AcrIIIA1 Is a Protein–RNA Anti-CRISPR Complex That Targets Core Cas and Accessory Nucleases

The authors discovered and characterized AcrIIIA1, the first Type III-A specific anti-CRISPR protein. They showed that AcrIIIA1 bound to Csm2 within the Cas10-Csm effector complex and attenuated Cas10’s DNase activity and second messenger production.