Advances in epigenetic regulation of Chinese hamster ovary cells / 生物工程学报

Chinese hamster ovary (CHO) cells play an irreplaceable role in biopharmaceuticals because the cells can be adapted to grow in suspension cultures and are capable of producing high quality biologics exhibiting human-like post-translational modifications. However, gene expression regulation such as transgene silencing and epigenetic modifications may reduce the recombinant protein production due to the decrease of expression stability of CHO cells. This paper summarized the role of epigenetic modifications in CHO cells, including DNA methylation, histone modification and miRNA, as well as their effects on gene expression regulation.

Increasing transgenic expression in recombinant Chinese hamster ovary cells using introns in different directions / 生物工程学报

The aim of this study is to investigate the effect of the chimeric intron in different directions on the expression of the nerve growth factor (NGF) in recombinant Chinese hamster ovary (CHO) cells. The chimeric intron that contained the splice sequence of the first intron of the human β-globin and the human immunoglobulin heavy chain variable region intron was used. NGF gene was cloned into the expression vectors containing the chimeric intron in the forward or reverse direction, followed by transfecting into CHO cells, and screened under G418 to produce the stable transfected CHO cells. Fluorescence quantitative PCR, ELISA, and Western blotting were performed to detect the recombinant NGF gene expression in CHO cells. The results showed that the chimeric introns could significantly enhance the expression of NGF in recombinant CHO cells. Moreover, the enhancing effect on NGF expression level by the intron in the forward direction showed stronger than that of the reverse direction both at mRNA and protein level. In conclusion, the chimeric intron could increase NGF expression in stably transfected CHO cells and the effect is associated with the direction of the intron insertion.

Effect of GC-rich DNA fragment on the level of transgene expression in Chinese hamster ovary cells and its position effect / 新乡医学院学报

Objective To analyze the effect of GC-rich DNA fragments on the level of transgenic expression in Chinese hamster ovary (CHO) celts and its position effect.Methods The synthetic DNA fragment with GC-rich was cloned into the 5'or 3'or both 5'and 3'ends of expression cassette of expression vector.Three new expression vectors (pIRES-G1,pIRES-G2 and pIRES-G3) which was inserted with the GC-rich DNA fragments in different position were transfected CHO ceils,respectively,and then was observed under fluorescence microscope;the control vector was pIRES-EGFP.Stable transfected cell lines were screened under G418,and enhanced green fluorescent protein(EGFP) expression was analyzed by flow cytometry and the transgenic copy number was detected by quantitative real-time quantitative polymerase chain reaction (qRT-PCR).Results Three expression vectors with a GC-rich DNA fragments in different position were constructed successfully.The insertion of GC-rich DNA fragments at 3'end and both 5',3'ends of the box of expression vector could obviously improve the expression level of vector in CHO cells;and the expression level of the stably transfected CHO cells increased 1.39 fold and 1.32 fold compared to the control vector,respectively;the transgene copy number increased 1.32 fold and 1.24 fold compared with the control vector.While the insertion of GC-rich DNA fragments at 5'end of expression cassette had no obvious effect on the level of gene expression.Conclusion The role of DNA fragment with GC-rich in improving the transgenic expression of CHO cells is related to its position in the vector.The insertion of GC-rich DNA fragments at 3'end and both 5',3'ends of the box of expression vector can improve transgenic expression.

Influence of different promoters on expression of transgene containing MAR expression vector in recombinant CHO cells / 重庆医学

Objective To investigate the effect of different promoters on the expression level of transgene containing MAR expression vector in recombinant CHO cells.Methods The CMV promoter and 3-globin MAR were amplified by PCR,then CMV promoter was replaced the SV40 promoter in pCAT1 for constructing the expression vector droved by CMV promoter.The control vectors of pCAT1 and pCAT2 without containing MAR were simultaneously transfected into the CHO cells.Then the stably transfected cell line was screened by G418.The CAT gene expression level was analyzed by ELISA.Results The expression level of CAT enzyme in the cells transfected with MAR-containing vectors was increased compared with the cells transfected by pCATG and pCAT3 vectors without containing MAR,which were increased by 1.75 and 1.25 times respectively(P＜0.05);but CAT enzyme expression level in the pCAT1 transfected cells droved by SV40 promotor with the MAR-containing expression vectors was 1.4 times higher than that in the pCAT2 vector droved by the CMV promoter(P＜0.05).Conclusion MAR can enhance the transgene expression level in stably recombinant CHO cells,and the promoting efficiency of SV40 promoter and MAR combination is superior to that of CMV promoter and MAR combination.

