RAG proteins shepherd double-strand breaks to a specific pathway, suppressing error-prone repair, but RAG nicking initiates homologous recombination.
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.
Lee
Gregory S
GS
The Skirball Institute of Biomolecular Medicine, Lab 2-10 and Department of Pathology, New York University School of Medicine, New York, NY 10016, USA.
Neiditch
Matthew B
MB
Salus
Sandra S
SS
Roth
David B
DB
D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D004247:DNA / Q000235:genetics / Q000378:metabolism*; D004249:DNA Damage / Q000235:genetics*; D004260:DNA Repair / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D019143:Evolution, Molecular; D018390:Gene Targeting; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D016297:Mutagenesis, Site-Directed / Q000235:genetics; D009154:Mutation / Q000235:genetics; D011995:Recombination, Genetic / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D014178:Translocation, Genetic / Q000235:genetics; D045567:VDJ Recombinases / Q000235:genetics / Q000378:metabolism
D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; C064655:V(D)J recombination activating protein 2; C064658:RAG-1 protein; D004247:DNA; D045567:VDJ Recombinases