CtIP tetramer assembly is required for DNA-end resection and repair.
CtIP tetramer assembly is required for DNA-end resection and repair.
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DOI：
10.1038/nsmb.2937
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发表时间：
2015-02
影响因子：
16.8
通讯作者：
Pellegrini L
中科院分区：
文献类型：
--
作者：
Davies OR;Forment JV;Sun M;Belotserkovskaya R;Coates J;Galanty Y;Demir M;Morton CR;Rzechorzek NJ;Jackson SP;Pellegrini L
哺乳动物CtIP蛋白在DNA双链断裂（DSB）修复中起主要作用。虽然CtIP促进DNA末端切除以准备同源依赖性DSB修复是公认的，但该功能的分子基础仍然未知。在这里，我们通过生物物理和X射线晶体学分析表明，人CtIP的N-末端结构域作为一个稳定的同源四聚体存在。四聚化的结果从CtIP的卷曲螺旋区域的N-末端延伸之间的联锁相互作用，导致一个'二聚体的二聚体'架构。通过对CtIP结构的询问，我们确定了一个点突变，该点突变废除了N-末端结构域的四聚化，同时在体外保留了二聚化。重要的是，我们确定这种突变消除了细胞中的CtIP寡聚体组装，导致DNA末端切除和基因转换的强烈缺陷。这些发现表明，这里描述的CtIP四聚体结构是必要的有效的DSB修复同源重组。
Mammalian CtIP protein plays major roles in DNA double-strand break (DSB) repair. While it is well-established that CtIP promotes DNA-end resection in preparation for homology-dependent DSB repair, the molecular basis for this function remains unknown. Here we show by biophysical and X-ray crystallographic analyses that the N-terminal domain of human CtIP exists as a stable homotetramer. Tetramerization results from interlocking interactions between the N-terminal extensions of CtIP’s coiled-coil region, leading to a ‘dimer-of-dimers’ architecture. Through interrogation of the CtIP structure, we identify a point mutation that abolishes tetramerization of the N-terminal domain while preserving dimerization in vitro. Importantly, we establish that this mutation abrogates CtIP oligomer assembly in cells, leading to strong defects in DNA-end resection and gene conversion. These findings indicate that the CtIP tetramer architecture described here is essential for effective DSB repair by homologous recombination.