1
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Wang XY, Zhang WL, Zhang X, Fu YS, Wang HM, Sun QL, Li Q, Jia YL, Zhang JH, Wang TY. Combination of MAR and intron increase transgene expression of episomal vectors in CHO cells. Biotechnol J 2023; 18:e2200643. [PMID: 37551822 DOI: 10.1002/biot.202200643] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Revised: 07/22/2023] [Accepted: 08/03/2023] [Indexed: 08/09/2023]
Abstract
Previous work has shown that the EF-1α promoter of episomal vectors maintains high-level transgene expression in stably transfected Chinese hamster ovary (CHO) cells. However, the transgene expression levels need to be further increased. Here, we first incorporated matrix attachment regions (MARs), ubiquitous chromatin opening element (UCOE), stabilizing anti repressor elements 40 (STAR 40) elements into episomal vector at different sites and orientations, and systemically assessed their effects on transgene expression in transfected CHO-K1 cells. Results showed that enhanced green fluorescent protein (eGFP) expression levels increased remarkably when MAR X-29 was inserted upstream of the promoter, followed by the insertion of MAR1 downstream of the poly A, and the orientation had no significant effect. Moreover, MAR X-29 combined with human cytomegalovirus intron (hCMVI) yielded the highest transgene expression levels (4.52-fold). Transgene expression levels were not exclusively dependent on transgene copy numbers and were not related to the mRNA expression level. In addition, vector with MAR X-29+hCMVI can induce herpes simplex virus thymidine kinase (HSV-TK) protein expression, and the HSV-TK protein showed a cell-killing effect and an obvious bystander effect on HCT116 cells. In conclusion, the combination of MAR X-29 and hCMV intron can achieve high efficiency transgene expression mediated by episomal vectors in CHO-K1 cells.
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Affiliation(s)
- Xiao-Yin Wang
- School of Basic Medical Science, Xinxiang Medical University, Xinxiang, China
- International Joint Research Laboratory for Recombinant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang, China
| | - Wei-Li Zhang
- School of Basic Medical Science, Xinxiang Medical University, Xinxiang, China
- Center for Medical Genetics, Nanyang Second General Hospital, Nanyang, China
| | - Xi Zhang
- College of Pharmacy, Xinxiang Medical University, Xinxiang, China
| | - Yu-Shun Fu
- School of Basic Medical Science, Xinxiang Medical University, Xinxiang, China
| | - Hao-Min Wang
- School of Basic Medical Science, Xinxiang Medical University, Xinxiang, China
| | - Qiu-Li Sun
- International Joint Research Laboratory for Recombinant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang, China
| | - Qin Li
- School of Basic Medical Science, Xinxiang Medical University, Xinxiang, China
| | - Yan-Long Jia
- College of Pharmacy, Xinxiang Medical University, Xinxiang, China
| | - Jun-He Zhang
- Institutes of Health Central Plains, Xinxiang Medical University, Xinxiang, China
| | - Tian-Yun Wang
- School of Basic Medical Science, Xinxiang Medical University, Xinxiang, China
- International Joint Research Laboratory for Recombinant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang, China
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2
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Zhang J, Wang TY, Zhang C, Mi C, Geng S, Tang Y, Wang X. CMV/AAT promoter of MAR-based episomal vector enhanced transgene expression in human hepatic cells. 3 Biotech 2023; 13:354. [PMID: 37810190 PMCID: PMC10558423 DOI: 10.1007/s13205-023-03774-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2023] [Accepted: 09/13/2023] [Indexed: 10/10/2023] Open
Abstract
We have previously developed a non-viral episomal vector based on matrix attachment region (MAR) that can facilitate plasmid replication episomally in mammal cells. In this study, we have focused on the development of an alternative tissue specific episomal vector by incorporating into cis-acting elements. We found that AAT promoter demonstrated the highest eGFP expression level in HepG2, Huh-7 and HL-7702 hepatic cells. Furthermore, hCMV enhancer when combined with AAT promoter significantly improved the eGFP expression level in the transfected HepG2 cells. The mean fluorescence intensity of eGFP in hCMV2 group was 1.33 fold, which was higher than that of the control (p < 0.01), followed by the hCMV1 group (1.21 fold). In addition, the percentages of eGFP-expressing cells in hCMV1 and hCMV2 groups were observed to be 49.3% and 57.2%, which were significantly higher than that of the enhancer-devoid control vector (44.3%) (p < 0.05). Moreover, the eGFP protein were up to 3.5 fold and 5.1 fold (p < 0.05), respectively. This observation could be related with the activities of some specific transcription factors (TFs) during the transcriptional process, such as SRF, REL and CREB1. The composite CMV/AAT promoter can be thus used for efficient transgene expression of MAR-based episomal vector in liver cells and as a potential gene transfer tools for the management of liver diseases. Supplementary Information The online version contains supplementary material available at 10.1007/s13205-023-03774-x.
