Structure of Csx1-cOA4 complex reveals the basis of RNA decay in Type III-B CRISPR-Cas

• Published in: Nature communications Vol. 10; no. 1; pp. 1 - 14
• Main Authors: Molina, Rafael, Stella, Stefano, Feng, Mingxia, Sofos, Nicholas, Jauniskis, Vykintas, Pozdnyakova, Irina, López-Méndez, Blanca, She, Qunxin, Montoya, Guillermo
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 20.09.2019; Nature Publishing Group; Nature Portfolio
• Subjects: 631/337/4041; 631/45/535/1266; 631/535/1258/1259; Activation; Active sites; Allosteric properties; Binding sites; Catalysis; CRISPR; Deactivation; Decay; Degradation; Dimers; Humanities and Social Sciences; multidisciplinary; Nuclease; Phosphodiester bonds; Ribonucleic acid; RNA; Science; Science (multidisciplinary); Trimers
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-12244-z

Type III CRISPR-Cas multisubunit complexes cleave ssRNA and ssDNA. These activities promote the generation of cyclic oligoadenylate (cOA), which activates associated CRISPR-Cas RNases from the Csm/Csx families, triggering a massive RNA decay to provide immunity from genetic invaders. Here we present the structure of Sulfolobus islandicus (Sis) Csx1-cOA 4 complex revealing the allosteric activation of its RNase activity. SisCsx1 is a hexamer built by a trimer of dimers. Each dimer forms a cOA 4 binding site and a ssRNA catalytic pocket. cOA 4 undergoes a conformational change upon binding in the second messenger binding site activating ssRNA degradation in the catalytic pockets. Activation is transmitted in an allosteric manner through an intermediate HTH domain, which joins the cOA 4 and catalytic sites. The RNase functions in a sequential cooperative fashion, hydrolyzing phosphodiester bonds in 5′-C-C-3′. The degradation of cOA 4 by Ring nucleases deactivates SisCsx1, suggesting that this enzyme could be employed in biotechnological applications. Type III CRISPR-Cas RNases from the Csm and Csx families are activated by cyclic oligoadenylates (cOA). Here the authors present the cOA bound Sulfolobus islandicus Csx1 structure, which forms a hexamer and reveal an allosteric mechanism for the activation of Csx1 RNase.