J Biol Chem, 1987 Dec 25, 262(36), 17549 - 55 Mutation of a conserved glycine residue modifies the vanadate sensitivity of the plasma membrane H+-ATPase from Schizosaccharomyces pombe; Ghislain M et al.; The structural gene pma+1 for the H+-ATPase from the fission yeast Schizosaccharomyces pombe has been isolated and sequenced . The intron-less gene encodes for a protein of Mr = 99,769 which is 75% homologous to those of Saccharomyces cerevisiae and Neurospora crassa . The S . pombe pma+1 gene complements not only S . pombe pma-1-1 but also S . cerevisiae pma-1-4 mutants selected for in vitro vanadate-resistant ATPase activity . The sequence of the S . pombe mutant pma-1-1 allele reveals that the glycine residue 268, which is perfectly conserved in the transduction domain of all animal and fungal transport ATPases sequenced so far, is modified into an aspartate residue by the mutation . Replacement of glycine 268 by aspartate has been monitored by the appearance of a new PvuI restriction site in the mutant DNA . Mitotic cosegregation has been observed between the PvuI site and vanadate-resistant ATPase activity in a growing population of S . pombe transformants. Philos Trans R Soc Lond B Biol Sci, 1987 Dec 15, 317(1187), 507 - 16 Control over the onset of DNA synthesis in fission yeast; Simanis V et al.; The fission yeast Schizosaccharomyces pombe has been used to identify gene functions required for the cell to become committed to the mitotic cell cycle and to initiate the processes leading to chromosome replication in S-phase . Two gene functions cdc2 and cdc10 must be executed for the cell to traverse 'start' and proceed from G1 into S-phase . Before the completion of these two functions the cell is in an uncommitted state and can undergo alternative developmental fates such as conjugation . A third gene, suc1, has also been identified whose product may interact directly with that of cdc2 at 'start' . The molecular functions of the genes involved in the completion of 'start' have been investigated . The cdc2 gene has been shown to be a protein kinase, suggesting that phosphorylation may be involved in the control over the transition from G1 into S-phase . The biochemical functions of the cdc10 and suc1 gene products have not yet been elucidated . A control at 'start' has also been shown to exist in the budding yeast Saccharomyces cerevisiae . Traverse of 'start' requires the execution of the CDC28 gene function . The cdc2 and CDC28 gene products (lower-case letters represent genes of Schizosaccharomyces pombe, and capital letters genes of Saccharomyces cerevisiae) are functionally homologous, suggesting that the processes involved in traverse of 'start' are highly conserved . An analogous control may also exist in the G1 period of mammalian cells, suggesting that the 'start' control step, after which cells become committed to the mitotic cell cycle, may have been conserved through evolution. Eur J Biochem, 1987 Dec 15, 169(3), 527 - 37 The mitochondrial genome of the fission yeast, Schizosaccharomyces pombe . Sequence of the large-subunit ribosomal RNA gene, comparison of potential secondary structure in fungal mitochondrial large-subunit rRNAs and evolutionary considerations; Lang BF et al.; The DNA sequence of the mitochondrial large subunit (LSU) rRNA gene of Schizosaccharomyces pombe has been determined . In the direction of transcription, this gene is located between the gene coding for subunit II of cytochrome oxidase and a cluster of three tRNA genes . Both the 5' and 3' ends of the LSU rRNA have been mapped precisely: whereas the 5' end can be assigned unambiguously to a single nucleotide position, multiple 3' ends occur within a run of eight U residues . Based on these results, the S . pombe LSU rRNA is between 2818 and 2826 nucleotides long . A sequence motif immediately upstream of the 5' end of the gene resembles that of the mitochondrial promoter motif of Saccharomyces cerevisiae; however, the sequence at the 3' end of the gene is not similar to any of the motifs implicated as processing signals in other mitochondrial systems . Unlike its counterparts in S . cerevisiae and Aspergillus nidulans, the mitochondrial LSU rRNA gene of S . pombe does not contain an intron . Comparison of potential secondary structure among the three fungal mitochondrial and Escherichia coli LSU rRNAs has defined a common secondary structure core, held together by long-range hydrogen-bonding interactions . A 5.8S-like structure is present within the 5'-terminal region of all three fungal mitochondrial LSU rRNAs; in contrast, no 4.5S-like structure is evident at the 3' end of these molecules . An evolutionary evaluation of highly conserved regions of a small set of LSU rRNA sequences suggests that S . pombe mitochondria diverged from a mitochondrial proto-fungal branch earlier than either A . nidulans or S . cerevisiae mitochondria . This result, considered in conjunction with the patterns of genome organization and codon usage in fungal mitochondria, points to a slower evolutionary clock speed in the mitochondrial genome of S . pombe. Nucleic Acids Res, 1987 Dec 10, 15(23), 9727 - 39 Cloning and sequencing of Schizosaccharomyces pombe DNA topoisomerase I gene, and effect of gene disruption; Uemura T et al.; We cloned the structural gene topl+ for Schizosaccharomyces pombe DNA topoisomerase I (topo I) by hybridization . An eight-fold increase of topo I relaxing activity was obtained in S . pombe cells transformed with multicopy plasmid with topl+ insert . Nucleotide sequence determination showed a hypothetical coding frame interrupted by two short introns, encoding a 812 residue polypeptide (M.W . 94,000), 43 residues longer than and 47% homologous to Saccharomyces cerevisiae topo I . We show that the topl (null) strain made by gene disruption is viable, although its generation time is 20% longer than that of wild type . The topl locus is mapped in the long arm of chromosome II, using the Leu+ marker integrated with the cloned topl+ sequence . We constructed a double mutant topl (null) top2 (ts) and found its defective phenotype similar to that of previously obtained topl (heat sensitive) top2 (ts) . The other double mutant topl (null) top2 (cs), however, was lethal . Our results suggest that topl+ gene of S . pombe is dispensable only if topo II activity is abundant. Mol Gen Genet, 1987 Dec, 210(3), 485 - 9 Strains of Schizosaccharomyces pombe with a disrupted swi1 gene still show some mating-type switching; Schmidt H; The swi1+ gene is necessary for effective mating-type (MT) switching in Schizosaccharomyces pombe . It was cloned on a 4.2 kb genomic DNA fragment . By site-directed integration into the genome and gene disruption experiments it was proved that the swi1+ gene itself and not a suppressor had been isolated . Disruption of the swi1+ gene causes a phenotype identical to that of the original swi1 mutant, i.e . the strain still shows some MT switching . The swi1 gene is unique in the genome and gives rise to a 3 kb mRNA. Mol Cell Biol, 1987 Dec, 7(12), 4424 - 30 Identification of healed terminal DNA fragments in linear minichromosomes of Schizosaccharomyces pombe; Matsumoto T et al.; The minichromosome Ch16 of the fission yeast Schizosaccharomyces pombe is derived from the centromeric region of chromosome III . We show that Ch16 and a shorter derivative, Ch12, made by gamma-ray cleavage, are linear molecules of 530 and 280 kilobases, respectively . Each minichromosome has two novel telomeres, as shown by genomic Southern hybridization with an S . pombe telomere probe . Comparison by hybridization of the minichromosomes and their chromosomal counterparts showed no signs of gross rearrangement . Cosmid clones covering the ends of the long arms of Ch16 and Ch12 were isolated, and subcloned fragments that contained the breakage sites were identified . They are apparently unique in the genome . By hybridization and Bal 31 digestion, the ends appear to consist of the broken-end sequences directly associated with short stretches (about 300 base pairs) of new DNA that hybridizes to a cloned S . pombe telomere . They do not contain the telomere-adjacent repeated sequences that are present in the normal chromosomes . The sizes of the short telomeric stretches are roughly the same as those of the normal chromosomes . Our results show that broken chromosomal ends in S . pombe can be healed by the de novo addition of the short telomeric repeats . The formation of Ch16 must have required two breakage-healing events, whereas a single cleavage-healing event in the long arm of Ch16 yielded Ch12. Biochem Biophys Res Commun, 1987 Nov 13, 148(3), 1182 - 8 Revertant of the yeast Schizosaccharomyces pombe with modified alpha subunits of mitochondrial ATPase-ATPsynthase: impaired nucleotide interactions with soluble and membrane-bound enzyme; Falson P et al.; A partial revertant from a mutant with modified alpha subunits of mitochondrial ATPase-ATPsynthase has been obtained for the first time from the yeast Schizosaccharomyces pombe . The purified F1 contains a lower amount of endogenous nucleotides as compared to the wild-strain enzyme . In contrast to the wild-type, the F1 ATPase activity from the revertant does not exhibit bicarbonate-sensitive negative cooperativity . The revertant Michaelis constant for Mg-ATP is very similar to that of normal F1 in the presence of bicarbonate while the Vm is slightly lower . The revertant enzyme is much less sensitive to inhibitions by ADP and by azide . It is proposed that the lack of negative cooperativity of revertant F1 ATPase activity is due to lower affinity for ADP, the release of which is no longer the rate-limiting step. Nature, 1987 Oct 15-21, 329(6140), 651 - 4 Similarity between cell-cycle genes of budding yeast and fission yeast and the Notch gene of Drosophila; Breeden L et al.; The HO gene of Saccharomyces cerevisiae encodes the endonuclease that initiates mating-type switching . To prevent inopportune switching, HO transcription is restricted to a specific period in the haploid cell cycle, which is just after, and dependent on, the start of the mitotic cell cycle . A repeated promoter element (CACGA4) (refs 7-9) and two trans-acting activators (SWI4 and SWI6) have been identified, which are responsible for the periodic and start-dependent transcription of HO . To understand further the link between start and HO transcription, the SWI6 gene has been cloned and sequenced . The SWI6 protein is similar to the protein in Schizosaccharomyces pombe that is encoded by cdc10 an essential gene specifically required at the start of the cell cycle . The similarity between the SWI6 and cdc10 products, and their common involvement with 'start', suggest that they may share a common mechanism for sensing or executing this critical control step in the cell cycle . The SWI6 and cdc10 proteins also contain two copies of a repeated motif that occurs at least five times in the cytoplasmic domain of the Notch protein of Drosophila melanogaster. Nucleic Acids Res, 1987 Oct 12, 15(19), 7865 - 76 Resolution of DNA molecules greater than 5 megabases by contour-clamped homogeneous electric fields; Vollrath D et al.; Excellent resolution of chromosomal DNA molecules from Saccharomyces cerevisiae, Candida albicans and Schizosaccharomyces pombe has been obtained using alternating contour-clamped homogeneous electric field (CHEF) gel electrophoresis . The largest of these molecules is greater than 5 Mb in size and is resolved after 130 hours in a 0.6% agarose gel at a field strength of 1.3 V/cm and a switching interval of 1 hour . Separation of concatamers of phage lambda DNA reveals four regions of resolution in alternating CHEF gel electrophoresis . There are two regions of good resolution in which mobility approximates a linear function of molecular weight . These are separated by a region of lower resolution and bounded at high molecular weights by a region of little or no resolution . The four regions are of practical and possibly theoretical importance. J Mol Biol, 1987 Oct 5, 197(3), 389 - 95 Nucleotide sequences of three tRNA(Ser) from Drosophila melanogaster reading the six serine codons; Cribbs DL et al.; The nucleotide sequences of three serine tRNAs from Drosophila melanogaster, together capable of decoding the six serine codons, were determined . tRNA(Ser)2b has the anticodon GCU, tRNA(Ser)4 has CGA and tRNA(Ser)7 has IGA . tRNA(Ser)2b differs from the last two by about 25% . However, tRNA(Ser)4 and tRNA(Ser)7 are 96% homologous, differing only at the first position of the anticodon and two other sites . This unusual sequence relationship suggests, together with similar pairs in the yeasts Schizosaccharomyces pombe and Saccharomyces cerevisiae, that eukaryotic tRNA(Ser)UCN may be undergoing concerted evolution. Mol Gen Genet, 1987 Oct, 209(3), 627 - 9 Mapping of the ras1 gene of Schizosaccharomyces pombe; Lund PM et al.; The ras1 gene, an oncogene homologue, is known to be essential for recognition of the mating pheromone and hence for conjugation but not for vegetative growth in Schizosaccharomyces pombe . To facilitate further characterization and genetic manipulation of this gene, we have mapped it by using S . pombe strains which carry the Saccharomyces cerevisiae LEU2 gene inserted next to ras1 on the chromosome . Crosses with tester strains revealed that ras1 is tightly linked to pro2 on chromosome I . Furthermore, we have shown that ras1 is allelic with ste5, one of the sterility genes described by O . Girgsdies . The map position previously reported for ste5 eventually turned out to be false. J Cell Sci, 1987 Oct, 88 ( Pt 3), 295 - 304 Schizosaccharomyces pombe mutants affected in their division response to starvation; Young PG et al.; Schizosaccharomyces pombe mutants have been selected on the basis of an altered response to nutritional stimulation of cell