J Bacteriol, 1981 Oct, 148(1), 241 - 7 Proline transport in Saccharomyces cerevisiae; Lasko PF et al.; The yeast Saccharomyces cerevisiae is capable of utilizing proline as the sole source of nitrogen . Mutants of S . cerevisiae with defective proline transport were isolated by selecting for resistance to either of the toxic proline analogs L-azetidine-2-carboxylate or 3,4-dehydro-DL-proline . Strains carrying the put4 mutation are defective in the high-affinity proline transport system . These mutants could still grow when given high concentrations of proline, due to the operation of low-affinity systems whose existence as confirmed by kinetic studies . Both systems were repressed by ammonium ions, and either was induce by proline . Low-affinity transport was inhibited by histidine, so put4 mutants were unable to grow on a medium containing high concentrations of proline to which histidine has been added. Chem Biol Interact, 1981 Oct, 37(1-2), 123 - 40 Toxicity, interstrand cross-links and DNA fragmentation induced by 'activated' cyclophosphamide in yeast; Fleer R et al.; Treatment of yeast cells with 4-hydroperoxy-cyclophosphamide (4-OOH-CP), the chemically activated form of cyclophosphamide, results in cell killing, induction of DNA interstrand cross-links and DNA fragmentation . Toxicity of 4-OOH-CP is greatly influenced by the cell's capacity of DNA dark-repair: genetic blocking of non-epistatic pathways of DNA repair results in an increase of sensitivity of several orders of magnitude . DNa primary lesions have been measured using a haploid, excision deficient, dTMP-uptaking mutant of S . cerevisiae . In this strain, a significant extent of DNA cross-linking can already be observed at a survival of 88% . At a concentration of 100 nmol/ml 4-OOH-CP, renaturability of DNA increases up to 12 h of drug exposure and drops to lower values upon further incubation . In contrast to the time course of renaturability, DNA double-strand breakage is seen at later stages of drug treatment and continuously increases as a function of incubation time . Whereas inactivation of cells and induction of strand breakage continue upon postincubation of cells, comparable effects are much less pronounced for DNA renaturability. Biochim Biophys Acta, 1981 Sep 24, 665(3), 420 - 6 Characterization of phosphatidylserine synthase from Saccharomyces cerevisiae and a mutant defective in the enzyme; Nikawa JI et al.; The membrane fraction of exponentially growing cells of Saccharomyces cerevisiae was found to exhibit phosphatidylserine synthase activity . The enzyme was solubilized by Triton X-100 and chromatographed on a Sepharose 6B column . The enzyme had a pH optimum between 8.0 and 8.5 . The apparent Km values for CDPdiacylglycerol and L-serine were 0.12 and 13 mM, respectively . Triton X-100 stimulated the enzyme . Mg2+ or Mn2+ was required for the activity . Ca2+ was inhibitory at relatively low concentrations . The enzyme was highly specific to L-serine . Labeling experiments showed that the enzyme synthesized phosphatidylserine by transferring the phosphatidyl moiety to L-serine . A mutant of S . cerevisiae defective in phosphatidylserine synthase was isolated . The strain required ethanolamine for its growth . Ethanolamine could be substituted by choline or high concentrations of L-serine . The mutant showed normal levels of CDPdiacylglycerol-inositol 3-phosphatidyltransferase and phosphatidylethanolamine methyltransferase activities. Biochemistry, 1981 Sep 15, 20(19), 5403 - 11 Guanidine hydrochloride induced unfolding of yeast iso-2 cytochrome c; Nall BT et al.; The properties of the guanidine hydrochloride induced unfolding transition of iso-2 cytochrome c (iso-2) from Saccharomyces cerevisiae have been investigated by using kinetic and equilibrium techniques and have been compared with previously published studies of horse cytochrome c, which differs from iso-2 by 46% in amino acid sequence . Measurements of absorbance in the ultraviolet and visible spectral regions as a function of guanidine hydrochloride concentration give superimposable equilibrium transition curves with a midpoint of 1.15 M at pH 7.2 and 20 degrees C . A two-state analysis of the equilibrium data gives a Gibbs free energy of unfolding of 3.1 kcal/mol at 20 degrees C in the absence of denaturant . This agrees well with the predicted difference in stability between S . cerevisiae iso-2 and horse cytochrome c estimated from the free energies of transfer of buried hydrophobic groups . Three kinetic phases associated with folding can be detected throughout most of the transition zone . Two of the phases are detected by stopped-flow mixing experiments . The third phase is over within the mixing time of the flow experiments but is detectable by temperature jumps . At 20 degrees C, pH 7.2, the slowest phase (T1) is in the 20-100-s time range, the middle phase (T2) is in the 0.1-3-s range, and the fastest phase (T3) is on the order of 1 ms . For the reactions observed in the stopped flow (T1 and T2), a simplified three-state mechanism can be used to predict quantitatively the relative amplitudes of the phases and the equilibrium unfolding curve from the observed time constant data . Previously this same mechanism has been successful in describing the folding reactions of horse cytochrome c {Hagerman, P . J . (1977) Biopolymers 16, 731} . We suggest that the qualitative features of protein folding reactions may be conserved among homologous proteins. Mol Cell Biol, 1981 Sep, 1(9), 836 - 42 Genetic complementation of the Saccharomyces cerevisiae leu2 gene by the Escherichia coli leuB gene; Storms RK et al.; The leucine operon of Escherichia coli was cloned on a plasmid possessing both E . coli and Saccharomyces cerevisiae replication origins . This plasmid, pEH25, transformed leuA, leuB, and leuD auxotrophs of E . coli to prototrophy; it also transformed leu2 auxotrophs of S . cerevisiae to prototrophy . beta-Isopropylmalate dehydrogenase was encoded by the leuB gene of E . coli and the leu2 gene of yeast . Verification that the leuB gene present on pEH26 was responsible for complementing yeast leu2 was obtained by isolating in E . coli several leuB mutations that resided on the plasmid . These mutant leuB- plasmids were no longer capable of complementing leu2 in S . cerevisiae . We conclude that S . cerevisiae is capable of transcribing at least a portion of the polycistronic leu operon of E . coli and can translate a functional protein from at least the second gene of this operon . The yeast Leu+ transformants obtained with pEH25, when cultured in minimal medium lacking leucine, grew with a doubling time three to four times longer than when cultured in medium supplemented with leucine. Nucleic Acids Res, 1981 Aug 11, 9(15), 3621 - 40 Secondary structure comparisons between small subunit ribosomal RNA molecules from six different species; Zwieb C et al.; Secondary structure models are presented for three pairs of small subunit ribosomal RNA molecules . These are the 16S rRNA from E . coli cytoplasmic and Z . mays chloroplast ribosomes, the 18S rRNA from S . cerevisiae and X . laevis cytoplasmic ribosomes, and the 12S rRNA from human and mouse mitochondrial ribosomes . Using the experimentally-established secondary structure of the E . coli 16S rRNA as a basis, the models were derived both by searching for primary structural homology between the three classes of sequence (12S, 16S, 18S), and also by searching for compensating base changes in putative helical regions of each pair of sequences . The models support the concept that secondary structure of ribosomal RNA has been extensively conserved throughout evolution, differences in length between the three classes of sequence being accommodated in distinct regions of the molecules. J Bioenerg Biomembr, 1981 Aug, 13(3-4), 141 - 8 Effect of ubiquinone extraction on ubiquinol-1 oxidase activity in beef heart mitochondria; Pasquali P et al.; Extraction of endogenous ubiquinone with different methods does not influence ubiquinol oxidase activity in lyophilized mitochondria in terms of KM, although a decrease of Vmax is sometimes observed . Experiments with submitochondrial particles from a UQ-deficient mutant of S . cerevisiae confirm the results with UQ-depleted mitochondria and support the idea that endogenous ubiquinone is not required for the oxidation of exogenous ubiquinols by complex III. Cell, 1981 Aug, 25(2), 525 - 36 Distinct repressible mRNAs for cytoplasmic and secreted yeast invertase are encoded by a single gene; Perlman D et al.; We have studied regulation of invertase putative structural genes (SUC) in S . cerevisiae and the synthetic relationship between secreted, glycosylated invertase (E.C.3.2.1.26) and the cytoplasmic, nonglycosylated form of the enzyme . Using immunoprecipitation and gel electrophoresis, we have analyzed invertase polypeptides and glycopeptides synthesized in vitro and in vivo . Analysis of size-fractionated mRNA from a SUC2 strain has shown that three mature, catabolite-repressible mRNA species direct the in vitro synthesis of three invertase polypeptides that have differing molecular weights . Two of these polypeptides, P63 and P62 (63 and 62 kd), are larger than the polypeptides of the secreted enzyme and are cotranslationally processed by microsomal membranes in vitro to yield secreted invertase glycopeptides (GP90 and GP87) . The smallest polypeptide, P60 (60 kd), which comigrates electrophoretically with cytoplasmic invertase, is not processed . Posttranslationally, a microsomal-membrane detergent extract removes approximately 20 aminoacids from P62 but not from P60 . In vitro translations of mRNAs from a genetically confirmed suc3 mutant strain, from the parental SUC3 strain and from derivative meiotic segregants have shown that the three polypeptides (and therefore three mRNA species) are encoded by one gene . Analysis of in vivo radiolabeled invertase from the same SUC3 and suc3 strains has verified that the SUC3 locus contains the structural gene for secreted and cytoplasmic invertase . Through the derepressed synthesis of multiple primary or processed transcripts, the SUC2 and SUC3 genes are regulated to produce multiple invertase polypeptides . The larger two polypeptides appear to be processed and secreted to yield glycosylated invertase, while the smallest remains in the cytoplasm. Cell, 1981 Aug, 25(2), 451 - 60 Compartmentalized assembly of oligosaccharides on exported glycoproteins in yeast; Esmon B et al.; Temperature-sensitive secretory mutants (sec) of S . cerevisiae have been used to evaluate the stages and localization of glycoprotein oligosaccharide synthesis . At the nonpermissive growth temperature (37 degrees C), the sec mutants accumulate secretory organelles and glycoproteins . Histochemical staining and thin-section electron microscopy reveal that the secreted glycoprotein, acid phosphatase, is contained within one of three distinct organelles that accumulates in different mutants: ER; Golgi-like structures called Berkeley bodies; and 80--100 nm vesicles . When produced at 37 degrees C, invertase and acid phosphatase have less carbohydrate in the mutants that accumulate ER than in other mutants, or than in the wild-type strain . External invertase migrates on SDS-polyacrylamide gels as a heterogeneous species with an apparent molecular weight of 100 to 140 kd . Radiolabeled invertase, immunoprecipitated from extracts of ER-accumulating mutant cells, migrates as a set of three discrete protein species with apparent molecular weights of 79, 81, and 83 kd; the other mutants produce a form more like the secreted enzyme . In each case, removal of N-glycosidically linked oligosaccharides by treatment with endoglycosidase H produces a discrete species that migrates as a protein of 61 kd . Immunochemical analysis of bulk glycoprotein accumulated in the mutants suggests that a major portion of the N-linked oligosaccharide, the outer chain, is added after material passes from the ER. Antimicrob Agents Chemother, 1981 Aug, 20(2), 184 - 9 Physiological response of Saccharomyces cerevisiae to 15-azasterol-mediated growth inhibition; Rodriguez RJ et al.; We studied 15-aza-24-methylene-8,14-cholestadiene-3 beta-ol (15-azasterol) inhibition of Saccharomyces cerevisiae growth . Exposure to sublethal concentrations of this drug caused S . cerevisiae cells to undergo a transient period of inhibition at midlog phase . During growth inhibition the turbidity of each culture remained constant, as did the total cell number . Although the proportion of viable cells in cultures decreased from 90 to 12% during inhibition, methylene blue staining showed that less than 40% of the cells underwent metabolic inactivation . We monitored adenosine triphosphate levels throughout the inhibition cycle, and these levels followed kinetics identical to cell growth kinetics . After overcoming inhibition, cellular lipid extracts revealed the presence of a modified form of 15-azasterol . It appeared that the yeast cells were able to overcome 15-azasterol inhibition by an inactivating transmethylation reaction involving S-adenosylmethionine. Biochemistry, 1981 Jul 7, 20(14), 4217 - 23 Identification of 3,4-dihydroxy-5-hexaprenylbenzoic acid as an intermediate in the biosynthesis of ubiquinone-6 by Saccharomyces cerevisiae; Goewert RR et al.; The mutant strain of Saccharomyces cerevisiae E3-24 is unable to synthesize ubiquinone-6 . When this mutant is grown in the presence of p-hydroxy{U-14C}benzoate or p-hydroxy{carboxy-14C}benzoate, a radioactive compound accumulates . This new metabolite has been isolated and identified as 3,4-dihydroxy-5-hexaprenylbenzoate (3,4-DHHB) . Aerobically grown prototrophic strains of S . cerevisiae were found to contain only low levels of this compound . When strain X963-18C, blocked at homoserine O-transacetylase (in methionine biosynthesis), was deprived of methionine, ubiquinone biosynthesis ceased, and 3,4-DHHB was observed to accumulate . This suggested that S-adenosylmethionine (SAM) could be the methyl donor for 3,4-DHHB . Restoration of methionine to the cultures released this block and resulted in the conversion of 3,4-DHHB to ubiquinone-6, demonstrating a precursor--product relationship . The identification of 3,4-DHHB as an intermediate in ubiquinone biosynthesis in yeast establishes an alternate pathway for ubiquinone biosynthesis in eukaryotes. Proc Natl Acad Sci U S A, 1981 Jul, 78(7), 4466 - 70 Expression and processing of bacterial beta-lactamase in the yeast Saccharomyces cerevisiae; Roggenkamp R et al.; The mode of expression in Saccharomyces cerevisiae of the bacterial antibiotic resistance gene coding for beta-lactamase (EC 3.5.2.6) is described . Yeast transformants, containing hybrid plasmid pMP78-1 consisting of pBR325 in a 2-micrometers DNA vector, synthesize an active beta-lactamase protein . The enzyme was purified about 100-fold over crude extracts . With regard to activity, molecular weight, and binding to specific antibodies the yeast beta-lactamase was indistinguishable from the purified enzyme from Escherichia coli . Because the bacterial enzyme is synthesized as a preprotein with subsequent maturation, the results suggest that S . cerevisiae is able to convert the preprotein to the mature beta-lactamase . This was confirmed by in vitro experiments showing that the bacterial preprotein can be processed by crude extracts of S . cerevisiae. Cell, 1981 Jun, 24(3), 819 - 28 Dispersed 5S RNA genes in N . crassa: structure, expression and evolution; Selker EU et al.; The 5S RNA genes (5S genes) in N . crassa are not tandemly arranged or tightly clustered as in other eucaryotes that have been examined . 