Identification of Tup1 and Cyc8 mutations defective in the responses to osmotic stress

Biochem Biophys Res Commun. 2008 Mar 28;368(1):50-5. doi: 10.1016/j.bbrc.2008.01.033. Epub 2008 Jan 15.


In the yeast Saccharomyces cerevisiae, Tup1, in association with Cyc8 (Ssn6), functions as a general transcriptional corepressor. This repression is mediated by recruitment of the Tup1-Cyc8 complex to target promoters through sequence-specific DNA-binding proteins such as Sko1, which mediates the HOG pathway-dependent regulation. We identified tup1 and cyc8 mutant alleles as the suppressor of osmo-sensitivity of the hog1Delta strain. In these mutants, although the expression of the genes under the control of DNA-binding proteins other than Sko1 was apparently normal, the Sko1-regulated genes GRE2 and AHP1 were derepressed under non-stress conditions, suggesting that the Tup1 and Cyc8 mutant proteins were specifically defective in the repression of the Sko1-dependent genes. Chromatin immunoprecipitation analyses of the GRE2 promoter in the mutants demonstrated that the Sko1-Tup1-Cyc8 complex was localized to the promoter, together with Gcn5/SAGA, suggesting that the erroneous recruitment of SAGA to the promoter led to the derepression.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alleles
  • Basic-Leucine Zipper Transcription Factors / genetics
  • Basic-Leucine Zipper Transcription Factors / metabolism
  • Calcium / metabolism
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Gene Expression Regulation, Fungal / genetics
  • Histone Acetyltransferases / genetics
  • Histone Acetyltransferases / metabolism
  • Mitogen-Activated Protein Kinases / deficiency
  • Mitogen-Activated Protein Kinases / genetics
  • Mitogen-Activated Protein Kinases / metabolism
  • Mutation / genetics
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Osmotic Pressure
  • Oxidoreductases / genetics
  • Oxidoreductases / metabolism
  • Promoter Regions, Genetic / genetics
  • Protein Binding
  • Repressor Proteins / genetics
  • Repressor Proteins / metabolism*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Sensitivity and Specificity


  • Basic-Leucine Zipper Transcription Factors
  • CYC8 protein, S cerevisiae
  • DNA-Binding Proteins
  • Nuclear Proteins
  • Repressor Proteins
  • SKO1 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • TUP1 protein, S cerevisiae
  • Oxidoreductases
  • GRE2 protein, S cerevisiae
  • GCN5 protein, S cerevisiae
  • Histone Acetyltransferases
  • HOG1 protein, S cerevisiae
  • Mitogen-Activated Protein Kinases
  • Calcium