Catalytic 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. In the RAG complex, RAG1 mediates the DNA-binding to the conserved recombination signal sequences (RSS) and catalyzes the DNA cleavage activities by introducing a double-strand break between the RSS and the adjacent coding segment. RAG2 is not a catalytic component but is required for all known catalytic activities. DNA cleavage 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. The chromatin structure plays an essential role in the V(D)J recombination reactions and the presence of histone H3 trimethylated at 'Lys-4' (H3K4me3) stimulates both the nicking and haipinning steps. The RAG complex also plays a role in pre-B cell allelic exclusion, a process leading to expression of a single immunoglobulin heavy chain allele to enforce clonality and monospecific recognition by the B-cell antigen receptor (BCR) expressed on individual B-lymphocytes. The introduction of DNA breaks by the RAG complex on one immunoglobulin allele induces ATM-dependent repositioning of the other allele to pericentromeric heterochromatin, preventing accessibility to the RAG complex and recombination of the second allele. In addition to its endonuclease activity, RAG1 also acts as a E3 ubiquitin-protein ligase that mediates monoubiquitination of histone H3. Histone H3 monoubiquitination is required for the joining step of V(D)J recombination. Mediates polyubiquitination of KPNA1. Homodimer. Component of the RAG complex composed of core components RAG1 and RAG2, and associated component HMGB1 or HMGB2. Maturing lymphoid cells. Belongs to the RAG1 family. Note: This description may include information from UniProtKB.
Protein type: EC 3.1.-.-; DNA binding protein; EC 18.104.22.168; Ubiquitin conjugating system; Ligase; Ubiquitin ligase; EC 6.3.2.-
Cellular Component: nucleus
Molecular Function: protein binding; protein homodimerization activity; DNA binding; zinc ion binding; histone binding; sequence-specific DNA binding; endonuclease activity; metal ion binding; ubiquitin-protein ligase activity
Biological Process: histone monoubiquitination; adaptive immune response; protein autoubiquitination; V(D)J recombination; thymus development; B cell differentiation; pre-B cell allelic exclusion; T cell differentiation in the thymus; immune response; regulation of T cell differentiation; T cell homeostasis; negative regulation of caspase activity; DNA recombination
SS: The number of records in which this modification site was determined using site-specific methods. SS methods include amino acid sequencing, site-directed mutagenesis, modification site-specific antibodies, specific MS strategies, etc.