55 RNA or cloned 5S DNA hybridizes to at least 30 different restriction fragments of Neurospora DNA . Of 34 5S DNA clones examined, each contains a single 5S gene . Saturation hybridization analyses indicate that there are about 100 copies of 5S genes in the genome of this organism . We have partially or completely sequenced the 5S region of 15 clones . Both identical and highly divergent 5S coding regions were found . Nine are of one type (alpha) . The other six include four different types (beta, beta', gamma and delta) which differ from each other and from the alpha genes to various degrees . Eleven of 15 genes have distinct flanking regions . Analysis of Neurospora 5S RNA showed that it consists of one principal species which matches the alpha-type gene sequence . Additional 5S species corresponding to the less abundant 5S gene types were also detected . The pattern of nucleotide substitutions between the predicted Neurospora 5S RNAs and between these and S . cerevisiae 5S RNA suggests that a particular 5S RNA secondary structure occurs in vivo and is conserved. Genetics, 1981 May, 98(1), 25 - 40 Mutants of yeast defective in sucrose utilization; Carlson M et al.; Utilization of sucrose as a source of carbon and energy in yeast (Saccharomyces) is controlled by the classical SUC genes, which confer the ability to produce the sucrose-degrading enzyme invertase (Mortimer and Hawthorne 1969) . Mutants of S . cerevisiae strain S288C (SUC2+) unable to grow anaerobically on sucrose, but still able to use glucose, were isolated . Two major complementation groups were identified: twenty-four recessive mutations at the SUC2 locus (suc2-); and five recessive mutations defining a new locus, SNF1 (for sucrose nonfermenting), essential for sucrose utilization . Two minor complementation groups, each comprising a single member with a leaky sucrose-nonfermenting phenotype, were also identified . The Suc2 mutations isolated include four suppressible amber mutations and five mutations apparently exhibiting intragenic complementation; complementation analysis and mitotic mapping studies indicated that all of the suc2 mutations are alleles of a single gene . These results suggest that SUC2 encodes a protein, probably a dimer or multimer . No invertase activity was detected in suc2 probably a dimer or multimer . No invertase activity was detected in suc2 mutants,--The SNF1 locus is not tightly linked to SUC2 . The snf1 mutations were found to be pleiotropic, preventing sucrose utilization by SUC2+ and SUC7+ strains, and also preventing utilization of galactose, maltose and several nonfermentable carbon sources . Although snf1 mutants thus display a petite phenotype, classic petite mutations do not interfere with utilization of sucrose, galactose or maltose . A common feature of all the carbon utilization systems affected by SNF1 is that all are regulated by glucose repression . The snf1 mutants were found to produce the constitutive nonglycosylated form of invertase, but failed to produce the glucose-repressible, glycosylated, secreted invertase . This failure cannot be attributed to a general defect in production of glycosylated and secreted proteins because synthesis of acid phosphatase, a glycosylated secreted protein not subject to glucose repression, was not affected by snf1 mutations . These findings suggest that the SNF1 locus is involved in the regulation of gene expression by glucose repression. Mutat Res, 1981 Apr, 81(2), 155 - 64 An unexpected response to Torulopsis glabrata fusion products to X-irradiation; Galeotti CL et al.; Intra-species fusion products of Saccharomyces cerevisiae, Saccharomyces unisporus and Torulopsis glabrata have been isolated following polyethylene glycol-induced fusion of protoplasts and selection for prototrophic colonies . Staining with lomofungin showed that all fusion products were uninucleate . Measurement of DNA content mostly gave values between haploid and diploid levels indicating that the majority of fusion products were aneuploid, Nevertheless fusion products of S . cerevisiae and S . unisporus were, as expected, more resistant to X-irradiation than their haploid parents . By contrast, the X-ray dose-response curve of all T . glabrata fusion products was indistinguishable from their progenitors despite the fact that mitotic segregants could be recovered amongst the survivors to X-rays . A possible explanation for the behaviour towards X-rays of T . glabrata fusion products is that this species lacks a DNA repair pathway involving recombination between homologous chromosomes . We conclude from this study that the shape of the X-ray dose-response curve should not be taken to indicate the ploidy of new yeast isolates without supporting data. Appl Environ Microbiol, 1981 Apr, 41(4), 992 - 9 Mutants of Saccharomyces cerevisiae and Candida utilis with increased susceptibility to digestive enzymes; Mehta RD et al.; Mutants of Candida utilis and a haploid strain of Saccharomyces cerevisiae were isolated, after ultraviolet light mutagenesis, which had increased sensitivities to snail gut enzymes (ses) . Three of the five S . cerevisiae mutants tested had increased sensitivities to porcine pepsin, all were more susceptible to a sequential treatment with pepsin, lipase, peptidase, and trypsin, four were sensitive to osmotic shock, and two had increased glucan/mannan ratios in their cell walls . All combinations of mutants showed positive complementation in heterozygous diploids, although complementation between one pair, which had the same phenotype, was incomplete, indicating that four to five different cistrons were involved . All mutations were found to be recessive . Haploid strains bearing pairs of ses mutations were not markedly more sensitive to mammalian digestive enzymes than strains with single mutations . Rat-feeding experiments with three mutants and the parental strains indicated that the protein was efficiently utilized in all cases . Net protein ratios for the two mutants of S . cerevisiae tested were slightly higher than that for their parent, but the differences were of marginal significance. Proc Natl Acad Sci U S A, 1981 Apr, 78(4), 2199 - 203 Fusion of Escherichia coli lacZ to the cytochrome c gene of Saccharomyces cerevisiae; Guarente L et al.; Hybrid genes between the Escherichia coli lacZ gene and the iso-1-cytochrome c (CYC1) gene of Saccharomyces cerevisiae were constructed by recombination in vitro . Each of the hybrid genes encodes a chimeric protein with a cytochrome c moiety at the amino terminus and an active beta-galactosidase (beta-D-galactoside galactohydrolase, EC 3.2.1.23) moiety at the carboxy terminus . When these hybrids are introduced into S . cerevisiae on plasmid vectors, they direct synthesis of beta-galactosidase . beta-Galactosidase levels directed by one such plasmid display the pattern of regulation normally seen for cytochrome c (i.e., a reduction of synthesis in cells grown in glucose) . This plasmid contains one codon of CYC1 fused to lacZ, and the fused gene is preceded by the 1100 nucleotides that lie upstream from CYC1 . An analysis of deletions in the upstream DNA suggests that sequences required for efficient transcription initiation of CYC1 lie within the DNA segment 250--700 base pairs upstream from the start of the CYC1 coding sequence . This region is at least 130 base pairs upstream from the "Hogness box" sequence that precedes the CYC1 coding sequence. J Biochem (Tokyo), 1981 Feb, 89(2), 523 - 9 Saturated fatty acid-starved cells of Saccharomyces cerevisiae grown in the presence of cerulenin and oleic acid; Otoguro K et al.; Cell growth of Saccharomyces cerevisiae ATCC 12341 inhibited by the antibiotic cerulenin, a specific inhibitor of fatty acid synthesis, was restored by oleic acid (18 : 1) to give saturated fatty acid-starved cells, which could not grow when again transferred into a fresh synthetic medium containing the antibiotic and oleic acid . The growth of the saturated fatty acid-starved cells was restored when they were transferred into a medium supplemented with myristic acid (14 : 0), pentadecanoic acid (15 : 0), and palmitic acid (16 : 0) in the presence of cerulenin and oleic acid . Cellular saturated fatty acid content in the growth-restored cells was also restored to about two-thirds of that of the normal yeast cells . The DNA, RNA, and cell wall synthetic capabilities of the saturated fatty acid-starved cells were almost normal, but the L-leucine uptake and cytochrome pattern were severely impaired . These impairments were reversed on supplying palmitic acid . The decrease of L-leucine uptake of the yeasts was also caused by the addition of cerulenin alone . However, since the decrease occurred later than the inhibition of fatty acid synthesis, it was considered to be a secondary effect . These results, obtained by using the saturated fatty acid-starved cells, indicate that the membranes of S . cerevisiae require certain amounts of saturated fatty acid and that the membrane functions (energy metabolism, transport, and so on) are impaired by starvation of saturated fatty acids. Int J Pept Protein Res, 1981 Feb, 17(2), 219 - 30 Synthesis of the dodecapeptide-alpha mating factor of Saccharomyces cerevisiae; Khan SA et al.; The synthesis of His-Trp-Leu-Gln-Leu-Lys-Pro-Gly-Gln-Pro-Met-Tyr, the dodecapeptide alpha-mating factor from Saccharomyces cerevisiae, and its Ala2- and Cha2-(beta-cyclohexylalanine) analogs are reported . Peptides were synthesized in solution using a combination of mixed anhydride and 1-hydroxybenzotriazole accelerated active ester coupling procedures . Dilute methanesulfonic acid (0.1-0.2 M) in methylene chloride-formic acid solution was employed to specifically remove the tert.-butoxycarbonyl group in the presence of the benzyloxycarbonyl group . Free peptides were obtained using catalytic transfer hydrogenation with formic acid as the hydrogen donor followed by mild acidolysis with trifluoroacetic acid . The alpha-factor and the Cha2-analog exhibited almost equal ability to cause "shmooing" of a-mating types of S . cerevisiae whereas the Ala2-analog exhibited no activity in this assay . These results differ with structure-activity studies reported on the tridecapeptide alpha-factor. J Gen Microbiol, 1981 Jan, 122(Pt 1), 101 - 7 Growth characteristics of Saccharomyces cerevisiae and Aspergillus nidulans when biotin is replaced by aspartic and fatty acids; Adler JH et al.; When either aerobic or anaerobic cultures of Saccharomyces cerevisiae were supplemented with aspartic and fatty acids in place of biotin, stationary phase populations were very small compared with those obtained in the presence of biotin . Similarly, these acids failed to fulfil the role of biotin-requiring strain of Aspergillus nidulans . Furthermore, a requirement for saturated fatty acid was found with anaerobically cultured S . cerevisiae . Cells were fragmented when biotin was replaced by aspartic and oleic acids alone, while cellular integrity was maintained, but with only slight growth, when biotin was replaced by oleic and palmitic acids together with aspartate . The importance of biotin in the growth of A . nidulans was particularly pronounced in the presence of glucose . In a medium containing glucose, growth ceased when biotin was replaced by aspartate and Tween 80 (a source of saturated and unsaturated fatty acids), but such replacement permitted a very small amount of growth to occur in the absence of glucose. Mol Gen Genet, 1981, 182(1), 65 - 9 The two methionine adenosyl transferases in Saccharomyces cerevisiae: evidence for the existence of dimeric enzymes; Cherest H et al.; In Saccharomyces cerevisiae either of the two genes SAM1 and SAM2 is able to produce a functional methionine adenosyl transferase (MATI and MATII) . In a wild-type strain, MATI and MATII are present in dimeric forms: MATI-MATI, MATII-MATII and perhaps MATI-MATII . A hypothesis is presented to explain the possible role of these different forms of methionine adenosyl transferase in S . cerevisiae. Ann N Y Acad Sci, 1981, 369, 321 - 34 Electrochemical measurements of cell populations; Sakato K et al.; Determination of cell growth was carried out by a polarographic system . The system was constructed of two platinum electrodes, a saturated calomel electrode, and a thermistor electrode . Responses of the system to the dissolved oxygen, pH, and temperature were examined . Cell growth of S . cerevisiae and M . olivoasterospora was monitored continuously by this system . In addition, this polarographic system could be applied to the measurements of cell populations of the human cancer cell L-1210 and mouse leukocytes . The measureable range for these animal cells was approximately 10(3)--10(5) cells/ml. Mutat Res, 1981 Jan, 80(1), 65 - 74 Extreme chemical mutagen sensitivity of respiratory adaptation in yeast; Pasupathy K et al.; The respiratory adaptation process (i.e . essentially mitochondrial biogenesis) in the cells of both wild-type Saccharomyces cerevisiae and strains sensitive to ultraviolet radiation (UV) undergoing transition from the anaerobic to the aerobic state (1-2 h aeration) could be arrested by a prior incubation for 15--30 min with several chemical mutagens and other DNA-acting chemicals at very low concentrations (10-7 to 10-6 M added to cells suspended at the density of 10(7) cells/ml) . At the same concentrations, these chemicals also inhibited DNA and RNA biosynthesis in maturing mitochondria during respiratory adaptation . This provides suggestive evidence for the view that the inhibitory effect of the chemical mutagens on respiratory adaptation could be due to lesions introduced into the DNA of promitochondria in the anaerobic cells . The system of respiratory adaptation in S . cerevisiae cells could serve as a rapid test for ascertaining the potentiality of a chemical to affect cellular DNA and probably, in turn, its potentiality to be mutagenic. Mol Gen Genet, 1981, 184(3), 394 - 9 Cloning of a eukaryotic regulatory gene; Losson R et al.; From a pool of hybrid plasmids carrying Sau3A fragments representing the entire yeast (S . cerevisiae) genome, a DNA fragment containing the regulatory gene PPRI was cloned by complementation of a non-inducible ppr1 mutation which confers to the cells an increased sensitivity to 6-azauracil . Cells containing the cloned DNA regained the ability to induce the synthesis of URA1 and URA3 gene products controlled by PPR1 . A physical map has been constructed and the study of subcloned restriction endonuclease fragments from the original yeast DNA fragment allowed us to localize the wile-type PPR1 regulatory gene within a 3 kilobase-pair region . The ppr1 RNA level was measured and the hybridization data indicate in a wild-type strain a low efficiency of transcription of PPR1 as compared to the structural URA3 gene, without effect of inducing conditions. Mol Gen Genet, 1981, 184(3), 386 - 93 Expression of the Herpes simplex virus thymidine kinase gene in Saccharomyces cerevisiae; McNeil JB et al.; Yeast plasmids have been constructed that carry the Herpes simplex Virus type 1 (HSV-1) thymidine kinase (TK) gene which is functionally expressed in Saccharomyces cerevisiae . The expression of the TK gene appears to be due to transcriptional read-through from a yeast promoter that lies on the 3' side of the HIS3 gene . The TK+ yeast possesses in vitro thymidine kinase activity which is absent in the original yeast strain . Yeast strains auxotrophic for thymidine monophosphate (dTMP) (tmp1) can grown on thymidine-containing medium after transformation with these plasmids . Tmp+, TK+ S . cerevisiae whose de novo synthesis of dTMP is inhibited with amethopterin plus sufanilamide is also capable of growth in thymidine . S . cerevisiae transformed with such plasmids is capable of incorporating thymidine and bromodeoxyuridine into DNA. Nucleic Acids Res, 1980 Dec 11, 8(23), 5725 - 37 Yeast histone mRNA is polyadenylated; Fahrner K et al.; Histone mRNA from S . cerevisiae has been identified and partially purified . The RNA is quantitatively retained on oligo (dT) cellulose or poly(U) sepharose as assayed by in vitro translation or hybridization of radiolabelled cloned yeast histone sequences to RNA immobilized on DBM paper . Retention of yeast histone mRNA on either of these chromatographic systems is most likely the result of polyadenylation since, when primed with oligo (dT), the RNA is an extremely good template for reverse transcriptase, as determined by hybrid arrest translation or by hybridization to D . melanogaster histone DNA sequences. Genetics, 1980 Dec, 96(4), 841 - 57 The effects of three PSO genes on induced mutagenesis : a novel class of mutationally defective yeast; Cassier C et al.; Reverse and forward mutation, induced by photoaddition of 8-methoxypsoralen (8-MOP) and 3-carbethoxypsoralen (3-CPs) or ultraviolet light (UV), are reduced in three pso mutants of Saccharomyces cerevisiae . The pso1-1 strain exhibits a lower frequency of spontaneous reversion (anti-mutator) and is almost entirely unaffected by the three agents in both the haploid and diploid states . The pso2-1 strain demonstrates very reduced frequencies of 8-MOP and 3-CPs plus 365 nm radiation-induced mutations in haploid and diploid cells . UV-induced mutation are slightly reduced, whereas survival is almost normal . The pso3-1 strain is mutable by 8-MOP and 3-CPs photoaddition only in the low-dose range . After UV treatment, survival of pso3-1 is nearly normal, whereas the frequencies of induced mutants are diminished as compared to the normal PSO+ . An analogue of adenine, 6-N-hydroxyaminopurine, is capable of inducing reversions in wild type, as well as in pso and rad6-1 mutant strains, indicating that this drug may act as a direct mutagen in yeast . The comparison of photoaddition of the bifunctional agent (8-MOP) to that of the monofunctional one (3-CPs) confirms that cross-links, as well as monoadditions, are mutagenic in S . cerevisiae . Repair, of the recombinational type, taking place in diploid cells or in haploid cells in G2 phase leads to higher survival, but appears to be error-free. Mutat Res, 1980 Dec, 73(2), 251 - 65 Genetic control of diploid recovery after gamma-irradiation in the yeast Saccharomyces cerevisiae; Saeki T et al.; Genetic mechanisms(s) of gamma-ray resistance of the diploid and budding haploid cells of S . cerevisiae were investigated, with special reference to mitotic recombination, by examining 11 rad mutant strains . The radiosensitivity of the diploid was markedly enhanced in certain gamma-ray-sensitive rad mutants, whereas the sensitivity of the haploid was not so enhanced in these rad mutants . These enhanced sensitivities of diploids were irrespective of their own haploid sensitivities . From these results, the existence of a mechanism of diploid-specific recovery was postulated . The magnitude of diploid radioresistance in rad mutants was positively correlated with the ability for the induction of mitotic recombinational events which were controlled by RAD genes belonging to the RAD-51 genetic pathway . The genetic mechanism(s) of the diploid recovery after gamma-irradiation are probably related to recombinational processes between the homologous chromosomes leading to reciprocal recombination or non-reciprocal gene conversion . Furthermore, the higher radioresistance of budding cells in comparison with the non-budding cells was also correlated to the diploid radioresistance with a few exceptions . Consequently, the mechanism(s) of budding radioresistance similar to the diploid recovery seems to be related to mitotic recombinational processes. Genetics, 1980 Nov, 96(3), 589 - 611 Recombination and chromosome segregation during the single division meiosis in SPO12-1 and SPO13-1 diploids; Klapholz S et al.; This paper reports a study of chromosome segregation and recombination during sporulation of spo12-1 and spo13-1 diploid strains of S . cerevisiae . These strains undergo a single division to form asci containing two diploid or near-diploid spores . The segregation of centromere-linked markers in the two-spored (dyad) products indicates that the division is generally equational . However, in a small percentage of the spo12-1 and spo13-1 cells, it appears that a meiosis I-like division occurs . Aberrant segregation of the MAT locus on chromosome III, yielding a monosomic and a trisomic spores pair, occurs in 12% of all dyads . The segregation patterns of markers at various distances from their centromeres and several pairs of markers on the same chromosome indicate that recombination takes place in both strains at nearly standard meiotic levels. Genetics, 1980 Nov, 96(3), 567 - 88 Isolation of SPO12-1 and SPO13-1 from a natural variant of yeast that undergoes a single meiotic division; Klapholz S et al.; ATCC4117 is a strain of S . cerevisiae that undergoes a single nuclear division during sporulation to produce asci containing two diploid ascopores (Grewal and Miller 1972) . All clones derived from these spores are sporulation-capable and, like the parental strain, form two-spored asci . In this paper, we describe the genetic analysis of ATCC4117 . In tetraploid hybrids of vegetative cells of the ATCC4117 diploid and a/a or alpha/alpha diploids, the production of two-spored asci is recessive . From these tetraploids, we have isolated two recessive alleles, designated spo12-1 and spo13-1, each of which alone results in the production of asci with two diploid or near-diploid spores . These alleles are unlinked and segregate as single nuclear genes . spo12-1 is approximately 22 cM from its centromere; spo13-1 has been localized to within 1 cM of arg4 on chromosome VIII . This analysis also revealed that ATCC4117 carries a diploidization gene allelic to or closely linked to HO, modifiers that reduce the number of haploid spores per ascus and alleles affecting the total level of sporulation. Arch Intern Med . 1980 Nov;140(11):1539. Saccharomyces cerevisiae septicemia; Eschete ML et al.; We report the first known case of septicemia caused by Saccharomyces cerevisiae . It occurred nosocomially in a hyperalimented burned man . It is a rare example of disease caused by S cerevisiae, which, like many saprophytes, can become pathogenic in the debilitated . The case is remarkable for its apparent origin in a bleeding esophageal lesion, for its clinical characteristics, including profound neutropenia, thrombocytopenia, hypothermia, and monocytopenia, and for its cure by amphotericin B. Cell, 1980 Nov, 22(2 Pt 2), 427 - 36 Mating signals control expression of mutations resulting from insertion of a transposable repetitive element adjacent to diverse yeast genes; Errede B et al.; ROAM mutations cause overproduction in S . cerevisiae . Overproduction of ROAM mutant gene products is less in MATa/MAT alpha diploid strains which cannot conjugate than in haplolid strains which can . Overproduction occurs in diploid strains capable of mating whether or not they are capable of sporulating . Overproduction decreases when haploid ROAM mutants also contain the ste7 mutation which prevents conjugation; other ste mutations do not affect the expression of ROAM mutations . Cloning of the ROAM mutant gene CYC7-H2 shows that a 5.5 kb sequence homologous to a transposable and reiterated Ty1 element is inserted in the 5' noncoding region of the CYC7 structural locus . The similar genetic properties of other ROAM mutations suggest that they each contain an inserted Ty element . These results also suggest that ROAM mutations respond to signals normally directed toward genes controlling conjugation functions, and that sequences present in Ty elements may be adjacent to structural loci and are the normal receptors for these signals. J Biol Chem, 1980 Oct 25, 255(20), 9828 - 37 Assembly of the mitochondrial membrane system . DNA sequence and organization of the cytochrome b gene in Saccharomyces cerevisiae D273-10B; Nobrega FG et al.; The mitochondrial genomes of cytoplasmic "petite" (rho-) mutants of Saccharomyces cerevisiae have been used to sequence the cytochrome b gene . A continuous sequence of 6.2 kilobase pairs has been obtained from 71.4 to 80.2 units of the wild type map . This region contains all the cytochrome b mutations previously assigned to the cob1 and cob2 genetic loci . Analysis of the DNA sequence has revealed that in the strain D273-10B, the cytochrome b gene is composed of three exons . The longest exon (b1) codes for the first 252 to 253 amino acids from the NH2-terminal end of the protein . The next two exons (b2 and b3) code for 16 to 18 and 115 to 116 amino acids, respectively . The complete cytochrome b polypeptide chain consists of 385 amino acids . Based on the amino acid composition, the yeast protein has a molecular weight of 44,000 . The three exon regions of the cytochrome b gene are separated by two introns . The intron between b1 and b2 is 1414 nucleotides long and contains a reading frame that is continuous with the reading frame of exon b1 . This intron sequence is potentially capable of coding for another protein of 384 amino acid residues . The second intron is 733 nucleotides long . This sequence is rich in A + T and includes a G + C cluster that may be involved in processing of the cytochrome b messenger . The organization of the cytochrome b region in S . cerevisiae D273-10B is somewhat less complex than has been reported for other yeast strains i which exon b1 appears to be further fragmented into three smaller exons. Eur J Biochem, 1980 Oct, 111(1), 17 - 31 A flavin-mononucleotide-binding site in Hansenula anomala nicked flavocytochrome b2, requiring the association of two domains; Gervais M et al.; Previous experiments in our laboratory with Saccharomyces cervisiae flavocytochrom b2 indicated that both fragments alpha and beta of the enzyme after cleavage by yeast proteases are required to form the flavin site . More detailed experiments have not been carried out on the nicked Hansenula anomala enzyme obtained by tryptic cleavage . A method has been devised that gives a quantitative separation in 4 M urea of beta, and alpha with its heme still bound . The characteristics of the various species: isolated alpha and beta and mixed alpha + beta were studied in 4 M urea and after elimination of this reagent by dialysis in the presence of FMN and 2-mercaptoethanol . Several methods, including heme spectroscopy, tryptophan fluorescence, sedimentation studies, and titration of bound flavin, were used . The results indicate that isolated alpha and beta have a folded globular structure after renaturation . The flavin binding to the alpha + beta mixture was important (50-100%) with recovery of the flavodehydrogenase activity . In contrast, binding was not detectable (< 0.5%, Kf > 10 mM) for isolated alpha and beta . As far as mononucleotide binding is concerned, such a cooperative requirement for two folding domains has never been reported in other enzymes . The present results are discussed together with others obtained in our laboratory which demonstrate that, as deduced from their sensitivity to trypsin, the structure of S . cerevisiae and H . anomala flavocytochrome b2 protomers is triglobular 'n-x-beta' (n and x combined within alpha) . The tetramer assembly, which remains intact as a nicked enzyme (alpha beta)4 after the first trypsin cleavage, is broken down following a second cleavage of the chain into four cytochrome cores (n) and a functional T-flavodehydrogenase entity, a tetramer of the type (x beta)4. Antimicrob Agents Chemother, 1980 Oct, 18(4), 593 - 7 Influence of extracellular K+ or Mg2+ on the stages of the antifungal effects of amphotericin B and filipin; Brajtburg J et al.; The macrolide heptaene amphotericin B (AmB) induced concentration-dependent effects on Saccharomyces cerevisiae which were separable into two distinct stages . At low concentrations the drug inhibited the growth of the yeast and reversible changed cell permeability to Na+ and K+ . At high levels it was lethal . The intracellular K+ concentration of cells with reversible damage (stage I) could be increased by addition of K+ to the medium, but cells irreversibly damaged (stage II) were not able to retain K+ . The addition of K+ to the medium did not influence the growth-inhibitory or killing action of AmB . Addition of Mg2+ to cultures increased S . cerevisiae resistance to the killing effects of AmB . At low concentrations of AmB, growth inhibition was also decreased by extracellular Mg2+, but at higher concentration of AmB, growth inhibition was increased, probably because the prevention by Mg2+ of the lethal effect allowed expression of the inhibitory effect in a greater range . Simultaneous addition of K+ and Mg2+ markedly decreased both the inhibitory and lethal action of AmB at all concentrations . Filipin, a pentaene macrolide, had only lethal effects, which were unaffected when K+ was added to the medium but were diminished when medium was supplemented with Mg2+. Boll Soc Ital Biol Sper, 1980 Sep 30, 56(18), 1803 - 6 Genetic effects of vinylcyclohexene diepoxide in yeast; Bronzetti G et al.; Using D7 strain of S . cerevisiae where we can consider three genetic effects such as mitotic gene conversion, mitotic cross over and reverse mutation we tested vinylcyclohexene diepoxide "in vitro" without metabolic activation . In this condition VCD is very toxic and induces both three genetic effects namely mitotic gene conversion, mitotic cross over and reverse mutation. J Bacteriol, 1980 Sep, 143(3), 1411 - 9 Changes in regulation of ribosomal protein synthesis during vegetative growth and sporulation of Saccharomyces cerevisiae; Pearson NJ et al.; When diploid Saccharomyces cerevisiae cells logarithmically growing in acetate medium were placed in sporulation medium, the relative rates of synthesis of 40 or more individual ribosomal proteins (r-proteins) were coordinately depressed to approximately 20% of those of growing cells . These new depressed rates remained constant for at least 10 h into sporulation . If yeast nitrogen base was added 4 yh after the beginning of sporulation to shift the cells back to vegetative growth, the original relative rates of r-protein synthesis were rapidly reestablished . this upshift in the rates occurred even in diploids homozygous for the regulatory mutation rna2 at the restrictive temperature for this mutation (34 degrees C) . However, once these mutant cells began to bud and grow at 34 degrees C, the phenotype of rna2 was expressed and the syntheses of r-proteins were again coordinately depressed . At least one protein whose rate of synthesis was not depressed by rna2 in vegetative cells did have a decreased rate of synthesis during sporulation . Another r-protein whose synthesis was depressed by rna2 maintained a high rate of synthesis at the beginning of sporulation . These data suggest that the mechanism responsible for coordinate control of r-protein synthesis during sporulation does not require the gene product of RNA2 and thus defines a separate mechanism by which r-proteins are coordinately controlled in S . cerevisiae. Eur J Biochem, 1980 Sep, 110(1), 107 - 14 Structure of the 5-S ribosomal RNA gene and its adjacent regions in Torulopsis utilis; Tabata S; A DNA segment spanning one repeating unit of ribosomal RNA(rRNA) genes in a yeast strain, Torulopsis utilis, has been cloned on a bacterial plasmid pBR322 . The size of the cloned segment was about Mr = 8.0 x 10(6) . All of the genes for the four species of rRNA were linked on it, and there was a long spacer between the 5-S and 18-S rRNA coding regions . The nucleotide sequences of the regions flanking the 5-S rRNA gene were determined and compared with those in the corresponding regions of Sacharomyces cerevisiae {Valenzuela, P., Bell, G . I., Masiarz, F . R., DeGennaro, L . J., and Rutter, W . J . (1977) Nature, 267, 641-643; Maxam A . M., Tizard, R., Skryabin, K . G., and Gilbert, W . (1977) Nature, 267, 643-645} . The sequence of the T . utilis 5-S rRNA is identical with that of S . cerevisiae except for two residues at positions 18 and 61 . However, its upstream region contained a quite different sequence, and a sequence which showed some homology was only found at positions -21 to -28 . The sequences were d(T-G-T-A-A-C-C-T) in T . utilis and d(T-A-T-C-A-C-C-T) in S . cerevisiae . Although the presence of various repeat sequences having the same or opposite directions was noted, these repeats occurred at different positions in the two yeast species . In the downstream region, the common sequence was only seven dT deoxynucleotides, which occurred immediately after the 5-S rRNA coding sequence . Significant direct and inverted repeat sequences were found in T . utilis, but such repeats are not seen in S . cerevisiae. J Bacteriol, 1980 Aug, 143(2), 621 - 7 Synthesis of beta-glucanases during sporulation in Saccharomyces cerevisiae: formation of a new, sporulation-specific 1,3-beta-glucanase; del Rey F et al.; A biphasic synthesis of 1,3-beta-glucanase occurred when cells of Saccharomyces cerevisiae AP-1 (a/alpha) were incubated in sporulation medium . The capacity to degrade laminarin increased very slowly during the first 7 h but at a much faster rate thereafter . Changes occurring during the first period were not sporulation specific since the moderate increase in activity against laminarin was insensitive to glutamine and hydroxyurea and also took place in the nonsporulating strain S . cerevisiae AP-1 (alpha/alpha) . However, the changes taking place after 7 h must be included in the group of sporulation-specific events since they were inhibited by glucose, glutamine, and hydroxyurea and did not occur in the nonsporulating diploid . Consequently, only when the cells had been incubated for at least 7 h in sporulation medium did full induction of activity against laminarin take place upon shift to a medium which favored vegetative growth . Changes in the relative proportions of the vegetative glucanases, namely, endo- and exo-1,3-beta-glucanase, and the formation of a new sporulation-specific 1,3-beta-glucanase account for the observed events and are the consequence of the expression of the sporulation program. J Bacteriol, 1980 Aug, 143(2), 1066 - 9 Separation of peptide transport and hydrolysis in trimethionine uptake by Saccharomyces cerevisiae; Parker DD et al.; Intact cells of Saccharomyces cerevisiae 139 hydrolyzed amino acid-p-nitroanilide by an activity similar to that of aminopeptidase II, as well-characterized external peptidase in yeast . In contrast, trimethionine, a model peptide used in transport assays, was not hydrolyzed by this aminopeptidase II-like activity, and the peptidase activity toward this substrate was localized in the soluble fraction of the yeast . We conclude that this tripeptide is taken up by S . cerevisiae intact and rapidly hydrolyzed inside the cell. Gut, 1980 Aug, 21(8), 643 - 9 Defective opsonisation and complement deficiency in serum from patients with fulminant hepatic failure; Wyke RJ et al.; Serum from 23 of 26 patients with fulminant hepatic failure and grade IV encephalopathy had defective opsonisation of E . coli and yeast (S . cerevisiae) . No toxic serum factors acting on the polymorphonuclear leucocytes or inactivators of the normal serum opsonisation factors were found . Complement deficiency was shown to be the most likely cause of the defect in opsonisation . The addition of a heat-labile fraction of normal serum at low concentration corrected the defect and factors of both the classical and the alternative pathways of complement were reduced to below 40% of the activity of the control serum . During the early stages of clinical recovery serum opsonisation and complement activity returned to normal with statistically significant correlations between tests of opsonisation and total haemolytic complement CH50, C3 and total alternative pathway activity . Defective serum opsonisation and complement deficiency represent major defects in the body's defences against infection. Proc Natl Acad Sci U S A, 1980 Aug, 77(8), 4559 - 63 Eukaryotic DNA segments capable of autonomous replication in yeast; Stinchcomb DT et al.; A selective scheme is presented for isolating sequences capable of replicating autonomously in the yeast Saccharomyces cerevisiae . YIp5, a vector that contains the yeast gene ura3, does not transform a ura3 deletion mutant to Ura+ . Hybrid YIp5-Escherichia coli DNA molecules also fail to produce transformants . However, collections of molecular hybrids between YIp5 and DNA from any of six eukaryotes tested (S . cerevisiae, Neurospora crassa, Dictyostelium discoideum Ceanhorabditis elegans, Drosophila melanogaster, and Zea mays) do transform the deletion mutant . The Ura+ transformants grow slowly, are unstable under nonselective conditions, and carry the transforming DNA as autonomously replicating, supercoiled circular molecules . Such a phenotype is qualitatively identical to that of strains transformed by molecules containing a yeast chromosomal origin of replication . Thus, these DNA hybrid molecules may contain eukaryotic origins of replication . The isolated sequences may be useful in determiing the signals controlling DNA replication in yeast and in studying both DNA replication and transformation in other eukaryotic organisms. Antimicrob Agents Chemother, 1980 Aug, 18(2), 226 - 30 Classification of polyene antibiotics according to their synergistic effect in combination with bleomycin A2 or fusidic acid; Akiyama S et al.; Five polyene antibiotics were compared for their effects on colony formation of either Chinese hamster V79 or Saccharomyces cerevisiae cells . A 10 to 40 times higher concentration of amphotericin B (heptaene) or nystatin (degenerated heptaene) was necessary to inhibit colony formation of hamster cells than that needed to inhibit colony formation of yeast cells . In contrast, colony formation of both hamster and yeast cells was inhibited to the same extent by similar concentrations of filipin (pentaene), pentamycin (pentaene), or pimaricin (tetraene) . The five polyene antibiotics were also compared for their effects on colony formation of either V79 or S . cerevisiae cells when combined with a nonpolyene antibiotic, fusidic acid or bleomycin A2 . Amphotericin B or nystatin could augment the cytocidal effect of fusidic acid but not that of bleomycin A2, whereas pentamycin or pimaricin could augment the cytocidal effect of both fusidic acid and bleomycin A2 against hamster and yeast cells . Filipin was found to enhance the action of fusidic acid and bleomycin upon growth of mammalian cells, whereas the pentaene polyene significantly potentiated the action of fusidic acid, but not that of bleomycin A2, against S . cerevisiae . It was therefore suggested that these polyene antibiotics be classified into two groups: group 1 (pimaricin, pentamycin, and filipin) and group 2 (amphotericin B and nystatin). Genetics, 1980 Jul, 95(3), 579 - 88 The selection of amber mutations in genes required for completion of start, the controlling event of the cell division cycle of S . cerevisiae; Reed SI; Using a modification of a procedure developed for the isolation of temperature-sensitive mutants defective in the start event of cell division, amber mutations were obtained for two Class-I start genes, cdc28 and cdc37 . Genetic analysis demonstrated that co-segregation of an amber suppressor with such alleles was required for viability of spores subsequent to meiosis . These mutations are expected to be useful in the identification of the molecular products of the genes cdc28 and cdc37. Genetics, 1980 Jul, 95(3), 561 - 77 The selection of S . cerevisiae mutants defective in the start event of cell division; Reed SI; Thirty-three temperature-sensitive mutations defective in the start event of the cell division cycle of Saccharomyces cerevisiae were isolated and subjected to preliminary characterization . Complementation studies assigned thes mutations to four complementation groups, one of which, cdc28, has been described previously . Genetic analysis revealed that these complementation groups define single nuclear genes, unlinked to one another . One of the three newly identified genes, cdc37, has been located in the yeast linkage map on chromosome IV, two meiotic map units distal to hom2.