TY - JOUR
T1 - AcrIIIA1 is a protein–RNA anti-CRISPR complex that targets core Cas and accessory nucleases
AU - Chou-Zheng, Lucy
AU - Howell, Olivia
AU - Boyle, Tori A
AU - Hossain, Motaher
AU - Walker, Forrest C
AU - Sheriff, Emma K
AU - Aslan, Barbaros
AU - Hatoum-Aslan, Asma
N1 - U.S. National Science Foundation (NSF) [2054755 to A.H.-A]; Burroughs Wellcome Fund [1020298to A.H.-A.]; National Institutes of Health (NIH) Division of Intramural Research [1R01AI173022 to A.H.-A.]. Funding for open access charge: NIH [1R01AI173022].
PY - 2024/12/11
Y1 - 2024/12/11
N2 - Clustered regularly-interspaced short palindromic repeats (CRISPRs) and CRISPR-associated (Cas) proteins protect bacteria and archaea from their viruses, and anti-CRISPRs (Acrs) are small virus-encoded proteins that inhibit CRISPR-Cas immunity. Over 80 families of Acrs have been described to date; however, only three of these subvert Type III CRISPR-Cas immunity. Type III systems employ a complex network of Cas and accessory nucleases to degrade viral nucleic acids. Here, we discover and characterize AcrIIIA1, the first Type III-A specific anti-CRISPR protein. We demonstrate that AcrIIIA1 binds to Csm2 within the Cas10-Csm effector complex and attenuates Cas10’s DNase activity and second messenger production. Additionally, AcrIIIA1 associates with fragmented t(m)RNAs (acrIIIA1-RNAs), and we show that they co-purify with the Cas10-Csm complex during phage infection. Although the precise role(s) of acrIIIA1-RNAs remain unclear, we found that they bind stably to RNase R, a host-encoded nuclease known to bolster immunity, and RNase R has the capacity to degrade them. Altogether, our results support a model in which AcrIIIA1 and its associated RNAs target both core Cas and accessory nucleases to provide robust protection against Type III CRISPR-Cas immunity.
AB - Clustered regularly-interspaced short palindromic repeats (CRISPRs) and CRISPR-associated (Cas) proteins protect bacteria and archaea from their viruses, and anti-CRISPRs (Acrs) are small virus-encoded proteins that inhibit CRISPR-Cas immunity. Over 80 families of Acrs have been described to date; however, only three of these subvert Type III CRISPR-Cas immunity. Type III systems employ a complex network of Cas and accessory nucleases to degrade viral nucleic acids. Here, we discover and characterize AcrIIIA1, the first Type III-A specific anti-CRISPR protein. We demonstrate that AcrIIIA1 binds to Csm2 within the Cas10-Csm effector complex and attenuates Cas10’s DNase activity and second messenger production. Additionally, AcrIIIA1 associates with fragmented t(m)RNAs (acrIIIA1-RNAs), and we show that they co-purify with the Cas10-Csm complex during phage infection. Although the precise role(s) of acrIIIA1-RNAs remain unclear, we found that they bind stably to RNase R, a host-encoded nuclease known to bolster immunity, and RNase R has the capacity to degrade them. Altogether, our results support a model in which AcrIIIA1 and its associated RNAs target both core Cas and accessory nucleases to provide robust protection against Type III CRISPR-Cas immunity.
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U2 - 10.1093/nar/gkae1006
DO - 10.1093/nar/gkae1006
M3 - Article
C2 - 39551936
SN - 0305-1048
VL - 52
SP - 13490
EP - 13514
JO - Nucleic acids research
JF - Nucleic acids research
IS - 22
M1 - gkae1006
ER -