Tetramerisation of the CRISPR ring nuclease Csx3 facilitates cyclic oligoadenylate cleavage
Tetramerisation of the CRISPR ring nuclease Csx3 facilitates cyclic oligoadenylate cleavage
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DOI：
10.1101/2020.04.28.066118
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发表时间：
2020-04
期刊：
影响因子：
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通讯作者：
Januka S. Athukoralage;S. McQuarrie;S. Grüschow;S. Graham;T. Gloster;M. F. White
中科院分区：
文献类型：
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作者：
Januka S. Athukoralage;S. McQuarrie;S. Grüschow;S. Graham;T. Gloster;M. F. White
III型CRISPR系统检测外源RNA并激活Cas10亚基的环化酶结构域，产生环寡腺苷酸（cOA）分子，作为感染信号的第二信使，激活核酸酶，降解入侵者和宿主的核酸。这可能导致休眠或细胞死亡；为了避免这种情况，一旦病毒感染被击败，细胞需要一种方法从细胞中去除辅酶a。专门用于这项任务的酶被称为环核酸酶，但它们的分布有限。在这里，我们证明了广泛存在的CRISPR相关蛋白Csx3，以前被描述为RNA死基化酶，是一种快速降解环四腺苷酸（cA4）的环核酸酶。该酶具有一种不同寻常的协同反应机制，其活性位点跨越两个二聚体之间的界面，夹住cA4底物。我们建议将Csx3家族命名为Crn3 （CRISPR相关环核酸酶3）。
Type III CRISPR systems detect foreign RNA and activate the cyclase domain of the Cas10 subunit, generating cyclic oligoadenylate (cOA) molecules that act as a second messenger to signal infection, activating nucleases that degrade the nucleic acid of both invader and host. This can lead to dormancy or cell death; to avoid this, cells need a way to remove cOA from the cell once a viral infection has been defeated. Enzymes specialised for this task are known as ring nucleases, but are limited in their distribution. Here, we demonstrate that the widespread CRISPR associated protein Csx3, previously described as an RNA deadenylase, is a ring nuclease that rapidly degrades cyclic tetra-adenylate (cA4). The enzyme has an unusual cooperative reaction mechanism involving an active site that spans the interface between two dimers, sandwiching the cA4 substrate. We propose the name Crn3 (CRISPR associated ring nuclease 3) for the Csx3 family.