Mutat Res, 1983 Apr, 109(1), 41 - 52 Evaluation of epichlorohydrin (ECH) genotoxicity . Microsomal epoxide hydrolase-dependent deactivation of ECH mutagenicity in Schizosaccharomyces pombe in vitro; Rossi AM et al.; The mutagenic effect of epichlorohydrin (ECH) on the yeast Schizosaccharomyces pombe was studied in vitro in the presence of mouse-liver S9 mix and microsomal and cytosolic fractions . The incubations were always performed in the absence of NADPH-generating systems . S9 mix and microsomes from phenobarbital-pretreated mice significantly reduced ECH mutagenicity, whereas the cytosol did not result in any deactivating effect . The various protein contents of the subcellular fractions were not involved in any scavenger effect as regards ECH mutagenic activity . Moreover, the addition of reduced glutathione to the incubation mixtures indicated that it did not play an important role, either per se or through the enzyme(s) glutathione-S-epoxide transferase(s), in preventing ECH genotoxicity . Our results suggest that microsomal epoxide hydrolase(s) represents the major step in the detoxifying pathway of ECH . These observations were supported by measurements of the specific epoxide hydrolase activity in the various fractions on the same substrate. J Cell Sci, 1983 Mar, 60, 355 - 65 Nucleoside diphosphokinase and cell cycle control in the fission yeast Schizosaccharomyces pombe; Dickinson JR; Centrifugal elutriation was used to prepare synchronous cultures of Schizosaccharomyces pombe . Nucleoside diphosphokinase activity was measured throughout the cell cycle . In the wild-type strain (972) nucleoside diphosphokinase activity doubled in a stepwise fashion . The midpoint of the rise in enzyme activity was at 0.65 of a cycle, 0.29 of a cycle before the next S phase . Synchronous cultures of the mutant wee 1-6 were also prepared . In this strain S phase is delayed, occurring about 0.3 cycle later than in the wild-type . In wee 1-6 the midpoint of the stepwise doubling in nucleoside diphosphokinase activity occurred at 0.084; showing that the rise in enzyme activity is also delayed . Addition of cycloheximide to an exponentially growing culture caused an immediate inhibition of protein synthesis, yet nucleoside diphosphokinase activity continued to increase exponentially for a further 300 min . This indicates that the stepwise doubling of nucleoside diphosphokinase activity during the cell cycle is not achieved by a simple control on protein synthesis . Two temperature-sensitive cdc- mutants were also used: cdc2-33, a mutant whose single genetic lesion results in the twin defects of a loss of mitotic control and a loss of commitment to the cell cycle; and cdc 10-129, which has a defect in DNA replication . In both mutants a temperature shift-up of an asynchronously growing culture from the permissive (25 degrees C) to the restrictive temperature (36.5 degrees C) results in a rapid inhibition of DNA replication . In both mutants nucleoside diphosphokinase continues to increase exponentially . Therefore, although nucleoside diphosphokinase is required for DNA replication, apparently DNA replication is not required for an increase in nucleoside diphosphokinase activity. J Biol Chem, 1983 Jan 10, 258(1), 143 - 9 The primary structure of the alcohol dehydrogenase gene from the fission yeast Schizosaccharomyces pombe; Russell PR et al.; We have cloned and sequenced the alcohol dehydrogenase gene of the fission yeast Schizosaccharomyces pombe . The gene was isolated by transformation and complementation of a Saccharomyces cerevisiae strain which lacked functional alcohol dehydrogenase with an S . pombe gene bank constructed in the autonomously replicating yeast plasmid YEp13 . Southern hybridization analysis indicates that S . pombe contains only one alcohol dehydrogenase gene . The structural region of the gene is 50% homologous to the alcohol dehydrogenase encoding genes of the budding yeast S . cerevisiae . The gene exhibits a very strong codon usage bias; with the set of predominantly used codons generally resembling that which S . cerevisiae employs preferentially . All of the differences in codon usage bias between S . pombe and S . cerevisiae are in the direction of greater G + C content in S . pombe codons . It is argued that this observation supports the hypothesis that selection toward uniform codon-anticodon binding energies contributes to codon usage bias and that the optimum binding energy is, on the average, higher in S . pombe than S . cerevisiae. Z Allg Mikrobiol, 1983, 23(5), 289 - 96 {Purification and isolation of the arom aggregates of Schizosaccharomyces pombe}; Bode R et al.; The five enzymes that catalyzing steps two through six in the prechorismate polyaromatic amino acid biosynthetic pathway are physically associated and have been purified up to 400-fold from Schizosaccharomyces pombe . The native arom aggregate has a molecular weight of approx . 140,000-145,000 based on gel filtration, glycerol-density-gradient centrifugation, and polyacrylamide-gel electrophoresis in the presence of sodium dodecyl sulphate . Similarities between the S . pombe arom aggregate and that of Neurospora crassa and Euglena gracilis are discussed. Z Allg Mikrobiol, 1983, 23(4), 219 - 24 {Gene-enzyme relationships of the arom aggregate of Schizosaccharomyces pombe}; Bode R; The gene-enzyme relationships of the arom multienzyme complex of Schizosaccharomyces pombe that catalyzes steps two through six in the prechorismate polyaromatic amino acid biosynthetic pathway have been studied . The various mutants were subjected to biochemical analysis by direct enzymic assays . These studies have established that aro-3A, aro-3B, aro-3C, aro-3D, and aro-3E mutants lack, respectively, the enzymic activities 5-dehydroquinate synthase, 5-dehydroquinase, shekimate kinase, 3-enolpyruvylshikimate 5-phosphate synthase, and shikimate: NADP oxidoreductase . In S . pombe lack enzymic activities for the inducible quinate catabolic pathway . The functional significance of the arom aggregate is discussed. Mol Gen Genet, 1983, 192(1-2), 212 - 7 Regulation of the maximal rate of RNA synthesis in the fission yeast Schizosaccharomyces pombe; Elliott SG; Of interest to many biologists is how growth, e.g., RNA synthesis, and cell division are mutually controlled . One method of establishing the nature of the control is to determine what "factors" are limiting when cells synthesize RNA at a maximal rate . The transcription maximum (maximum rate of RNA synthesis) has been determined in cell division mutants that continue to grow but fail to divide to determine if there is a cell cycle control over RNA synthesis . There is no correlation between transcription maximum and DNA synthesis or septation which suggests that these events do not exert a direct cell cycle control over RNA synthesis in exponentially growing cells . In addition, the lack of strong correlation between the transcription maximum and cell size or gene dosage indicates that the rate of RNA synthesis is not directly regulated by either of these parameters . The possibility that the maximum rate is determined by a concentration effect of an end product which acts in the nucleus, such as a specific RNA or protein, could not be ruled out and evidence is presented in support of such a model. Mol Gen Genet, 1983, 192(1-2), 204 - 11 Coordination of growth with cell division: regulation of synthesis of RNA during the cell cycle of the fission yeast Schizosaccharomyces pombe; Elliott SG; In the fission yeast Schizosaccharomyces pombe the rate of RNA synthesis, as determined by pulse labeling, increases in a step-like manner in synchronous cultures prepared by centrifugal elutriation . Cultures prepared in this way show marked reductions in perturbations which can be caused by many synchrony techniques . Kinetic evidence indicates that alterations in pool metabolism are not responsible for the step pattern . The long period of increase in the rate doubling (relative to cell number increase) indicates that the period of increasing rate may be due to a growth period and not a sudden transition between a slow and a fast rate . An analysis of synchronous cultures of cells of different cell size and synchronous cultures of temperature sensitive mutants blocked in cell cycle progress indicated that neither size control, changes in DNA content nor septation are directly responsible for the steps in RNA synthesis . Instead the time of the rate change is associated with a specific point in the cell cycle, probably an event associated with nuclear division. Mol Gen Genet, 1983, 191(3), 519 - 24 Yeast ribosomal proteins: VII . Cytoplasmic ribosomal proteins from Schizosaccharomyces pombe; Otaka E et al.; The cytoplasmic ribosomal proteins from a fission yeast Schizosaccharomyces pombe were analysed by two-dimensional polyacrylamide gel electrophoresis . Seventy-three protein species were identified in the 80S ribosome, and named SP-S1 to SP-S33 and SP-L1 to SP-L40 in the small and large subunits, respectively . Many of these proteins could be correlated to those of Saccharomyces cerevisiae on the basis of their electrophoretic mobilities . Eleven proteins were isolated from the 80S ribosome, and their amino acid compositions were determined . Of these, SP-S6, SP-L1, SP-L12, SP-L15, SP-L17, SP-L27, SP-L36 and SP-L40c and d were sequenced from their amino-termini . SP-S28 and SP-L2 appear to have their amino-termini blocked . These results were compared with the data available for the S . cerevisiae and rat liver ribosomal proteins . The S . cerevisiae counterparts of the eight proteins mentioned above were found to be YS4, YL1, YL10, YL14, YL35, YL40 and YL44c and d, respectively . The rat liver counterparts of SP-S6, SP-L1, SP-L27 and SP-L40c and d were the rat S6, L4, L37 and P2, respectively . Comparison of the partial sequences of these ribosomal proteins suggests that these two yeasts are relatively far apart, phylogenetically. Mol Gen Genet, 1983, 191(1), 91 - 8 Expression of cloned mitochondrial DNA from the petite negative yeast Schizosaccharomyces pombe in E . coli minicells; Del Giudice L et al.; The minicell producing Escherichia coli strain D24 (lysogenic for phage lambda cI857) was transformed with the recombinant plasmid pDG3 containing the entire mitochondrial (mt) genome of the fission yeast Schizosaccharomyces pombe (S . pombe) cloned in the single BamHI-site of the E . coli plasmid pBR322 (Del Giudice 1981) . By DNA-RNA hybridization it could be shown that the total mtDNA sequence of the plasmid pDG3 was transcribed in the E . coli minicells . The cloned mtDNA also directed the synthesis of at least five novel polypeptides with molecular weights between 7,200 and 34,000 . When the minicell producing E . coli strain P678-54 was transformed with the hybrid plasmid pDG3, considerable portions of the inserted mtDNA sequences were deleted . One of the resulting plasmids (pDG4), lacking about two-thirds of the mtDNA sequence, directed the synthesis of new polypeptides in the range of 7,000 to 17,500 daltons . Another derivative of pDG3, the plasmid pDG5, containing one-sixth of the mtDNA sequence, directed the synthesis of at least three novel polypeptides . The mt origin of novel polypeptides coded by the hybrid plasmid pDG3 was demonstrated by use of antisera raised against total mitochondrial proteins from S . pombe and antisera against subunits II and III of cytochrome c oxidase from Saccharomyces cerevisiae (S . cer.). Teratog Carcinog Mutagen, 1983, 3(1), 75 - 87 In vivo and in vitro mutagenicity studies of a possible carcinogen, trichloroethylene, and its two stabilizers, epichlorohydrin and 1,2-epoxybutane; Rossi AM et al.; In vivo and in vitro methodologies that have employed the yeast Schizosaccharomyces pombe as genetic indicator have been utilized to investigate the mutagenicity of two trichloroethylene (TCE) samples of pure and technical grade . Mutagenicity assays were also performed on two stabilizers contained in the technical grade sample: epichlorohydrin and 1,2-epoxybutane . In the in vitro studies a metabolic conversion system was supplied by liver homogenate (S-9) from mice and rats untreated and pretreated with phenobarbital and/or beta-naphthoflavone . Up to highly toxic doses of TCE were applied to growing and stationary-phase yeast cells . In the in vivo studies two different host-mediated assays, intrasanguineous and intraperitoneal methodologies, were performed on different mice breeds treated by oral administration . Epichlorohydrin and epoxybutane were tested singly or combined in a mixture of the same ratio as in the technical grade TCE sample . Both TCE samples gave negative results for in vivo and in vitro assays, whereas the two contaminants were found mutagenic only in vitro . The high toxicity of the technical TCE sample did not allow us to reach concentrations containing effective levels of its two additives. Nature, 1982 Dec 23, 300(5894), 706 - 9 Functionally homologous cell cycle control genes in budding and fission yeast; Beach D et al.; The cdc 2 (previously called wee 2) cell cycle start gene of Schizosaccharomyces pombe, which is required for start and the control of mitosis, has been isolated from an S . pombe gene bank by complementation of a cdc 2 mutation . A functionally homologous sequence which complements the cdc 2 mutation has also been isolated from a Saccharomyces cerevisiae gene bank and this sequence has been shown to contain the cdc 28 cell cycle start gene of S . cerevisiae . It is concluded that the cdc 2 and cdc 28 genes perform homologous cell cycle control functions in the two organisms. J Cell Sci, 1982 Dec, 58, 263 - 85 Patterns of protein synthesis during the cell cycle of the fission yeast Schizosaccharomyces pombe; Creanor J et al.; The rate of protein synthesis through the cell cycle of Schizosaccharomyces