A DNA mimic jams the Cas9 scissors.

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• CRISPR-Cas systems are microbial adaptive immune mechanisms targeting nucleic acids.
• Anti-CRISPR (Acr) proteins are diverse inhibitors of CRISPR-Cas activity.
• Acr proteins exhibit varied structures and inhibition mechanisms.

Purpose of the Study:

• To characterize the novel AcrIIA13b protein.
• To elucidate the mechanism by which AcrIIA13b inhibits the Cas9 enzyme.

Main Methods:

• Structural analysis of AcrIIA13b.
• Biochemical assays to assess Cas9 inhibition.
• Mutational analysis to identify key residues for DNA mimicry.

Main Results:

• AcrIIA13b was identified as a novel inhibitor of the Cas9 protein.
• Structural and biochemical data revealed AcrIIA13b functions as a DNA mimic.
• AcrIIA13b prevents Cas9 from binding to its DNA target by mimicking DNA.

Conclusions:

• AcrIIA13b represents a new class of anti-CRISPR proteins.
• The DNA mimicry mechanism of AcrIIA13b provides insights into Cas9 regulation.
• Understanding AcrIIA13b's function could inform the development of novel gene-editing tools.