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Updated: Jun 5, 2025

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Published on: June 26, 2020
Repair of replication-dependent double-strand breaks differs between the leading and lagging strands
Michael T Kimble1, Aakanksha Sane2, Robert J D Reid3
1Program in Biological Sciences, Columbia University, New York, NY 10027, USA; Department of Microbiology & Immunology, Columbia University Irving Medical Center, New York, NY 10032, USA.
DNA replication can turn single-strand breaks into double-strand breaks (DSBs). The replication-coupled nucleosome assembly pathway, particularly histone H3K56 acetylation, is crucial for repairing these replication-dependent DSBs.
Area of Science:
- Molecular Biology
- Genetics
- DNA Repair
Background:
- Single-strand breaks (SSBs) are common DNA lesions.
- Replication can convert SSBs into cytotoxic double-strand breaks (DSBs).
Purpose of the Study:
- Investigate the repair mechanisms of replication-dependent DSBs.
- Identify factors involved in repairing DSBs arising from nicks during DNA replication.
Main Methods:
- Used Cas9 nickase (nCas9) to create site- and strand-specific nicks in yeast.
- Performed genome-wide screens to identify repair factors.
- Analyzed homologous recombination (HR) and non-homologous end joining (NHEJ) pathways.
Main Results:
- nCas9-induced nicks convert to DSBs during S phase.
- DSB repair relies on HR, not NHEJ.
- Replication-coupled nucleosome assembly (RCNA) pathway components are essential for repair.
- RCNA pathway, via H3K56 acetylation, is key for leading-strand template nick repair.
Conclusions:
- Replication-dependent DSBs are primarily repaired by HR using sister chromatids.
- The RCNA pathway plays a vital role in repairing DSBs originating from nicks during replication.
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