Anti-CRISPR Loci | Aca5

Pinilla-Redondo R, Shehreen S, Marino ND, et al. (2020). Nature CommunicationsAnti-CRISPRAntidefense Finder

Anti-CRISPR (Acr) proteins are phage-encoded inhibitors that allow mobile genetic elements to evade CRISPR-Cas immunity. Aca5 is an Acr-associated protein found downstream of acr loci that serves as a marker for discovering new anti-CRISPR genes in Enterobacteriaceae. This visualization explores the genomic neighborhoods of Aca5 homologs, revealing the clustering of multiple anti-defense genes within prophages and conjugative elements. The study uncovered 11 new type I-F and I-E anti-CRISPR families, demonstrating how MGEs accumulate diverse immune evasion strategies in "anti-defense islands."