The Yeast Hsp110 Family Member, Sse1, Is an Hsp90 Cochaperone

Abstract

In eukaryotes, production of the diverse repertoire of molecular chaperones during normal growth and in response to stress is governed by the heat shock transcription factor HSF. The HSC82 and HSP82 genes, encoding isoforms of the yeast Hsp90 molecular chaperone, were recently identified as targets of the HSF carboxyl-terminal activation domain (CTA), whose expression is required for cell cycle progression during prolonged heat stress conditions. In the present study, we have identified additional target genes of the HSF CTA, which include nearly all of the heat shock-inducible members of the Hsp90 chaperone complex, demonstrating coordinate regulation of these components by HSF. Heat shock induction of SSE1, encoding a member of the Hsp110 family of heat shock proteins, was also dependent on the HSF CTA. Disruption of SSE1 along with STI1, encoding an established subunit of the Hsp90 chaperone complex, resulted in a severe synthetic growth phenotype. Sse1 associated with partially purified Hsp90 complexes and deletion of the SSE1 gene rendered cells susceptible to the Hsp90 inhibitors macbecin and geldanamycin, suggesting functional interaction between Sse1 and Hsp90. Sse1 is required for function of the glucocorticoid receptor, a model substrate of the Hsp90 chaperone machinery, and Hsp90-based repression of HSF under nonstress conditions. Taken together, these data establish Sse1 as an integral new component of the Hsp90 chaperone complex in yeast.

Conformational dynamics of the molecular chaperone Hsp90

“…Aha1 stimulates ATPase activity * p50 blocks ATPase activity and is thought to be kinase specific * Cpr6 TPR-containing and peptidy-prolyl-isomerase (Johnson et al, 2007) FKBP52 TPR-containing and peptidy-prolyl-isomerase (Riggs et al, 2003) GCUNC-45 TPR-containing that blocks progression of cycle (Chadli et al, 2006) Hop TPR-containing and scaffolds Hsp70-Hsp90 interaction * Hsp70 recruits substrates to Hsp90 * NudC CHORD-domain containing (Te et al, 2007) p23 blocks ATPase activity and traps client proteins in complex with Hsp90 * PP5 TPR-containing and phosphatase * Sse1 part of Hsp90 complex in budding yeast (Liu et al, 1999) Tah1 TPR-containing For a list of additional co-chaperones see http://www.picard.ch/downloads/Hsp90interactors.pdf * References can be found in the text.…”

Cti6 Is an Rpd3-Sin3 Histone Deacetylase-associated Protein Required for Growth under Iron-limiting Conditions in Saccharomyces cerevisiae

“…For INO1-LacZ assays 1 mM choline and 0.75 mM inositol were added to the medium. Cells were harvested and ␤-galactosidase activity was measured in permeabilized cells as previously described (29).…”

Interaction between Heat Shock Transcription Factors (HSFs) and Divergent Binding Sequences

“…The C-terminal activation domain termed AR2/CTA/CAD, but not the ScHsf1-specific N-terminal activation domain termed AR1/ NTA/AAD, is necessary for heat-and menadione-induced transcription of CUP1 (10,14,24). Deletion of AR2 also abrogates the heat shock response of several other genes containing gap-type HSEs (12). The HR-A/B region is necessary for stressinduced hyperphosphorylation of ScHsf1 and for its binding to and transcriptional activation via HSEs with three nGAAn units but not with four or more units (19).…”