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bioRxiv · 10.1101/2020.06.24.163345

Structures of the Cmr-βComplex Reveal the Regulation of the Immunity Mechanism of Type III-B CRISPR-Cas

Sofos, N.·Feng, M.·Stella, S.·Pape, T.·Fuglsgang, A.·Lin, J.·Huang, Q.·Li, Y.·She, Q.·Montoya, G.
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Abstract

Cmr-{beta} is a Type III-B CRISPR-Cas complex that upon target RNA recognition unleashes a multifaceted immune response against invading genetic elements, including ssDNA cleavage, cyclic oligoadenylate synthesis, and also a unique UA-specific ssRNA hydrolysis by the Cmr2 subunit. Here, we present the structure-function relationship of Cmr-{beta} unveiling how binding of the target RNA regulates the Cmr2 activities. CryoEM analysis revealed the unique subunit architecture of Cmr-{beta} and captured the complex in different conformational stages of the immune response, including the non-cognate and cognate target-RNA bound complexes. The binding of the target RNA induces a conformational change of Cmr2, which together with the complementation between the 5-handle in the crRNA and the 3-antitag of the target RNA, activate different configurations in a unique loop of the Cmr3 subunit, which acts as an allosteric sensor signaling the self vs. non-self recognition. These findings highlight the diverse defense strategies of Type III complexes.

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Sofos, N., Feng, M., Stella, S., Pape, T., Fuglsgang, A., Lin, J., Huang, Q., Li, Y., She, Q., Montoya, G.. 2020-06-24. Structures of the Cmr-βComplex Reveal the Regulation of the Immunity Mechanism of Type III-B CRISPR-Cas. https://doi.org/10.1101/2020.06.24.163345

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