Stimuli that induce a yeast heat shock gene fused to beta-galactosidase.

Saccharomyces cerevisiae contain a multigene family related to the Drosophila heat shock gene hsp70. Two members of this family, YG100 and YG101, have been previously characterized (Ingolia et al., Mol. Cell. Biol. 2:1388-1398, 1982), and only YG100 was found to have elevated levels of transcription after heat shock. The yeast hsp70 genes contained on YG100 and YG101 were truncated and fused to the Escherichia coli lacZ gene contained on pMC1587 (Casadaban et al., Methods Enzymol. 100:283-308, 1983). The resulting plasmids directed synthesis of the beta-galactosidase gene as measured by in vitro enzyme assays and by colorimetric assays on plates. The expression level from the YG101 gene was constant under all the conditions tested, whereas expression driven by the YG100 gene could be induced over 50-fold. Other stimuli besides heat, including recovery from anoxia and high cell density, were found to strongly induce YG100 gene expression. Most physical and chemical stimuli tested, including UV irradiation, zymolyase treatment, and ethanol, did not stimulate expression of this heat shock gene.