1
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Li Q, Yan RF, Yang YX, Mi CL, Jia YL, Wang TY. Stabilizing and Anti-Repressor Elements Effectively Increases Transgene Expression in Transfected CHO Cells. Front Bioeng Biotechnol 2022; 10:840600. [PMID: 35721852 PMCID: PMC9199445 DOI: 10.3389/fbioe.2022.840600] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Accepted: 04/21/2022] [Indexed: 11/13/2022] Open
Abstract
Chinese hamster ovary (CHO) cells are currently the most widely used host cells for recombinant therapeutic protein (RTP) production. Currently, the RTP yields need to increase further to meet the market needs and reduce costs. In this study, three stabilizing and anti-repressor (SAR) elements from the human genome were selected, including human SAR7, SAR40, and SAR44 elements. SAR elements were cloned upstream of the promoter in the eukaryotic vector, followed by transfection into CHO cells, and were screened under G418 pressure. Flow cytometry was used to detect enhanced green fluorescent protein (eGFP) expression levels. The gene copy numbers and mRNA expression levels were determined through quantitative real-time PCR. Furthermore, the effect of the stronger SAR elements on adalimumab was investigated. The results showed that transgene expression levels in the SAR-containing vectors were higher than that of the control vector, and SAR7 and SAR40 significantly increased and maintained the long-term expression of the transgene in CHO cells. In addition, the transgene expression level increase was related with gene copy numbers and mRNA expression levels. Collectively, SAR elements can enhance the transgene expression and maintain the long-term expression of a transgene in transfected CHO cells, which may be used to increase recombinant protein production in CHO cells.
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Affiliation(s)
- Qin Li
- School of Basic Medicine, Xinxiang Medical University, Xinxiang, China.,International Joint Research Laboratory for Recombinant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang, China
| | - Rui-Fang Yan
- School of Basic Medicine, Xinxiang Medical University, Xinxiang, China
| | - Yong-Xiao Yang
- International Joint Research Laboratory for Recombinant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang, China
| | - Chun-Liu Mi
- School of Basic Medicine, Xinxiang Medical University, Xinxiang, China.,International Joint Research Laboratory for Recombinant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang, China
| | - Yan-Long Jia
- International Joint Research Laboratory for Recombinant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang, China
| | - Tian-Yun Wang
- School of Basic Medicine, 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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Screening of CHO-K1 endogenous promoters for expressing recombinant proteins in mammalian cell cultures. Plasmid 2022; 119-120:102620. [DOI: 10.1016/j.plasmid.2022.102620] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Revised: 01/28/2022] [Accepted: 02/01/2022] [Indexed: 12/28/2022]
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3
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Marx N, Dhiman H, Schmieder V, Freire CM, Nguyen LN, Klanert G, Borth N. Enhanced targeted DNA methylation of the CMV and endogenous promoters with dCas9-DNMT3A3L entails distinct subsequent histone modification changes in CHO cells. Metab Eng 2021; 66:268-282. [PMID: 33965614 DOI: 10.1016/j.ymben.2021.04.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 04/02/2021] [Accepted: 04/22/2021] [Indexed: 01/08/2023]
Abstract
With the emergence of new CRISPR/dCas9 tools that enable site specific modulation of DNA methylation and histone modifications, more detailed investigations of the contribution of epigenetic regulation to the precise phenotype of cells in culture, including recombinant production subclones, is now possible. These also allow a wide range of applications in metabolic engineering once the impact of such epigenetic modifications on the chromatin state is available. In this study, enhanced DNA methylation tools were targeted to a recombinant viral promoter (CMV), an endogenous promoter that is silenced in its native state in CHO cells, but had been reactivated previously (β-galactoside α-2,6-sialyltransferase 1) and an active endogenous promoter (α-1,6-fucosyltransferase), respectively. Comparative ChIP-analysis of histone modifications revealed a general loss of active promoter histone marks and the acquisition of distinct repressive heterochromatin marks after targeted methylation. On the other hand, targeted demethylation resulted in autologous acquisition of active promoter histone marks and loss of repressive heterochromatin marks. These data suggest that DNA methylation directs the removal or deposition of specific histone marks associated with either active, poised or silenced chromatin. Moreover, we show that de novo methylation of the CMV promoter results in reduced transgene expression in CHO cells. Although targeted DNA methylation is not efficient, the transgene is repressed, thus offering an explanation for seemingly conflicting reports about the source of CMV promoter instability in CHO cells. Importantly, modulation of epigenetic marks enables to nudge the cell into a specific gene expression pattern or phenotype, which is stabilized in the cell by autologous addition of further epigenetic marks. Such engineering strategies have the added advantage of being reversible and potentially tunable to not only turn on or off a targeted gene, but also to achieve the setting of a desirable expression level.
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Affiliation(s)
- Nicolas Marx
- BOKU University of Natural Resources and Life Sciences, Vienna, Austria; Austrian Center for Industrial Biotechnology GmbH, Vienna, Austria
| | - Heena Dhiman
- BOKU University of Natural Resources and Life Sciences, Vienna, Austria; Austrian Center for Industrial Biotechnology GmbH, Vienna, Austria
| | - Valerie Schmieder
- BOKU University of Natural Resources and Life Sciences, Vienna, Austria; Austrian Center for Industrial Biotechnology GmbH, Vienna, Austria
| | | | - Ly Ngoc Nguyen
- BOKU University of Natural Resources and Life Sciences, Vienna, Austria; Austrian Center for Industrial Biotechnology GmbH, Vienna, Austria
| | - Gerald Klanert
- Austrian Center for Industrial Biotechnology GmbH, Vienna, Austria
| | - Nicole Borth
- BOKU University of Natural Resources and Life Sciences, Vienna, Austria; Austrian Center for Industrial Biotechnology GmbH, Vienna, Austria.
