The V(D)J recombination machinery is organized as large complexes anchored on the nuclear matrix (62.1)

Abstract

Abstract V(D)J recombination provides the foundation for adaptive immunity. This complicated process involves the cleavage of specific recombination signal sequences (RSS) by the recombination activating gene products, RAG1 and RAG2, followed by repair of the DNA double-stranded breaks (DSBs) by the non-homologous end joining (NHEJ) factors, including DNA dependent protein kinase (DNA-PK), Artemis, Ku86, Ku70, DNA ligase IV, XRCC4, XLF, and HMGB1. Currently, it is not clear how these factors are organized inside of the nuclei for recombination. Accumulating studies indicate that the multiple-component DNA replication and RNA transcription machineries are organized as large complexes on the nuclear matrix (NM). Here we show that RAG1, RAG2, and many NHEJ factors are associated with the NM, where they appear to form large complexes and are distributed closely at discrete foci. Ongoing RSS cleavage mainly occurs on the NM in developing B, T lineage cells and HEK293 cells with an artificial recombination system; Purified NMs containing RAG and NHEJ proteins possess the entire enzymatically active recombination system to cleave RSS substrates and generate coding joints in vitro. These results support a novel model that the V(D)J recombination machinery is organized as large complexes anchored on the NM to conduct recombination.