--Each mutation produces stage-specific arrest of cell division at start, the same point where mating pheromone interrupts division . After synchronization at start by incubation at the restrictive temperature, the mutants retain the capacity to enlarge and to conjugate. J Bacteriol, 1980 Jul, 143(1), 176 - 81 Choline transport in Saccharomyces cerevisiae; Hosaka K et al.; Choline transport of Saccharomyces cerevisiae was measured by the filtration method with the use of glass microfiber paper . The uptake was time and temperature dependent . The kinetics of choline transport showed Michaelis behavior; an appearent Km for choline was 0.56 microM . N-Methylethanolamine, N,N-dimethylethanolamine, and beta-methylcholine were competitive inhibitors of choline transport, with Ki values of 40.1, 3.1, and 6.9 microM, respectively . Ethanolamine, phosphorylcholine, and various amino acids examined had no effect . Choline transport required metabolic energy; removal of glucose resulted in a great loss of transport activity, and the remaining activity was abolished by 2,4-dinitrophenol, carbonyl cyanide p-trifluoromethoxyphenyl hydrazone, arsenate, and cyanide . External Na+ was not required, and the transport was not effected by ionophores, valinomycin, and gramicidin D . These results indicate that S . cerevisiae possess an active choline transport system mediated by a specific carrier . This view is further supported by the isolation and characterization of a choline transport mutant . The choline transport activity in this mutant was very low, whereas the transport of L-leucine, L-methionine, D-glucose, and myo-inositol was normal . Together with the choline transport mutant, mutants defective in choline kinase were also isolated. Boll Soc Ital Biol Sper, 1980 Jun 30, 56(12), 1315 - 21 {Use of the D7 strain of S . cerevisiae in the determination of environmental risk . 1 . Genetic effects of trichloroethylene}; Bronzetti G et al.; Trichloroethylene (TCE) was tested for its ability to induce both point mutation and mitotic gene conversion in diploid strain of yeast . S . cerevisiae (strain D7) was tested for both activities in culture with and without a mammalian microsomal activation system and intrasanguinous host-mediated assay in mice . In suspension test with D7, TCE was genetically active only with microsomal activation . In vivo TCE induced both point mutation and gene conversion in D7 and gene conversion in D4 when recovered from the liver and kidneys after both acute and subacute dosing . Yeasts recovered from the lungs showed little, if any, increase in genetic effects. Mutat Res, 1980 Jun, 71(1), 77 - 89 Yeast mitochondrial deoxyribonuclease stimulated by ethidium bromide . III . Possible invovlement in the induction of "petite" mutation by phenanthridinium derivatives; Jacquemin-Sablon H et al.; We previously described a yeast-mitochondrial deoxyribonuclease (EtdBr DNAase), whose activity is stimulated by ethidium bromide . In this paper, we have compared the ability of a series of phenanthridinium derivatives to activate the EtdBr DNAase "in vitro" and their efficiency in inducing "petite" mutants in the yeast S . cerevisiae . Kinetics studies, in the absence or the presence of SDS, were first carried out to compare the penetration rates of the various compounds . Dose--response curves were then established to quantify their mutagenic efficiencies . From these data, a linear correlation was established between the level of EtdBr DNAase activation produced by a drug and its mutagenic efficiency, thus demonstrating that the two processes display similar drug-structural requirements . These results suggest that the EtdBr DNAase might be involved in the induction of petite mutations by these derivatives. Eur J Biochem, 1980 Jun, 107(2), 501 - 4 Direct oxidation of NADPH by submitochondrial particles from Saccharomyces cerevisiae; Djavadi FH et al.; It has been accepted that in Saccharomyces cerevisiae submitochondrial particles do not oxidize the NADPH and that the NADPH:cytochrome c reductase is not a mitochondrial enzyme but rather a microsomal one . The present study provides clear evidence that in S . cerevisiae a direct oxidation of NADPH occurs through the mitochondrial electron transport system . The following results wee obtained: submitochondrial particles from S . cerevisiae are capable of oxidizing NADPH with a relatively high rate . The oxidation of NADPH is sensitive to antimycin A and NaN3 but insensitive to rotenone as is known for NADPH oxidation . Also NADPH:cytochrome c reductase activity is inhibited by antimycin A . NADPH-induced reduction of cytochromes b, c + c1, and aa3 is as fast as NADPH-induced reduction . Cytochromes are reduced to the same extent with either NADH or NADPH . The changes of the ratio of NADH/NADPH oxidation rate and the ratio of NADH K3Fe(CN)6/NADPH-K3Fe(CN)6 reductase activities at various phases of growth suggest that two distinct pyridine nucleotide dehydrogenases could be responsible for NADH and NADPH oxidation . This problem remains to be elucidated. Mutat Res, 1980 Apr, 77(4), 341 - 4 {Effect of smoking-machine parameters on the genetoxic activity of cigarette gas phase, estimated on human lymphocyte and yeast (author's transl)}; Izard C et al.; Cigarette smoke used in chemical research and bioassays is obtained by mechanical smoking on machines adjusted to international standards . On studying the behavior of some smokers of black tobacco, we were led to change the standard parameters: volume, duration, frequency . The gas phase obtained under those new conditions is poorer in some components . This decrease goes with a clear-cut decrease of its genotoxic activity towards cultured human lymphocytes (sister-chromatid exchange frequency) and S . cerevisiae (rate of mitotic recombinants and of respiratory deficients) . This investigation emphasizes the leading part of the smoking behavior. Biochim Biophys Acta, 1980 Mar 27, 597(1), 125 - 36 Uptake of the lipophilic cation dibenzyldimethylammonium into Saccharomyces cerevisiae . Interaction with the thiamine transport system; Barts PW et al.; The distribution ratio of the lipophilic cation dibenzyldimethylammonium between the cells of Saccharomyces cerevisiae and the medium appears to reflect changes in the membrane potential in a way that is qualitatively correct: the addition of a proton conductor or of an agent which blocks metabolism causes an apparent depolarization of the cell membrane; monovalent cations cause also a lowering of the equilibrium distribution, whereas the addition of divalent cations results in an increase of the partition ratio . However, uptake of dibenzyldimethylammonium and probably also of other liophilic cations proceeds via the thiamine transport system of the yeast . Dibenzyldimethylammonium transport is inducible, like thiamine transport . A kinetic analysis of the mutual interaction between thiamine and dibenzyldimethylammonium uptake shows that these compounds share a common transport system; moreover, dibenzyldimethylammonium uptake is inhibited complete by thiamine disulfide, a competitive inhibitor of thiamine transport and dibenzyldimethylammonium uptake in a thiamine-transport mutant is reduced considerably . It is concluded that one should be cautious when using lipophilic cations to measure the membrane potential of cells of S . cerevisiae. J Biol Chem, 1980 Mar 25, 255(6), 2569 - 77 Formyl-methenyl-methylenetetrahydrofolate synthetase(combined) from yeast . Biochemical characterization of the protein from an ade3 mutant lacking the formyltetrahydrofolate synthetase function; de Mata ZS et al.; A protein from Saccharomyces cerevisiae mutant ade3-1050, a formyltetrahydrofolate synthetase-deficient mutant, has been purified to apparent homogeneity . The purified mutant enzyme shows both methylenetetrahydrofolate dehydrogenase and methenyltetrahydrofolate cyclohydrolase activities, but lacks formyltetrahydrofolate synthetase activity . The biochemical characterization of the mutant protein described in this paper is consistent with genetic data which indicate that the 1050 mutation is a point mutation at the ade3 locus of chromosome VII of S . cerevisiae . The molecular weight of the native mutant protein (Mr = 227,000 by exclusion chromatography), as well as the number and size of its subunits are exactly the same as those of the trifunctional wild type enzyme . In addition, both proteins have the same sedimentation behavior in a glycerol density gradient (s20,w = 9.4 S), and their activities and structures are equally affected by exposure to mild tryptic degradation . ATP protects both enzymes from tryptic degradation, but NADP+ does not . Some of the kinetic properties of the activities of both enzymes were also determined and were essentially similar . Although both enzymes require the presence of metals for maximal synthetase and dehydrogenase activities, metals are not necessary to maintain their structures intact. Nucleic Acids Res, 1980 Mar 11, 8(5), 1043 - 59 Molecular cloning of the actin gene from yeast Saccharomyces cerevisiae; Gallwitz D et al.; Two overlapping DNA fragments from yeast Saccharomyces cerevisiae containing the actin gene have been inserted into pBR322 and cloned in E.coli . Clones were identified by hybridization to complementary RNA from a plasmid containing a copy of Dictyostelium actin mRNA . One recombinant plasmid obtained (pYA102) contains a 3.93-kb Hindlll fragment, the other (pYA208) a 5.1-kb Pstl fragment, both share a common 2.2-kb fragment harboring part of the actin gene . Cloned yeast actin DNA was identified by R-loop formation and translation of the hybridized actin mRNA and by DNA sequence analysis . Cytoplasmic actin mRNA has been estimated to be about 1250 nucleotides long . There is only one type of the actin gene in S.cerevisiae. Nucleic Acids Res, 1980 Mar 11, 8(5), 1009 - 22 Hybridizable sequences between cytoplasmic ribosomal RNAs and 3 micron circular DNAs of Saccharomyces cerevisiae and Torulopsis glabrata; Clark-Walker GD et al.; We have shown that 2.8 and 3.1 micron circular DNA molecules, previously reported to be present in Saccharomyces cerevisiae and Torulopsis glabrata respectively, contain sequences hybridizing to cytoplasmic ribosomal RNAs . In S . cerevisiae the 2.8 micron circular DNA appears to be identical to the rDNA repeating unit from nuclear DNA, both in length (approximately 9000 base pairs) and in the location of the 25, 18 and 5.8S rRNA sequences on the large HindIII fragment (6500 bp) and the presence of the 5S rRNA sequence on the small HindIII fragment . The 3.1 micron molecule from T . glabrata is approximately 2000 base pairs longer than the S . cerevisiae molecule and in addition, one of the HindIII sites lies within the region hybridizing to 25, 18 and 5.8S rRNAs . In S . cerevisiae the 4-5 copies of the 2.8 micron circular DNA molecules per cell, which have an extra-nuclear location, do not appear to be essential for cell viability as in one strain they were undetectable. Genetics, 1980 Mar, 94(3), 555 - 80 Structural analysis of the dur loci in S . cerevisiae: two domains of a single multifunctional gene; Cooper TG et al.; In Saccharomyces cerevisiae, the degradation of urea to carbon dioxide and ammonia is catalyzed by urea carboxylase and allophanate hydrolase . The loci coding for these enzymes (dur1 and dur2) are very tightly linked on the right arm of chromosome II between pet11 and met8 . Pleiotropic mutations that fail to complement mutations in either of the dur loci were found to be predominantly located in or near the dur2 locus . We interpret these data as suggesting that the two dur loci might in reality be domains of a single gene that codes for a multifunctional polypeptide . In view of this conclusion, we have renamed the dur loci as the dur1,2 locus. Nucleic Acids Res, 1980 Feb 11, 8(3), 467 - 85 More ribosomal spacer sequences from Xenopus laevis; Moss T et al.; The base sequence analysis of a Xenopus laevis ribosomal DNA repeat (7) has been extended to cover almost the entire non-transcribed and external transcribed spacer . A compilation of these sequences is presented . All the repetitive and non-repetitive sequence elements of the spacer are identified and their evolution discussed . Comparison of the X.laevis and S.cerevisiae (25,26) ribosomal DNAs shows about 80% sequence conservation in the 18S gene but no sequence conservation, from the available data, in the external transcribed spacer . The sequence coding for the 3' terminus of the X.laevis 40S ribosomal precursor RNA is presented and its structural features analyzed. Cell, 1980 Feb, 19(2), 403 - 14 Translational analysis of the killer-associated virus-like particle dsRNA genome of S . cerevisiae: M dsRNA encodes toxin; Bostian KA et al.; The M species (medium sized) dsRNA (1.1-1.4 x 10(6) daltons) isolated from a toxin-producing yeast killer strain (K+R+) and three related, defective interfering (suppressive) S species dsRNAs of the yeast killer-associated cytoplasmic multicomponent viral-like particle system were analyzed by in vitro translation in a wheat germ cell-free protein synthesis system . Heat-denatured M species dsRNA programmed the synthesis of two major polypeptides, M-P1 (32,000 daltons) and M-P2 (30,000 daltons) . M-P1 has been shown by the criteria of proteolytic peptide mapping and cross-antigenicity to contain ihe 12,000 dalton polypeptide corresponding to the in vivo produced killer toxin, thus establishing thiat it is the M species dsRNA which carries the toxin gene . An M species dsRNA obtained from a neutral strain (K-R+) also programmed the in vitro synthesis of a polypeptide identical in molecular weight to M-P1, thus indicating that the cytoplasmic determinant of the mutant neutral phenotype is either a simple point mutation in the dsRNA toxin gene or a mutation in a dsRNA gene which is required for functional toxin production . In vitro translation of each of the three different suppressive S dsRNAs resulted in the production of a polypeptide (S-P1) of approximately 8000 daltons instead of the 32,000 dalton M-P1 polypeptide programmed by M dsRNA . This result is consistent with the heteroduplex analysis of these dsRNAs by Fried and Fink (1978), which shows retention of M dsRNA ends, accompanied by large internal deletions in each of the S dsRNAs translated. Z Allg Mikrobiol, 1980, 20(10), 641 - 52 {Cell electrophoretical characterization of