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4
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McGraw CE, Peng D, Sandoval NR. Synthetic biology approaches: the next tools for improved protein production from CHO cells. Curr Opin Chem Eng 2020. [DOI: 10.1016/j.coche.2020.06.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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5
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Wang TY, Guo X. Expression vector cassette engineering for recombinant therapeutic production in mammalian cell systems. Appl Microbiol Biotechnol 2020; 104:5673-5688. [PMID: 32372203 DOI: 10.1007/s00253-020-10640-w] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 04/13/2020] [Accepted: 04/20/2020] [Indexed: 12/16/2022]
Abstract
Human tissue plasminogen activator was the first recombinant therapy protein that successfully produced in Chinese hamster ovary cells in 1986 and approved for clinical use. Since then, more and more therapeutic proteins are being manufactured in mammalian cells, and the technologies for recombinant protein production in this expression system have developed rapidly, with the optimization of both upstream and downstream processes. One of the most promising strategies is expression vector cassette optimization based on the expression vector cassette. In this review paper, these approaches and developments are summarized, and the future strategy on the utilizing of expression cassettes for the production of recombinant therapeutic proteins in mammalian cells is discussed.
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Affiliation(s)
- Tian-Yun Wang
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, Xinxiang, 453003, Henan, China.
- International Joint Research Laboratory for Recombinant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang, 453003, Henan, China.
| | - Xiao Guo
- International Joint Research Laboratory for Recombinant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang, 453003, Henan, China
- Perildicals Publishing House, Xinxiang Medical University, Xinxiang, Henan, China
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6
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Zhang JH, Zhang JH, Wang XY, Xu DH, Wang TY. Distance effect characteristic of the matrix attachment region increases recombinant protein expression in Chinese hamster ovary cells. Biotechnol Lett 2019; 42:187-196. [PMID: 31776751 DOI: 10.1007/s10529-019-02775-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Accepted: 11/24/2019] [Indexed: 12/21/2022]
Abstract
OBJECTIVES Previously, we have found that the matrix attachment region (MAR) may confer a 'distance effect' on transgene expression. This work aims to systematically explore the increased transgene expression in transfected Chinese hamster ovary (CHO) cells due to the characteristics of MAR and its mechanism. RESULTS Compared with the control vector, 500 and 1000 bp DNA distances between MAR and the cytomegalovirus promoter can increase transgene expression by 1.77- and 1.56-fold, respectively. Meanwhile, transgene expression was not affected when 2000 and 2500 bp spacer DNAs were inserted, but a declining trend was observed when a 1500 bp spacer DNA was inserted. The vector containing a 500 bp DNA distance significantly increased the expression of the enhanced green fluorescent protein, and this increase was not related to transgene copy numbers. CONCLUSIONS A short DNA distance-containing MAR confers high transgene expression level in transfected CHO cells, but a distance threshold does not exist in the vector system.
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Affiliation(s)
- Jun-He Zhang
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, No. 601 Jinsui Road, Xinxiang, 453003, Henan, China.,International Joint Research Laboratory for Recombinant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang, Henan, China
| | - Ji-Hong Zhang
- Department of Histology and Embryology, Xinxiang Medical University, Xinxiang, Henan, China
| | - Xiao-Yin Wang
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, No. 601 Jinsui Road, Xinxiang, 453003, Henan, China.,International Joint Research Laboratory for Recombinant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang, Henan, China
| | - Dan-Hua Xu
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, No. 601 Jinsui Road, Xinxiang, 453003, Henan, China.,International Joint Research Laboratory for Recombinant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang, Henan, China
| | - Tian-Yun Wang
- Department of Biochemistry and Molecular Biology, Xinxiang Medical University, No. 601 Jinsui Road, Xinxiang, 453003, Henan, China. .,International Joint Research Laboratory for Recombinant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang, Henan, China.
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7
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Jia YL, Guo X, Ni TJ, Lu JT, Wang XY, Wang TY. Novel short synthetic matrix attachment region for enhancing transgenic expression in recombinant Chinese hamster ovary cells. J Cell Biochem 2019; 120:18478-18486. [PMID: 31168866 DOI: 10.1002/jcb.29165] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Revised: 05/18/2019] [Accepted: 05/23/2019] [Indexed: 01/17/2023]
Abstract
Matrix attachment regions (MARs) are DNA fragments with specific motifs that enhance transgenic expression; however, the characteristics and functions of these elements remain unclear. In this study, we designed and synthesized three short chimeric MARs, namely, SM4, SM5, and SM6, with different numbers and orders of motifs on the basis of the features and motifs of previously reported MARs, namely, SM1, SM2, and SM3, respectively. Expression vectors with six synthetic MARs flanking the down or upstream of the expression cassette for enhanced green fluorescence protein (EGFP) were constructed and introduced into Chinese hamster ovary (CHO) cells. Results indicated that the EGFP expression of the CHO cells with transfection bySM4, SM5, or SM6-containing vectors was higher than that of those containing SM1, SM2, or SM3 regardless of the MAR insertion position. The improving effect of SM5 was particularly pronounced. Transgenic expression was further enhanced with the increasing SM5 copy number. Bioinformatics analysis indicated that several arrangements of the DNA-binding motifs for CEBP, FAST, Hox, glutathione, and NMP4 may help increase transgenic expression levels and the average population of highly expressed cells. Our findings on novel synthetic MARs will help establish stable expression systems in mammalian cells.
