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The Heat Shock Response as a Condensate Cascade.
1Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL, United States.
Journal of Molecular Biology
|June 7, 2024
Summary
The heat shock response (HSR) is activated by adaptive condensates, not toxic aggregates, in yeast. This reveals a new model where molecular chaperones regulate HSR gene expression through a condensate cascade.
Area of Science:
- Cellular Biology
- Molecular Biology
- Biophysics
Background:
- The heat shock response (HSR) is a critical cellular defense mechanism involving molecular chaperones.
- Traditionally, the HSR was thought to be triggered by toxic protein aggregates.
- Recent studies propose a novel regulatory role for the HSR in yeast.
Purpose of the Study:
- To investigate the physiological triggers of the HSR in yeast.
- To elucidate the role of adaptive biomolecular condensates in HSR activation.
- To propose a new model for HSR regulation based on chaperone activity and condensate formation.
Main Methods:
- Yeast genetics and microscopy to observe condensate formation and HSR gene expression.
- Biochemical assays to analyze chaperone interactions with Hsf1 and oRPs.
- Mathematical modeling to understand the dynamics of the HSR feedback loop.
Main Results:
- Adaptive biomolecular condensates, not toxic aggregates, were identified as physiological activators of the HSR.
- These condensates sequester chaperones (Sis1, Hsp70), releasing the transcription factor Hsf1.
- Released Hsf1 forms transcriptional condensates, driving high expression of HSR genes, establishing a negative feedback loop embedded in system biophysics.
Conclusions:
- The HSR in yeast is physiologically activated by adaptive condensates.
- A novel 'condensate cascade' model is proposed, where localized chaperone activity transmits information.
- This mechanism offers new insights into chaperone regulation and cellular stress responses relevant to aging and disease.
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