Characteristic properties of type III CRISPR-Cas systems include recognition of target RNA and the subsequent induction of a multifaceted immune response. This involves sequence-specific cleavage of the target RNA and production of cyclic oligoadenylate (cOA) molecules. Here we report that an exposed seed region at the 3′ end of the crRNA is essential for target RNA binding and cleavage, whereas cOA production requires base pairing at the 5′ end of the crRNA. Moreover, we uncover that the variation in the size and composition of type III complexes within a single host results in variable seed regions. This may prevent escape by invading genetic elements, while controlling cOA production tightly to prevent unnecessary damage to the host. Lastly, we use these findings to develop a new diagnostic tool, SCOPE, for the specific detection of SARS-CoV-2 from human nasal swab samples, revealing sensitivities in the atto-molar range. Type III CRISPR-Cas systems recognize and cleave target RNAs and produce signalling molecules. Here the authors discover that both processes are governed by a flexible seed region, ultimately resulting in SCOPE, a SARSCoV-2 diagnostic assay with atto-molar sensitivity.
【저자키워드】 Assay systems, Infectious-disease diagnostics, CRISPR-Cas systems, 【초록키워드】 SARS-CoV-2, immune response, Variation, Genetic, diagnostic, RNA, sensitivity, cleavage, escape, nasal swab, type III, binding, SARSCoV-2, elements, Recognition, Base pairing, 3′ end, sensitivities, Host, regions, Prevent, flexible, resulting, develop, include, subsequent, recognize, complexes, Type, cleave, CRISPR-Ca, 【제목키워드】 diagnostics, type III, Activation, flexible, CARF, CRISPR-Ca,