Prokaryotic expression, purification and characterization of tissue inhibitor of metalloproteinase-2 / 生物工程学报

Tissue inhibitor of metalloproteinases-2 (TIMP-2) inhibits tumor migration and invasion. Obtaining TIMP-2 protein is conducive to a comprehensive and in-depth study of its function and mechanism in tumorigenesis and development. We collected human TIMP-2 protein through prokaryotic expression in vitro. We expressed, purified and characterized human TIMP-2 protein. First, the human TIMP-2 gene was cloned from the cDNA obtained by reverse transcription of total RNA of human lung cancer A549 cells, and constructed to pET28a vector. The recombinant plasmid pET28a-TIMP-2 was transformed into Escherichia coli BL21(DE3) after restriction endonuclease digestion and sequencing analysis. The expression of TIMP-2 protein was induced by isopropyl-β-D-thiogalactoside (IPTG), and the expression conditions were optimized. After purification by nickel affinity column, the fusion protein His-TIMP-2 was identified by Western blotting method and its biological activity was detected by gelatin zymography. The fusion protein His-TIMP-2 existed in the form of inclusion body in E. coli. In a certain range, the concentration of IPTG had no significant effect on the expression amount of His-TIMP-2. But in this expression system, induction temperature and time were the key parameters, and the expression amount of His-TIMP-2 in E. coli increased with the increase of induction temperature. The purified and refolded fusion protein could effectively inhibit the activity of matrix metalloproteinases expressed by human lung cancer A549 cells. The acquisition of active fusion protein lays a foundation for further study of the function and mechanism of human TIMP-2, and is of great significance for tumor therapy.

Gene transfer of Chlorella vulgaris n-3 fatty acid desaturase optimizes the fatty acid composition of human breast cancer cells

Chlorella vulgaris has the gene of n-3 fatty acid desaturase (CvFad3), which can synthesize the precursor of n-3 polyunsaturated fatty acids (PUFAs) or convert n-6 to n-3 PUFAs. The objective of the present study was to examine whether the CvFad3 gene from C. vulgaris can be functionally and efficiently expressed in human breast cancer cells and whether its expression can exert a significant effect on cell fatty acid composition. We inserted the CvFad3 gene into the plasmid pEGFP-C3 to construct the eukaryotic expression vector pEGFP-C3-n-3 and to express the n-3 Fad gene in human breast cancer cells (MCF-7 cells). Transfection of MCF-7 cells with the recombinant vector resulted in a high expression of n-3 fatty acid desaturase. Lipid analysis indicated that the ratio of n-6/n-3 PUFAs was decreased from 6:1 in the control cells to about 1:1 in the cells expressing the n-3 fatty acid desaturase. Accordingly, the CvFad3 gene significantly decreased the ratio of n-6/n-3 PUFAs of the MCF-7 cell membrane. The expression of the CvFad3 gene can decrease cell proliferation and promote cell apoptosis. This study demonstrates that the CvFad3 gene can dramatically balance the ratio of n-6/n-3 PUFAs and may provide an effective approach to the modification of the fatty acid composition of mammalian cells, also providing a basis for potential applications of its transfer in experimental and clinical settings.

HIGH-LEVEL EXPRESSION OF RECOMBINANT TRICHOSANTHIN IN ESCHERICHIA COLI AND EVALUATION OF ITS IMMUNOGENICITY / 解剖学报

Objective The TCS gene without N-and C-terminal sequences was cloned into pET-29b in order to get the recombinant trichosanthin(rTCS) at the relatively high level in E.coli,and the rTCS immunogenicity was compared with natural TCS(nTCS). Methods TCS gene without the N-and C-terminal coding sequences was amplified by RT-PCR,and then inserted into pET-29b.The soluble rTCS was induced with IPTG and purified through metal chelate affinity chromatography,the purity and content were showed by the thin-layer scan analysis and bradford assay.After the rabbits were immunized with purified rTCS and nTCS,respectively,the titer and specificity of polyclonal antibody were detected by indirect ELISA assay and Western blotting. Results 1.The vector pET-29b-TCS was constructed successfully after it was confirmed with the same restriction enzymes.2.The rTCS attained the maximum in the presence of 1 mmol/L IPTG for 4?h at 30℃.3.The soluble rTCS was expressed at relatively high level(36% of total protein in E.coli) and the yield of rTCS with a purity of 95% was 1.2?g in 1 L bacterium.4.The polyclonal antisera titer of nTCS was significantly higher than that of rTCS(1∶40?960 and 1∶5?120 respectively).5.The specific reaction between rTCS and anti-nTCS antibody was detected by Western blotting.Conclusion The high level expressing vector pET-29b-TCS,carrying TCS gene withoug the N-and C-terminal coding sequences,was constructed successfully.The immunogenicity of rTCS was remarkably lower than that of nTCS,which indicates that glycosylation of nTCS has a relationship with the antigenicity.