CRISPR-Cas adaptation in Escherichia coli.
CRISPR-Cas adaptation in Escherichia coli.
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DOI：
10.1042/bsr20221198
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发表时间：
2023-03-31
影响因子：
4
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原核生物使用通过重复的规则间隔短回文重复序列和CRISPR相关（CRISPR-Cas）系统介导的适应性免疫来保护免受入侵元件如DNA和质粒的侵害。免疫力是通过从外源核酸（原型间隔区）捕获小DNA片段或间隔区并将其整合到宿主CRISPR基因座中来实现的。CRISPR-Cas免疫的这一步骤被称为“初始CRISPR适应”，需要保守的Cas 1-Cas 2复合物，并且通常由有助于间隔区加工和整合的可变宿主蛋白支持。获得新间隔区的细菌在再次感染时对相同的入侵元素具有免疫力。CRISPR-Cas免疫也可以通过整合来自相同入侵元件的新间隔区来更新，这一过程称为“启动适应”。只有正确选择和整合的间隔区在CRISPR免疫的下一个步骤中起作用，当它们的加工转录物用于RNA引导的靶识别和干扰（靶降解）时。以正确的方向捕获、修剪和整合新的间隔区是适应所有CRISPR-Cas系统的通用步骤，但一些细节是CRISPR-Cas类型特异性和物种特异性的。在这篇综述中，我们概述了大肠杆菌中CRISPR-Cas 1类I-E适应的机制，作为已详细研究的适应过程（DNA捕获和整合）的一般模型。我们专注于参与适应的宿主非Cas蛋白的作用，特别是同源重组的作用。
Prokaryotes use the adaptive immunity mediated via the Clustered Regularly Interspaced Short Palindromic Repeats and CRISPR associated (CRISPR-Cas) system for protection against invading elements such as phages and plasmids. The immunity is achieved by capturing small DNA fragments or spacers from foreign nucleic acids (protospacers) and integrating them into the host CRISPR locus. This step of CRISPR-Cas immunity called ‘naïve CRISPR adaptation’ requires the conserved Cas1–Cas2 complex and is often supported by variable host proteins that assist in spacer processing and integration. Bacteria that have acquired new spacers become immune to the same invading elements when reinfected. CRISPR-Cas immunity can also be updated by integrating new spacers from the same invading elements, a process called ‘primed adaptation’. Only properly selected and integrated spacers are functional in the next steps of CRISPR immunity when their processed transcripts are used for RNA-guided target recognition and interference (target degradation). Capturing, trimming, and integrating new spacers in the correct orientation are universal steps of adaptation to all CRISPR-Cas systems, but some details are CRISPR-Cas type-specific and species-specific. In this review, we provide an overview of the mechanisms of CRISPR-Cas class 1 type I-E adaptation in Escherichia coli as a general model for adaptation processes (DNA capture and integration) that have been studied in detail. We focus on the role of host non-Cas proteins involved in adaptation, particularly on the role of homologous recombination.