division (changed division response, cdr) . Two new loci (cdr1 and cdr2) were identified and characterized . When suspended in nitrogen-free medium wild-type cells underwent stimulated rates of division and became reduced to approximately 30% in protein content with a concomitant 3.6-fold increase in cell number after 24 h starvation . cdr cells had significantly smaller increases in cell number . The ratio of starved/unstarved protein content was higher for the cdr strains than for the wild type . cdr cells were also affected in their response to nitrogen-source shifts from proline to glutamate (or vice versa) or when shifted from serine phosphate to inorganic phosphate, showing that the alteration in division response was not restricted to nitrogen metabolism . Upon nitrogen starvation wild-type cells arrested prior to the cdc10 execution point, whereas cdr cells arrested later in the cell cycle . cdc25-22 cdr1 or cdr2 double mutants grew very slowly and were extremely elongated at all temperatures; the restrictive temperature was reduced to 27 degrees C . wee1 was epistatic to cdr mutations with respect to cell length at the cell plate stage . cdr+ genes are postulated to play a role in the nutritional modulation of the mitotic size control. Nucleic Acids Res, 1987 Sep 25, 15(18), 7369 - 79 A single intronless action gene in the fission yeast Schizosaccharomyces pombe: nucleotide sequence and transcripts formed in homologous and heterologous yeast; Mertins P et al.; The actin gene of the fission yeast Schizosaccharomyces pombe has been isolated by using as a hybridization probe cloned actin DNA from the budding yeast Saccharomyces cerevisiae . In contrast to most actin genes studied from diverse eukaryotic species, the S . pombe gene is not interrupted by introns . The protein sequence deduced from the nucleotide sequence of the gene shows that the S . pombe actin is more closely related to the mammalian gamma-actin than to the actin of S . cerevisiae . Three transcripts of 1240, 1650 and 1850 nucleotides having the same 5' end but differing in the length of their 3' untranslated region are generated in the fission yeast . Only one messenger RNA of 1330 nucleotides is formed from the S . pombe actin gene in S . cerevisiae . Contrary to the observation made with other S . pombe genes transcribed in the budding yeast, the heterologous actin gene transcript is initiated 39 nucleotides upstream of the initiation start site used in the homologous yeast . The mRNA termination (or 3' processing) mechanism in the two ascomycetes also differs as the 3'end of the S . pombe actin gene transcript in S . cerevisiae does not coincide with either of the three 3'ends mapped in the fission yeast. Cell, 1987 Sep 11, 50(6), 917 - 25 DNA topoisomerase II is required for condensation and separation of mitotic chromosomes in S . pombe; Uemura T et al.; We show that DNA topoisomerase II (topo II) is continuously required for mitotic chromosome changes in Schizosaccharomyces pombe . We constructed cold-sensitive (cs) or temperature-sensitive (ts) strains mutated in the genes coding for topo II (top2) and beta-tubulin (nda3) . The ATP-dependent activity of the top2cs gene product is cs in vitro . The cloned top2cs gene sequence predicts an amino acid substitution . A cs top2-cs nda3 double mutant at 20 degrees C shows long, entangled chromosomes, which condense and separate upon the shift to permissive temperatures . If spindle formation is prevented at permissive temperatures, the chromosomes condense but do not separate . Thus topo II is required for final chromosome condensation; moreover, pulse-shift experiments show that topo II is required for chromatid disjuction . Experiments with ts top2-cs nda3 cells show that topo II is also required for chromosome separation in anaphase: inactivation of topo II and activation of beta-tubulin allow normal spindle formation but result in "streaked" chromosomes. FEBS Lett, 1987 Aug 10, 220(1), 27 - 30 Heterogeneous glycosylation of the EXG1 gene product accounts for the two extracellular exo-beta-glucanases of Saccharomyces cerevisiae; Nebreda AR et al.; Two exo-beta-glucanases of glycoprotein nature can be detected in culture supernatants of Saccharomyces cerevisiae cells . These exo-beta-glucanases show different Mr values and kinetic properties, although they are immunologically related . Their carbohydrate content and the electrophoretic mobility of both endoglycosidase H-treated exo-beta-glucanases suggest that they share the same protein fraction . Studies at genetic level relate the production of both extracellular exo-beta-glucanases with the expression of a single-copy gene in S . cerevisiae . Expression of this gene in another yeast, Schizosaccharomyces pombe, demonstrates that it codes for a protein with exo-beta-glucanase activity whose heterogeneous N-glycosylation accounts for both extracellular exo-beta-glucanases of S . cerevisiae. Cell, 1987 Jul 31, 50(3), 391 - 403 A fission yeast chromosome can replicate autonomously in mouse cells; Allshire RC et al.; To test the functional capacity of a fission yeast chromosome in mouse cells, a strain of the fission yeast Schizosaccharomyces pombe, ED628 Int5, was constructed . A plasmid bearing the SV2NEO gene, which can confer G418 resistance to mouse cells, was integrated at the ura4 locus on S . pombe chromosome III . S . pombe Int5 chromosomes were introduced into mouse C127 cells by PEG-facilitated protoplast fusion . Here we describe two independent G418-resistant cell lines with distinct growth characteristics, F1.1 and F7.1, and examine the structure of material derived from S . pombe Int5 chromosome III in these lines . F1.1 is shown to contain a single rearranged block of chromatin from S . pombe chromosome III integrated into a mouse chromosome, maintained in the absence of selection . In contrast, the data for F7.1 are consistent with the presence of linear, unintegrated copies of S . pombe chromosome III, which are apparently intact and maintained in an unstable but autonomous state . The unstable maintenance of this chromosome may be due to defective centromere function leading to missegregation at mitosis or to over- or underreplication. J Mol Biol, 1987 Jul 20, 196(2), 355 - 61 High level of complexity of small nuclear RNAs in fungi and plants; Tollervey D; The complexity of the trimethylguanosine-capped, small nuclear RNA (snRNA) populations in a number of organisms has been examined using immunoprecipitation and two-dimensional gels . From the fungi Aspergillus nidulans and Schizosaccharomyces pombe, over 30 major snRNAs can be resolved . The most abundant of these correspond to the putative analogues of vertebrate U1, U2, U4 and U5, which have been reported to be precipitated by anti-Sm antibodies, but other snRNAs are little less abundant than the major Sm-precipitable species . A similarly high level of complexity of snRNAs is detected in pea plants . In Candida albicans, the snRNAs are somewhat less numerous (about 22 major species) and are substantially less abundant than those of the above fungi, features shared with another budding yeast, Saccharomyces cerevisiae . Ten species of human snRNA have been reported; on two-dimensional gels, a number of additional snRNAs can be resolved from human cells . Each fungus, as well as pea plants, contains snRNAs substantially larger than any reported from vertebrates or detected in the human RNA used here . It appears that many eukaryotes contain substantially more species of snRNA than was previously believed. Cell, 1987 Jul 17, 50(2), 319 - 25 Identification of p34 and p13, human homologs of the cell cycle regulators of fission yeast encoded by cdc2+ and suc1+; Draetta G et al.; cdc2+ and CDC28 play central roles in the cell division cycles of the widely divergent yeasts Schizosaccharomyces pombe and Saccharomyces cerevisiae, respectively . The genes encode protein kinases that show 62% protein sequence identity and are capable of cross-complementation . Monoclonal antibodies were raised against p34cdc2, and a subset recognize p36cdc28 . The cross-reacting antibodies detected a 34 kd homolog of the p34cdc2/p36CDC28, protein in HeLa cells . Human p34 was also recognized by an affinity-purified polyclonal anti-p34cdc2 serum . Peptide mapping of p34cdc2, p36CDC28, and human p34 revealed complete conservation of four tryptophan residues in the three proteins . p34 thus appears to be closely related to the two yeast proteins . In addition, a p34 immune complex showed protein kinase activity in vitro, and HeLa cell p34 interacts with p13, the human homolog of the suc1+ gene product of S . pombe. Nucleic Acids Res, 1987 Jun 25, 15(12), 4705 - 15 A novel sequence common to the centromere regions of Schizosaccharomyces pombe chromosomes; Nakaseko Y et al.; An approximately 4 kb long sequence (designated dh) is located in the centromere regions of all three chromosomes of S . pombe . There is one copy each of dh per centromere in chromosomes I and II and multiples in the centromere of chromosome III . Nucleotide sequence determination shows that dhI and dhII are highly homologous . A part of the sequence (ca . 300-400 bp) contains short direct repeats, otherwise dh is in general internally non-repetitious . Although there are three segmental deletions (total 821 bp) and two insertions (27 bp) in dhII (an 80% overall homology to dhI), there are only nine substitutions between dhI and dhII in the remaining 3980 bp, giving a 99.77% homology . The substitutions are restricted to the non-repetitious domains and are only of the pyrimidine-pyrimidine or purine-purine types . A possible conformational role of dh is discussed. Nucleic Acids Res, 1987 Jun 11, 15(11), 4481 - 9 An electrophoretic karyotype for Schizosaccharomyces pombe by pulsed field gel electrophoresis; Smith CL et al.; The three chromosomal DNAs of S . pombe have been fractionated by pulsed field gel electrophoresis . The resulting molecular karyotype will greatly speed gene mapping in this organism, and it indicates that the separation range of the technique extends to DNA molecules as large as 9,000,000 base pairs. EMBO J, 1987 Jun, 6(6), 1757 - 63 Nuclear pre-mRNA splicing in the fission yeast Schizosaccharomyces pombe strictly requires an intron-contained, conserved sequence element; Mertins P et al.; It has recently been argued that pre-mRNA splicing in the fission yeast Schizosaccharomyces pombe may be more similar to splicing in metazoan species than in the budding yeast Saccharomyces cerevisiae . In this report we show that, contrary to this assumption, the conserved sequence element 5'-CTPu APy-3' found in all S . pombe introns 6-18 nucleotides upstream of the 3' splice site is, like the TACTAAC box in S . cerevisiae, indispensable for efficient splicing . The conserved adenine residue of this sequence is used for branch formation and point mutations introduced into the CTPuAPy sequence abolish splicing and seem not to result in the recruitment of cryptic branch sites . We also show that an S . cerevisiae intron is correctly excised in S . pombe whereby the TACTAAC box is used in branch formation. Proc Natl Acad Sci U S A, 1987 Jun, 84(11), 3580 - 4 Analysis and in vivo disruption of the gene coding for calmodulin in Schizosaccharomyces pombe; Takeda T et al.; Calmodulin is a low molecular weight calcium-binding protein that modulates many enzyme systems in eukaryotes . We have cloned the gene encoding calmodulin from the fission yeast, Schizosaccharomyces pombe, by using synthetic oligonucleotide probes that correspond to three distinct regions of Tetrahymena calmodulin . A 1.6-kilobase (kb) DNA fragment that hybridized to all of them contains a gene whose deduced product possesses 74% amino acid homology with bovine calmodulin . This gene, which is unique in the S . pombe genome and is named cam1, encodes 149 amino acids excluding the first methionine and is transcribed into mRNA of 1.2-kb length . It has an intron that apparently starts immediately after the initiation codon and is 126 bp long . S . pombe calmodulin exhibits more homology to vertebrate calmodulin than to that of the budding yeast, Saccharomyces cerevisiae . Gene disruption experiments revealed that cam1 gene function is essential for vegetative growth of S . pombe . Spores bearing disrupted cam1 halt growth soon after germination and rarely carry out the first cell division, indicating that calmodulin does not exist in excess in those cells. Proc Natl Acad Sci U S A, 1987 May, 84(9), 2585 - 9 Cloning and heterologous expression of glycosidase genes from Saccharomyces cerevisiae; Kuranda MJ et al.; Genomic clones were isolated that code for three glycosidases proposed to be involved in the catabolism of cell wall components in Saccharomyces cerevisiae . alpha-Mannosidase (AMS1), exoglucanase (BGL1), and endochitinase (CTS1) genes were isolated with the aid of filter assays based on the hydrolysis of 4-methylumbelliferyl glycosides, which permitted the in situ monitoring of these glycosidase activities in yeast colonies . Uracil prototrophs resulting from transformation with a multicopy YEp24 yeast genomic library were screened, leading to the identification of transformants possessing high levels of glycosidase activity . Restriction maps of plasmids from multiple isolates were used to localize glycosidase-overproduction genes, which were subcloned into a Schizosaccharomyces pombe/S . cerevisiae shuttle vector . Transformation of Sch . pombe with BGL1 and CTS1 subclones resulted in the appearance of these activities in this organism, and an AMS1 plasmid caused a 2-fold increase in endogenous alpha-mannosidase levels . Insertion of the marker gene LEU2 into putative AMS1 sequences disrupted plasmid-encoded alpha-mannosidase overproduction . S . cerevisiae strains that incorporated a restriction fragment containing