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Affiliation(s)
- Jihong Zhang
- School of Basic Medical Sciences, Xinxiang Medical University, No. 601 Jinsui Road, Xinxiang, 453003 Henan Province China
- International Joint Research Laboratory for Recombinant Pharmaceutical Protein Expression System of Henan, Xinxiang, 453003 China
| | - Tian-Yun Wang
- School of Basic Medical Sciences, Xinxiang Medical University, No. 601 Jinsui Road, Xinxiang, 453003 Henan Province China
- International Joint Research Laboratory for Recombinant Pharmaceutical Protein Expression System of Henan, Xinxiang, 453003 China
| | - Chunbo Zhang
- College of Life Science, Henan Normal University, Xinxiang, 453000 China
| | - Chunliu Mi
- School of Basic Medical Sciences, Xinxiang Medical University, No. 601 Jinsui Road, Xinxiang, 453003 Henan Province China
- International Joint Research Laboratory for Recombinant Pharmaceutical Protein Expression System of Henan, Xinxiang, 453003 China
| | - Shaolei Geng
- School of Basic Medical Sciences, Xinxiang Medical University, No. 601 Jinsui Road, Xinxiang, 453003 Henan Province China
- International Joint Research Laboratory for Recombinant Pharmaceutical Protein Expression System of Henan, Xinxiang, 453003 China
| | - Yuanyuan Tang
- School of Basic Medical Sciences, Xinxiang Medical University, No. 601 Jinsui Road, Xinxiang, 453003 Henan Province China
| | - Xiaoyin Wang
- School of Basic Medical Sciences, Xinxiang Medical University, No. 601 Jinsui Road, Xinxiang, 453003 Henan Province China
- International Joint Research Laboratory for Recombinant Pharmaceutical Protein Expression System of Henan, Xinxiang, 453003 China
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3
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Khan SU, Khan MU, Khan MI, Kalsoom F, Zahra A. Current Landscape and Emerging Opportunities of Gene Therapy with Non-viral Episomal Vectors. Curr Gene Ther 2023; 23:135-147. [PMID: 36200188 DOI: 10.2174/1566523222666221004100858] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 06/10/2022] [Accepted: 06/10/2022] [Indexed: 11/22/2022]
Abstract
Gene therapy has proven to be extremely beneficial in the management of a wide range of genetic disorders for which there are currently no or few effective treatments. Gene transfer vectors are very significant in the field of gene therapy. It is possible to attach a non-viral attachment vector to the donor cell chromosome instead of integrating it, eliminating the negative consequences of both viral and integrated vectors. It is a safe and optimal express vector for gene therapy because it does not cause any adverse effects. However, the modest cloning rate, low expression, and low clone number make it unsuitable for use in gene therapy. Since the first generation of non-viral attachment episomal vectors was constructed, various steps have been taken to regulate their expression and stability, such as truncating the MAR element, lowering the amount of CpG motifs, choosing appropriate promoters and utilizing regulatory elements. This increases the transfection effectiveness of the non-viral attachment vector while also causing it to express at a high level and maintain a high level of stability. A vector is a genetic construct commonly employed in gene therapy to treat various systemic disorders. This article examines the progress made in the development of various optimization tactics for nonviral attachment vectors and the future applications of these vectors in gene therapy.
