Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
Mol Cell. 2009 Dec 25;36(6):954-69. doi: 10.1016/j.molcel.2009.12.002.
In response to DNA double-strand breaks (DSBs), cells sense the DNA lesions and then activate the protein kinase ATM. Subsequent DSB resection produces RPA-coated ssDNA that is essential for activation of the DNA damage checkpoint and DNA repair by homologous recombination (HR). However, the biochemical mechanism underlying the transition from DSB sensing to resection remains unclear. Using Xenopus egg extracts and human cells, we show that the tumor suppressor protein CtIP plays a critical role in this transition. We find that CtIP translocates to DSBs, a process dependent on the DSB sensor complex Mre11-Rad50-NBS1, the kinase activity of ATM, and a direct DNA-binding motif in CtIP, and then promotes DSB resection. Thus, CtIP facilitates the transition from DSB sensing to processing: it does so by binding to the DNA at DSBs after DSB sensing and ATM activation and then promoting DNA resection, leading to checkpoint activation and HR.
针对 DNA 双链断裂（DSBs），细胞感知 DNA 损伤，然后激活蛋白激酶 ATM。随后的 DSB 切除产生 RPA 包被的单链 DNA，这对于激活 DNA 损伤检查点和同源重组（HR）修复至关重要。然而，从 DSB 感应到切除的生化机制仍不清楚。利用非洲爪蟾卵提取物和人细胞，我们表明肿瘤抑制蛋白 CtIP 在这个过程中起着关键作用。我们发现 CtIP 易位到 DSBs，这个过程依赖于 DSB 传感器复合物 Mre11-Rad50-NBS1、ATM 的激酶活性以及 CtIP 中的一个直接 DNA 结合基序，然后促进 DSB 切除。因此，CtIP 促进了从 DSB 感应到处理的转变：它通过在 DSB 感应和 ATM 激活后与 DSB 处的 DNA 结合，然后促进 DNA 切除，从而激活检查点并促进 HR。