ams1::LEU2 into their chromosomal DNA by homologous recombination expressed no detectable alpha-mannosidase activity in either the haploid or homozygous recessive diploid states, whereas heterozygous and wild-type cells exhibited levels proportional to AMS1 gene dosage . No readily apparent phenotype was associated with the alpha-mannosidase deficiency; however, labeling experiments utilizing {2-3H}mannose suggest that alpha-mannosidase may function in mannan turnover. Mol Gen Genet, 1987 Apr, 207(1), 161 - 4 Characterisation of an autonomously replicating sequence from the fission yeast Schizosaccharomyces pombe; Johnston LH et al.; A DNA sequence has been isolated from Schizosaccharomyces pombe which promotes high frequency transformation of plasmids in the same organism . It is closely linked to the DNA ligase gene CDC17 and has therefore been named ARS17 although in structure it differs substantially from ARS elements in Saccharomyces cerevisiae . ARS17 spans some 1.8 kb of DNA and deletion of any part of this region affects activity . Moreover, there does not appear to be any short sequence which is, by itself, sufficient for high frequency transformation . ARS17 lies between and partly overlaps two divergently transcribed genes and it is extremely AT rich . It lacks the consensus sequence found in S . cerevisiae ARSs and it has no ARS activity in S . cerevisiae. Microbiol Sci, 1987 Apr, 4(4), 115 - 8 Yeast tubulin genes; Yanagida M; There are two alpha-tubulin genes and one beta-tubulin gene in Schizosaccharomyces pombe and Saccharomyces cerevisiae . Detailed analyses employing tubulin mutants and cloned genes have revealed different cellular roles for the tubulin genes in these organisms. J Biol Chem, 1987 Mar 15, 262(8), 3754 - 61 Kinetic characterization of yeast alcohol dehydrogenases . Amino acid residue 294 and substrate specificity; Ganzhorn AJ et al.; A three-dimensional model of yeast alcohol dehydrogenase, based on the homologous horse liver enzyme, was used to compare the substrate binding pockets of the three isozymes (I, II, and III) from Saccharomyces cerevisiae and the enzyme from Schizosaccharomyces pombe . Isozyme I and the S . pombe enzyme have methionine at position 294 (numbered as in the liver enzyme, corresponding to 270 in yeast), whereas isozymes II and III have leucine . Otherwise the active sites of the S . cerevisiae enzymes are the same . All four wild-type enzymes were produced from the cloned genes . In addition, oligonucleotide-directed mutagenesis was used to change Met-294 in alcohol dehydrogenase I to leucine . The mechanisms for all five enzymes were predominantly ordered with ethanol (but partially random with butanol) at pH 7.3 and 30 degrees C . The wild-type alcohol dehydrogenases and the leucine mutant had similar kinetic constants, except that isozyme II had 10-20-fold smaller Michaelis and inhibition constants for ethanol . Thus, residue 294 is not responsible for this difference . Apparently, substitutions outside of the substrate binding pocket indirectly affect the interactions of the alcohol dehydrogenases with ethanol . Nevertheless, the substitution of methionine with leucine in the substrate binding site of alcohol dehydrogenase I produced a 7-10-fold increase in reactivity (V/Km) with butanol, pentanol, and hexanol . The higher activity is due to tighter binding of the longer chain alcohols and to more rapid hydrogen transfer. J Biol Chem, 1987 Mar 5, 262(7), 3146 - 53 Study of the nucleotide binding site of the yeast Schizosaccharomyces pombe plasma membrane H+-ATPase using formycin triphosphate-terbium complex; Ronjat M et al.; The plasma membrane of yeasts contains an H+-ATPase similar to the other cation transport ATPases of eukaryotic organisms . This enzyme has been purified and shows H+ transport in reconstituted vesicles . In the presence of Mg2+, formycin triphosphate (FTP) is hydrolyzed by the H+-ATPase and supports H+ transport . When combined with terbium ion, FTP (Tb-FTP) and ATP (Tb-ATP) are no longer hydrolyzed . Competition between Mg-ATP and Tb-FTP for ATP hydrolysis indicates that terbium-associated nucleotides bind to the catalytic site of the H+-ATPase . The fluorescent properties of the Tb-FTP complex were used to study the active site of the H+-ATPase . Fluorescence of Tb-FTP is greatly enhanced upon binding into the nucleotide site of H+-ATPase with a dissociation constant of 1 microM . Tb-ATP, Tb-ADP, and Tb-ITP are competitive inhibitors of Tb-FTP binding with Ki = 4.5, 5.0, and 6.0 microM, respectively . Binding of Tb-FTP is observed only in the presence of an excess of Tb3+ with an activation constant Ka = 25 microM for Tb3+ . Analysis of the data reveals that the sites for Tb-FTP and Tb3+ binding are independent entities . In standard conditions these sites would be occupied by Mg-ATP and Mg2+, respectively . These findings suggest an important regulatory role of divalent cations on the activity of H+-ATPase . Replacement of H2O by D2O in the medium suggests the existence of two types of nucleotide binding sites differing by the hydration state of the Tb3+ ion in the bound Tb-FTP complex. J Cell Sci, 1987 Mar, 87 ( Pt 2), 323 - 5 Periodic cell cycle changes in the rate of CO2 production in the fission yeast Schizosaccharomyces pombe persist after a block to protein synthesis; Novak B et al.; CO2 production has been followed by manometry in synchronous and asynchronous control cultures of Schizosaccharomyces pombe prepared by elutriation from the same initial culture . Earlier results showed a periodic change in the rate of production, which took place once per cell cycle . These changes were most clearly shown as oscillations in the difference between values of the second differential (acceleration) for the synchronous and asynchronous cultures . This paper shows that the oscillations continue for at least three cycles in the presence of cycloheximide (with and without chloramphenicol) . Protein synthesis is virtually absent and there is no cell division . The control of this metabolic oscillation is therefore not directly dependent on translation . The period of the oscillation under these conditions is about 60% of the normal cycle time. Nature, 1987 Mar 26-Apr 1, 326(6111), 414 - 6 Need for DNA topoisomerase activity as a swivel for DNA replication for transcription of ribosomal RNA; Brill SJ et al.; Yeast strains with mutations in the genes for DNA topoisomerases I and II have been identified previously in both Saccharomyces cerevisiae and Schizosaccharomyces pombe . The topoisomerase II mutants (top2) are conditional-lethal temperature-sensitive (ts) mutants . They are defective in the termination of DNA replication and the segregation of daughter chromosomes, but otherwise appear to replicate and transcribe DNA normally . Topoisomerase I mutants (top1), including strains with null mutations are viable and exhibit no obvious growth defects, demonstrating that DNA topoisomerase I is not essential for viability in yeast . In contrast to the single mutants, top1 top2 ts double mutants from both Schizosaccharomyces pombe and Saccharomyces cerevisiae grow poorly at the permissive temperature and stop growth rapidly at the non-permissive temperature . Here we report that DNA and ribosomal RNA synthesis are drastically inhibited in an S . cerevisiae top1 top2 ts double mutant at the restrictive temperature, but that the rate of poly(A)+ RNA synthesis is reduced only about threefold and transfer DNA synthesis remains relatively normal . The results suggest that DNA replication and at least ribosomal RNA synthesis require an active topoisomerase, presumably to act as a swivel to relieve torsional stress, and that either topoisomerase can perform the required function (except in termination of DNA replication where topoisomerase II is required). Nucleic Acids Res, 1987 Feb 25, 15(4), 1477 - 92 Sequence and regulatory responses of a ribosomal protein gene from the fission yeast Schizosaccharomyces pombe; Nischt R et al.; We have determined the nucleotide sequence and mapped the 5' and 3' termini of a ribosomal protein gene . The gene is transcribed into a RNA molecule of about 770 nt and appears to initiate at multiple sites, as judged by SI nuclease analysis . Gene dosage experiments with a plasmid born gene leads to a proportional increase of the messenger RNA, but not to an overproduction of the protein, suggesting a posttranscriptional control mechanism . However, the heat shock response of this gene indicates that there is also a potential for transcriptional control . Comparison of the 5' flanking region of this gene with the ribosomal protein gene S 6 from Schizosaccharomyces pombe and with ribosomal protein genes from Saccharomyces cerevisiae revealed homologous sequences, which may be involved in the regulation of ribosomal protein genes. FEBS Lett, 1987 Feb 23, 212(2), 323 - 7 Pi in equilibrium ATP exchange in the absence of proton gradient by the H+-ATPase from yeast plasma membranes; de Meis L et al.; Purified soluble H+-ATPase from Schizosaccharomyces pombe catalyzes a Pi in equilibrium ATP exchange in the absence of a H+ gradient . When the pH of the assay medium is raised from 5.5 to 8.0 there is a decrease of the ATPase activity and an increase of the rate of Pi in equilibrium ATP exchange . At pH 7.0 the addition of the organic solvent dimethyl sulfoxide (20%, v/v) promotes a decrease of ATPase activity and an increase of the Pi in equilibrium ATP exchange reaction . The effect of the organic solvent on the Pi in equilibrium ATP exchange is related to a decrease of the apparent Km for Pi. Eur J Biochem, 1987 Feb 2, 162(3), 659 - 67 Molecular characterisation of the DNA ligase gene, CDC17, from the fission yeast Schizosaccharomyces pombe; Barker DG et al.; We have sequenced a 4200-base-pair fragment of Schizosaccharomyces pombe DNA which encompasses the entire DNA ligase gene, CDC17 . S1 mapping has enabled us to identify two small introns (40 and 62 nucleotides) at the 5' end of the coding region of the gene and their 3' internal conserved sequences match the CTRAY consensus found in other S . pombe introns . The major transcription initiation and 3' polyadenylation sites have been mapped and are preceded by higher eukaryotic-like TATA and AATAAA sequences respectively . Furthermore, the CDC17 mRNA carries a poly(A) tail whose length (approximately 250 nucleotides) is typical of that found in higher eukaryotic mRNAs, and is in contrast to the much shorter polyadenylated sequences found for the mRNAs of the budding yeast, Saccharomyces cerevisiae . The deduced amino acid sequence of the S . pombe DNA ligase predicts a protein of 86182 daltons, and an overall 53% homology with the same enzyme from S . cerevisiae . In particular, a stretch of 24 amino acids with 100% sequence homology spans the putative ATP-binding region which is also conserved in T4 and T7 bacteriophage DNA ligases. EMBO J, 1987 Feb, 6(2), 469 - 76 Fungal small nuclear ribonucleoproteins share properties with plant and vertebrate U-snRNPs; Tollervey D et al.; snRNAs with properties closely related to those of the major vertebrate U-snRNAs are present in the fungi Aspergillus nidulans, Neurospora crassa and Schizosaccharomyces pombe . These RNAs possess a tri-methyl guanosine cap structure and a subset cross-hybridizes with human U1 and U2 clones . In the form of snRNPs, snRNAs from these fungi as well as from Saccharomyces cerevisiae and pea plants are immunoprecipitated by human and anti-Sm or anti-(U1)RNP autoimmune antibodies . On micro-injection into the cytoplasm of Xenopus oocytes, the snRNAs are packaged into ribonucleoprotein particles and migrate into the nucleus . The results demonstrate a hitherto unsuspected degree of evolutionary conservation in snRNA structure, snRNP protein structure, and sites of RNA-protein interaction within snRNPs. J Biol Chem, 1987 Jan 5, 262(1), 223 - 8 A single mutation confers vanadate resistance to the plasma membrane H+-ATPase from the yeast Schizosaccharomyces pombe; Ulaszewski S et al.; A single-gene nuclear mutant has been selected from the yeast Schizosaccharomyces pombe for growth resistance to Dio-9, a plasma membrane H+-ATPase inhibitor . From this mutant, called pma1, an ATPase activity has been purified . It contains a Mr = 100,000 major polypeptide which is phosphorylated by {gamma-32P} ATP . Proton pumping is not impaired since the isolated mutant ATPase is able, in reconstituted proteoliposomes, to quench the fluorescence of the delta pH probe 9-amino-6-chloro-2-methoxy acridine . The isolated mutant ATPase is sensitive to Dio-9 as well as to seven other plasma membrane H+-ATPase inhibitors . The mutant H+-ATPase activity tested in vitro is, however, insensitive to vanadate . Its Km for MgATP is modified and its ATPase specific activity is decreased . The pma1 mutation decreases the rate of extracellular acidification induced by glucose when cells are incubated at pH 4.5 under nongrowing conditions . During growth, the intracellular mutant pH is more acid than the wild type one . The derepression by ammonia starvation of methionine transport is decreased in the mutant . The growth rate of pma1 mutants is reduced in minimal medium compared to rich medium, especially when combined to an auxotrophic mutation . It is concluded that the H+-ATPase activity from yeast plasma membranes controls the intracellular pH as well as the derepression of amino acid, purine, and pyrimidine uptakes . The pma1 mutation modifies several transport properties of the cells including those responsible for the uptake of Dio-9 and other inhibitors (Ulaszewski, S., Coddington, A., and Goffeau, A . (1986) Curr . Genet . 