FIG 1.

HDAC activity is not required for Toxoplasma to inhibit IFN-γ-induced IRF1 expression or induction of IFN-γ-responsive reporter cell lines. (A) HFFs were plated on coverslips, pretreated with 3 μM trichostatin A (TSA), an HDAC inhibitor, for 1 h, infected with RH parasites for 1 h, and subsequently stimulated with 100 U of IFN-γ/ml for 2 h. Control cells were also left unstimulated (US) and/or uninfected (UI). Cells were fixed, permeabilized, and stained with α-acetyl-histone H4 (green), α-IRF1 (red), and with Hoechst dye (nucleus, blue). A representative cell from each condition is shown. Scale bar, 10 μm. This experiment was performed twice with similar results. (B) HEK293 GAS (top) or STAT1 (bottom) reporter cell lines were pretreated with a variety of HDAC inhibitors (TSA, MC1568, MS-275, and sodium butyrate) or left untreated (DMSO, vehicle-only control) for 1 h. Cells were left uninfected (UI) or infected with RH parasites for 1 to 3 h, subsequently stimulated with 100 U of IFN-γ/ml for 14 to 20 h or left unstimulated (US), and lysed, and the luciferase activity was measured. The data were normalized within each experiment to the sample with the maximum luciferase activity, and the data shown are averages and the standard errors of the mean (SEM) from three independent experiments. Asterisks (*) indicate P < 0.05, or the P values are shown above bars.