AcrIF5 specifically targets DNA-bound CRISPR-Cas surveillance complex for inhibition

Nat Chem Biol. 2022 Jun;18(6):670-677. doi: 10.1038/s41589-022-00995-8. Epub 2022 Mar 17.

Abstract

CRISPR-Cas systems are prokaryotic antiviral systems, and phages use anti-CRISPR proteins (Acrs) to inactivate these systems. Here we present structural and functional analyses of AcrIF5, exploring its unique anti-CRISPR mechanism. AcrIF5 shows binding specificity only for the target DNA-bound form of the crRNA-guided surveillance (Csy) complex, but not the apo Csy complex from the type I-F CRISPR-Cas system. We solved the structure of the Csy-dsDNA-AcrIF5 complex, revealing that the conformational changes of the Csy complex caused by dsDNA binding dictate the binding specificity for the Csy-dsDNA complex by AcrIF5. Mechanistically, five AcrIF5 molecules bind one Csy-dsDNA complex, which destabilizes the helical bundle domain of Cas8f, thus preventing subsequent Cas2/3 recruitment. AcrIF5 exists in symbiosis with AcrIF3, which blocks Cas2/3 recruitment. This attack on the recruitment event stands in contrast to the conventional mechanisms of blocking binding of target DNA. Overall, our study reveals an unprecedented mechanism of CRISPR-Cas inhibition by AcrIF5.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacteriophages* / genetics
  • Bacteriophages* / metabolism
  • CRISPR-Associated Proteins* / genetics
  • CRISPR-Cas Systems / genetics
  • DNA / metabolism
  • Viral Proteins / chemistry
  • Viral Proteins / genetics
  • Viral Proteins / metabolism

Substances

  • CRISPR-Associated Proteins
  • Viral Proteins
  • DNA