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Updated: Jun 15, 2026

Detection of DNA Breaks in Dividing Human Cells by Neutral Comet Assay
Published on: August 23, 2024
Hydroxyurea-stalled replication forks become progressively inactivated and require two different RAD51-mediated
Eva Petermann1, Manuel Luís Orta, Natalia Issaeva
1Gray Institute for Radiation Oncology and Biology, University of Oxford, Oxford OX3 7DQ, UK.
None:
Faithful DNA replication is essential to all life. Hydroxyurea (HU) depletes the cells of dNTPs, which initially results in stalled replication forks that, after prolonged treatment, collapse into DSBs. Here, we report that stalled replication forks are efficiently restarted in a RAD51-dependent process that does not trigger homologous recombination (HR). The XRCC3 protein, which is required for RAD51 foci formation, is also required for replication restart of HU-stalled forks, suggesting that RAD51-mediated strand invasion supports fork restart. In contrast, replication forks collapsed by prolonged replication blocks do not restart, and global replication is rescued by new origin firing. We find that RAD51-dependent HR is triggered for repair of collapsed replication forks, without apparent restart. In conclusion, our data suggest that restart of stalled replication forks and HR repair of collapsed replication forks require two distinct RAD51-mediated pathways.
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