| Affiliation: | 1. Lady Davis Institute for Medical Research, Segal Cancer Centre, Jewish General Hospital, Montreal, QC, Canada;2. Department of Microbiology and Immunology, McGill University, Montreal, QC, Canada;3. Gerald Bronfman Department of Oncology, McGill University, Montreal, QC, Canada;4. Department of Biology, Université de Sherbrooke, Sherbrooke, QC, Canada;5. Genome Stability Laboratory, CHU de Québec Research Center, Quebec City, QC, Canada;6. Department of Molecular Biology, Medical Biochemistry and Pathology, Laval University Cancer Research Center, Quebec City, QC, Canada;7. Division of Experimental Medicine, McGill University, Montreal, QC, Canada;8. Institut de Recherches Cliniques de Montréal (IRCM), Montreal, QC, Canada;9. Department of Anatomy and Cell Biology, McGill University, Montreal, QC, Canada;10. Department of Developmental Biology and Cancer Research, The Institute for Medical Research Israel‐Canada, The Hebrew University of Jerusalem, Jerusalem, Israel;11. Rosalind and Morris Goodman Cancer Research Centre, McGill University, Montreal, QC, Canada;12. Department of Epidemiology, Biostatistics and Occupational Health, MGill University, Montreal, QC, Canada;13. Département de Biochimie et Médecine Moléculaire, Université de Montréal, Montreal, QC, Canada;14. Département de Médecine (Programmes de Biologie Moléculaire), Université de Montréal, Montreal, QC, Canada |
| Abstract: | DNA double‐strand breaks (DSBs) can be repaired by two major pathways: non‐homologous end‐joining (NHEJ) and homologous recombination (HR). DNA repair pathway choice is governed by the opposing activities of 53BP1, in complex with its effectors RIF1 and REV7, and BRCA1. However, it remains unknown how the 53BP1/RIF1/REV7 complex stimulates NHEJ and restricts HR to the S/G2 phases of the cell cycle. Using a mass spectrometry (MS)‐based approach, we identify 11 high‐confidence REV7 interactors and elucidate the role of SHLD2 (previously annotated as FAM35A and RINN2) as an effector of REV7 in the NHEJ pathway. FAM35A depletion impairs NHEJ‐mediated DNA repair and compromises antibody diversification by class switch recombination (CSR) in B cells. FAM35A accumulates at DSBs in a 53BP1‐, RIF1‐, and REV7‐dependent manner and antagonizes HR by limiting DNA end resection. In fact, FAM35A is part of a larger complex composed of REV7 and SHLD1 (previously annotated as C20orf196 and RINN3), which promotes NHEJ and limits HR. Together, these results establish SHLD2 as a novel effector of REV7 in controlling the decision‐making process during DSB repair. |
