Researchers have discovered a variety of natural proteins called
anti-CRISPRs, which can be used to control gene editing. Anti-CRISPRs
can be used in gene therapy and gene drive systems.

CRISPR-Cas9 is one of the gene-editing tools commonly used by
researchers to cut DNA in a cell's genome at a highly targeted location.
The longer the CRISPRsystem stays active in cells, there is higher the
chance for unintended editing and other side effects. In an article
published by the American Chemical Society, the emerging applications of
anti-CRISPRs were discussed in detail.

To date, over 50 distinct families of anti-CRISPRs have been reported,
which are generally small proteins composed of 50-150 amino acids. These
minuscule proteins have minimal similarities in sequence and structure,
indicating that each may have evolved independently. The first
anti-CRISPR was reported about 10 years ago by Joseph Bondy-Denomy, a
microbiologist who now works at the University of California, San Francisco.

Anti-CRISPR proteins could help put the brakes on gene editing (acs.org)
[cen.acs.org]