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Affiliation(s)
- Yan-Long Jia
- School of Pharmacy, Xinxiang Medical University, Xinxiang, Henan, China.,International Joint Research Laboratory for Recombiant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang, Henan, China
| | - Xiao Guo
- School of Pharmacy, Xinxiang Medical University, Xinxiang, Henan, China.,International Joint Research Laboratory for Recombiant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang, Henan, China
| | - Tian-Jun Ni
- School of Basic Medicine, Xinxiang Medical University, Xinxiang, Henan, China
| | - Jiang-Tao Lu
- School of Pharmacy, Xinxiang Medical University, Xinxiang, Henan, China.,International Joint Research Laboratory for Recombiant Pharmaceutical Protein Expression System of Henan, 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.,School of Basic Medicine, Xinxiang Medical University, Xinxiang, Henan, China
| | - Tian-Yun Wang
- International Joint Research Laboratory for Recombiant Pharmaceutical Protein Expression System of Henan, Xinxiang Medical University, Xinxiang, Henan, China.,School of Basic Medicine, Xinxiang Medical University, Xinxiang, Henan, China
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8
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Johari YB, Brown AJ, Alves CS, Zhou Y, Wright CM, Estes SD, Kshirsagar R, James DC. CHO genome mining for synthetic promoter design. J Biotechnol 2019; 294:1-13. [PMID: 30703471 DOI: 10.1016/j.jbiotec.2019.01.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Revised: 01/07/2019] [Accepted: 01/09/2019] [Indexed: 01/01/2023]
Abstract
Synthetic promoters are an attractive alternative for use in mammalian hosts such as CHO cells as they can be designed de novo with user-defined functionalities. In this study, we describe and validate a method for bioprocess-directed design of synthetic promoters utilizing CHO genomic sequence information. We designed promoters with two objective features, (i) constitutive high-level recombinant gene transcription, and (ii) upregulated transcription under mild hypothermia or late-stage culture. CHO genes varying in transcriptional activity were selected based on a comparative analysis of RNA-Seq transcript levels in normal and biphasic cultures in combination with estimates of mRNA half-life from published genome scale datasets. Discrete transcription factor regulatory elements (TFREs) upstream of these genes were informatically identified and functionally screened in vitro to identify a subset of TFREs with the potential to support high activity recombinant gene transcription during biphasic cell culture processes. Two libraries of heterotypic synthetic promoters with varying TFRE combinations were then designed in silico that exhibited a maximal 2.5-fold increase in transcriptional strength over the CMV-IE promoter after transient transfection into host CHO-K1 cells. A subset of synthetic promoters was then used to create stable transfectant pools using CHO-K1 cells under glutamine synthetase selection. Whilst not achieving the maximal 2.5-fold increase in productivity over stable pools harboring the CMV promoter, all stably transfected cells utilizing synthetic promoters exhibited increased reporter production - up to 1.6-fold that of cells employing CMV, both in the presence or absence of intron A immediately downstream of the promoter. The increased productivity of stably transfected cells harboring synthetic promoters was maintained during fed-batch culture, with or without a transition to mild hypothermia at the onset of stationary phase. Our data exemplify that it is important to consider both host cell and intended bioprocess contexts as design criteria in the de novo construction of synthetic genetic parts for mammalian cell engineering.
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Affiliation(s)
- Yusuf B Johari
- Department of Chemical and Biological Engineering, University of Sheffield, Mappin St., Sheffield S1 3JD, UK
| | - Adam J Brown
- Department of Chemical and Biological Engineering, University of Sheffield, Mappin St., Sheffield S1 3JD, UK
| | | | - Yizhou Zhou
- Cell Culture Development, Biogen Inc., Cambridge, MA 02142, USA
| | | | - Scott D Estes
- Cell Culture Development, Biogen Inc., Cambridge, MA 02142, USA
| | | | - David C James
- Department of Chemical and Biological Engineering, University of Sheffield, Mappin St., Sheffield S1 3JD, UK.
