Department of Biological Chemistry, School of Medicine, University of California, Irvine, CA 92697-1700, USA.
Beckman Laser Institute and Medical Clinic, University of California, Irvine, 1002 Health Sciences Road East, Irvine, CA 92612, USA.
J Cell Sci. 2018 Dec 5;131(23):jcs219311. doi: 10.1242/jcs.219311.
TRF2 (TERF2) binds to telomeric repeats and is critical for telomere integrity. Evidence suggests that it also localizes to non-telomeric DNA damage sites. However, this recruitment appears to be precarious and functionally controversial. We find that TRF2 recruitment to damage sites occurs by a two-step mechanism: the initial rapid recruitment (phase I), and stable and prolonged association with damage sites (phase II). Phase I is poly(ADP-ribose) polymerase (PARP)-dependent and requires the N-terminal basic domain. The phase II recruitment requires the C-terminal MYB/SANT domain and the iDDR region in the hinge domain, which is mediated by the MRE11 complex and is stimulated by TERT. PARP-dependent recruitment of intrinsically disordered proteins contributes to transient displacement of TRF2 that separates two phases. TRF2 binds to I-PpoI-induced DNA double-strand break sites, which is enhanced by the presence of complex damage and is dependent on PARP and the MRE11 complex. TRF2 depletion affects non-sister chromatid homologous recombination repair, but not homologous recombination between sister chromatids or non-homologous end-joining pathways. Our results demonstrate a unique recruitment mechanism and function of TRF2 at non-telomeric DNA damage sites.
端粒结合因子 2（TRF2）结合到端粒重复序列上，对于端粒的完整性至关重要。有证据表明，它也定位于非端粒 DNA 损伤部位。然而，这种募集似乎不稳定，并且功能上存在争议。我们发现，TRF2 募集到损伤部位是通过两步机制发生的：初始快速募集（I 相），以及与损伤部位的稳定和持久关联（II 相）。I 相依赖于聚（ADP-核糖）聚合酶（PARP），需要 N 端碱性结构域。第二阶段的募集需要 C 端 MYB/SANT 结构域和铰链域中的 iDDR 区域，这是由 MRE11 复合物介导的，并受到 TERT 的刺激。固有无序蛋白的 PARP 依赖性募集有助于 TRF2 的瞬时置换，从而分离两个阶段。TRF2 结合到 I-PpoI 诱导的 DNA 双链断裂位点，复杂损伤的存在增强了这种结合，并且依赖于 PARP 和 MRE11 复合物。TRF2 耗竭会影响非姐妹染色单体同源重组修复，但不影响姐妹染色单体之间的同源重组或非同源末端连接途径。我们的研究结果表明了 TRF2 在非端粒 DNA 损伤部位的独特募集机制和功能。
