Linda Rubio Research
The Heat Shock Response (HSR) is a universal response of eukaryotes to proteotoxic conditions. The master regulator of this response is a transcription factor termed Heat Shock Factor 1 (Hsf1). In Saccharomyces cerevisiae (budding yeast), Hsf1 is known to be activated by different environmental stresses including heat, ethanol, osmotic stress, and glucose starvation. Nonetheless, mechanisms underlying Hsf1 activation have typically been studied only under thermal stress conditions. Scant information exists on the mechanism by which ethanol elicits the transcriptional activation of Hsf1-regulated Heat Shock Protein (HSP) genes. Previous work from our lab has shown that thermal stress leads to Hsf1-dependent restructuring of the yeast genome (Chowdhary et al, MCB 2018). Whether this type of restructuring occurs in response to other stresses is unknown. My interests are to understand the mechanisms underlying HSP gene activation in response to ethanol stress, as well as to test the existence of intra- and inter- chromosomal interactions during ethanol stress. Recent work from our lab has suggested that under thermal stress, Hsf1-GFP transiently forms puncta structures that correlate with Hsf1’s transcriptionally active state (Chowdhary et al, submitted). Following cell exposure to ethanol, I have found that Hsf1-GFP assembles into puncta structures that form and dissolve with similar kinetics, pointing to the possibility that Hsf1 drives HSP gene transcription and 3D genome restructuring under heat and ethanol in the same fashion. Yet my initial work suggests that despite similar kinetics of Hsf1 occupancy under thermal and ethanol stresses, kinetics of RNA Pol II occupancy of HSP genes seem to differ. Therefore, although Hsf1 is activated with similar kinetics in response to thermal and ethanol stress, different pathways may be utilized to elicit transcription of Hsf1-target genes.
Hsf1 puncta formation and dissolution kinetics are similar under thermal and ethanol stresses.
Hsf1-GFP is present in a diffuse state inside the yeast nucleus under normal growth conditions. Upon exposure to thermal stress (38°C), Hsf1-GFP rapidly forms puncta structures. These start to dissolve after 30 min despite constant exposure to heat, leading to a diffuse intra-nuclear distribution of Hsf1-GFP. Similarly, exposure to 8.5% ethanol stress (at 24°C) induces rapid and evanescent Hsf1-GFP puncta formation.