The expression and clinical significance of hsa-miR-144 in esophageal squamous cell carcinoma / 天津医药

Objective To investigate the expression of hsa-miR-144 in esophageal squamous cell carcinoma, and its relationship with clinicopathological features and prognosis. Methods Reverse transcriptase polymerase chain reaction (RT-PCR) method was used to detect the hsa-miR-144 in 46 cases of esophageal squamous cell carcinoma and adjacent normal tissue. The expression of hsa-miR-144 in esophageal squamous cell carcinoma and its difference in the clinicopatho?logical characteristics including gender, age, and tumor size were investigated. The relationship between the expression of hsa-miR-144 and prognosis of patients with esophageal squamous cell carcinoma was analyzed. Kaplan-Meier method and Log-rank test were used to analyse the differences in survival rates in different pathological characteristics. Results The ex?pression level of hsa-miR-144 was lower in esophageal squamous cell carcinoma 0.97(0.22-24.48)×10-6 than that of adjacent normal tissue 8.60(0.09-258.20)×10-6, the difference was statistically significant (Z=2.221, P0.05). There was no correlation between the expression of hsa-miR-144 and prognosis in patients with esophageal squamous cell carcino?ma (rs=0.031, P=0.839). In the survival rate, there was no statistic significance between high expressive of hsa-miR-144 group and low expressive group (P=0.828). The survival rate was lower in patients with lymph node metastasis than that of pa?tients without lymph node metastasis. The survival rates were lower in patients with relatively deep invasion and higher patho?logic stage (P<0.05). Conclusion The expression of hsa-miR-144 is down regulated in esophageal squamous cell carcino?ma, and which is associated with lymph node metastasis and pathological staging of esophageal carcinoma. It shows that hsa-miR-144 may serve as an anti-oncogene in the occurrence and development of esophageal squamous cell carcinoma.

Cloning of human csp-B matrix attachment region sequence and construction of its retrovirus vector / 中国组织工程研究

BACKGROUND:Matrix attachment region(MAR)are DNA elements that bound to the nuclear matrices after chromatin digested with restriction endonuclease.Plenty of studies have shown that MAR considered as initiaI point of DNA replication or transcription of regulatory gene.Thereby,construction of MAR expression vector can elevate the overall level of transgene expression,enhance stability of exogenous gene.as welI as increase frequency of stable transfectant cells.OBJECTIVE:To construction pLXSN-CAT recombinant retrovirus vector that containing chloramphenicol acetyltransferase(CAT)via cloning MAR sequence of human.and to explore the influence of MAR on the gene expression.METHODS:An open experiment was performed at the Department of Biochemistry and Molecular Biology.Xinxiang Medical College from September 2007 to December 2007 The PLXSN-CAT vector of CAT was constructed by the laboratory.TaqDNA polymerase,T_4 DNA ligase,DNA Marker,restriction enzyme BamH I,agarose gel DNA purification kit,as well as plasmid purification kit were purchased fromTakara Biotechn0Iogy(Dalian)Co.,Ltd.The sequence of csp-B MAR was amplified by polymerase chain reaction(PCR)method applied to human DNA.The fragment was inserted into retrovirus vector PLXSN-CAT plasmid.The recombinant plasmid was verified by double digestion and DNA sequencing.RESULTS AND CONCLUSION:The length of specific fragment applied by PCR was 931 bp,and the recombinant plasmid PLXSN-CAT-MAR presented two bands:5.9 kb and 931 bp using respective restriction enzymes BamH I The sequence of MAR was confirmed by blasting to Genbank(serial numobr:M6271 6).It suggested that MAR had been cloned into PLXSN-CATR vector correctly.The recombinant retrovirus vector PLXSN-MAR was successfully constructed.

Regulatory effect of human beta-interferon matrix attachment region on transgene expression in CHO cells / 中国组织工程研究

