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bioRxiv · 10.1101/453720

Structure reveals mechanism of CRISPR RNA-guided nuclease recruitment and anti-CRISPR viral mimicry

Rollins, M. F.·Chowdhury, S.·Carter, J.·Golden, S. M.·Miettinen, H. M.·Santiago-Frangos, A.·Faith, D.·Lawrence, C. M.·Lander, G. C.·Wiedenheft, B.
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Abstract

Bacteria and archaea have evolved sophisticated adaptive immune systems that rely on CRISPR RNA (crRNA)-guided detection and nuclease-mediated elimination of invading nucleic acids. Here we present the cryo-EM structure of the type I-F CRISPR RNA-guided surveillance complex (Csy complex) from Pseudomonas aeruginosa bound to a double-stranded DNA target. Comparison of this structure to previously determined structures of this complex reveals a I180-degree rotation of the C-terminal helical bundle on the \"large\" Cas8f subunit. We show that the dsDNA-induced conformational change in Cas8f exposes a Cas2/3 \"nuclease recruitment helix\" that is structurally homologous to a virally encoded anti-CRISPR protein (AcrIF3). Structural homology between Cas8f and AcrIF3 suggests that AcrIF3 is a mimic of the Cas8f \"nuclease recruitment helix\", implying that cas genes may sometimes serve as genetic fodder for the evolution of anti-CRISPRs.

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Rollins, M. F., Chowdhury, S., Carter, J., Golden, S. M., Miettinen, H. M., Santiago-Frangos, A., Faith, D., Lawrence, C. M., Lander, G. C., Wiedenheft, B.. 2018-10-26. Structure reveals mechanism of CRISPR RNA-guided nuclease recruitment and anti-CRISPR viral mimicry. https://doi.org/10.1101/453720

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