Department of Biology, University of Copenhagen, Copenhagen N, Denmark.
Department of Biology, University of Copenhagen, Copenhagen N, Denmark.
Trends Microbiol. 2020 Nov;28(11):913-921. doi: 10.1016/j.tim.2020.05.007. Epub 2020 Jun 1.
Anti-CRISPR (Acr) proteins are natural inhibitors of CRISPR-Cas immune systems. To date, Acrs inhibiting types I, II, III, V, and VI CRISPR-Cas systems have been characterized. While most known Acrs are derived from bacterial phages and prophages, very few have been characterized in the domain Archaea, despite the nearly ubiquitous presence of CRISPR-Cas in archaeal cells. Here we summarize the discovery and characterization of the archaeal Acrs with the representatives encoded by a model archaeal virus, Sulfolobus islandicus rod-shaped virus 2 (SIRV2). AcrID1 inhibits subtype I-D CRISPR-Cas immunity through direct interaction with the large subunit Cas10d of the effector complex, and AcrIIIB1 inhibits subtype III-B CRISPR-Cas immunity through a mechanism interfering with middle/late gene targeting. Future development of efficient screening methods will be key to uncovering the diversity of archaeal Acrs.
抗 CRISPR（Acr）蛋白是 CRISPR-Cas 免疫系统的天然抑制剂。迄今为止，已鉴定出抑制 I 型、II 型、III 型、V 型和 VI 型 CRISPR-Cas 系统的 Acr。虽然大多数已知的 Acr 来源于细菌噬菌体和前噬菌体，但在古菌域中仅鉴定出极少数 Acr，尽管 CRISPR-Cas 在古菌细胞中几乎普遍存在。在这里，我们总结了具有模型古菌病毒——嗜热硫化叶菌棒状病毒 2（SIRV2）编码的代表的古菌 Acr 的发现和特征。AcrID1 通过与效应复合物的大亚基 Cas10d 直接相互作用抑制 I-D 型 CRISPR-Cas 免疫，而 AcrIIIB1 通过干扰中/晚期基因靶向的机制抑制 III-B 型 CRISPR-Cas 免疫。开发有效的筛选方法将是揭示古菌 Acr 多样性的关键。