the surface of Candida guilliermondii}; Lerche KH et al.; The electrical properties of the outer layer of the cell wall of a hydrocarbon-grown yeast C . guilliermondii were studied in detail by cell electrophoresis . Some experiments were also made with the yeast S . cerevisiae . The mobilities of the yeasts were measured as a function of pH at pH 2-11.5 and constant ionic strength I = 0.02 mol/l . For identification of surface groups the pH-mobility curves are used to calculate pK-values . The results indicate the presence of amino and carboxyl groups on the surface of C . guilliermondii . These groups are probably a part of a glyco-protein with an isoelectric point at pH 3.3 located on the surface . Electrophoresis of droplets of mineral oil coated with adsorbed protein layer confirms these conclusions . The importance of this glycoprotein in hydrocarbon uptake is discussed. Mol Gen Genet, 1980, 177(4), 581 - 8 Analysis of rho mutability in Saccharomyces cerevisiae . I . Effects of mmc and pet-ts alleles; Marmiroli N et al.; Two additional types of nuclear determinants involved in the control of spontaneous mutability of rho in S . cerevisiae have been identified: mmc and the pet-ts 1, 2, 10, 52 and 53 genes . These genes in their mutated recessive form increase at various extents the number of respiratory deficient cytoplasmic "petite" mutants accumulated . The gene mmc does not affect the respiratory activity and is not temperature-dependent whereas the pet-ts genes determine at the non permissive temperature a respiratory deficient phenotypes even if they affect the mutability of rho at the permissive and at the non permissive temperature . The data here reported suggest that a "replicative complex" exists for the mitochondrial DNA . It is in the purpose of this paper to deal with the relative contribution that mmc and pet-ts gene products have in ensuring the fidelity of this "replicative complex". Birth Defects Orig Artic Ser, 1980, 16(1), 179 - 93 Towards enzyme replacement in GM2 gangliosidosis: organ disposition and induced central nervous system uptake of human beta-hexosaminidase in the cat; Rattazzi MC et al.; The rapid plasma clearance of human placental beta-hexosaminidase in the cat is due mainly to a receptor-mediated mechanism recognizing terminal N-acetyl glucosaminyl and mannosyl residues on glycoproteins . Using a sensitive single radial immunodiffusion assay, specific for human beta-hexosaminidase, we have shown that, in normal cats, the liver is responsible for most of the clearance of human beta-hexosaminidase . Two hours after injection of approximately 6 X 10(6) U beta-hexosaminidase/kg bw, 70-90% of the enzyme was recovered in the liver . Spleen, kidney, lung, bone, bone, pancreas, adrenals, testes and ovaries, cardiac and skeletal muscle, lymph nodes, and placenta, however, also participated in the clearance, although specific uptake in most organs was < 5% of that of liver . Exogenous beta-hexosaminidase was also present in bile, indicating that the hepatocytes are involved in clearance . Injection of terminal mannose-rich S . cerevisiae mannans (50-150 mg/kg bw), prolonged the plasma half-life of the enzyme (t 1/2 up to 290 min) . In these animals, beta-hexosaminidase uptake by liver was reduced to < 10% of controls but uptake by other organs was not proportionally or uniformly reduced, suggesting the existence of different uptake mechanisms in different tissues . Permeability of the blood-brain barrier was induced by exposing cats to 100% O2 at 2.5 ATA for 90 min . Injection of 6 X 10(6) U beta-hexosaminidase/kg bw during or immediately after exposure resulted in apparent uptake of enzyme by nervous tissue, qualitatively detectable by immunologic methods, but below the limits of sensitivity of the radial immunoassay(ie < 150 U/gr) . When enzyme uptake by liver was inhibited by injection of ovomucoid or mannans, however, the hyperbaric oxygen-induced apparent uptake of beta-hexosaminidase by brain, cerebellum, and spinal cord was 200-500 U/gr of blood-free tissue, suggesting that the transport mechanism involved (presumably at the level of the nervous system vascular endothelium) is different from the carbohydrate-dependent hepatic uptake . The mechanism by which hyperbaric oxygenation induces permeability of the blood-brain barrier is not clear . The combination of this procedure (routinely used in human therapy) with specific inhibition of hepatic uptake, however, appears to be a promising approach for lysosomal enzyme targeting to the central nervous system. Genetics, 1979 Dec, 93(4), 877 - 901 A suppressor of mating-type locus mutations in Saccharomyces cerevisiae: evidence for and identification of cryptic mating-type loci; Rine J et al.; A mutation has been identified that suppresses the mating and sporulation defects of all mutations in the mating-type loci of S . cerevisiae . This suppressor, sir1-1, restores mating ability to mat alpha 1 and mat alpha 2 mutants and restores sporulation ability to mat alpha 2 and mata1 mutants . MATa sir1-1 strains exhibit a polar budding pattern and have reduced sensitivity to alpha-factor, both properties of a/alpha diploids . Furthermore, sir1-1 allows MATa/MATa, mat alpha 1/mat alpha/, and MAT alpha/MAT alpha strains to sporulate efficiently . All actions of sir1-1 are recessive to SIR1 . The ability of sir1-1 to supply all functions necessary for mating and sporulation and its effects in a cells are explained by proposing that sir1-1 allows expression of mating type loci which are ordinarily not expressed . The ability of sir1-1 to suppress the mat alpha 1-5 mutation is dependent on the HMa gene, previously identified as required for switching of mating types from a to alpha . Thus, as predicted by the cassette model, HMa is functionally equivalent to MAT alpha since it supplies functions of MAT alpha . We propose that sir1-1 is defective in a function . Sir ("Silent-information regulator"), whose role may be to regulate expression of HMa and HM alpha. Tsitologiia, 1979 Dec, 21(12), 1403 - 10 {Cytochemical and biochemical determination of acid phosphatase activity in yeasts}; Rainina EP et al.; Optimal conditions of the cytochemical assay for acid phosphatase in protoplasts and whole cells of S . cerevisiae have been described . Dimethyl sulfoxide was used to increase the permeability of the yeast cell envelope . In the yeast cells, grown up to the end of the exponential phase, acid phosphatase is shown to be located mainly in the central vacuole and on the cell envelope surface . A considerable activity of acid phosphatase is demonstrable on the surface of the plasma membrane and within adjacent vesicles that represent, presumably, part of the endoplasmic reticulum . Acid phosphatase can be considered as a marker enzyme for yeast cell vacuoles. Mol Gen Genet, 1979 Nov, 176(3), 393 - 8 Ozone response in wild type and radiation-sensitive mutants of Saccharomyces cerevisiae; Dubeau H et al.; The effect of ozone exposure on Saccharomyces cerevisiae was studied . Factors such as ozone concentration, treatment time, media, initial cell concentration and growth phase were shown to influence ozone response in this organism . Logarithmic phase cells were much more sensitive than stationary phase cells to the lethal effect of ozone . The radiation-sensitive mutants rad3, rad6, rad51 and rad52 of S . cerevisiae were exposed, in water, to 50 ppm of ozone for 30 min . On comparing their survival curves, the rad51 and the rad52 mutants showed a greater sensitivity to ozone exposure than the wild type. Cell, 1979 Nov, 18(3), 623 - 35 Recovery of S . cerevisiae a cells from G1 arrest by alpha factor pheromone requires endopeptidase action; Ciejek E et al.; Radioactive alpha factor is degraded to discrete biologically inactive fragments by the target a cells of S . cerevisiae, but not by alpha cells which make the pheromone . The pattern of cleavage products and sequence analysis of one fragment indicated that the first scission occurred between leucine 6 and lysine 7 . The protease inhibitors tosyl-L-argininyl-methyl ester (TAME), tosyl-L-lysyl-chloromethylketone (TLCK) and N-acetyl-L-leucyl-L-leucyl-L-argininal (leupeptin) markedly prolonged the period of G1 arrest in a cells exposed to alpha factor, while other standard protease inhibitors had little or no effect . The presence of TAME and leupeptin, or TLCK, reduced the rate of degradation of radioactively labeled alpha factor by a cells . Intact yeast cells have apparent esterase and amidase activities that are blocked by the same spectrum of inhibitors that potentiate alpha factor action . Purified alpha factor is a competitive inhibitor of these hydrolytic activities . The activities are present in yeast mutants which have greatly reduced levels of the three major vacuole-associated proteases (A, B and C) or which carry an ochre mutation in the major neutral protease (B) . These observations indicate that the inactivation of alpha factor is due to endoproteolytic cleavage, the destruction of the pheromone is required to overcome its effects on growth and that degradation of the molecule may involve surface bound endopeptidase(s). J Bacteriol, 1979 Oct, 140(1), 73 - 82 Chimeric plasmids for cloning of deoxyribonucleic acid sequences in Saccharomyces cerevisiae; Storms RK et al.; Two sets of plasmids, each carrying a Saccharomyces cerevisiae gene and a portion or all of the yeast 2-micron circle linked to the Escherichia coli plasmid pBR322, have been constructed . One of these sets contains a BamHI fragment of S . cerevisiae deoxyribonucleic acid that includes the yeast his3 gene, whereas the other set contains a BamHI fragment of S . cerevisiae that includes the yeast leu2 gene . All plasmids transform S . cerevisiae and E . coli with a high frequency, possess unique restriction endonuclease sites, and are retrievable from both host organisms . Plasmids carrying the 2.4-megadalton EcoRI fragment of the 2-micron circle transform yeast with 2- to 10-fold greater frequency than those carrying the 1.5-megadalton EcoRI fragment of the 2-micron circle . Restriction endonuclease analysis of plasmics retrieved from S . cerevisiae transformed with plasmics carrying the 2.4-megadalton EcoRI fragment showed that in 13 of 96 cases the original plasmic has acquired an additional copy of the 2-mcron circle . These altered plasmids appear to have arisen by means of an interplasmid recombination event while in S . cerevisiae . A clone bank of S . cerevisiae genes based upon one of these composite plasmids has been constructed . By using this bank and selecting directly in S . cerevisiae, the ura3, tyr1, and met2 genes have been cloned. Cell, 1979 Oct, 18(2), 309 - 19 Isolation of a circular derivative of yeast chromosome III: implications for the mechanism of mating type interconversion; Strathern JN et al.; We describe genetic and physical characterization of rearrangements of chromosome III which result in changes of cell type in S . cerevisiae . Two types of rearrangements were obtained as rare events which caused a change at the locus controlling cell type, MAT, associated with a recessive lethal mutation, in one case from MATalpha to MATa-lethal, and in the other case from MATa to MATalpha-lethal . The MATa-lethal mutation is a deletion on the right arm of chromosome III, which we demonstrate extends to (or near) HMalpha . We suggest this deletion removes MATalpha and activates cryptic MATa information stored in HMalpha as proposed in the cassette model of mating type interconversion . The MATalpha-lethal mutation is the result of the formation of a circular chromosome III, which we interpret to remove MATa and activate the cryptic MATalpha information stored at HMa . Strains carrying the MATalpha-lethal chromosome contain a circular chromosome of length 62.6 plus or minus 5.7 mum, which is absent in related strains . This chromosome was confirmed to be chromosome III by hybridization of specific yeast DNA fragments to supercoiled DNA obtained from MATalpha-lethal strains . The isolation of a large circular derivative of chromosome III allows correlation of genetic and physical distance based on large distances-1 centimorgan corresponds to approximately 2700 base pairs. Cell, 1979 Sep, 18(1), 47 - 53 Assembly of the mitochondrial membrane system: sequences of yeast mitochondrial valine and an unusual threonine tRNA gene; Li M et al.; The mitochondrial DNA segments of two independently isolated rho- clones of S . cerevisiae carrying a genetic marker for a threonine tRNA have been characterized by restriction endonuclease analysis and DNA sequencing . The DNA sequences of the two segments have been used to deduce the primary and secondary structures of the tRNA . The threonine tRNA is unusual in having a leucine anticodon (3'-GAU-5') . Despite the anomalous anticodon, the tRNA is proposed to function in mitochondrial protein synthesis . One of the rho- clones contains an additional coding sequence that has been identified as a valine tRNA genes have been located on the wild-type physical map and determined to be transcribed from two different strands. Cell, 1979 Sep, 18(1), 27 - 35 Splicing of yeast tRNA precursors: a two-stage reaction; Peebles CL et al.; Soluble extracts of S . cerevisiae splice tRNA precursors which contain intervening sequences . The reaction goes to completion and requires ATP for the production of mature sequence tRNA . In the absence of ATP, half-tRNA molecules accumulate . Similar half-tRNA molecules appear as kinetic intermediates and accumulate if splicing is inhibited with pure, mature tRNA . Half-tRNA molecules have been purified . These half-tRNAs are efficiently ligated in an ATP-dependent reaction that is inhibited by added mature tRNA . The product of ligation is the expected mature sequence tRNA . The excised intervening sequence has also been identified . These results suggest an enzymatic mechanism for splicing which involves two independent steps. Cell, 1979 Sep, 18(1), 11 - 26 A precursor to a minor species of yeast tRNASer contains an intervening sequence; Etcheverry