Regulation of Thermotolerance by Stress-Induced Transcription Factors in Saccharomyces cerevisiae

Abstract

The heat shock transcription factor Hsf1 and the general stress transcription factors Msn2 and Msn4 (Msn2/4) are major regulators of the heat shock response in Saccharomyces cerevisiae. Here, we show that transcriptional activation of their target genes, including HSP104, an antistress chaperone gene, is obligatory for thermotolerance. Although Hsf1 activity might be necessary before the exposure of cells to high temperature, severe heat shock induced the binding of hyperphosphorylated Hsf1 to its target promoters. However, promoter-bound, phosphorylated Hsf1 was inactive for transcription because RNA polymerase II was inactive at high temperatures. Rather, our results suggest that Hsf1 activates the transcription of most of its target genes during the recovery period following severe heat shock. This delayed upregulation by Hsf1, which would be induced by misfolded proteins that accumulate in severely heat-shocked cells, is required for the resumption of normal cell growth. In contrast, the factors Msn2/4 were not involved in the delayed upregulation of genes and were dispensable for cell growth during the recovery period, suggesting that they play a role before the exposure to high temperature. These results show that Hsf1 and Msn2/4 act differentially before and after exposure to extreme temperatures to ensure cell survival and growth.

Rtr1 Is the Saccharomyces cerevisiae Homolog of a Novel Family of RNA Polymerase II-Binding Proteins

“…Complementation of rtr1⌬ restored GAL1 induction, verifying that loss of transcriptional activity was due to loss of Rtr1 function (data not shown). Interestingly, RNAPII-but not RNAPIII-dependent gene expression appeared to be inhibited at high temperatures, as is consistent with a previous report (67). FIG.…”

Deletion of a subgroup of ribosome-related genes minimizes hypoxia-induced changes and confers hypoxia tolerance

“…Network analysis of these regulators showed that many regulators are highly connected and interact with each other genetically and biochemically ( Fig. 8) (5,18,44,59,72,80,81,88,91,95,98,106,120,123,128). Many of the regulators are components of global regulatory complexes.…”

Molecular Characterization of the Putative Transcription Factor SebA Involved in Virulence in Aspergillus fumigatus

“…As expected, most of the analyses have shown that heat shock proteins are very important for the thermotolerance, but in addition, several proteins involved in oxidative stress response, signal transduction, transcription, translation, and carbohydrate or nitrogen metabolism were observed (1,19,40). In S. cerevisiae, the heat shock response is mostly controlled by Hsf1, Msn2/Msn4, and Hac1, and targets for these transcription factors have already been identified (22,27,(63)(64)(65)(66). Upon heat shock, the A. fumigatus Hsf1 homologue has increased transcription (1,22).…”

“…In the wild-type strain, sebA transcription did not increase in the presence of H 2 O 2 (2 mM) or paraquat (10 mM) for 15 and 30 min or when the strain was exposed to increasing concentrations of KCl and sorbitol (data not shown). The transcriptional response of several A. fumigatus genes involved in the oxidative stress response (http://www.aspgd.org), including Afyap1 and Afatf1 (Afu6g09930 and Afu3g11330), which encode TFs required for resistance to oxidative stress (26,34,65), Afccp1 (Afu4g09110), which encodes a cytochrome c peroxidase (1, 34, 57), Afcat1 (Afu3g02270), which encodes a catalase (57), Afcat2 (Afu8g01670), which encodes a bifunctional catalase-peroxidase (34), afsod1 (Afu5g09240), which encodes a Cu/Zn superoxide dismutase (30,32,34,42,62), and Afusod2 (Afu4g11580), which encodes a manganese-superoxide dismutase (32,57), was assessed via real-time RT-PCR.…”