Construction of mouse pdx-1 gene eukaryotic expression vector and its expression in embryonic stem cells

AIM: To clone mouse pdx-1 gene and construct its eukaryotic expression vector for expression of pdx-1 in mouse embryonic stem cells.METHODS: Mouse pdx-1 cDNA fragment was amplified with polymerase chain reaction (PCR) from mouse pancreatic cDNA. The purified fragment was recombinated with a eukaryotic expression vector carrying enhanced green fluorescent protein, pEGFP-N1. The pdx-1 cDNA fragment was inserted into the multi-clone sites of the vector to construct a new plasmid, pEGFP/pdx-1. E.colli strain DH5α was transfected with the new recombinant plasmid to expand it. Plasmid DNA extracted from the expanded DH5α was identifed by cutting with Hind Ⅲ, BamHⅠ nuclease and by DNA sequencing. Identified plasmid DNA was transfected into mouse embryonic stem cell line MESPU13 by carrying with liposome. RESULTS: A 876 bp cDNA fragment was amplified from mouse pancreatic cDNA by PCR and it was inserted into the vector pEGFP-N1 correctly. The fragment was defined to be pdx-1 gene by nuclease digestion and DNA sequencing. Mouse embryonic stem cell line MESPU13 was transfected with the new recombinant plasmid DNA. The green fluorescent protein report gene and pdx-1 gene expressed in transfected mouse embryonic stem cells within 24 h. CONCLUSION: Mouse pdx-1 gene is cloned and its recombinant eukaryotic expression vector carrying green fluorescent protein is constructed successfully. It provides a useful tool for further research on the function of pdx-1.     

Cloning and expression of NK4 gene in Raji cells

AIM: To clone NK4 gene and to construct recombinant eukaryotic expression vector for observing its expression in transfected Raji cells. METHODS: Total RNA was extracted from human hepatic tissue. NK4 gene cDNA was amplified by RT-PCR, and then cloned into vector pVITRO2-mcs to construct the recombinant eukaryotic expression vector pVITRO2-mcs-NK4. Raji cells were transfected by recombinant vector pVITRO2-mcs-NK4 and screened by homomycin B. The stable strain of NK4 gene expression was screened by real-time fluorescent quantitative PCR, ELISA, immunocytohistochemistry and semisolid culture. RESULTS: The specific DNA fragment was detected by RT-PCR in Raji cells transfected with NK4 gene. The transfected Raji cells expressed NK4 mRNA and protein stably, which inhibited Raji cell proliferation, metastasis and invasion. CONCLUSION: NK4 gene is cloned and recombined to construct recombinant eukaryotic expression vector pVITRO2-mcs-NK4 successfully. NK4 gene in Raji cells expresses stably.     

Construction of eukaryotic expression vector and expression of outer membrane lipoprotein LipL41 gene of Leptospiria lai

AIM:To construct a eukaryotic expression vector expressing outer membrane lipoprotein LipL41 of Leptospira lai and express it in mammalian cell. METHODS:LipL41 gene was amplified by PCR from genome of Leptospira lai 017 strain, and was subcloned into vector pGEX-4T-1. After sequencing, LipL41 gene digested by restriction endonuclease and cloned into vector pcDNA3. After confirming the correctness of the eukaryotic recombinant vector by restrication enzyme digestion, it was transfected into COS7 cells by liposome. Its expression was analyzed by RT-PCR. RESULTS:A fragment of 1 011 bp was amplified, and sequence analysis showed it had a 98% homology with Leptospira kirschneri. The analysis of restriction enzyme indicated that the eukaryotic recombinant vector was correctly constructed. A specific amplified fragment was showed in the cells transfected with recombinant plasmid by RT-PCR, but the cell transfected with blank plasmid did not show this band. CONCLUSIONS:The LipL41 gene of Leptospira lai was successfully inserted into eukaryotic expression plasmid and the recombinant plasmid expressed the LipL41 mRNA.     

