Sam Sternberg, Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY.

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
transposons have coopted nuclease-deficient CRISPR–Cas systems to catalyze RNA-guided
integration of mobile genetic elements into the genome. Programmable transposition
requires CRISPR- and transposon-associated molecular machineries, including a novel cocomplex
between Cascade and the transposition protein TniQ. Donor DNA integration
occurs at a fixed distance downstream of target DNA sequences, accommodates variable
length genetic payloads, and functions robustly in diverse bacterial species. Deep sequencing
experiments reveal highly specific, genome-wide DNA integration across dozens of unique
target sites. The discovery of a fully programmable, RNA-guided integrase lays the
foundation for kilobase-scale genome engineering that obviates the requirements for DNA
double-strand breaks and homologous recombination.