Edit, then shut down

A trio of studies has uncovered two proteins and a new mechanism for curbing off-target activity of CRISPR, providing a route to assuage drug developers and regulators about one of the main safety concerns for the gene editing technology. Unlike other approaches that rely on modifying the CRISPR components to increase specificity, the new system aims to switch off CRISPR before it cuts the wrong regions of the genome.

CRISPR-based gene editing involves a nuclease -- most commonly Cas9 -- that cuts DNA at sites specified by a guide RNA that is co-delivered with the enzyme. The problem is that Cas9 also cleaves other sites, particularly after it has cut its target...