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9
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Mahameed M, Obiedat A, Beck G, Johnson JC, Tirosh B. Low concentrations of cadmium chloride promotes protein translation and improve cell line productivity. Biotechnol Bioeng 2019; 116:569-580. [DOI: 10.1002/bit.26888] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Revised: 11/15/2018] [Accepted: 11/29/2018] [Indexed: 01/06/2023]
Affiliation(s)
- Mohamed Mahameed
- Institute for Drug ResearchThe School of PharmacyThe Hebrew University of JerusalemJerusalem Israel
| | - Akram Obiedat
- Institute for Drug ResearchThe School of PharmacyThe Hebrew University of JerusalemJerusalem Israel
| | - Gad Beck
- Molecular Biology and Fermentation Unit, Valin TechnologiesYavne Israel
| | | | - Boaz Tirosh
- Institute for Drug ResearchThe School of PharmacyThe Hebrew University of JerusalemJerusalem Israel
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10
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Jia Y, Guo X, Lu J, Wang X, Qiu L, Wang T. CRISPR/Cas9-mediated gene knockout for DNA methyltransferase Dnmt3a in CHO cells displays enhanced transgenic expression and long-term stability. J Cell Mol Med 2018; 22:4106-4116. [PMID: 29851281 PMCID: PMC6111867 DOI: 10.1111/jcmm.13687] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Accepted: 04/23/2018] [Indexed: 12/14/2022] Open
Abstract
CHO cells are the preferred host for the production of complex pharmaceutical proteins in the biopharmaceutical industry, and genome engineering of CHO cells would benefit product yield and stability. Here, we demonstrated the efficacy of a Dnmt3a-deficient CHO cell line created by CRISPR/Cas9 genome editing technology through gene disruptions in Dnmt3a, which encode the proteins involved in DNA methyltransferases. The transgenes, which were driven by the 2 commonly used CMV and EF1α promoters, were evaluated for their expression level and stability. The methylation levels of CpG sites in the promoter regions and the global DNA were compared in the transfected cells. The Dnmt3a-deficent CHO cell line based on Dnmt3a KO displayed an enhanced long-term stability of transgene expression under the control of the CMV promoter in transfected cells in over 60 passages. Under the CMV promoter, the Dnmt3a-deficent cell line with a high transgene expression displayed a low methylation rate in the promoter region and global DNA. Under the EF1α promoter, the Dnmt3a-deficient and normal cell lines with low transgene expression exhibited high DNA methylation rates. These findings provide insight into cell line modification and design for improved recombinant protein production in CHO and other mammalian cells.
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Affiliation(s)
- Yan‐Long Jia
- College of PharmacyXinxiang Medical UniversityXinxiangHenanChina
- International Joint Research Laboratory for Recombiant Pharmaceutical Protein Expression System of HenanXinxiang Medical UniversityXinxiangHenanChina
| | - Xiao Guo
- College of PharmacyXinxiang Medical UniversityXinxiangHenanChina
- International Joint Research Laboratory for Recombiant Pharmaceutical Protein Expression System of HenanXinxiang Medical UniversityXinxiangHenanChina
| | - Jiang‐Tao Lu
- College of PharmacyXinxiang Medical UniversityXinxiangHenanChina
- International Joint Research Laboratory for Recombiant Pharmaceutical Protein Expression System of HenanXinxiang Medical UniversityXinxiangHenanChina
| | - Xiao‐Yin Wang
- International Joint Research Laboratory for Recombiant Pharmaceutical Protein Expression System of HenanXinxiang Medical UniversityXinxiangHenanChina
- School of Basic MedicineXinxiang Medical UniversityXinxiangHenanChina
| | - Le‐Le Qiu
- School of Basic MedicineXinxiang Medical UniversityXinxiangHenanChina
| | - Tian‐Yun Wang
- International Joint Research Laboratory for Recombiant Pharmaceutical Protein Expression System of HenanXinxiang Medical UniversityXinxiangHenanChina
- School of Basic MedicineXinxiang Medical UniversityXinxiangHenanChina
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11
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Tomioka I, Nogami N, Nakatani T, Owari K, Fujita N, Motohashi H, Takayama O, Takae K, Nagai Y, Seki K. Generation of transgenic marmosets using a tetracyclin-inducible transgene expression system as a neurodegenerative disease model. Biol Reprod 2018; 97:772-780. [PMID: 29045563 DOI: 10.1093/biolre/iox129] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Accepted: 10/12/2017] [Indexed: 01/18/2023] Open
Abstract
Controllable transgene expression systems are indispensable tools for the production of animal models of disease to investigate protein functions at defined periods. However, in nonhuman primates that share genetic, physiological, and morphological similarities with humans, genetic modification techniques have not been well established; therefore, the establishment of novel transgenic models with controllable transgene expression systems will be valuable tools to understand pathological mechanism of human disease. In the present study, we successfully generated transgenic marmosets using a tetracyclin-inducible transgene expression (tet-on) system as a neurodegenerative disease model. The mutant human ataxin 3 gene controlled by the tet-on system was introduced into marmoset embryos via lentiviral transduction, and 34 transgene-introduced embryos were transferred into the uteri of surrogate mothers. Seven live offspring (TET1-7) were obtained, of which four were transgenic. Fibroblasts from TET1 and 3 revealed that inducible transgene expression had occurred after treatment with 10 μg/mL of doxycycline, while treatment with doxycycline via drinking water resulted in 1.7- to 1.8-fold inducible transgene expression compared with before treatment. One transgenic second-generation offspring (TET3-3) was obtained from TET3, and doxycycline-inducible transgene expression in its fibroblasts showed that TET3-3 maintained a high transgene expression level that matched its parent. In conclusion, we established a novel transgenic marmoset line carrying the mutant human ataxin 3 gene controlled by the tet-on system. The development of nonhuman primate models with controllable transgene expression systems will be useful for the identification of disease biomarkers and evaluation of the efficacy and metabolic profiles of therapeutic candidates.
