Versatile eucaryotic vectors for strong and constitutive transient and stable gene expression

A set of three eucaryotic expression vectors (pKEX-1, pKEX-2-XR, and pKEX-2-XL) is described. They contain the human cytomegalovirus immediate early (HCMV-IE) promoter/enhancer element, allowing strong and constitutive expression of heterologous sequences transiently as well as in stably transfected cells which can be selected by using the hygromycin B resistance gene (hyR) in cis as a dominant selection marker. The pronounced promoter strength in the non-integrated state was demonstrated by comparing the HCMV-IE promoter/enhancer driven chloramphenicol acetyltransferase (CAT) gene expression with the CAT gene expression from a series of other viral and cellular promoters in the human teratocarcinoma cell line 2102Ep. The suitability of pKEX vectors for efficient establishment of stable transfectants was shown for cells of different origin, i.e., human T-lymphoma, human B-lymphoma, and murine fibroblast cell lines.