pombe has been determined from the incorporation of pulses of {3H}tryptophan in synchronous cultures prepared by selection in an elutriating rotor . This selection procedure caused minimal perturbations as judged by asynchronous control cultures, which had also been put through the rotor . The rate of synthesis showed a periodic pattern rather than a smooth exponential increase . There was a sharp increase in the rate at an 'acceleration point' at about 0.9 of the cycle . Model-fitting by a novel procedure suggests that the average single cell has an increasing rate of protein synthesis for the first 60% of the cycle and a constant rate for the remaining 40% . The same pattern was shown in less extensive experiments with {3H}leucine and {3H}phenylalanine . It was also shown in a series of size mutants, which indicates that the pattern is not size-related, in contrast to earlier work on the rates of synthesis of messenger RNA . However, one large mutant (cdc 2.M35r20) had a significantly earlier acceleration point . Care was taken to justify the assumption that the rate of incorporation of tryptophan was a valid measure of the rate of protein synthesis . A tryptophan auxotroph was used to eliminate the problem of endogenous supply and the size of the metabolic pool was measured through the cycle . This pool did not show cell-cycle related fluctuations . An operational model of the pools is presented. Mutat Res, 1982 Dec, 102(4), 425 - 37 Mutagenic action of structurally related alkene oxides on Schizosaccharomyces pombe: the influence, 'in vitro', of mouse-liver metabolizing system; Migliore L et al.; A series of aliphatic epoxides were tested for their ability to induce forward mutations in the yeast Schizosaccharomyces pombe . For all the compounds under study, a linear dose-response relationship was found, and the ranking of the relative specific activity was: epichlorohydrin greater than ethylene oxide greater than glycidol greater than 1,2-epoxybutane greater than 1,1,1-trichloropropylene oxide greater than propylene oxide greater than 2,3-epoxybutane . The influence of the metabolic conversion of the epoxides by the mouse-liver S9 fraction was also investigated . In such conditions, except for the 2,3-epoxybutane, the genetic activity of epoxides seems to be reduced. Proc Natl Acad Sci U S A, 1982 Dec, 79(24), 7819 - 23 Cloned ural locus of Schizosaccharomyces pombe propagates autonomously in this yeast assuming a polymeric form; Sakaguchi J et al.; DNA segments cloned from Schizosaccharomyces pombe by the ability to complement Escherichia coli pyrB mutations are shown to complement a ural mutation in S . pombe, thereby demonstrating that ural is the structural gene for aspartate transcarbamylase of S . pombe . Further, such segments combined with parts or all of pBR322 are shown to be capable of autonomous propagation in S . pombe . This suggests the existence of an autonomously replicating sequence (ars) in the vicinity of ural . Unlike the TRP1 segment cloned from Saccharomyces cerevisiae {Struhl, K., Stinchcomb, D . T., Scherer, S . & Davis, R . W . (1979) Proc . Natl . Acad . Sci . USA 76, 1035-1039}, plasmids carrying the ural locus do not multiply as monomers but assume a polymeric form as large as a decamer to an icosamer in the yeast . Monomers are tandemly arranged in the polymer . Inversion of an inserted fragment or insertion of another segment into a competent plasmid greatly decreases the efficiency of such transformation, implying a role of the tertiary structure of the plasmids in the establishment of transformation of this kind. J Biol Chem, 1982 Nov 10, 257(21), 12509 - 16 Exchange of oxygen between phosphate and water catalyzed by the plasma membrane ATPase from the yeast Schizosaccharomyces pombe; Amory A et al.; The ATPase of the plasma membrane isolated from the yeast Schizosaccharomyces pombe catalyses a medium Pi in equilibrium H2O exchange in the presence of Mg2+ and in the absence of ATP and ADP . (formula, see text) The Pi in the E.Pi species tumbles in the active site so that each of its oxygens has an equal probability of exchange with water . The partition coefficient (Pc = k2/k2 + k-1) is 0.45 . The total rate of oxygen exchange, Vex, representing the rate of incorporation of water oxygens occurring during hydrolysis of E--P into E.Pi (Vex = k-2{E--P}) is dependent on the {Pi} with an apparent Km of 177 mM, reflecting the very low affinity of the enzyme for Pi . The maximal exchange rate is 6.7 micrograms atoms of oxygen X min-1 X mg-1 of protein . The individual kinetic constants are evaluated: k2 = 3.4 X 10(3) min-1, k-2 = 5.50 X 10(5) min-1 and k-1 = 4.11 X 10(3) min-1 . Under conditions of uncoupled transport, the hydrolysis of E--P is exergonic as {E.Pi}/{E--P} = k-2/k2 = 164 . During hydrolysis of ATP, the rate of medium Pi in equilibrium H2O exchange activity as well as the extent of phosphorylation of the enzyme from Pi are markedly stimulated: 7.9 and 5.3 times, respectively, whereas the Pc is not modified . These data are most simply interpretated by the existence of two isomeric forms of the enzyme; one is specific for binding ATP and the other for binding Pi . The Pc for intermediate Pi in equilibrium H2O exchange, when the E--P species is formed from cleavage of {gamma-18O}ATP, is the same as for medium exchange, indicating that the same exchange pathway operates under both conditions . Varying the {ATP} had very little effect on the Pc, indicating little or no cooperativity between different catalytic sites under the conditions used in this study. Proc Natl Acad Sci U S A, 1982 Nov, 79(21), 6475 - 9 Post-transcriptional nucleotide addition is responsible for the formation of the 5' terminus of histidine tRNA; Cooley L et al.; All sequenced histidine tRNAs have one additional nucleotide at the 5' end when compared to other tRNA species . Sequence analysis of histidine tRNA genes from Drosophila melanogaster and Schizosaccharomyces pombe showed that the terminal guanylate residue of the mature tRNAs is not encoded by the genes . Analysis of the products from in vitro transcription of these genes in extracts from Drosophila Kc cells demonstrated that the 5'-terminal nucleotide present in the mature tRNA is added post-transcriptionally . The addition reaction requires ATP . A portion of the mature tRNAs are then modified at the 5'-terminal pG . Analysis of the RNA species formed during the in vitro maturation of the Drosophila histidine tRNA primary transcript uncovered the following maturation scheme: (i) the primary transcript is processed by RNase P at the 5' end to form an intermediate precursor; (ii) the 3'-flanking sequence is endonucleolytically removed, and a guanylate moiety is added to the 5' end to form mature-sized histidine tRNA; and (iii) a fraction of the 5'-terminal guanylate residues then undergoes modification . In contrast to the capping of eukaryotic mRNA, the guanylate addition to histidine tRNA results in the formation of a (3'-5')-phosphodiester bond . There are no precedents for the post-transcriptional addition of nucleotides (in phosphodiester linkage) to the 5' end of RNA precursors. Cytometry, 1982 Sep, 3(2), 123 - 8 Cell cycle operation during batch growth of fission yeast populations; Agar DW et al.; Batch cultivation provides a continuous sequence of different environments useful for studying responses of cell cycle controls . Flow cytometry measurements have been made of the frequency functions for protein, RNA, and DNA at different times during batch growth of the fission yeast Schizosaccharomyces pombe . The mean cellular protein and RNA contents and their variances tend to increase with increasing population specific growth rates . Analysis of the mid-exponential phase DNA frequency function data indicates that DNA synthesis occupies 12% of the total cell cycle time and is completed at the same time as cell separation . Coordination of DNA synthesis and cell separation is less precise when population growth rate is low in late lag and early stationary phases. J Cell Sci, 1982 Aug, 56, 263 - 79 Ascospore development in the fission yeasts Schizosaccharomyces pombe and S . japonicus; Tanaka K et al.; The fine structure of ascospore formation in the fission yeasts Schizosaccharomyces pombe and Schizosaccharomyces japonicus var . japonicus was studied by serial thin-sectioning and electron microscopy . The morphogenetic events were almost the same in both species . Ascospore development was initiated by the formation of the forespore membrane on the cytoplasmic side of the differentiated nucleus-associated organelle (NAO) in the interval between meiosis I and II in S . pombe, or during the post-meiotic nuclear division in S . japonicus, and the process proceeded almost synchronously through the two or four nuclei in the ascus . The forespore membrane developed by fusion of the cytoplasmic vesicles and this was clearly demonstrated in S . japonicus where the behaviour of vesicles involved in the forespore membrane development could be traced as they were marked by the presence of electron-dense granules . The staining technique, by phosphotungustic acid--chromic acid (PTA-CA) after treatment with periodic acid, was used to attempt to elucidate the origin and the nature of the forespore membrane . The method specific to plasmalemma-type membranes stained both ascus and ascospore plasmalemmas; the forespore membrane was not stained at first but developed the same affinity for stain as the plasma membrane in the course of ascospore development . The results suggest that the forespore membrane did not come directly from the ascus plasma membrane, but from another membrane system such as the endoplasmic reticulum . Spore wall material was deposited in the space between the inner and outer leaflets of the forespore membrane. Eur J Biochem, 1982 Jul, 125(3), 471 - 7 Alterations of the alpha or beta subunits of the mitochondrial ATPase in yeast mutants; Boutry M et al.; Among 979 non-glycerol growers of the yeast Schizosaccharomyces pombe, 40 strains were found to be deficient in the mitochondrial ATPase activity . Three of them exhibited an alteration in either the alpha or beta subunits of the F1ATPase . The alpha subunit was not immunodetected in the A23/13 mutant . The beta subunit was not immuno-detected in the B59/1 mutant . The existence of these two mutants shows that the alpha and beta subunits can be present independently of each other in the inner mitochondrial membrane . The beta subunit of the mutant F25/28 had a slower electrophoretic mobility than that of the wild-type beta subunit . This phenotype indicates abnormal processing or specific modification of the beta subunit . All mutants showed reduced activities of the NADH-cytochrome c reductase and of the cytochrome oxidase and a decreased synthesis of cytochrome aa3 and cytochrome b . This pleiotropic phenotype appears to result from specific modifications in the mitochondrial protein synthesis . The mitochondrial synthesis of four polypeptides (three cytochrome oxidase and one cytochrome b subunits) was markedly decreased or absent while three new polypeptides (Mr = 54000, 20000 and 15000) were detected in all the mutants analysed . This observation suggests that a functional F1ATPase is necessary for the correct synthesis and/or assembly of the mitochondrially made components of the cytochrome oxidase and cytochrome b complexes. Can J Biochem, 1982 Jun, 60(6), 693 - 704 Sexual development in a homothallic fission yeast: synthesis of readiness proteins resolved by gel electrophoresis; Calleja GB et al.; Sexual development of a homothallic strain of Schizosaccharomyces pombe was monitored by radiolabelling and sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis . Of more than 60 bands detected by Coomassie brilliant blue and by autoradiography, about 30 bands synthesized during development were discrete enough for experimental analysis . About a dozen bands are preferentially vegetative, another dozen preferentially developmental . However, vegetative bands as a group are also synthesized during development . Their synthesis is relatively unaffected by low concentrations of cycloheximide or by chloramphenicol and is not temperature sensitive at 37 degrees C nor catabolite repressible . Only band 40 (ca . 