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Affiliation(s)
- Ikuo Tomioka
- Department of Neurophysiology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan.,Institute for Biomedical Science, Shinshu University, Nagano, Japan
| | - Naotake Nogami
- Department of Neurophysiology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Terumi Nakatani
- Department of Neurophysiology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Kensuke Owari
- Department of Neurophysiology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Naoko Fujita
- Department of Neurophysiology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Hideyuki Motohashi
- Department of Neurophysiology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Osamu Takayama
- Department of Neurophysiology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Kentaro Takae
- Institute for Biomedical Science, Shinshu University, Nagano, Japan
| | - Yoshitaka Nagai
- Department of Degenerative Neurological Diseases, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan.,Department of Neurotherapeutics, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Kazuhiko Seki
- Department of Neurophysiology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan
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12
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Patel NA, Anderson CR, Terkildsen SE, Davis RC, Pack LD, Bhargava S, Clarke HR. Antibody expression stability in CHO clonally derived cell lines and their subclones: Role of methylation in phenotypic and epigenetic heterogeneity. Biotechnol Prog 2018; 34:635-649. [DOI: 10.1002/btpr.2655] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 04/24/2018] [Indexed: 11/11/2022]
Affiliation(s)
- Neha A. Patel
- Dept. of Bioprocess Development; Seattle Genetics; Bothell WA 98021
| | | | | | - Ray C. Davis
- Dept. of Bioprocess Development; Seattle Genetics; Bothell WA 98021
| | - Laura D. Pack
- Dept. of CMC Statistics; Seattle Genetics; Bothell WA 98021
| | - Swapnil Bhargava
- Dept. of Bioprocess Development; Seattle Genetics; Bothell WA 98021
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13
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Jazayeri SH, Amiri-Yekta A, Bahrami S, Gourabi H, Sanati MH, Khorramizadeh MR. Vector and Cell Line Engineering Technologies Toward Recombinant Protein Expression in Mammalian Cell Lines. Appl Biochem Biotechnol 2018; 185:986-1003. [PMID: 29396733 DOI: 10.1007/s12010-017-2689-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Accepted: 12/29/2017] [Indexed: 11/26/2022]
Abstract
The rapid growth of global biopharmaceutical market in the recent years has been a good indication of its significance in biotechnology industry. During a long period of time in recombinant protein production from 1980s, optimizations in both upstream and downstream processes were launched. In this regard, one of the most promising strategies is expression vector engineering technology based on incorporation of DNA opening elements found in the chromatin border regions of vectors as well as targeting gene integration. Along with these approaches, cell line engineering has revealed convenient outcomes in isolating high-producing clones. According to the fact that more than 50% of the approved therapeutic proteins is being manufactured in mammalian cell lines, in this review, we focus on several approaches and developments in vector and cell line engineering technologies in mammalian cell culture.
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Affiliation(s)
- Seyedeh Hoda Jazayeri
- Department of Medical Biotechnology, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran, Iran
- Department of Genetics, Reproductive Biomedicine Research Center, ACECR, Royan Institute for Reproductive Biomedicine, P.O. Box: 14155-6343, Tehran, Iran
| | - Amir Amiri-Yekta
- Department of Genetics, Reproductive Biomedicine Research Center, ACECR, Royan Institute for Reproductive Biomedicine, P.O. Box: 14155-6343, Tehran, Iran
| | - Salahadin Bahrami
- Department of Genetics, Reproductive Biomedicine Research Center, ACECR, Royan Institute for Reproductive Biomedicine, P.O. Box: 14155-6343, Tehran, Iran
| | - Hamid Gourabi
- Department of Genetics, Reproductive Biomedicine Research Center, ACECR, Royan Institute for Reproductive Biomedicine, P.O. Box: 14155-6343, Tehran, Iran
| | - Mohammad Hossein Sanati
- Department of Genetics, Reproductive Biomedicine Research Center, ACECR, Royan Institute for Reproductive Biomedicine, P.O. Box: 14155-6343, Tehran, Iran.
- Department of Medical Genetics, National Institute of Genetic Engineering and Biotechnology, Tehran, Iran.
| | - Mohammad Reza Khorramizadeh
- Biosensor Research Center, Endocrinology and Metabolism Molecular-Cellular Sciences Institute, Tehran University of Medical Sciences, P.O. Box: 1411413137, Tehran, Iran.
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14
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An IRES-Mediated Tricistronic Vector for Efficient Generation of Stable, High-Level Monoclonal Antibody Producing CHO DG44 Cell Lines. Methods Mol Biol 2018; 1827:335-349. [PMID: 30196505 DOI: 10.1007/978-1-4939-8648-4_17] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The generation of stable, high-level monoclonal antibody (mAb) producing cell lines remains a major challenge in biopharmaceutical industry. The commonly used plasmid vectors for mAb expression, which express light chain (LC), heavy chain (HC), and selection marker genes on separate vectors or via multiple promoters on a single vector, are not able to accurately control the ratio of LC over HC expression and tend to result in non-expressing clones. To overcome these issues, we have developed a tricistronic vector using two internal ribosome entry sites (IRES) to express the LC, HC, and dihydrofolate reductase (DHFR) selection marker genes in one transcript. In this tricistronic vector, the three genes are under the control of a hapten-modified human cytomegalovirus (hCMV) promoter containing a core CpG island element (IE) to enhance the production stability. The LC gene is arranged as the first cistron followed by a wild-type IRES to control the HC expression. Such design expresses excess LC polypeptides which enhance mAb expression level and reduce aggregate. A mutated IRES with attenuated strength is applied on DHFR to reduce its expression for enhancing the stringency of selection for high producers. This vector allows easy generation of stable, high mAb producing CHO DG44 pools and clones for antibody development and manufacturing.
