Type I-F CRISPR-Cas provides protection from DNA, but not RNA phages

Abstract

The type I-F CRISPR–Cas system from Pseudomonas aeruginosa (PA14) provides sequence-specific elimination of invading DNA1,2. Recently, a paper published in Cell Research reported that this system targets mRNA through a non-canonical mechanism3. Here, we implement the proposed design rules for generating CRISPR-RNA (crRNA)-guides that target RNA and test whether the proposed RNA-targeting activity provides immunity against RNA phage infection. Our experiments reveal that the type I-F CRISPR system provides protection from DNA, but not RNA phages.