Construction of pLNCX/anti-CD20scFv/IgGFc/CD80/CD28/ζ eukaryotic expression vector and expression in NIH 3T3 cells

AIM: To construct a recombinant eukaryotic expression vector pLNCX/anti-CD20scFv/IgGFc/CD80/CD28/ζ and detect its expression in NIH 3T3 cells.METHODS: CD28-ζ cDNA was amplified from the plasmids pBULLET and inserted into pLNCX vector that contained anti-CD20 scFv/IgGFc/CD80 gene.The recombinant plasmids were transfected into NIH 3T3 cells,and resistant clones were obtained by G418 selection.The gene expression of the fusion protein was determined by RT-PCR and FACS.RESULTS: The recombinant eukaryotic vector was constructed successfully,determined by PCR and enzyme digestion analysis.The target gene was amplified from NIH 3T3 cells transfected with the vectors by RT-PCR.The FACS showed that recombinant protein was expressed in NIH 3T3 cells.CONCLUSION: Construction of pLNCX/anti-CD20scFv/IgGFc/CD80/CD28/ζ expression vector and its expression in NIH 3T3 cells lay the foundation for further research of generation of modified T lymphocytes to CD20 positive lymphoma.     

Molecular cloning of ING4 gene and ING4-induced apoptosis in HeLa cells

AIM: To isolate a gene encoding mouse ING4, construct pcDNA3.0-ING4 recombinant eukaryotic expression plasmid and investigate its effects on HeLa cells in vitro. METHODS: The mouse ING4cDNA was amplified by RT-PCR from mouse liver. The eukaryotic expression vector pcDNA3.0-ING4 was constructed by DNA recombination technique. The recombinant plasmid pcDNA3.0-ING4 was identified by PCR, restriction enzyme digestion and DNA sequence analysis, then was transfected into HeLa cells by lipofectamine. The expression was determined by RT-PCR. Apoptosis was detected by fluorescence microscope with Hoechst33258 staining and laser scanning confocal microscope. Cell cycle distribution was measured with flow cytometry. RESULTS: RT-PCR product was about 750 bp specific fragment. Analysis by restricting enzyme digestion and PCR of pcDNA3.0-ING4 recombiant plasmid showed that results were about 750 bp, DNA sequencing revealed that ING4 cloning were successful. With Hoechst fluorescence staining, we found that the percentage of apoptotic rate in HeLa cells transfected with pcDNA3.0- ING4 (21.25%) was higher than that in HeLa cells transfected with pcDNA3.0 (8.91%,P<0.01). Apoptosis was also detected by laser scanning confocal microscope. Cell cycle analysis reavealed the cell number in S phase of HeLa cells transfected with pcDNA3.0- ING4 increased. CONCLUSION: The gene encoding mouse ING4 and construction of pcDNA3.0- ING4 eukaryotic expression vector were successfully obtained, ING4 could enhance apoptosis in HeLa cells.     

Construction of eukaryotic expression vector of fusion gene CD80-IgG and its expression in Chinese hamster ovary cells

AIM: To construct the eukaryotic expression vector CD80-IgG by fusing the cDNA encoding extracellular portion of murine CD80 to the 5'-terminus of cDNA encoding Fc fragment of murine immunoglobulin G1 and to express the fusion protein in Chinese hamster ovary (CHO) cells. METHODS: The two cDNAs was amplified by PCR respectively from plasmid pcDNA/B7 containing the full-length cDNA of murine CD80 from murine spleen cells, and cloned to the eukaryotic expression vector pcDNA3.0 by directional cloning. The resultant recombinant plasmid pcDNA/CD80-IgG was transfected into CHO cells with liposome transfection reagent. The stably expressing cells were obtained by G418 screening. Western blot, Dot ELISA, and flow cytometry were used to detect the expression of the fusion protein and its immunological activity. RESULTS: DNA sequencing verified the correction of the construction of recombinant plasmid pcDNA/CD80-IgG. The expressed fusion protein was detected in the supernatant of transfected CHO cells and the molecular weight of the protein was similar to what we expected. Its immunological activity was also established. CONCLUSION: The recombinant plasmid pcDNA/CD80-IgG was successfully constructed and it expressed the fusion protein CD80-IgG.     

Construction and sequence analysis of eukaryotic expression vector of Chinese prostate-specific membrane antigen

AIM: To obtain eukaryotic expression vector of Chinese prostate-specific membrane antigen. METHODS: Chinese prostate-specific membrane antigen (PSMA) cDNA was amplified by RT-PCR from prostate cancer tissues, then cloned into eukaryotic expression vector pcDNA3.0 and sequenced. RESULTS: Seven bases in Chinese PSMA cDNA sequence were found different from those reported by Israeli, which lead to two different amino acids. CONCLUSION: We have obtained the PSMA cDNA, and the recombinant eukaryotic expression vector was successfully constructed. The study lays foundation for DCs vaccine modified by PSMA gene for the treatment of prostate neoplasms.     

