Dimers of DNA-PK create a stage for DNA double-strand break repair
Dimers of DNA-PK create a stage for DNA double-strand break repair
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DOI：
10.1038/s41594-020-00517-x
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发表时间：
2020-10-19
影响因子：
16.8
通讯作者：
Blundell, Tom L.
中科院分区：
文献类型：
--
作者：
Chaplin, Amanda K.;Hardwick, Steven W.;Blundell, Tom L.
一种新的人类DNA-PKcs与Ku 70/80异二聚体和DNA复合的冷冻电镜结构揭示了Ku 80-DNA-PKcs相互作用如何创建一个介导DNA双链断裂修复的支架。DNA双链断裂是最危险的DNA损伤类型，如果修复不正确，可能导致癌症。在人类中，Ku 70/80识别DNA断裂末端，并在非同源末端连接（NHEJ）过程中招募DNA依赖性蛋白激酶催化亚基（DNA-PKcs）形成DNA依赖性蛋白激酶全酶（DNA-PK）。我们提出了一个2.8埃分辨率的cryo-EM结构的DNA-PKcs，允许精确的氨基酸序列登记在以前的4.3埃的X射线图中未解释的区域。我们还报告了一个cryo-EM结构的DNA-PK在3.5埃的分辨率，并揭示了二聚体介导的Ku 80 C端。二聚体形成的核心是Ku 80保守C-末端螺旋的结构域交换。我们的研究结果表明NHEJ利用DNA-PK二聚体将断裂的DNA末端结合在一起的新机制。此外，NHEJ的药物抑制与化疗和放疗的组合已被证明是成功的，使这些模型成为基于结构的药物靶向努力的核心。
A new cryo-EM structure of human DNA-PKcs in complex with a Ku70/80 heterodimer and DNA reveals how Ku80-DNA-PKcs interactions create a scaffold to mediate DNA double-strand break repair.DNA double-strand breaks are the most dangerous type of DNA damage and, if not repaired correctly, can lead to cancer. In humans, Ku70/80 recognizes DNA broken ends and recruits the DNA-dependent protein kinase catalytic subunit (DNA-PKcs) to form DNA-dependent protein kinase holoenzyme (DNA-PK) in the process of non-homologous end joining (NHEJ). We present a 2.8-angstrom-resolution cryo-EM structure of DNA-PKcs, allowing precise amino acid sequence registration in regions uninterpreted in previous 4.3-angstrom X-ray maps. We also report a cryo-EM structure of DNA-PK at 3.5-angstrom resolution and reveal a dimer mediated by the Ku80 C terminus. Central to dimer formation is a domain swap of the conserved C-terminal helix of Ku80. Our results suggest a new mechanism for NHEJ utilizing a DNA-PK dimer to bring broken DNA ends together. Furthermore, drug inhibition of NHEJ in combination with chemo- and radiotherapy has proved successful, making these models central to structure-based drug targeting efforts.