AcrIF9 tethers non-sequence specific dsDNA to the CRISPR RNA-guided surveillance complex
- Hirschi, Marscha
- Lu, Wang-Ting
- Santiago-Frangos, Andrew [ Montana State University: Microbiology & Cell Biology ]
- Wilkinson, Royce [ Montana State University: Microbiology & Cell Biology ]
- Golden, Sarah M. [ Montana State University: Microbiology & Cell Biology ]
- Davidson, Alan R.
- Lander, Gabriel C.
- Wiedenheft, Blake [ Montana State University: Microbiology & Cell Biology ]
Bacteria have evolved sophisticated adaptive immune systems, called CRISPR-Cas, that provide sequence-specific protection against phage infection. In turn, phages have evolved a broad spectrum of anti-CRISPRs that suppress these immune systems. Here we report structures of anti-CRISPR protein IF9 (AcrIF9) in complex with the type I-F CRISPR RNA-guided surveillance complex (Csy). In addition to sterically blocking the hybridization of complementary dsDNA to the CRISPR RNA, our results show that AcrIF9 binding also promotes non-sequence-specific engagement with dsDNA, potentially sequestering the complex from target DNA. These findings highlight the versatility of anti-CRISPR mechanisms utilized by phages to suppress CRISPR-mediated immune systems.