The effect of crRNA-target mismatches on cOA-mediated interference by a type III-A CRISPR-Cas system

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Date
2022
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Taylor & Francis
Abstract

CRISPR systems elicit interference when a foreign nucleic acid is detected by its ability to base-pair to crRNA. Understanding what degree of complementarity between a foreign nucleic acid and crRNA is required for interference is a central question in the study of CRISPR systems. A clear description of which target-crRNA mismatches abrogate interference in type III, Cas10-containing, CRISPR systems has proved elusive due to the complexity of the system which utilizes three distinct interference activities. We characterized the effect of target-crRNA mismatches on in vitro cyclic oligoadenylate (cOA) synthesis and in vivo in an interference assay that depends on cOA synthesis. We found that sequence context affected whether a mismatched target was recognized by crRNA both in vitro and in vivo. We also investigated how the position of a mismatch within the target-crRNA duplex affected recognition by crRNA. Our data provide support for the hypothesis that a Cas10-activating region exists in the crRNA-target duplex, that the Cas10-proximal region of the duplex is the most critical in regulating cOA synthesis. Understanding the rules governing target recognition by type III CRISPR systems is critical: as one of the most prevalent CRISPR systems in nature, it plays an important role in the survival of many genera of bacteria. Recently, type III systems were re-purposed as a sensitive and accurate molecular diagnostic tool. Understanding the rules of target recognition in this system will be critical as it is engineered for biotechnology purposes.

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Keywords
CRISPR-Cas, crRNA, Cas10-Csm, cyclic oligoadenylates, bacterial immunity, CSM COMPLEX, OFF-TARGET, SPECIFICITY, ENDONUCLEASE, RECOGNITION, IMMUNITY, PROTEIN, Biochemistry & Molecular Biology
Citation
Nasef, M., Khweis, S. A., & Dunkle, J. A. (2022). The effect of crRNA–target mismatches on cOA-mediated interference by a type III-A CRISPR-Cas system. In RNA Biology (Vol. 19, Issue 1, pp. 1293–1304). Informa UK Limited. https://doi.org/10.1080/15476286.2022.2150812