Comparative interactomes of HSF1 in stress and disease reveal a role for CTCF in HSF1-mediated gene regulation

Abstract

Heat Shock Transcription Factor 1 (HSF1) orchestrates cellular stress protection by activating or repressing gene transcription in response to protein misfolding, oncogenic cell proliferation and other environmental stresses. HSF1 is tightly regulated via intramolecular repressive interactions, post-translational modifications, and protein-protein interactions. How these HSF1 regulatory protein interactions are altered in response to acute and chronic stress is largely unknown. To elucidate the profile of HSF1 protein interactions under normal growth, chronic and acutely stressful conditions, quantitative proteomics studies identified interacting proteins in the response to heat shock or in the presence of a poly-glutamine aggregation protein cell-based model of Huntington’s Disease. These studies identified distinct protein interaction partners of HSF1 as well as changes in the magnitude of shared interactions as a function of each stressful condition. Several novel HSF1-interacting proteins were identified that encompass a wide variety of cellular functions, including roles in DNA repair, mRNA processing, regulation of RNA polymerase II and others. One HSF1 partner, CTCF, interacted with HSF1 in a stress-inducible manner and functions in repression of specific HSF1 target genes. Understanding how HSF1 regulates gene repression is a crucial question, given the dysregulation of HSF1 target genes in both cancer and neurodegeration. These studies expand our understanding of HSF1-mediated gene repression and provide key insights into HSF1 regulation via protein-protein interactions.

HSF1 Can Prevent Inflammation following Heat Shock by Inhibiting the Excessive Activation of the ATF3 and JUN&FOS Genes

“…This is in line with a previous report that showed an involvement HSF1 in the induction of RNA-producing enhancers across the whole genome, but also the recruitment of HSF1 in CTCF-rich, non-transcribed chromatin [ 32 ], suggesting that interactions between HSF1 and CTCF are possible. Indeed, such interactions were later documented [ 33 ]. We also showed that HSF1 is likely to interact with CTCF in MCF7 cells (as assessed by the proximity ligation assay) and the number of interactions increased significantly after heat shock treatment ( Figure 3 B).…”

“…It was previously suggested that HSF1 may be involved in remodeling 3D chromatin architecture in response to temperature stress [ 49 ] and recruited into CTCF-occupied, non-transcribed chromatin [ 32 ]. We showed here the interaction of HSF1 with CTCF, a known regulator of chromatin architecture that was proposed to act in repressing specific HSF1 target genes [ 33 ]. This indicates that HSF1 may regulate transcription directly (by binding to the promoters) and indirectly by participating in chromatin organization.…”

An Important Role for RPRD1B in the Heat Shock Response

“…We note that RPRD1B function in the HS response is unlikely to be due to a direct interaction with HSF1. Indeed, several proteomic studies have established the HSF1 interactome, and RPRD1B was not identified as a partner in these experiments ( Burchfiel et al, 2021 ; Smith et al, 2022 ; Takii et al, 2019 ; Zhang et al, 2019 ). Furthermore, HSF1 appears to be normally activated in cells depleted for RPRD1B.…”

Kinases and Their Potential as Therapeutic Targets in Huntington’s Disease

“…Several HSPs are downregulated in cells and mouse models of HD, which is known to contribute to mtHTT aggregation [138,153,154]. HSF1 depletion has also been reported in several cell and mouse models of HD, in human iPSCs derived from patienetse with HD differentiated into MSN-like cells, and in human postmortem striatum from pateinets with HD [138,[155][156][157][158]. Initial studies proposed that down-regulation of HSPs in HD was facilitated by mtHTT-mediated changes in chromatin remodeling [153].…”