A virus-made small RNA that mimics guide RNA to block CRISPR-Cas9

A phage-encoded RNA, rAcrIIA1, mimics the CRISPR RNA guide and inhibits CRISPR-Cas9 activity.

• rAcrIIA1 adopts a chimeric structure resembling both crRNA and tracrRNA, mimicking the single-guide RNA used by Cas9.
• Cryo-electron microscopy shows that rAcrIIA1 engages with Cas9 similarly to native sgRNA, blocking the loading of crRNA and tracrRNA.
• The presence of rAcrIIA1 prevents DNA interference by Cas9.
• rAcrIIA1 can be reprogrammed with different guide sequences to direct Cas9 for specific DNA cleavage.
• The efficiency of rAcrIIA1 in directing Cas9 is comparable to that of canonical sgRNA, with enhanced trans-cleavage activity.

Simplified