标题：Cmr3 regulates the suppression on cyclic oligoadenylate synthesis by tag complementarity in a Type III-B CRISPR-Cas system
作者：Guo, Tong; Zheng, Fan; Zeng, Zhifeng; Yang, Yang; Li, Qi; She, Qunxin; Han, Wenyuan
作者机构：[Guo, Tong; She, Qunxin] Univ Copenhagen, Danish Archaea Ctr, Dept Biol, Copenhagen N, Denmark.; [Zheng, Fan; Zeng, Zhifeng; Yang, Yang; Li, Qi; Han 更多
通讯作者：Han, WY;Han, WY
通讯作者地址：[Han, WY]Huazhong Agr Univ, State Key Lab Agr Microbiol, Wuhan 430070, Hubei, Peoples R China;[Han, WY]Huazhong Agr Univ, Coll Life Sci & Technol, Wuh 更多
关键词：CRISPR-Cas; III-B Cmr system; autoimmunity avoidance; Cmr3; cOA; synthesis activity; DNA cleavage activity
摘要：Type III CRISPR-Cas systems code for a multi-subunit ribonucleoprotein (RNP) complex that mediates DNA cleavage and synthesizes cyclic oligoadenylate (cOA) second messenger to confer anti-viral immunity. Both immune activities are to be activated upon binding to target RNA transcripts by their complementarity to crRNA, and autoimmunity avoidance is determined by extended complementarity between the 5MODIFIER LETTER PRIME-repeat tag of crRNA and 3MODIFIER LETTER PRIME-flanking sequences of target transcripts (anti-tag). However, as to how the strategy could achieve stringent autoimmunity avoidance remained elusive. In this study, we systematically investigated how the complementarity of the crRNA 5MODIFIER LETTER PRIME-tag and anti-tag (i.e., tag complementarity) could affect the interference activities (DNA cleavage activity and cOA synthesis activity) of Cmr-alpha, a type III-B system in Sulfolobus islandicus Rey15A. The results revealed an increasing suppression on both activities by increasing degrees of tag complementarity and a critical function of the 7(th) nucleotide of crRNA in avoiding autoimmunity. More importantly, mutagenesis of Cmr3 alpha exerts either positive or negative effects on the cOA synthesis activity depending on the degrees of tag complementarity, suggesting that the subunit, coupling with the interaction between crRNA tag and anti-tag, function in facilitating immunity and avoiding autoimmunity in Type III-B systems.