FIG. 6.
HIV-1 expression is activated when U1 cells are cultured in the presence of a pan-RAR antagonist. (A) U1 cells were grown for 72 h in the absence or presence of various concentrations (10−7, 10−6, or 10−5 M) of the pan-RAR antagonist, BMS-204 493. Levels of p24 expression over the last 24 h of cell culture were measured by p24 antigen capture ELISA. The data are the averages (± the standard errors) of three independent experiments. (B) U1 cells were treated as described in panel A except that total cytoplasmic RNA was prepared from the cultures and analyzed for the expression of both HIV-1 (top panel) and α-tubulin (bottom panel) RNA by semiquantitative RT-PCR. The data are representative of three independent experiments. Tenfold serial dilutions of total cytoplasmic RNA prepared from the BMS-204 493-treated U1 cells were included as a standard (right panel). (C) U1 cells were grown for the indicated times in the absence or presence of either RA (10−6 M), the pan-RAR antagonist BMS-204 493 (10−5 M), or the pan-RAR agonist BMS-348 997 (10−5 M). Accumulation of p24 in the cell culture was measured by p24 antigen capture ELISA. The data are the averages (± the standard errors) of five independent experiments. (D) U1 cells were cultured in the presence or absence of various molar concentrations of RA (either 10−7 or 10−6 M) and various molar concentrations of BMS-204 493 (10−7, 10−6, or 10−5 M) for 72 h prior to activation with IL-1β/IL-6 for an additional 48 h. HIV-1 expression was measured by p24 antigen capture ELISA. The data are the means (± the standard errors) of three independent experiments.