Misfolded proteins are competent to mediate a subset of the responses to heat shock in Saccharomyces cerevisiae.
Cells may sense heat shock via the accumulation of thermally misfolded proteins. To explore this possibility, we determined the effect of protein misfolding on gene expression in the absence of temperature changes. The imino acid analog azetidine-2-carboxylic acid (AZC) is incorporated into protein competitively with proline and causes reduced thermal stability or misfolding. We found that adding AZC to yeast at sublethal concentrations sufficient to arrest proliferation selectively induced expression of heat shock factor-regulated genes to a maximum of 27-fold and that these inductions were dependent on heat shock factor. AZC treatment also selectively repressed expression of the ribosomal protein genes, another heat shock factor-dependent process, to a maximum of 20-fold. AZC treatment thus strongly and selectively activates heat shock factor. AZC treatment causes this activation by misfolding proteins. Induction of HSP42 by AZC treatment required protein synthesis; treatment with ethanol, which can also misfold proteins, activated heat shock factor, but treatment with canavanine, an arginine analog less potent than AZC at misfolding proteins, did not. However, misfolded proteins did not strongly induce the stress response element regulon. We conclude that misfolded proteins are competent to specifically trigger activation of heat shock factor in response to heat shock.
Trotter
Eleanor W
EW
Division of Molecular Genetics, Faculty of Biomedical and Life Sciences, University of Glasgow, Glasgow G11 6NU, United Kingdom.
Kao
Camilla M-F
CM
Berenfeld
Ludmilla
L
Botstein
David
D
Petsko
Gregory A
GA
Gray
Joseph V
JV
D001383:Azetidinecarboxylic Acid / Q000494:pharmacology*; D002172:Canavanine / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D000431:Ethanol / Q000494:pharmacology; D005786:Gene Expression Regulation; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D018869:Heat-Shock Response; D020411:Oligonucleotide Array Sequence Analysis; D017510:Protein Folding; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D018085:Regulon / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
D004268:DNA-Binding Proteins; C067168:HSF1 protein, S cerevisiae; D006360:Heat-Shock Proteins; D011500:Protein Synthesis Inhibitors; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D002172:Canavanine; D000431:Ethanol; D001383:Azetidinecarboxylic Acid; D003513:Cycloheximide