV; The mitochondrial mutation of the resistance to tetracycline (Tr) is shown to have one-parent inheritance . The polarity of recombination between the gene Tr and other mitochondrial mutations also depends on the alleles controlling the mating type as well as in another nuclear gene i, suppressing Tr-resistance . The "arrest" of Tr-transmission in alpha-haploid or in a haploid with gene-suppressor induces the process of mitochondrial recombination.

Genetika, 1975, 11(9), 104 - 15
{Genetico-biochemical study of acid phosphatases in Saccharomyces cerevisiae yeast . V . Genetic control of regulation of acid phosphatase II synthesis}; Samsonova MG et al.; Regulation of exocellular enzyme acid phosphatase 2 synthesis is studied . 21 mutants with consitutive synthesis of this enzyme are obtained by UV-irradiation . All mutants were recessive and were distributed among 3 complementation groups ACP80, ACP81, ACP82 . Two groups, ACP80 and ACP81 corresponded to two different genes, which showed no linkage with ACP1, ACP2 and PHO1 genes . The type of synthesis of acid phosphatase 2 in strains acp1 acp80, acp1 acp81, acp2 acp80, acp2 acp81 is determined, and a conclusion is made about the participation of ACP2 gene in the regulation of acid phosphatase 2 synthesis . It is shown that some mutations in PHO1 gene, which block the activity of acid phosphatase 1, influence the activity and regulation of acid phosphatase 2.

Folia Microbiol (Praha), 1975, 20(4), 320 - 5
Transport of acyclic polyols in Saccharomyces cerevisiae; Canh DS et al.; Acyclic polyols (erythritol, xylitol, ribitol, D-arabinitol, mannitol, sorbitol and galactitol) are not metabolized by Saccharomyces cerevisiae . They are taken up by a fast non-active process, reaching 40-70% distribution referred to total cell water . The uptake is insensitive to temperature, pH (between 4 and 8), 2,4-dinitrophenol and uranyl ions . Its initial rate rises linearly with concentration from 10(-5)M to 1M . The process resembles simple diffusion through large pores or the trapping of the whole solution on the surface . Protoplasts behave like whole cells in this respect . Only erythritol shows a second type of uptake which is inhibitor-insensitive but temperature-dependent.

Antonie Van Leeuwenhoek, 1975, 41(3), 249 - 56
Regulation of citrate synthase activity of Saccharomyces cerevisiae; Coleman JS et al.; Citrate synthase activity of Saccharomyces cerevisiae was determined by a radioactive assay procedure and the reaction product, 14C-citric acid, was identified by chromatographic techniques . ATP, d-ATP, GTP and NADH were most inhibitory to the citrate synthase invitro . The activity was inhibited to a lesser extent by ADP, UTP, and NADP whereas, AMP and CTP were much less inhibitory . NADH, like NAD, glutamic acid, glutamine, arginine, ornithine, proline, aspartic acid and alpha-ketoglutarate exhibited no inhibition . These results have been discussed in the light of the role of citrate synthase for the energy metabolism and glutamic acid biosynthesis.

Folia Microbiol (Praha), 1975, 20(6), 467 - 9
Effect of some aldoses on growth of Saccharomyces cerevisiae inhibited with molybdenum; Zemek J et al.; The inhibitory effect of molybdenum ions on growth of yeasts at pH 5.5 was found to be decreased by aldoses in the following order: D-talose greater than L-mannose greater than L-ribose greater than D-lyxose greater than L-galactose greater than L-arabinose greater than L-glucose greater than L-xylose . Increased concentrations of molybdenum brought about morphological changes of yeast cells . Cells grown under these conditions were smaller, had thicker walls and formed clusters.

Mol Gen Genet, 1974, 135(4), 309 - 26
Nucleo-cytoplasmic interaction between oligomycin-resistant mutations in Saccharomyces cerevisiae; Colson AM et al.; 1.A single-gene nuclear mutant of Saccharomyces cerevisiae, isolated as oligomycin-resistant, exhibits in vivo cross-resistance to venturicidin and collateral sensitivity to Synthalin . All three compounds are inhibitors of mitochondrial oxidative phosphorylation . Oligomycin resistance and Synthalin sensitivity are recessive, while venturicidin resistance is dominant . 2 . Acytoplasmic mutant, also isolated as oligomycin-resistant, shows collateral sensitivity to both Synthalin and venturicidin . All three traits undergo mitotic segregation in diploids formed by crossing mutant and normal halpoids . 3 . A novel nucleocytoplasmic interaction is observed in diploids formed by crossing haploid strains containing the nuclear and the cytoplasmic mutations, respectively . The dominant venturicidin resistance determined by the nuclear gene undergoes mitotic segregation, which results from a suppression of the nuclear phenotype by the cytoplasmic mutation . When a diploid mitotic segregant contains primarily mutant-type mitochondria, venturicidin resistance is completely suppressed . In haploids containing both the nuclear and cytoplasmic mutations, suppression is only partial . 4 . Oxidative phosphorylation and ATPase in mitochondrial fractions isolated fromcytoplasmic mutant cells are less sensitive to inhibition by oligomycin than normal, but in vitro sensitivity to venturicidin is not significantly changed . In similar mitochondrial fractions isolated from normal and nuclear mutant cells, no significant differences in sensitivity to either inhibitor are detected . 5 . The molecular basis for the nucleocytoplasmic suppression of venturicidin resistance may involve participation of mitochondrial membrane, plasma membrane or both . Either mitochondria can undergo changes in venturicidin sensitivity upon isolation, or the molecular entity which controls access of venturicidin to the mitochondria resides outside of the organelles . 6 . Our data establish that aspects of the response in vivo of both venturicidin and Snythalin are controlled by the mitochondrial genome . 7 . The nucleocytoplasmic interaction described here is the first example in which a specific restricted mitochondrial mutation modifies the phenotypic expression of a nuclear gene.

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