Lee Gregory S, Neiditch Matthew B, Salus Sandra S, Roth David B
The Skirball Institute of Biomolecular Medicine, Lab 2-10 and Department of Pathology, New York University School of Medicine, New York, NY 10016, USA.
Cell. 2004 Apr 16;117(2):171-84. doi: 10.1016/s0092-8674(04)00301-0.
The two major pathways for repairing double-strand breaks (DSBs), homologous recombination and nonhomologous end joining (NHEJ), have traditionally been thought to operate in different stages of the cell cycle. This division of labor is not absolute, however, and precisely what governs the choice of pathway to repair a given DSB has remained enigmatic. We pursued this question by studying the site-specific DSBs created during V(D)J recombination, which relies on classical NHEJ to repair the broken ends. We show that mutations that form unstable RAG postcleavage complexes allow DNA ends to participate in both homologous recombination and the error-prone alternative NHEJ pathway. By abrogating a key function of the complex, these mutations reveal it to be a molecular shepherd that guides DSBs to the proper pathway. We also find that RAG-mediated nicks efficiently stimulate homologous recombination and discuss the implications of these findings for oncogenic chromosomal rearrangements, evolution, and gene targeting.
修复双链断裂（DSB）的两条主要途径，即同源重组和非同源末端连接（NHEJ），传统上被认为在细胞周期的不同阶段发挥作用。然而，这种分工并非绝对，而且究竟是什么决定了修复特定DSB的途径选择仍然是个谜。我们通过研究V（D）J重组过程中产生的位点特异性DSB来探讨这个问题，V（D）J重组依靠经典的NHEJ来修复断裂末端。我们发现，形成不稳定的RAG切割后复合物的突变会使DNA末端既能参与同源重组，也能参与易出错的替代性NHEJ途径。通过消除该复合物的关键功能，这些突变表明它是一个分子引导者，将DSB引导至合适的途径。我们还发现，RAG介导的切口能有效刺激同源重组，并讨论了这些发现对致癌染色体重排、进化和基因靶向的意义。