10, 359-364). Mol Cell Biol, 1987 Jan, 7(1), 76 - 84 Substrate recognition and identification of splice sites by the tRNA-splicing endonuclease and ligase from Saccharomyces cerevisiae; Greer CL et al.; We have examined the substrate requirements for efficient and accurate splicing of tRNA precursors in Saccharomyces cerevisiae . The effects of Schizosaccharomyces pombe tRNASer gene mutations on the two steps in splicing, intron excision and joining of tRNA halves, were determined independently by using partially purified splicing endonuclease and tRNA ligase from S . cerevisiae . Two mutations (G14 and A46) reduced the efficiency of excision and joining in parallel, whereas two others (U47:7 and C33) produced differential effects on these two steps; U47:7 affected primarily the excision reaction, and C33 had a greater impact on ligation . These data indicate that endonuclease and ligase recognize both common and unique features of their substrates . Another two mutations (Ai26 and A37:13) induced miscutting, although with converse effects on the two splice sites . Thus, the two cutting events appear to be independent . Finally, we suggest that splice sites may be determined largely through their position relative to sites within the tRNA-like domain of the precursors . Several of these important sites were identified, and others are proposed based on the data described here. Curr Genet, 1987, 12(8), 591 - 7 Sequence of the bifunctional ade1 gene in the purine biosynthetic pathway of the fission yeast Schizosaccharomyces pombe; McKenzie R et al.; The ade1 gene of the fission yeast Schizosaccharomyces pombe encodes a bifunctional polypeptide with glycinamide ribotide synthetase (GARSase) and aminoimidazole ribotide synthetase (AIRSase) enzyme activities . These enzyme activities carry out the 2nd and 5th steps, respectively, of the purine synthetic pathway . We report the cloning of the ade1 gene on a 4.4 kb Sau3A insert in the yeast shuttle vector pWH5 . Integration of this genomic insert at or near the ade1 locus and its ability to complement, by transformation, three different types of ade1 mutants proved that it contains the ade1 chromosomal gene . Analysis of the nucleotide sequence of this insert revealed the presence of an uninterrupted open reading frame of 2,367 pb . This sequence, and the predicted 789 amino acid sequence encoded, both show a high degree of homology with the functionally equivalent ade5,7 gene sequence of Saccharomyces cerevisiae (approx . 60% overall in both cases) and Gart gene sequences of Drosophila melanogaster . The size of the ade1 RNA transcript is about 2.7 kb. Curr Genet, 1987, 12(5), 329 - 36 Distribution of mitochondrial introns in the species Schizosaccharomyces pombe and the origin of the group II intron in the gene encoding apocytochrome b; Zimmer M et al.; The mitochondrial genome size of 26 different Schizosaccharomyces pombe strains varies between 17.6 and 24.6 kilobase pairs due to the presence or absence of introns . One of these is the group II intron in the gene encoding apocytochrome b (cob: intron cobI1) . Partial DNA sequences of continuous cob genes from six strains (including strain EF1: Trinkl et al . 1985) revealed identical nucleotide sequence in the region where the group II intron is inserted in the mosaic form of the gene . In contrast, analysis of the mosaic cob gene in strain UCD-FstI revealed several base pair changes in the exon regions flanking the splice point, compared with the continuous genes and with the mosaic cob gene in strain 50 (Lang et al . 1985) . The base pair differences between the exons of the two mosaic cob genes and the identity of exons in all continuous cob genes argue in favour of the two cob introns in strains 50 and UCD-FstI as independent later acquisitions of the genes, rather than loss of the intron from a common mosaic ancestor of all strains . Other introns present in some but not all strain include two group I introns without open reading frame in the gene encoding subunit 1 of cytochrome c oxidase (cox1: introns cox1I2a and cox1I3), and two group I introns with open reading frames in the same gene (introns cox1I1 and cox1I2b). Gene, 1987, 60(2-3), 157 - 61 The RNA components of Schizosaccharomyces pombe RNase P are essential for cell viability; Cherayil B et al.; The fission yeast Schizosaccharomyces pombe contains in the haploid genome one copy of the gene (designated rrkl) for the RNA components of RNase P . Gene disruption in diploid cells of one copy of rrkl resulted in a moderate reduction of the level of cellular RNase P activity . Haploidization by meiosis demonstrated that rrkl is required for cell growth . Thus, the RNA components of S . pombe RNase P are essential in vivo . This is similar to the situation in Escherichia coli. Curr Genet, 1987, 11(8), 575 - 89 Genetic nomenclature and gene list of the fission yeast Schizosaccharomyces pombe; Kohli J; The nomenclature rules for the genetics of the fission yeast Schizosaccharomyces pombe have been fixed for the first time, after discussion among scientists working with this organism . Conventions are proposed for the naming of genes and alleles that are obtained by classical means or by reverse genetics . In addition a list has been compiled of 460 known genes of S . pombe . It includes genes defined both by classical mutation analysis and by molecular cloning . 270 genes have been assigned either to one of the three nuclear chromosomes or the mitochondrial genome. Gene, 1987, 58(1), 59 - 66 The unique histone H2A gene of Aspergillus nidulans contains three introns; May GS et al.; The histone H2A gene of the filamentous fungus Aspergillus nidulans has been cloned and sequenced . There is a single H2A gene in the genome of A . nidulans, and it contains three introns . The introns are 51 nucleotides (nt), 56 nt and 50 nt in length and split codons for amino acids (aa) 18, 48 and 116 of the predicted protein . The transcriptional start and termination points have been determined using an S1 nuclease protection assay . The predicted protein is 132 aa residues in length and surprisingly has a threonine after the initiator methionine instead of the usual serine . The sequence of the predicted histone H2A protein is compared to histone H2A proteins from Schizosaccharomyces pombe, Saccharomyces cerevisiae and calf thymus . Comparison of the amino acid sequence to these other H2A proteins shows that the divergence of amino acid sequences between H2A proteins is found in two clustered sites. Mol Cell Biol, 1987 Jan, 7(1), 504 - 11 Sucl+ encodes a predicted 13-kilodalton protein that is essential for cell viability and is directly involved in the division cycle of Schizosaccharomyces pombe; Hindley J et al.; Sucl+ was originally identified as a DNA sequence that, at high copy number, rescued Schizosaccharomyces pombe strains carrying certain temperature-sensitive alleles of the cdc2 cell cycle control gene . We determined the nucleotide sequence of a 1,083-base-pair Sucl+ DNA fragment and S1 mapped its 866-nucleotide RNA transcript . The protein-coding sequence of the gene is interrupted by two intervening sequences of 115 and 51 base pairs . The predicted translational product of the gene is a protein of 13 kilodaltons . A chromosomal gene disruption of Sucl+ was constructed in a diploid S . pombe strain . Germinating spores carrying a null allele of the gene were capable of very limited cell division, following which many cells became highly elongated . The Sucl+ gene was also strongly overexpressed under the control of a heterologous S . pombe promoter . Overexpression of Sucl+ is not lethal but causes a division delay such that cells are approximately twice the normal length at division . These data suggest that Sucl+ encodes a protein which plays a direct role in the cell division cycle of S . pombe. J Bacteriol, 1987 Jan, 169(1), 93 - 6 Cloning and analysis of transcription of the mei2 gene responsible for initiation of meiosis in the fission yeast Schizosaccharomyces pombe; Shimoda C et al.; We have isolated a hybrid plasmid, pDB(mei2)2, containing a 7.4-kilobases (kb) DNA fragment from a Schizosaccharomyces pombe genomic library which is able to complement the mei2 mutation of S . pombe . Integration of the cloned DNA sequence at the mei2 site on chromosome I demonstrated that it contained the mei2 gene . This gene was localized on a 4.7-kb HindIII-PvuII fragment in the subclone pFMV402 . Transcriptional regulation was studied by Northern blot analysis in which polyadenylated RNA was prepared from a heterozygous (h+N/h-S) diploid strain cultured either in nitrogen-rich growth medium or in nitrogen-free sporulation medium . The size of the major mei2 mRNA, which always gave a broad band, was estimated to be 4.2 +/- 0.2 kb, and a few minor bands (e.g., 3.2 and 1.8 kb) appeared as well . These transcripts appeared more abundantly in sporulating cells than in growing cells . Neither the mating type genes (mat) nor the mei3 gene was essential for transcription of the mei2 gene, since ample mei2 mRNA was detected in sporulation-deficient cells transferred to sporulation medium, such as h+N/h+N and h-S/h-S homozygotes, as well as mei1 and mei3 mutants. Proc Natl Acad Sci U S A, 1987 Jan, 84(2), 388 - 92 Homology probing: identification of cDNA clones encoding members of the protein-serine kinase family; Hanks SK; Mixed oligonucleotide probes were used to screen a HeLa cDNA library for clones encoding amino acid contiguities whose conservation is characteristic of the protein-serine kinase family . Eighty thousand clones were screened, from which 19 were identified as showing strong hybridization to two distinct probes . Four clones were chosen for characterization by partial DNA sequence analysis and 3 of these were found to encode amino acid sequences typical of protein-serine kinases . One deduced amino acid sequence shares 72% identity with rabbit skeletal muscle phosphorylase kinase gamma-subunit, while another is closely related to the yeast protein-serine kinases CDC2 in Schizosaccharomyces pombe and CDC28 in Saccharomyces cerevisiae . This screening approach should have applications in the identification of clones encoding previously unknown or poorly characterized members of other protein families. Curr Genet, 1987, 12(7), 527 - 34 Cloning and expression of the OMP decarboxylase gene URA4 from Schizosaccharomyces pombe; Bach ML; URA4, the gene coding for orotidine monophosphate decarboxylase (OMPdecase), has been cloned from the fission yeast by homologous complementation and restricted in an Escherichia coli-Schizosaccharomyces pombe (E . coli-S . pombe) replicative plasmid to a 1.76 kb HindIII fragment . This plasmid is maintained at a high copy number in S . pombe and allows OMPdecase expression in Saccharomyces cerevisiae (S . cerevisiae) as well as in E . coli . After characterisation by restriction mapping and Southern hybridisation, the cloned gene was used as a probe to measure URA4 transcription and to examine its regulation . Messenger RNA levels were measured by DNA/RNA filter-hybridisation with pulse labelled RNAs during 6-azauridine (6-AUR) inhibited growth in wild type and 6-AUR sensitive strains . We found that in S . pombe the OMP analogue 6-AUR does not regulate the level of OMPdecase formation as it does in S . cerevisiae but rather modifies the ratio of total polyA+ to polyA- RNAs in the cell . Based on these results and on corresponding enzyme activities this study demonstrates divergent pyrimidine pathway regulation in the two yeasts S . cerevisiae and S . pombe . Finally, we propose the use of the URA4 gene as a convenient selective marker for genetic engineering in S . pombe. NCI Monogr, 1987, (4), 7 - 10 Molecular genetic analysis of topoisomerase II gene from Drosophila melanogaster; Hsieh TS et al.; The gene encoding the Drosophila type II DNA topoisomerase has been isolated and characterized . The enzyme is coded for by a messenger RNA of about 5000 nucleotides, the expected size for the enzyme with MWr 170,000, and the gene is interrupted by four introns . The cytogenetic location of this gene has been mapped to the left arm of chromosome 2 at 37D2-6 by both in situ hybridization to polytene chromosomes and genomic blot-hybridization . The complete nucleotide sequence of the coding region and the flanking sequence has been determined . The deduced amino acid sequence shows interesting homology with topoisomerases II from bacteria, bacteriophage T4, and yeasts . The sequence homology between the Drosophila enzyme and those from Saccharomyces and Schizosaccharomyces is very extensive . This, in combination with the similar biochemical properties among all the eucaryotic DNA topoisomerases II, indicates that these enzymes are conserved during the course of evolution. EMBO J, 1986 Dec 20, 5(13), 3665 - 71 Homology between the ran1+ gene of fission yeast and protein kinases; McLeod M et al.; The ran1+ gene of the fission yeast Schizosaccharomyces pombe is a negative regulator of both sexual conjugation and meiosis . The nucleotide sequence of the gene has been determined and contains a region of open reading frame (ORF) capable of encoding a protein of 52,000 daltons . S1 nuclease analysis of ran1+-encoded RNA showed that the ORF was spanned by an uninterrupted transcript . A fragment of DNA containing the entire ran1+ gene was expressed in a bacterial expression vector and found to encode the expected product of 52,000 daltons . The putative ran1+ gene product shares significant sequence homology with known protein kinases . The level of the ran1+ transcript was similar in vegetative and meiotic cells suggesting that the ran1+ protein product rather than its transcript is regulated during sexual differentiation. J Biol Chem, 1986 Dec 15, 261(35), 16351 - 5 Antisuppressor mutations and sulfur-carrying nucleosides in transfer RNAs of Schizosaccharomyces pombe; Grossenbacher AM et al.; Antisuppressor mutations reduce the efficiency of nonsense suppressors . A mutation in the gene sin4 of Schizosaccharomyces pombe leads to loss of 5-(methoxycarbonylmethyl) thiouridine (mcm5s2U) from the first anticodon position of tRNAs . This resembles the phenotype of sin3 (Heyer, W . D., Thuriaux, P., Kohli, J., Ebert, P., Kersten, H., Gehrke, C., Kuo, K . C., and Agris, P . F . (1984) J . Biol . Chem . 