Unravelling the structural and mechanistic basis of CRISPR–Cas systems

Bacteria and archaea have evolved sophisticated adaptive immune systems, known as CRISPR-Cas (clustered regularly interspaced short palindromic repeats-CRISPR-associated proteins) systems, which target and inactivate invading viruses and plasmids. Immunity is acquired by integrating short fragments of foreign DNA into CRISPR loci, and following transcription and processing of these loci, the CRISPR RNAs (crRNAs) guide the Cas proteins to...