利用内源CRISPR-Cas系统开展乳酸菌基因编辑的研究进展

Advances in utilizing the endogenous CRISPR-Cas system for genome editing of lactic acid bacteria

摘要:

CRISPR-Cas9技术是一种高效、精准的基因编辑工具,该技术的建立推动基因组编辑进入快速发展阶段。目前应用最广泛的Cas9蛋白是来源于酿脓链球菌(Streptococcuspyogenes)的SpyCas9,该蛋白作为“基因剪刀”在哺乳动物、植物等真核生物中应用较为广泛且成熟,但是该蛋白在一些乳酸菌中的应用仍然受到多种因素的限制。乳酸菌基因组上已发现多种类型的CRISPR系统,也蕴含着多种未表征的Cas蛋白,利用乳酸菌内源CRISPR-Cas系统,结合外源导入的向导RNA和同源修复模板,也可实现对乳酸菌基因组的编辑。这种基于内源CRISPR-Cas系统实现基因编辑的方式,具有打靶载体相对较小易转化、无外源Cas9蛋白对宿主细胞产生毒性等优势,相比于CRISPR-SpyCas9更适合于乳酸菌基因组进行编辑,可能是一些乳酸菌未来开展基因组编辑的主要手段,本文重点对此部分内容进行了综述。

Abstract:

The CRISPR(clustered regularly interspaced short palindromic repeats)-Cas(CRISPR-associated proteins) system is an efficient and precise gene editing tool. The development of this technology has promoted genome editing into a rapid development stage. The most widely used Cas9 protein is SpyCas9 from Streptococcus pyogenes. As a “gene scissors”, the SpyCas9 protein is widely used in eukaryotes including mammals and plants. However, the application of this protein in some lactic acid bacteria(LAB) is still hampered by many factors. It has been identified that LAB genomes possess many types of CRISPR system and are rich in uncharacterized Cas proteins. Genome editing of LAB is possible by repurposing the endogenous CRISPR-Cas systems in LAB combined with exogenous single guide RNA(sgRNA) and homologous recombination template. This method employs its endogenous CRISPR-Cas system for gene editing, which has the advantages including easiness for transformation due to the relatively small targeting vector, and no concern about the toxicity of heterologous Cas9 to host cells. Compared to CRISPR-SpyCas9, the endogenous CRISPR-Cas system is more suitable for genome editing of LAB, and it may become the main genome editing tool for some LAB in the future.This article summarizes the advances in this field.