Codelivery to mammalian cells of a transcriptional factor with cis-acting element using cationic liposomes

The human immunodeficiency virus-1 transactivator protein (tat) was codelivered efficiently with a reporter gene under the control of a tat-responsive DNA element using different formulations of cationic liposomes. Expression of a tat-responsive reporter gene was induced by incubating cells with a mixture of purified recombinant tat protein, reporter DNA, and liposomes. Different cell lines were tested successfully as targets for the codelivery. Tat was shown to trans-activate the codelivered virus promoter specifically in the cells tested. Codelivery of tat with DNA is a useful model for studying the function of trans-acting factors and their cis-acting DNA elements. The currently available methods such as foot-printing only reveal the binding, but not the functional consequence of the binding, of the factor with the element. In addition, this system may prove useful as a model for high level and regulated transgene expression in target cells.