Hog1 kinase converts the Sko1-Cyc8-Tup1 repressor complex into an activator that recruits SAGA and SWI/SNF in response to osmotic stress.
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.
Proft
Markus
M
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
Struhl
Kevin
K
D050976:Basic-Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008957:Models, Genetic; D009687:Nuclear Proteins; D009994:Osmolar Concentration; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
D050976:Basic-Leucine Zipper Transcription Factors; C065455:CYC8 protein, S cerevisiae; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D009687:Nuclear Proteins; D012097:Repressor Proteins; C077832:SKO1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C066502:TUP1 protein, S cerevisiae; C088589:HOG1 protein, S cerevisiae; D020928:Mitogen-Activated Protein Kinases