Download MendeleyStructure and mechanism of the broad spectrum CRISPR-associated ring nuclease Crn4.
Chi, H., Hoikkala, V., McMahon, S., Graham, S., Gloster, T., White, M.F.(2025) Nat Commun 17: 889-889
- PubMed: 41398410 Search on PubMed
- DOI: https://doi.org/10.1038/s41467-025-67607-6
- Primary Citation Related Structures:
9QS9, 9R7B, 9SMA - PubMed Abstract:
Type III CRISPR systems detect the presence of RNA from mobile genetic elements (MGE) in prokaryotes, providing antiviral immunity. On activation, the catalytic Cas10 subunit conjugates ATP to form cyclic oligoadenylate (cOA) signalling molecules that activate ancillary effectors, providing an immune response. Cellular ring nucleases degrade cOA to reset the system. Here, we describe the structure and mechanism of a new family of ring nucleases, Crn4, associated with type III-D CRISPR systems. The crystal structure of Crn4 reveals a small homodimeric protein with a fold unrelated to any known ring nuclease or, indeed, any known protein structure. Crn4 degrades a wide range of cOA species to linear oligoadenylates in vitro and ameliorates type III CRISPR immunity in vivo. Phage and plasmids also encode Crn4 orthologues that may function as anti-CRISPRs. These observations expand our understanding of ring nucleases and reveal a new protein fold for cyclic nucleotide recognition.
- School of Biology, University of St Andrews, BMS building, North Haugh, St Andrews, Fife, UK.
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