Construction of eukaryotic expression vector with EGFP and hVEGF121 fusion protein and its expression in mesenchymal stem cells of rats

AIM: To construct a recombinant plasmid carrying enhanced green fluorescent protein and human vascular endothelial growth factor 121 gene and to detect its expression in rats mesenchymal stem cells (MSCs). METHODS: Human VEGF121 cDNA was amplified with polymerase chain reaction (PCR) from pCD/hVEGF121 and was inserted into the eukaryotic expression vector pEGFP-C1. The recombinant plasmid pEGFP/hVEGF121 was identified with PCR, double enzyme digestion and DNA sequencing. Then this recombinant plasmid was transfected into rat's MSCs with lipofectamine. The expression of EGFP and VEGF121 protein were detected with fluorescence microscope and immunocytochemical staining, respectively. RESULTS: The recombinant plasmid was confirmed with PCR, double enzyme digestion and DNA sequencing. The fluorescence microscope and immunocytochemical staining results showed that the EGFP and VEGF121 protein were expressed in MSCs 48h after transfection. CONCLUSIONS: The recombinant plasmid carrying enhanced green fluorescent protein and human vascular endothelial growth factor was successfully constructed and expressed positively in rat MSCs. It provides a good basis for further research on differentiation of MSC and VEGF gene therapy for ischemial cardiovascular disease.     

Construction of pNTAP-PRAK eukaryotic expression plasmid and its expression in HEK293 cells

AIM: To construct pNTAP-PRAK eukaryotic expression plasmid and to establish a stable HEK293 cell line expressing tandam affinity purification (TAP)-tagged PRAK. METHODS: Human PRAK coding region was subcloned into pNTAP vector to construct a recombinant plasmid called pNTAP-PRAK, then DH5α E.coli was transformed with the recombinant plasmid. After identified by PCR, digestion with restriction endonuclease and sequencing, the correct recombinant expression plasmid was transfected with PolyFect liposome transfection reagent to HEK293 cells. The cell line with stable expression of exogenous TAP tagged-PRAK gene was established by screening of antibiotic G418. The expression and localization of the fusion protein TAP tagged-PRAK were detected by Western blotting and immunofluorescence assay. RESULTS: All the results of identification by PCR, digestion with restriction endonuclease and sequencing indicated that the recombinant eukaryotic expression plasmid pNTAP-PRAK was constructed correctly. The result of Western blotting showed that the recombinant plasmid was expressed stably in HEK293 cells after transfection followed by G418 screening. The result of immunofluorescence assay showed that the expression product TAP tagged-PRAK distributed mainly in the nucleus. CONCLUSION: The eukaryotic expression vector pNTAP-PRAK was successfully constructed and the cell line stably expressing TAP tagged-PRAK was established. TAP tag didnt influence the localization of exogenous PRAK.     

Role of B7-H6 over-expression in NK cell-mediated apoptosis of hepatocytes

AIM: To investigate the role of B7 homologue 6 (B7-H6) over-expression in natural killer (NK) cell-mediated hepatocyte apoptosis. METHODS: The full-length fragment of B7-H6 gene was amplified by PCR and subcloned into linearized eukaryotic expression vector pIRES2-EGFP to construct recombinant B7-H6 over-expression vector pIRES2-EGFP-B7-H6. The recombinant plasmid was identified by double digestion, PCR and sequencing, and was then transfected into L02 cells. The expression of EGFP was observed by fluorescence microscopy and the transfection efficiency was evaluated by flow cytometry. B7-H6 expression was confirmed by qRT-PCR and Western blot. The L02 cells transfected with pIRES2-EGFP-B7-H6 recombinant plasmid were co-cultured with NK-92 cells at different effector/target ratios, and the cytotoxicity of NK-92 cells was evaluated by CCK-8 assay.RESULTS: The strong green fluorescence in the L02 cells was observed under fluorescence microscope 48 h after transfection. The transfection efficiency reached 92.6%. The expression of B7-H6 at mRNA and protein levels was remarkably increased 48 h after transfection. The cytotoxicity of NK-92 cells against L02 cells transfected with pIRES2-EGFP-B7-H6 plasmid was significantly higher than that of the null vector transfection group (P<0.05).CONCLUSION: The recombinant eukaryotic expression vector pIRES2-EGFP-B7-H6 was constructed successfully. The cytotoxic effect of NK-92 cells against L02 cells can be enhanced by transfecting L02 cells with pIRES2-EGFP-B7-H6 plasmid.     

