title: The homologous recombination protein RAD51D protects the genome from large deletions.
abstract: Homologous recombination (HR) is a DNA double-strand break (DSB) repair pathway that protects the genome from chromosomal instability. RAD51 mediator proteins (i.e. paralogs) are critical for efficient HR in mammalian cells. However, how HR-deficient cells process DSBs is not clear. Here, we utilized a loss-of-function HR-reporter substrate to simultaneously monitor HR-mediated gene conversion and non-conservative mutation events. The assay is designed around a heteroallelic duplication of the Aprt gene at its endogenous locus in isogenic Chinese hamster ovary cell lines. We found that RAD51D-deficient cells had a reduced capacity for HR-mediated gene conversion both spontaneously and in response to I-SceI-induced DSBs. Further, RAD51D-deficiency shifted DSB repair toward highly deleterious single-strand annealing (SSA) and end-joining processes that led to the loss of large chromosomal segments surrounding site-specific DSBs at an exceptionally high frequency. Deletions in the proximity of the break were due to a non-homologous end-joining pathway, while larger deletions were processed via a SSA pathway. Overall, our data revealed that, in addition to leading to chromosomal abnormalities, RAD51D-deficiency resulted in a high frequency of deletions advancing our understanding of how a RAD51 paralog is involved in maintaining genomic stability and how its deficiency may predispose cells to tumorigenesis.
authors.affiliation: Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, Dell Pediatric Research Institute, Austin, TX 78723, USA.
authors.forename: Wade A
authors.initials: WA
authors.lastname: Reh
authors.affiliation: Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center Science Park, Smithville, TX 78957, USA.
authors.forename: Rodney S
authors.initials: RS
authors.lastname: Nairn
authors.affiliation: Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Cancer Center Science Park, Smithville, TX 78957, USA.
authors.forename: Megan P
authors.initials: MP
authors.lastname: Lowery
authors.affiliation: Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, Dell Pediatric Research Institute, Austin, TX 78723, USA.
authors.forename: Karen M
authors.initials: KM
authors.lastname: Vasquez
mesh_terms: D000818:Animals; D016466:CHO Cells; D043171:Chromosomal Instability; D003412:Cricetulus; D053903:DNA Breaks, Double-Stranded; D004249:DNA Damage; D004260:DNA Repair; D015252:Deoxyribonucleases, Type II Site-Specific / Q000378:metabolism; D015870:Gene Expression; D055786:Gene Knockout Techniques; D017930:Genes, Reporter; D016678:Genome; D059765:Homologous Recombination; D009154:Mutation; D051135:Rad51 Recombinase / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion
chemical_list: D051135:Rad51 Recombinase; D015252:Deoxyribonucleases, Type II Site-Specific