title: High copies of SUM1 enhance the stability of wild-type microtubules against adverse conditions in Saccharomyces cerevisiae.
abstract: The budding yeast transcriptional repressor Sum1p binds to several promoters and recruits Hst1p, an NAD(+)-dependent histone deacetylase, at these promoters with the help of another protein Rfm1p. Hst1p causes repression of transcription by histone deacetylation of chromatin at its target promoters. In an earlier work we have shown that about 13-fold increase in Sum1p levels, brought about by expressing SUM1 from the high copy 2 micron plasmid (2 μ-SUM1), suppressed cold-sensitive growth phenotype associated with mutations in the α-tubulin gene TUB1. In this work we show that the dosage suppression is accompanied by an elevation of α-tubulin levels in mutant cells at their non-permissive growth temperature of 14°C. Further, 2 μ-SUM1 significantly rescued the benomyl-supersensitive growth phenotype of mutant cells having wild-type tubulin subunits but a deficiency in tubulin folding cofactors. Finally, wild-type 2 μ-SUM1 transformants, having no known mutation in microtubule-related genes, displayed spindle microtubules which were substantially more stable than of wild-type control cells when challenged with microtubule-depolymerizing drugs. Therefore, we conclude that high copies of Sum1p stabilize microtubules against a variety of adverse and destabilizing conditions like mutations, low temperatures and drugs.
authors.affiliation: Department of Biochemistry, Bose Institute, Kolkata 700054, India.
authors.forename: Subhash
authors.initials: S
authors.lastname: Haldar
authors.forename: Sourav
authors.initials: S
authors.lastname: Sarkar
authors.forename: Vinay
authors.initials: V
authors.lastname: Singh
authors.forename: Pratima
authors.initials: P
authors.lastname: Sinha
mesh_terms: D018628:Gene Dosage; D008870:Microtubules / Q000502:physiology* / Q000648:ultrastructure; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics* / Q000502:physiology*; D017510:Protein Folding; D012097:Repressor Proteins / Q000235:genetics* / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000502:physiology*; D013312:Stress, Physiological; D013489:Suppression, Genetic; D014404:Tubulin / Q000235:genetics / Q000378:metabolism
chemical_list: D009687:Nuclear Proteins; D012097:Repressor Proteins; C100925:SUM1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014404:Tubulin