The influence of the copy number of invader on the fate of bacterial host cells in the antiviral defense by CRISPR-Cas10 DNases  

作　　者：Zhenxiao Yu Jianan Xu Yan Zhang Qunxin She 

机构地区：[1]CRISPR and Archaea Biology Research Center,State Key Laboratory of Microbial Technology and Microbial Technology Institute,Shandong University,Qingdao 266237,China [2]College of Food and Biological Engineering,Henan University of Animal Husbandry and Economy,Zhengzhou 450000,China

出　　处：《Engineering Microbiology》2023年第4期38-47,共10页工程微生物学（英文）

基　　金：supported by grants from the National Key R&D Pro-gram of China(2021YFA0717000);the National Natural Science Foun-dation of China(31771380)to QS;from the China Postdoctoral Sci-ence Foundation(2020M672050);the Qingdao Applied Research Fund For Postdoctoral Researchers(62450079311107)to ZY;an Open Project from the State Key Laboratory of Microbial Technology at Shan-dong University.

摘　　要：Type Ⅲ CRISPR-Cas10 systems employ multiple immune activities to defend their hosts against invasion from mobile genetic elements(MGEs),including DNase and cyclic oligoadenylates(cOA)synthesis both of which are hosted by the type-specific protein Cas10.Extensive investigations conducted for the activation of Cas accessory proteins by cOAs have revealed their functions in the type Ⅲ immunity,but the function of the Cas10 DNase in the same process remains elusive.Here,Lactobacillus delbrueckii subsp.Bulgaricus type Ⅲ-A(Ld)Csm system,a type Ⅲ CRISPR system that solely relies on its Cas10 DNase for providing immunity,was employed as a model to investigate the DNase function.Interference assay was conducted in Escherichia coli using two plasmids:pCas carrying the LdCsm system and pTarget producing target RNAs.The former functioned as a de facto“CRISPR host element”while the latter,mimicking an invading MGE.We found that,upon induction of immune responses,the fate of each genetic element was determined by their copy numbers:plasmid of a low copy number was selectively eliminated from the E.coli cells regardless whether it represents a de facto CRISPR host or an invader.Together,we reveal,for the first time,that the immune mechanisms of Cas10 DNases are of two folds:the DNase activity is capable of removing low-copy invaders from infected cells,but it also leads to abortive infection when the invader copy number is high.

关 键 词：TypeⅢCRISPR systems Target RNA-activated Cas10 DNase Invader copy number Plasmid interference assay Abortive infection Invader clearance 

分 类 号：Q93[生物学—微生物学]