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bioRxiv · 10.1101/582114

A type III CRISPR ancillary ribonuclease degrades its cyclic oligoadenylate activator

Athukoralage, J. S.·Graham, S.·Grueschow, S.·Rouillon, C.·White, M. F.
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Abstract

Cyclic oligoadenylate (cOA) secondary messengers are generated by type III CRISPR systems in response to viral infection. cOA allosterically activates the CRISPR ancillary ribonucleases Csx1/Csm6, which degrade RNA non-specifically using a HEPN (Higher Eukaryotes and Prokaryotes, Nucleotide binding) active site. This provides effective immunity, but can also lead to growth arrest in infected cells, necessitating a means to deactivate the ribonuclease once viral infection has been cleared. In the crenarchaea, dedicated ring nucleases degrade cA4 (cOA consisting of 4 AMP units), but the equivalent enzyme has not been identified in bacteria. We demonstrate that, in Thermus thermophilus HB8, the uncharacterised protein TTHB144 is a cA4-activated HEPN ribonuclease that also degrades its activator. TTHB144 binds and degrades cA4 at an N-terminal CARF (CRISPR Associated Rossman Fold) domain. The two activities can be separated by site-directed mutagenesis. TTHB144 is thus the first example of a self-limiting CRISPR ribonuclease.\n\n\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=98 SRC=\"FIGDIR/small/582114_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (21K):\norg.highwire.dtl.DTLVardef@d4ac46org.highwire.dtl.DTLVardef@7a67b0org.highwire.dtl.DTLVardef@2d8c7aorg.highwire.dtl.DTLVardef@61b12a_HPS_FORMAT_FIGEXP M_FIG Graphical abstract C_FIG

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Athukoralage, J. S., Graham, S., Grueschow, S., Rouillon, C., White, M. F.. 2019-03-20. A type III CRISPR ancillary ribonuclease degrades its cyclic oligoadenylate activator. https://doi.org/10.1101/582114

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