Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK.
Graduate School of Frontier Sciences, The University of Tokyo, Tokyo, Japan.
Open Biol. 2021 Jun;11(6):210060. doi: 10.1098/rsob.210060. Epub 2021 Jun 16.
The DNA repair factor CtIP has a critical function in double-strand break (DSB) repair by homologous recombination, promoting the assembly of the repair apparatus at DNA ends and participating in DNA-end resection. However, the molecular mechanisms of CtIP function in DSB repair remain unclear. Here, we present an atomic model for the three-dimensional architecture of human CtIP, derived from a multi-disciplinary approach that includes X-ray crystallography, small-angle X-ray scattering (SAXS) and diffracted X-ray tracking (DXT). Our data show that CtIP adopts an extended dimer-of-dimers structure, in agreement with a role in bridging distant sites on chromosomal DNA during the recombinational repair. The zinc-binding motif in the CtIP N-terminus alters dynamically the coiled-coil structure, with functional implications for the long-range interactions of CtIP with DNA. Our results provide a structural basis for the three-dimensional arrangement of chains in the CtIP tetramer, a key aspect of CtIP function in DNA DSB repair.
DNA 修复因子 CtIP 在同源重组介导的双链断裂（DSB）修复中具有关键作用，它促进修复装置在 DNA 末端的组装，并参与 DNA 末端切除。然而，CtIP 在 DSB 修复中的功能的分子机制尚不清楚。在这里，我们通过包括 X 射线晶体学、小角度 X 射线散射（SAXS）和衍射 X 射线跟踪（DXT）在内的多学科方法，提出了人 CtIP 的三维结构的原子模型。我们的数据表明，CtIP 采用扩展的二聚体-二聚体结构，与在重组修复过程中桥接染色体 DNA 上的远距离位点的作用一致。CtIP N 端的锌结合基序动态改变了卷曲螺旋结构，对 CtIP 与 DNA 的长程相互作用具有功能意义。我们的结果为 CtIP 四聚体中链的三维排列提供了结构基础，这是 CtIP 在 DNA DSB 修复中功能的关键方面。
