Regulation of the RNA and DNA nuclease activities required for Pyrococcus furiosus Type III-B CRISPR-Cas immunity
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Type III CRISPR-Cas prokaryotic immune systems provide anti-viral and anti-plasmid immunity via a dual mechanism of RNA and DNA destruction. Upon target RNA interaction, Type III crRNP effector complexes become activated to cleave both target RNA (via Cas7) and target DNA (via Cas10). Moreover, trans-acting endoribonucleases, Csx1 or Csm6, can promote the Type III immune response by destroying both invader and host RNAs. Here, we characterize how the RNase and DNase activities associated with Type III-B immunity in Pyrococcus furiosus (Pfu) are regulated by target RNA features and second messenger signaling events. In vivo mutational analyses reveal that either the DNase activity of Cas10 or the RNase activity of Csx1 can effectively direct successful anti-plasmid immunity. Biochemical analyses confirmed that the Cas10 Palm domains convert ATP into cyclic oligoadenylate (cOA) compounds that activate the ribonuclease activity of Pfu Csx1. Furthermore, we show that the HEPN domain of the adenosine-specific endoribonuclease, Pfu Csx1, degrades cOA signaling molecules to provide an auto-inhibitory off-switch of Csx1 activation. Activation of both the DNase and cOA generation activities require target RNA binding and recognition of distinct target RNA 3' protospacer flanking sequences. Our results highlight the complex regulatory mechanisms controlling Type III CRISPR immunity.
Foster , K , Grüschow , S , Bailey , S , White , M F & Terns , M P 2020 , ' Regulation of the RNA and DNA nuclease activities required for Pyrococcus furiosus Type III-B CRISPR-Cas immunity ' , Nucleic Acids Research , vol. 48 , no. 8 , pp. 4418-4434 . https://doi.org/10.1093/nar/gkaa176
Nucleic Acids Research
Copyright © The Author(s) 2020. Published by Oxford University Press on behalf of Nucleic Acids Research. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
DescriptionFunding: National Institutes of Health (NIH) [R35GM118160 to M.P.T., R01GM097330 to S.B. and 1F31GM125365 toK.F.]; Biotechnology and Biological Sciences Research Council [REF: BB/S000313/1 to M.F.W.]. Funding for open access charge: NIH grant.
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