Regulation of gene expression in vivo by liposome-mediated delivery of a purified transcription factor.

We describe a procedure for assessing the functional activity in vivo of a glucocorticoid receptor derivative, T7X556, a mammalian transcriptional regulator that has been overexpressed in Escherichia coli and purified to homogeneity. The protein was assessed with DOTMA (N-[1-(2,3-dioleyloxy)propyl]-N,N,N-trimethyl-ammonium chloride) liposomes, which are internalized by cultured mammalian cells. T7X556 protein delivered in this manner localized rapidly to the nucleus and selectively enhanced expression from glucocorticoid response element-linked promoters, properties that are characteristic of this receptor derivative when it is synthesized endogenously in mammalian cells. Thus, in vivo activities of T7X556 were not disrupted by expression in bacteria or by biochemical purification. In general, liposome-mediated delivery may permit functional analyses of proteins that have been expressed in heterologous cells and manipulated in vitro.