T et al.; Certain tRNAs in S . cerevisiae (tRNATyr and tRNAPhe) arise via precursor molecules which are mature at the 5' and 3' termini but contain intervening sequences adjacent to the anticodon (Knapp et al., 1978; O'Farrell et al., 1978) . In addition to these molecules, precursors to several other tRNAs accumulate in a temperature-sensitive mutant (ts136) at the nonpermissive temperature . We have analyzed one of these species and shown that it is a precursor to a minor species of tRNASer . This precursor is also mature at both termini and contains an intervening sequence of 19 nucleotides adjacent to the hypermodified A residue 3' to the anticodon . The sequence can be arranged in a secondary structure in which the anticodon stem is extended by additional base-pairing, and contains the sites of excision and ligation within two looped regions . Support for this structure was provided by analysis of the products of limited digestion with RNAase T1 . recently Piper (1978) reported the isolation of a minor species of tRNASer which decodes UCG . He found this species to be structurally heterogeneous and determined that the less abundant form corresponds to the tRNA which is altered in the recessive lethal SUP-RL1 amber suppressor . Our data now suggest that the more abundant form may be restricted to reading UCA in vivo; thus mutation of the minor species would result in complete loss of UCG-decoding ability and explain the recessive lethality of SUP-RL1 . We have shown that the precursor which accumulates in ts136 corresponds exclusively to this minor tRNASerUCG species . Our results suggest that this may be the only gene for tRNASer in yeast which contains an intervening sequence. Mol Gen Genet, 1979 Aug, 175(1), 1 - 4 Two isoaccepting seryl tRNAs coded by separate mitochondrial genes in yeast; Colletti E et al.; In S . cerevisiae four isoacceptor mitochondrial tRNAs for serine have been separated by reversed phase chromatography . At least two of these species are products of different genes . In this work the deletion mapping technique has been used to locate two genes for tRNAser . The gene for tRNAser previously localized in the oli I region of the mitochondrial genome has been found to code for tRNAser2, and another gene coding for tRNAser1 has been detected in the region where most of other tRNA genes are found . Results of fine mapping experiments allowed to localize this gene in the proximity of the gene for tRNAarg. Mol Gen Genet, 1979 Jul 24, 174(3), 335 - 7 The nucleotide sequence of the mitochondrial genome of a spontaneous "petite" mutant of yeast; Gaillard C et al.; The nucleotide sequence of the repeat unit of the mitochondrial genome of a spontaneous petite mutant of S . cerevisiae is reported . The sequence provides direct information on the AT-spacers and GC-clusters of the mitochondrial genome of yeast. Genetics, 1979 Jul, 92(3), 803 - 21 Mapping chromosomal genes of Saccharomyces cerevisiae using an improved genetic mapping method; Wickner RB; A triploid (3n) strain of Saccharomyces cerevisiae was constructed carrying a standard marker on each of chromosomes 1 through XVII in the -/+/+ configuration . This is called a "supertriploid." Meiotic spores from this strain (n + approximately n/2) were mated with a haploid (n) carrying an unmapped mutation . Meiotic analysis of each zygote clone (2n + approximately n/2) produced in this way resulted in elimination of an average of 4.2 chromosomes as the possible location of the unmapped marker . The distribution of extra chromosomes in the 2n + approximately n/2) strains was nearly random . Meiotic segregrants of these crosses carrying the unmapped mutation in the -/+ configuration were then crossed with multiply marked haploid strains to further narrow the possible location of the unmapped mutation to a single chromosome . Scoring of markers by complemention tests was simplified by mating spore clones with mixtures of a and alpha strains, each pair carrying the same set of markers . Using this new, more rapid method ("supertriploid mapping"), eight genes required for the maintenance of the killer plasmid were located on the genetic map of S . cerevisiae. Mutat Res, 1979 Jul, 61(2), 191 - 6 Sodium azide-induced mutagenesis in Saccharomyces cerevisiae; Silhankova L et al.; Sodium azide (0.5--2.0 X 10(-5) M), applied for 24 h on cells growing in complete medium, increased up to 26 times the frequency of reversions and locus-specific suppressor mutations of allele ilv1-92 in diploid strain D7 of Saccharomyces cerevisiae . Similarly, it enhanced the frequency of reversions and/or mitotic gene conversions of alleles trp5-12/trp5-27 up to 19 times . Reconstruction experiments showed that the increase of mutations in complete medium was not due to a selection of prototrophic types under growth conditions and, therefore, that sodium azide acts as a weak mutagen in S . cerevisiae under growth conditions at a low pH . No mutagenic or convertogenic effect was observed when azide was applied to resting cells in buffer at pH 4.2. J Bacteriol, 1979 Jun, 138(3), 799 - 804 Modulation of cytochrome biosynthesis in yeast by antimetabolite action of levulinic acid; Malamud DR et al.; Levulinic acid, a competitive inhibitor of delta-aminolevulinic acid dehydratase, was used to inhibit cytochrome biosynthesis in growing yeast cells . In Saccharomyces cerevisiae the antimetabolite acts by inhibiting delta-aminolevulinic acid dehydratase in vivo, causing an accumulation of intracellular delta-aminolevulinic acid and simultaneous decreases in all classes of mitochondrial cytochromes . Changes in cellular cytochrome content with increasing levulinic acid concentration suggested the existence of different regulatory patterns in S . cerevisiae and Candida utilis . In C . utilis, cytochrome a.a3 formation is very resistant to the antimetabolite action of levulinic acid . In this aerobic yeast, cytochrome c+c1 is the most sensitive to levulinic acid, and cytochrome b exhibits intermediate sensitivity. Mol Cell Biochem, 1979 May 6, 25(1), 33 - 42 Mitochondrial glucose-6-phosphate dehydrogenase from Saccharomyces cerevisiae; Campbell WH et al.; In Saccharomyces cerevisiae, a small proportion of the glucose-6-P dehydrogenase activity is firmly associated with the mitochondrial fraction and is not removed by repeated washing or density-gradient centrifugation . However, the enzyme is released by sonic disruption . Mitochondrial glucose-6-P dehydrogenase that is released by sonication and partially purified has been found to be similar to cytosol glucose-6-P dehydrogenase with respect to electrophoretic mobility, isoelectric point, pH optimum, molecular size, and apparent KM's for NADP+ and glucose-6-P . These results indicate that a single species of glucose-6-P dehydrogenase is synthesized in S . cerevisiae and that the enzyme has more than one intracellular location . Mitochondrial glucose-6-P dehydrogenase may be a source of intramitochondrial NADPH and may function with hexokinase and transhydrogenase to provide a pathway for glucose oxidation that is coupled to the synthesis of mitochondrial ATP . A constant proportion of total glucose-6-P dehydrogenase activity remains compartmented in the mitochondrial fraction throughout the growth cycle. Cell, 1979 May, 17(1), 185 - 90 Deletions of a tyrosine tRNA gene in S . cerevisiae; Rothstein R; Genetic fine structure analysis of a tyrosine tRNA in yeast revealed that complete deletions of the gene occurred at an unusually high frequency . Among 56 spontaneous mutations at the SUP4 locus, 16 were classified as deletions as judged by their failure to recombine with any other mutations known to map within the gene . Physical analysis of each deletion confirmed the genetic result . The deletions fall into two size classes: ten are 2100 bp deletions and six are 2800 bp deletions . These results imply that the physical structure of the region surrounding the SUP4 locus, which is known to contain short repeated segments, has a direct role in promoting deletions. J Membr Biol, 1979 Apr 20, 46(2), 91 - 124 Water permeability of yeast cells at sub-zero temperatures; Levin RL et al.; A combined cryomicroscopic-multiple nonlinear regression analysis technique has been used to determine the water permeability of the yeast cell Saccharomyces cerevisiae during freezing . The time rate of change in volume of "supercooled" yeast cells was photographically monitored using a "cryomicroscope" which is capable of controlling in a programmable manner both the temperature and the time rate of change in temperature of the cell suspension being studied . Multiple nonlinear regression analysis together with a thermodynamic model of cell water transport during freezing was then used to statistically deduce the subzero temperature dependence of the cell water permeability . The water permeability process for S . cerevisiae being cooled at subzero temperatures was found to be rate-limited by the passage of water through either the plasmalemma, the cell wall, or a combination of these two permeability barriers . The hydraulic water permeability coefficient for yeast at 20 degrees C is approximately 1--2 x 10(-13) cm3/dyne sec, if extrapolation from subzero temperatures to room temperature is permissible, while the apparent activation energy governing the permeability process at subzero temperatures is approximately 45--68 kJ/mol (11--16 kcal/mol). Cell, 1979 Apr, 16(4), 827 - 39 Identification and mapping of the transcriptional and translational products of the yeast plasmid, 2mu circle; Broach JR et al.; We have identified two major and approximately ten minor poly(A)-containing RNA species in S . cerevisiae which arise from in vivo transcription of the yeast plasmid, known as 2mu circle . The two major species, which are 1325 and 1275 bases in length, are transcribed from the two unique halves of the plasmid and extend into the inverted repeat sequences which separate the unique regions . The map positions of the minor transcripts, which range in length from 350 to 2600 bases, indicate that except for a small region of the genome in which no transcription is observed, both strands of the entire 2mu circle genome are transcribed . We also present evidence demonstrating that RNA transcribed from 2mu circular DNA is used to program the synthesis of specific proteins in yeast: that is, yeast RNA complementary to 2mu circle DNA can be translated in vitro to produce specific polypeptides of substantial size . Finally, the pattern of transcription of 2mu circle suggests the possibility that messenger RNA species are derived by cleavage of larger transcripts, and in addition, that the intramolecular recombination of 2mu circle which occurs in yeast functions as a genetic switch to allow separate expression of two sets of genes on the 2mu circle genome. Cell, 1979 Apr, 16(4), 739 - 51 Evidence for transposition of dispersed repetitive DNA families in yeast; Cameron JR et al.; Dispersed repetitive DNA sequences from yeast (Saccharomyces cerevisiae) nuclear DNA have been isolated as molecular hybrids in lambdagt . Related S . cerevisiae strains show marked alterations in the size of the restriction fragments containing these repetitive DNAs . "Ty1" is one such family of repeated sequences in yeast and consists of a 5.6 kilobase (kb) sequence including a noninverted 0.25 kb sequence of another repetitious family, "delta", on each end . There are about 35 copies of Ty1 and at least 100 copies of delta (not always associated with Ty1) in the haploid genome . A few Ty1 elements are tandem and/or circular, but most are disperse and show (along with delta) some sequence divergence between repeat units . Sequence alterations involving Ty1 elements have been found during the continual propagation of a single yeast clone over the course of a month . One region with a large number of delta sequences (SUP4) also shows a high frequency of sequence alterations when different strains are compared . One of the differences between two such strains involves the presence or absence of a Ty1 element . The novel joint is at one inverted pair of delta sequences. Mol Gen Genet, 1979 Mar 27, 171(3), 239 - 50 Mitochondrial DNA from Podospora anserina . II . Properties of mutant DNA and multimeric circular DNA from senescent cultures; Cummings DJ et al.; Mitochondrial (Mt) DNA from mitochondrial mutants of race s Podospora anserina and from senescent cultures of races s and A was examined . In mutants, we observed that fewer full length circles (31 mu) were present; instead, smaller circles characteristic for each mutant studied were found . Eco R1 digestion of these mutant MtDNAs indicated that in certain mutants, although specific fragments were absent, the total molecular weight of the fragments was not much different than wild-type . The properties of senescent MtDNA was strikingly different from either wild-type or mutant Mt DNA . First, a multimeric set of circular DNA was observed for both race s and A, with a monomeric repeat size of 0.89 mu . These circles ranged in size from 0.89 mu to greater than 20 mu; only one molecule out of some 200 molecules was thought to be of full length (31 mu) . Density gradient analysis showed that there were two density species: a majority were at the same density as wild-type (1.694 g/cm3) and a second at 1.699 g/cm3 . Most of the circular molecules from MtDNA isolated by either total DNA extraction or by extraction of DNA from isolated mitochondria were contained in the heavy DNA fraction . Eco R1 enzymatic digestion indicated that the light DNA had several fragments (amounting to about 23 x 10(6) daltons) missing, compared with young, wild-type MtDNA . Heavy senescent MtDNA was not cleaved by Eco R1 . Analysis with Hae III restriction endonuclease showed also that light senescent MtDNA was missing certain fragments . Heavy MtDNA of average size 20 x 10(6) daltons, yielded only one fragment, 2,500 bp long, by digestion with Hae III restriction endonuclease . Digestion of heavy DNA with Alu I enzyme yielded 10 fragments totalling 