Studies on the preparation and interaction of modified transferrin-DNA complexes with HeLa cells.
The correction of human genetic disorders by transfer of genetic material to cells is under intensive investigation in a number of 1aboratories. One possible way of trying to achieve the transfer of nucleic acid is by attaching DNA to a protein which has specific receptors on cells and which undergoes receptor-mediated endocytosis. In order to make use of the ligand protein-receptor approach for DNA transfer, iron-loaded human serum transferrin has been modified with the water soluble carbodiimides N-ethy1-N I -(3-dilllethy1aminopropyl) carbodiimide (CDI) and its quaterary analogue (ECDI) to give modified N-acy1urea transferrins. N-Acy1urea CDI (Fe 3+) transferrin and N-acy1urea CDI (Fe ) transferrin have been found to interact with and bind DNA in a reversible manner which i! dependent on ionic strength.  N-Acy1urea CDI+(Fe3+) transferrin binds to transferrin receptors on Hea cells in culture and undergoes internalization through receptor-mediated endocytosis. Binding of the modified transferrin in the presence of calf thymus DNA to transferrin receptors also takes place. However, although internalization in the presence of DNA doe! appear to take place, the results of the internalization are not fully understood. Transfection studies with N-acy1urea CDI (Fe ) transferrin and plasmid pBR322 DNA as well as plasmid ptkNEO DNA complexes in the HeLa cell system are reported. The results of a number of transfection experiments suggests that N-acy1urea transferrins are capable of transfecting DNA (ptkNEO DNA), carrying genes for resistance to the antibiotic Geneticin (G41S) in the HeLa cell system. However, further development of the transfection system is necessary in order that consistantly reproducible results may be achievd.