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Affiliation(s)
- Safir Ullah Khan
- Hefei National Laboratory for Physical Sciences at the Microscale, School of Life Sciences, University of Science and Technology of China, Hefei 230027, People's Republic of China
| | - Munir Ullah Khan
- MOE Key Laboratory of Macromolecular Synthesis and Functionalization, International Research Center for X Polymers, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou, 310027 China
| | - Muhammad Imran Khan
- School of Life Sciences and Medicine, University of Science and Technology of China,Hefei 230027,People's Republic of China
- Department of Pathology, District Headquarters Hospital Jhang 35200, Punjab Province, Islamic Republic of Pakistan
| | - Fadia Kalsoom
- Department of Pathology, District Headquarters Hospital Jhang 35200, Punjab Province, Islamic Republic of Pakistan
| | - Aqeela Zahra
- Department of Family and Community Medicine. College of Medicine, University of Ha'il, Ha'il 81451, Saudi Arabia
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4
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Dynamics of nuclear matrix attachment regions during 5 th instar posterior silk gland development in Bombyx mori. BMC Genomics 2022; 23:247. [PMID: 35361117 PMCID: PMC8973518 DOI: 10.1186/s12864-022-08446-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Accepted: 03/06/2022] [Indexed: 12/02/2022] Open
Abstract
Background Chromatin architecture is critical for gene expression during development. Matrix attachment regions (MARs) control and regulate chromatin dynamics. The position of MARs in the genome determines the expression of genes in the organism. In this study, we set out to elucidate how MARs temporally regulate the expression of the fibroin heavy chain (FIBH) gene during development. We addressed this by identifying MARs and studying their distribution and differentiation, in the posterior silk glands of Bombyx mori during 5th instar development. Results Of the MARs identified on three different days, 7.15% MARs were common to all 3 days, whereas, 1.41, 19.27 and 52.47% MARs were unique to day 1, day 5, and day 7, respectively highlighting the dynamic nature of the matrix associated DNA. The average chromatin loop length based on the chromosome wise distribution of MARs and the distances between these MAR regions decreased from day 1 (253.91 kb) to day 5 (73.54 kb) to day 7 (39.19 kb). Further significant changes in the MARs in the vicinity of the FIBH gene were found during different days of 5th instar development which implied their role in the regulation and expression of the FIBH gene. Conclusions The presence of MARs in the flanking regions of genes found to exhibit differential expression during 5th instar development indicates their possible role in the regulation of their expression. This reiterates the importance of MARs in the genomic functioning as regulators of the molecular mechanisms in the nucleus. This is the first study that takes into account the tissue specific genome-wide MAR association and the potential role of these MARs in developmentally regulated gene expression. The current study lays a foundation to understand the genome wide regulation of chromatin during development. Supplementary Information The online version contains supplementary material available at 10.1186/s12864-022-08446-3.
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Wang X, Zhang W, Jia Y, Wang M, Yi D, Wang TY. Woodchuck hepatitis post-transcriptional regulatory element improves transgene expression and stability mediated by episomal vectors in CHO-K1 cells. Acta Biochim Biophys Sin (Shanghai) 2020; 52:1285-1288. [PMID: 33196825 DOI: 10.1093/abbs/gmaa105] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Revised: 08/02/2020] [Accepted: 08/09/2020] [Indexed: 11/13/2022] Open
Affiliation(s)
- Xiaoyin Wang
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang 453003, China
- International Joint Research Laboratory for Recombinant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang 453003, China
| | - Weili Zhang
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang 453003, China
| | - Yanlong Jia
- Pharmacy College, Xinxiang Medical University, Xinxiang 453003, China
| | - Meng Wang
- International Joint Research Laboratory for Recombinant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang 453003, China
| | - Dandan Yi
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang 453003, China
- International Joint Research Laboratory for Recombinant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang 453003, China
| | - Tian-yun Wang
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang 453003, China
- International Joint Research Laboratory for Recombinant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang 453003, China
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6
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Dou Y, Lin Y, Wang TY, Wang XY, Jia YL, Zhao CP. The CAG promoter maintains high-level transgene expression in HEK293 cells. FEBS Open Bio 2020; 11:95-104. [PMID: 33155423 PMCID: PMC7780116 DOI: 10.1002/2211-5463.13029] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 10/03/2020] [Accepted: 11/04/2020] [Indexed: 12/11/2022] Open
Abstract
The vast majority of therapeutic recombinant proteins are produced in mammalian cell lines. However, proteins generated in nonhuman cell lines, such as Chinese hamster ovary (CHO) cells, are decorated with human‐like glycan structures that differ from those of human cells, and these may induce immunogenic responses in human cells. Human embryonic kidney cells (HEK293F) are also extensively used as hosts for the expression of recombinant therapeutic proteins, but their utility is limited by the low expression of transgenes in these cells. Here, we investigated recombinant protein expression from eight frequently used promoters in transfected HEK293F cells. The expression levels and stability of the transgenes were evaluated by flow cytometry and qRT‐PCR. The most efficient expression (in terms of both mRNA and protein yields) was achieved using a cytomegalovirus (CMV) major immediate‐early enhancer combined with the chicken beta‐actin promoter (CAG) promoter, as compared to all other tested promoters under both transient and stable transfection conditions. In addition, application of mild hypothermia (i.e., 33 °C) after transfection improved the positive effect of the CMV enhancer fused to the chicken beta‐actin promoter (CAG promoter) on enhanced green fluorescent protein (eGFP) expression. Although the temperature sensitivity of the CMV promoter is greater than that of CAG promoter, recombinant protein levels were still highest when expression was driven by the CAG promoter. When eGFP was replaced with hepatitis B surface antigen, the CAG promoter still showed the highest transgene expression. In conclusion, our data show that the CAG promoter is a strong promoter for recombinant protein expression in HEK293F cells.
