HDAC inhibitors differ in their ability to suppress IFNα induction of PML. Western blot analysis of PML protein levels in HeLa cells (A-C) or HSFs (D) simultaneously treated for 24 hours with IFNα and one of the following HDAC inhibitors: BUT, VA, SAHA, or MS-275. The final concentrations of the inhibitors are indicated. Cell protein lysates (25 μg total protein) were loaded on 8% SDS gels (actin band of Ponceau S–stained membrane or GAPDH signal is shown to demonstrate equal loading). (E) Real-time RT-PCR quantification of HDAC inhibitors' suppression of IFNα-induced PML mRNA. HeLa cells were treated with 1000 U/mL IFNα alone or simultaneously with a particular HDAC inhibitor for 8 hours. PML mRNA levels were normalized to GAPDH. Statistically significant differences compared with the IFNα-treated cells are indicated by ***P < .001, **P < .005, or *P < .05; 3 independent experiments were evaluated. Error bars represent standard error.