Authors: Lindquist S; Kim G
Abstract: In all organisms, mild heat pretreatments induce tolerance to high temperatures. In the yeast Saccharomyces cerevisiae, such pretreatments strongly induce heat-shock protein (Hsp) 104, and hsp104 mutations greatly reduce high-temperature survival, indicating Hsp1O4 plays a critical role in induced thermotolerance. Surprisingly, however, a heat-shock transcription factor mutation (hsf1-m3) that blocks the induction of Hsps does not block induced thermotolerance. To resolve these apparent contradictions, we reexamined Hsp expression in hsf1-m3 cells. HsplO4 was expressed at a higher basal level in this strain than in other S. cerevisiae strains. Moreover, whereas the hsf1-m3 mutation completely blocked the induction of Hsp26 by heat, it did not block the induction of Hsp1O4. HSP104 could not be deleted in hsf1-m3 cells because the expression of heat-shock factor (and the viability of the strain) requires nonsense suppression mediated by the yeast prion [PSI+], which in turn depends upon Hsp1O4. To determine whether the level of Hsp1O4 expressed in hsf1-m3 cells is sufficient for thermotolerance, we used heterologous promoters to regulate Hsp1O4 expression in other strains. In the presence of other inducible factors (with a conditioning pretreatment), low levels of Hsp1O4 are sufficient to provide full thermotolerance. More remarkably, in the absence of other inducible factors (without a pretreatment), high levels of Hsp1O4 are sufficient. We conclude that Hsp1O4 plays a central role in ameliorating heat toxicity. Because Hsp1O4 is nontoxic and highly conserved, manipulating the expression of Hsp1OO proteins provides an excellent prospect for manipulating thermotolerance in other species.
Keywords: Estradiol/pharmacology; Gene Expression/drug effects; Genotype; Heat-Shock Proteins/biosynthesis/genetics/*physiology; Hot Temperature; Mutagenesis; Saccharomyces cerevisiae/drug effects/genetics/*physiology; *Saccharomyces cerevisiae Proteins; Species Specificity|
Journal: Proceedings of the National Academy of Sciences of the United States of America Volume: 93 Issue: 11 Pages: 5301-6 Date: May 28, 1996 PMID: 8643570 |
Lindquist S, Kim G (1996) Heat-shock protein 104 expression is sufficient for thermotolerance in yeast. Proceedings of the National Academy of Sciences of the United States of America 93: 5301-6.
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