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Affiliation(s)
- Yuanyuan Dou
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, China.,Henan Collaborative Innovation Center of Molecular Diagnosis and Laboratory Medicine, Xinxiang, China
| | - Yan Lin
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, China
| | - Tian-Yun Wang
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, China
| | - Xiao-Yin Wang
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, China
| | - Yan-Long Jia
- Henan Collaborative Innovation Center of Molecular Diagnosis and Laboratory Medicine, Xinxiang, China
| | - Chun-Peng Zhao
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, China
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7
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Xu ZJ, Jia YL, Wang M, Yi DD, Zhang WL, Wang XY, Zhang JH. Effect of promoter, promoter mutation and enhancer on transgene expression mediated by episomal vectors in transfected HEK293, Chang liver and primary cells. Bioengineered 2020; 10:548-560. [PMID: 31668126 PMCID: PMC6844389 DOI: 10.1080/21655979.2019.1684863] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The episomal vector cannot integrate into the host cell chromosome, which has no potential risk in gene therapy. However, the low level of transgene expression driven by episomal vectors needs to be solved. In this study, we investigated the effects of enhancers, promoters and promoter variants on transgene expression levels driven by episomal vectors in HEK293, Chang liver and primary cells. Results showed that all eight cis-acting elements used could increase transfection efficiency and transient eGFP expression in transfected HEK293 and Chang liver cells. In stably transfected mammalian cells, the elongation factor-1 alpha (EF-1α) promoter and mutant-404 showed high and stable transgene expression. The mechanisms might be related to the type and quantity of transcription factor regulatory elements. Moreover, quantitative reverse transcription polymerase chain reaction analysis showed that mRNA expression levels were not directly proportional to protein expression levels. Furthermore, the EF-1α promoter conferred high transgene expression levels in primary cells, and the plasmid was also present in the episomal state. Taken together, these results provided valuable information for improving transgene expression with episomal vectors in mammalian cells.
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Affiliation(s)
- Zhong-Jie Xu
- Life Science and Technology, Xinxiang Medical University, Xinxiang, Henan, China
| | - Yan-Long Jia
- Pharmacy collage, Xinxiang Medical University, Xinxiang, Henan, China
| | - Meng Wang
- International Joint Research Laboratory for Recombiant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang, Henan, China
| | - Dan-Dan Yi
- International Joint Research Laboratory for Recombiant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang, Henan, China.,Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang, Henan, China
| | - Wei-Li Zhang
- International Joint Research Laboratory for Recombiant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang, Henan, China.,Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang, Henan, China
| | - Xiao-Yin Wang
- International Joint Research Laboratory for Recombiant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang, Henan, China.,Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang, Henan, China
| | - Jun-He Zhang
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang, Henan, China
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8
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Wadhwa A, Aljabbari A, Lokras A, Foged C, Thakur A. Opportunities and Challenges in the Delivery of mRNA-based Vaccines. Pharmaceutics 2020; 12:E102. [PMID: 32013049 PMCID: PMC7076378 DOI: 10.3390/pharmaceutics12020102] [Citation(s) in RCA: 277] [Impact Index Per Article: 69.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2019] [Revised: 01/22/2020] [Accepted: 01/26/2020] [Indexed: 02/08/2023] Open
Abstract
In the past few years, there has been increasing focus on the use of messenger RNA (mRNA) as a new therapeutic modality. Current clinical efforts encompassing mRNA-based drugs are directed toward infectious disease vaccines, cancer immunotherapies, therapeutic protein replacement therapies, and treatment of genetic diseases. However, challenges that impede the successful translation of these molecules into drugs are that (i) mRNA is a very large molecule, (ii) it is intrinsically unstable and prone to degradation by nucleases, and (iii) it activates the immune system. Although some of these challenges have been partially solved by means of chemical modification of the mRNA, intracellular delivery of mRNA still represents a major hurdle. The clinical translation of mRNA-based therapeutics requires delivery technologies that can ensure stabilization of mRNA under physiological conditions. Here, we (i) review opportunities and challenges in the delivery of mRNA-based therapeutics with a focus on non-viral delivery systems, (ii) present the clinical status of mRNA vaccines, and (iii) highlight perspectives on the future of this promising new type of medicine.