40 000 daltons) seems to be exclusively vegetative . The synthesis of developmental bands 13, 18, 24, 30, and alpha, all of which first appear during late-log phase, is catabolite repressible . Developmental band 51 is also synthesized throughout the vegetative phase . The synthesis of bands 24, 30, 51, and alpha is temperature sensitive at 37 degrees C during the development, but that of band 18 is not . The synthesis of band 13 during development is not temperature sensitive, but its earlier synthesis during late-log phase is . The synthesis of all these six developmental bands is immediately inhibited by cycloheximide, but not by chloramphenicol . Their appearance as a group of radioactive bands is greatly diminished in cultures grown in cycloheximide, in chloramphenicol, or in ethidium bromide . Developmental bands 13, 18, 24, and 30 may be called readiness proteins . They first appear prior to the earliest morphological signs of sexual activity . Their developmental synthesis is inhibited by conditions that inhibit sexual development . Such inhibitory conditions include anaerobiosis, restrictive temperature, aging in stationary phase, the presence of inhibitors of cytoplasmic protein synthesis and of mitochondrial function, and catabolite repression . Readiness proteins may be regulating the switch from vegetative metabolism. Nucleic Acids Res, 1982 May 11, 10(9), 2851 - 64 The 5.8S RNA gene sequence and the ribosomal repeat of Schizosaccharomyces pombe; Schaak J et al.; We have characterized the rRNA gene repeat in Schizosaccharomyces pombe . This repeat, which does not contain the 5S RNA gene, is found in a 10.4 kb HindIII DNA fragment . We have determined the nucleotide sequences of the S . pombe 5.8S RNA gene and intergenic spacers from two different 10.4 kb DNA fragments . Analysis of isolated total cellular 5.8S RNA revealed the presence of eight species of 5.8S RNA, differing in the number of nucleotides at the 5'-end . The eight 4.8S RNA species vary in length from 158 to 165 nucleotides . Apart from the heterogeneity observed at the 5'-end, the sequence of the eight 5.8S RNA species appears to be identical and is the same sequence as coded for by the 5.8S genes . The gene sequence shows great homology to the 5.8S RNA genes or S . cerevisiae and N . crassa . Most of the base differences are confined to the highly variable stem though to be involved in co-axial helix stacking with the 25S RNA, where base pairing is nearly identical despite the sequence differences . Secondary structure models are examined in light of 5.8S RNA oligonucleotide conservation across species from yeasts to higher eukaryotes. Proc Natl Acad Sci U S A, 1982 Apr, 79(8), 2618 - 22 Extrachromosomal mutator inducing point mutations and deletions in mitochondrial genome of fission yeast; Seitz-Mayr G et al.; We report the isolation and characterization of a mutator mutant in the fission yeast Schizosaccharomyces pombe . This mutator is of extrachromosomal, very likely mitochondrial, inheritance and acts exclusively on mitochondrial mtDNA . It greatly enhances the frequency of spontaneous mitochondrial drug-resistance mutants compared to the wild type, but it is not obligatory for their occurrence . In contrast, mitochondrial respiratory deficient mutants can only be isolated from mutator strains . It could be shown that this mutator induces point mutations as well as deletions in the mitochondrial genome which lead to respiratory deficiency . This mutator might prove to have a novel function encoded by the mtDNA. J Biol Chem, 1982 Feb 25, 257(4), 1824 - 8 Potassium transport coupled to ATP hydrolysis in reconstituted proteoliposomes of yeast plasma membrane ATPase; Villalobo A; Potassium transport coupled to ATP hydrolysis has been reconstituted in proteoliposomes using a highly purified plasma membrane Mg2+-dependent ATPase of the yeast Schizosaccharomyces pombe . The ATPase activity in the incorporated enzyme was strongly stimulated (2.2-fold) by the H+-conducting agent carbonyl cyanide m-chlorophenylhydrazone (CCCP) . The H+/K+ exchanger nigericin (in the presence of K+) stimulated 1.6-fold the ATPase activity . When both ionophores were added together, the stimulation was increased up to 2.7-fold . When a potassium concentration gradient (high K+ in) was applied to the proteoliposome membrane, a significant drop in the CCCP-stimulated ATPase activity was observed . Inversion of the K+ concentration gradient (high K+ out) did not decrease the stimulation by CCCP . High Na+ in also decreased the stimulation induced by CCCP in the absence but not in the presence of external K+ . However, high Li+ in had no effect . Direct potassium efflux from the proteolyposomes was detected upon addition of MgATP using a selective K+ electrode . The ATP-dependent potassium efflux was abolished in CCCP and/or nigericin-pretreated proteoliposomes . However, during steady state ATP hydrolysis, a transient and small K+ efflux was observed upon addition of a CCCP pulse . I propose that the plasma membrane Mg2+-dependent ATPase in yeast cells not only carries out electrogenic H+ ejection but also drives the uptake of potassium via a voltage-sensitive gate which is closed in the absence and open in the presence of the membrane potential. Mutat Res, 1982 Feb 22, 92(1-2), 39 - 47 Mutations induced by X-rays and UV radiation during the nuclear cell cycle in the yeast Schizosaccharomyces pombe; Barale R et al.; The availability of a cell-division-cycle (cdc) mutant in the fission yeast S . pombe, wee 1-50, has made possible the production of a large population of G1 nuclear-stage synchronized cells . During their development, yeast cells from the G1 into the G2 nuclear stages were treated with X-rays and UV radiation at various doses . The DNA pre-replicative and replicative phases were the most sensitive to both cell lethality and mutant induction with either X-rays or UV radiation . The trends of induced biological effects that were observed suggest that the induction of mutations is dependent on the number of unrepaired DNA lesions that reach the replicating fork or of those that occur at that time . The X-ray-induced mutations were earlier saturated, possibly because of the higher number of lethal lesions so induced. Mol Cell Biol, 1982 Feb, 2(2), 106 - 16 Structure of the Schizosaccharomyces pombe cytochrome c gene; Russell PR et al.; The cytochrome c gene of the fission yeast Schizosaccharomyces pombe has been cloned by using the Saccharomyces cerevisiae iso-1-cytochrome c gene as a molecular hybridization probe . The DNA sequence and the 5' termini of the mRNA transcripts of the gene have been determined . The DNA sequence has confirmed, with two exceptions, the previously determined protein sequence . The nonrandom distribution of silent third base differences which was observed between the two cytochrome c genes of S . cerevisiae does not extend to the S . pombe cytochrome c gene, suggesting that there are no constraints other than protein function and codon usage which have acted to conserve the cytochrome DNA sequences of the two yeasts . Introduction of the S . pombe cytochrome c gene on a yeast plasmid into a S . cerevisiae mutant which lacked functional cytochrome c transformed that recipient strain for the ability to grow on a nonfermentable carbon source . This implies that the S . pombe cytochrome c gene has all the regulatory signals which are required for its expression in S . cerevisiae, and that none of the amino acid differences between the cytochrome c proteins of the two yeasts has a drastic effect on the function of the protein in vivo. Nucleic Acids Res, 1982 Jan 22, 10(2), 487 - 500 The 5S RNA genes of Schizosaccharomyces pombe; Mao J et al.; The genomic arrangement and sequences of S . pombe 5S RNA genes are reported here . The 5S gene sequences appear to be dispersed within the genome, and are found independently of other rRNA genes . The sequences of two 5S genes examined show identical coding regions of 119 base pairs but have widely varying flanking sequences . A tRNAAsp gene is found in the 3' flanking region of one of the 5S genes . The tRNAAsp gene is faithfully transcribed in an X . laevis in vitro system, while the 5S genes are not transcribed in this system . The phylogenetic position of S . pombe is examined through comparison of 5S RNA sequences. J Gen Microbiol, 1982 Jan, 128 (Pt 1), 61 - 71 Cell cycle specificity of certain antimicrotubular drugs in Schizosaccharomyces pombe; Walker GM; Of the seven antimicrotubular drugs tested, nocodazole, mebendazole and trifluralin at saturable concentrations failed to inhibit cell division in Schizosaccharomyces pombe, while carbendazim, thiabendazole and chloropropham each at 50 micrograms ml- and amiprophos methyl at 200 micrograms ml-1 completely arrested cell division . This inhibition was associated with striking morphological changes in which carbendazim- and thiabendazole-treated cells became elongated and pseudohyphal, whereas chloropropham- and amiprophos methyl-treated cells appeared small and rounded with occasional V-shaped pairs . Lomofungin staining revealed that nuclear division was also arrested by these drugs . Suspected blockage of defined cell cycle stages was confirmed by pulse-induction experiments which revealed that cells could be synchronized into division using exposure to a drug for one generation . Further experiments with synchronous cultures prepared by size selection showed that different drugs possessed different transition points; for example, carbendazim and thiabendazole were effective in blocking a late stage of the cell cycle just prior to division, whereas amiprophos methyl affected a very early stage . The results suggest that some of the drugs used exert cell cycle specificity in S . pombe either by impairing microtubule assembly mechanisms (as with carbendazim and thiabendazole) or by inhibiting synthesis of tubulin subunits (as with amiprophos methyl) . These drugs could prove useful in studies of microtubule biogenesis during the cell cycle in yeast. Mol Gen Genet, 1982, 187(1), 96 - 100 Extrachromosomal inheritance of nalidixic acid resistance in the petite negative yeast Schizosaccharomyces pombe; Massardo DR et al.; Spontaneous mutants resistant to nalidixic acid (NAL) were isolated from the petite negative yeast Schizosaccharomyces pombe (S . pombe) . One of these mutants, resistant to 200 micrograms/ml NAL, nalr-Y13, was characterized both genetically and biochemically . The extrachromosomal inheritance of this mutation was demonstrated both by mitotic segregation and by mitotic haploidization analysis . In the wild-type, NAL at a concentration of 100 micrograms/ml almost completely inhibits incorporation of {14C}adenine in total DNA as well as in mitochondrial DNA . In the NAL-resistant mutant both total DNA synthesis and mitochondrial DNA synthesis were resistant to the drug . These results are discussed in view of previously published findings on the close interaction between the two DNA synthesizing systems in S . pombe. Mol Gen Genet, 1982, 185(2), 311 - 4 Multiple drug resistance in the fission yeast Schizosaccharomyces pombe: evidence for the existence of pleiotropic mutations affecting dependent transport systems; Johnston PA et al.; The uptake of L-tyrosine into wild type and antibiotic resistant strains of Schizosaccharomyces pombe requires an energy source, is initially linear with respect to time, is inhibited by 2,4-dinitrophenol and sodium azide and is saturable . However the initial uptake rates and the amount of L-tyrosine accummulated by antibiotic resistant strains are much less than wild type . Comparison of the kinetic constants of uptake shows that mutant strains have a reduced maximum velocity of uptake compared to wild type and a larger Km . Since the three mutant strains possess a permeability barrier to L-tyrosine as well as being drug resistant this is an indication that antibiotic resistance may be caused by a decrease in plasma membrane permeability. Mol Gen Genet, 1982, 188(2), 219 - 24 Nonsense suppression in Schizosaccharomyces pombe: the S . pombe Sup3-e tRNASerUGA gene is active in S . cerevisiae; Hottinger H et al.; The gene encoding the efficient UGA suppressor sup3-e of Schizosaccharomyces pombe was isolated by in vivo transformation of Saccharomyces cerevisiae UGA mutants with S . pombe sup3-e DNA . DNA from a clone bank of EcoRI fragments from a S . pombe sup3-e strain in the hybrid yeast vector YRp17 was used to transform the S . cerevisiae multiple auxotroph his4-260 leu2-2 trp1-1 to prototrophy . Transformants were isolated at a low frequency; they lost the ability to grow in minimal medium after passaging in non-selective media . This suggested the presence of the suppressor gene on the non-integrative plasmid . Plasmid DNA, isolated from the transformed S . cerevisiae cells and subsequently amplified in E . coli, transformed S . cerevisiae his4-260 leu2-2 trp1-1 to prototrophy . In this way a 2.4 kb S . pombe DNA fragment carrying the sup3-e gene was isolated . Sequence analysis revealed the presence of two tRNA coding regions separated by a spacer of only seven nucleotides . The sup3-e tRNASerUGA tRNA gene is followed by a sequence coding for the initiator tRNAMet . The transformation results demonstrate that the cloned S . pombe UGA suppressor is active in S . cerevisiae UGA mutant strains. EMBO J, 1982, 1(3), 375 - 7 Expression of the cloned uracil permease gene of Saccharomyces cerevisiae in a heterologous membrane; Chevallier MR et al.; A piece of DNA of the yeast Saccharomyces cerevisiae complementing the uracil permease gene was introduced into a plasmid able to replicate autonomously in Schizosaccharomyces pombe . A strain of S . pombe lacking uracil transport activity was transformed with this new plasmid carrying the gene of S . cerevisiae . The behaviour of the transformant shows not only an expression of the uracil permease gene in the heterologous membrane but also that the transport of uracil is active and coupled to the energy furnishing system of the heterologous host. Can J Genet Cytol, 1982, 24(6), 771 - 5 Differential survival as an indicator of potential mutagenicity using repair deficient strains of Saccharomyces cerevisiae and Schizosaccharomyces pombe; Nestmann ER et al.; A method is presented to screen chemicals for potential mutagenicity on the basis of their ability to cause more killing in cells of repair-deficient yeast than in wild type cells . Two species were chosen in the event that one might be more sensitive to certain chemicals . The strains used were RAD+ and rad6 derivatives of Saccharomyces cerevisiae and RAD+ and rad3 derivatives of Schizosaccharomyces pombe . This report describes the test system and results for 12 known, direct-acting mutagens (i.e., not requiring mammalian metabolic activation) . These compounds showed more lethality in one or both of the repair-deficient strains, indicating that they induce damage to DNA which is subject to repair in wild type cells . Advantages of this system include the use of eukaryotic yeast cells which can be manipulated as easily as bacteria, and that exogenous enzymes (S9) can be added for metabolic activation . Growing yeast cells can activate certain promutagens, and preliminary experiments showed positive responses for diethylnitrosamine and 2-acetylaminofluorene without the addition of S9. Mol Gen Genet, 1982, 187(2), 326 - 9 Construction of a Schizosaccharomyces pombe gene bank in a yeast bacterial shuttle vector and its use to isolate genes by complementation; Beach D et al.; A gene bank of partial Sau3A restriction fragments of S . pombe DNA has been constructed in the plasmid vector, pDB248', which is capable of high frequency transformation of S . pombe . Procedures are described which enable plasmids to be recovered from S . pombe by their reintroduction into E . coli . These methods have been used to detect the S . pombe genes lys 1+, ade 6+ and his 2+ in the gene bank by complementation of mutant gene functions, and to physically isolate the lys 1+ gene. Comp Biochem Physiol B, 1982, 71(3), 495 - 500 The mitochondrial adenosine triphosphatase of Acanthamoeba castellanii . Partial characterization and changes in activity during exponential growth; Edwards SW et al.; 1 . The mitochondrial adenosine triphosphatase (ATPase) of Acanthamoeba castellanii is Mg2+-requiring (optimum cation: ATP ratio of 1.5) and has two pH optima of activity (at pH 6.6 and 8.1) . 