Type II CRISPR-Cas | Cas9

Makarova KS, Haft DH, Barrangou R, et al. (2011). Nature Reviews MicrobiologyCRISPRCCtyperncRNA

CRISPR-Cas systems provide bacteria and archaea with adaptive immunity against invading genetic elements such as phages and plasmids. The Type II CRISPR-Cas9 system, found primarily in pathogenic bacteria, uses a single multidomain protein (Cas9) for interference. Cas9, guided by CRISPR RNA (crRNA) and trans-activating crRNA (tracrRNA), recognizes and cleaves foreign DNA at specific sequences adjacent to PAM motifs. This visualization explores the genomic neighborhoods of Cas9 orthologs across 268 diverse bacterial genomes, revealing the conserved architecture of Type II CRISPR loci including the signature genes cas1, cas2, and csn2, as well as the associated CRISPR arrays. The revolutionary gene-editing capabilities of Cas9 have made it one of the most important biotechnological tools of the 21st century.