Weill Cornell Medicine Pharmacology Graduate Program, New York, United States.
Weill Cornell Medicine, Department of Pathology and Laboratory Medicine, New York, United States.
Elife. 2022 May 16;11:e74700. doi: 10.7554/eLife.74700.
DNA double-strand break (DSB) repair by homologous recombination is confined to the S and G phases of the cell cycle partly due to 53BP1 antagonizing DNA end resection in G phase and non-cycling quiescent (G) cells where DSBs are predominately repaired by non-homologous end joining (NHEJ). Unexpectedly, we uncovered extensive MRE11- and CtIP-dependent DNA end resection at DSBs in G murine and human cells. A whole genome CRISPR/Cas9 screen revealed the DNA-dependent kinase (DNA-PK) complex as a key factor in promoting DNA end resection in G cells. In agreement, depletion of FBXL12, which promotes ubiquitylation and removal of the KU70/KU80 subunits of DNA-PK from DSBs, promotes even more extensive resection in G cells. In contrast, a requirement for DNA-PK in promoting DNA end resection in proliferating cells at the G or G phase of the cell cycle was not observed. Our findings establish that DNA-PK uniquely promotes DNA end resection in G, but not in G or G phase cells, which has important implications for DNA DSB repair in quiescent cells.
DNA 双链断裂 (DSB) 的同源重组修复仅限于细胞周期的 S 和 G 期，部分原因是 53BP1 在 G 期拮抗 DNA 末端切除，并且非循环静止 (G) 细胞中 DSB 主要通过非同源末端连接 (NHEJ) 修复。出乎意料的是，我们在 G 期的小鼠和人类细胞中发现了广泛的 MRE11 和 CtIP 依赖性 DNA 末端切除。全基因组 CRISPR/Cas9 筛选显示，DNA 依赖性激酶 (DNA-PK) 复合物是促进 G 细胞中 DNA 末端切除的关键因素。一致地，耗尽 FBXL12（促进 DNA-PK 上的 KU70/KU80 亚基的泛素化和去除）促进了 G 细胞中甚至更广泛的切除。相比之下，在细胞周期的 G 或 G 期的增殖细胞中，DNA-PK 促进 DNA 末端切除的需求并未观察到。我们的发现确立了 DNA-PK 独特地促进 G 期的 DNA 末端切除，但不促进 G 期或 G 期细胞的切除，这对静止细胞中的 DNA DSB 修复具有重要意义。