2 . ATPase activity of submitochondrial particles is effectively inhibited by twelve different inhibitors of energy conservation suggesting similarities in inhibitor-binding sites to other previously characterized complexes . 3 . Gel filtration by passage through Sephadex G-50 increases ATPase activity of submitochondrial particles between 1.5 and 3.5 fold indicating the presence of a low molecular weight inhibitor protein . 4 . After removal of the inhibitor protein, sensitivity to inhibitors of energy conservation decreases by between 1.5 and 14 fold . Crude F1-inhibitor preparations from A . castellanii, Schizosaccharomyces pombe, Tetrahymena pyriformis and bovine heart also inhibit ATPase activity . 5 . Large variations in ATPase activity, F1-inhibitor protein activity, and amounts of immunologically-determined ATPase protein were observed during exponential growth, and the correlation between changes in these measurements is discussed . 6 . The results are also discussed highlighting the similarities between the mitochondrial ATPase of A . castellanii and other mitochondrial ATPases. Nucleic Acids Res, 1981 Dec 11, 9(23), 6429 - 37 Nucleotide sequences of the 5S ribosomal RNA genes and their adjacent regions in Schizosaccharomyces pombe; Tabata S; The organization of 5S ribosomal RNA (rRNA) genes in the genome of Schizosaccharomyces pombe has been investigated by restriction and hybridization analyses . The 5S rRNA genes were not linked to the other three species of rRNA genes which formed a repeating unit of 6.9 megadaltons, but located in other regions surrounded by heterogeneous sequences . The 5S rRNA gene organization in S . pombe is therefore different from those in other yeasts; Saccharomyces cerevisiae and Torulopsis utilis . Four restriction segments of different sizes each containing a single 5S rRNA gene were cloned on a bacterial plasmid, and the sequences in and around the RNA coding regions were determined . In the RNA coding regions, the sequences in four clones were identical with an exception that one residue has been substituted in one clone . In the flanking regions, the sequences were extremely rich in the AT-content and highly heterogeneous . The sequences were also markedly different from those in the corresponding regions of the other two yeasts . THe presence of T-clusters in the regions immediately after the RNA coding sequences was only notable homology among the four clones and the other two yeasts. J Biol Chem, 1981 Dec 10, 256(23), 12081 - 7 Electrogenic proton translocation coupled to ATP hydrolysis by the plasma membrane Mg2+-dependent ATPase of yeast in reconstituted proteoliposomes; Villalobo A et al.; The purified plasma membrane Mg2+-dependent ATPase of the yeast Schizosaccharomyces pombe was incorporated in liposomes using a cholate-dialysis method . The ATPase activity of the incorporated enzyme was stimulated by the H+-conducting agent carbonyl cyanide m-chlorophenylhydrazone and to a much lower extent of the K+-ionophore valinomycin in the presence of potassium . The K+/H+ exchanger nigericin (plus K+) did not stimulate ATPase activity, whereas the combined addition of both nigericin plus valinomycin was strongly stimulatory . The incorporated ATPase activity was controlled by the generated electrochemical H+ gradient since only conditions which collapse both the membrane potential and the pH gradient stimulated fully the ATPase activity of the incorporated enzyme . Direct measurement of proton movement with a pH glass electrode showed a fast and transient proton entry into the proteoliposomes upon addition of MgATP in the presence of the charge-compensating cation K+ (plus valinomycin) . Moreover, during the steady state ATP hydrolysis, a H+ entry was again observed when the membrane potential was collapsed upon addition of valinomycin in the presence of K+ . These data demonstrate that the plasma membrane ATPase of yeast cells is involved in electrogenic H+ translocation coupled to ATP hydrolysis since the purified enzyme incorporated in the liposomes is virtually free of mitochondrial F1F0-ATPase contaminant. J Cell Sci, 1981 Dec, 52, 271 - 87 Sequential alterations in the nuclear chromatin region during mitosis of the fission yeast Schizosaccharomyces pombe: video fluorescence microscopy of synchronously growing wild-type and cold-sensitive cdc mutants by using a DNA-binding fluorescent probe; Toda T et al.; Video-connected fluorescence microscopy was introduced to study the yeast nuclear chromatin region . It was defined as the nuclear area where a DNA-binding fluorescent probe 4',6-diamidino-2-phenylindole specifically bound and fluoresced . The 3-dimensional feature of the mitotic chromatin region was deduced by analysing the successive video images of a cell viewed at different angles . By investigating synchronous culture of the wild-type fission yeast Schizosaccharomyces pombe, we found sequential structural alterations in the chromatin region during mitosis . The steps found include the compaction of the chromatin region from the regular hemispherical form, the formation of a U-shaped intermediate and the rapid segregation into 2 daughter hemispherical forms . Six cs cdc mutants, apparently blocked in mitosis, were observed by fluorescence microscopy . Under the restrictive conditions their chromatin regions exhibited either hemispherical, compact, disk-like, U-shaped or partially segregated chromatin regions . Two mutants showed anomalous nuclear locations . The results of the temperature shift-up experiments of the highly reversible KM52 and KM108 strains supported the above scheme of sequential alterations in the chromatin region. J Biochem (Tokyo), 1981 Nov, 90(5), 1561 - 4 Cadmium-binding peptide induced in fission yeast, Schizosaccharomyces pombe; Murasugi A et al.; When S . pombe is cultured in a medium containing a high concentration of CdCl2 (1 mM), it grows for over 20 h accumulating Cd2+ in the cells . Simultaneously, Cd-binding peptides (Cd-BP1 and -BP2) are synthesized, and accumulated depending on the time after addition of Cd2+ to the culture medium . Apparent molecular weights of Cd-BP1 and -BP2 are 4,000 and 1,800, respectively . Both Cd-BPs are composed of common unit peptides, confirmed by chemical and physicochemical analyses. J Cell Sci, 1981 Oct, 51, 203 - 17 Polypeptide synthesis in cell cycle mutants of fission yeast; Dickinson DP; The cell cycle of a growing cel is characterized by 3 main periodic events: DNA synthesis mitosis and cell division . These events generally lie in a dependent sequence, in which one event cannot occur unless preceding events have occurred . The existence of dependent sequences of events raises the possibility that at least some of the gene products involved in the events are synthesized in a dependent sequence parallel to the observable events . To test this hypothesis, the patterns of polypeptide synthesis were investigated in 2 types of cell cycle mutant of the fission yeast Schizosaccharomyces pombe: temperature-sensitive cell cycle (ts cdc) mutants . which become blocked in cell cycle progress at the restrictive temperature; and wee I mutants, which are defective in size control over nuclear division, and which divide at a small size . Cells of mutants and wild-type cells were labelled with {35S{ sulphate under conditions designed to maximize any differences between the labelling patterns of wild-type and mutant cell polypeptides . The polypeptides were then separated by O'Farrell 2-dimensional gel electrophoresis, and the patterns compared . Although both types of mutation affect cell cycle control, and cause a considerable alteration in the relative proportions of cellular components, an examination of over 700 polypeptides detected on gels revealed no qualitative differences between wild-type and mutant cell polypeptides . These results suggest that a large majority of the more abundant polypeptides in the growing cell are synthesized independently of cell cycle controls directly related to DNA synthesis and division, and that the synthesis of these polypeptides can occur in the absence of normal progress through the cell cycle . Dependent sequences of gene expression do not appear to make a significant contribution to total polypeptide synthesis during the cell cycle, or to the occurrence of periodic cell cycle events such as mitosis . It is suggested that such cell cycle events may result largely through the reorganization of existing cellular components, rather than by the synthesis of new ones . An unsuccessful attempt was made to detect the wee I gene product on gels by surveying a range of mutants for changes in an individual spot . The limitations of gel electrophoresis for this type of survey, and other cell cycle experiments, are discussed. J Gen Microbiol, 1981 Oct, 126(Pt 2), 261 - 6 Effects of inhibitors on mitochondrial adenosine triphosphatase of Tetrahymena pyriformis ST; Unitt MD et al.; Mitochondrial adenosine triphosphatase (ATPase) of the ciliate protozoon Tetrahymena pyriformis ST is completely inhibited by antiserum prepared against F1-ATPase purified from Schizosaccharomyces pombe, and by naturally occurring inhibitor proteins from this yeast and from bovine heart mitochondria . An ATPase inhibitor protein is also present in extracts of T . pyriformis . Mitochondrial ATPase of T . pyriformis is only partially inhibited by the F0-ATPase inhibitors N,N'-dicyclohexylcarbodiimide, oligomycin, leucinostatin, triethyltin sulphate and venturicidin, and (at high titres) by the F1-ATPase inhibitors Dio-9, efrapeptin, 4-chloro-7-nitrobenzofurazan and spegazzinine . Aurovertin, citreoviridin and quercetin were not inhibitory . Resistance to inhibitors distinguishes this mitochondrial ATPase from all those previously examined. Eur J Biochem, 1981 Oct, 119(2), 341 - 5 The cdc 22 mutation by Schizosaccharomyces pombe is a temperature-sensitive defect in nucleoside diphosphokinase; Dickinson JR; A number of temperature-sensitive cdc- mutants of Schizosaccharomyces pombe that are affected in DNA replication, were screened for the absence of deoxynucleoside triphosphate(s) when blocked at their restrictive temperature . The preliminary screening simply involved analysis of perchloric acid-soluble cell extracts by two-dimensional thin-layer chromatography on poly(ethyleneimine)-impregnated cellulose . One mutant strain, cdc 22-M45, was found which apparently lacked dTTP . Pulse-labelling of intracellular nucleotides revealed that not only did dTTP become depleted, but that dTDP accumulated when this mutant was blocked by a temperature shift-up, indicating a defective nucleoside diphosphokinase . Nucleoside diphosphokinase from cdc 22-M45 was less active than that from wild-type strain 972 when assayed at high temperatures . The nucleoside diphosphokinase of the mutant also has an altered Km for dTDP at both permissive (25 degrees C), and at the restrictive (36.8 degrees C) temperatures . At the restrictive temperature the Km for dTDP of the mutant enzyme is more than 11-times greater than that of the wild type . Characterisation of the biochemical basis of the defect in this cdc- mutant has shown that in S . pombe, despite its having an apparently complex system of genetic control over progression through S-phase, one factor at least is merely availability of a nucleoside triphosphate precursor to DNA synthesis. Biochemistry, 1981 Sep 15, 20(19), 5576 - 86 Comparative study of an adenosine triphosphatase trigger-fused lipid vesicle and other vesicle forms of dimyristoylphosphatidylcholine; Dufour JP et al.; Several known forms of bilayer vesicles of dimyristoylphosphatidylcholine exhibit the gel to liquid-crystalline phase transition in the temperature range convenient for membrane enzyme reconstitution studies . This warrants a systematic investigation of their physical characteristics and their phase transition behaviors . We have employed electron microscopy, gel chromatography, 31P nuclear magnetic resonance, differential scanning microcalorimetry, and fluorescence spectroscopy to determine several physical parameters of the limiting size microvesicle (260 +/- 40 A), the larger vesicle form (900 +/- 100A) of Enoch and Strittmatter {Enoch, H . G., & Strittmatter, P . (1979) Proc . Natl . Acad . Sci . U.S.A . 