ISTOCK, MOLEKUULTo minimize the off-target effects of CRISPR-based genome editing, researchers have designed a version of Cas9, the enzyme that cuts DNA, that avoids mistakes with unprecedented precision. Mutating one piece of the nuclease, called REC3, reduced off-target effects to below that of other high-fidelity Cas9 enzymes.
“If you mutate certain amino acid residues in REC3, you can tweak the balance between Cas9 on-target activity and improved specificity,” coauthor Janice Chen, a graduate student in Jennifer Doudna’s lab at the University of California, Berkeley, says in a press release. “We were able to find the sweet spot where there is sufficient activity at the intended target but also a large reduction in off-target events,”
Chen and her colleagues had set out to understand why certain variants of Cas9—namely, eSpCas9(1.1) and SpCas9-HF1—are more specific to their target sequences and make fewer off-target cuts than the natural version. That’s when they identified REC3’s role in sensing the accuracy with which the enzyme binds to an intended stretch of DNA: in the event of a ...
