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

• 成果类型: Article
• 署名作者: Eickhoff, Patrik; Sonmez, Ceylan; Fisher, Charlotte E. L.; Inian, Oviya; Roumeliotis, Theodoros I.; dello Stritto, Angela; Mansfeld, Jorg; Choudhary, Jyoti S.; Guettler, Sebastian; Lottersberger, Francisca; Douglas, Max E.
• 署名单位: Royal Marsden NHS Foundation Trust; University of London; Institute of Cancer Research - UK; Linkoping University; University of London; Institute of Cancer Research - UK; Royal Marsden NHS Foundation Trust; Royal Marsden NHS Foundation Trust; University of London; Institute of Cancer Research - UK; University of London; Institute of Cancer Research - UK; Royal Marsden NHS Foundation Trust
• 刊物名称: Nature
• ISSN/ISSBN: 0028-3001
• DOI: 10.1038/s41586-025-08896-1
• 发表日期: 2025-06-26
• 关键词: human rap1; cryo-em; telomere protection; complex; binding; ku; apollo; trf2; Visualization; requirement

摘要

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.