Core component of the RAG complex, a multiprotein complex that mediates the DNA cleavage phase during V(D)J recombination. V(D)J recombination assembles a diverse repertoire of immunoglobulin and T-cell receptor genes in developing B and T lymphocytes through rearrangement of different V (variable), in some cases D (diversity), and J (joining) gene segments. DNA cleavage by the RAG complex occurs in 2 steps: a first nick is introduced in the top strand immediately upstream of the heptamer, generating a 3'-hydroxyl group that can attack the phosphodiester bond on the opposite strand in a direct transesterification reaction, thereby creating 4 DNA ends: 2 hairpin coding ends and 2 blunt, 5'-phosphorylated ends. In the RAG complex, rag2 is not the catalytic component but is required for all known catalytic activities mediated by RAG1. It probably acts as a sensor of chromatin state that recruits the RAG complex to H3K4me3 (By similarity). Component of the RAG complex composed of core components rag1 and rag2. Expressed within the thymus, liver and spleen in juvenile frogs, and within the thymus and bone marrow of adults. A lower level expression is seen in the ovaries. First detected in the thymus during day 4 of development. Expression then increases in the thymus for at least three weeks. The atypical PHD-type zinc finger recognizes and binds histone H3 trimethylated on 'Lys-4' (H3K4me3). The atypical PHD-type zinc finger also binds various phosphoinositides (By similarity). Belongs to the RAG2 family.