Construction and identification of eukaryotic expression vector of bcl-2 siRNA

AIM: To construct eukaryotic expression vector of small interfering RNA(siRNA) specific to bcl-2 and investigate the effect of recombinant plasmid on suppressing bladder cancer cell growth.METHODS: siRNA of bcl-2 gene was designed according to the principle of RNAi-based medicine, and was converted into cDNA coding expression of small hairpin RNAs(shRNA) of siRNA. The cDNA was synthesized and inserted into plasmid pGenesil-1. The recombinant eukaryotic expression vectors of pGenesil-1545 and pGenesil-1555 were controlled by the U6 promoter of RNA polymerase Ⅲ, identified by the restriction map and the sequence analysis, and transfected into T24 cells. After T24 cells were transfected for 72 h, expression of bcl-2 mRNA was assayed by RT-PCR; and MTT was used to observe the proliferation of T24 cells.RESULTS: The recombinant plasmids of pGenesil-1545 and pGenesil-1555 were identified by the restriction map and the sequence analysis. The sequences completely coincided with the designs. The expression of the bcl-2 mRNA in T24 cells transfected with recombinant plasmid decreased nearly 80%, and the growth of T24 cells was suppressed significantly.CONCLUSION: The siRNA eukaryotic expression vector against bcl-2 gene is successfully constructed. It effectively downregulates the expression of bcl-2 in T24 cells and suppresses the cell growth.     

Construction and identification of eukaryotic dicistronic vector expressing TCA-12-2/TCB-7.1

AIM: To construct the recombinant dicistronic eukaryotic expression vector pDC315-TCA-12-2-TCB-7.1, which containing T cell antigen receptor (TCR) genes TCA-12-2 and TCB-7.1, and to transfer this recombinant vector into 293 cells to investigate the expression of TCA-12-2 and TCB-7.1. METHODS: The TCA-12-2 was obtained by RT-PCR from the T cells and the TCB-7.1 was amplified by PCR from plamid pcDNA3.1-TCB-7.1 that we constructed before. TCA-12-2 and TCB-7.1 was cloned into vector pIRES2-AcGFP1 firstly, then subcloned into vector pDC315. The recombinant plasmid pDC315-TCA-12-2-TCB-7.1 was verified by restriction enzyme digestion and sequencing, the positive recombinant plasmid was transferred into 293 cells using Lipofectamine 2000. The expressions of gene TCA-12-2 and TCB-7.1 were identified by RT-PCR and flow cytometry. RESULTS: Both TCA-12-2 and TCB-7.1 genes were constructed into eukaryotic expression vector pDC315 and the expressions of genes in 293 cells were detected successfully with RT-PCR and flow cytometry. CONCLUSION: The dicistronic expression vector pDC315-TCA-12-2-TCB-7.1 is successfully constructed and expressed.     

Construction of human anti-HBc ScFv eukaryotic expression vector and expression of anti-HBc ScFv in HepG2 cells

AIM: To construct an eukaryotic expression vector of human single-chain variable fragment against hepatitis B virus core protein (anti-HBc ScFv) and detect its expression in HepG2 cells. METHODS: Anti-HBc ScFv genes were amplified from the plasmids abstracted from positive clone and inserted into pEGFP-c1 vector that contained green fluorescent protein gene. The recombinant plasmids were transfected into HepG2 cells, and resistant clones were obtained by G418 selection. The expression of the gene of fusion protein was determined by fluorescent invert microscope and ELISA. RESULTS: Recombinant plasmids were successfully constructed. The plasmid transfected HepG2 cells were obtained by G418 selection. Specific fluorescence was observed in HepG2 cells 48 hours after transfection. ELISA analysis confirmed the expression of anti-HBc ScFv in the cells. CONCLUSION: The construction of human anti-HBc ScFv eukaryotic expression vector and its expression in HepG2 cells lay the foundation for advanced research of intracellular anti-HBc ScFv.     

