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 β-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. © 2010 Haase et al; licensee BioMed Central Ltd.
Haase, R., Argyros, O., Wong, S. P., Harbottle, R. P., Lipps, H. J., Ogris, M., … Baiker, A. (2010). PEPito: A significantly improved non-viral episomal expression vector for mammalian cells. BMC Biotechnology, 10. https://doi.org/10.1186/1472-6750-10-20