BACKGROUND: Matrix attachment region (MAR), a DNA sequence, is still bound to the nuclear matrices after chromatindigested with restriction endonuclease, not only affects expression of endogenous gene, but also overcames transgenic silence andimproves transcription and expression of exogenous gene. OBJECTIVE: To investigate the influence of ?-interferon MAR of CHO cells on the transgenic expression of chloramphenicolacetyltransferase (CAT). DESIGN, TIME AND SETTING: The opening experiment was performed at the Department of Biochemistry and MolecularBiology, Molecular Institute, Xinxiang Medical College from October 2006 to April 2007. MATERIALS: CHO cell lines were obtained from China Center for Type Culture Collection. The pCATG vector of CAT and G418screening markers were constructed by this laboratory. METHODS: Human ?-interferon MAR by PCR was digested with SacI/KpnI and BamHI/SalI, and was inserted into pCATGvector, which was propagated in Escherichia coli JM109, then extracted and purified followed by enzyme digestion analysis. Vectorof CAT expression cassette and human ?-interferon MAR by the two sides was successfully constructed, and christened aspCAT-MAR. Two methods were compared between CHO cells of pCATG transformation and CHO cells of pCATG-MARtransformation. After G418 selecting, genome DNA of cell lines of G418 was extracted, then primers for PCR to amplify the CATtarget gene fragment was designed. MAIN OUTCOME MEASURES: The activity of CAT was analyzed by ELISA method. It was also tested to see if thepCATG-MAR was stably integrated into genomic DNA in the transfected cells. RESULTS: CHO cells of pCATG transformation was screened to have 16 strains of positive cell, and CHO cells of pCATG-MARtransformation was screened to have 17 strains of positive cell. Human ?-interferon MAR could increase the CAT gene expressionby 2.8 fold. The coefficient of variation of CHO cells of pCATG transformation was 2.065 0, and coefficient of variation of CHOcells of pCATG-MAR transformation was 0.813 1. Genome DNA of stable transformation cell lines was amplified by a fragment of437 bp. The results confirmed the pCAT-MAR vector was stably integrated into genomic DNA. CONCLUSION: Human ?-interferon MAR can increase transgenic expression in CHO cells and decrease the transgenicexpression variation in different transfected cells.

MAR increased transgene expression in stable transfected CHO cells / 基础医学与临床

Objective To study the effect of human ?-globin matrix attachment region(MAR) on transgene expression in stably transfected CHO cells.Methods Expression vector was constructed,which contained the ?-globin MAR in both sides of Chloramphenicol acetyltransferase(CAT) reporter gene expression cassette in cis,then transfected into CHO cells.The CAT reporter gene expression was analyzed by ELISA method.Results The ?-globin MAR enhanced the CAT gene expression 5.5-fold in stably transformed CHO cells,while the transgene expression variation among individuals of transformants was decreased.Conclusion MAR increase transgene expression in stably transfected CHO cells.

Cloning of the human β-globin MAR and construction of the pCAT-MAR expression vector / 新乡医学院学报

Objective To clone the human β-globin matrix attachment region(MAR) and construct the mammalian animal expression vector pCAT-MAR, which contains the MAR and CAT reporter gene.Methods The human genomic DNA was extracted through phenol/chloroform and precipitated with ethanol, followed the MAR was amplified through PCR using the primers designed according to the GenBank sequence. After identified by agarose gel electrophoresis, sequenced and analyzed by the software, the PCR products were cut with restriction enzymes and ligated into the pCAT3-control vector to construct the pCAT-MAR vector. Results About 770bp band appeared in the agarose gel electrophoresis, the similarly compared with the published MAR sequence was 99.9%, the DNA fragment has the MAR typical features. The pCAT-MAR vector was demonstrated to be right through digestion with the corresponding enzymes and agarose gel electrophoresis. Conclusion The humanβ-globin MAR is cloned through PCR, and the expression vector pCAT-MAR containing the MAR is successfully constructed.

Effect of medium composition on the growth and Sporulation of Bacillus sp WTFY / 新乡医学院学报

Objective Study the relationship between the component of medium and spore formation of Bacillus sp WTFY. Methods Alter the carbon source、nitrogen source、inorganic concentration and kinds in turns, observe the sporulation circumstances of Bacillus sp WTFY.Results When glucose concentration was higher over 0.1%, spore did not emerge;Nitrogen source、phosphorus、magnesiumions concentration and kinds have some degree influence,but not significantly.Conclusion Carbon source concentration is a key factor that influence spore formation.

Cloning and expression of mouse canstatin cDNA in E.coli / 中国病理生理杂志

AIM: To clone and express mouse canstatin (m canstatin)cDNA and provide a basis for the further research on its anti-angiogenic activity and potential application for cancer therapy. METHODS: Total RNA was extracted from mouse liver tissue by Trizol Reagent, and mouse canstatin cDNA was amplified by RT- PCR, then cloned into vector pMD18-T for sequencing. pET30a(+)-m canstatin recombinant plasmid was constructed and expressed in E.coli BL21 with induction of IPTG. RESULTS: Mouse canstatin cDNA is 684 bp coding 227 amino acids. The sequences of both cDNA and amino acid share high homology with human canstatin, with cDNA identity at 89% and amino acids identity at 96% to human canstatin. In the present study, pET30a(+)-m canstatin recombinant plasmid was expressed in E.coli BL21. CONCLUSION: Mouse canstatin cDNA has been cloned for the first time. Constructed pET30a(+)-m canstatin recombinant plasmid is highly expressed in E.coli BL21.