Hog1 kinase converts the Sko1-Cyc8-Tup1 repressor complex into an activator that recruits SAGA and SWI/SNF in response to osmotic stress

Mol Cell. 2002 Jun;9(6):1307-17. doi: 10.1016/s1097-2765(02)00557-9.


The yeast ATF/CREB repressor Sko1(Acr1) regulates genes that are induced upon hyperosmotic stress by recruiting the Cyc8(Ssn6)-Tup1 corepressor complex to target promoters. During hyperosmotic stress, Hog1 MAP kinase associates with target promoters, phosphorylates Sko1, and converts Sko1 into a transcriptional activator. Unexpectedly, Tup1 remains bound to target promoters during osmotic stress. Sko1, Hog1, and Tup1 are all important for recruitment of SAGA histone acetylase and SWI/SNF nucleosome-remodeling complexes to osmotic-inducible promoters, and both complexes are important for activation upon osmotic stress. Thus, osmotic induction involves a switch of Sko1-Cyc8-Tup1 from a repressing to an activating state in a process that is triggered by Hog1 phosphorylation. Cyc8-Tup1 is not simply a corepressor but is also involved in recruiting SWI/SNF and SAGA during the transcriptional induction process.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Basic-Leucine Zipper Transcription Factors
  • DNA-Binding Proteins / metabolism*
  • Fungal Proteins / metabolism
  • Gene Expression Regulation, Fungal
  • Mitogen-Activated Protein Kinases / metabolism*
  • Models, Genetic
  • Nuclear Proteins*
  • Osmolar Concentration*
  • Promoter Regions, Genetic
  • Repressor Proteins / metabolism*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Transcription, Genetic


  • Basic-Leucine Zipper Transcription Factors
  • CYC8 protein, S cerevisiae
  • DNA-Binding Proteins
  • Fungal Proteins
  • Nuclear Proteins
  • Repressor Proteins
  • SKO1 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • TUP1 protein, S cerevisiae
  • HOG1 protein, S cerevisiae
  • Mitogen-Activated Protein Kinases