Department of Chemistry and Biochemistry, Price Family Foundation Structural Biology Center, Stephenson Life Sciences Research Center, University of Oklahoma, Norman, OK, United States.
Front Cell Infect Microbiol. 2021 Jan 28;10:619763. doi: 10.3389/fcimb.2020.619763. eCollection 2020.
Bacterial and archaeal CRISPR-Cas systems offer adaptive immune protection against foreign mobile genetic elements (MGEs). This function is regulated by sequence specific binding of CRISPR RNA (crRNA) to target DNA/RNA, with an additional requirement of a flanking DNA motif called the protospacer adjacent motif (PAM) in certain CRISPR systems. In this review, we discuss how the same fundamental mechanism of RNA-DNA and/or RNA-RNA complementarity is utilized by bacteria to regulate two distinct functions: to ward off intruding genetic materials and to modulate diverse physiological functions. The best documented examples of alternate functions are bacterial virulence, biofilm formation, adherence, programmed cell death, and quorum sensing. While extensive complementarity between the crRNA and the targeted DNA and/or RNA seems to constitute an efficient phage protection system, partial complementarity seems to be the key for several of the characterized alternate functions. Cas proteins are also involved in sequence-specific and non-specific RNA cleavage and control of transcriptional regulator expression, the mechanisms of which are still elusive. Over the past decade, the mechanisms of RNA-guided targeting and auxiliary functions of several Cas proteins have been transformed into powerful gene editing and biotechnological tools. We provide a synopsis of CRISPR technologies in this review. Even with the abundant mechanistic insights and biotechnology tools that are currently available, the discovery of new and diverse CRISPR types holds promise for future technological innovations, which will pave the way for precision genome medicine.
细菌和古菌的 CRISPR-Cas 系统提供了针对外来可移动遗传元件 (MGE) 的适应性免疫保护。这种功能受 CRISPR RNA (crRNA) 与靶 DNA/RNA 的序列特异性结合调控，在某些 CRISPR 系统中还需要侧翼 DNA 基序（称为原间隔序列邻近基序 [PAM]）。在这篇综述中，我们讨论了细菌如何利用相同的 RNA-DNA 和/或 RNA-RNA 互补的基本机制来调节两种截然不同的功能：抵御入侵的遗传物质和调节多种生理功能。替代功能的最佳例证是细菌的毒力、生物膜形成、黏附、程序性细胞死亡和群体感应。虽然 crRNA 与靶向 DNA 和/或 RNA 之间的广泛互补似乎构成了有效的噬菌体保护系统，但部分互补似乎是几种已描述的替代功能的关键。Cas 蛋白还参与序列特异性和非特异性 RNA 切割以及转录调节因子表达的调控，其机制仍不清楚。在过去的十年中，RNA 引导靶向和几种 Cas 蛋白的辅助功能的机制已转化为强大的基因编辑和生物技术工具。我们在这篇综述中概述了 CRISPR 技术。即使目前有丰富的机制见解和生物技术工具，新的和多样化的 CRISPR 类型的发现也为未来的技术创新提供了希望，这将为精准基因组医学铺平道路。
