The RAG proteins and V(D)J recombination: complexes, ends, and transposition.

Area of Science:

• Molecular Biology
• Immunology
• Genetics

Background:

• V(D)J recombination is a crucial process for adaptive immunity, generating diverse antibody and T-cell receptor genes.
• The recombination-activating gene (RAG) proteins, RAG1 and RAG2, are essential for initiating this process through DNA cleavage.

Purpose of the Study:

• To review the multifaceted roles of RAG proteins in V(D)J recombination.
• To explore the biochemical mechanisms, protein:DNA interactions, and higher-order complexes involved.
• To discuss the evolutionary implications of RAG proteins as a transposase.

Main Methods:

• Review of existing literature on RAG protein biochemistry and V(D)J recombination.
• Analysis of protein:DNA interactions and DNA cleavage chemistry.
• Comparison with bacterial transposition systems to understand RAG protein function.

Main Results:

• RAG proteins bind DNA specifically and catalyze DNA cleavage.
• Evidence suggests RAG proteins have post-cleavage roles, including nicking hairpin DNA termini.
• RAG1 and RAG2 function as a transposase, with a proposed active site model involving divalent metal ions.

Conclusions:

• RAG proteins are central to V(D)J recombination, exhibiting complex DNA interactions and catalytic activities.
• The transposase nature of RAG proteins provides evolutionary insights into immune system development.
• A model involving metal ions in the RAG active site explains key catalytic steps.