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.     

Expression of NK4 gene in human pancreatic cancer cells and its effect on growth of human vascular endothelial cells

AIM:The current study was designed to construct eukaryotic expression vector containing NK4 gene and transfect it into human pancreatic cancer cell lines.METHODS:The recombinant of pcDNA3/hNK4 was digested by restriction enzyme,the NK4 gene was cloned into a high effective eukaryotic expressing plasmid which contains CMV2 immediate early gene promoter and then transiently introduced into the pancreatic cancer cell line SW1990 by lipo fectamine and clonal cel lines that secrete high levels of NK4 protein were isolated.The expression of NK4 was observed by RT-PCR and Western blot,in vitro the vascular endothelial cell proliferation inhibiting activity of NK4 was examined by 3-[4,5-dimethylthiazolzyl]-2,5-diphenyl tetrazolium bromide(MTT)method.RESULTS:A specific expression of NK4 gene mRNA by lipofectamine-mediated transfer exhibited only in SW1990/NK4 cells,Western blot analysis demonstrated that there was positive expression of NK4 protein(50 kD).The NK4 inhibited proliferation of the vascular endothelial cellsin vitro.CONCLUSION:The recombinant of pRC/CMV2-hNK4 is a high effective expressing eukaryotic vector.The bio-engineering product of the NK4 is an angiogenesis inhibitor and may play an important role in the gene therapy for tumor.     

Cloning and sequence analysis of death associated protein kinase gene ORF and DAPK1 inducing Raji cell apoptosis

AIM: Open reading frame(ORF) of death associated protein kinase1(DAPK1) gene was cloned for studying on tumor forming and metastasis.METHODS: Based on nucleotide sequence of DAPK1 gene from GenBank, a pair of primers was designed. DAPK1 gene ORF was transfected into Raji cells in expression vector pcDNA3.1(+) with lipofectamine reagent. Morphologic assessment of apoptosis was performed with fluorescence microscope cytotoxicity and cell viability was assayed by MTT. RESULTS: DAPK1 gene ORF was amprified from K562 cells by RT-PCR. It was cloned into plasmid pMD18-T and sequenced. There were seven mutation in 4 300 bp nucleotide sequence relatively to DAPK1 nucleotide sequence from GenBank, but six was synonymous mutation and one was single nucleotide polymorphism. 4 300 bp nucleotide of DAPK1 gene ORF was transfected into Raji cells. DAPK1 gene expression was detected in 48 h after it was transfected into Raji cells. Then Raji cells showed apoptosis. CONCLUSION: Large fragment gene was cloned by RT-PCR and transfected into Raji cells successfully. Over-expression of DAPK1 gene induced Raji cells apoptosis.     

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 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.     

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 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.     

Effect of adipose differentiation-related protein on proliferation and apoptosis in H9c2 cells

AIM: To construct an adipose differentiation-related protein (ADRP) eukaryotic expression vector and to explore the effect of ADRP on apoptosis of H9c2 cells induced by palmitic acid (PA). METHODS: The ADRP gene obtained by the method of RT-PCR was cloned into pEGFP-C1 plasmid. The recombinant plasmid was transformed into E.coli DH5α for amplification. The recombinant plasmid was extracted from E.coli DH5α and transfected into H9c2 cells by Lipofectamine^TM2000. The stable transformants were selected by G418 screening. Expression of green fluorescent protein was observed under fluorescence microscope and the ADRP expression was identified by RT-qPCR and Western blotting analysis. The effect of PA on the proliferation of H9c2 cells was detected by MTT assay. The apoptotic percentage of H9c2 cells caused by PA was determined by flow cytometry. RESULTS: The eukaryotic expression vector pEGFP-C1-ADRP was successfully constructed. Green fluorescent was observed in the cells transfected with pEGFP-C1 or pEGFP-C1-ADRP under fluorescence microscope. RT-qPCR and Western blotting analysis showed that recombinant cells exhibited high mRNA and protein levels of ADRP. After treated with PA at different concentrations, the apoptosis rates and the proliferation inhibition of recombinant cells were both lower than those of the other two cells. CONCLUSION: The transfected H9c2 cells with stable ADRP expression were successfully established. The over-expression of ADRP prevents the cells from apoptosis and inhibition of proliferation caused by PA, indicating that ADRP plays a protective role in H9c2 cells.     

