State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, 100871, Beijing, China.
Nat Commun. 2018 Sep 25;9(1):3925. doi: 10.1038/s41467-018-06407-7.
53BP1 with its downstream proteins, RIF1, PTIP and REV7, antagonizes BRCA1-dependent homologous recombination (HR) and promotes non-homologous end joining (NHEJ) in an unclear manner. Here we show that REV7 forms a complex with two proteins, FAM35A and C20ORF196. We demonstrate that FAM35A preferentially binds single-strand DNA (ssDNA) in vitro, and is recruited to DSBs as a complex with C20ORF196 and REV7 downstream of RIF1 in vivo. Epistasis analysis shows that both proteins act in the same pathway as RIF1 in NHEJ. The defects in HR pathway to repair DSBs and the reduction in resection of broken DNA ends in BRCA1-mutant cells can be largely suppressed by inactivating FAM35A or C20ORF196, indicating that FAM35A and C20ORF196 prevent end resection in these cells. Together, our data identified a REV7-FAM35A-C20ORF196 complex that binds and protects broken DNA ends to promote the NHEJ pathway for DSB repair.
53BP1 及其下游蛋白 RIF1、PTIP 和 REV7 以一种不明确的方式拮抗 BRCA1 依赖性同源重组 (HR) 并促进非同源末端连接 (NHEJ)。在这里，我们显示 REV7 与两种蛋白质 FAM35A 和 C20ORF196 形成复合物。我们证明 FAM35A 在体外优先结合单链 DNA (ssDNA)，并作为与 C20ORF196 和 RIF1 下游的 REV7 的复合物被募集到体内的 DSB 中。上位性分析表明，这两种蛋白质在 NHEJ 中与 RIF1 作用于相同的途径。BRCA1 突变细胞中修复 DSB 的 HR 途径缺陷和断裂 DNA 末端的切除减少可以通过失活 FAM35A 或 C20ORF196 得到很大程度的抑制，表明 FAM35A 和 C20ORF196 防止这些细胞中的末端切除。总之，我们的数据确定了一个 REV7-FAM35A-C20ORF196 复合物，该复合物结合并保护断裂的 DNA 末端，以促进 NHEJ 途径修复 DSB。
