Stabilization of the hexasome intermediate during histone exchange by yeast SWR1 complex
Adam S B Jalal1, Paul Girvan2, Eugene Y D Chua1
1Section of Structural Biology, Department Infectious Disease, Faculty of Medicine, Imperial College London, London SW7 2AZ, UK.
Molecular Cell
|September 3, 2024
Summary
The SWR1 complex facilitates histone exchange in yeast. Cryo-EM reveals how the Swc5 subunit aids DNA unwrapping during this process, offering insights into histone exchange mechanisms.
Area of Science:
- Molecular Biology
- Structural Biology
- Epigenetics
Background:
- The SWR1 complex is crucial for replacing canonical histone H2A/H2B dimers with Htz1/H2B variants in yeast nucleosomes.
- This histone exchange is vital for regulating gene expression and chromatin structure.
Purpose of the Study:
- To elucidate the structural mechanism of histone exchange mediated by the SWR1 complex.
- To understand the role of specific subunits and intermediates in the SWR1-catalyzed reaction.
Main Methods:
- Cryo-electron microscopy (cryo-EM) was employed to determine the structure of key reaction intermediates.
- Biochemical engineering, including crosslinking of histone dimers and chaperones, was used to trap and analyze complexes.
Main Results:
- A hexasome intermediate structure revealed the Swc5 subunit's role in stabilizing DNA unwrapping from the histone core.
- Engineered crosslinks demonstrated how chaperone-histone interactions influence the exchange process.
- A trapped SWR1/hexasome complex provided structural insights into the subsequent step of histone insertion.
Conclusions:
- The study provides high-resolution structural snapshots of the SWR1 histone exchange mechanism.
- Key structural features, including the Swc5 subunit's function and chaperone interactions, are elucidated.
- These findings advance our understanding of chromatin remodeling and epigenetic regulation.
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