76, 145}, the multilamellar vesicle, and, in particular, an ATPase-trigger-fused macrovesicle (950 +/- 200 A) . This latter vesicle form was produced by a spontaneous fusion of the complex of the plasma membrane ATPase of Schizosaccharomyces pombe and the lipid microvesicles at a low ratio of enzyme to vesicle concentrations, and at a low temperature (around 10 degrees C) . The ATPase-trigger-fused vesicles are unilamellar and have an intact ionic permeation barrier at 30 degrees C and a gel to liquid-crystalline transition temperature at 24.4 degrees C with a transition heat of 5.64 kcal/mol . Thus, this vesicle form should be a valuable tool for studying possible proton-pumping activity of this ATPase . In contrast to data found in the literature, which show lack of the pretransition for unilamellar microvesicles, we have observed the pretransition around 15 degrees C for all the vesicle forms examined . Moreover, the transition widths of unilamellar vesicles are much broader than those of the multilamellar vesicles, suggesting that in the latter system interlayer interactions may contribute to the cooperativity of the transition. Ann Microbiol (Paris), 1981 Sep-Oct, 132B(2), 241 - 55 {Microbial growth synchronization by immobilization onto solid carriers (author's transl)}; Navarro JM et al.; Immobilization of Saccharomyces uvarum onto solid carriers modifies their growth . When adsorbed onto glass or brick beads, synchronous yeast cycles and reduced generation times can be observed . The same phenomena take place when the cells are bound to the glass by glutaraldehyde . Synchronization of growth is also obtained with Schizosaccharomyces pombe amd Bacillus megaterium . These modifications do not result from an immobilization of cells in a particular state or from an interaction before linking. J Cell Sci, 1981 Aug, 50, 171 - 80 A search for synaptonemal complexes in Ustilago maydis; Fletcher HL; Germinating spores, germ-tubes (promycelia), gall tissue and spores developing in the gall were examined . No synaptonemal complexes (SCs) were found in any of these cell types . There are 3 possible explanations for this: (1) Ustilago maydis does not have SCs . This is the case in Schizosaccharomyces pombe (Olson, Eden, Egel-Mitani & Egel, 1978) and in many strains of Saccharomyces cerevisiae (e.g . see Byers & Goetch, 1975) . (2) The SC might occur in spores either in the gall or before germination when the spore wall was too solid to allow examination of the contents by the methods used . (3) The SC was present, but for a very short time, and most of the cells examined were in any case not undergoing meiosis, so the SCs were not seen . (Large numbers of spores were examined, but few spores germinate and undergo normal meiotic division; also a minority of the cells in the gall are forming spores at any one time.) The gall was found to contain uninucleate single cells (i.e . it is a yeast, as it is in artificial culture medium) and virtually all these cells were haploid, 1 in 3000 recovered cells was diploid . It appears that the haploids fuse to form a heterokaryotic or diploid cell immediately before spore formation . A heterokaryotic phase is presumed to exist to establish and maintain the infection. J Biol Chem, 1981 Jul 25, 256(14), 7298 - 304 An homologous in vitro assay for yeast nonsense suppressors; Tuite MF et al.; A cell-free translation system, from the yeast Saccharomyces cerevisiae, has been used to develop an in vitro assay for yeast UGA, ochre and amber suppressors . Amber suppression was assayed by read-through of the brome mosaic virus coat protein cistron UAG terminator . UGA suppression was assayed by read-through of the rabbit beta-globin UGA terminator and ochre suppression by read-through of the rabbit alpha-globin mRNA UAA terminator . Ochre suppression was increased 3-fold when the globin mRNA was heat denatured prior to translation; this was due to an increase in the synthesis of alpha-globin relative to beta-globin . Amber suppression was more efficient in vitro (46%) than ochre suppression (14%) . UGA suppression was also highly efficient in vitro, reaching almost 100% using a purified UGA suppressor tRNA from Schizosaccharomyces pombe . Unfractionated yeast tRNA, from a sup+ strain, contained a tRNA species able to suppress UGA termination codons in vitro, but no tRNA species able to suppress either UAA or UAG was found . This homologous in vitro assay for yeast nonsense suppressors will allow, for the first time, an approach to the biochemical analysis of yeast mutants that modify the efficiency of nonsense suppression in vivo. J Biol Chem, 1981 May 25, 256(10), 5058 - 63 Partial purification of RNase P from Schizosaccharomyces pombe; Kline L et al.; Ribonuclease P from the fission yeast Schizosaccharomyces pombe was partially purified using DEAE-cellulose and phosphocellulose column chromatography . The yeast RNase P enzyme cleaves Escherichia coli tRNATyr precursor to give tRNATyr containing its mature 5' end . The enzyme activity is inhibited after treatment with nucleases; this indicates the requirement of a nucleic acid component for activity . The enzyme purification was greatly facilitated by using a synthetically prepared radioactive ApApApCOH ligated to the 5'-terminal phosphate of E . coli tRNAfMet (ApApApCp-tRNA) substrate . (p denotes a {32P}phosphate group.) This substrate was cleaved by yeast RNase P to the mature tRNA and a tetranucleoside triphosphate ApApApCOH . The synthetic substrate allowed the utilization of a simple assay procedure measuring the trichloroacetic acid solubility of the ApApApC product, thus avoiding the more cumbersome gel electrophoric separation of reaction products. Toxicol Eur Res, 1981 May, 3(3), 131 - 40 Metabolic activation and mutagenicity of 4 vinylic monomers (vinyl chloride, styrene, acrylonitrile, butadiene); Duverger M et al.; The mutagenic activity and the metabolism of four vinylic monomers; vinyl chloride, styrene, acrylonitrile and butadiene are reviewed . Those chemicals are converted by the mixed function oxidases system of the endoplasmic reticulum into reactive intermediates which can interact with macromolecules within the cell . In order to examine the mutagenic activity of these compounds and their metabolites, different mutagenicity testing systems have been used: tests with S . typhimurium, E . coli, Schizosaccharomyces pombe, Saccharomyces cerevisiae, V79 Chinese Hamster cells, CHO cells, Drosophila melanogaster as well as evaluations of chromosome aberrations. J Biochem (Tokyo), 1981 May, 89(5), 1663 - 6 The nucleotide sequence of 5S ribosomal RNA from Schizosaccharomyces pombe; Komiya H et al.; The nucleotide sequence of 5S rRNA from the fission yeast, S . pombe, has been established by post labeling procedures combined with cataloging RNase T1- and A-oligonucleotides derived from unlabeled 5S rRNA . The sequence consists of 119 nucleotides without a modified base and shows more dissimilarities (at 38 positions) from that of S . cerevisiae than from that of humans (at 33 positions). J Biol Chem, 1981 Apr 25, 256(8), 3926 - 30 Molecular properties and active form of nonspecific acid phosphatase from Schizosaccharomyces pombe; Dibenedetto G et al.; Equilibrium sedimentation experiments of the native acid phosphatase indicate a dimer-tetramer dissociating nonequilibrating system with a dimer Mr = 180,000 g/mol . The hydrolysis of nitrophenylphosphate was used to determine the sedimentation coefficient of the active species . The s20,w value for the species which degrades nitrophenylphosphate is 13.52 +/- 0.46 S in 1% sucrose and 13.72 +/- 0.11 S in 1.3 M sodium chloride, corresponding to the Svedberg value of the tetramer species . Several lines of evidence are presented which, together with previous data, indicate that the Schizosaccharomyces pombe nonspecific acid phosphatase is composed of 4 identical or nearly identical polypeptide chains: a, equilibrium sedimentation analysis of the enzyme in denaturing agents indicates the presence of homogeneous material having Mr = 90,800 g/mol; b, digestion with carboxypeptidase A releases 0.82 mol of tyrosine/monomer molecular weight . Concomitant phosphatase inactivation occurred during the splitting off of the tyrosyl terminal residue . Furthermore, a unique NH2-terminal residue (histidine) was determined. Mutat Res, 1981 Mar, 81(1), 37 - 48 Spontaneous and UV-induced recombination in radiation-sensitive mutants of Schizosaccharomyces pombe; Grossenbacher-Grunder AM et al.; The rad alleles of 18 unlinked genes of S . pombe were tested for their level of spontaneous meiotic, spontaneous mitotic and UV-induced mitotic recombination in the ade7-50 x ade7-152 interval . The effects of these rad alleles on meiosis and cell morphology were also studied . None of these mutants showed a clear-cut reduction of spontaneous recombination rates, no matter whether they had lost or retained a caffeine-sensitive repair of UV-induced lesions, which has previously been interpreted as a recombinational pathway of DNA repair (Fabre, 1972a; Gentner, 1977; Gentner et al., 1978) . rad1-1 was the only mutant with a reduced frequency of UV-induced recombination . Some mutants displayed an increased frequency of mitotic recombination, either spontaneously (rad 15-P, rad 21-45), UV-induced (rad8-190) or both (rad2-44) . Previous hypothesis on the contribution of recombination to DNA repair in S . pombe are reconsidered in the light of these data. Can J Microbiol, 1981 Feb, 27(2), 184 - 91 Hybridization studies within the genus Schizosaccharomyces Lindner; Johannsen E; Hybridization studies based on the prototrophic selection technique, involving the use of auxotrophic mutants of strains of five accepted species of the genus Schizosaccharomyces, are reported . Intrastrain recombinants were recovered in five out of six tested parental pairs . Interstrain recombinants were recovered from crosses involving strains of S . japonicus and strains of S . pombe . No recombinants were recovered in 62 interspecific crosses involving all possible combinations of the six representatives of the genus. Cell Biol Int Rep, 1981 Feb, 5(2), 187 - 94 Inhibition of RNA synthesis in yeast protoplasts by a peptide factor from Tetrahymena cells; Andersen HA et al.; Protoplasts of Schizosaccharomyces pombe, grown on a rich nutrient medium, were treated with a peptide factor isolated from cultures of the protozoan Tetrahymena pyriformis . The peptide factor is known to inhibit RNA synthesis in Tetrahymena . It has now been shown that the peptide factor also inhibits RNA synthesis in yeast protoplasts without affecting protein synthesis. Z Allg Mikrobiol, 1981, 21(3), 261 - 6 Multiple septation in multinuclear protoplasts of Schizosaccharomyces pombe; Havelkova M; The dependence of septation on karyokinesis was studied in protoplasts of the fission yeast Schizosaccharomyces pombe . The mononuclear protoplast produces a single centrally located septum . In multinuclear reverting protoplasts, on the other hand, the formation of a single septum was a rare event . In each protoplast instead of one, two to six septa were formed . These findings suggest some closer relations between the formation of septa and the number of nuclei present in the protoplast . Our results obtained with protoplasts also imply that the initiation of septum formation is possible only in the presence of a complete cell wall . In reverting multinuclear protoplasts undergoing more than one mitosis, no septation is initiated until the cell wall has been completed . Only the complete cell wall can induce the formation of one or several septa in mono- and multinuclear protoplasts, respectively. Arzneimittelforschung, 1981, 31(12), 2142 - 4 Mutagenicity studies on fenticonazole, a new antifungal imidazole derivative; Veronese M et al.; The forward mutational assay on Schizosaccharomyces pombe and the mitotic gene conversion assay on Saccharomyces cerevisiae were performed in order to verify whether alpha-(2,4-dichlorophenyl)-beta,N-imidazolylethyl 4-phenylthiobenzyl ether nitrate (fenticonazole, Rec 15/1476) shows a potential mutagenicity . In both tests the drug does not seem to possess any mutagenic activity when compared with mutagenic standards. Mol Gen Genet, 1981, 183(1), 32 - 6 Induction of trehalase activity on a nitrogen-free medium: a sporulation-specific event in the fission yeast, Schizosaccharomyces pombe; Inoue H et al.; Kinetic experiments with synchronously sporulating cultures of a homothallic h90 strain of Schizosaccharomyces pombe showed that trehalase activity abruptly increased in the late sporulation process, coinciding with the appearance of visible spores . Trehalase activity was absent in vegetative cells . A set of strains different in genetic constitution at the mating type loci was tested for induction of trehalase on nitrogen-free sporulation medium . The appearance of trehalase activity on the sporulation medium was observed only in sporulating cultures; cultures of homothallic strains (h 90) and diploid strains heterozygous for mating type (h +/h-), and mixed cultures of heterothallic h+ and h- strains . Trehalase activity was not induced in nonsporogenic strains: heterothallic haploid strains (h+ and h-), diploid strains homozygous for mating type (h+/h+ and h-/h-) and the homothallic strain harboring the mutation in the mat2 gene, which was unable to undergo the first meiotic division . Trehalose accumulation on the sporulation medium was observed solely in the sporulating cultures . These results led us to conclude that the induction of trehalase activity as well as the accumulation of trehalose in the medium lacking nitrogen sources was a sporulation-specific event under the control of the mating type genes. Mol Gen Genet, 1981, 182(2), 252 - 4 Synthesis of mitochondrial DNA during the cell cycle of the petite negative yeast Schizosaccharomyces pombe; Del Giudice L et al.; Synthesis of mitochondrial DNA (mitDNA) and nuclear DNA (nucDNA) during growth of synchronously dividing cultures of Schizosaccharomyces pombe (S . pombe) was followed by pulse labelling with radioactive adenine and determination of its rate of incorporation into total protoplast DNA and into the DNA of DNase-treated mitochondria at different stages of the cell cycle . It could be demonstrated that both mitDNA and nucDNA were synthesised discontinuously