Effect of the Kozak sequence on transient expression of human coagulation factor IX (FIX) minigene in mammalian cells

The positive effect of Kozak sequence on the translational efficiency of the eukaryotic genes has been noted and can be used in order to increase recombinant protein expression. A CMV-regulated human factor IX (hFIX) –expressing plasmid containing factor IX minigene– equipped with the Kozak sequence was constructed. After verification, the constructed plasmid which was in parallel with a Kozak-less hFIX-minigene expressing plasmid (the positive control) and a parental plasmid (pcDNA3) as the negative control were used to transfect Chinese Hamster Ovary (CHO) cells, separately. The expression of the recombinant hFIX (rhFIX) was evaluated by performing one-stage coagulation test on the cultured media collected from the transfected cells after 2 and 3 days. This study indicated the expression of biologically active hFIX by cells transfected with either of the recombinant plasmids in comparison with negative control. The data also shows a higher coagulation activity in the cultured media taken from the cells transfected with the Kozak: hFIX-minigene compared to that of the cells transfected with the Kozak-less hFIX-minigene. In addition to confirming the positive effect of Kozak sequence on the translational efficiency of the eukaryotic genes, the constructed plasmids provide new tools for systematic analysis of the ability of the transfected cells for the production of biologically active hFIX.