A phage-encoded anti-CRISPR enables complete evasion of type VI-A CRISPR-Cas immunity

We describe a listeriaphage (LS46) encoding an anti-CRISPR protein (AcrVIA1) that inactivates the type VI-A CRISPR system of Listeria seeligeri. Using genetics, biochemistry, and structural biology, we found that AcrVIA1 interacts with the guide-exposed face of Cas13a, preventing access to the target RNA and the conformational changes required for nuclease activation. Unlike inhibitors of DNA-cleaving Cas nucleases, which cause limited immunosuppression and require multiple infections to bypass CRISPR defenses, a single dose of AcrVIA1 delivered by an individual virion completely dismantles type VI-A CRISPR-mediated immunity.
Source: ScienceNOW - Category: Science Authors: Tags: Biochemistry, Microbiology r-articles Source Type: news