National Center for Biotechnology Information, National Library of Medicine, 8600 Rockville Pike, Bethesda, MD 20894, USA.
Danish Archaea Centre, Department of Biology, University of Copenhagen, Danish Archaea Centre, Ole Maaloes Vej 5, Copenhagen , DK-2200 Denmark.
FEMS Microbiol Lett. 2019 Apr 1;366(7). doi: 10.1093/femsle/fnz079.
Screening of genomic and metagenomic databases for new variants of CRISPR-Cas systems increasingly results in the discovery of derived variants that do not seem to possess the interference capacity and are implicated in functions distinct from adaptive immunity. We describe an extremely derived putative class 1 CRISPR-Cas system that is present in many Halobacteria and consists of distant homologs of the Cas5 and Cas7 protein along with an uncharacterized conserved protein and various nucleases. We hypothesize that, although this system lacks typical CRISPR effectors or a CRISPR array, it functions as a RNA-dependent defense mechanism that, unlike other derived CRISPR-Cas, utilizes alternative nucleases to cleave invader genomes.
基于基因组和元基因组数据库对 CRISPR-Cas 系统新变体的筛选，不断发现似乎不具有干扰能力且与适应性免疫不同的衍生变体。我们描述了一种存在于许多盐杆菌中的极其衍生的假定的 1 类 CRISPR-Cas 系统，它由 Cas5 和 Cas7 蛋白的远距离同源物以及一个未表征的保守蛋白和各种核酸酶组成。我们假设，尽管该系统缺乏典型的 CRISPR 效应物或 CRISPR 阵列，但它作为一种 RNA 依赖性防御机制发挥作用，与其他衍生的 CRISPR-Cas 不同，它利用替代的核酸酶来切割入侵基因组。
