Structures of the Cmr-beta Complex Reveal the Regulation of the Immunity Mechanism of Type III-B CRISPR-Cas
Structures of the Cmr-beta Complex Reveal the Regulation of the Immunity Mechanism of Type III-B CRISPR-Cas
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Cmr-beta复合物的结构揭示了III-B型CRISPR-Cas免疫机制的调节
DOI：
10.1016/j.molcel.2020.07.008
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发表时间：
2020
期刊：
影响因子：
16
通讯作者：
Montoya Guillermo
中科院分区：
文献类型：
--
作者：
Sofos Nicholas;Feng Mingxia;Stella Stefano;Pape Tillmann;Fuglsang Anders;Lin Jinzhong;Huang Qihong;Li Yingjun;She Qunxin;Montoya Guillermo
Cmr-β是一种III-B型CRISPR-Cas复合物，在靶RNA识别后，释放针对入侵遗传元件的多方面免疫应答，包括单链DNA（ssDNA）切割，环状寡腺苷酸合成，以及Cmr 2亚基的独特UA特异性单链RNA（ssRNA）水解。在这里，我们介绍了Cmr-β的结构-功能关系，揭示了靶RNA的结合如何调节Cmr 2的活性。冷冻电子显微镜（cryo-EM）分析揭示了Cmr-β独特的亚基结构，并在免疫应答的不同构象阶段捕获了复合物，包括非同源和同源靶RNA结合复合物。靶RNA的结合诱导Cmr 2的构象变化，其与CRISPR RNA（crRNA）中的5′标签和靶RNA的3′反标签之间的互补一起激活Cmr 3亚基的独特环中的不同构型，Cmr 3亚基作为变构传感器发出自我识别与非自我识别的信号。这些发现突出了III型复合物的多样防御策略。
Cmr-β is a type III-B CRISPR-Cas complex that, upon target RNA recognition, unleashes a multifaceted immune response against invading genetic elements, including single-stranded DNA (ssDNA) cleavage, cyclic oligoadenylate synthesis, and also a unique UA-specific single-stranded RNA (ssRNA) hydrolysis by the Cmr2 subunit. Here, we present the structure-function relationship of Cmr-β, unveiling how binding of the target RNA regulates the Cmr2 activities. Cryoelectron microscopy (cryo-EM) analysis revealed the unique subunit architecture of Cmr-β 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′ tag in the CRISPR RNAs (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- versus non-self-recognition. These findings highlight the diverse defense strategies of type III complexes.