近日，英国癌症研究所教授Max E. Douglas及其研究小组研制了RAP1介导的DNA-PK抑制对染色体末端的保护。2025年4月16日出版的《自然》发表了这项成果。

在这里，该课题组发现庇护蛋白成分TRF2和RAP1与DNA-PK形成复合体，直接抑制其在端粒的末端连接功能。生化实验和低温电镜显示，当与TRF2结合时，RAP1与KU和DNA建立相互作用网络，阻止DNA- pk招募LIG4。在小鼠细胞和人类细胞中，RAP1在抑制染色体末端的cNHEJ时与Apollo核酸酶是冗余的，这表明DNA-PK的抑制与悬垂依赖机制平行地阻止了端粒的变化。他们的实验表明，DNA-PK的末端连接功能在端粒中被直接和特异性地抑制，从而建立了哺乳动物细胞中单个线性染色体维持的分子机制。

研究人员表示，在经典的非同源末端连接（cNHEJ）过程中，DNA依赖性蛋白激酶（DNA- pk）包封游离DNA末端，形成下游末端连接因子包括连接酶4 (LIG4)1的招募平台。DNA-PK也可以结合端粒并调节其切除，但不会在该位置启动cNHEJ。如何以这种具体的方式调节最终加入过程目前尚不清楚。

附：英文原文

Title: Chromosome end protection by RAP1-mediated inhibition of DNA-PK

Author: Eickhoff, Patrik, Sonmez, Ceylan, Fisher, Charlotte E. L., Inian, Oviya, Roumeliotis, Theodoros I., dello Stritto, Angela, Mansfeld, Jrg, Choudhary, Jyoti S., Guettler, Sebastian, Lottersberger, Francisca, Douglas, Max E.

Issue&Volume: 2025-04-16

Abstract: During classical non-homologous end joining (cNHEJ), DNA-dependent protein kinase (DNA-PK) encapsulates free DNA ends, forming a recruitment platform for downstream end-joining factors including ligase 4 (LIG4)1. DNA-PK can also bind telomeres and regulate their resection2,3,4, but does not initiate cNHEJ at this position. How the end-joining process is regulated in this context-specific manner is currently unclear. Here we show that the shelterin components TRF2 and RAP1 form a complex with DNA-PK that directly represses its end-joining function at telomeres. Biochemical experiments and cryo-electron microscopy reveal that when bound to TRF2, RAP1 establishes a network of interactions with KU and DNA that prevents DNA-PK from recruiting LIG4. In mouse and human cells, RAP1 is redundant with the Apollo nuclease in repressing cNHEJ at chromosome ends, demonstrating that the inhibition of DNA-PK prevents telomere fusions in parallel with overhang-dependent mechanisms. Our experiments show that the end-joining function of DNA-PK is directly and specifically repressed at telomeres, establishing a molecular mechanism for how individual linear chromosomes are maintained in mammalian cells.

DOI: 10.1038/s41586-025-08896-1

Source: https://www.nature.com/articles/s41586-025-08896-1