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  • 1
    ISSN: 1432-0983
    Keywords: Yeast ; Mitochondria ; Aminoacyl-tRNA synthetase ; RNA splicing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The mitochondrial leucyl-tRNA synthetase (mLRS) of Saccharomyces cerevisiae is involved in both mitochondrial protein synthesis and pre-mRNA splicing. We have created mutations in the regions HIGH, GWD and KMSKS, which are involved in ATP-, amino acid-and tRNA-binding respectively, and which have been conserved in the evolution of group I tRNA synthetases. The mutants GRD and NMSKS have no discernible phenotype. The mutants AWD and ARD act as null alleles and lead to the production of 100% cytoplasmic petites. The mutants HIGN, NIGH and KMSNS are unable to grown on glycerol even in the presence of an intronless mitochondrial genome and accumulate petites to a greater extent than the wild-type but less than 40%. Experiments with an imported bI4 maturase indicate that the lesion in these mutations primarily affects the synthetase and not the splicing functions.
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  • 2
    ISSN: 1617-4623
    Keywords: Aminoacyl-tRNA synthetase ; RNA splicing ; Group I introns ; RNA maturase ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The Saccharomyces cerevisiae nuclear gene NAM2 codes for mitochondrial leucyl-tRNA synthetase (mLRS). Herbert et al. (1988, EMBO J 7:473–483) proposed that this protein is involved in mitochondrial RNA splicing. Here we present the construction and analyses of nine mutations obtained by creating two-codon insertions within the NAM2 gene. Three of these prevent respiration while maintaining the mitochondrial genome. These three mutants: (1) display in vitro a mLRS activity ranging from 0%–50% that of the wild type: (2) allow in vivo the synthesis of several mitochondrially encoded proteins; (3) prevent the synthesis of the COXII protein but not of its mRNA; (4) abolish the splicing of the group I introns bI4 and aI4; and (5) affect significantly the excision of the group I introns bI2, bI3 and aI3. Importation of the bI4 maturase from the cytoplasm into mitochondria in a nam2 − mutant strain does not restore the excision of the introns bI4 and aI4 implying that the splicing deficiency does not result from the absence of the bI4 maturase. We conclude that the mLRS is a splicing factor essential for the excision of the group I introns bI4 and aI4 and probably important for the excision of other group I introns.
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  • 3
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Cell cycle ; Bud site selection ; Guanine exchange factor ; Ras
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Guanine Exchange Factor (GEF) activity for Ras proteins has been associated with a conserved domain in Cdc25p, Sdc25p in Saccharomyces cerevisiae and several other proteins recently found in other eukaryotes. We have assessed the structure-function relationships between three different members of this family in S. cerevisiae, Cdc25p, Sdc25p and Bud5p. Cdc25p controls the Ras pathway, whereas Bud5p controls bud site localization. We demonstrate that the GEF domain of Sdc25p is closely related to that of Cdc25p. We first constructed a thermosensitive allele of SDC25 by specifically altering amino acid positions known to be changed in the cdc25-1 mutation. Secondly, we constructed three chimeric genes from CDC25 and SDC25, the products of which are as active in the Ras pathway as are the wild-type proteins. In contrast, similar chimeras made between CDC25 and BUD5 lead to proteins that are inactive both in the Ras and budding control pathways. This difference in the ability of chimeric proteins to retain activity allows us to define two subclasses of structurally different GEFs: Cdc25p and Sdc25p are Ras-specific GEFs, and Bud5p is a putative GEF for the Rsr1/Bud1 Rap-like protein.
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  • 4
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Translation ; Splicing ; Paromomycin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The MSS51 gene product has been previously shown to be involved in the splicing of the mitochondrial pre-mRNA of cytochrome oxidase subunit I (COX1). We show here that it is specifically required for the translation of the COX1 mRNA. Furthermore, the paromomycin-resistance mutation (P inf454 supR ) which affects the 15 S mitoribosomal RNA, interferes, directly or indirectly, with the action of the MSS51 gene product. Possible roles of the MSS51 protein on the excision of COX1 introns are discussed.
