V(D)J Recombination: Mechanisms of Initiation

Abstract

V(D)J recombination assembles immunoglobulin and T cell receptor genes during lymphocyte development through a series of carefully orchestrated DNA breakage and rejoining events. DNA cleavage requires a series of protein-DNA complexes containing the RAG1 and RAG2 proteins and recombination signals that flank the recombining gene segments. In this review, we discuss recent advances in our understanding of the function and domain organization of the RAG proteins, the composition and structure of RAG-DNA complexes, and the pathways that lead to the formation of these complexes. We also consider the functional significance of RAG-mediated histone recognition and ubiquitin ligase activities, and the role played by RAG in ensuring proper repair of DNA breaks made during V(D)J recombination. Finally, we propose a model for the formation of RAG-DNA complexes that involves anchoring of RAG1 at the recombination signal nonamer and RAG2-dependent surveillance of adjoining DNA for suitable spacer and heptamer sequences.

Single-molecule analysis of RAG-mediated V(D)J DNA cleavage

“…Interestingly, we find that the synaptic complex has a mean lifetime of roughly 400 s and that its formation is readily reversible, with only ∼40% of observed synapses resulting in cleavage at consensus RSS binding sites. (1). Adjacent to the V, D, and J gene segments are recombination signal sequences (RSSs) consisting of a conserved heptamer (consensus 5′-CACAGTG-3′) and nonamer (consensus 5′-ACAAAAACC-3′) separated by a spacer of 12 or 23 bp (referred to as 12RSS and 23RSS, respectively).…”

“…The hairpin is created by nucleophilic attack on the opposing strand by the 3′ hydroxyl group at the nick in a transesterification reaction. After RAG1/2 forms hairpins, it recruits the nonhomologous end joining machinery to repair the ends (1,2). Since their discovery, the full-length RAG1 and RAG2 proteins have proven difficult to isolate and study in vitro (1).…”

“…After RAG1/2 forms hairpins, it recruits the nonhomologous end joining machinery to repair the ends (1,2). Since their discovery, the full-length RAG1 and RAG2 proteins have proven difficult to isolate and study in vitro (1). However, core domains (referred to as RAG1c and RAG2c) have been identified by removing a large region from the N terminus of RAG1 (which includes an E3 ubiquitin ligase domain) and a large region from the C terminus of RAG2 (which includes a plant homeodomain) (3,4).…”

Paralogie et redondance : maintenir l’intégrité du génome au cours de la recombinaison V(D)J

“…Elle est initiée par la formation de DSB induites par la nucléase RAG1/2 au niveau des séquences signal de recombinaison (RSS) qui flanquent les segments codants V, D et J [2]. Les DSB sont alors rapidement reconnues par la voie de réponse aux dommages de l'ADN (DDR, DNA damage response) qui dépend en grande partie de la protéine kinase ATM (ataxiatelangiectasia mutated) [3].…”

Characterization of the B-cell receptor repertoires in peanut allergic subjects undergoing oral immunotherapy

“…BCRs are a heterodimeric protein complex, composed of two identical heavy-chain (IGH) and two identical light-chain proteins [1,2]. BCR genes consist of multiple distinct gene segments corresponding to the variable (V), diversity (D, only for IGH genes), and joining (J) regions, and undergo sitespecific V(D)J recombination [3,4]. During the recombination, random deletion and/or non-templated insertion at the junction site occurred and this process significantly increases the BCR diversity; within this rearranged protein, a complementarity-determining region 3 (CDR3) is considered to be critical for antigen recognition.…”