Cas9 senses CRISPR RNA abundance to regulate CRISPR spacer acquisition

Cas9 senses CRISPR RNA abundance to regulate CRISPR spacer acquisition

Prokaryotes create adaptive immune memories by acquiring foreign DNA snippets, known as spacers, into the CRISPR array1. In type II CRISPR-Cas systems, the RNA-guided effector Cas9 also assists the acquisition machinery by selecting spacers from protospacer adjacent motif (PAM)-flanked DNA2,3. Here, we uncover the first biological role for Cas9 that is independent of its dual RNA partners. Following depletion of crRNA and/or tracrRNA, Neisseria …