Pleiotrophic functions of Epstein-Barr virus nuclear antigen-1 (EBNA-1) and oriP differentially contribute to the efficiency of transfection/expression of exogenous gene in mammalian cells

The EBNA1 gene and oriP sequence, originally derived from the EBV genome, provide plasmid vectors with artificial chromosome (AC)-like characteristics, including cytoplasm-to-nuclear transport, nuclear retention, replication and segregation of the DNA, while transcriptional up-regulation has been suggested as another activity of the EBNA1/oriP. Transfection as well as expression rates of various nonviral delivery vehicles are highly improved by inserting these genetic elements into plasmid DNA constructs. Here we differentially analyzed the contribution of each function of the EBNA1/oriP to the efficacy of electroporation-mediated genetic delivery and expression in mammalian cells. It was found that the EBNA1/oriP-mediated acceleration of genetic delivery and expression was predominantly due to the promotion of cytoplasm-to-nuclear recruitment as well as enhancement of transcription, while the episomal replication of the EBV-AC was not essentially involved.