State Key Laboratory of Agricultural Microbiology and College of Life Science and Technology, Huazhong Agricultural University, 430070 Wuhan, China.
State Key Laboratory of Microbial Technology, Shandong University, Binhai Road 72, Jimo, 266237 Qingdao, China; Danish Archaea Center, Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, Copenhagen Biocenter, 2200 Copenhagen N, Denmark.
Cell Rep. 2020 Sep 15;32(11):108133. doi: 10.1016/j.celrep.2020.108133.
Type III CRISPR-Cas systems initiate an intracellular signaling pathway to confer immunity. The signaling pathway includes synthesis of cyclic oligo-adenylate (cOA) and activation of the RNase activity of type III accessory ribonuclease Csm6/Csx1 by cOA. After the immune response, cOA should be cleared on time to avoid constant cellular RNA degradation. In this study, we find a metal-dependent cOA degradation activity in Sulfolobus islandicus. The activity is associated with the cell membrane and able to accelerate cOA clearance at a high cOA level. Further, we show that a metal-dependent and membrane-associated DHH-DHHA1 family nuclease (MAD) rapidly cleaves cOA and deactivates Csx1 ribonuclease. The cOA degradation efficiency of MAD is much higher than the cellular ring nuclease. However, the subcellular organization may prevent it from degrading nascent cOA. Together, the data suggest that MAD acts as the second cOA degrader after the ring nuclease to remove diffused redundant cOA.
III 型 CRISPR-Cas 系统启动细胞内信号通路以赋予免疫性。该信号通路包括环寡腺苷酸（cOA）的合成以及 cOA 激活 III 型辅助核糖核酸酶 Csm6/Csx1 的核糖核酸酶活性。免疫反应后，cOA 应及时清除，以避免持续的细胞 RNA 降解。在本研究中，我们在 Sulfolobus islandicus 中发现了一种依赖金属的 cOA 降解活性。该活性与细胞膜相关，能够在高 cOA 水平下加速 cOA 清除。此外，我们表明，一种依赖金属和膜相关的 DHH-DHHA1 家族核酸酶（MAD）可快速切割 cOA 并使 Csx1 核糖核酸酶失活。MAD 的 cOA 降解效率远高于细胞环核酶。然而，细胞内的组织可能会阻止其降解新生的 cOA。总之，数据表明 MAD 作为环核酶之后的第二种 cOA 降解酶，可去除扩散的冗余 cOA。