259, 2856-2862), but the mutations reside in different genes . In vivo 35S-labeled tRNA from the parental suppressor strain sup3, the antisuppressor strains sin3 and sin4, and the double mutant sin3 sin4 has been digested to nucleosides and analyzed with high performance liquid chromatography methods . The major sulfur-carrying nucleoside in wild-type S . pombe tRNA is mcm5s2U . It is reduced in the mutant strains . Two other thiolated nucleosides are also present: 2-thiouridine and a nucleoside of unknown structure . Neither was affected by the antisuppressor mutations . Thiocytidine has not been found . Independent from their effect on suppressors, the two mutations sin3 and sin4 reduce the growth rate of cells, and sin3 also increases cell length . In vivo decoding of the serine codon UCG by the UCA reading serine tRNA is not promoted by the two antisuppressor mutations. J Biol Chem, 1986 Dec 5, 261(34), 15877 - 82 Identification and characterization of thiamin repressible acid phosphatase in yeast; Schweingruber ME et al.; We have identified a genetic locus, pho4, in Schizosaccharomyces pombe which encodes a minor expressed cell surface acid phosphatase that is repressed by low concentrations (0.5 microM) of thiamin . The enzyme was purified from a strain that overproduces the enzyme . It is an Asn-linked glycoprotein . Removal of the carbohydrates by endoglycosidase H does not abolish enzymatic activity . The molecular mass of deglycosylated and unglycosylated enzyme that accumulates in membranes when cells are grown in the presence of tunicamycin is 56 kDa as determined by sodium dodecyl sulfate-gel electrophoresis . Thiamin regulation, at least in part, operates by reducing the level of pho4-mRNA . Pho4 is not genetically linked to the phosphate repressible acid phosphatase gene pho1 . Phosphate and thiamin repressible acid phosphatase differ in their substrate specificity . Their protein moieties are immunologically related . Pho4 and pho1 are the only genes in S . pombe that express cell surface acid phosphatases being enzymatically active with nitrophenyl phosphate as substrate . S . pombe is not unique in having a thiamin repressible acid phosphatase . In Saccharomyces cerevisiae this enzyme is encoded by PHO3. J Bacteriol, 1986 Dec, 168(3), 1439 - 43 Malate transport in Schizosaccharomyces pombe; Osothsilp C et al.; The transport of malate was studied in a Schizosaccharomyces pombe wild-type strain and in mutant strains unable to utilize malic acid . Two groups of such mutants, i.e., malic enzyme-deficient and malate transport-defective mutants, were differentiated by a 14C-labeled L-malate transport assay and by starch gel electrophoresis followed by activity staining for malic enzyme (malate dehydrogenase {oxaloacetate decarboxylating} {NAD+}; 1.1.1.38) and malate dehydrogenase (1.1.1.37) . Transport of malate in S . pombe was constitutive and strongly inhibited by inhibitors of oxidative phosphorylation and of the formulation of proton gradients . Transport was a saturable function of the malate concentration . The apparent Km and Vmax values for transport by the parent were 3.7 mM and 40 nmol/min per mg of protein, respectively, while those of the malic enzyme-deficient mutant were 5.7 mM and 33 nmol/min per mg of protein, respectively . Malate transport was pH and temperature dependent . The specificity of transport was studied with various substrates, including mono- and dicarboxylic acids, and the possibility of a common transport system for dicarboxylic acids is discussed. J Cell Sci, 1986 Dec, 86, 191 - 206 Change in the rate of CO2 production in synchronous cultures of the fission yeast Schizosaccharomyces pombe: a periodic cell cycle event that persists after the DNA-division cycle has been blocked; Novak B et al.; CO2 production has been followed by manometry in synchronous and asynchronous cultures of Schizosaccharomyces pombe prepared by elutriation from the same initial culture . The rate of production follows a linear pattern in synchronous cultures with a rate change once per cycle at the time of cell division . This pattern is most clearly shown in oscillations of the difference between values of the second differential (acceleration) for the synchronous and asynchronous cultures . The association between the rate change and the time of division is maintained during growth speeded up in rich medium and slowed down in poor medium and at lower temperature . It is also maintained after a shift-up in temperature . Results with wee mutants suggest that the association is with the S period rather than division itself . The rate and acceleration of CO2 production are approximately proportional to cell size (protein content) in asynchronous cultures . When synchronous cultures of the temperature-sensitive mutants cdc2.33 and cdc2.33 wee1.6 are shifted up to the restrictive temperature, the DNA-division cycle is blocked . The oscillatory pattern of CO2 production, however, continues for one to two cycles until the acceleration reaches a constant value, after which the oscillations are undetectable . This point is reached later in the double mutant and there is a phase difference in the oscillations compared to those in the single mutant . With both blocked mutants the 'free-running' oscillations are about 15% shorter than the normal cycle time . There are well-known examples of such oscillations in eggs but they are rare in growing systems. J Cell Sci, 1986 Dec, 86, 207 - 15 Nucleoside diphosphokinase, an enzyme with step changes in activity during the cell cycle of the fission yeast Schizosaccharomyces pombe . I . Persistence of steps after a block to the DNA-division cycle; Creanor J et al.; In confirmation of earlier results, nucleoside diphosphokinase is shown to be a 'step' enzyme in Schizosaccharomyces pombe with a sharp doubling in activity at the beginning of the cell cycle . These doubling steps occur at the same time in the cycle in the smaller cells of the mutant wee1.6 . An important result is that the activity steps persist with normal cell cycle timing after a block to the DNA-division cycle imposed by the cycle mutants cdc2.33 and cdc2.33wee1.6 . This is clear proof that oscillatory controls of some cell cycle events can persist after the main periodic events of the DNA-division cycle have been abolished. Proc Natl Acad Sci U S A, 1986 Nov, 83(21), 8253 - 7 Analysis of centromeric DNA in the fission yeast Schizosaccharomyces pombe; Clarke L et al.; The Schizosaccharomyces pombe centromere-linked genes, LYS1 and CYH1 on chromosome I and TPS13 and RAN1 on chromosome II, have been isolated . The genetic order of these markers with respect to their centromeres was determined to establish relative directionality on the genetic and physical maps . Chromosome walking toward the centromeres reveals a group of repetitive sequences that occur only in the centromere regions of chromosomes I and II and at one other specific location in the S . pombe genome, presumably the centromere of chromosome III . The major class of large repeated sequence elements is 6.4 kilobases (kb) long (repeat K), portions of which occur at least twice on chromosome II and in several tandemly arranged intact copies at another centromeric location . Repeat K in turn contains groups of smaller repeats . Genetic recombination is strongly suppressed in the centromere II region, which contains at least 30 kb of repeated sequences . Centromeric DNA organization is much more complex in fission yeast than has been described in budding yeast (Saccharomyces cerevisiae), possibly because of the larger more condensed nature of the S . pombe chromosomes. Cell, 1986 Oct 10, 47(1), 49 - 59 U2 RNA from yeast is unexpectedly large and contains homology to vertebrate U4, U5, and U6 small nuclear RNAs; Ares M Jr; I have determined the structure of the gene from Saccharomyces cerevisiae coding for the yeast homolog of vertebrate U2 snRNA . Surprisingly, the RNA is 1175 nucleotides long, six times larger than U2 RNAs from other organisms, including Schizosaccharomyces pombe . Nearly 100 nucleotides of the large RNA share sequence homology and potential secondary structure with metazoan U2 . The large RNA also contains homology to vertebrate U4, U5, and U6 snRNAs, implying a "poly-snRNP" structure for the RNP containing the large RNA . The gene LSR1, encoding the large RNA, is essential for growth, suggesting that the yeast spliceosome can be dissected using genetic approaches . The different organization of spliceosomal RNA may underlie differences in splicing between yeast and metazoans. Mol Cell Biol, 1986 Oct, 6(10), 3523 - 30 Site-specific mutagenesis of cdc2+, a cell cycle control gene of the fission yeast Schizosaccharomyces pombe; Booher R et al.; The cdc2+ gene of Schizosaccharomyces pombe is homologous to the CDC28 gene of Saccharomyces cerevisiae . Both genes share limited homology with vertebrate protein kinases and have protein kinase activity . cdc2+ has been subjected to mutagenesis in vitro . A null allele of the gene, constructed by insertion of the S . cerevisiae LEU2 gene into a site within the gene, has a phenotype similar to that of many temperature-sensitive alleles of cdc2 . Mutations within the predicted ATP-binding site and in a region which may be a site of phosphorylation result in loss of cdc2+ activity . A single substitution of Gly-146 to Asp-146 has been identified in cdc2-1w, a dominant activated allele of the gene . The four introns within the cdc2+ gene have been deleted . The resulting gene not only functions in fission yeast but also rescues cdc28(Ts) strains of S . cerevisiae, a property which is not shared by the genomic cdc2+ gene. Proc Natl Acad Sci U S A, 1986 Oct, 83(20), 7860 - 4 Functional complementation between mutations in a yeast suppressor tRNA gene reveals potential for evolution of tRNA sequences; Willis I et al.; Successive rounds of mutagenesis of a Schizosaccharomyces pombe strain bearing the UGA-reading sup3 tRNASer suppressor have been carried out for two cycles of inactivation and reactivation of the suppressor . The suppressor phenotype at each stage was found to involve different combinations of three mutations, A30, A53, and A67, in the sup3-UGA gene . Single mutations A30 and A53 inactivate the suppressor as does the presence of all three mutations . A67 by itself is phenotypically neutral, but in combination with either A30 or A53 suppressor function is restored . The frequency with which these and other complementation events occur in S . pombe demonstrates a significant potential for nucleotide sequence evolution in tRNA . Differential expression of the S . pombe genes in Saccharomyces cerevisiae suggests that the two yeasts have diverged at the transcriptional and RNA processing level . Processing of the mutant tRNA precursors in S . cerevisiae reveals a hierarchy of structural domains within the tRNA that vary in their importance for RNase P cleavage. FEBS Lett, 1986 Sep 29, 206(1), 135 - 41 Immunological cross-reactivity of fungal and yeast plasma membrane H+-ATPase; Vai M et al.; The plasma membrane H+-ATPases from fungi and yeasts have similar catalytic and molecular properties . A structural comparison has been performed using immunoblot analysis with polyclonal antibodies directed toward the 102 kDa polypeptide of the plasma membrane H+-ATPase from Neurospora crassa . A strong cross-reactivity is observed between the fungal H+-ATPase and the enzyme from the yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe . Structural homologies are indicated also by the analysis of the cross-reactive peptides originated by proteolytic digestion of Neurospora and S . cerevisiae purified enzymes . Neither enzyme from these two sources appears to be glycosylated by a highly sensitive concanavalin A affinity assay on blotted proteins . A glycoprotein of Mr 115000 and pI 4.8-5, which comigrates with a cell cycle-modulated protein on 2D gel, is present in partially purified preparations of plasma membrane H+-ATPase of S . cerevisiae and it is shown to be structurally unrelated to H+-ATPase. EMBO J, 1986 Sep, 5(9), 2355 - 61 The nucleotide sequence of the fission yeast DNA topoisomerase II gene: structural and functional relationships to other DNA topoisomerases; Uemura T et al.; We have determined the complete nucleotide sequence of a 5.3-kb long genomic DNA fragment of the fission yeast Schizosaccharomyces pombe that encodes DNA topoisomerase II . It contains a 4293 bp long single open reading frame . The predicted polypeptide has 1431 residues (mol . wt 162,000) and shows three characteristic domains; the large C-terminal region, which consists of alternating acidic-basic stretches and might be a chromatin-binding domain, the NH2 half domain homologous to the ATP-binding gyrB subunit of bacterial gyrase and the central-to-latter part which is homologous to the NH2 domain of the catalytic gyrA subunit, suggesting a possible evolutionary consequence of the gene fusion of the bacterial gyrase subunits into the eucaryotic DNA topoisomerase II gene . We have found that the cloned fission yeast TOP2 gene can complement the budding yeast top2 mutation, although the fission yeast TOP2 protein sequence is only 50% homologous to the recently determined sequence of budding yeast (J.C . Wang, personal communication) . Conversely, the budding yeast TOP2 gene can complement the fission yeast top2 mutations, indicating that their DNA topoisomerase II genes are functionally exchangeable. Cell, 1986 Aug 29, 46(5), 725 - 31 Initiation of meiotic recombination by