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Published on: August 23, 2024
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RAD51 protects abasic sites to prevent replication fork breakage
Yodhara Wijesekara Hanthi1, Miguel Angel Ramirez-Otero1, Robert Appleby2
1IFOM, The AIRC Institute of Molecular Oncology, Milan, Italy.
Molecular Cell
|August 23, 2024
Summary
DNA repair protein RAD51 protects against genomic instability by shielding abasic sites, preventing DNA breaks during replication. This is crucial for maintaining genome integrity when DNA damage occurs.
Area of Science:
- Molecular Biology
- Genomics
- DNA Repair Mechanisms
Background:
- Abasic sites are common DNA lesions arising from base modifications.
- Unrepaired abasic sites in single-stranded DNA (ssDNA) pose a risk of chromosomal breakage during replication.
- The mechanisms preventing abasic DNA rupture and subsequent genomic instability are not fully understood.
Purpose of the Study:
- To elucidate the role of RAD51 in protecting abasic sites.
- To understand how abasic site cleavage is prevented during DNA replication.
- To investigate the contribution of BRCA2 and RAD51 to genomic stability in the context of abasic lesions.
Main Methods:
- Cryo-electron microscopy (cryo-EM) to visualize protein-DNA interactions.
- Xenopus laevis egg extracts and human cell lines for experimental models.
- Assays to detect abasic site accumulation and DNA cleavage.
Main Results:
- RAD51 nucleofilaments specifically recognize and bind to abasic sites, increasing their association rate with DNA.
- Loss of BRCA2 or RAD51 leads to abasic site accumulation and sensitivity to APE1 cleavage.
- RAD51 binding prevents MRE11-RAD50 complex-mediated cleavage of abasic DNA, suppressing replication fork breakage.
Conclusions:
- RAD51 plays a critical protective role at abasic sites, preventing DNA breaks.
- BRCA2 and RAD51 are essential for maintaining genomic stability against DNA base alterations.
- This study reveals a key mechanism for safeguarding replicating DNA from unrepaired abasic lesions.
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