Leveraging HSF1 chemical-genetic tools to elucidate mechanisms of proteostasis

Maintenance of protein function depends on an extensive network of chaperones, quality control factors, and trafficking mechanisms collectively termed the proteostasis network. This network assists folding and maintains optimal protein localization and concentration. While the components and organization of this network are generally well-established, our understanding of how protein folding problems are identified, how the network components integrate to successfully address challenges, and which components of the proteostasis network can solve what types of biophysical issues remains immature. Cytosolic proteostasis is dynamically regulated by the master transcriptional regulator Heat Shock Factor 1 (HSF1), which induces expression of cytosolic chaperones in response to proteotoxic stressors. Previous work in our lab enabled precision regulation of HSF1 activity through constitutively active or constitutively dominant-negative variants. My graduate work has focused on applying these HSF1 chemical-genetic tools to approach various problems in the field of metazoan proteostasis. First, I examined the interplay between stress response pathways regulating chaperone expression and post-translational modification by the small ubiquitin like modifier SUMO2/3. This work lead to the identification of a critical role in the communication between the heat shock response and protein SUMOylation throughout the stress response. Moreover, I identify a novel role for SUMO2/3 conjugation as a rapid response to prevent protein aggregation during initial proteotoxic stress. Next, I used deep-mutational scanning to identify HSF1 as a critical non-oncogenic component capable of tuning fitness of dominant-negative mutations within the oncogene tumor protein 53 (TP53). Within the context of basal temperatures, the impact of HSF1 activation was beneficial and supportive of destabilizing mutations within the DNA-binding domain. I also discovered the unexpectedly opposing impacts of HSF1 on client mutational tolerance at permissive versus restrictive temperatures, revealing that the role of HSF1 in supporting or inhibiting TP53 mutations is environment dependent. Altogether, my results highlight the multifaceted roles of HSF1 in addressing client proteostasis.

Name thesis:degree_name

Doctoral

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Chemistry

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2022

Author dc:creator

• Sebastian, Rebecca Michelle

Advisor dc:contributor.advisor

• Shoulders, Matthew D.

Statement dc:rights

• In Copyright - Educational Use Permitted
• Copyright MIT

Licence dc:rights.uri

• http://rightsstatements.org/page/InC-EDU/1.0/

Handle dc:identifier.uri

https://hdl.handle.net/1721.1/145175

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/145175