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15
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Wang D, Dai W, Wu J, Wang J. Improving transcriptional activity of human cytomegalovirus major immediate-early promoter by mutating NF-κB binding sites. Protein Expr Purif 2017; 142:16-24. [PMID: 28941824 DOI: 10.1016/j.pep.2017.09.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Revised: 09/12/2017] [Accepted: 09/18/2017] [Indexed: 01/11/2023]
Abstract
Many mammalian gene expression vectors express the transferred genes under the control of the cytomegalovirus (CMV) major immediate-early promoter (MIEP). The human MIEP has been known as the strongest promoter in mammalian cells and utilized widely in mammalian expression systems. There are four NF-κB binding sites (named as κBs) in the human MIEP. In this study, we have constructed multiple mutated MIEPs by changing the natural κBs in the human MIEP into the high-affinity artificial sequences that were in vitro selected by using systematic evolution of ligands by exponential enrichment (SELEX) and predicted by bioinformatics. With various transcriptional activity evaluations, we found three mutated MIEPs with the transcriptional activity higher than the wild-type MIEP, which should be useful and widely applicable in many mammalian transgene expression fields such as gene engineering, gene therapy and gene editing. This study provides a useful approach for promoter engineering in biotechnology. This study also produced a series of mutated MIEPs with various transcriptional activities, which may be used for the fine control of gene expression output in the future synthetic biology.
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Affiliation(s)
- Danyang Wang
- State Key Laboratory of Bioelectronics, Southeast University, Nanjing 210096, China
| | - Wei Dai
- State Key Laboratory of Bioelectronics, Southeast University, Nanjing 210096, China
| | - Jian Wu
- State Key Laboratory of Bioelectronics, Southeast University, Nanjing 210096, China
| | - Jinke Wang
- State Key Laboratory of Bioelectronics, Southeast University, Nanjing 210096, China.
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Brown AJ, Kalsi D, Fernandez-Martell A, Cartwright J, Barber NOW, Patel YD, Turner R, Bryant CL, Johari YB, James DC. Expression Systems for Recombinant Biopharmaceutical Production by Mammalian Cells in Culture. METHODS AND PRINCIPLES IN MEDICINAL CHEMISTRY 2017. [DOI: 10.1002/9783527699124.ch13] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Adam J. Brown
- University of Sheffield; Department of Chemical and Biological Engineering; Mappin St. Sheffield S1 3JD UK
| | - Devika Kalsi
- University of Sheffield; Department of Chemical and Biological Engineering; Mappin St. Sheffield S1 3JD UK
| | | | - Joe Cartwright
- University of Sheffield; Department of Chemical and Biological Engineering; Mappin St. Sheffield S1 3JD UK
| | - Nicholas O. W. Barber
- University of Sheffield; Department of Chemical and Biological Engineering; Mappin St. Sheffield S1 3JD UK
| | - Yash D. Patel
- University of Sheffield; Department of Chemical and Biological Engineering; Mappin St. Sheffield S1 3JD UK
| | | | - Claire L. Bryant
- University of Sheffield; Department of Chemical and Biological Engineering; Mappin St. Sheffield S1 3JD UK
| | - Yusuf B. Johari
- University of Sheffield; Department of Chemical and Biological Engineering; Mappin St. Sheffield S1 3JD UK
| | - David C. James
- University of Sheffield; Department of Chemical and Biological Engineering; Mappin St. Sheffield S1 3JD UK
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17
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Soo BPC, Tay J, Ng S, Ho SCL, Yang Y, Chao SH. Correlation Between Expression of Recombinant Proteins and Abundance of H3K4Me3 on the Enhancer of Human Cytomegalovirus Major Immediate-Early Promoter. Mol Biotechnol 2017; 59:315-322. [DOI: 10.1007/s12033-017-0019-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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18
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Rocha-Pizaña MDR, Ascencio-Favela G, Soto-García BM, Martinez-Fierro MDLL, Alvarez MM. Evaluation of changes in promoters, use of UCOES and chain order to improve the antibody production in CHO cells. Protein Expr Purif 2017; 132:108-115. [DOI: 10.1016/j.pep.2017.01.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2016] [Revised: 01/30/2017] [Accepted: 01/31/2017] [Indexed: 11/26/2022]
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19
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Cheng JK, Alper HS. Transcriptomics-Guided Design of Synthetic Promoters for a Mammalian System. ACS Synth Biol 2016; 5:1455-1465. [PMID: 27268512 DOI: 10.1021/acssynbio.6b00075] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Despite recent advances in improving titers for therapeutic proteins such as antibodies to the 10 g/L scale, these high yields can only be achieved in select mammalian hosts. Regardless of the host or product, strong promoters are required to obtain high levels of transgene expression. However, the promoters employed to drive this expression are rather limited in variety and are usually either viral-derived or screened empirically during vector design. To begin to move away from viral parts, we employed a more systematic approach to identify and design new synthetic promoters using endogenous elements. To do so, we established a workflow to design these elements by (1) analyzing the transcriptomics profile of a specific cell line under a desired, representative cell culture condition, (2) identifying key genetic motifs using bioinformatics that can be used to rationally construct synthetic promoters, (3) building synthetic promoters using conventional DNA synthesis and molecular biology techniques, and (4) evaluating the performance of these synthetic promoters using model proteins. The resulting promoters perform comparably to the hCMV IE promoter variants tested, but with endogenous components. During this design-build-test cycle we also investigated the underlying design rules for transcription factor binding site arrangement in synthetic promoters. Overall, this approach of using an "omics-guided" workflow for designing synthetic promoters facilitates the construction of high expression vectors for immediate use in current production hosts.
