title: A novel regulatory element (E77) isolated from CHO-K1 genomic DNA enhances stable gene expression in Chinese hamster ovary cells.
abstract: Vectors flanked by regulatory DNA elements have been used to generate stable cell lines with high productivity and transgene stability; however, regulatory elements in Chinese hamster ovary (CHO) cells, which are the most widely used mammalian cells in biopharmaceutical production, are still poorly understood. We isolated a novel gene regulatory element from CHO-K1 cells, designated E77, which was found to enhance the stable expression of a transgene. A genomic library was constructed by combining CHO-K1 genomic DNA fragments with a CMV promoter-driven GFP expression vector, and the E77 element was isolated by screening. The incorporation of the E77 regulatory element resulted in the generation of an increased number of clones with high expression, thereby enhancing the expression level of the transgene in the stable transfectant cell pool. Interestingly, the E77 element was found to consist of two distinct fragments derived from different locations in the CHO genome shotgun sequence. High and stable transgene expression was obtained in transfected CHO cells by combining these fragments. Additionally, the function of E77 was found to be dependent on its site of insertion and specific orientation in the vector construct. Our findings demonstrate that stable gene expression mediated by the CMV promoter in CHO cells may be improved by the isolated novel gene regulatory element E77 identified in the present study.
authors.affiliation: Department of Bioprocess Engineering, Korea University of Science and Technology (UST), Daejeon, Republic of Korea.
authors.forename: Shin-Young
authors.initials: SY
authors.lastname: Kang
authors.affiliation: Department of Bioprocess Engineering, Korea University of Science and Technology (UST), Daejeon, Republic of Korea.|Biotechnology Process Engineering Center, KRIBB, Ochang, Republic of Korea.
authors.forename: Yeon-Gu
authors.initials: YG
authors.lastname: Kim
authors.affiliation: Biotechnology Process Engineering Center, KRIBB, Ochang, Republic of Korea.
authors.forename: Seunghee
authors.initials: S
authors.lastname: Kang
authors.affiliation: Department of Bioprocess Engineering, Korea University of Science and Technology (UST), Daejeon, Republic of Korea.|Biotechnology Process Engineering Center, KRIBB, Ochang, Republic of Korea.
authors.forename: Hong Weon
authors.initials: HW
authors.lastname: Lee
authors.affiliation: Department of Bioprocess Engineering, Korea University of Science and Technology (UST), Daejeon, Republic of Korea. eglee@kribb.re.kr.|Biotechnology Process Engineering Center, KRIBB, Ochang, Republic of Korea. eglee@kribb.re.kr.
authors.forename: Eun Gyo
authors.initials: EG
authors.lastname: Lee
mesh_terms: D000818:Animals; D016466:CHO Cells; D003001:Cloning, Molecular; D006224:Cricetinae; D003412:Cricetulus; D015870:Gene Expression; D005818:Genetic Engineering / Q000379:methods*; D016678:Genome; D015698:Genomic Library; D011401:Promoter Regions, Genetic; D012045:Regulatory Sequences, Nucleic Acid; D019076:Transgenes
keywords: CMV promoter; Chinese hamster ovary cells; Green fluorescent protein; Regulatory DNA element; Stable gene expression