Inhibition of CRISPR-Cas9 with Bacteriophage Proteins

Cell. 2017 Jan 12;168(1-2):150-158.e10. doi: 10.1016/j.cell.2016.12.009. Epub 2016 Dec 29.

Abstract

Bacterial CRISPR-Cas systems utilize sequence-specific RNA-guided nucleases to defend against bacteriophage infection. As a countermeasure, numerous phages are known that produce proteins to block the function of class 1 CRISPR-Cas systems. However, currently no proteins are known to inhibit the widely used class 2 CRISPR-Cas9 system. To find these inhibitors, we searched cas9-containing bacterial genomes for the co-existence of a CRISPR spacer and its target, a potential indicator for CRISPR inhibition. This analysis led to the discovery of four unique type II-A CRISPR-Cas9 inhibitor proteins encoded by Listeria monocytogenes prophages. More than half of L. monocytogenes strains with cas9 contain at least one prophage-encoded inhibitor, suggesting widespread CRISPR-Cas9 inactivation. Two of these inhibitors also blocked the widely used Streptococcus pyogenes Cas9 when assayed in Escherichia coli and human cells. These natural Cas9-specific "anti-CRISPRs" present tools that can be used to regulate the genome engineering activities of CRISPR-Cas9.

Keywords: CRISPR-Cas; Cas9; Cas9 inhibitor; Listeria monocytogenes; anti-CRISPR; bacteriophage; dCas9; gene editing; prophage.

MeSH terms

  • Bacterial Proteins / antagonists & inhibitors
  • Bacteriophages / metabolism*
  • CRISPR-Associated Protein 9
  • CRISPR-Cas Systems*
  • Endonucleases / antagonists & inhibitors*
  • Escherichia coli
  • Genetic Engineering*
  • HEK293 Cells
  • Humans
  • Listeria monocytogenes / enzymology*
  • Listeria monocytogenes / immunology
  • Listeria monocytogenes / virology
  • Prophages

Substances

  • Bacterial Proteins
  • CRISPR-Associated Protein 9
  • Cas9 endonuclease Streptococcus pyogenes
  • Endonucleases