double-strand DNA breaks in S . pombe; Klar AJ et al.; Mitotic gene conversion and reciprocal recombination have recently been shown to be efficiently initiated by double-strand DNA breaks (DSBs) in both Saccharomyces cerevisiae and Schizosaccharomyces pombe . We tested whether DSBs could also initiate meiotic recombination at the mat1 locus in S . pombe . The mat1 switching-mechanism-generated DSB found in mitotically growing cells can be repaired without mat1 switching, since strains deleted for both donor loci (mat2-P and mat3-M) have the break but do not produce inviable cells . A (mat1-P X mat1-M) cross produced a high frequency (20%) of 3:1 gene conversions of mat1 in meiotic tetrads . Gene conversion events were associated with the recombination of flanking markers . Strains lacking the DSB failed to convert . Thus, the DSB at mat1 promotes efficient meiotic recombination in fission yeast. Microbiol Sci, 1986 Aug, 3(8), 234 - 7 Regulation of meiosis in Schizosaccharomyces pombe; Yamamoto M; Analysis of a new class of meiotic mutants isolated in the fission yeast Schizosaccharomyces pombe strongly indicates that the gene in which they are deficient codes for a factor whose physiological role is inhibition of initiation of meiosis . A negative control mechanism for meiosis is discussed. EMBO J, 1986 Jul, 5(7), 1697 - 703 Two RNA species co-purify with RNase P from the fission yeast Schizosaccharomyces pombe; Krupp G et al.; RNase P activity from Schizosaccharomyces pombe co-purifies with two RNA species . These RNAs are associated with enzyme activity as judged by titrated micrococcal nuclease inactivation experiments . The two RNAs, K1- and K2-RNA, are 285 and 270 nucleotides long, respectively . Both RNAs are transcribed from one gene, present in a single copy in the haploid genome . The primary and a secondary structure of K RNAs have been determined and compared with M1 RNA, their counterpart from Escherichia coli . Very limited sequence homology was observed, and this agrees with the finding that no cross-hybridization with M1 RNA can be detected in a Southern analysis with yeast genomic DNA . However, the secondary structures of K RNA and M1 RNA show the same basic organization and one conserved local motif, the sequence GUG--AGGPu in an exposed hairpin loop. Eur J Biochem, 1986 Jul 1, 158(1), 133 - 40 Glycosylation and secretion of acid phosphatase in Schizosaccharomyces pombe; Schweingruber AM et al.; We have purified secreted acid phosphatase of Schizosaccharomyces pombe . The enzyme is N-glycosylated, the associated carbohydrate accounts for 90% of the total molecular mass and the protein moiety has a molecular mass of 54 kDa . The deglycosylated enzyme still exhibits enzymatic activity . Using antibodies recognizing the protein moiety of the enzyme we have identified two intracellular precursors of acid phosphatase: an unglycosylated membrane-bound 54-kDa form that accumulates in the presence of tunicamycin and a partially glycosylated 72-kDa form that accumulates mostly in membranes of cells grown in rich medium . We further showed that the conversion of the 54-kDa and 72-kDa forms to partially glycosylated and fully glycosylated acid phosphatase is a regulated process . Growth conditions determine how much of translated 54-kDa acid phosphatase is glycosylated to the 72-kDa form and how much remains unglycosylated in membranes . When cells are grown in a rich medium, 5% of the total acid phosphatase protein remains as unglycosylated enzyme and 8% as partially glycosylated 72-kDa form . In cells grown in the minimal medium, however, all of the 54-kDa and 72-kDa forms of acid phosphatase are rapidly processed to fully glycosylated enzyme . The 72-kDa form and the unglycosylated form of acid phosphatase are not secreted or transported to the plasma membrane. Exp Cell Res, 1986 Jul, 165(1), 243 - 54 A second growth state for Schizosaccharomyces pombe; Kubitschek HE et al.; The kinetics of volume increase in individual cells of Schizosaccharomyces pombe were determined by phase microscopy at osmolalities lower than those reported in the literature . At the highest osmolality, 550 mmol/kg, all cells followed a biphasic pattern of growth, in which cell volumes increased to their maximum values approximately four-fifths of the way through the growth cycle . At lower osmolalities (400-420 mmol/kg), many or most of the cells followed a different growth pattern, with a linear increase in cell volume throughout the cycle . The following evidence indicates that a different regulatory mechanism is responsible for the linear growth pattern: (1) Regulation of cell length and diameter differed for the two cases . During biphasic growth, cell length also increased biphasically and cell diameters remained essentially constant during the cycle, whereas during linear growth, both cell length and diameter increased linearly until formation of the cell plate very late in cycle . (2) The two different growth states were observed for cells growing on two very different kinds of medium . (3) Frequency distributions of the two growth patterns showed that there were two distinct groups of growing cells, with and without a cell volume plateau; these results rule out a single growth state in which plateaus are graded from large to infinitesimally small . (4) Linear regressions fitted to the data for linear growth did not differ significantly from the theoretical model for linear growth without a terminal plateau . These results reveal the operation of a second regulatory system for cell growth in S . pombe at osmolalities closer to those in liquid medium . The occurrence of transitions between the two growth states in successive generations and the agreement between several growth parameters for the two modes suggest that the growth states are closely related. EMBO J, 1986 Jul, 5(7), 1705 - 9 Periodic transcription as a means of regulating gene expression during the cell cycle: contrasting modes of expression of DNA ligase genes in budding and fission yeast; White JH et al.; Using cultures synchronised by three independent procedures, we have shown that the CDC9 gene, coding for DNA ligase, is periodically expressed in the Saccharomyces cerevisiae cell cycle . The level of CDC9 transcript increases many fold in late G1 reaching a peak at about the G1/S phase boundary and preceding the peak in histone message by some 20 min . The level of DNA ligase itself also fluctuates, showing the expected pattern for a stable enzyme synthesised periodically . In contrast, the transcript from the DNA ligase gene (CDC17) of Schizosaccharomyces pombe is present at a constant level throughout the cell cycle, and no fluctuation in amount was detected, although the histone H2A showed the expected periodic synthesis . Furthermore, DNA ligase activity remains at a constant level during the S . pombe cell cycle showing that there is unlikely to be any form of translational control . These contrasting modes of expression of the DNA ligase genes in the two organisms suggests that when periodic transcription is observed from an essential cell cycle gene, it may have no particular significance for regulating progress through the cell cycle . Also, regulatory circuits may be less well conserved between organisms than the processes they control and thus different organisms may utilise quite different modes of control to achieve the same ends. J Biol Chem, 1986 Jun 5, 261(16), 7151 - 9 Chemical modification of thiol groups of mitochondrial F1-ATPase from the yeast Schizosaccharomyces pombe . Involvement of alpha- and gamma-subunits in the enzyme activity; Falson P et al.; Mitochondrial F1-ATPase from the yeast Schizosaccharomyces pombe has been prepared under a stable form and in relatively high amounts by an improved purification procedure . Specific chemical modification of the enzyme by the thiol reagent N-ethylmaleimide (NEM) at pH 6.8 leads to complete inactivation characterized by complex kinetics and pH dependence, indicating that several thiols are related to the enzyme activity . A complete protection against NEM effect is afforded by low concentrations of nucleotides in the presence of Mg2+, with ADP and ATP being more efficient than GTP . A total binding of 5 mol of {14C}NEM/mol of F1-ATPase is obtained when the enzyme is 85% inactivated: 3 mol of the label are located on the alpha-subunits and 2 on the gamma-subunit . Two out of the 3 mol on the alpha-subunits bind very rapidly before any inactivation occurs, indicating that the two thiols modified are unrelated to the inactivation process . Complete protection by ATP against inactivation by NEM prevents the modification of three essential thiols out of the group of five thiols labeled in the absence of ATP: one is located on a alpha-subunit and two on the gamma-subunit . These two essential thiols of the gamma-subunit can be differentiated by modification with 6,6'-dithiodinicotinic acid (CPDS), another specific thiol reagent . A maximal binding of 4 mol of {14C}CPDS/mol of enzyme is obtained, concomitant to a 25% inhibition . Sequential modification of the enzyme by CPDS and {14C}NEM leads to the same final deep inactivation as that obtained with {14C}NEM alone . One out of the two thiols of the gamma-subunit is no longer accessible to {14C}NEM after CPDS treatment . When incubated at pH 6.8 with {3H}ATP in the presence of Mg2+, F1-ATPase is able to bind 3, largely exchangeable, mol of nucleotide/mol of enzyme . Modification of the three essential thiols by NEM dramatically decreases the binding of 3H-nucleotide down to about 1 mol/mol of enzyme . Partial modification modifies the cooperative properties, the enzyme being no longer sensitive to anion activation. Mol Cell Biol, 1986 Jun, 6(6), 2168 - 78 Differential expressions of essential and nonessential alpha-tubulin genes in Schizosaccharomyces pombe; Adachi Y et al.; The fission yeast Schizosaccharomyces pombe has two alpha-tubulin genes and one beta-tubulin gene . Gene disruption experiments showed that the alpha 1-tubulin gene (NDA2) is essential whereas the alpha 2 gene is dispensable . The alpha 2-disrupted cells missing alpha 2 transcript and alpha 2 polypeptide could grow and sporulate normally . The alpha 2 gene, however, was expressed in the wild type and the alpha 1 mutant . Alpha 2-Tubulin was distinguished as an electrophoretic band and was assembled into microtubules . The alpha 2-disrupted cells had an increased sensitivity to an antimicrotubule drug thiabendazole, and the alpha 1(cold-sensitive {cs}) alpha 2 (disrupted) cells became not only cs but also temperature sensitive . Northern blot experiments indicated that alpha 2 transcription was minor and constitutive whereas alpha 1 transcription was major and modulated, depending on the gene copy number of the alpha 2 gene . The amounts of alpha 1 and alpha 2 polypeptides estimated by beta-galactosidase activities of the lacZ-fused genes integrated on the chromosome and by intensities of the electrophoretic bands in crude tubulin fractions, however, were comparable, indicating that alpha 2 tubulin is not a minor subtype . We assume that the cells of Schizosaccharomyces pombe have no excess tubulin pool . alpha 1 mutants would then be blocked in the cell cycle because only half the amount of functional alpha-tubulin required for growth can be produced by the alpha 2 gene . On the other hand, the alpha 2-disrupted cells became viable because the synthesis of alpha 1 tubulin was increased by transcriptional or translational modulation or both . The real cause for essential alpha 1 and dispensable alpha 2 genes seems to be in their regulatory sequences instead of the coding sequences. J Bacteriol, 1986 Jun, 166(3), 779 - 86 Metabolism of the phospholipid precursor inositol and its relationship to growth and viability in the natural auxotroph Schizosaccharomyces pombe; Fernandez S et al.; Phospholipid metabolism in the fission yeast Schizosaccharomyces pombe was examined . Three enzymes of phospholipid biosynthesis, cytidine diphosphate diacylglycerol synthase (CDP-DG), phosphatidylinositol (PI) synthase, and phosphatidylserine (PS) synthase, were characterized in extracts of S . pombe cells . Contrary to an earlier report, we were able to demonstrate that CDP-DG served as a precursor for PI and PS biosynthesis in S . pombe . S . pombe is naturally auxotrophic for the phospholipid precursor inositol . We found that S . pombe was much more resistant to loss of viability during inositol starvation than artificially generated inositol auxotrophs of Saccharomyces cerevisiae . The phospholipid composition of S . pombe cells grown in inositol-rich medium (50 microM) was similar to that of S . cerevisiae cells grown under similar conditions . However, growth of S . pombe at low inositol concentrations (below 30 microM) affected the ratio of the anionic phospholipids PI and PS, while the relative proportions of other glycerophospholipids remained unchanged . During inositol starvation, the rate of PI synthesis decreased rapidly, and there was a concomitant increase in the rate of PS synthesis . Phosphatidic acid and CDP-DG, which are precursors to these phospholipids, also increased when PI synthesis was blocked by lack of exogenous inositol . The major product of turnover of inositol-containing phospholipids in S . pombe was found to be free inositol, which accumulated in the medium and could be reused by the cell. J Biol Chem, 1986 May 5, 261(13), 5878 - 85 A single base change in the intron of a serine tRNA affects the rate of RNase P cleavage in vitro and suppressor activity in vivo in Saccharomyces cerevisiae; Willis I et al.; Differences in the processing of dimeric tRNASer-tRNAMet precursors derived from the Schizosaccharomyces pombe sup9 wild-type and opal suppressor genes can be attributed to conformational alterations in the tRNASer anticodon/intron domain . A comparison of the patterns obtained upon transcription of the sup9+ (wild-type) and sup9-e (opal suppressor) genes in a coupled transcription/processing extract from Saccharomyces cerevisiae reveals that the latter exhibits a greatly reduced efficiency of 5'-end maturation and is susceptible to specific endonucleolytic cleavage(s) within the intron . Free energy calculations indicate that these effects coincide with a destabilization of the wild-type anticodon/intron stem and suggest that the predominant sup9-e conformer lacks secondary structure in this region . Evidence in support of this hypothesis was obtained by analyzing the processing of sup9+ and sup9-e precursors carrying the intron base substitution, G37:10, which destroys and restores, respectively, the base-pairing potential of the proposed secondary structure and comparing the strength and temperature sensitivity of sup9-e and sup9-e G37:10 suppression in vivo in S . cerevisiae . The data indicate that the anticodon/intron structure of tRNA precursors can influence the rate of RNase P cleavage in vitro and affect tRNA expression in vivo. J Bacteriol, 1986 May, 166(2), 484 - 90 Cloning and expression of a Saccharomyces diastaticus glucoamylase gene in Saccharomyces cerevisiae and Schizosaccharomyces pombe; Erratt JA et al.; A recombinant plasmid pool of the Saccharomyces diastaticus genome was constructed in plasmid YEp13 and used to transform a strain of Saccharomyces cerevisiae . Six transformants were obtained which expressed amylolytic activity . The plasmids each contained a 3.9-kilobase (kb) BamHI fragment, and all of these fragments were cloned in the same orientations and had identical restriction maps, which differed from the map of the STA1 gene (I . Yamashita and S . Fukui, Agric . Biol . Chem . 