Inhibitors of a gene-editing system called CRISPR–Cas9 could one day provide a safety switch, allowing researchers to halt the system's activity in cells.
CRISPR–Cas9 is a naturally occurring bacterial defence mechanism that scientists have harnessed to alter DNA sequences. Alan Davidson at the University of Toronto in Canada and his colleagues searched for bacterial proteins that block the DNA-slicing Cas9 enzyme from the bacterium Neisseria meningitidis, and found three families of such proteins.
The inhibitors halted CRISPR–Cas9 editing in human cells, suggesting that they could be used to better control genome editing. They could be important if CRISPR–Cas9 is to be used for gene therapy in people, or to edit the genomes of entire populations in the wild.