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Affiliation(s)
| | | | | | | | - Aneesh Thakur
- Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen Ø, Denmark
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9
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Wang XY, Zhang X, Wang TY, Jia YL, Xu DH, Yi DD. Shortened nuclear matrix attachment regions are sufficient for replication and maintenance of episomes in mammalian cells. Mol Biol Cell 2019; 30:2761-2770. [PMID: 31509492 PMCID: PMC6789156 DOI: 10.1091/mbc.e19-02-0108] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Matrix attachment regions (MARs) can mediate the replication of vector episomes in mammalian cells; however, the molecular mode of action remains unclear. Here, we assessed the characteristics of MARs and the mechanism that mediates episomal vector replication in mammalian cells. Five shortened subfragments of β-interferon MAR fragments were cloned and transferred into CHO cells, and transgene expression levels, presence of the gene, and the episomal maintenance mechanism were determined. Three shortened MAR derivatives (position 781–1320, 1201–1740, and 1621–2201) retained full MAR activity and mediated episomal vector replication. Moreover, the three shortened MARs showed higher transgene expression levels, greater efficiency in colony formation, and more persistent transgene expression compared with those of the original pEPI-1 plasmid, and three functional truncated MARs can bind to SAF-A MAR-binding protein. These results suggest that shortened MARs are sufficient for replication and maintenance of episomes in CHO cells.
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Affiliation(s)
- Xiao-Yin Wang
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang 453003, Henan, China.,International Joint Research Laboratory for Recombiant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang 453003, Henan, China
| | - Xi Zhang
- International Joint Research Laboratory for Recombiant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang 453003, Henan, China
| | - Tian-Yun Wang
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang 453003, Henan, China.,International Joint Research Laboratory for Recombiant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang 453003, Henan, China
| | - Yan-Long Jia
- Pharmacy Collage, Xinxiang Medical University, Xinxiang 453003, Henan, China
| | - Dan-Hua Xu
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang 453003, Henan, China.,International Joint Research Laboratory for Recombiant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang 453003, Henan, China
| | - Dan-Dan Yi
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang 453003, Henan, China.,International Joint Research Laboratory for Recombiant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang 453003, Henan, China
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10
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Wang XY, Yi DD, Wang TY, Wu YF, Chai YR, Xu DH, Zhao CP, Song C. Enhancing expression level and stability of transgene mediated by episomal vector via buffering DNA methyltransferase in transfected CHO cells. J Cell Biochem 2019; 120:15661-15670. [PMID: 31074065 DOI: 10.1002/jcb.28835] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Revised: 02/01/2019] [Accepted: 02/04/2019] [Indexed: 12/17/2022]
Abstract
Nonviral episomal vectors present attractive alternative vehicles for gene therapy applications. Previously, we have established a new type of nonviral episomal vector-mediated by the characteristic motifs of matrix attachment regions (MARs), which is driven by the cytomegalovirus (CMV) promoter. However, the CMV promoter is intrinsically susceptible to silencing, resulting in declined productivity during long-term culture. In this study, Chinese hamster ovary (CHO) cells and DNA methyltransferase-deficient (Dnmt3a-deficient) CHO cells were transfected with plasmid-mediated by MAR, or CHO cells were treated with the DNA methylation inhibitor 5-Aza-2'-deoxycytidine. Flow cytometry, plasmid rescue experiments, fluorescence in-situ hybridization (FISH), and bisulfite sequencing were performed to observe transgene expression, its state of existence, and the CpG methylation level of the CMV promoter. The results indicated that all DNA methylation inhibitor and methyltransferase deficient cells could increase transgene expression levels and stability in the presence or absence of selection pressure after a 60-generation culture. Plasmid rescue assay and FISH analysis showed that the vector still existed episomally after long-time culture. Moreover, a relatively lower CMV promoter methylation level was observed in Dnmt3a-deficient cell lines and CHO cells treated with 5-Aza-2'-deoxycytidine. In addition, Dnmt3a-deficient cells were superior to the DNA methylation inhibitor treatment regarding the transgene expression and long-term stability. Our study provides the first evidence that lower DNA methyltransferase can enhance expression level and stability of transgenes mediated by episomal vectors in transfected CHO cells.
