Author ORCID Identifier

https://orcid.org/0000-0003-3788-5044

Date of Graduation

5-2019

Document Type

Dissertation (PhD)

Program Affiliation

Microbiology and Molecular Genetics

Degree Name

Doctor of Philosophy (PhD)

Advisor/Committee Chair

Kevin A. Morano

Committee Member

Michael C. Lorenz

Committee Member

Ambro van Hoof

Committee Member

Carmen W. Dessauer

Committee Member

Heidi B. Kaplan

Abstract

In eukaryotic cells, protein homeostasis and cellular fitness is promoted by the transcription factor heat shock factor 1 (HSF1) during exposure to proteotoxic stress. HSF1 controls the basal and stress-induced expression of molecular chaperones and other protective targets. Dynamic regulation of HSF1 involves the major heat shock proteins Hsp70 and Hsp90. Recent advances in the understanding of this regulatory circuit in Saccharomyces cerevisiae have shown that the Hsp70 Ssa1 acts as a sensor for some proteotoxic stresses and is capable of a direct interaction with Hsf1. This work continues to explore the complex regulatory interaction between Hsf1 and Ssa1. I found that the Ssa1 substrate binding domain recognizes Hsf1 at two distinct sites, one previously defined as the CE2 within the carboxyl-terminal transcriptional activation domain, and one within the amino-terminal activation domain. Disruption of the identified in silico Hsp70-binding sites within each regulatory element results in loss of Ssa1 association. Furthermore, loss of regulation by Ssa1 leads to global dysregulation of Hsf1 transcriptional activity that displays synergism when both sites are disrupted simultaneously. Dysregulation of Hsf1 transcriptional activity also results in survival consequences, with slow growth at optimal growth temperatures that is exacerbated during heat shock. Additionally, the activation domains of Hsf1 in the related yeast Lachancea kluyveri also associate with Hsp70, indicating that this interaction may be a conserved mechanism for regulation of Hsf1 transcriptional activity.

Keywords

Hsf1, Heat shock response, Saccharomyces cerevisiae, Hsp70, regulation, transcriptome

Available for download on Thursday, May 07, 2020

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