Construction of Shuttle Expression Plasmid and Stable Expression of Foreign Gene in Mycobacteria and E．Coli

By employing the pUC19 as a backbone,the regulatory and signal sequences which encode kanamycin resistance, and mycobacterial plasmid origin of replication (oriM) were cloned into the pUC19. The recombinant E. Coli-mycobacteria shuttle expression plasmid PBCG-8000 was constructed. The PBCG-8000 was able to replicate in both E. Coli and mycobacteria (including BCG) systems, and to confer stable kanamycin resistance upon transformants. The study should facilitate the development of BCG and other mycobacteria into multivalent vaccine vectors.

THE USE OF A SHUTTLE PLASMID TO STUDY NONTARGETED MUTAGENESIS AND ITS SEQUENCE SPECIFICITY

Intact pZ189 DNA was replicated in monkey kidney vero cells which had been pretreated with Nmethyl-N’-nitro-N-nitrosoguanidine (MNNG) . The mutants were selected in E. coli MBM7070 and the mutation frequencies involving mutants with unchanged electrophoretic mobilrty of their plasmid DNA were scored. When compared to the spontaneous mutation frequency. the mutation frequencies were increased by 5.8 and 2.9-fold in cells pretreated with 0. 2 and 2μmol/L MNNG, respectively. The supF genes of these mutants were sequenced. and it was found that the types of base substitution and the sites of frameshifts differed from findings in studies of spontaneous and targeted mutagenesis. The results suggest that nontargeted mutagenesis occurs in mammalian cells and may have a sequence specificity.

Expression of Foreign Gene in Mycobacterium Regulated by Human Mycobacterium Tuberculosis Heat Shock Protein 70 Promoter

The DNA fragments of 150bp length promoter 0f human Mycobacterium(M.) tuberculosis heat shock protein (hsp)7O and 650bp length foreign gene, the Schistosoma japonicum glutathione S-transferase(Sj26GST)gene,were obtained by amplification with polymerase chain reaction. And the 150p DNA sequence upstream initiation codon ATG of the human M. tuberculosis hsp7O promoter that contains the sequence TTGAG and ATCATA which consensus with E. coli promoter's -35 and-10 region respectively, as well as ribosome binding site GGAGG at position-12-8 upstream the ATG were determined by SangerDideoxyribonucleotide-mediated chain-termination method-Then, the human M. tuberculosis hsp70 promoter and Sj26GST cDNA were cloned into E. coli-mycobacteria shuttle plasmid pBCG-2000 to construct E. coli-Mycobacterium expression shuttle plasmid pBCG- Sj26 that can express Sj26GST gene.The M. smegmatis were electroporated and the positivecolonies were selected by kanamycin-The M.smegmatis containing the vector pBCG-Sj26 can be induced by heating and hydrogen peroxide (H2O2) to express GST. The molecular weight of the recombinant GST(rGST) was 26000. The rGST contents that were about 10 percent of the total bacterial protein were analyzed by density scanning after running SDS-PAGE. This study would provide scientific evidences for application of hsp70 promoter in expressing foreign gene in mycobacterium and development of mycobacterium as multiple-valent vectoral vaccine.

The Construction of Schistosoma Japonicum Vaccine BCG-Sj26GST and Its Identification

Summary: The expression of foreign gene, Schistosoma Japonicum 26 ku antigen (Sj26GST), in Bacillus Calmette Guerin (BCG), Mycobacterium ( M. smegmatis ) and Escherichia coli ( E. coli ) were studied. The cDNA fragment encoding Sj26GST was amplified by PCR using plasmid pGEX, which could express Sj26GST in E. coli as template. The Sj26GST cDNA was cloned into the downstream of human M. tuberculosis heat shock protein (hsp) 70 promoter with correct reading frame, and then the DNA fragment containing hsp70 promoter and Sj26GST gene were subcloned together into E. coli Mycobacteria shuttle plasmid pBCG 2000 to construct the expression shuttle plasmid pBCG Sj26. The recombinant BCG and M. smegmatis mc 2 155, which were electroplated with pBCG Sj26, could express Sj26GST and the recombinant Schistosoma Japonicum vaccine BCG Sj26GST was made. The recombinant Sj26GST (rSj26GST) were soluble and could be observed on SDS PAGE at molecular weight of 26 ku. The content of rSj26GST accounted for 15 % and 10 % of total bacterial protein in BCG and M. smegmatis respectively. The results of Western blot showed the combination of rSj26GST with antibody of GST.

Assembly of long DNA sequences using a new synthetic Escherichia coli-yeast shuttle vector

Synthetic biology is a newly developed field of research focused on designing and rebuilding novel biomolecular components, circuits, and networks. Synthetic biology can also help understand biological principles and engineer complex artificial metabolic systems. DNA manipulation on a large genome-wide scale is an inevitable challenge, but a necessary tool for synthetic biology. To improve the methods used for the synthesis of long DNA fragments, here we constructed a novel shuttle vector named p GF(plasmid Genome Fast) for DNA assembly in vivo. The BAC plasmid p CC1 BAC, which can accommodate large DNA molecules, was chosen as the backbone. The sequence of the yeast artificial chromosome(YAC) regulatory element CEN6-ARS4 was synthesized and inserted into the plasmid to enable it to replicate in yeast. The selection sequence HIS3, obtained by polymerase chain reaction(PCR) from the plasmid p BS313, was inserted for screening. This new synthetic shuttle vector can mediate the transformation-associated recombination(TAR) assembly of large DNA fragments in yeast, and the assembled products can be transformed into Escherichia coli for further amplification. We also conducted in vivo DNA assembly using p GF and yeast homologous recombination and constructed a 31-kb long DNA sequence from the cyanophage PP genome. Our findings show that this novel shuttle vector would be a useful tool for efficient genome-scale DNA reconstruction.

Genetic technologies for extremely thermophilic microorganisms of Sulfolobus, the only genetically tractable genus of crenarchaea

Archaea represents the third domain of life, with the information-processing machineries more closely resembling those of eukaryotes than the machineries of the bacterial counterparts but sharing metabolic pathways with organisms of Bacteria, the sister prokaryotic phylum. Archaeal organisms also possess unique features as revealed by genomics and genome comparisons and by biochemical characterization of prominent enzymes. Nevertheless, diverse genetic tools are required for in vivo experiments to verify these interesting discoveries. Considerable efforts have been devoted to the development of genetic tools for archaea ever since their discovery, and great progress has been made in the creation of archaeal genetic tools in the past decade. Versatile genetic toolboxes are now available for several archaeal models, among which Sulfolobus microorganisms are the only genus representing Crenarchaeota because all the remaining genera are from Euryarchaeota. Nevertheless, genetic tools developed for Sulfolobus are probably the most versatile among all archaeal models, and these include viral and plasmid shuttle vectors, conventional and novel genetic manipulation methods, CRISPR-based gene deletion and mutagenesis, and gene silencing, among which CRISPR tools have been reported only for Sulfolobus thus far. In this review, we summarize recent developments in all these useful genetic tools and discuss their possible application to research into archaeal biology by means of Sulfolobus models.