【摘要】 CRISPR(clustered regularly interspaced short palindromic repeats)系统存在于40%细菌与90%古细菌中,由前导序列、回文重复序列、相关Cas蛋白三部分构成。Cas蛋白是CRISPR系统中的一类核酸酶,对CRISPR系统发挥获得性免疫功能具有重要作用。已鉴定出至少45个Cas蛋白家族,其多样性对现有分类系统提出了巨大挑战。不同类型的Cas蛋白在CRISPR系统适应、表达、干扰等作用阶段发挥的功能各异。本文主要讨论Cas蛋白的分类及作用机制的研究进展。更多还原

【Abstract】 Clustered regularly interspaced short palindromic repeat(CRISPR)systems exist in 40% of bacteria and90% of archaea.Such systems consist of three parts,i.e.,leader sequences,arrays of short direct repeats interspersed with spacer sequences,and Cas protein genes.Cas proteins are nucleases that play important roles in acquired immunity involving CRISPR systems.At least 45 Cas protein families have been identified;such diversity presents a great challenge to the existing classification system.Different types of Cas proteins have different functions in CRISPR adaptation,expression,and interference.In the first phase,the DNA fragment of the invading virus or plasmid is introduced into the CRISPR genome as a novel spacer sequence.During the expression phase when the intruder comes,the corresponding spacer sequence will be transcribed to generate pre-crRNA.In the final stage,crRNA directs the corresponding crRNAeffector complexes(type I and III systems)or Cas9(type II systems)to the complementary virus or plasmid target sequences that match the spacers.Over the past few years,CRISPR systems have been classified according to their Cas protein content,and the aforementioned types I to V have been combined and classified as "type 1" and "type 2." This article mainly discusses advances in the classification and the function mechanisms of Cas proteins.更多还原