Antiviral Type III CRISPR signalling via conjugation of ATP and AdoMet
Antiviral Type III CRISPR signalling via conjugation of ATP and AdoMet
复制标题
DOI：
10.1101/2023.06.26.546636
复制
发表时间：
2023-06
期刊：
影响因子：
--
通讯作者：
Haotian Chi;Ville Hoikkala;S. Grüschow;S. Graham;S. Shirran;M. F. White
中科院分区：
文献类型：
--
作者：
Haotian Chi;Ville Hoikkala;S. Grüschow;S. Graham;S. Shirran;M. F. White
CRISPR系统在原核世界中广泛存在，提供针对移动的遗传元件（MGE）的适应性免疫1，2。具有特征基因cas 10的III型CRISPR系统使用CRISPR RNA（crRNA）来检测非自身RNA，激活酶Cas 10亚基以直接地（经由整合的HD核酸酶结构域3-5）或间接地（经由环状寡核苷酸（cOA）第二信使的合成来激活多种辅助效应物6-9）防御细胞对抗MGE。III型CRISPR系统的一个子集编码未表征的CorA家族膜蛋白和预测在抗病毒防御中起作用的相关NrN家族磷酸二酯酶。在这里，我们证明了来自脆弱拟杆菌的CorA相关III-B型（Cmr）CRISPR系统在E中表达时提供针对MGE的免疫力。杆菌然而，B。fragilis Cmr在活化时不合成cOA物质，而是通过磷酸二酯键将ATP缀合至S-腺苷甲硫氨酸而产生先前未描述的信号分子SAM-AMP（3 '-腺苷酰-腺苷甲硫氨酸）。一旦合成，SAM-AMP与CorA效应物结合，推测通过破坏膜完整性导致细胞死亡。SAM-AMP被CRISPR相关的磷酸二酯酶或SAM-AMP裂解酶降解，提供类似于cOA特异性环核酸酶的“关闭开关”。因此，SAM-AMP代表了一类新的抗病毒信号传导的第二信使，其可能在不同的细胞环境中发挥不同的作用。
CRISPR systems are widespread in the prokaryotic world, providing adaptive immunity against mobile genetic elements (MGE) 1, 2. Type III CRISPR systems, with the signature gene cas10, use CRISPR RNA (crRNA) to detect non-self RNA, activating the enzymatic Cas10 subunit to defend the cell against MGE either directly, via the integral HD nuclease domain 3–5 or indirectly, via synthesis of cyclic oligonucleotide (cOA) second messengers to activate diverse ancillary effectors 6–9. A subset of type III CRISPR systems encode an uncharacterised CorA-family membrane protein and an associated NrN family phosphodiesterase predicted to function in antiviral defence. Here, we demonstrate that the CorA associated type III-B (Cmr) CRISPR system from Bacteroides fragilis provides immunity against MGE when expressed inE. coli. However, B. fragilis Cmr does not synthesise cOA species on activation, instead generating a previously undescribed sigalling molecule, SAM-AMP (3’-adenylyl-AdoMet) by conjugating ATP to S-adenosyl methionine via a phosphodiester bond. Once synthesised, SAM-AMP binds to the CorA effector, presumably leading to cell death by disruption of the membrane integrity. SAM-AMP is degraded by CRISPR associated phosphodiesterases or a SAM-AMP lyase, providing an “off switch” analogous to cOA specific ring nucleases 10. SAM-AMP thus represents a new class of second messenger for antiviral signalling, which may function in different roles in diverse cellular contexts.