A Type III CRISPR Ancillary Ribonuclease Degrades Its Cyclic Oligoadenylate Activator
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 cA 4 (cOA consisting of 4 AMP units), but the equivalent enzyme has not been identified in bacteria. We demonstrate that, in Thermus thermophilus HB8 , the uncharacterized protein TTHB144 is a cA 4 -activated HEPN ribonuclease that also degrades its activator. TTHB144 binds and degrades cA 4 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.
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BibTeX
@article{athukoralage2026type,
title = {{A Type III CRISPR Ancillary Ribonuclease Degrades Its Cyclic Oligoadenylate Activator}},
author = {Januka Athukoralage and Shirley Graham and Sabine Grüschow and Christophe Rouillon and Malcolm White},
journal = {Journal of Molecular Biology},
year = {2026},
month = sep,
doi = {10.1016/j.jmb.2019.04.041},
url = {https://hal.science/hal-05769444v1},
note = {CC BY},
}
RIS
TY - JOUR
TI - A Type III CRISPR Ancillary Ribonuclease Degrades Its Cyclic Oligoadenylate Activator
AU - Januka Athukoralage
AU - Shirley Graham
AU - Sabine Grüschow
AU - Christophe Rouillon
AU - Malcolm White
PY - 2026
DA - 2026/09/29
JO - Journal of Molecular Biology
DO - 10.1016/j.jmb.2019.04.041
UR - https://hal.science/hal-05769444v1
AB - 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 cA 4 (cOA consisting of 4 AMP units), but the equivalent enzyme has not been identified in bacteria. We demonstrate that, in Thermus thermophilus HB8 , the uncharacterized protein TTHB144 is a cA 4 -activated HEPN ribonuclease that also degrades its activator. TTHB144 binds and degrades cA 4 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.
SN - 0022-2836
SN - 1089-8638
ER -