CK2-dependent inhibitory phosphorylation is relieved by Ppt1 phosphatase for the ethanol stress-specific activation of Hsf1 in Saccharomyces cerevisiae

Ethanol, the major fermentation product of Saccharomyces cerevisiae, has long been known as an inducer of heat shock response, but the underlying mechanisms by which ethanol activates heat shock transcription factor (HSF) are not well understood. We demonstrate that CK2-dependent phosphorylation on S608 is an ethanol stress-specific repression mechanism of Hsf1, which does not affect the basal or heat-induced activity of Hsf1. This repression is relieved by dephosphorylation by Ppt1 which directly interacts with Hsf1 via its tetratricopeptide repeat (TPR) domain. In response to ethanol stress, PPT1 deletion and CK2 overexpression exert synergistic inhibitory effects on Hsf1 activation, whereas Hsf1(S608A) mutant shows enhanced activation. Therefore, regulation of the Hsf1 S608 phosphorylation status by reciprocal actions of CK2 and Ppt1 might play an important role to determine Hsf1 sensitivity towards ethanol stress.