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Affiliation(s)
- Xiao-Yin Wang
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang, Henan, China.,International Joint Research Laboratory for Recombiant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang, Henan, China
| | - Dan-Dan Yi
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang, Henan, China
| | - Tian-Yun Wang
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang, Henan, China.,International Joint Research Laboratory for Recombiant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang, Henan, China
| | - Yan-Fang Wu
- Department of Pharmacy, Medical College, Henan University of Science and Technology, Luoyang, China
| | - Yu-Rong Chai
- Department of Histology and Embryology, School of Basic Medical Sciences, University of Zhengzhou, Zhengzhou, Henan, China
| | - Dan-Hua Xu
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang, Henan, China
| | - Chun-Peng Zhao
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang, Henan, China
| | - Chao Song
- International Joint Research Laboratory for Recombiant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang, Henan, China
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11
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Wagner S, McCracken J, Bruszies S, Broadhurst R, Wells DN, Oback B, Bode J, Laible G. Episomal minicircles persist in periods of transcriptional inactivity and can be transmitted through somatic cell nuclear transfer into bovine embryos. Mol Biol Rep 2019; 46:1737-1746. [PMID: 30694456 DOI: 10.1007/s11033-019-04624-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 01/18/2019] [Indexed: 12/14/2022]
Abstract
Episomal plasmids based on a scaffold/matrix attachment region (S/MAR) are extrachromosomal DNA entities that replicate once per cell cycle and are stably maintained in cells or tissue. We generated minicircles, episomal plasmids devoid of bacterial sequences, and show that they are stably transmitted in clonal primary bovine fibroblasts without selection pressure over more than two months. Total DNA, plasmid extraction and fluorescence in situ hybridization (FISH) analyses suggest that the minicircles remained episomal and were not integrated into the genome. Minicircles survived extended periods in serum-starved cells, which indicates that ongoing transcription in non-proliferating cells is not necessary for the maintenance of S/MAR-episomes. To test whether minicircles endure the process of somatic cell nuclear transfer (SCNT), we used cell-cycle synchronized, serum-starved, minicircle-containing cells. Analysis of cells outgrown from SCNT-derived blastocysts shows that the minicircles are maintained through SCNT and early embryonic development, which raises the prospect of using cell lines with episomal minicircles for the generation of transgenic animals.
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Affiliation(s)
- Stefan Wagner
- AgResearch Limited, Ruakura Research Centre, Hamilton, 3240, New Zealand. .,Rowett Institute, University of Aberdeen, Aberdeen, AB25 2ZD, UK.
| | - Judi McCracken
- AgResearch Limited, Ruakura Research Centre, Hamilton, 3240, New Zealand
| | - Sabine Bruszies
- AgResearch Limited, Ruakura Research Centre, Hamilton, 3240, New Zealand
| | - Ric Broadhurst
- AgResearch Limited, Ruakura Research Centre, Hamilton, 3240, New Zealand
| | - David N Wells
- AgResearch Limited, Ruakura Research Centre, Hamilton, 3240, New Zealand
| | - Björn Oback
- AgResearch Limited, Ruakura Research Centre, Hamilton, 3240, New Zealand
| | - Jürgen Bode
- Hannover Medical School (MHH), Carl-Neuberg-Strasse 1, 30625, Hannover, Germany
| | - Götz Laible
- AgResearch Limited, Ruakura Research Centre, Hamilton, 3240, New Zealand
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12
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Human rhinovirus internal ribosome entry site element enhances transgene expression in transfected CHO-S cells. Sci Rep 2018; 8:6661. [PMID: 29703950 PMCID: PMC5923211 DOI: 10.1038/s41598-018-25049-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Accepted: 04/13/2018] [Indexed: 01/27/2023] Open
Abstract
Chinese hamster ovary (CHO) cells are mainly used for recombinant protein production. However, the unstable transgene expression and lower transgene copy numbers are the major issues need to be resolved. Here, eleven internal ribosome entry site (IRES) elements from viral and cellular IRES were evaluated for foreign gene expression in CHO-S cells. We constructed eleven fusing plasmids containing different IRES sequences downstream of the enhanced green fluorescent protein (EGFP) gene. EGFP expression was detected by flow cytometry and the transgene copy number was evaluated by quantitative PCR. The erythropoietin (EPO) protein was also used to assess the stronger IRES. The results showed that IRES from human rhinovirus (HRV) exhibited the highest EGFP expression level under transient and stable transfections. The EGFP expression level of vector with IRES from HRV was related to the gene copy number in stably transfected CHO-S cells. Moreover, IRES from HRV induced higher expression level of EPO compared with one mutant IRES from EMCV in transfected cells. In conclusion, IRES from HRV can function as a strong IRES element for stable expression in CHO-S cells, which could potentially guide more effective foreign gene expression in CHO-S cells.
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Xu DH, Wang XY, Jia YL, Wang TY, Tian ZW, Feng X, Zhang YN. SV40 intron, a potent strong intron element that effectively increases transgene expression in transfected Chinese hamster ovary cells. J Cell Mol Med 2018; 22:2231-2239. [PMID: 29441681 PMCID: PMC5867124 DOI: 10.1111/jcmm.13504] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Accepted: 11/15/2017] [Indexed: 12/20/2022] Open
Abstract
Chinese hamster ovary (CHO) cells have become the most widely utilized mammalian cell line for the production of recombinant proteins. However, the product yield and transgene instability need to be further increased and solved. In this study, we investigated the effect of five different introns on transgene expression in CHO cells. hCMV intron A, adenovirus tripartite leader sequence intron, SV40 intron, Chinese hamster EF-1alpha gene intron 1 and intervening sequence intron were cloned downstream of the eGFP expression cassette in a eukaryotic vector, which was then transfected into CHO cells. qRT-PCR and flow cytometry were used to explore eGFP expression levels. And gene copy number was also detected by qPCR, respectively. Furthermore, the erythropoietin (EPO) protein was used to test the selected more strong intron. The results showed that SV40 intron exhibited the highest transgene expression level among the five compared intron elements under transient and stable transfections. In addition, the SV40 intron element can increase the ratio of positive colonies and decrease the coefficient of variation in transgene expression level. Moreover, the transgene expression level was not related to the gene copy number in stable transfected CHO cells. Also, the SV40 intron induced higher level of EPO expression than IVS intron in transfected CHO cell. In conclusion, SV40 intron is a potent strong intron element that increases transgene expression, which can readily be used to more efficient transgenic protein production in CHO cells.
