We have developed a system to deliver DNA to mammalian cells utilizing a protein with specific receptor and DNA binding properties. The fusion protein was constructed with transforming growth factor a (TGFa) at the N-terminus and human telomeric repeat binding factor (hTRF) at the C-terminus (TGFa/TRF), expressed in E.coli, refolded from inclusion bodies and purified through ion exchange columns and a telomeric DNA (T2AG3 repeats)-specific affinity column. Binding to telomeric DNA was evident by mobility shift assay. TGFa binding activity to the epidermal growth factor (EGF) receptor was confirmed by competition studies whereby TGFa/TRF displaced 125I-EGF from EGF receptors. Plasmid DNA containing T2AG3 repeats and the E. coli Lac Z (beta-gal) reporter gene was bound to TGFa/TRF and the complexes were condensed by poly-L-lysine (pL), and added to cells. beta-gal expression was observed in EGF expressing cells above the background of pL alone and this increase inbeta-gal expression was blocked in the presence of excess EGF protein. Current work focuses on confirming specificity and improving efficiency by utilizing modified fusion proteins incorporating translocation domains to enhance intracellular trafficking of DNA to the nucleus. We will test this approach in vivo in mice and assess the feasibility of TGFa/TRF to deliver human artificial chromosomes into human cells.
