Recruitment of CRISPR-Cas systems by Tn7-like transposons

Significance CRISPR-Cas is an adaptive immunity system that protects bacteria and archaea from mobile genetic elements. We present comparative genomic and phylogenetic analysis of minimal CRISPR-Cas variants associated with distinct families of transposable elements and develop the hypothesis that such repurposed defense systems contribute to the transposable element propagation by facilitating transposition into specific sites. Thus, these transposable elements are predicted to propagate via RNA-guided transposition, a mechanism that has not been previously described for DNA transposons.