Plasmid DNA entry into postmitotic nuclei of primary rat myotubes.

These studies were initiated to elucidate the mechanism of DNA nuclear transport in mammalian cells. Biotin- or gold-labeled plasmid and plasmid DNA expression vectors for Escherichia coli beta-galactosidase or firefly luciferase were microinjected into the cytoplasm of primary rat myotubes in culture. Plasmid DNA was expressed in up to 70% of the injected myotubes, which indicates that it entered intact, postmitotic nuclei. The nuclear transport of plasmid DNA occurred through the nuclear pore by a process common to other large karyophilic macromolecules. The majority of the injected plasmid DNA was sequestered by cytoplasmic elements. This understanding of plasmid DNA nuclear transport provides a basis for increasing the efficiency of gene transfer.