Figure 1. V(D)J recombination in developing lymphocytes requires the RAG endonuclease and C-NHEJ factors.
This Figure depicts an example of a V(D)J recombination event occurring between a V gene segment and a rearranged DJ gene segment to form a complete V-D-J exon.
(A) The RAG1/2 endonuclease (green ovals) is recruited to recombination signal (RS) sequences flanking a “V” gene segment and a “DJ” gene segment. The white triangle represents a 23-RSS, and the black triangle represents a 12-RSS.
(B) After DSB induction, RAG holds hairpin-sealed coding ends and blunt signal ends in a post-cleavage synaptic complex.
(C) The Ku70/Ku80 heterodimer (denoted by the light blue semicircle and dark blue semicircle, respectively) recognizes and binds DNA ends. Hairpin-sealed coding ends require DNA-PKcs (light blue oval) and the nuclease Artemis (red circle) to open and process the hairpins before ligation.
(D) DNA ligase 4 (Lig4, yellow oval) and XRCC4 (orange oval) are recruited to the DNA repair complex in a Ku-dependent manner. XLF (orange circle) is also recruited to the DNA repair complex by Ku.
(E) The XRCC4/Lig4 complex ligates signal ends and coding ends, resulting in signal joins (left) and coding joins (right), respectively.