Taylor & Francis Group
Browse
krnb_a_1642725_sm2609.docx (2.91 MB)

Cmr3 regulates the suppression on cyclic oligoadenylate synthesis by tag complementarity in a Type III-B CRISPR-Cas system

Download (2.91 MB)
journal contribution
posted on 2019-07-12, 14:31 authored by Tong Guo, Fan Zheng, Zhifeng Zeng, Yang Yang, Qi Li, Qunxin She, Wenyuan Han

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 5ʹ-repeat tag of crRNA and 3ʹ-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 5ʹ-tag and anti-tag (i.e., tag complementarity) could affect the interference activities (DNA cleavage activity and cOA synthesis activity) of Cmr-α, 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 7th nucleotide of crRNA in avoiding autoimmunity. More importantly, mutagenesis of Cmr3α 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.

Funding

This work was supported by the National Natural Science Foundation of China [31771380]; Natur og Univers, Det Frie Forskningsråd [DFF-4181-00274].

History