Anti-CRISPR: A defense strategy of bacteriophages against bacteria

Abstract

Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-Cas system is a sequence-specific adaptive immune strategy, widespread across prokaryotic systems conferring innate immunity against various bacteriophages and other MGEs like plasmids, genomic islands, integrative and conjugative elements. Even with the presence of such a sophisticated mechanism, the bacteria haven’t been always completely victorious against phages. This is due to Anti-CRISPR proteins produced by bacteriophages and other MGEs. Since their discovery in 2013, more than 60 Acr families have been identified to date and many more are yet to be known. Studies revealed diverse mechanisms adopted by Acrs through which they mediate their control over CRISPR defense system. With the development in this area, Acrs can be harnessed as potential control strategies for CRISPR-Cas technology. In this review, we focus on the discovery of various Anti-CRISPR proteins, their mechanism of action through which they can counteract the bacterial CRISPR-Cas system, and the potential applications of Acrs in gene editing and gene therapy technologies.