高特异性CRISPR/Cas系统及其Acrs

High specificity CRISPR/Cas system and anti-CRISPR proteins

CRISPR/Cas系统是在细菌和古生菌中发现的一种适应性免疫系统,可以在序列特异性RNA的引导下利用其核酸酶活性效应蛋白或复合物靶向入侵的移动遗传元件(MGEs),从而抵御噬菌体的侵袭。目前,Ⅱ-A型CRISPR/Cas系统作为一种有效的基因编辑手段已被广泛应用。但研究人员发现,与Ⅱ-C型CRISPR/Cas9系统相比,Ⅱ-A型系统具有高特异性,并且其效应蛋白具有较小的相对分子质量。这一特性使其在进行体内基因编辑时更适于通过重组腺病毒相关载体递送。近年来,在噬菌体体内发现了多种可以抑制CRISPR/Cas系统的抗CRISPR蛋白(Acrs)。这为调节或抑制CRISPR/Cas系统效应蛋白的活性,降低基因编辑中的脱靶效应提供了新的策略。本文综述了Ⅱ-C型CRISPR/Cas系统及其抑制蛋白的结构和机制的研究进展,并简要概述其余已报道Acrs蛋白的作用机制,以期为Ⅱ-C型CRISPR/Cas系统及在基因编辑甚至基因治疗方面的研究和应用提供理论支持和参考。

The CRISPR/Cas system is an adaptive immune system found in bacteria and archaea,which can target invade mobile genetic elements(MGEs)to protect against phages using the effect protein or compounds with nuclease activity under the guidance of sequence specific RNA.Currently,typeⅡ-A CRISPR/Cas9 system has been widely used as an effective gene editing strategy,but researchers found that typeⅡ-C CRISPR/Cas9 system has lower off-target effect and smaller molecular weight effect proteins than typeⅡ-A system which make it easier to apply to gene editing in vivo.Moreover,several anti-CRISPR proteins(Acrs)that can inhibit the CRISPR/Cas system have been found in phages,which provides a new strategy to regulate the activity and reduce the off-target effect of CRISPR/Cas system.This review will summarize the research progress of typeⅡ-C CRISPR/Cas9 system and its inhibitory proteins in structure and mechanism,and briefly summarize the mechanism of the rest Acrs to provide theoretical support for the research and application of typeⅡ-C CRISPR/Cas9 system in gene editing or even gene therapy.