Selection of the exogenous signal peptide that conducts the secretion of hepatopoietin

AIM: To look for a suitable signal peptide which may effectively conduct hepatopoietin (HPO) secretion, various recombinant eukaryotic expression vectors were constructed. METHODS: Different exogenous signal sequences were spliced with HPO cDNA by PCR, and the spliced genes were cloned into eukaryotic expression plasmids. The different recombinants were respectively tansfected into COS-7 cells by Lipofectamine 2000 method and the secretion of HPO was analyzed by Western blotting. RESULTS: Western blotting analysis indicated that the signal peptides from interleukin-1 receptor antagonist (IL-1ra) and an artifical signal peptide did not secret HPO directly and effectively, but the signal peptide from murine Ig kappa secreted HPO directly with great efficiency. The molecular weight of the secreted HPO was 30 kD, which means that the secreted HPO existed in homodimer. CONCLUSION: Secreted recombinant expression plasmid is successful constructed. The result may pave the way for the gene therapy of hepatic fibrosis.     

Construction and in vitro analysis of recombinant adenovirus vector carrying red fluorescent protein reporter gene

AIM: To provide important tools for gene therapy and gene vaccine research by constructing an adenovirus vector containing red fluorescent protein ( RFP ) reporter gene with the approach of in vitro recombinant ligation. METHODS: The RFP gene fragment of pTurboRFP-N was digested and ligated into pShuttle transfer vector to construct recombinant vector pShuttle-TurboRFP-N. I- Ceu I/PI- Sce I were used to double digest recombinant vector pShuttle-TurboRFP-N and backbone of vector pH5'040.pkGFP-II. The target fragment was collected and ligated, and recombinant adenovirus vector AdH5'.040.CMV.RFP-N was obtained. After linearization, the vector was transfected into AD293 cells by liposome for virus packaging. The efficiency of virus packaging and RFP expression level in AD293 cells were examined using fluorescent microscope. In addition, the biological activity and titer of the virus were tested. Human lung cancer cell line A549 and breast cancer cell line MDA-MB-231 were infected with recombinant adenovirus vector AdH5'.040.CMV.RFP-N and control adenovirus vector AdH5.CMV.EGFP respectively. The infection efficiencies of the 2 vectors to different cell lines were compared by evaluating the expression levels of RFP and enhanced green fluorescent protein (EGFP). RESULTS: The recombinant adenovirus vector AdH5'.040.CMV.RFP-N was correctly constructed and confirmed by enzyme digestion. The virus was packaged by the vector in AD293 cells and had the ability to infect the target cells. The target gene in eukaryotic cells was also expressed. The number of recombinant adenoviruses and the titer of the virus after amplification and purification were 3.6×10¹⁵ vp/L and 1×10¹³ pfu/L,respectively. The infection efficiencies of recombinant adenovirus vector Ad5'.040.CMV.RFP-N to human lung cancer cell line A549 and breast cancer cell line MDA-MB-231 were higher than those in control adenovirus vector AdH5.CMV.EGFP (P<0.05). CONCLUSION: We have constructed recombinant virus vector carrying RFP reporter gene and provide an important tool for gene therapy and gene vaccine research. The reporter gene can be highly expressed in AD293 cells and has high infection efficiency to cancer cells. RFP is a good substitution and supplement to green fluorescent protein.     

Construction of recombinant plasmid pEGFP-HSP70 and its expression in rat neural stem cells

AIM：To explore the method of constructing recombinant plasmid pEGFP-HSP70 and its expression in neural stem cells. METHODS：Total RNA was acquired from the fetal liver tissue of SD rat. cDNA complete sequence of heat-shock protein 70 (HSP70) gene was amplified by RT-PCR, and cloned into an eukaryotic expression vector containing the enhanced green fluorescent protein (EGFP) reporter gene, pEGFP-C2. Sequencing analysis was performed to confirm the recombinant plasmid pEGFP-HSP70. The technique of nucleofector transfection was used to transfect the recombinant plasmid pEGFP-HSP70 into neural stem cells. RESULTS：HSP70 cDNA sequence was correctly cloned into the eukaryotic expression vector pEGFP-C2. The recombinant plasmid pEGFP-HSP70 was constructed successfully. Compared with control group, the fluorescence intensities in pEGFP-C2 group and pEGFP-HSP70 group were significantly increased. The fluorescence intensity in pEGFP-HSP70 group after 24 h of transfection was significantly decreased compared with other time points of 7 d, 14 d and 21 d. The expression level of HSP70 significantly increased 1 d, 7 d and 14 d after transfection compared with control group. CONCLUSION：The neural stem cells can be directly used as gene action target cells. The HSP70 expression level in the stem cells is closely related to the time after transfection.