9 The Heat-shock Response of Saccharomyces cerevisiae

Abstract

I. INTRODUCTION
A nearly universal response of organisms to an increase in temperature or other stresses is the induction of a set of proteins referred to as heat-shock or stress proteins (Hsps) (for review, see Lindquist and Craig 1988). Saccharomyces cerevisiae exhibits such a response (Miller et al. 1979; McAlister and Finkelstein 1980a). In the laboratory, the heat-shock response is most commonly induced in yeast by transferring cultures growing at 23°C to 37°C or 39°C (Nicolet and Craig 1990). The heat-shock response occurs in both rich and defined media containing a variety of carbon sources. A number of other stresses, such as high concentrations of ethanol or amino acid analogs, induce all or a subset of Hsps. However, a thorough analysis of the magnitude of induction of each Hsp with a series of inducers has not been carried out.

The induction of Hsps is primarily due to a rapid increase in transcription (Finkelstein et al. 1982; Plesset et al. 1982b). In general, both the level of Hsp mRNAs and the rate of Hsp synthesis peak between 10 and 20 minutes after temperature upshift (Miller et al. 1982; Werner-Washburne et al. 1989). In contrast, the synthesis of many proteins (300 out of 500 analyzed in one study; Miller et al. 1982) transiently decreases after a heat shock. This decrease is mainly due to the cessation of RNA synthesis and degradation of preexisiting mRNA (Lindquist 1981; Plesset et al. 1982b). There may be a translational component to the regulation as well. Some...