and at different points in the cell cycle. Mol Gen Genet, 1981, 182(1), 119 - 24 Cell division cycle mutants altered in DNA replication and mitosis in the fission yeast Schizosaccharomyces pombe; Nasmyth K et al.; A total of 59 new temperature sensitive cdc mutants are described which grow normally at 25 degrees C but become blocked at DNA replication or mitosis when incubated at 36 degrees C . Thirty-nine of the mutants are altered in cdc genes which have been identified previously . The remaining 20 mutants define 10 new cdc genes . These have been characterised physiologically, and 6 of the genes (cdc 17, 20, 21, 22, 23, 24) were found to be required for DNA replication, 2 for mitosis (cdc 27, 28), and 2 (cdc 18, 19), could not be unambiguously assigned to either DNA replication or mitosis but were definitely required for one or the other . Three genes, the previously identified cdc 10, and cdc 20, 22 are likely to be required for the initiation of DNA replication . Mutants in two genes, cdc 17, 24 undergo bulk DNA synthesis at 36 degrees C, but this DNA is defective . In the case of cdc 17 the defect is in the ligation of Okazaki fragments . cdc 23 is required for bulk DNA synthesis, whilst cdc 21 may possibly be required for the initiation of a particular sub-set of replicons . A previously isolated mutant cdc 13.117 is also further described . This mutant becomes blocked in the middle of mitosis with apparently condensed chromosomes. Mol Gen Genet, 1981, 181(3), 306 - 8 Nucleo-cytoplasmic interactions in the petite negative yeast Schizosaccharomyces pombe . Inhibition of nuclear and mitochondrial DNA syntheses in the absence of cytoplasmic protein synthesis; Del Giudice L et al.; In the petite positive yeast, Saccharomyces cerevisiae, cycloheximide selectively inhibits protein synthesis on cytoplasmic ribosomes, and, as a consequence, nuclear DNA synthesis . Mitochondrial DNA, however, is synthesized for 4-6 h after cessation of protein synthesis . In this paper we show that in contrast to Saccharomyces cerevisiae, synthesis of mitochondrial and nuclear DNA is tightly coordinated in the petite negative yeast Schizosaccharomyces pombe, since inhibition of cytoplasmic protein synthesis leads immediately to cessation of both nuclear and mitochondrial DNA synthesis. Mol Gen Genet, 1981, 184(3), 465 - 70 Cloning of mitochondrial DNA from the petite negative yeast Schizosaccharomyces pombe in the bacterial plasmid pBR322; Del Giudice L; The entire mitochondrial (mt) genome of the yeast Schizosaccharomyces pombe (S . pombe) was cloned in the BamHI site of the Escherichia coli plasmid pBR322 . Three lines of evidence demonstrate that the complete mtDNA molecule was amplified without rearrangement or partial loss . First, restriction of the hybrid plasmid with BamHI led to the recovery of two fragments corresponding to the linearized plasmid and the BamHI-cut mtDNA . Second, restriction of cloned and native mtDNA with HindIII revealed identical fragments . Third, mitochondrial ribosomal RNA hybridized to the same HindIII fragments from cloned mtDNA and from mtDNA isolated from mitochondria. J Cell Sci, 1980 Dec, 46, 399 - 431 Arginase and sucrase potential in the fission yeast Schizosaccharomyces pombe; Benitez T et al.; The induction potentials of 2 enzymes, sucrase and arginase, have been measured in asynchronous and synchronous cultures of the fission yeast Schizosaccharomyces pombe . The effect on potential of inhibiting DNA synthesis is asynchronous cultures has been studied using 2 temperature-sensitive dcd mutants, one blocked in DNA replication and the other blocked in mitosis . The results show that despite inhibition of DNA synthesis, sucrase and arginase potential both continue to increase exponentially for at least a generation of growth after shifting the cdc mutants from the permissive to the restrictive temperature . A second method of inhibiting DNA synthesis, using deoxyadenosine, has also been tested . Cells treated with deoxyadenosine stop the increase in potential for a short period . However, experiments carried out using a cdc mutant together with deoxyadenosine show that the block to the increase in potential is due to a side effect of the inhibitor . It appears that increase in potential is not dependent upon continued DNA replication, and that gene dosage does not control potential in the normal cell cycle . This conclusion is supported by measurements on mutants of different cell sizes . potential is proportional to size (protein content per cell is asynchronous culture) and not to DNA content . Although potential is not gene limited in normal cells, it does appear to be so in the abnormally large cells produced by a cdc block . If cdc mutants of different sizes are grown asynchronously, and DNA synthesis is inhibited by a shift to the restrictive temperature, there is no increase in potential . This critical ratio is different for the 2 enzymes, but for each enzyme it is similar in all the mutants tested . When large cells (produced by a mutant block for 4.5 h) are shifted down in temperature, there are synchronous rounds of DNA synthesis and division and also step doublings in potential . In synchronous cultures of wild type cells, both enzymes show a stepwise doubling of potential at 0.2 of a cycle after DNA replication . In synchronous cultures of cdc mutants blocked either in replication or in mitosis, the potential steps continue with the normal timing observed in wild type cells . This shows that the steps are not dependent on the events of the DNA-division cycle but are controlled by another mechanism . Attainment of a critical size might be part of this mechanism, but tests with size mutants argue against this. Nature, 1980 Nov 27, 288(5789), 401 - 4 Genes which control cell proliferation in the yeast Saccharomyces cerevisiae; Sudbery PE et al.; In many eukaryotes it is thought that cell proliferation is regulated at a point in G1 close to the initiation of DNA synthesis . Hartwell and his colleagues have shown such a point in G1 phase in the budding yeast, Saccharomyces cerevisiae, defined by the cdc 28 mutation . He has termed this point 'start' and showed that for cells to proceed beyond start, initiate DNA synthesis and produce a bud, various conditions must be met . Two of these conditions are the presence of adequate nutrients in the medium and attainment of a critical size . We identify here some of the genes controlling start by isolating mutants which are altered with respect to the conditions in which start occurs . Two types of mutant have been isolated . One results in bud initiation when the parent cell is only half the size at which bud initiation occurs in wild-type cells . Such mutants define a single gene, whi-1, and they are apparently analogous to the size mutants isolated by Nurse and his colleagues in Schizosaccharomyces pombe . A second type of mutation affects a second gene, whi-2, which is involved in the mechanism whereby cells arrest in G1 in stationary phase . whi-2- cells growing exponentially initiate buds at the same size as wild-type cells . In stationary phase, however, whi-2- cells growing exponentially initiate buds at the same size as wild-type cells . In stationary phase, however, whi-2- cells, unlike wild-type cells, are predominantly budded and are smaller than wild-type cells. J Biol Chem, 1980 Nov 25, 255(22), 10591 - 8 Phospholipid reactivation of the purified plasma membrane ATPase of yeast; Dufour JP et al.; The plasma membrane ATPase of the yeast Schizosaccharomyces pombe solubilized by lysolecithin and purified by centrifugation through a sucrose gradient is essentially inactive . The phospholipid distribution in the sucrose gradient indicates that inactivation of the ATPase may result from the partial delipidation occurring during purification . Taking into account the 100,000 daltons of the ATPase polypeptide, it is concluded that 74 mol of phospholipids are bound per mol of purified ATP monomer . The ATPase so purified is reactivated simply by mixing the enzyme with preformed lipid micelles or vesicles . Lysolecithins reactivate the enzyme at concentrations around the critical micellar concentration . Gel exclusion chromatography indicates that the enzyme binds reversibly to the lysolecithin micelles . On the other hand, lecithins of varying chain length and unsaturation reactivate the enzyme to different extents and with different efficiencies . In addition, from binding studies, it is observed that each saturated lecithin combines equally well with the ATPase . Using other diacylphospholipids no specificity for the polar head group is observed . Moreover, cardiolipin microvesicles is shown to bind all the protein but not to restore the enzyme activity . From lipid-reactivation titration curves . Arrhenius plots, and physical data of the phospholipids, it is concluded that the major parameter which governs the optimal reactivation of ATPase is the ability of the phospholipids to form amphipathic structures (micelles or vesicles) of sufficient fluidity and hydrophobicity . From these results, a coherent description can be provided for the protein-lipid interactions occurring during solubilization, purification, and the lipid reactivation of the yeast plasma membrane ATPase. J Bacteriol, 1980 Nov, 144(2), 836 - 9 Induction of arginase and ornithine transaminase in the fission yeast Schizosaccharomyces pombe; Benitez T et al.; The induction of arginase and ornithine transaminase in the fission yeast Schizosaccharomyces pombe requires the absence of ammonia and the presence of the inducer arginine . It seems that immediate arginase degradation is initiated by starved cells or ones from which arginine has been removed. Genetics, 1980 Nov, 96(3), 627 - 37 Regulatory genes controlling mitosis in the fission yeast Schizosaccharomyces pombe; Nurse P et al.; Fifty-two wee mutants that undergo mitosis and cell division at a reduced size compared with wild type have been genetically analyzed . The mutants define two genes, wee1 and cdc2, which control the timing of mitosis . Fifty-one of the mutants map at the wee1 locus, which is unlinked to any known cdc gene . One of the wee1 alleles has been shown to be nonsense suppressible . The 52nd were mutant maps within cdc2 . Previously, only temperature-sensitive mutants that become blocked at mitosis have been found at the cdc2 locus . The simplest interpretation of these observations is that wee1+ codes for a negative element or inhibitor, and cdc2+ codes for a positive element or activator in the mitotic control . The gene dosage of wee1+ plays some role in determining the timing of mitosis, but the gene dosage of cdc2+ has little effect . However, some aspect of the cdc2 gene product activity is important for determining when mitosis takes place . The possible roles of wee1 and cdc2 in the mitotic control are discussed, with particular reference to the part they may play in the monitoring of cell growth rate, both of which influence the timing of mitosis. J Biol Chem, 1980 Oct 10, 255(19), 9353 - 7 The purified plasma membrane ATPase of the yeast Schizosaccharomyces pombe forms a phosphorylated intermediate; Amory A et al.; An acid slab gel electrophoresis method of high-resolving power allows detection of a phosphorylated form in the purified ATPase of the yeast Schizosaccharomyces pombe and identification of this catalytic intermediate among the different phosphopeptides of a plasma membrane preparation . At a maximum steady state rate of MgATP hydrolysis by the membrane-bound ATPase, 20 to 40% of the ATPase subunits of 100,000 daltons are in a phosphorylated form, while only 0.8% of the subunits of the purified ATPase are phosphorylated under the same conditions . The phosphorylated intermediate reaches the steady state level in less than 2 s and rapidly turns over . The phosphorylated substance is cleaved by hydroxylamine and is relatively stable in acids but is readily hydrolyzed in alkaline or in acid alcoholic media . These results suggest that the intermediate is an acylphosphate . The phosphorylation reaction has an apparent Km value of 3.0 mM MgATP for the plasma membrane-bound ATPase and 0.6 mM MgATP for the purified ATPase . Plasma membranes contain several other minor phosphorylated components whose kinetic behavior is typical of phosphorylation by protein kinase . Artifactual production of two forms of the ATPase by phenylmethanesulfonyl fluoride-sensitive proteases liberated during cell disruption is also demonstrated. Mutat Res, 1980 Oct, 79(2), 141 - 50 The use of organic solvents in mutagenicity testing; Abbondandolo A et al.; 13 organic substances (dimethylsulfoxide, methanol, ethanol, n-propyl alcohol, sec-butyl alcohol, tert-butyl alcohol, dl-sec-amyl alcohol, ethylene glycol, ethylene glycol monomethyl ether, 1,4-diethylene dioxide, acetone, methyl acetate and formamide) were considered from the standpoint of their use as solvents for water-insoluble chemicals to be tested for mutagenicity . First, the effect of these solvents on cell survival was studied in the yeast Schizosaccharomyces pombe and in V79 Chinese hamster cells . 8 solvents showing relatively low toxicity on either cell system (dimethylsulfoxide, ethanol, ethylene glycol, ethylene glycol monomethyl ether, 1,4-diethylene dioxide, acetone, methyl acetate and formamide) were tested for their effect on aminopyrine demethylase . 