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Haase, Rudolf; Argyros, Orestis; Wong, Suet-Ping; Harbottle, Richard P.; Lipps, Hans J.; Ogris, Manfred; Magnusson, Terese; Pinto, Maria G. Vizoso; Haas, Juergen; Baiker, Armin: pEPito: a significantly improved non-viral episomal expression vector for mammalian cells. In: BMC Biotechnology 2010, 10:20
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Abstract

Background: The episomal replication of the prototype vector pEPI-1 depends on a transcription unit starting from the constitutively expressed Cytomegalovirus immediate early promoter (CMV-IEP) and directed into a 2000 bp long matrix attachment region sequence (MARS) derived from the human beta-interferon gene. The original pEPI-1 vector contains two mammalian transcription units and a total of 305 CpG islands, which are located predominantly within the vector elements necessary for bacterial propagation and known to be counterproductive for persistent long-term transgene expression. Results: Here, we report the development of a novel vector pEPito, which is derived from the pEPI-1 plasmid replicon but has considerably improved efficacy both in vitro and in vivo. The pEPito vector is significantly reduced in size, contains only one transcription unit and 60% less CpG motives in comparison to pEPI-1. It exhibits major advantages compared to the original pEPI-1 plasmid, including higher transgene expression levels and increased colony-forming efficiencies in vitro, as well as more persistent transgene expression profiles in vivo. The performance of pEPito-based vectors was further improved by replacing the CMV-IEP with the human CMV enhancer/human elongation factor 1 alpha promoter (hCMV/EF1P) element that is known to be less affected by epigenetic silencing events. Conclusions: The novel vector pEPito can be considered suitable as an improved vector for biotechnological applications in vitro and for non-viral gene delivery in vivo.