Inhibition of histone-mediated gene transfer in eucaryotic cells by anti-histone IgG

In our laboratory, the gene transfer efficiency of some lipofection reagent s (lipofectine, lipofectamine, DOTAP and Dosper) and histones H3 and H4 was compared to that of DEAF-Dextran (64). The histones H3 and H4 were found t o have the highest transfection efficiency of all the agents tested. In the present study we have analyzed other parameters important for gene deliver y by the histones H3 and H4. We transferred the HIV-1 tat gene to Jurkat ce lls and measured the transactivation of HIV-1-LTR by the transactivator pro tein, expressed in Jurkat cells. The expression of CAT as a reporter gene h ybridized to LTR was a direct measure of transactivation potential. In orde r to investigate whether the transfection was only due to the positive ioni c character of the histones H3 and H4 we tested other histones (H1 and H2A) and polylysine in our system. Under our experimental conditions, neither p olylysine, nor the histones H1 and H2A were able to promote gene transfer i n Jurkat cells. The inability of these reagents to promote gene transfer wa s not dependent on DNA condensation; in EMSA (Electrophoretic Mobility Shif t Assay) all these reagents exhibited a strong retardation of DNA. In the p resence of anti-histone-IgG the transfection potential of histones H3 and H 4 was diminished in a concentration - dependent manner. To investigate whet her the histone antibodies inhibited the condensation of DNA by histones we carried out gel retardation assays (EMSA) in the absence and in the presen ce of histone antibodies. Anti-histone-IgG had no effect on the retardation of histone-DNA complexes; on the contrary, retardation was increased. This observation has led us to postulate two models for the possible mechanism by which the histones H3 and H4 catalyze gene transfer in eucaryotic cells.