47:2689-2692, 1983) . The glucoamylase activity exhibited by all S . cerevisiae transformants was approximately 100 times less than that of the donor strain . An even lower level of activity was obtained when the recombinant plasmid was introduced into Schizosaccharomyces pombe . No expression was observed in Escherichia coli . The 3.9-kb BamHI fragment hybridized to two sequences (4.4 and 3.9 kb) in BamHI-digested S . diastaticus DNA, regardless of which DEX (STA) gene S . diastaticus contained, and one sequence (3.9 kb) in BamHI-digested S . cerevisiae DNA . Tetrad analysis of crosses involving untransformed S . cerevisiae and S . diastaticus indicated that the 4.4-kb homologous sequence cosegregated with the glucoamylase activity, whereas the 3.9-kb fragment was present in each of the meiotic products . Poly(A)+ RNA fractions from vegetative and sporulating diploid cultures of S . cerevisiae and S . diastaticus were probed with the 3.9-kb BamHI fragment . Two RNA species, measuring 2.1 and 1.5 kb, were found in both the vegetative and sporulating cultures of S . diastaticus, whereas one 1.5-kb species was present only in the RNA from sporulating cultures of S . cerevisiae. J Mol Biol, 1986 Apr 5, 188(3), 343 - 53 Inactivation of nonsense suppressor transfer RNA genes in Schizosaccharomyces pombe . Intergenic conversion and hot spots of mutation; Heyer WD et al.; Intergenic conversion is a mechanism for the concerted evolution of repeated DNA sequences . A new approach for the isolation of intergenic convertants of serine tRNA genes in the yeast Schizosaccharomyces pombe is described . Contrary to a previous scheme, the intergenic conversion events studied in this case need not result in functional tRNA genes . The procedure utilizes crosses of strains that are homozygous for an active UGA suppressor tRNA gene, and the resulting progeny spores are screened for loss of suppressor activity . In this way, intergenic convertants of a tRNA gene are identified that inherit varying stretches of DNA sequence from either of two other tRNA genes . The information transferred between genes includes anticodon and intron sequences . Two of the three tRNA genes involved in these information transfers are located on different chromosomes . The results indicate that intergenic conversion is a conservative process . No infidelity is observed in the nucleotide sequence transfers . This provides further evidence for the hypothesis that intergenic conversion and allelic conversion are the result of the same molecular mechanism . The screening procedure for intergenic revertants also yields spontaneous mutations that inactivate the suppressor tRNA gene . Point mutations and insertions of A occur at various sites at low frequency . In contrast, A insertions at one specific site occur with high frequency in each of the three tRNA genes . This new type of mutation hot spot is found also in vegetative cells. Environ Health Perspect, 1986 Mar, 65, 13 - 9 Unique properties of Cd-binding peptides induced in fission yeast, Schizosaccharomyces pombe; Hayashi Y et al.; Metallothioneins, a class of low molecular weight cysteine-rich proteins that bind heavy metal ions, have been found in various eucaryotic organisms . When fission yeasts are grown in the presence of high concentration of CdCl2, large amounts of Cd-binding peptides (Cd-BP1 and Cd-BP2) are synthesized . Cd-BP1 (MW 4000) contains 4 mole of small unit peptide (cadystin, MW 771), 6 mole of Cd2+, and 1 mole of the labile sulfide; on the other hand, Cd-BP2 (MW 1800) contains 2 mole of cadystin and 2 mole of Cd2+ . While Cd-BP2 shows similarities to mammalian Cd-thioneins in UV and CD spectra, Cd-BP1 has a characteristic shoulder at 265 nm in the UV absorption spectrum and shows two marked Cotton bands at 257 nm (negative) and 275 nm (positive) . These characteristics of Cd-BP1 are not found in the other Cd-thioneins . When Cd-BP1 is acidified (pH 2.0) and successively neutralized, a shoulder of 265 nm in the UV spectrum and a Cotton band at 275 nm disappear, and the molecular weight changes from 4000 to 1800, with simultaneous loss of the labile sulfide . While the reconstituted complex without labile sulfide showed the characteristics of Cd-BP2, the reconstituted complex in the presence of labile sulfide indicated partial reconstitution of Cd-BP1 . The UV and CD spectra differences between reconstituted and native Cd-BP1 suggest the requirement for some additional molecular architecture including another peptide-Cd2+ interaction . Induction of cadystin synthesis is almost exclusive for Cd, but an exception is a small amount of cadystin also induced by the higher concentration of CuCl2 (2.5 mM).(ABSTRACT TRUNCATED AT 250 WORDS) Plasmid, 1986 Mar, 15(2), 156 - 8 Vectors for the construction of gene banks and the integration of cloned genes in Schizosaccharomyces pombe and Saccharomyces cerevisiae; Wright A et al.; We have constructed a variety of vectors for use in both budding yeast (Saccharomyces cerevisiae) and fission yeast (Schizosaccharomyces pombe) . Four of these, pDB262, pWH4, pWH5, and pMAK262, have positive selection for the insertion of cloned DNA, making them convenient for the construction of gene banks . pDB262, pWH4 and pWH5 contain the 2 mu ARS and the LEU2 gene from S . cerevisiae and can be used for gene isolation . They can also be converted into integration vectors for use in the genetic mapping of cloned sequences . pMAK262 contains only the LEU2 gene from budding yeast and can be used to screen for ARS elements or for gene integration . We also describe two other integration vectors, pDAM3 and pDAM6, which have a variety of restriction sites suitable for subcloning. J Biol Chem, 1986 Feb 25, 261(6), 2936 - 41 Isolation and characterization of the structural gene for secreted acid phosphatase from Schizosaccharomyces pombe; Elliott S et al.; The Schizosaccharomyces pombe acid phosphatase structural gene (PHO 1) was isolated by complementation of an S . pombe acid phosphatase mutant with a wild type S . pombe DNA recombinant plasmid library . Northern analysis indicates that acid phosphatase is encoded by a 1.4-kilobase mRNA of which approximately 100 bases are 3'-poly(A) . The gene contains no introns and the 3' and 5' untranslated regions are short . According to DNA and amino acid sequence data, the S . pombe acid phosphatase has a molecular weight of 50,600 . An 18-amino acid sequence at the N terminus was found that is similar to previously identified signal peptides in other eukaryotic secretory proteins . This signal peptide is apparently removed during secretion, since it is absent in the mature secreted acid phosphatase . The gene can be induced 2--3-fold by starvation for phosphate . The signals required for this induction are contained on the isolated DNA clone . Although the gene can be expressed in Saccharomyces cerevisiae, secretion is abnormal. J Theor Biol, 1986 Feb 21, 118(4), 405 - 26 Sloppy size control of the cell division cycle; Tyson JJ et al.; In an asynchronous, exponentially proliferating cell culture there is a great deal of variability among individual cells in size at birth, size at division and generation time (= age at division) . To account for this variability we assume that individual cells grow according to some given growth law and that, after reaching a minimum size, they divide with a certain probability (per unit time) which increases with increasing cell size . This model is called sloppy size control because cell division is assumed to be a random process with size-dependent probability . We derive general equations for the distribution of cell size at division, the distribution of generation time, and the correlations between generation times of closely related cells . Our theoretical results are compared in detail with experimental results (obtained by Miyata and coworkers) for cell division in fission yeast, Schizosaccharomyces pombe . The agreement between theory and experiment is superior to that found for any other simple models of the coordination of cell growth and division. J Cell Sci, 1986 Feb, 80, 253 - 68 Mitosis in the fission yeast Schizosaccharomyces pombe as revealed by freeze-substitution electron microscopy; Tanaka K et al.; Nuclear division in Schizosaccharomyces pombe has been studied in transmission electron micrographs of sections of cells fixed by a method of freeze-substitution . We have found cytoplasmic microtubules in the vicinity of the spindle pole bodies and two kinds of microtubules, short discontinuous ones and long, parallel ones in the intranuclear mitotic spindle . For most of the time taken by nuclear division the spindle pole bodies face each other squarely across the nuclear space but early in mitosis they briefly appear twisted out of alignment with each other, thereby imparting a sigmoidal shape to the bundle of spindle microtubules extending between them . This configuration is interpreted as indicating active participation of the spindle in the initial elongation of the dividing nucleus . It is proposed that mitosis is accompanied by the shortening of chromosomal microtubules simultaneously with the elongation of the central pole-to-pole bundle of microtubules of the intranuclear spindle . Daughter nuclei are separated by the sliding apart of interdigitating microtubules of the spindle at telophase . Some of the latter bear dense knobs at their ends. Mol Gen Genet, 1986 Feb, 202(2), 291 - 3 The fission yeast cell cycle control gene cdc2: isolation of a sequence suc1 that suppresses cdc2 mutant function; Hayles J et al.; A DNA fragment called suc1 has been found to rescue cells mutated in the cell cycle control gene cdc2 of the fission yeast Schizosaccharomyces pombe . The suppressing activity of suc1 is observed when it is present on a multicopy number plasmid . The gene does not hybridize to cdc2 and maps elsewhere in the genome . Its effect is cdc2 allele specific suggesting that it interacts directly with the cdc2 gene function. Cell, 1986 Jan 31, 44(2), 329 - 36 Role of a ras homolog in the life cycle of Schizosaccharomyces pombe; Fukui Y et al.; We have analyzed the function of the only ras homolog in S . pombe detectable by Southern blotting, ras1, which is homologous to mammalian ras genes and has been cloned . We have disrupted the ras1 gene and have replaced it with ras1Val17, which corresponds to a transforming variant of mammalian ras . Loss of ras1 activity by disruption results in the complete inability to mate . The cell body of a ras1- strain is extensively deformed, and a ras1-/ras1- diploid sporulates very poorly . Unlike RAS1 and RAS2 of S . cerevisiae, ras1 of S . pombe appears to have no effect on adenylate cyclase activity . This suggests that the target enzymes presumably modulated by ras proteins in signal transduction are not the same for all organisms. Antonie Van Leeuwenhoek, 1986, 52(1), 45 - 51 Long-chain fatty acid composition of selected genera of yeasts belonging to the Endomycetales; Viljoen BC et al.; The cellular long-chain fatty acids of 36 strains representing 18 genera of the Saccharomycetace, Endomycetaceae, Metchnikowiaceae, Saccharomycodaceae, Schizosaccharomycetaceae and Dipodascaceae were extracted and analyzed as methyl esters by gas chromatography . On the basis of their fatty acid content the set of strains was divided into 6 groups, coinciding with the above families . The members of the Saccharomycetaceae (group I) had a high percentage of oleic acid while the strains classified under the Endomycetaceae (group II) and Metchnikowiaceae (group III) were characterized by oleic acid and linoleic acid as major fatty acids . The Saccharomycodaceae (group IV) had the highest percentage of palmitoleic acid . The Schizosaccharomycetaceae (group V) had the highest percentage of oleic acid, while the Dipodascacea (group VI) were characterized by a high percentage of linoleic acid. CRC Crit Rev Biochem, 1986, 21(2), 153 - 223 Control of cell growth and division in Saccharomyces cerevisiae; Hanes SD et al.; Considerable advances have been