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SMC5/6 Promotes Replication Fork Stability via Negative Regulation of the COP9 Signalosome
Michelle J Xu1, Philip W Jordan1,2
1Department of Biochemistry and Molecular Biology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD 21205, USA.
International Journal of Molecular Sciences
|January 23, 2024
Summary
The SMC5/6 complex is crucial for restarting stalled DNA replication forks in mouse cells. Loss of SMC5/6 leads to fork instability by affecting fork protection factors and MRE11 activity.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- DNA replication fork stalling is a common event during cell proliferation.
- The SMC5/6 complex is known to maintain replication fork integrity.
- The precise role of SMC5/6 in mammalian DNA replication remains unclear.
Purpose of the Study:
- To investigate the molecular mechanisms by which the SMC5/6 complex maintains replication fork integrity in mammalian cells.
- To elucidate the role of SMC5/6 in replication fork restart following stalling.
- To understand how SMC5/6 loss impacts fork protection and MRE11 activity.
Main Methods:
- Utilized the auxin-inducible degron (AID) system for acute and reversible depletion of SMC5 in mouse embryonic stem cells (mESCs).
- Employed DNA fiber techniques, small-molecule inhibition assays, and immunofluorescence microscopy.
- Investigated the interaction between SMC5/6, the COP9 signalosome (CSN), and fork protection factors.
Main Results:
- SMC5 depletion resulted in defective replication fork restart.
- Excess MRE11-mediated resection and perturbed localization of fork protection factors were observed in SMC5-depleted cells.
- SMC5/6 negatively modulates the COP9 signalosome (CSN) to promote fork protection factor localization.
Conclusions:
- SMC5/6 is essential for efficient replication fork restart in mammalian cells.
- SMC5/6 regulates CSN activity to ensure proper localization of fork protection factors.
- This regulation by SMC5/6 is critical for stabilizing replication forks and enabling restart upon stall alleviation.
Keywords:
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