6dbq

Publication Abstract from PubMed

The mechanism for initiating DNA cleavage by DDE-family enzymes, including the RAG endonuclease, which initiates V(D)J recombination, is not well understood. Here we report six cryo-EM structures of zebrafish RAG in complex with one or two intact recombination signal sequences (RSSs), at up to 3.9-A resolution. Unexpectedly, these structures reveal DNA melting at the heptamer of the RSSs, thus resulting in a corkscrew-like rotation of coding-flank DNA and the positioning of the scissile phosphate in the active site. Substrate binding is associated with dimer opening and a piston-like movement in RAG1, first outward to accommodate unmelted DNA and then inward to wedge melted DNA. These precleavage complexes show limited base-specific contacts of RAG at the conserved terminal CAC/GTG sequence of the heptamer, thus suggesting conservation based on a propensity to unwind. CA and TG overwhelmingly dominate terminal sequences in transposons and retrotransposons, thereby implicating a universal mechanism for DNA melting during the initiation of retroviral integration and DNA transposition.

DNA melting initiates the RAG catalytic pathway.,Ru H, Mi W, Zhang P, Alt FW, Schatz DG, Liao M, Wu H Nat Struct Mol Biol. 2018 Aug;25(8):732-742. doi: 10.1038/s41594-018-0098-5. Epub, 2018 Jul 30. PMID:30061602^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.