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Affiliation(s)
- Joseph K. Cheng
- Department
of Chemical Engineering, The University of Texas at Austin, 200
E Dean Keeton Street Stop C0400, Austin, Texas 78712, United States
| | - Hal S. Alper
- Department
of Chemical Engineering, The University of Texas at Austin, 200
E Dean Keeton Street Stop C0400, Austin, Texas 78712, United States
- Institute
for Cellular and Molecular Biology The University of Texas at Austin, 2500
Speedway Avenue, Austin, Texas 78712, United States
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20
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Ho SCL, Koh EYC, Soo BPC, Mariati, Chao SH, Yang Y. Evaluating the use of a CpG free promoter for long-term recombinant protein expression stability in Chinese hamster ovary cells. BMC Biotechnol 2016; 16:71. [PMID: 27756290 PMCID: PMC5070371 DOI: 10.1186/s12896-016-0300-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Accepted: 10/13/2016] [Indexed: 12/04/2022] Open
Abstract
Background Methylated CpG dinucleotides in promoters are associated with the loss of gene expression in recombinant Chinese hamster ovary (CHO) cells during large-scale commercial manufacturing. We evaluated a promoter devoid of CpG dinucleotides, CpGfree, in parallel with a similar CpG containing promoter, CpGrich, for their ability to maintain the expression of recombinant enhanced green fluorescent protein (EGFP) after 8 weeks of culturing. Results While the promoters gave similar transient expression levels, CpGfree clones had significantly higher average stable expression possibly due to increased resistance to early silencing during integration into the chromosome. A greater proportion of cells in clones generated using the CpGfree promoter were still expressing detectable levels of EGFP after 8 weeks but the relative expression levels measured at week 8 to those measured at week 0 did not improve compared to clones generated using the CpGrich promoter. Chromatin immunoprecipitation assays indicated that the repression of the CpGfree promoter was likely linked to histone deacetylation and methylation. Use of histone deacetylase inhibitors also managed to recover some of the lost expression. Conclusion Using a promoter without CpG dinucleotides could mitigate the early gene silencing but did not improve longer-term expression stability as silencing due to histone modifications could still take place. The results presented here would aid in promoter selection and design for improved protein production in CHO and other mammalian cells.
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Affiliation(s)
- Steven C L Ho
- Bioprocessing Technology Institute, Agency for Science, Technology and Research (A*STAR), 20 Biopolis Way, #06-01 Centros, Singapore, 138668, Singapore
| | - Esther Y C Koh
- Bioprocessing Technology Institute, Agency for Science, Technology and Research (A*STAR), 20 Biopolis Way, #06-01 Centros, Singapore, 138668, Singapore
| | - Benjamin P C Soo
- Bioprocessing Technology Institute, Agency for Science, Technology and Research (A*STAR), 20 Biopolis Way, #06-01 Centros, Singapore, 138668, Singapore
| | - Mariati
- Bioprocessing Technology Institute, Agency for Science, Technology and Research (A*STAR), 20 Biopolis Way, #06-01 Centros, Singapore, 138668, Singapore
| | - Sheng-Hao Chao
- Bioprocessing Technology Institute, Agency for Science, Technology and Research (A*STAR), 20 Biopolis Way, #06-01 Centros, Singapore, 138668, Singapore.,Department of Microbiology, National University of Singapore, Block MD4, 5 Science Drive 2, Singapore, 117597, Singapore
| | - Yuansheng Yang
- Bioprocessing Technology Institute, Agency for Science, Technology and Research (A*STAR), 20 Biopolis Way, #06-01 Centros, Singapore, 138668, Singapore.
