Transposon-encoded CRISPR–Cas systems direct RNA-guided DNA integration
Conventional CRISPR–Cas systems maintain genomic integrity by leveraging guide RNAs for the nuclease-dependent degradation of mobile genetic elements, including plasmids and viruses. Here we describe a remarkable inversion of this paradigm, in which bacterial Tn7-like transposons have co-opted nuclease-deficient CRISPR–Cas systems to catalyze RNA-guided integration of mobile genetic elements into the genome. Programmable transposition of Vibrio cholerae Tn6677 in E. coli requires CRISPR- and transposon-associated molecular machineries, including a novel co-complex between Cascade and the transposition protein TniQ. Donor DNA integration occurs in one of two possible orientations at a fixed distance downstream of target DNA sequences, and can accommodate variable length genetic payloads. Deep sequencing experiments reveal highly specific, genome-wide DNA integration across dozens of unique target sites. This work provides the first example of a fully programmable, RNA-guided integrase and lays the foundation for genomic manipulations that obviate the requirements for double-strand breaks and homology-directed repair.