Department of Cancer Biology, Cleveland Clinic Lerner Research Institute, Cleveland, OH, USA.
Department of Cardiovascular & Metabolic Sciences, Cleveland Clinic Lerner Research Institute, Cleveland, OH, USA.
Nucleic Acids Res. 2023 Mar 21;51(5):2238-2256. doi: 10.1093/nar/gkad073.
The 53BP1-dependent end-joining pathway plays a critical role in double-strand break (DSB) repair. However, the regulators of 53BP1 in chromatin remain incompletely characterized. In this study, we identified HDGFRP3 (hepatoma-derived growth factor related protein 3) as a 53BP1-interacting protein. The HDGFRP3-53BP1 interaction is mediated by the PWWP domain of HDGFRP3 and the Tudor domain of 53BP1. Importantly, we observed that the HDGFRP3-53BP1 complex co-localizes with 53BP1 or γH2AX at sites of DSB and participates in the response to DNA damage repair. Loss of HDGFRP3 impairs classical non-homologous end-joining repair (NHEJ), curtails the accumulation of 53BP1 at DSB sites, and enhances DNA end-resection. Moreover, the HDGFRP3-53BP1 interaction is required for cNHEJ repair, 53BP1 recruitment at DSB sites, and inhibition of DNA end resection. In addition, loss of HDGFRP3 renders BRCA1-deficient cells resistant to PARP inhibitors by facilitating end-resection in BRCA1 deficient cells. We also found that the interaction of HDGFRP3 with methylated H4K20 was dramatically decreased; in contrast, the 53BP1-methylated H4K20 interaction was increased after ionizing radiation, which is likely regulated by protein phosphorylation and dephosphorylation. Taken together, our data reveal a dynamic 53BP1-methylated H4K20-HDGFRP3 complex that regulates 53BP1 recruitment at DSB sites, providing new insights into our understanding of the regulation of 53BP1-mediated DNA repair pathway.
53BP1 依赖性末端连接途径在双链断裂 (DSB) 修复中起着关键作用。然而，染色质中 53BP1 的调节剂仍不完全特征化。在这项研究中，我们鉴定了 HDGFRP3（肝癌衍生生长因子相关蛋白 3）作为 53BP1 的相互作用蛋白。HDGFRP3-53BP1 相互作用由 HDGFRP3 的 PWWP 结构域和 53BP1 的 Tudor 结构域介导。重要的是，我们观察到 HDGFRP3-53BP1 复合物与 53BP1 或 γH2AX 在 DSB 部位共定位，并参与 DNA 损伤修复反应。HDGFRP3 的缺失会损害经典的非同源末端连接修复 (NHEJ)，限制 53BP1 在 DSB 部位的积累，并增强 DNA 末端切除。此外，HDGFRP3-53BP1 相互作用对于 cNHEJ 修复、53BP1 在 DSB 部位的募集以及抑制 DNA 末端切除都是必需的。此外，HDGFRP3 的缺失通过促进 BRCA1 缺陷细胞中的末端切除，使 BRCA1 缺陷细胞对 PARP 抑制剂产生抗性。我们还发现，HDGFRP3 与甲基化 H4K20 的相互作用明显减少；相比之下，电离辐射后 53BP1 与甲基化 H4K20 的相互作用增加，这可能受蛋白磷酸化和去磷酸化的调节。总之，我们的数据揭示了一个动态的 53BP1 甲基化 H4K20-HDGFRP3 复合物，该复合物调节 53BP1 在 DSB 部位的募集，为我们理解 53BP1 介导的 DNA 修复途径的调控提供了新的见解。
