ABSTRACT
Group Ⅱ introns are self-splicing ribozymes, which insert directly into target sites in DNA with high frequency through "retrohoming". They specifically and efficiently recognize and splice DNA target sites, endowing themselves with great potential in genetic engineering. This paper reviewed the gene targeting principle of group Ⅱ introns and the application in microbial genetic modification, and then analyzed the limitations of them in multi-functional gene editing and eukaryotes based on the "retrohoming" characteristics and the dependence on high Mg2+ concentration. Finally, we dissected the potential of group Ⅱ introns in the development of novel gene editing tools based on our previous research outcome and the structural characteristics of the introns, hoping to provide a reference for the application of group Ⅱ introns in biotechnology.
Subject(s)
DNA , Eukaryota , Gene Targeting , Introns/genetics , RNA, Catalytic/geneticsABSTRACT
To construct TeI3c/4c-based and temperature-inducible gene inactivation system (Thermotargetron) and to apply it to gene inactivation of mesophilic bacteria. The subunit of flagellum (fliC) and C4 dicarboxylate orotate:H⁺ symporter (dctA) genes were chosen as targets in the genome of Escherichia coli HMS174 (DE3) strain. According to recognition roles of TeI3c/4c intron, the fliC489a, fliC828s, fliC1038s and dctA2a sites were chosen as target sites. Gene-targeting plasmids were constructed based on pHK-TT1A by using overlap PCR method and transformed into HMS174 cells. An aliquot mid-log phase cultures of the transformants were shocked at 48 °C and plated on LB plate (containing chloramphenicol). Afterwards, gene mutants were screened by using colony PCR and DNA sequencing. After the mutants were obtained, the phenotypes of ΔfliC and ΔdctA gene mutants were characterized by using agar puncture and carbon metabolism experiments. Colony PCR and sequencing results show that TeI3c/4c intron was inserted in the designed sites of fliC and dctA genes. The gene-targeting efficiency of Thermotargetron system was 100%. Phenotype verification experiments of the mutants demonstrated that the cell motility of all ΔfliC mutants was damaged and the malate assimilation ability of ΔdctA mutant was deprived comparing to wild-type HMS174 strain. In our study, a temperature-inducible and high-efficiency gene inactivation system was established for mesophilic bacteria. This system could achieve high efficiency and precise gene inactivation by modulation of the incubation duration of the transformants at 48 °C.
ABSTRACT
Objective To knockout and identify the Antigen 43 (Ag43) in the Escherichia Coli JM109 .Methods Mutation group Ⅱ introns RNA protein complexes (RNP) gene sequence was obtained by Sigma Company′s TargeTron Gene Knockout Sys‐tem and Ag43 gene specific designed PCR primers amplification ,then ,to acquired Ag43 specific recombinant RNP plasmid pACD4K‐Ag4 ,this gene sequence was inserted into the plasmid pACD4K‐C of RNA′s expression .Finally ,pEGFP‐Ag43 was trans‐formed into JM109 and inserted the group Ⅱ intron into the Ag43′s locus by IPTG inducing expression .Results The best insertion locus was between 1 812 and 1 913 .Through the agarose electrophoresis gel ,the RNP gene sequence was consistent with the expec‐ted value (350 bp) .The pEGFP‐Ag43 vector was correctly constructed which was proofed by endonuclease Nhe Ⅰ and Hind ⅡI di‐gestion as predicted products (3 646 and 4 029 bp;7 000 and 550 bp ,respectively ) .The PCR and gene sequence results indicated that the group Ⅱ intron was inserted into the locus between 1 812 and 1 913 in the Ag43 gene .Conclusion Successful knockout of the Ag43 in Escherichia Coli JM109 found basis to further study the Ag43′s function and regard the coli as host bacteria of Ag43 chimeric protein recombinant .