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RNF4 Regulates the BLM Helicase in Recovery From Replication Fork Collapse
Nathan Ellis1, Jianmei Zhu2, Mary K Yagle1
1University of Arizona Cancer Center, University of Arizona, Tucson, AZ, United States.
Frontiers in Genetics
|December 6, 2021
Summary
The SUMO-targeted ubiquitin E3 ligase RNF4 is crucial for restarting DNA replication after stress. It removes sumoylated Bloom syndrome helicase (BLM) from stalled replication forks, enabling DNA synthesis resumption.
Area of Science:
- Cellular Biology
- Molecular Biology
- Genetics
Background:
- Sumoylation enhances responses to DNA replication stress.
- RNF4 (a SUMO-targeted ubiquitin E3 ligase) regulates these responses by ubiquitylating sumoylated DNA damage response factors.
- The precise targets and functions of RNF4 in replication stress are not fully understood.
Purpose of the Study:
- To investigate the role of RNF4 in DNA replication restart following hydroxyurea (HU)-induced replication stress.
- To identify RNF4 targets and understand their functional consequences during replication stress.
- To elucidate the mechanism by which RNF4 facilitates replication recovery.
Main Methods:
- DNA fiber assays to assess DNA replication origin firing.
- Analysis of DNA double-strand break (DSB) recognition and repair.
- Depletion studies (siRNA) to evaluate RNF4 and Bloom syndrome helicase (BLM) functions.
- Proteasomal degradation assays.
Main Results:
- RNF4 is essential for DNA replication restart after prolonged HU-induced stress.
- RNF4 depletion inhibits the firing of new replication origins required for restart.
- RNF4 targets and promotes the proteasomal degradation of sumoylated BLM at stalled replication forks.
- Co-depletion of BLM rescues the origin firing defects caused by RNF4 depletion.
Conclusions:
- RNF4 facilitates DNA replication restart by removing sumoylated BLM from collapsed replication forks.
- This removal by RNF4 is critical for the resumption of DNA synthesis after prolonged replication stress.
- RNF4's function in replication stress response differs from its role in repairing gamma-irradiation-induced DSBs.
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