Enhanced nuclear import and transfection efficiency of plasmid DNA using streptavidin-fused importin-β

In order to enhance the nuclear import of exogenous genes, novel plasmid DNA/importin-β conjugates, which consist of a biotinylated plasmid DNA and a recombinant streptavidin-fused importin-β, were prepared. The spacer length between plasmid DNA and biotin and the number of introduced biotin were adjusted. The microinjection of plasmid DNA/importin-β conjugates into the cytoplasm of NIH3T3 cells resulted in the nuclear localization of conjugates and the higher expression efficiency, compared to intact plasmid DNA alone. These results indicate that plasmid DNA/importin-β conjugates would be an important tool to enhance the nuclear localization of exogenous DNA in non-viral gene delivery system.