Lila Reddy
Pronouns: she/her
Research Mentor(s): Sethuramasundaram Pitchiaya
Research Mentor School/College/Department: Urology / Medicine
Program: UROP
Session: Session 6 (3:40pm – 4:30pm)
Authors: Lila Reddy, Joel Berends, Sethuramasundaram Pitchiaya
Abstract
Heat Shock Factor 1 (HSF1) is an evolutionarily conserved protein that regulates transcriptional responses to heat stress in almost all forms of life. More specifically, HSF1 upregulates the transcription of chaperone genes, which assist in the refolding or degradation of injured proteins. Aberrations in HSF1’s activity are associated with aging, neurodegenerative pathologies, and cancer. However, how HSF1 specifically and rapidly regulates stress-response genes amidst the vast expanse of the human genome is largely unknown. We discovered that HSF1 accumulates within membraneless nuclear compartments, called condensates, in response to heat shock, as well as a variety of other stresses (e.g. hypoxic, oxidative, osmotic and proteotoxic drugs). We hypothesize that these HSF1 condensates are sites of transcriptional activity. To test this thesis, we performed immunofluorescence assays on human U2-OS cells, a well validated human model system for stress response, to probe for HSF1 and other transcriptional modulators. To this end, U2-OS cells were either heat shocked (42º C) or propagated at normal growth temperatures (37º C). We found that CTCF, a genome organizing protein, did not localize within HSF1 condensates. Surprisingly, HSF1 colocalized with H3K27me3, a histone modification that typically denotes transcriptionally silent facultative heterochromatin, and H2K27ac, a histone modification that typically denotes transcriptional activation, within condensates upon heat shock. Our data suggests that HSF1 condensates either transition between transcriptionally active to inactive states or have distinct sub-domains. We will test this result with combined immunofluorescence of all three components and will further test our hypothesis by probing other transcriptional modulators.
