Laboratory of Genomic Instability and Cancer therapeutics, Chosun University School of Medicine, 309 Pilmun-daero, Dong-gu, Gwangju 61452, Republic of Korea.
Department of Cellular and Molecular Medicine, Chosun University School of Medicine, 309 Pilmun-daero, Dong-gu, Gwangju 61452, Republic of Korea.
Nucleic Acids Res. 2022 Oct 14;50(18):10469-10486. doi: 10.1093/nar/gkac808.
Human CtIP maintains genomic integrity primarily by promoting 5' DNA end resection, an initial step of the homologous recombination (HR). A few mechanisms have been suggested as to how CtIP recruitment to damage sites is controlled, but it is likely that we do not yet have full understanding of the process. Here, we provide evidence that CtIP recruitment and functioning are controlled by the SIAH2 E3 ubiquitin ligase. We found that SIAH2 interacts and ubiquitinates CtIP at its N-terminal lysine residues. Mutating the key CtIP lysine residues impaired CtIP recruitment to DSBs and stalled replication forks, DSB end resection, overall HR repair capacity of cells, and recovery of stalled replication forks, suggesting that the SIAH2-induced ubiquitination is important for relocating CtIP to sites of damage. Depleting SIAH2 consistently phenocopied these results. Overall, our work suggests that SIAH2 is a new regulator of CtIP and HR repair, and emphasizes that SIAH2-mediated recruitment of the CtIP is an important step for CtIP's function during HR repair.
人类 CtIP 主要通过促进 5' DNA 末端切除来维持基因组完整性，这是同源重组 (HR) 的初始步骤。已经提出了几种 CtIP 招募到损伤部位的控制机制，但我们可能还没有完全理解这个过程。在这里，我们提供的证据表明，CtIP 的招募和功能受到 SIAH2 E3 泛素连接酶的控制。我们发现 SIAH2 在其 N 端赖氨酸残基上相互作用并泛素化 CtIP。突变关键的 CtIP 赖氨酸残基会损害 CtIP 向 DSBs 和复制叉停滞的招募、DSB 末端切除、细胞整体 HR 修复能力以及停滞复制叉的恢复，表明 SIAH2 诱导的泛素化对于将 CtIP 重新定位到损伤部位很重要。耗尽 SIAH2 始终会复制这些结果。总的来说，我们的工作表明 SIAH2 是 CtIP 和 HR 修复的新调节剂，并强调 SIAH2 介导的 CtIP 募集是 CtIP 在 HR 修复过程中发挥功能的重要步骤。
