Institute for Integrative Biology of the Cell, Institute Joliot, CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette, France.
Institut de Pharmacologie et Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France.
Nat Struct Mol Biol. 2018 Oct;25(10):971-980. doi: 10.1038/s41594-018-0133-6. Epub 2018 Oct 5.
The Ku70-Ku80 (Ku) heterodimer binds rapidly and tightly to the ends of DNA double-strand breaks and recruits factors of the non-homologous end-joining (NHEJ) repair pathway through molecular interactions that remain unclear. We have determined crystal structures of the Ku-binding motifs (KBM) of the NHEJ proteins APLF (A-KBM) and XLF (X-KBM) bound to a Ku-DNA complex. The two KBM motifs bind remote sites of the Ku80 α/β domain. The X-KBM occupies an internal pocket formed by an unprecedented large outward rotation of the Ku80 α/β domain. We observe independent recruitment of the APLF-interacting protein XRCC4 and of XLF to laser-irradiated sites via binding of A- and X-KBMs, respectively, to Ku80. Finally, we show that mutation of the X-KBM and A-KBM binding sites in Ku80 compromises both the efficiency and accuracy of end joining and cellular radiosensitivity. A- and X-KBMs may represent two initial anchor points to build the intricate interaction network required for NHEJ.
Ku70-Ku80（Ku）异二聚体快速而紧密地结合到 DNA 双链断裂的末端，并通过分子相互作用招募非同源末端连接（NHEJ）修复途径的因子，这些相互作用仍不清楚。我们已经确定了 NHEJ 蛋白 APLF（A-KBM）和 XLF（X-KBM）的 Ku 结合基序（KBM）与 Ku-DNA 复合物结合的晶体结构。这两个 KBM 基序结合 Ku80α/β 结构域的远程位点。X-KBM 占据由 Ku80α/β 结构域前所未有的向外旋转形成的内部口袋。我们观察到通过 A-KBM 和 X-KBM 分别与 Ku80 的结合，APLF 相互作用蛋白 XRCC4 和 XLF 的独立募集到激光照射的位点。最后，我们表明 Ku80 中 X-KBM 和 A-KBM 结合位点的突变会损害末端连接的效率和准确性以及细胞的放射敏感性。A-KBM 和 X-KBM 可能代表建立 NHEJ 所需的复杂相互作用网络的两个初始锚点。
