A short peptide at the C terminus is responsible for the nuclear localization of RAG2.

The RAG1 and RAG2 proteins are the lymphoid-specific factors essential for V(D)J recombination, the process that leads to the diversification of antigen receptors on B and T lymphocytes. Nucleolar/nuclear localization of RAG1 is mediated by four basic domains, which are the binding sites for the nuclear transport proteins SRP1 and RCH1, and by a nuclear localization signal (NLS) in the fifth basic domain. The C-terminal region of RAG2 from amino acids (aa) 417 to 484 shows a homology with the PHD domain of other proteins involved in chromatin-mediated gene regulation by protein-protein interactions. Mutations in this domain were shown to be responsible for several diseases and in some case lead to altered subcellular localization of proteins. We found that the C-terminal PHD domain of RAG2 is not responsible for the nuclear localization of the protein. We report here the characterization of a region (aa 491-527) in the C-terminal domain of RAG2, downstream of the putative PHD domain, which directs the nuclear localization of the protein.