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Hsf1 and Hsp70 constitute a two-component feedback loop that regulates the yeast heat shock response.

Authors
  • Krakowiak, Joanna1
  • Zheng, Xu1
  • Patel, Nikit2
  • Feder, Zoë A1
  • Anandhakumar, Jayamani2
  • Valerius, Kendra1
  • Gross, David S3
  • Khalil, Ahmad S1, 4
  • Pincus, David1
  • 1 Whitehead Institute for Biomedical Research, Cambridge, United States. , (United States)
  • 2 Department of Biomedical Engineering and Biological Design Center, Boston University, Boston, United States. , (United States)
  • 3 Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, United States. , (United States)
  • 4 Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, United States. , (United States)
Type
Published Article
Journal
eLife
Publisher
"eLife Sciences Organisation, Ltd."
Publication Date
Feb 02, 2018
Volume
7
Identifiers
DOI: 10.7554/eLife.31668
PMID: 29393852
Source
Medline
Keywords
License
Unknown

Abstract

Models for regulation of the eukaryotic heat shock response typically invoke a negative feedback loop consisting of the transcriptional activator Hsf1 and a molecular chaperone. Previously we identified Hsp70 as the chaperone responsible for Hsf1 repression and constructed a mathematical model that recapitulated the yeast heat shock response (Zheng et al., 2016). The model was based on two assumptions: dissociation of Hsp70 activates Hsf1, and transcriptional induction of Hsp70 deactivates Hsf1. Here we validate these assumptions. First, we severed the feedback loop by uncoupling Hsp70 expression from Hsf1 regulation. As predicted by the model, Hsf1 was unable to efficiently deactivate in the absence of Hsp70 transcriptional induction. Next, we mapped a discrete Hsp70 binding site on Hsf1 to a C-terminal segment known as conserved element 2 (CE2). In vitro, CE2 binds to Hsp70 with low affinity (9 µM), in agreement with model requirements. In cells, removal of CE2 resulted in increased basal Hsf1 activity and delayed deactivation during heat shock, while tandem repeats of CE2 sped up Hsf1 deactivation. Finally, we uncovered a role for the N-terminal domain of Hsf1 in negatively regulating DNA binding. These results reveal the quantitative control mechanisms underlying the heat shock response.

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