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bioRxiv · 10.1101/2024.03.09.584257

Cas1 mediates the interference stage in a phage-encoded CRISPR-Cas system

Zhang, L.·Wang, H.·Zeng, J.·Cao, X.·Gao, Z.·Liu, Z.·Li, F.·Wang, J.·Zhang, Y.·Yang, M.·Feng, Y.
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Abstract

CRISPR-Cas systems are prokaryotic adaptive immune systems against invading phages and other mobile genetic elements, which function in three stages: adaptation, expression and interference. Interestingly, phages were also found to encode CRISPR-Cas systems to antagonize their hosts and establish infection. The Vibrio cholerae-infecting ICP1 phage was the first discovered phage with a functional CRISPR-Cas system against an antiphage region in the host genome. Nevertheless, this system lacks a domain essential for recruitment of helicase-nuclease Cas2/3 during target DNA cleavage, and how this system accomplishes the interference stage remains unknown. Here, surprisingly, we found that Cas1, a highly conserved component known to exclusively work in the adaptation stage, also mediates the interference stage through connecting Cas2/3 to the DNA bound-Cascade (Csy) complex of the ICP1 CRISPR-Cas system. A series of structures of Csy, Csy-dsDNA, Cas1-Cas2/3 and Csy-dsDNA-Cas1-Cas2/3 complexes collectively reveal the whole process of Cas1-mediated target DNA cleavage by the ICP1 CRISPR-Cas system. Together, these data support an unprecedented model in which Cas1 mediates the interference stage in a phage-encoded CRISPR-Cas system and also shed light on a unique model of primed adaptation.

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Zhang, L., Wang, H., Zeng, J., Cao, X., Gao, Z., Liu, Z., Li, F., Wang, J., Zhang, Y., Yang, M., Feng, Y.. 2024-03-11. Cas1 mediates the interference stage in a phage-encoded CRISPR-Cas system. https://doi.org/10.1101/2024.03.09.584257

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