title: Homologous recombination is a primary pathway to repair DNA double-strand breaks generated during DNA rereplication.
abstract: Re-initiation of DNA replication at origins within a given cell cycle would result in DNA rereplication, which can lead to genome instability and tumorigenesis. DNA rereplication can be induced by loss of licensing control at cellular replication origins, or by viral protein-driven multiple rounds of replication initiation at viral origins. DNA double-strand breaks (DSBs) are generated during rereplication, but the mechanisms of how these DSBs are repaired to maintain genome stability and cell viability are poorly understood in mammalian cells. We generated novel EGFP-based DSB repair substrates, which specifically monitor the repair of rereplication-associated DSBs. We demonstrated that homologous recombination (HR) is an important mechanism to repair rereplication-associated DSBs, and sister chromatids are used as templates for such HR-mediated DSB repair. Micro-homology-mediated non-homologous end joining (MMEJ) can also be used but to a lesser extent compared to HR, whereas Ku-dependent classical non-homologous end joining (C-NHEJ) has a minimal role to repair rereplication-associated DSBs. In addition, loss of HR activity leads to severe cell death when rereplication is induced. Therefore, our studies identify HR, the most conservative repair pathway, as the primary mechanism to repair DSBs upon rereplication.
authors.affiliation: From the Department of Molecular and Experimental Medicine, The Scripps Research Institute, La, Jolla, California 92037.
authors.forename: Lan N
authors.initials: LN
authors.lastname: Truong
authors.affiliation: From the Department of Molecular and Experimental Medicine, The Scripps Research Institute, La, Jolla, California 92037.
authors.forename: Yongjiang
authors.initials: Y
authors.lastname: Li
authors.affiliation: From the Department of Molecular and Experimental Medicine, The Scripps Research Institute, La, Jolla, California 92037.
authors.forename: Emily
authors.initials: E
authors.lastname: Sun
authors.affiliation: From the Department of Molecular and Experimental Medicine, The Scripps Research Institute, La, Jolla, California 92037.
authors.forename: Katrina
authors.initials: K
authors.lastname: Ang
authors.affiliation: From the Department of Molecular and Experimental Medicine, The Scripps Research Institute, La, Jolla, California 92037.
authors.forename: Patty Yi-Hwa
authors.initials: PY
authors.lastname: Hwang
authors.affiliation: From the Department of Molecular and Experimental Medicine, The Scripps Research Institute, La, Jolla, California 92037 xiaohwu@scripps.edu.
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Wu
mesh_terms: D063646:Carcinogenesis; D016923:Cell Death; D045744:Cell Line, Tumor; D002469:Cell Separation; D002470:Cell Survival; D053903:DNA Breaks, Double-Stranded; D059766:DNA End-Joining Repair; D004260:DNA Repair; D005434:Flow Cytometry; D049452:Green Fluorescent Proteins / Q000378:metabolism; D057809:HEK293 Cells; D059765:Homologous Recombination; D006801:Humans; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism; D016366:Open Reading Frames; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D011995:Recombination, Genetic; D055544:beta-Globins / Q000378:metabolism
chemical_list: D034741:RNA, Small Interfering; D055544:beta-Globins; D049452:Green Fluorescent Proteins
keywords: DNA Repair; DNA Replication; DNA Rereplication; DSB Repair; Genomic Instability; Homologous Recombination; MMEJ; Viral Replication