4 solvents (ethanol, 1,4-diethylene dioxide, methyl acetate and formamide) showed a more or less pronounced adverse effect on the microsomal enzymic activity . The remaining 4 and methanol (whose effect on aminopyrine demethylase was not testable) were assayed for mutagenicity in S . pombe . They all gave negative results both with and without the post-mitochondrial fraction from mouse liver. J Bacteriol, 1980 Oct, 144(1), 17 - 21 Synchronization of cell division in microorganisms by percoll gradients; Dwek RD et al.; We describe a method for obtaining synchronously dividing cells of bacteria (Escherichia coli B and K-12 and Bacillus subtilis 168) and fission yeasts (Schizosaccharomyces pombe) by the use of Percoll density gradients. Nature, 1980 Sep 25, 287(5780), 361 - 3 In vitro suppression of UGA codons in a mitochondrial mRNA; De Ronde A et al.; Although both prokaryotic and eukaryotic messenger RNAs can be easily translated in heterologous protein-synthesizing systems, attempts to achieve correct synthesis of mitochondrial proteins by translation of mitochondrial mRNAs in such systems have failed . In general, the products of synthesis are of low molecular weight and presumably represent fragments of mitochondrial proteins . These fragments display a strong tendency to aggregate . Explanations have included the use by mitochondria of codons requiring a specialized tRNA population and the fortuitous occurrence within genes of purine-rich sequences resembling bacterial ribosome binding sites . In addition, the long 5'-leader sequences present in many mitochondrial (mt) RNAs may also contribute to difficulties in mRNA recognition by heterologous ribosomes . Recent sequence analysis of human mtDNA suggests that the genetic code used by mammalian mitochondria deviates in a number of respects from the 'universal' code, the most striking of these being the use of the UGA termination codon to specify tryptophan . That this may also apply in yeast mitochondria has been shown by Fox and Macino et al., thus providing an obvious and easily testable explanation for the inability of heterologous systems to synthesize full-length mitochondrial proteins . We confirm this explanation and describe here the in vitro synthesis of a full-length subunit II of yeast cytochrome c oxidase in a wheat-germ extract supplemented with a partially purified mitochondrial mRNA for this protein and a UGA-suppressor tRNA from Schizosaccharomyces pombe. Cell, 1980 Sep, 21(2), 509 - 16 Dimeric transfer RNA precursors in S . pombe; Mao J et al.; Sequence analysis of a Schizosaccharomyces pombe DNA fragment revealed two tRNA coding regions separated by a seven nucleotide spacer . the 5'-proximal tRNA gene encodes a tRNAUCGSer sequence, which is interrupted by a 16 nucleotide intron at the 3' side of the base adjacent to the anticodon . The second tRNA gene encodes an initiator tRNAMet sequence . This DNA fragment, cloned into pBR322, was used as template for in vitro transcription in a nuclear extract of Xenopus oocytes . The tRNA genes were transcribed into one RNA precursor which contained both tRNA sequences . The primary transcription product initiates with pppG, contains a 9 nucleotide leader sequence, a 16 nucleotide intron, a 7 nucleotide spacer between the two tRNA molecules and an 8--9 nucleotide trailer sequence . RNA initiation was only observed upstream of the 5'-proximal tRNASer . We used RNA analysis to establish a sequence of the enzymatic steps of tRNA maturation in the nuclear extract . The first step in processing the dimeric precursor is an endonuclease cleavage which generates the mature 5' end of the tRNAMet . Further steps include the removal of the flanking sequences and addition of the CCAOH 3' terminus . The last step is the splicing of the tRNASer precursor to remove the intervening sequence. Genetics, 1980 Sep, 96(1), 237 - 62 Intracellular population genetics: evidence for random drift of mitochondrial allele frequencies in Saccharomyces cerevisiae and Schizosaccharomyces pombe; Thrailkill KM et al.; We report evidence for random drift of mitochondrial allele frequencies in zygote clones of Saccharomyces cerevisiae and Schizosaccharomyces pombe . Monofactorial and bifactorial crosses were done, using strains resistant or sensitive to erythromycin (alleles Er, Es), oligomycin (Or, Os), or diuron (Dr, Ds) . The frequencies of resistant and sensitive cells (and thus the frequencies of the resistant and sensitive alleles) were determined for each of a number of clones of diploid cells arising from individual zygotes . Allele frequencies were extremely variable among these zygote clones; some clones were "uniparental," with mitochondrial alleles from only one parent present . These observations suggest random drift of the allele frequencies in the population of mitochondrial genes within an individual zygote and its diploid progeny . Drift would cease when all the cells in a clone become homoplasmic, due to segregation of the mitochondrial genomes during vegetative cell divisions . To test this, we delayed cell division (and hence segregation) for varying times by starving zygotes in order to give drift more time to operate . As predicted, delaying cell division resulted in an increase in the variance of allele frequencies among the zygote clones and an increase in the proportion of uniparental zygote clones . The changes in form of the allele frequency distributions resembled those seen during random drift in finite Mendelian populations . In bifactorial crosses, genotypes as well as individual alleles were fixed or lost in some zygote clones . However, the mean recombination frequency for a large number of clones did not increase when cell division was delayed . Several possible molecular mechanisms for intracellular random drift are discussed. Can J Microbiol, 1980 Sep, 26(9), 1165 - 8 Growth of yeasts on D-xylulose 1; Wang PY et al.; Nine of eleven yeasts of different species or genera grew in the presence of air on the intermediate of D-xylose catabolism, D-xylulose (D-threo-pentulose) . Growth on this substrate was efficient as judged by the optical density in stationary phase being generally similar to that after growth on glucose . Yeasts which grew on D-xylose also did so on D-xylulose, but among those which grew are included several which utilise neither D-xylose nor xylitol: Saccharomyces cerevisiae, Saccharomyces carlsbergensis, and Schizosaccharomyces pombe . Since catabolism of a sugar generally requires an initial phosphorylation step, growth of these strains suggests that they contain an enzyme which can function as a D-xylulose kinase . The D-xylulose-5-phosphate formed thereby is considered to enter the pentose-phosphate pathway . Glucose-grown inocula of S . carlsbergensis and Schizosaccharomyces pombe, and of several other yeasts, began to grow logarithmically when placed on D-xylulose with no apparent delay, or one which was minimal, suggesting that the D-xylulose kinase was already present in such cells, or was rapidly induced . Petites of S . cerevisiae did not grow on D-xylulose indicating that, in this species, mitochondria are involved in its utilisation. Arch Microbiol, 1980 Aug, 127(1), 11 - 6 Lysis of growing fissin-yeast cells induced by aculeacin A, a new antifungal antibiotic; Miyata M et al.; Cells of Schizosaccharomyces pombe grown in the presence of aculeacin A, a peptide antibiotic, were lysed resulting the death of cells . Under high osmolarity, the cellular lysis induced by aculeacin A was considerably reduced . The use of synchronous-culture systems distinguished cell elongation from cell division revealed that the sites of aculeacin A-induced lysis on the fission yeast were the end(s) and the cell plate region, corresponded to the regions of the cell wall synthesis . Aculeacin A-resistant survivors exhibited morphological alterations which were swollen at one or both ends of the cell and appeared drumstick or dumbbel like; the wall of the bulge region was observed to be stained with a fluorescent brightner, as well as that of the cell plate region . These effects of aculeacin A are discussed as compared with effects of 2-deoxy-D-glucose. J Gen Microbiol, 1980 Feb, 116(2), 525 - 8 Genetical analysis of a sterile mutant by protoplast fusion in the fission yeast Schizosaccharomyces pombe; Thuriaux P et al.; The genetical analysis, by protoplast fusion, of the sterile strain ED22 of Schizosaccharomyces pombe is described . Two major mutations are harboured by this strain . One, cdc 25.22, is conditionally defective in mitosis . The other mutation, ste 1.1, causes sterility in strains of h-, h+ or mat 2.102 mating-type . Sterility is due to the failure of cell agglutination . We present evidence that ste 1.1 is defective in the production of a non-diffusible and non-mating-type specific factor . ste 1 and cdc 25 both map on chromosome I and are loosely linked. Can J Microbiol, 1980 Feb, 26(2), 250 - 4 Microfilaments and cytoplasmic microtubules in cell division cycle mutants of Schizosaccharomyces pombe; Streiblova E et al.; The occurrence of axial cytoplasmic microtubules (25 nm in diameter) and of microfilaments (7 nm in diameter) associated in bundles just below the plasma membrane of the yeast Schizosaccharomyces pombe is described . Both types of cytoplasmic filamentous structures were present in the cell division cycle mutant cdc 12-112 of this fungus incubated for 6 h at the restrictive temperature of 35 degrees C . Microtubules and microfilaments probably function in septum formation and (or) in the volume-related control of the terminal phenotype of the mutant. Biophys J, 1980 Jan, 29(1), 1 - 11 Oscillations of redox states in synchronously dividing cultures of Acanthamoeba castellanii and Schizosaccharomyces pombe; Bashford CL et al.; The redox state of the mitochondria of Acanthamoeba castellanii and Schizosaccharomyces pombe was assessed with a flying-spot fluorometer (Chance et al . 1978 . Am . J . Physiol . 235:H 809) that provides excitation appropriate for oxidized flavoprotein or reduced pyridine nucleotide . Fluorescence signals could be resolved from the thin films of cultures that were only one cell deep . In both organisms anoxia was associated with an increased pyridine nucleotide and decreased flavoprotein fluorescence . The addition of mitochondrial uncoupling agents increased the flavoprotein fluorescence and the fluorometer was able to resolve uncoupler-sensitive and uncoupler-insensitive fractions of S . pombe cultures . In both synchronous and asynchronous cultures of A . castellanii and S . pombe the mitochondrial redox state oscillates with a period of 4.5 +/- 1.0 min . Oscillations with much longer period, of the order of an hour, are observed in synchronous cultures and these oscillations correlate with similar oscillations in respiratory rate, uncoupler sensitivity, and adenine nucleotide pool sizes . The results are consistent with the hypothesis that synchronous cultures of A . castellanii and S . pombe oscillate between the ADP-limited (state 4) and ADP-sufficient (state 3) respiratory states, i.e., exhibit in vivo respiratory control. Mol Gen Genet, 1980, 180(1), 231 - 4 Genetic analysis of resistant mutants to antimitotic benzimidazole compounds in Schizosaccharomyces pombe; Yamamoto M; Mutants resistant to the antimitotic compounds thiabendazole and methyl-2-benzimidazole-carbamate were isolated and analyzed genetically in the fission yeast . Schizosaccharomyces pombe . They comprised three groups in terms of genetic linkage . Mutants in one linkage group (ben1) differed phenotypically from those in the other two (ben2 and ben3) . The former were resistant to the compounds at any physiological temperature tested, whereas the latter exhibited temperature dependent resistance . Through tetrad analysis, ben1 was mapped at the rightmost part of chromosome II, and ben2 was mapped near the centromere of the same chromosome . Haploidization experiments revealed the location of ben3 on chromosome II . By analogy with Aspergillus nidulans, it is suggested that one of these ben genes may code for tubulin. Biochem J, 1979 Dec 15, 184(3), 555 - 63 The reaction of cytochrome oxidase with oxygen in the fission yeast Schizosaccharomyces pombe 972h- . Studies at subzero temperatures and measurement of apparent oxygen affinity; Poole RK et al.; 1 . Cytochrome alpha 3 in whole-cell suspensions of the fission yeast Schizosaccharomyces pombe reacted in the reduced form with CO to give a photodissociable CO complex with absorption maxima at 429, 543 and 591 nm in CO-liganded reduced-minus-reduced difference spectra . 2 . Other CO-bound haemoproteins, cytochromes P-420 and P-450, were not photodissociated under the conditions employed . 3 . Measurements of the rates of reassociation of CO with cytochrome alpha 3 after flash photolysis over the temperature range from -101 to -109 degrees C gave a value for Eact . of 28.6 kJ/mol . 4 . Between -94 and -106 degrees C, O2 reacted with cytochrome oxidase in intact cells to give an oxygenated intermediate (compound A) . 5 . At -70 degrees C compound A was converted into a second spectrally distinct intermediate (compound B) . 6 . Electron transport, indicated by the oxidation of cytochromes alpha + alpha 3 and cytochrome c, did not occur until the temperature was raised to -50 degrees C . 