Gene transfer using a novel fusion protein, GAL4/invasin

The delivery of DNA to target cells using simple, defined, nonviral systems has become an area of intense interest in gene therapy. We describe here the development and characterization of one such novel system. A recombinant, bifunctional, fusion protein was expressed and purified from Escherichia coli. This protein consists of the DNA-binding domain of the yeast transcription factor GAL4 fused to the cell binding, internalization domain of the Yersinia pseudotuberculosis inv gene product, invasin. This protein, GAL4/Inv, together with poly-L-lysine, formed complexes with a chloramphenicol acetyltransferase (CAT) reporter plasmid that contains eight repeats of the GAL4 consensus recognition sequence. These complexes were shown to transfect target cells in an invasin receptor-dependent manner, resulting in transient CAT expression. A simple, targeted DNA delivery vehicle, as we describe here, represents a viable approach to nonviral gene delivery.