Comparative Analysis of IRES Efficiency of Dicistronic Expression Vectors in Primary Cells and Permanent Cell Line

Abstract

Internal ribosome entry sites (IRES) are used in eukaryotic vectors for correlated co-expression of genes in eukaryotic cells. To investigate the IRESs? tissue and species specificity we have compared the translational efficiencies in dicistronic expression vectors mediated by the IRES of the bovine viral diarrhea virus (BVDV), the poliovirus type I IRES and by a vector harboring a random intercistronic region in certain primary cells and permanent cell lines derived from the liver, kidney, brain, cervix and endothelium. We found that IRES mediated expression differs considerably between the IRES elements used in one given cell necessitating the careful choice of IRES elements for a given cell type. BVDV IRES was superior to the strong poliovirus IRES in rodent neuronal and liver cells. The polio-IRES is stronger than the BVDV IRES in human neuronal, liver and kidney cells. The BVDV IRES tends to function optimal in the mouse (rodent) context, the poliovirus IRES in the human context. Interestingly, dicistronic expression differs considerably between primary cells and permanent cell lines. This indicates that for gene therapy of primary cells using dicistronic vectors, permanent cell lines cannot be recommended as models for gene expression.