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Affiliation(s)
- Dan-Hua Xu
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang, Henan, China
| | - Xiao-Yin Wang
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang, Henan, China
| | - Yan-Long Jia
- Pharmacy collage, Xinxiang Medical University, Xinxiang, Henan, China
| | - Tian-Yun Wang
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang, Henan, China
| | - Zheng-Wei Tian
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang, Henan, China
| | - Xin Feng
- Grade 2014, The Third Clinical Medical College of Xinxiang Medical University, Xinxiang, Henan, China
| | - Yin-Na Zhang
- Grade 2014, The Third Clinical Medical College of Xinxiang Medical University, Xinxiang, Henan, China
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Impact of different promoters, promoter mutation, and an enhancer on recombinant protein expression in CHO cells. Sci Rep 2017; 7:10416. [PMID: 28874794 PMCID: PMC5585415 DOI: 10.1038/s41598-017-10966-y] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Accepted: 08/17/2017] [Indexed: 11/09/2022] Open
Abstract
In the present study, six commonly used promoters, including cytomegalovirus major immediate-early (CMV), the CMV enhancer fused to the chicken beta-actin promoter (CAG), human elongation factor-1α (HEF-1α), mouse cytomegalovirus (mouse CMV), Chinese hamster elongation factor-1α (CHEF-1α), and phosphoglycerate kinase (PGK), a CMV promoter mutant and a CAG enhancer, were evaluated to determine their effects on transgene expression and stability in transfected CHO cells. The promoters and enhancer were cloned or synthesized, and mutation at C-404 in the CMV promoter was generated; then all elements were transfected into CHO cells. Stably transfected CHO cells were identified via screening under the selection pressure of G418. Flow cytometry, qPCR, and qRT-PCR were used to explore eGFP expression levels, gene copy number, and mRNA expression levels, respectively. Furthermore, the erythropoietin (EPO) gene was used to test the selected strong promoter. Of the six promoters, the CHEF-1α promoter yielded the highest transgene expression levels, whereas the CMV promoter maintained transgene expression more stably during long-term culture of cells. We conclude that CHEF-1α promoter conferred higher level of EPO expression in CHO cells, but the CMV promoter with its high levels of stability performs best in this vector system.
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Wang X, Xu Z, Tian Z, Zhang X, Xu D, Li Q, Zhang J, Wang T. The EF-1α promoter maintains high-level transgene expression from episomal vectors in transfected CHO-K1 cells. J Cell Mol Med 2017; 21:3044-3054. [PMID: 28557288 PMCID: PMC5661254 DOI: 10.1111/jcmm.13216] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2017] [Accepted: 04/01/2017] [Indexed: 02/03/2023] Open
Abstract
In our previous study, we demonstrated that episomal vectors based on the characteristic sequence of matrix attachment regions (MARs) and containing the cytomegalovirus (CMV) promoter allow transgenes to be maintained episomally in Chinese hamster ovary (CHO) cells. However, the transgene expression was unstable and the number of copies was low. In this study, we focused on enhancers, various promoters and promoter variants that could improve the transgene expression stability, expression magnitude (level) and the copy number of a MAR‐based episomal vector in CHO‐K1 cells. In comparison with the CMV promoter, the eukaryotic translation elongation factor 1 α (EF‐1α, gene symbol EEF1A1) promoter increased the transfection efficiency, the transgene expression, the proportion of expression‐positive clones and the copy number of the episomal vector in long‐term culture. By contrast, no significant positive effects were observed with an enhancer, CMV promoter variants or CAG promoter in the episomal vector in long‐term culture. Moreover, the high‐expression clones harbouring the EF‐1α promoter tended to be more stable in long‐term culture, even in the absence of selection pressure. According to these findings, we concluded that the EF‐1α promoter is a potent regulatory sequence for episomal vectors because it maintains high transgene expression, transgene stability and copy number. These results provide valuable information on improvement of transgene stability and the copy number of episomal vectors.
