2v89
From Proteopedia
Crystal structure of RAG2-PHD finger in complex with H3K4me3 peptide at 1.1A resolution
Structural highlights
FunctionRAG2_MOUSE 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. 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 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.[1] [2] [3] [4] [5] [6] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedNuclear processes such as transcription, DNA replication and recombination are dynamically regulated by chromatin structure. Eukaryotic transcription is known to be regulated by chromatin-associated proteins containing conserved protein domains that specifically recognize distinct covalent post-translational modifications on histones. However, it has been unclear whether similar mechanisms are involved in mammalian DNA recombination. Here we show that RAG2--an essential component of the RAG1/2 V(D)J recombinase, which mediates antigen-receptor gene assembly--contains a plant homeodomain (PHD) finger that specifically recognizes histone H3 trimethylated at lysine 4 (H3K4me3). The high-resolution crystal structure of the mouse RAG2 PHD finger bound to H3K4me3 reveals the molecular basis of H3K4me3-recognition by RAG2. Mutations that abrogate RAG2's recognition of H3K4me3 severely impair V(D)J recombination in vivo. Reducing the level of H3K4me3 similarly leads to a decrease in V(D)J recombination in vivo. Notably, a conserved tryptophan residue (W453) that constitutes a key structural component of the K4me3-binding surface and is essential for RAG2's recognition of H3K4me3 is mutated in patients with immunodeficiency syndromes. Together, our results identify a new function for histone methylation in mammalian DNA recombination. Furthermore, our results provide the first evidence indicating that disrupting the read-out of histone modifications can cause an inherited human disease. RAG2 PHD finger couples histone H3 lysine 4 trimethylation with V(D)J recombination.,Matthews AG, Kuo AJ, Ramon-Maiques S, Han S, Champagne KS, Ivanov D, Gallardo M, Carney D, Cheung P, Ciccone DN, Walter KL, Utz PJ, Shi Y, Kutateladze TG, Yang W, Gozani O, Oettinger MA Nature. 2007 Dec 13;450(7172):1106-10. Epub 2007 Nov 21. PMID:18033247[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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