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21
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Ritter A, Rauschert T, Oertli M, Piehlmaier D, Mantas P, Kuntzelmann G, Lageyre N, Brannetti B, Voedisch B, Geisse S, Jostock T, Laux H. Disruption of the gene C12orf35
leads to increased productivities in recombinant CHO cell lines. Biotechnol Bioeng 2016; 113:2433-42. [DOI: 10.1002/bit.26009] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Revised: 04/08/2016] [Accepted: 05/09/2016] [Indexed: 12/27/2022]
Affiliation(s)
- Anett Ritter
- Novartis Institutes for BioMedical Research; Basel Switzerland
- Novartis Pharma AG; Integrated Biologics Profiling Unit, Werk Klybeck Postfach CH-4002; Basel Switzerland
| | | | - Mevion Oertli
- Novartis Institutes for BioMedical Research; Basel Switzerland
- Novartis Pharma AG; Integrated Biologics Profiling Unit, Werk Klybeck Postfach CH-4002; Basel Switzerland
| | - Daniel Piehlmaier
- Novartis Pharma AG; Integrated Biologics Profiling Unit, Werk Klybeck Postfach CH-4002; Basel Switzerland
| | - Panagiotis Mantas
- Novartis Pharma AG; Integrated Biologics Profiling Unit, Werk Klybeck Postfach CH-4002; Basel Switzerland
| | | | - Nadine Lageyre
- Novartis Institutes for BioMedical Research; Basel Switzerland
| | | | - Bernd Voedisch
- Novartis Institutes for BioMedical Research; Basel Switzerland
| | - Sabine Geisse
- Novartis Institutes for BioMedical Research; Basel Switzerland
| | - Thomas Jostock
- Novartis Pharma AG; Integrated Biologics Profiling Unit, Werk Klybeck Postfach CH-4002; Basel Switzerland
| | - Holger Laux
- Novartis Pharma AG; Integrated Biologics Profiling Unit, Werk Klybeck Postfach CH-4002; Basel Switzerland
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22
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Brown AJ, James DC. Precision control of recombinant gene transcription for CHO cell synthetic biology. Biotechnol Adv 2015; 34:492-503. [PMID: 26721629 DOI: 10.1016/j.biotechadv.2015.12.012] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Revised: 12/11/2015] [Accepted: 12/22/2015] [Indexed: 11/30/2022]
Abstract
The next generation of mammalian cell factories for biopharmaceutical production will be genetically engineered to possess both generic and product-specific manufacturing capabilities that may not exist naturally. Introduction of entirely new combinations of synthetic functions (e.g. novel metabolic or stress-response pathways), and retro-engineering of existing functional cell modules will drive disruptive change in cellular manufacturing performance. However, before we can apply the core concepts underpinning synthetic biology (design, build, test) to CHO cell engineering we must first develop practical and robust enabling technologies. Fundamentally, we will require the ability to precisely control the relative stoichiometry of numerous functional components we simultaneously introduce into the host cell factory. In this review we discuss how this can be achieved by design of engineered promoters that enable concerted control of recombinant gene transcription. We describe the specific mechanisms of transcriptional regulation that affect promoter function during bioproduction processes, and detail the highly-specific promoter design criteria that are required in the context of CHO cell engineering. The relative applicability of diverse promoter development strategies are discussed, including re-engineering of natural sequences, design of synthetic transcription factor-based systems, and construction of synthetic promoters. This review highlights the potential of promoter engineering to achieve precision transcriptional control for CHO cell synthetic biology.
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Affiliation(s)
- Adam J Brown
- Department of Chemical and Biological Engineering, University of Sheffield, Sheffield S1 3JD, England, United Kingdom
| | - David C James
- Department of Chemical and Biological Engineering, University of Sheffield, Sheffield S1 3JD, England, United Kingdom.
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23
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Moritz B, Becker PB, Göpfert U. CMV promoter mutants with a reduced propensity to productivity loss in CHO cells. Sci Rep 2015; 5:16952. [PMID: 26581326 PMCID: PMC4652263 DOI: 10.1038/srep16952] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Accepted: 10/22/2015] [Indexed: 11/09/2022] Open
Abstract
The major immediate-early promoter and enhancer of the human cytomegalovirus (hCMV-MIE) is one of the most potent DNA elements driving recombinant gene expression in mammalian cells. Therefore, it is widely employed not only in research but also in large-scale industrial applications, e.g. for the production of therapeutic antibodies in Chinese hamster ovary cells (CHO). As we have reported previously, multi-site methylation of hCMV-MIE is linked to productivity loss in permanently transfected CHO cells lines. In particular, the cytosine located 179 bp upstream of the transcription start site (C-179) is frequently methylated. Therefore, our objective was to study whether mutation of C-179 and other cytosines within hCMV-MIE might lessen the instability of transgene expression. We discovered that the single mutation of C-179 to G can significantly stabilise the production of recombinant protein under control of hCMV-MIE in permanently transfected CHO cells.
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Affiliation(s)
- Benjamin Moritz
- Roche Pharmaceutical Research and Early Development, Large Molecule Research, Roche Innovation Center Penzberg, Germany
| | - Peter B Becker
- Biomedical Center and Center for Integrated Protein Science Munich, Ludwig Maximilian University, Munich, Germany
| | - Ulrich Göpfert
- Roche Pharmaceutical Research and Early Development, Large Molecule Research, Roche Innovation Center Penzberg, Germany
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24
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Mariati, Koh EYC, Yeo JHM, Ho SCL, Yang Y. Toward stable gene expression in CHO cells. Bioengineered 2015; 5:340-5. [PMID: 25482237 DOI: 10.4161/bioe.32111] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Maintaining high gene expression level during long-term culture is critical when producing therapeutic recombinant proteins using mammalian cells. Transcriptional silencing of promoters, most likely due to epigenetic events such as DNA methylation and histone modifications, is one of the major mechanisms causing production instability. Previous studies demonstrated that the core CpG island element (IE) from the hamster adenine phosphoribosyltransferase gene is effective to prevent DNA methylation. We generated one set of modified human cytomegalovirus (hCMV) promoters by insertion of one or two copies of IE in either forward or reverse orientations into different locations of the hCMV promoter. The modified hCMV with one copy of IE inserted between the hCMV enhancer and core promoter in reverse orientation (MR1) was most effective at enhancing expression stability in CHO cells without comprising expression level when compared with the wild type hCMV. We also found that insertion of IE into a chimeric murine CMV (mCMV) enhancer and human elongation factor-1α core (hEF) promoter in reverse orientation did not enhance expression stability, indicating that the effect of IE on expression stability is possibly promoter specific.
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Affiliation(s)
- Mariati
- a Bioprocessing Technology Institute; Agency for Science, Technology, and Research (A*STAR); Singapore, Republic of Singapore
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