7 . At room temperature cytochfome oxidase was oxidized to 50% of its steady-state concentration by 0.35 microM-O2. J Gen Microbiol, 1979 Nov, 115(1), 255 - 8 Germination and outgrowth of Schizosaccharomyces pombe spores isolated by a simple batch centrifugation technique; Johnke R et al.; Spores of the fission yeast Schizosaccharomyces pombe have been separated from vegetative cells by a simple and rapid centrifugation (800 g for 20 min) through a 35% Hypaque solution to a purity greater than 95% . Approximately 35% of the spores were recovered . Regrowth in EMM2 plus glucose showed that over 97% of the spores germinated within the first 2 h and outgrowth continued between 5 and 10 h . Sucrose induced germination in greater than 95% of the spores with a 1 h delay and outgrowth in 50% of the spores with a 3 h delay . There was little protein synthesis during germination but the protein content increased linearly coincident with outgrowth . The RNA content increased slightly during germination, but increased linearly 1 h before the onset of outgrowth and protein synthesis . After 8 h of regrowth, coincident with the onset of DNA synthesis, the rate of RNA synthesis was accelerated . The DNA content had increased 1.7-fold after 10 h of regrowth from a haploid level of 1.36 x 10(-8) microgram spore-1. Mutat Res, 1979 Nov, 63(1), 11 - 9 Reversion of nonsense mutants induced by 4-nitroquinoline-1-oxide in Schizosaccharomyces pombe; Janner F et al.; We have studied the reversion of 8 nonsense alleles located in 7 different genes of Schizosaccharomyces pombe using 4-nitroquinoline-1-oxide (NQO) as a mutagenic agent . The nonsense mutants of S . pombe have been classified according to their suppressibility by defined opal and ochre suppressors into a class of efficiently suppressed opal and a class of inefficiency suppressed ochre mutants . The UGA alleles tested all revert consistently with NQO, in agreement with the high specificity of this mutagen for G-residues reported for bacteria and yeast . The UAA alleles show a lack or a low level of reversion with NQO . This low level of reversion is due to the low level of non-G-specific transversions at A sites of the UAA triplet . Within each class of nonsense mutants the extent of induction is site-dependent . We conclude that NQO acts predominantly on G-residues in S . pombe. Nucleic Acids Res, 1979 Oct 25, 7(4), 1059 - 65 The nucleotide sequence of tRNA tyrosine from the fission yeast Schizosaccharomyces pombe; Vogeli G; The sequence of tRNA tyrosine from the fission yeast Schizosaccharomyces pombe is pCUCCUGAUm1 GGUG psi AGDDGGDDAUCACACor (psi) CCGGUG psi Ai6 AACCGGUUGm7 GUm5C GCUAGT psi CGm1 AUUCUGGUCAGGAGACCAOH . This sequence differs in 30 nucleotides from the tRNA-Tyr seqence of the budding yeast Saccharomyces cerevisiae . It has a unique anticodon stem of only four GC base pairs . The normal fifth pair position of nucleotide 28-44 is occupied by a C-U and in 20% of the tRNA-Tyr molecules it is psi-U . This unusual feature and its implications are considered in the discussion. Mol Gen Genet, 1979 Oct 3, 176(2), 301 - 2 Promotion of uniparental inheritance of mitochondrial drug resistance by delayed division of yeast zygotes; Wolf K et al.; Uniparental inheritance of mitochondrial markers conferring resistance to 3 (3,4-dichlor-phenyl)-1,1-dimethylurea (diuron or DCMU) and antimycin in the fission yeast Schizosaccharomyces pombe is promoted by delaying first division of zygotes. Mol Gen Genet, 1979 Oct 2, 176(1), 129 - 38 Variation of gene conversion and intragenic recombination frequencies in the genome of Ascobolus immersus; Nicolas A; Eighty mutants in 17 ascospore character genes were studied for their conversion patterns . The correlation between conversion pattern and mutagenic origin, previously found in genes b1 and b2 was extended to all the genes studied . Aberrant 4:4 asci were found in most genes irrespective of their conversion frequency . From gene to gene, the conversion frequency showed an almost 100 times variation . The frequency of intragenic recombination also showed sharp variation from gene to gene . The mean conversion frequency and the maximal intragenic recombination frequency were shown to be highly correlated in 5 genes for which these 2 values are known . This correlation was extended to 12 other genes in other Ascomycetes: Saccharomyces cerevisiae, Schizosaccharomyces pombe, Neurospora, and Sordaria . From this study it is concluded that, 1) the probability of hybrid DNA formation undergoes considerable changes according to the region of the genome; 2) the intragenic recombination frequency primarily reflects the frequency of hybrid DNA formation rather than the physical length of the gene; 3) for a given physical distance on the DNA, a similar fraction of the gene conversion events lead to recombination in the 5 Ascomycetes. J Cell Sci, 1979 Oct, 39, 215 - 33 The effect of cell mass on the cell cycle timing and duration of S-phase in fission yeast; Nasmyth K et al.; Two isotopic methods for measuring DNA replication in the fission yeast Schizosaccharomyces pombe are described . The first is a method for measuring the total quantity of {3H}uracil incorporated into DNA after pulse labelling . The second is a means of detecting DNA replication in single cells by autoradiography . Both of these techniques have been used to investigate the timing and duration of S-phase in a series of mutant strains whose cell mass at division varies over a 3-fold range . The results support the hypothesis that in S . pombe there are 2 different controls over the timing of S-phase: an attainment of a critical cell mass and a dependency upon the completion of the previous mitosis coupled with a short minimum time in G1 . Strains whose cell mass at birth is above this critical level initiate DNA replication almost immediately after septation, that is, very soon after the previous mitosis . Strains whose cell mass at birth is below the critical level do not initiate replication until the critical cell mass is attained . The duration of S-phase has been estimated from the proportion of cells whose nuclei are labelled after a pulse of given duration . S-phase is short in S . pombe, lasting only about 0.1 of a cell cycle in wild type . Cell mass at S-phase does not have any consistent effect on this length . We have also investigated the degree of synchrony of S-phase initiation in daughter cells, and have found that, in a cell cycle 240 min long, their S-phases are initiated within 1--2 min of each other . This result indicates that between sisters variability in the duration of the G1 phase is small compared with variability in the total cell cycle time, and argues against the hypothesis that the rate of cell cycle traverse is determined by a random transition in G1. Mikrobiologiia, 1979 Sep-Oct, 48(5), 887 - 91 {New remote hybrids between Saccharomyces and Schizosaccharomyces}; Kosikov KV et al.; Crossing the cells of Saccharomyces (diploid) and Schizosaccharomyces (haploid) cells as well as using genetic markers (adenine dependent mutants) and selective media produced remote hybrids . The hybrid cultures possessed the intermediate type of inheritance in a number of properties . Along with budding typical of Saccharomyces, partitions characteristic of Schizosaccharomyces were encountered . The shape and size of cells and some physiological properties were found to vary in the course of vegetative growth (no spores were formed by the hybrid cultures) . Conditions are discussed which favour remote hybridization of yeast cultures. Proc Natl Acad Sci U S A, 1979 Jul, 76(7), 3289 - 93 Initiator tRNAs have a unique anticodon loop conformation; Wrede P et al.; Transfer RNA (tRNA) molecules have been labeled with 32P at the 5' end and subjected to S1 nuclease digestion . The products were analyzed by high-resolution gel electrophoresis . Three initiator tRNAs and six chain-elongating tRNAs were examined . S1 nuclease cleaved Escherichia coli tRNAfMet, yeast tRNAfMet, and mammalian tRNAfMet at the same two positions in the anticodon loop . In contrast, S1 nuclease cleaved the anticodon loop of E . coli tRNAmMet, yeast tRNAmMet, yeast tRNAPhe, Schizosaccharomyces pombe tRNAPhe, E . coli tRNA2Glu, and E . coli tRNATrp (su+) at four positions generally, except where a modified nucleotide in the wobble position inhibited the enzyme . The marked contrast between these cleavage patterns suggests a different conformation for the anticodon loops of these two classes of tRNA molecules . It is suggested that the specialized conformation in the anticodon loop of initiator tRNAs may be due to a special sequence of GC base pairs in the adjoining anticodon stem. Nucleic Acids Res, 1979 Jun 25, 6(8), 2683 - 95 The nucleotide sequence of a UGA suppressor serine tRNA from Schizosaccharomyces pombe; Rafalski A et al.; The UGA suppressor tRNA produced by Schizosaccharomyces pombe strain sup3-e was purified to homogeneity . It can be aminoacylated with a serine by a crude aminoacyl-tRNA synthetase preparation from S . pombe cells . By combining post-labeling fingerprinting and gel sequencing methods the nucleotide sequence of this tRNA was determined to be: pG-U-C-A-C-U-A-U-G-U-C-ac4C-G-A-G-D-G-G-D-D-A-A-G-G-A-m2G2-psi-U-A-G-A-N-U-U-C-A-i6A-A-psi-C-U-A-A-U-G-G-G-C-U-U-U-G-C-C-C-G-m5C-G-G-C-A-G-G-T-psi-C-A-m1A-A-U-C-C-U-G-C-U-G-G-U-G-A-C-G-C-C-A OH . The anticodon sequence u ca is complementary to the UGA codon. Mol Gen Genet, 1979 May 4, 172(2), 221 - 8 Identification and nucleotide sequence of the sup8-e UGA-suppressor leucine tRNA from Schizosaccharomyces pombe; Wetzel R et al.; Using the translation of rabbit globin mRNA in wheat germ extracts as an assay for ochre and opal suppression, a UGA suppressor tRNA from Schizosaccharomyces pombre strain sup8-e was purified by column chromatography and two-dimensional gel electrophoresis . The purified tRNA can be aminoacylated with leucine by a crude aminoacyl-tRNA synthetase preparation from a wild type S . pombe strain, and has high activity in the suppressor assay . By a combination of post-labeling fingerprinting and rapid gel sequencing methods the nucleotide sequence of this suppressor tRNA was determined to be: pG-C-G-G-C-U-A-U-G-C-C-ac4C-G-A-G-D-G-G-D-G-D-A-A-G-G-G-m22G-G-C-A-G-A-psi-U-U*-C-A-m1G-C-C-C-U-G-C-U-G-U-U-G-U-A-A-A-A-C-G-m5C-G-A-G-A-G-T-psi-C-G-m1A-A-C-C-U-C-U-C-U-G-G-C-C-G-C-A-C-C-AOH . The anticodon sequence U*CA is complementary to the UGA codon . An interesting feature of the suppressor tRNA is an expanded anticodon loop of nine nucleotides owing to an A-C nonpair at the first anticodon stem position. Mol Gen Genet, 1979 May 4, 172(2), 165 - 9 2 micrometer covalently closed non-mitochondrial circular DNA in the petite-negative yeast Schizosaccharomyces pombe; Del Giudice L et al.; A population of small covalently closed non-mitochondrial circular DNA molecules was isolated from the petite-negative yeast Schizosaccharomyces pombe . The mean length of these molecules, possessing the same density as nuclear DNA (1.695 g/cm3) is 1.95 +/- 0.18 micrometer . The presence of these minicircles in crude mitochondrial preparations indicates their tight association with mitochondrial particles . Their disappearance after DNase treatment of mitochondria demonstrates their extramitochondrial location. J Cell Sci, 1979 Apr, 36, 155 - 68 A control acting over the initiation of DNA replication in the yeast Schizosaccharomyces pombe; Nasmyth KA; The control of cell division in the yeast Schizosaccharomyces pombe appears to be quite different to that of any other eukaryotic organisms for it is usually exerted not at the initiation of S-phase but at that of mitosis . However, it has been suggested that a control over the initiation of S-phase does also exist but that its action is redundant whilst the mitotic control is operating . This study has chosen conditions in which the latter appears to be largely absent in order to study the cryptic S-phase control . The timing of S-phase has been studied in cells grown at varying rates under nitrogen limitation in a chemostat . It is found that under these conditions the control of cell division resembles that of other eukaryotes . As the dilution rate of the chemostat is reduced, all increase in the generation time can be accounted for by a lengthened G1 period . In contrast, the length of S + G2 remains invariant . Thus, there must indeed be a control acting in G1 in S . pombe . An analysis of the size of cells at different growth rates shows that the initiation of S-phase is correlated with a particular cell size. J Biol Chem, 1979 Mar 10, 254(5), 1546 - 51 Characterization of a UGA-suppressing serine tRNA from Schizosaccharomyces pombe with the help of a new in vitro assay system for eukaryotic suppressor tRNAs; Kohli J et al.; Two different allele-specific suppressor mutants of the fission yeast Schizosaccharomyces pombe produce opal (UGA) suppressor tRNAs . This was shown by the use of a new in vitro assay for eukaryotic nonsense suppression: a wheat germ extract is programmed with rabbit globin mRNAs and the readthrough products are studied . alpha-Globin is elongated upon addition of ochre (UAA) suppressor tRNAs, whereas beta-globin yields a readthrough product with opal suppressor tRNAs . This simple and very sensitive assay allowed the purification of the opal suppressor tRNA from S . pombe strain sup3-e . The pure tRNA can be aminoacylated with serine; thus, we conclude that this suppressor tRNA inserts serine in response to the UGA termination codon of pure rabbit beta-globin mRNA. J Cell Sci, 1979 Feb, 35, 41 - 51 Analysis of the significance of a periodic, cell size-controlled doubling in rates of macromolecular synthesis for the control of balanced exponential growth of fission yeast cells; Barnes A et al.; Mutant strains of the fission yeast Schizosaccharomyces pombe are available which divide at smaller mean sizes than wild type . Earlier work by the present authors has shown that all these strains double their rates of polyadenylated messenger RNA synthesis as a step once in each cell cycle . The smaller the cell, the later in the cycle is the doubling in rate of synthesis . Strains of all sizes, however, double their synthetic rate when at the same threshold size . We show here that the differences in cell cycle stage of doubling in rate of polyadenylated messenger RNA synthesis are enough to explain the reduced mean steady state polyadenylated messenger RNA contents of the smaller strains . The cell size-related control over doubling in rate of synthesis is also shown to maintain the mean polyadenylated messenger RNA content as a constant proportion of cell mass, irrespective of cell size . This control thus allows cells to maintain balanced exponential growth, even when absolute growth rate per cell is altered by mutation