ABSTRACT
Using the amino acids 1-147 of the yeast transcriptional activator GAL4 as the DNA-binding domain and four tandem repeats of the 12-aa peptide (DALDDFDLDMLG) of the herpesvirus as the activation domain, an artificial transcription factor, GVP4,was constructed via the linkage of the nuclear localization signal sequence of SV40. And then, GVP4 was cloned into expression vector pcDNA3 . 1/Hygro ( + ) . Various amounts of targeting sites of artificial transcription factor were linked to the upstream of promoter CMV in exogenous gene expression vector pcDNA3.1 ( + ) that separately harbored EGFP cDNA and t-PA cDNA.The CHO cells were then co-transfected with GVP4 expression vector and EGFP or t-PA expression vector. The effect of GVP4 on exogenous gene expression was evaluated by measuring the fluorescence intensity of EGFP in CHO cells and the concentration of t-PA in the supernatant. GVP4 showed positive effect on the enhancement of exogenous gene expression in CHO cells integrated with targeting sites of artificial transcription factor. And, CHO cells integrated with 10 targeting sites of GVP4 was more favorable to foreign gene expression, which resulted in 2-3-fold increase in both EGFP and t-PA expressions. These results indicated that artificial transcription factor is potent in the enhancement of exogenous gene expression in mammalian cells.
Subject(s)
Animals , Cricetinae , Amino Acid Sequence , CHO Cells , Cricetulus , Flow Cytometry , Gene Expression Regulation , Genetic Vectors , Genetics , Green Fluorescent Proteins , Genetics , Metabolism , Tissue Plasminogen Activator , Genetics , Metabolism , Transcription Factors , Genetics , Metabolism , Transcriptional Activation , TransfectionABSTRACT
After having successfully constructed and expressed the gene of the anti-CD3/anti-CD20 bispecific single-chain antibody (bscCD3 x CD20), here we analyzed its in vitro bioactivity of mediating the lysis of Ramous human B-lymphoma cells in the presence of T-enriched human peripheral blood lymphocytes (PBL). Obvious opoptosis characters were observed by Annexin V/PI(AV/PI) stained and scanning electron microscope. As evaluated by non-radioactive cytotoxity assay, the bscCD3 x CD20 showed potent bioactivity of mediating human B-lymphoma cells lysis in the presence of T-enriched human PBL. The potency of cytotoxicity depended on the ratios of effect cells to target cells (E:T) used. Further, the antibody showed a dose and time-dependent effect on mediating Ramous cells lysis. The specific lysis reached about 87.3% at an antibody concentration of 5microg/mL and E:T used at 10:1. Clear changes in apoptogenes expression profiles were detected by apoptosis gene array after Ramous cells were treated with the antibody and PBL. Among the upregulated apoptogenes, ATM and P53 showed an increase of 187 times and 15 times respectively, which suggested that ATM-p53 pathway may be the main apoptosis way of Ramous cells induced by T cells in the presence of the bscCD3 x CD20.
Subject(s)
Humans , Antibodies, Bispecific , Allergy and Immunology , Antigens, CD20 , Allergy and Immunology , Apoptosis , Allergy and Immunology , CD3 Complex , Allergy and Immunology , Lymphoma, B-Cell , Allergy and Immunology , Pathology , T-Lymphocytes, Cytotoxic , Allergy and Immunology , Tumor Cells, CulturedABSTRACT
Objective:To determine the optimal condition for mouse embryonic stem cells (mESC) culture with stirred bioreactor,and to develop a method for mass production of embryoid bodies (EB). Methods:The different initial cell concentrations of mESC and the initial stirring speed of bioreactor were investigated to determine the optimal condition for EB formation. Induced by ascorbic acid,the differentiation of EBs formed in stirred bioreactor into cardiomyocytes was compared with EBs formed in Petri dish. Immunofluorescence staining and RT-PCR were used to identify the cardiomyocytes derived from mESC. Results:The formation of a large number of uniform relatively EBs was achieved in stirred bioreactor when mESC were seeded initially with 1?105~3?105 cells/ml and stirring speed was set to 15~30r/min. Most of cells in the EBs formed in bioreactor were viable. EBs produced in bioreactor differentiated into cardiomyocytes more efficiently compared with EBs from Petri dish. The cardiac specific genes were expressed in ESC-derived cardiomyocytes. Conclusions:Stirred bioreactor culture could enhance the efficiency of EB formation and differentiation into cardiomyocytes,which may be a more ideal culture system for EB formation.
ABSTRACT
Retroviral expression system which consists of retroviral vector,envelop protein vector and packaging cell line is an efficient expression system for recombinant protein.It has great potential in gene therapy and biopharmacy.Transcriptional active genome regions are the preferred targets for retrovirus integration.Furthermore,VSV-G protein enables this system a broader host range and makes virus integration more efficient.After infection of high-titer virus,high production clones can be selected through simple screening.So far,the research on retrovirus expression system has developed into application in bio-pharmacy industry.Here the composition of this system and the mechanism of virus transduction and summarize the application and prospect of retroviral expression system are introduced.
ABSTRACT
Based on the different permeability of DNA-intercalant dyes YO-PRO-1(YP) and propidium iodide (PI) to the membrane of viable, apoptotic and necrotic cells, cell samples were stained with 4?mol/L YP and 4?g/ml PI for 10 min, and the fluorescence intensity of both YP and PI were measured by fluorometer at Ex/Em wavelength of 485/538nm and 530/590nm, respectively. The correlation between YP fluorescence intensity and the apoptotic cell number was confirmed by fluorescence microscope and linear regression(r=0.999,P
ABSTRACT
By using the cell density, cell viability, size distribution of cell aggregates,specific consumption rate of glucose (q_ glc ), specific production rate of lactate (q_ lac ), lactate transform rate (Y_ lac/glc ) and amino acids utilization as the evaluation indexes, the growth and metabolism of HEK293 cells under carrier-free immobilization culture mode were examined and compared with those of HEK293 cells cultured in static tissue flasks. It was found that HEK293 cells grown as suspended cell aggregates in spinner flasks maintained the basic growth and metabolism characteristics of HEK293 cells in stationary anchored culture, and HEK293 cells under carrier-free immobilization culture mode as suspended aggregates in stirred bioreactor facilitate perfusion performance and increase unit productivity. Cultivation of HEK293 cells in carrier-free immobilization culture mode has potential for further improving mammalian cells culture technique.
ABSTRACT
The synthetic gene with 1640bp encoding for the anti-CD3/anti-CD20 bispecific single-chain antibody was designed and obtained by SOE (splicing by overlap extension) PCR. The cDNA was cloned into Flp-In expression vector pcDNA5/FRT and transfeced into Flp-In CHO cells to generate a stable expression cell line with a capacity for expressing anti-CD3/anti-CD20 bispecific single-chain antibody at 300 microg/L. The protein, which had a molecular weight of about 70 kD,was purified by Ni-NTA affinity chromatography and identified by SDS-PAGE and Western-blot analysis. Immunofluorescence assay and cellular rosetting showed that it can react specifically on Jurkat (CD3+) and Ramous (CD20+) cells. The lysis of human PBL against CD20-positive lymphoma Ramous cells in the presence of the anti-CD3/anti-CD20 bispecific single-chain antibody can observed by microscope. All these results would lighten the further study of its biological functions in vitro and in vivo.