There's a way to turn off CRISPR-Cas9 and researchers uncovered it by going over the same bacteria and viruses that led to the gene-editing system's development in the first place.

In a study published in the journal Cell, researchers detailed identifying anti-CRISPR proteins produced by bacterial viruses, coming up with a technique that will benefit CRISPR by making clinical and research applications of the gene-editing system safer and more accurate.

Many are throwing their hopes behind CRISPR as it has a number of uses but gene editing is not yet precise enough, leading to unintended edits along the way. CRISPR is also easy to use, opening up the possibility that the system could bring harm, whether accidental or intentional.

Anti-CRISPR Proteins

The anti-CRISPR proteins Benjamin Rauch, Ph.D. and colleagues identified are the first to directly work against the CRISPR-Cas9 gene-editing system most commonly used in labs today. The researchers examined almost 300 Listeria strains to find them and discovered that 3 percent of the strains they were looking at had a "self-targeting" ability. Further research led to the isolation of four anti-CRISPR proteins that can block Listeria Cas9 activity. Listeria Cas9 is similar to SpyCas9, the protein the CRISPR-Cas9 gene-editing system uses as a targeted DNA clipper.

Then out of the four anti-CRISPR proteins, two were singled out for their ability to inhibit an action used by SpyCas9 in targeting specific genes in bacteria and engineered human cells. The researchers then zeroed in on AcrIIA proteins as being the most potent in inhibiting the CRISPR-Cas9 gene-editing system.

"The next step is to show in human cells that using these inhibitors can actually improve the precision of gene editing by reducing off-target effects," said Rauch.

The Importance Of A CRISPR Off Switch

According to the researchers, having the option to deactivate SpyCas9 will improve gene editing precision and safety by addressing the ongoing issue of unintended modifications, which grow in likelihood the longer CRISPR stays active within target cells.

It will also be beneficial to those using newer CRISPR techniques that rely on Cas9 to tune up or down activity. With the anti-CRISPR proteins, gene activity can be boosted or blocked temporarily, offering the opportunity to synchronize activity for interconnected genes, which could play a role in the study and treatment of multi-gene diseases.

And should anything untoward occur during the course of intentional gene editing, the anti-CRISPR proteins can be used to quickly halt the system, offering a safeguard that could allow for the technology to be more safely explored.

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