Structure-function insights into the initial step of DNA integration by a CRISPR-Cas-Transposon complex
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摘要:
Dear Editor,
CRISPR (clustered regularly interspaced short palindromic repeats)-Cas (CRISPR-associated genes) surveillance complexes are RNA-based adaptive immune systems employed by prokaryotes against invading nucleic acids from bacteriophages and plasmids.1,2 The CRlSPR-derived RNAs (crRNAs) guide the Cas effector complex to target and degrade the invading nucleic acids.Recently,bioinformatics analyses have revealed the presence of CRISPR-Cas loci in bacterial Tn7-like transposons,thereby implicating a functional relationship between RNA-guided DNA targeting and transposition,with the latter representing a new role unrelated to host defense.3 Support for this concept has emerged from recent functional studies on type I-F and type V-K effectors involved in sequence-specific DNA transposition,4,5 thereby significantly broadening the potential biological applications of CRISPR-Cas technology.To complement the available functional studies,our efforts have focused on structural studies of the Vibrio cholerae Tn6677 multi-subunit type I-F CascadeCrRNA-TniQ complex,whereby transposition subunit TniQ initiates DNA transposition with the eventual help of other transposition-associated proteins TnsA,TnsB and TnsC in the gene cluster (Fig.1a).