made in recent years in our understanding of the biochemistry of protein and nucleic acid synthesis and, particularly, the molecular biology of gene expression in eukaryotes . The yeast Saccharomyces cerevisiae, and to a lesser extent Schizosaccharomyces pombe, has had a preeminent role as a focus for these studies, principally because of the facility with which these organisms can be experimentally manipulated biochemically and genetically . This review will be designed to critically examine and integrate recent advances in several vital areas of regulatory control of enzyme synthesis in yeast: structure and organization of DNA, transcriptional regulation, post-transcriptional modification, control of translation, post-translational modification and secretion, and cell-cycle modulation . It will attempt to emphasize and illustrate, where detailed information is available, principal underlying molecular mechanisms, and it will attempt to make relevant comparisons of this material to inferred and demonstrated facets of regulatory control of enzyme and protein synthesis in higher eukaryotes. J Cell Sci Suppl, 1986, 5, 229 - 41 Growth polarity and cytokinesis in fission yeast: the role of the cytoskeleton; Marks J et al.; The distribution of F-actin in the fission yeast Schizosaccharomyces pombe was investigated by fluorescence microscopy using rhodamine-conjugated phalloidin . Fluorescence was seen either at the ends of the cell or at the cell equator . End staining was predominantly in the form of dots whilst equatorial actin was resolved as a filamentous band . The different staining patterns showed a close correlation with the known pattern of cell wall deposition through the cell cycle . In small, newly divided cells actin was localized at the single growing cell end whilst initiation of bipolar cell growth was coincident with the appearance of actin at both ends of the cell . As cells ceased to grow and entered cell division, a ring of actin was seen to anticipate the deposition of the septum at cytokinesis . The relationship between actin and cell wall deposition was further confirmed in three temperature-sensitive cell division cycle (cdc) mutants; cdc10, cdc11 and cdc13 . Immunofluorescence microscopy of S . pombe with an anti-tubulin antibody revealed a system of cytoplasmic microtubules extending between the cell ends . The function of these was investigated in the cold-sensitive, benomyl-resistant mutant ben4 . In cold-grown cells actin was seen to form conspicuous filamentous rings around the nucleus . The origin of these and the possible role of microtubules in the cell-cycle-dependent rearrangements of F-actin are discussed. Curr Genet, 1986, 11(2), 113 - 7 Acid phosphatase deficient mutants of Schizosaccharomyces pombe are defective in tyrosine uptake; Coddington A et al.; The uptake of tyrosine and arginine into wild type and acid phosphatase deficient mutants (pho 1) of Schizosaccharomyces pombe was investigated . All 11 pho 1-alleles tested exhibited a reduced tyrosine uptake and impaired uptake cosegregated with the lack of acid phosphatase activity . Kinetic analyses using wild type cells grown in high phosphate medium (acid phosphatase repressed) and low phosphate medium (acid phosphatase derepressed) showed staturation kinetics for tyrosine with a KM of about 2 x 10(-4) M for both media and a V of about 5 nmol min-1 mg-1 and 2 nmol min-1 mg-1 for derepressed and repressed cells respectively . The pho 1-118 strain completely lacked this saturable uptake system for tyrosine . Preliminary evidence suggests that tyrosine uptake may be via a general amino acid permease system and we conclude that mutations in the structural gene of acid phosphatase which abolish enzyme activity lead to a loss of this uptake system . In contrast to tyrosine, arginine uptake seems not to be significantly affected either by different acid phosphatase levels in wild type cells or by the pho 1-118 mutation. Curr Genet, 1986, 10(7), 509 - 14 Isolation of a novel type of mutation in the mitotic control of Schizosaccharomyces pombe whose phenotypic expression is dependent on the genetic background and nutritional environment; Ogden JE et al.; The major cell cycle control in the fission yeast Schizosaccharomyces pombe acts at entry to mitosis, and involves three previously identified genes cdc2, cdc25 and wee1 . The presence of a wee1 mutation phenotypically suppresses cdc25 mutations . This paper describes the isolation and subsequent analysis of a strain in which the suppression is reversed by the presence of a new mutation, designated win1.1 . The mutation causes a slight increase in cell size at division in most genetic backgrounds . However, when combined with a wee1 mutation and cdc25.22, the win1.1 mutation interacts strongly to generate a novel phenotype: cells are phenotypically cdc during growth on minimal medium but cdc+ when cultured on complex medium . The win1 locus is unlinked to previously identified genes involved in mitosis. Curr Genet, 1986, 10(7), 503 - 8 Transformation of Schizosaccharomyces pombe by non-homologous, unstable integration of plasmids in the genome; Wright AP et al.; In the fission yeast, Schizosaccharomyces pombe, transformation with recombinant plasmids always results in a high proportion of mitotically unstable transformants . This suggested that specialised (ARS) sequences might not be required for autonomous replication of plasmids in S . pombe, contrary to the situation in Saccharomyces cerevisiae . We have shown that specialised ARS sequences, analogous to those in S . cerevisiae, do exist in S . pombe, supporting the view that ARS elements are a general feature of eukaryotes . In addition, there is a further mechanism of plasmid maintenance which involves homologous and non-homologous integration into, and excision from the genome. Curr Genet, 1986, 10(6), 443 - 7 Genetic mapping of eleven spo genes essential for ascospore formation in the fission yeast Schizosaccharomyces pombe; Kishida M et al.; Sporulation-deficient mutants of the fission yeast Schizosaccharomyces pombe were isolated from a homothallic strain mutagenized with ethyl methanesulfonate . Complementation tests defined two new genetic loci (spo19 and spo20) essential for ascospore formation, in addition to the 18 known spo loci (Bresch et al . 1968) . A novel mapping procedure using random spore analysis prior to tetrad analysis allowed us to map 11 spo genes . Four genes (spo3, spo15, spo19 and spo20) were mapped on chromosome I, 6 genes (spo2, spo4, spo5, spo6, spo14 and spo18) on chromosome III and 1 gene (spo13) on chromosome III . Although there was no noticeable clustering of spo genes on the chromosomes, three pairs of linked genes (spo15-spo20, spo3-spo19 and spo2-spo18) were found. Curr Genet, 1986, 10(5), 365 - 70 Molecular cloning of a ribosomal protein gene from the fission yeast Schizosaccharomyces pombe; Nischt R et al.; Using the structural gene for the ribosomal protein L3 from Saccharomyces cerevisiae as a probe, we isolated a homologous fragment from genomic DNA of Schizosaccharomyces pombe . Analysis of the plasmid carrying this fragment by hybridization selection and 2D-electrophoresis revealed a 31 kDa ribosomal protein . Transformation of the vector pDB248x containing this fragment into Schizosaccharomyces pombe leads to an increased level of mRNA suggesting that we have cloned the entire and actively transcribed gene. Curr Genet, 1986, 11(2), 107 - 12 Induction of yeast DNA ligase genes in exponential and stationary phase cultures in response to DNA damaging agents; Johnson AL et al.; UV-irradiation of stationary phase cells of Saccharomyces cerevisiae and Schizosaccharomyces pombe leads to a 9-fold and 90-fold increase in transcript levels from the respective DNA ligase genes CDC9 and CDC17, whereas exponential cells show only 3-fold and 2-fold increases . Induction of CDC9 after MMS treatment and gamma-irradiation was also observed by using a CDC9-lacZ translational fusion and assaying for beta-galactosidase . Surprisingly, irradiation of S . cerevisiae induces only a 50% increase in DNA ligase itself, probably reflecting the extremely high in vivo stability of the enzyme . The UV-induction of ligase may be part of a "fail-safe" mechanism which, together with the enzyme stability, ensures adequate supplies of this essential enzyme. J Mol Evol, 1986, 23(4), 337 - 42 Examination of protein sequence homologies: III . Ribosomal protein YS25 from Saccharomyces cerevisiae and its counterparts from Schizosaccharomyces pombe, rat liver, and Escherichia coli; Otaka E et al.; The sequences of the ribosomal proteins YS25, SP-S28, RL-S21, and Ec-S6, from Saccharomyces cerevisiae, Schizosaccharomyces pombe, rat liver, and Escherichia coli, respectively, have been examined using a computer program that searches for homologous tertiary structures . Matrices of comparisons among the eukaryotic sequences show that they match each other sequentially without any internal gaps . The average values of the correlation coefficients obtained from the comparison matrices are higher for the first halves of the sequences than for the latter halves . This result suggests that the first halves of the sequences may represent a more important domain than the latter halves . The comparison matrices between the eukaryotic and bacterial sequences of ribosomal proteins, however, do not show sequentially arranged homology, though there are six well-matching segments arranged in different orders in the two types of sequences . This implies that the eukaryotic sequences of the ribosomal protein were reconstituted by two internal transpositions and six deletions of 4-12 residues each from the ancestral sequence during the divergence between bacterial and eukaryotic genes . These findings may give insight into structural and quantitative studies of evolutionary divergence between eukaryotes and prokaryotes. Gene, 1986, 47(2-3), 245 - 59 Cloning of genes related to exo-beta-glucanase production in Saccharomyces cerevisiae: characterization of an exo-beta-glucanase structural gene; Nebreda AR et al.; The EXG1 gene of Saccharomyces cerevisiae was cloned and identified by complementation of a mutant strain (exg1-2) with highly reduced extracellular exo-beta-1,3-glucanase (EXG) activity . Two recombinant plasmids containing an overlapping region of 5.2 kb were isolated from a genomic DNA library and characterized by restriction mapping . The coding region was located by subcloning the original DNA inserts in a 2.7-kb HindIII-XhoI fragment . Exg+ strains and Exg- mutants transformed with yeast multicopy plasmids containing this DNA fragment showed an EXG activity 5- to 20-fold higher than for the untransformed Exg+ wild-type (wt) strains . The overproduced EXG had the same enzymic activity on different substrates, and showed the same electrophoretic behaviour on polyacrylamide gels and identical properties upon filtration through Sephacryl S-200 as those of the main EXG from Exg+ wt strains . The EXG1 gene transformed Schizosaccharomyces pombe, yielding extracellular EXG activity which showed cross-reactivity with anti-S . cervisiae EXG antibodies . A fragment including only a part of the EXG1 region was subcloned into the integrating vector YIp5, and the resulting plasmid was used to transform an Exg+ strain . Genetic and Southern analysis of several stable Exg- transformants showed that the fragment integrated by homology with the EXG1 locus . The chromosomal DNA fragment into which the plasmid integrated has a restriction pattern identical to that of the fragment on which we had previously identified the putative EXG1 gene . Only one copy of the EXG1 gene per genome was found in several strains tested by Southern analysis . Furthermore, two additional recombinant plasmids sharing a yeast DNA fragment of about 4.1 kb, which partially complements the exg1-2 mutation but which shows no homology with the 2.7-kb fragment containing the EXG1 gene, were also identified in this study . This 4.1-kb DNA fragment does not appear to contain an extragenic suppressor and could be related in some way to EXG production in S . cerevisiae. J Mol Evol, 1986, 23(1), 41 - 51 The cloning and characterization of a RAS gene from Schizosaccharomyces pombe; Nadin-Davis SA et al.; We have cloned and determined the complete nucleotide sequence of a RAS gene from the yeast Schizosaccharomyces pombe (SP-RAS) . The putative RAS protein of 214 amino acids is encoded by two noncontiguous reading frames separated by an intron of 86 bp . The SP-RAS gene product shares extensive homology with the proteins of the Saccharomyces cerevisiae (SC), Dictyostelium, Drosophila, and human RAS genes in its N-terminal region but not in its C-terminal region . The extended C-terminal regions found in the SC-RAS genes have no counterpart in the SP-RAS gene . Thus the RAS genes of these two yeasts are structurally quite distinct . The SP-RAS sequence was expressed in vivo. Gene, 1986, 45(3), 289 - 97 The mosaic cox1 gene in the mitochondrial genome of Schizosaccharomyces pombe: minimal structural requirements and evolution of group I introns; Trinkl H et al.; The gene encoding subunit 1 of cytochrome oxidase (cox1) in the fission yeast Schizosaccharomyces pombe is polymorphic . In strain 50 it contains two group I introns with open reading frames (ORFs) in phase with the upstream exons (Lang, 1984) . In strain EF1 two additional very short group I introns which do not possess ORFs were detected by DNA sequencing . These two introns (AI2a and AI3) share distinct characteristics concerning their nucleotide sequence and secondary structure and are located at identical positions as the introns AI4 and AI5 beta, respectively, in the cox1 gene of Saccharomyces cerevisiae . The sequence homology of the cob and cox1 genes around the splice points of introns AI2a,