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Affiliation(s)
- Xiaoyin Wang
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang, Henan, China.,Henan Collaborative Innovation Center of Molecular Diagnosis and Laboratory Medicine, Xinxiang, Henan, China
| | - Zhongjie Xu
- Life Science and Technology, Xinxiang Medical University, Xinxiang, Henan, China
| | - Zhengwei Tian
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang, Henan, China
| | - Xi Zhang
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang, Henan, China
| | - Danhua Xu
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang, Henan, China
| | - Qin Li
- Test Laboratory, Xinxiang Medical University, Xinxiang, Henan, China
| | - Junhe Zhang
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang, Henan, China
| | - Tianyun Wang
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang, Henan, China
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Impact of Different Promoters on Episomal Vectors Harbouring Characteristic Motifs of Matrix Attachment Regions. Sci Rep 2016; 6:26446. [PMID: 27226236 PMCID: PMC4881036 DOI: 10.1038/srep26446] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Accepted: 04/29/2016] [Indexed: 12/19/2022] Open
Abstract
We previously demonstrated that the characteristic sequence of matrix attachment regions (MARs) allows transgenes to be maintained episomally in CHO cells. In the present study, six commonly used promoters from human cytomegalovirus major immediate-early (CMV), simian vacuolating virus 40 (SV40), Rous sarcoma virus, Homo sapiens ubiquitin C, phosphoglycerate kinase, and β-globin, respectively, were evaluated to determine their effects on transgene expression and stability in CHO cells stably transfected via the episomal vector harbouring characteristic MAR motifs. The CHO cells were transfected with vectors and then screened using G418, after which the stably transfected cells were split into two and further cultured either in the presence or absence of G418. Of the six promoters, the CMV promoter yielded the highest transgene expression levels and the highest transfection efficiency, whereas the SV40 promoter maintained transgene expression more stably during long-term culture than the other promoters did. The CMV and SV40 promoter-containing vectors were furthermore episomally maintained and conferred sustained eGFP expression in the cells even under nonselective conditions. On the basis of these findings, we conclude that the CMV promoter performs best in terms of yielding both high expression levels and high levels of stability using this episomal vector system.
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Wang XJ, Wang J, Wang YY, Guo YJ, Chu BB, Yang GY. Sus scrofa matrix attachment region enhances expression of the PiggyBac system transfected into HEK293T cells. Biotechnol Lett 2016; 38:949-58. [PMID: 26965151 DOI: 10.1007/s10529-016-2074-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 03/01/2016] [Indexed: 10/22/2022]
Abstract
OBJECTIVES To determine the effects of the Sus scrofa matrix attachment region (SusMAR) on transgene expression in HEK293T cells. RESULTS Three expression vectors with the MAR at different sites in the PiggyBac (PB) transposon vector backbone were compared: two MARs flanking the β-galactosidase (β-gal) expression cassette, and one at the upstream or downstream site. Bos taurus MAR (BosMAR) and a β-gal expression cassette without MARs were the positive and negative controls, respectively. Compared to the control, β-gal activity of all SusMAR and BosMAR vectors was significantly improved in the presence of PB transposase (PBase). However, only the downstream SusMAR and upstream BosMAR vectors showed increased expression in the absence of PBase. Expression was significantly increased in all vectors with the PBase group compared to those without the PBase group. Gene copy numbers were not increased compared to the negative control. CONCLUSIONS SusMAR enhanced recombinant gene expression levels and stability in HEK293T cells, was not increase transgene copy number. These results could facilitate the development of vectors for stable production of therapeutic proteins.
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Affiliation(s)
- Xin-Jian Wang
- Key Laboratory of Animal Biochemistry and Nutrition, Ministry of Agriculture, Henan Agricultural University, Zhengzhou, Henan, China
| | - Jiang Wang
- Key Laboratory of Animal Biochemistry and Nutrition, Ministry of Agriculture, Henan Agricultural University, Zhengzhou, Henan, China
| | - Yue-Ying Wang
- Key Laboratory of Animal Biochemistry and Nutrition, Ministry of Agriculture, Henan Agricultural University, Zhengzhou, Henan, China
| | - Yu-Jie Guo
- Key Laboratory of Animal Biochemistry and Nutrition, Ministry of Agriculture, Henan Agricultural University, Zhengzhou, Henan, China
| | - Bei-Bei Chu
- Key Laboratory of Animal Biochemistry and Nutrition, Ministry of Agriculture, Henan Agricultural University, Zhengzhou, Henan, China
| | - Guo-Yu Yang
- College of Animal Husbandary and Veterinary Science, Henan Agricultural University, Wenhua Road 95, Zhengzhou, 450002, People's Republic of China.
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