Two-plasmid scarless genetic modification in Escherichia coli hfq and rne-710 / 生物工程学报

Gene modification is an important technique to understand gene function. We firstly constructed Δhfq::Spe and Δrne-710::Spe mutant strains of Escherichia coli MG1655. The fragment lacking of hfq and rne-710 was ligated to the auxiliary plasmid and separately replace the spectinomycin box by homologous recombinase system to obtain the Δhfq and Δrne-710 mutant strains. The combination of two-plasmid scarless genetic modification and fusion PCR led to a new way for the long DNA fragment gene deletions.

Fusion expression,detection and application of HHV-8 antigen / 重庆医学

Objective To construct the prokaryotic expression plasmid of HHV-8 fusion antigen for diagnosis of HHV-8 infec-tion .Methods The combined fragment ORF59 ,ORF65 and K8 .1 by fusion PCR was integrated into pQE-80L and transfected into E .coli DH5α.Fusion protein was induced to express by IPTG .SDS-PAGE and Western blot were employed to detect the fusion protein .Fusion protein was used to detect serum of blood donors .Results The combined plasmid pQE-80L-ORF59-ORF65-K8 .1 was constructed successfully after verifying by restriction enzyme digestion and sequencing .The fusion protein was about 24 KD and could be specific combined with HHV-8 positive serum .The fusion protein had the same result to detect HHV-8 with the HHV-8 ELISA kit .Conclusion Fusion protein we construct can be used as diagnosis antigen to detect HHV-8 of blood donors and common people .

Epitope Tagging of the rpoS gene of Y. pestis by Recombineering Technique / 中国生物工程杂志

Objective: To facilitate the functional analysis of chromosomal genes and their products, the recombineering technique to epitope tagging of chromosomal genes of Y. pestis was adapted. Methods: The epitope tag was generated by primer annealing and then fused with resistance gene by fusion PCR. The epitope-resistance cassette was inserted into pBluecript, resulted in the template plasmid, pBS-MH. The tagging cassette for rpoS was obtained by PCR amplification from pBS-MH with primers containing homology specific to the target gene. PCR products were transformed into recombination competent cells and recombinants were selected. PCR and DNA sequencing were used to confirm the correct tagging event. The expression of the tagged protein was detected with Western blot by using monoclonal antibody to the epitope. Results: The template plasmid containing fusion of epitope and resistance gene was successfully constructed. The sigma factor gene, rpoS, was tagged with a myc-his tag at the COOH terminus. Expression of the tagged rpoS was successfully detected indirectly by the antibody against His tag. Conclusion: The chromosomal gene tagging by recombineering technique represents a powerful tool in the functional study of bacterial genes and their products.

A Rapid Method for Generation of Homologous Recombinant Fragments—Fusion PCR / 中国生物工程杂志

Fusion PCR, which employs chimeric primers to generate PCR products with complementary ends in its amplifications, is a rapid and flexible method in joining different DNA fragments. This method can assemble DNA fragments without the treatment of restriction endonucleases and T4 DNA ligase. It offered a shortcut for the construction of homologous recombinant fragments. Through assembling three recombinant fragments successfully, fusion PCR procedure was improved and manipulation essentials of fusion PCR were described in detail. The results indicated that the improved procedure can assemble three or four fragments simultaneously, and the length of each fusion product is above 4.5 kb. The result recombinants were proposed to be use in further experiments, which structures had been confirmed by sequencing.