Yeast Whi2 and Psr1-phosphatase form a complex and regulate STRE-mediated gene expression.
BACKGROUND
In response to various stressful situations, including diauxic conditions, the Msn2 and Msn4 transcription factors induce STRE-mediated gene expression of many stress responsive genes in Saccharomyces cerevisiae. This is called the general stress response. The whi2 cells in the stationary phase are smaller than wild-type cells.


RESULTS
Here we demonstrate that STRE-mediated gene expression in whi2 cells is reduced to half of that in the wild-type cells under various stress conditions. It is also delayed for several hours when the mutant cells enter the stationary phase. Using the two-hybrid system, we isolated a WHI2-interacting gene, PSR1, which is one of the redundant genes encoding plasma membrane phosphatases. whi2 and psr1 psr2 mutants had similar phenotypes, including reduced STRE-mediated gene expression, higher sensitivity to sodium ions and heat shock, and hyper-phosphorylation of Msn2. The phosphatase activity of Psr1 was necessary for the full activation of STRE-mediated gene expression. Furthermore, both Psr1 and Msn2 were co-immunoprecipitated with Whi2.


CONCLUSIONS
Thus, Whi2 and its binding partner, Psr1-phosphatase, are required for a full activation of the general stress response, possibly through the dephosphorylation of Msn2. These results may explain why stationary phase whi2 cells are small.
Kaida
Daisuke
D
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Japan.
Yashiroda
Hideki
H
Toh-e
Akio
A
Kikuchi
Yoshiko
Y
D056850:Cyclin-Dependent Kinase 8; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal / Q000502:physiology*; D008565:Membrane Proteins; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D015003:Yeasts
D004268:DNA-Binding Proteins; C081935:MSN2 protein, S cerevisiae; D008565:Membrane Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; C470937:Whi2 protein, S cerevisiae; D056850:Cyclin-Dependent Kinase 8; D018844:Cyclin-Dependent Kinases; C498309:SSN3 protein, S cerevisiae; C411891:PSR2 protein, S cerevisiae; C411890:PSR1 protein, S cerevisiae; D010749:Phosphoprotein Phosphatases