Comparison of mammalian cell expression vectors with and without an EBV-replicon

Abstract

We have characterized the properties of an Epstein-Barr virus vector (EBV-CMV) and compared its expression potential with a respective integrating vector (CMV). These vectors were used to express chloramphenicol acetyltransferase (CAT) gene in human HeLa, 293, monkey CV-1, dog MDCK, and hamster R 1610 cells. The EBV-CMV-cat DNA replicates extrachromosomally in HeLa, 293 and CV-1 cells, where also high expression of CAT gene was observed. The EBV-CMV vector integrated in MDCK and R 1610 cells and the CMV vector integrated in all cells tested. Integration yielded mostly clones with low CAT expression. In all cell lines, except HeLa cells, the existence of the extrachromosomal but not the integrated vector DNA is strictly dependent on the Hygromycin B selection pressure. The extrachromosomal state of the EBV vector is a prerequisite for good expression particularly in human and monkey cells.

IPTG-Inducible Episomal Expression System for Exogenous Genes in Primate Cells

“…Episomal vectors such as those derived from the EBV replicon have several advantages (8,11,12,14). First, the absence of integration into host-cell chromosomes obviates potential problems of integration position effects on gene expression and reduces the likelihood of any rearrangement of the transfected DNA (8,11,12,14). Second, the expression levels of transfected genes are consistently higher than expression from non-episomal vectors (11).…”

“…First, the absence of integration into host-cell chromosomes obviates potential problems of integration position effects on gene expression and reduces the likelihood of any rearrangement of the transfected DNA (8,11,12,14). Second, the expression levels of transfected genes are consistently higher than expression from non-episomal vectors (11). Third, recovery of the transfected episomal plasmids is simple and efficient using the Hirt's extraction procedure (4,9).…”