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  • 1
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Synthesis of trehalose in the yeast Saccharomyces cerevisiae is catalysed by the trehalose-6-phosphate (Tre6P) synthase/phosphatase complex, which is composed of at least three different subunits encoded by the genes TPS1, TPS2, and TSL1. Previous studies indicated that Tps1 and Tps2 carry the catalytic activities of trehalose synthesis, namely Tre6P synthase (Tps1) and Tre6P phosphatase (Tps2), while Tsl1 was suggested to have regulatory functions. In this study two different approaches have been used to clarify the molecular composition of the trehalose synthase complex as well as the functional role of its potential subunits. Two-hybrid analyses of the in vivo interactions of Tps1, Tps2, Tsl1, and Tps3, a protein with high homology to Tsl1, revealed that both Tsl1 and Tps3 can interact with Tps1 and Tps2; the latter two proteins also interact with each other. In addition, trehalose metabolism upon heat shock was analysed in a set of 16 isogenic yeast strains carrying deletions of TPS1, TPS2, TSL1, and TPS3 in all possible combinations. These results not only confirm the previously suggested roles for Tps1 and Tps2, but also provide, for the first time, evidence that Tsl1 and Tps3 may share a common function with respect to regulation and/or structural stabilization of the Tre6P synthase/phosphatase complex in exponentially growing, heat-shocked cells.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Yeast cells show an adaptive response to a mild heat shock, resulting in thermotolerance acquisition. This is accompanied by induction of heat-shock protein (hsp) synthesis and rapid accumulation of trehalose. Genetic approaches to determine the specific role of trehalose in heat-induced thermotolerance in Saccharomyces cerevisiae have been hampered by the finding that deletion of TPS1, the gene encoding trehalose-6-phosphate synthase, causes a variety of pleiotropic effects, including inability to grow on glucose-containing media. Here, we have studied a tps1 mutant of the yeast Schizosaccharomyces pombe that reportedly has no such growth defects. We show that tps1 mutants have a serious defect in heat shock-induced acquisition of thermotolerance if conditioned at highly elevated temperatures (40–42.5°C), which, in wild-type cells, prevent hsp but not trehalose synthesis. In contrast, hsp synthesis appears to become particularly important under conditions in which trehalose synthesis is either absent (in tps1 mutant strains) or not fully induced (conditioning at moderately elevated temperatures, i.e. 35°C). In addition, pka1 mutants deficient in cAMP-dependent protein kinase were examined. Unconditioned pka1 cells had low levels of trehalose but a high basal level of thermotolerance. It was found that pka1 mutant cells, contrary to wild-type cells, accumulated large amounts of trehalose, even during a 50°C treatment. pka1 tps1 double mutants lacked this ability and showed reduced intrinsic thermotolerance, indicating a particularly important role for trehalose synthesis, which takes place during the challenging heat shock.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In the yeast Saccharomyces cerevisiae, PKA and Sch9 exert similar physiological roles in response to nutrient availability. However, their functional redundancy complicates to distinguish properly the target genes for both kinases. In this article, we analysed different phenotypic read-outs. The data unequivocally showed that both kinases act through separate signalling cascades. In addition, genome-wide expression analysis under conditions and with strains in which either PKA and/or Sch9 signalling was specifically affected, demonstrated that both kinases synergistically or oppositely regulate given gene targets. Unlike PKA, which negatively regulates stress-responsive element (STRE)- and post-diauxic shift (PDS)-driven gene expression, Sch9 appears to exert additional positive control on the Rim15-effector Gis1 to regulate PDS-driven gene expression. The data presented are consistent with a cyclic AMP (cAMP)-gating phenomenon recognized in higher eukaryotes consisting of a main gatekeeper, the protein kinase PKA, switching on or off the activities and signals transmitted through primary pathways such as, in case of yeast, the Sch9-controlled signalling route. This mechanism allows fine-tuning various nutritional responses in yeast cells, allowing them to adapt metabolism and growth appropriately.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Protein phosphorylation is estimated to affect 30% of the proteome and is a major regulatory mechanism that controls many basic cellular processes. Until recently, our biochemical understanding of protein phosphorylation on a global scale has been extremely limited; only one half of the yeast ...
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0749-503X
    Keywords: Saccharomyces cerevisiae ; chromosome I ; calnexin homologue ; CNE1 ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0749-503X
    Keywords: Saccharomyces cerevisiae ; chromosome I ; genetic mapping ; acetyl-coenzyme A synthetase ; ACS1 ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The ACS1 gene, encoding acetyl-coenzyme A synthetase, was mapped genetically at the left arm of chromosome I between pURA3 and PYK1 at 19 and 28 cM respectively. Comparison with the physical map defined a recombinational ‘hot-spot’ in this region in addition to the one between CDC24 and PYK1.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0749-503X
    Keywords: Acetyl-coenzyme A synthetase ; carbohydrate metabolism ; Saccharomyces cerevisiae ; chromosome I ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: A DNA fragment of Saccharomyces cerevisiae with high homology to the acetyl-coenzyme A (acetyl-CoA) synthetase genes of Aspergillus nidulans and Neurospora crassa has been cloned, sequenced and mapped to chromsome I. It contains an open reading frame of 2139 nucleotides, encoding a predicted gene product of 79·2 kDa. In contrast to its ascomycete homologs, there are no introns in the coding sequence. The first ATG codon of the open reading frame is in an unusual context for a translational start site, while the next ATG, 24 codons dowunstream, is in a more conventional context. Possible implications of two alternative traslational start sites for the celular lacalization of the enzyme are disussed. A stable mutant of this gene, obtained by the gene disruptiona technique, had the same low basal acitivity of acetyl-CoA synthetase as wild-type cells when grown on glucose but completely lacked the strong increase in activity upon entering the stationary phase, providing direct proof that the gene encodes an inducible acetlyl-CoA synthetase (ACSI) of yeast. As expected, the mutant was unable to grow on acetate as sole carbon source. Nevertheless, it showed normal induction os isocitrate lyase on acetate media, indicating that activity of acetyl-CoA sytheatase is dispensable for incuctionof the glyoxylate cycle in S. cerevisiae. Surprisingly, disruption of the ACSI gene did not affect growth on media containing ethanol as the sole crbon source. Demonstrating that threre are alternative pathways pathways leading to acetyl-CoA under these condintions.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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