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  • 5
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Cell cycle ; Proline ; DNA sequencing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We report here the isolation of temperature-sensitive mutants of the yeast Saccharomyces cerevisiae which exhibit cdc phenotypes. The recessive mutations defined four complementation groups, named ore1, ore2, ore3 and ore4. At the non-permissive temperature, strains bearing these mutations arrested in the G1 phase of the cell cycle. The wild-type allele of the gene altered in ore2 mutants was cloned. The nucleotide sequence of a fragment which can complement the mutation showed the presence of an open reading frame capable of encoding a protein with 286 amino acid residues. The deduced amino acid sequence showed 25% identity with that of the Escherichia coli Δ1-pyrroline-5-carboxylate reductase, an enzyme of the pathway for the biosynthesis of proline. The ore2 mutants, correspondingly, were found to be capable of growing at the non-permissive temperature on a synthetic medium supplemented with proline. In addition, the chromosomal location of the gene and its restriction map were compatible with those previously reported for the PRO3 gene which encodes the S. cerevisiae Δ1-pyrroline-5-carboxylate reductase.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 6 (1990), S. 271-297 
    ISSN: 0749-503X
    Keywords: Yeast ; DNA-binding proteins ; transcription regulation ; RNA polymerase B ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
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  • 7
    ISSN: 0749-503X
    Keywords: RVS161 gene ; Saccharomyces cerevisiae ; stationary phase entry ; viability loss ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: In yeast, nutrient starvation leads to entry into stationary phase. Mutants that do not respond properly to starvation conditons have been isolated in Saccharomyces cerevisiae. Among them the rvs161 mutant (RVS for Reduced Viability upon Starvation) is sensitive to carbon, nitrogen and sulphur starvation. When these nutrients are depleted in the medium, mutant cells show cellular viability loss with morphological changes. The mutation rvs161-1 is very pleiotropic, and besides the defects in stationary phase entry, the mutant strain presents other alterations: sensitivity to high salt concentrations, hypersensitivity to amino acid analogs, no growth on lactate or acetate medium. The addition of salts or amino acid analogs leads to the same morphological defects observed in starved cells, suggesting that the gene could be implicated mainly in the control of cellular viability. The gene RVS161 was cloned; it codes for a 30,252 daltons protein. No homology was detected with the proteins contained in the databases. Moreover, Southern analysis revealed the presence of other sequences homologous to the RVS161 gene in the yeast genome.
    Additional Material: 6 Ill.
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  • 8
    ISSN: 0749-503X
    Keywords: Chromosome III ; Saccharomyces cerevisiae ; mating type ; HML ; BUD5 ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: This paper reports the DNA sequence of a segment of 9·8 kb of the chromosome III. The sequenced DNA contains the MATα locus. The new sequence of the MATα locus differs from the previously reported sequence by six modifications in the W segment. We have found the same modifications in the HML locus. The corrected sequence contains, in HML, an open reading frame (ORF) of 190 codons which ends at the border between the W segment and the flanking DNA. In the MAT locus, this ORF extends in the flanking DNA up to 538 codons. This ORF corresponds to a gene independently identified as BUD5 (Chant et al., 1991). This gene presents homologies with the exchange factors SDC25 and CDC25. A large ORF of 1399 codons is found on the opposite side of MATα (toward the telomere). This ORF corresponds to a new gene YCR724. Next to this gene is a small ORF, YCR725, of 127 codons. The localization of this fragment on chromosome III, originally supposed to be distal from the MAT locus based on genetic distance, illustrates variation in recombination frequency along the chromosome and suggests the existence of hot spots of recombination between MAT and the THR4 locus.
    Additional Material: 5 Ill.
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  • 9
    ISSN: 0749-503X
    Keywords: Yeast ; genome ; ribosomal protein L21 ; RIM2 ; ATP carrier ; MSI1 ; IRA1 ; GAP ; PGI1 ; glycolytic genes ; leucine zipper ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: We report the DNA sequence of an 8 kb segment localized on the right arm of chromosome II from Saccharomyces cerevisiae. The sequence reveals the presence of eight open reading frames (ORFs). Three of them, YBR1402, YBR1405 and YBR1406 are previously sequenced genes, respectively the RIM2 (replication in mitochondria), MSI1 (multicopy suppressor of IRA1 gene) and PGI1 (phosphoglucoisomerase) genes. The predicted product of the ORF YBR1401 could be the putative yeast ribosomal protein L21. A new essential gene, YBR1403, has been identified by disruption; it possesses a leucine zipper motif.
    Additional Material: 6 Ill.
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  • 10
    ISSN: 0749-503X
    Keywords: Yeast ; genome ; KRE2/MNT1 ; KTR1 ; KTR2 ; BEM1 ; BUD5 ; CDC24 ; TUP1 ; PRP4 ; MSI1 ; STE4 ; CDC4 ; dTAFII80 ; transducin ; G-β subunit ; WD-40 repeat ; SH3 domain ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: This paper reports the DNA sequence and analysis of an 11·7 kb segment localized on the right arm of Saccharomyces cerevisiae chromosome II. This fragment contains one incomplete and five long and non-overlapping open reading frames (ORFs) designated from centromere to telomere-proximal side as: YBR1406, 1409, 1410, 1411, 1412 and 1413. YBR1406 corresponds to the 5′ end to PGI1 encoding phosphoglucoisomerase. YBR1410 encodes a polypeptide of 798 amino acids whose C terminus contains five repeats (WD-40 repeat) similar to those found in the β-subunits of G proteins and different yeast proteins such as Tup1, Prp4 and Cdc4. The higher similarity score is obtained with dTAFII80, a component of the RNA polymerase II transcriptional complex TFIID. YBR1411 encodes a polypeptide of 464 amino acids which belongs to the family of α-mannosyltransferases: KRE2/MNT1, KTR1, KTR2, YUR1 and the product of previously sequenced ORF YBR1445. YBR1412 corresponds to BEM1. The two ORFs, YBR1409 and YBR1413, which do not exhibit significant similarity with any known coding sequences, define new genes. The sequence has been deposited in the EMBL Data Library under Accession Number Z21487.
    Additional Material: 4 Ill.
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