Stress induction of HSP30, the plasma membrane heat shock protein gene of Saccharomyces cerevisiae, appears not to use known stress-regulated transcription factors.

More than one transcription factor contributes to the Saccharomyces cerevisiae heat shock response. Many genes are induced through the activation of heat shock factor (Hsf1), a protein that is constitutively bound to heat shock promoter elements (HSEs). Other genes are switched on by Msn2/Msn4-dependent activation of a quite separate promoter element (the stress response element, STRE). While Hsf directs gene activation mainly in response to heat stress, STRE-directed transcription is stimulated not only by heat but also by several other stresses, starvation included. HSP30, encoding the plasma membrane heat shock protein, is shown in this study to be activated by several stresses. It is most strongly induced with heat shock, ethanol and weak organic acid exposure. The HSP30 promoter has no good agreement to the HSE consensus and its stress activation is unaffected by a mutation (hsf1-m3) that causes defective heat shock activation of Hsf1-dependent genes. Activation of HSP30 occurs with some, but not all, STRE-inducing stresses and is largely unaffected either by loss of the Msn2/Msn4 transcription factors or with mutation of all STRE-like consensus sequences of the promoter. Stress activation of HSP30 appears therefore to involve as yet unidentified components of the yeast transcriptional apparatus.