2,570 bp . By three criteria, electron-microscopy, Eco R1 and Hae digestion, we conclude that the heavy MtDNA isolated from senescent cultures of Podospora anserina consisted of a monomeric tandemly repeating subunit of about 2,600 bp length . These results on the properties of senescent MtDNA are discussed with regard to the published properties of the rho- mutation in the yeast, S . cerevisiae. J Bacteriol, 1979 Mar, 137(3), 1185 - 90 Synthesis and modification of proteins during the cell cycle of the yeast Saccharomyces cerevisiae; Elliott SG et al.; We have used a novel technique to study the synthesis, modification and degradation of proteins during the cell cycle in Saccharomyces cerevisiae . Logarithmically growing cells were pulse-labeled twice, with the pulses separated in time by more than one generation . Subsequently, the cells were fractionated as to their position in the cell cycle by centrifugal elutriation, and for different proteins the ratio of radioactive material from the two pulses was then determined . Periodic degradation, synthesis, or modification would produce periodic variations in the ratio of counts . Two-dimensional gel electrophoresis was used to examine 110 different proteins at different times of the cell cycle . All but two proteins had a constant ratio of counts through the cell cycle . This indicates that the rate of synthesis of individual proteins increases exponentially during the cell cycle and that periodic degradation or modification of proteins is not a general feature of the cell cycle in S . cerevisiae. Mol Gen Genet, 1979 Feb 26, 170(2), 225 - 30 Peptide chain elongation rate and ribosomal activity in Saccharomyces cerevisiae as a function of the growth rate; Bonven B et al.; The peptide-chain elongation rate of Saccharomyces cerevisiae at two different growth rates was estimated by the kinetics of radioactive labelling of nascent and finished polypeptides as described by Gausing, 1972, and Young and Bremer, 1976 . The elongation rates of a diploid strain cultured in yeast nitrogen base supplemented with glucose or acetate were 9.3 amino acids/s and 5.5 amino acids/s at 30 degrees C, respectively . These data together with published values on the "ribosomal efficency" as a function of growth rate (Waldron and Lacroute, (1975) enable us to estimate the rate of synthesis of ribosomal proteins as a function of the rate of total protein synthesis, alpha r, and the fraction of ribosomes that one active in protein synthesis . We conclude that in S . cerevisiae alpha r is largely independent of the growth rate while the fraction of active ribosomes decreases with decreasing growth rate. Mol Gen Genet, 1979 Feb 16, 170(1), 25 - 48 Physical mapping of the yeast mitochondrial genome: derivation of the fine structure and gene map of strain D273-10B and comparison with a strain (MH41-7B) differing in genome size; Morimoto R et al.; (1) We have derived a fine-structure map of the 70 kb mitochondrial genome of the yeast S . cerevisiae, strain D273-10B, and compared it with our previous maps for strain MH41-7B . Restriction fragment maps for 56 enzyme recognition sites for 13 endonucleases, Eco RI, Hpa I, Bam HI, Hha I, Hinc II, Xba I, Hind III, Bgl II, Pvu II, Sal I, Pst I, Sst I, and Xho I, have been derived . We have used several methods to obtain these maps: (a) Four enzymes (Sal I, Sst I, Xho I, Pst I), each of which cuts D273-10B mtDNA at a single site, were employed to localize and orient fragments from multi-site enzyme digests that are cleaved by the single-site enzyme . (b) Radioactively labeled probes (rRNA or copy RNA {cRNA} transcribed from simple-sequence petite mtDNA) were hybridized to restriction fragments from different digests for identification of fragments which share common sequences . (c) The products of double or triple enzyme digests were identified for mapping and confirmation of the localization of restriction sites . (2) The antibiotic-resistant (antR) loci for erythromycin (E), chloramphenicol (C), paromomycin (P), and oligomycin (OI, OII) were positioned on the physical restriction map by hybridization of 3H-labeled cRNA transcribed from simple-sequence petite mtDNAs that retain a single genetic antR marker to appropriate restriction fragments bound to nitrocellulose filters . (3) Mitochondrial transcripts (21s rRNA, 14s rRNA, and tRNAs) labeled with 125I were hybridized to restriction fragments for identification of the corresponding coding sequence . (4) The gene order and localization of the antR loci and mitochondrial transcripts are as follows: C(0-1.5u)-tRNA I(0-21.5u)-P(29-36.6u)-tRNA II(29-46.4u)-14s rRNA(36-38.3u)-OII(60.3-62.5u) - tRNA III(73-76u) - OI(78.6-83.0u) - tRNA IV(82.5-83.0u) - E(94.2-98.6u) - 21s rRNA (94.2-99.4u) . (5) The DNA fine structure and gene map of the 70 kb D273-10B mtDNA were compared to the map of the larger MH41-7B (76 kb) mtDNA . There are 56 restriction sites on D273-10B and 67 sites on MH41-7B for the 13 enzymes studied . The additional restriction sites are largely accounted for by the presence, in MH41-7B, of two sets of sequences, "A" (2.7 kb) and "B" (3.0 kb), located on either side of the OII marker . The remainder of the fragments map is remarkably similar for the two strains . The distances separating the antR loci and the mitochondrial transcripts are very similar except in the two regions surrounding OII. Mol Gen Genet, 1979 Feb 16, 170(1), 11 - 23 Physical mapping of the Xba I, Hinc II, Bgl II, Xho I, Sst I, and Pvu II restriction endonuclease cleavage fragments of mitochondrial DNA of S . cerevisiae; Morimoto R et al.; A detailed molecular dissection of the yeast mitochondrial genome can be made with restriction endonucleases that generate site-specific cuts in DNA . The ordering of restriction fragments provides the basis of the physical mapping of mitochondrial transcripts and antibiotic resistance (antR) loci, and is a means of analyzing the molecular organization of mtDNA of petite and mit- deletion mutants . We have previously mapped the sites in the mtDNA of yeast strain MH41-7B recognized by the endonucleases Eco RI, Hpa I, Hind III, Bam HI, Sal I, Pst I, and Hha I, providing a total of 41 cleavage sites . We have now mapped the sites recognized by the endonucleases Xba I, Hinc II, Bgl II, Pvu II, Xho I, and Sst I, which make 6, 13, 5, 6, 2, and 2 cuts, respectively . Fragment maps for each of these endonuclease sites were derived by analysis of the products of double-enzyme digests and by hybridization of 3H-cRNA probes transcribed from low-kinetic-complexity petite mtDNAs to restriction fragments generated by various combinations of enzymes. Biochim Biophys Acta, 1979 Jan 11, 545(1), 1 - 14 The yeast mitochondrial ATPase complex . Subunit composition and evidence for a latent protease contaminant; Ryrie IJ et al.; 1 . The subunit compositions of the F1 (oligomycin-insensitive) and F1--F0 (oligomycin-sensitive) mitochondrial ATPase complexes from Saccharomyces cerevisiae have been examined by the highly resolving technique of sodium dodecyl sulphate-polyacrylamide slab gel electrophoresis using a discontinuous buffer system . When isolated in the presence of protease inhibitors, F1 and F1--F0 contained five and twelve bands, respectively; this contrasts with the four- and ten-band patterns seen previously using the less resolving disc gel method . When isolated in the absence of protease inhibitors both F1 and F1--F0 contain spurious polypeptides produced by proteolytic modification . 2 . Endogenous protein turnover in S . cerevisiae was impaired in the presence of protease inhibitors . F1--F0 isolated from cells grown in the presence and absence of inhibitors contained an identical polypeptide composition, suggesting that the subunits are not significantly modified by endogenous proteases prior to cell harvesting . 3 . Yeast F1--F0 prepared in the presence of protease inhibitors contains a latent, sodium dodecyl sulphate-activated protease contaminant . Sodium dodecyl sulphate-induced proteolysis is largely confined to the 52 000 dalton alpha subunit which degrades into polypeptides of 40 000 and 10 700 daltons . The 40 000 dalton band is apparently equivalent to the polypeptide previously designated subunit 3 . 4 . Both F1 and F1--F0 were isolated from Torulopsis glabrata, a yeast with considerably shorter mitochondrial DNA than that in S . cerevisiae . F1--F0 catalysed high rates of ATP--32Pi exchange when reconstituted into phospholipid vesicles, thus demonstrating the presence of a complete coupling mechanism . F1--F0 contained approximately twelve subunits and F1 five, like the S . cerevisiae complexes . It therefore appears that the shorter mitochondrial DNA length does not produce a significantly simpler ATPase subunit structure. Mol Gen Genet, 1979 Jan 10, 168(2), 125 - 39 Evidence that induction and suppression of mutations and recombinations by chemical mutagens in S . cerevisiae during mitosis are jointly correlated; Fahrig R; Mutagen-induced intergenic and interallelic recombination as well as forward mutation were studied in one and the same strain of S . cerevisiae . In nontoxic dose ranges, the induction of mutants and recombinants was parallel after treatment with ethyl methanesulfonate (EMS), methyl methanesulfonate (MMS), N-methyl-N'-nitro-M-nitrosoguanidine (MNNG), triethylene melamine (TEM), 4-nitroquinoline 1-oxide (4-NQO), sodium nitrite (NaNO2), and 1-fluoro-2,4-dinitrobenzene (2,4-DNFB) . Acridine orange (AO) after treatment without light induced recombinants, but reduced the frequency of spontaneous mutations . In combination with TEM, AO exerted the same effect, i.e., reduced its mutagenic effect and enhanced its recombinogenic effect . 4,5,6-Trichloro-2-(2,4-dichlorophenoxy) phenol (Cl5-predioxin) induced mutants and intergenic recombinants, but specifically reduced the spontaneous frequency of interallelic recombinants . In combination with TEM, it enhanced its mutagenic and intergenic recombinogenic effects but reduced its interallelic recombinogenic effect . The main conclusions of the present study, that is 1 . Essentially similar lesions can lead to different genetic consequences, and 2 . Induction of mutation and recombination are jointly correlated, i.e., suppression of mutations leads to an enhancement of recombinations, while suppression of recombinations leads to an enhancement of mutations, are used to set up a speculative concept for mutation and recombination induction in the diploid yeast cell during mitosis. Mol Gen Genet, 1979 Jan 2, 167(3), 287 - 98 Genetic localization of diuron- and mucidin-resistant mutants relative to a group of loci of the mitochondrial DNA controlling coenzyme QH2-cytochrome c reductase in Saccharomyces cerevisiae; Colson AM et al.; Diuron-resistance, DIU (Colson et al., 1977), antimycin-resistance, ANA (Michaelis, 1976; Burger et al., 1976), funiculosin-resistance, FUN (Pratje and Michaelis, 1977; Burger et al., 1977) and mucidin-resistance, MUC (Subik et al., 1977) are each coded by a pair of genetic loci on the mit DNA of S . cerevisiae . In the present paper, these respiratiory-competent, drug-resistant loci are localized relative to respiratory-deficient BOX mutants deficient in coenzyme QH2-cytochrome c reductase (Kotylak and Slonimski, 1976, 1977) using deletion and recombination mapping . Three drug-resistant loci possessing distinct mutated allelic forms are distinguished . DIU1 is allelic or closely linked to ANA2, FUN1 and BOX1; DIU2 is allelic or closely linked to ANA1, MUC1 and BOX4/5; MUC2 is allelic to BOX6 . The high recombinant frequencies observed between the three loci (13% on the average for 33 various combinations analyzed) suggest the existence of either three genes coding for three distinct polypeptides or of a single gene coding for a single polypeptide but subdivided into three easily separable segments . The resistance of the respiratory-chain observed in vitro in the drug-resistant mutants and the allelism relationships between respiratory-competent, drug-resistant loci and coQH2-cyt c reductase deficient, BOX, loci strongly suggest that each of the three drug-resistant loci codes for a structural gene-product which is essential for the normal coQH2-cyt c reductase activity and is obviously a good candidate for a gene product of the drug-resistant loci mapped in this paper . Polypeptide length modifications of cytochrome b were observed in mutants deficient in the coQH2-cyt c red and localized at the BOX1, BOX4 and BOX6 genetic loci (Claisse et al., 1977, 1978) which are precisely the loci allelic to drug resistant mutants as shown in the present work . Taken together these two sets of data provide a strong evidence in favor of the idea that there exist three non contiguous segments of the mitochondrial DNA sequence which code for a single polypeptide sequence of cytochrome b . In each segment mutations which modify the polypeptide sequence can occur leading to the loss (BOX mutants) or to a modification (drug resistant mutants) of the enzyme activity. J Supramol Struct, 1979, 12(4), 425 - 33 Sequence of the amino-terminal region of rat liver ribosomal proteins S4, S6, S8, L6, L7a, L18, L27, L30, L37, L37a, and L39; Wittmann-Liebold B et al.; The sequence of the amino-terminal region of eleven rat liver ribosomal proteins--S4, S6, S8, L6, L7a, L18, L27, L30, L37a, and L39--was determined . The analysis confirmed the homogeneity of the proteins and suggests that they are unique, since no extensive common sequences were found . The N-terminal regions of the rat liver proteins were compared with amino acid sequences in Saccharomyces cerevisiae and in Escherichia coli ribosomal proteins . It seems likely that the proteins L37 from rat liver and Y55 from yeast ribosomes are homologous . It is possible that rat liver L7a or L37a or both are related to S cerevisiae Y44, although the similar sequences are at the amino-terminus of the rat liver proteins and in an internal region of Y44 . A number of similarities in the sequences of rat liver and E coli ribosomal proteins have been found; however, it is