Engineered Cas9 could increase PAM targeting, DNA specificity

A study published in Nature showed that using protein evolution methods on Staphylococcus pyogenes Cas9 (CRISPR-associated protein 9) broadened protospacer adjacent motif (PAM) compatibility and increased DNA specificity, suggesting that the engineered enzyme could improve CRISPR-Cas9 genome editing.

Scientists from the Broad Institute of MIT and Harvard and Harvard University used a phage-assisted continuous evolution (PACE) system to rapidly evolve Cas9 variants with accumulated mutations. Unlike previous Cas9 proteins, which can only target 1 out of 16 PAM DNA sequences, the engineered variant xCas9 increased compatibility to 1 of 4 sites...