National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, 8600 Rockville Pike, Bethesda, Maryland 20894, USA.
Nat Rev Microbiol. 2011 Jun;9(6):467-77. doi: 10.1038/nrmicro2577. Epub 2011 May 9.
The CRISPR-Cas (clustered regularly interspaced short palindromic repeats-CRISPR-associated proteins) modules are adaptive immunity systems that are present in many archaea and bacteria. These defence systems are encoded by operons that have an extraordinarily diverse architecture and a high rate of evolution for both the cas genes and the unique spacer content. Here, we provide an updated analysis of the evolutionary relationships between CRISPR-Cas systems and Cas proteins. Three major types of CRISPR-Cas system are delineated, with a further division into several subtypes and a few chimeric variants. Given the complexity of the genomic architectures and the extremely dynamic evolution of the CRISPR-Cas systems, a unified classification of these systems should be based on multiple criteria. Accordingly, we propose a 'polythetic' classification that integrates the phylogenies of the most common cas genes, the sequence and organization of the CRISPR repeats and the architecture of the CRISPR-cas loci.
CRISPR-Cas（成簇规律间隔短回文重复序列-CRISPR 相关蛋白）模块是存在于许多古菌和细菌中的适应性免疫系统。这些防御系统由操纵子编码，这些操纵子具有极其多样的结构，并且 cas 基因和独特间隔子内容的进化速度都非常快。在这里，我们对 CRISPR-Cas 系统和 Cas 蛋白之间的进化关系进行了更新分析。划定了三种主要类型的 CRISPR-Cas 系统，并进一步细分为几个亚型和一些嵌合变体。鉴于基因组结构的复杂性和 CRISPR-Cas 系统极其动态的进化，这些系统的统一分类应该基于多个标准。因此，我们提出了一种“多系”分类法，该分类法整合了最常见的 cas 基因的系统发育、CRISPR 重复序列的序列和组织以及 CRISPR-cas 基因座的结构。
