Complex regulation of the yeast heat shock transcription factor.
The yeast heat shock transcription factor (HSF) is regulated by posttranslational modification. Heat and superoxide can induce the conformational change associated with the heat shock response. Interaction between HSF and the chaperone hsp70 is also thought to play a role in HSF regulation. Here, we show that the Ssb1/2p member of the hsp70 family can form a stable, ATP-sensitive complex with HSF-a surprising finding because Ssb1/2p is not induced by heat shock. Phosphorylation and the assembly of HSF into larger, ATP-sensitive complexes both occur when HSF activity decreases, whether during adaptation to a raised temperature or during growth at low glucose concentrations. These larger HSF complexes also form during recovery from heat shock. However, if HSF is assembled into ATP-sensitive complexes (during growth at a low glucose concentration), heat shock does not stimulate the dissociation of the complexes. Nor does induction of the conformational change induce their dissociation. Modulation of the in vivo concentrations of the SSA and SSB proteins by deletion or overexpression affects HSF activity in a manner that is consistent with these findings and suggests the model that the SSA and SSB proteins perform distinct roles in the regulation of HSF activity.
Bonner
J J
JJ
Department of Biology, Indiana University, Bloomington, Indiana 47405-3700, USA. jbonner@bio.indiana.edu
Carlson
T
T
Fackenthal
D L
DL
Paddock
D
D
Storey
K
K
Lea
K
K
D004268:DNA-Binding Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D018869:Heat-Shock Response; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; D013481:Superoxides / Q000494:pharmacology; D014157:Transcription Factors / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D015003:Yeasts / Q000235:genetics / Q000378:metabolism / Q000502:physiology
D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C067168:HSF1 protein, S cerevisiae; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C095192:SSB1 protein, S cerevisiae; C101143:SSB2 protein, S pombe; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; D014157:Transcription Factors; D013481:Superoxides