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 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 of eukaryotic expression vector miRNA let-7a1 and its effect on the proliferation of lung cancer A549 cells

AIM: To construct a recombinant eukaryotic expression vector, pSilencer 4.1-let-7a1 and to express it in lung cancer A549 cells for detecting its effect on the proliferation of A549 cells. METHODS: The pre-let-7a1 sequence was amplified by RT-PCR using RNA from human lung cancer A549 cells, and then inserted into pSilencer 4.1-CMV neo vector to generate pSilencer 4.1-let-7a1 which was transfected into lung cancer A549 cells. The expression of miRNA let-7a1 was verified by RT-PCR. Its activity in A549 cells was determined by luciferase reporter assay after cotransfection of let-7a1 target sequence-reporter gene plasmid with pMIR-report let-7a1T, which was constructed by inserting let-7a1 target sequence into the luciferase reporter 3’UTR of pMIR-report luciferase vector. The effect of pSilencer 4.1-let-7a1 transfection on A549 cell proliferation was detected by MTT method. RESULTS: The sequences of cloned pre-let-7a1 were correct. RT-PCR results indicated that pSilencer 4.1-let-7a1 was effectively expressed in the transfected A549 cells. The relative luciferase activity was decreased significantly after A549 cells were co-transfected with pSilencer 4.1-let-7a1 and pMIR-report let-7a1T, indicating that let-7a1 was expressed effectively and had biologic activity in A549 cells that were transfected with pSilencer 4.1-let-7a1. MTT results showed that miRNA let-7a1 gene overexpression in A549 inhibited cell proliferation. CONCLUSION: The eukaryotic expression vector pSilencer 4.1-let-7a1 is successfully constructed and effectively expresses in A549 cell. The overexpression of miRNAlet-7a1 gene inhibits lung cancer A549 cell proliferation.     

Transfection of WT1 gene isoforms and establishment of leukemia cell lines stably overexpressing WT1 gene

AIM: To transfer 4 full-length WT1 isoforms cDNA into the leukemia cell line NB4 so as to provide a cell model for studying the WT-1 gene function. METHODS: The eukaryotic expression recombinant vectors for WT1 isoforms (pCB6+/WT1) were introduced into the leukemia cell line NB4 by electroporation. The positive cell clones were screened by G418 culture. The integration of WT1 gene isoforms in NB4 cells as confirmed by PCR. The mRNA and protein of WT1 were detected by RT-PCR and Western blotting. RESULTS: WT1 gene isoforms were successfully transferred into NB4 cells. WT1 mRNA and protein expression in the G418-selected cells increased remarkably compared with the control. CONCLUSION: WT1 gene isoforms were effectively transferred into NB4 cells by electroporation and stably expressed in the transfected cells.     

Construction of an immunoconjugate targeting tissue factor and its effect on colorectal cancer cells

AIM: To construct a recombinant eukaryotic expression vector pcDNA3.1(+)-hFVII-LC+hIgG1-Fc, and to produce and purify the immunoconjugate hFVII-LC+hIgG1-Fc protein. METHODS: The target sequences were amplified by RT-PCR from hepatic tissue and lymphocyte RNA, and cloned into eukaryotic expression vector pcDNA3.1(+). After confirmed by restriction endonuclease digestion and DNA sequencing, the recombinant plasmid was transfected into CHO-K1 cells by lipofectamine 2000. The transfectant clones were selected by G418 screening. The positive monoclonals were grown in CHO-K1 serum-free medium Excel 301 and the culture medium was collected. The hFVII-LC+hIgG1-Fc protein was purified by affinity Ni-NTA resin. The immunoconjugate was identified by ELISA with tissue factor (TF) affinity and specificity. Induction of NK cell-mediated antibody-dependent cell cytotoxicity(ADCC) was examined in HT-29 colorectal cancer cell line. RESULTS: Human liver tissue and lymphocytes from Han population were used as template for amplification of hFVII-LC and hIgG1-Fc DNA fragments, which were confirmed by sequencing and were exactly the same as those GenBank reported. The eukaryotic expression vector pcDNA3.1(+)-hFVII-LC+hIgG1-Fc was successfully constructed, and 1.3 mg of hFVII-LC+hIgG1-Fc protein could be prepared from 1 liter of Excel 301 serum-free culture medium through Ni-NTA affinity chromatography. The immunoconjugate was specially bound to TF and induced a significant ADCC response in HT-29 cells. CONCLUSION: The human hFVII-LC+hIgG1-Fc recombinant plasmid and the hFVII-LC+hIgG1-Fc immunoconjugate are obtained, which provide the basis for further study of cancer-targeted therapy.