FIG. 9.

HDAC1 activity is required for the induction of specific IFN target genes in ES cells. (A) Real-time RT-PCR analysis of the expression of Irf1 and Gbp2 in wild-type (WT) and HDAC1 KO ES cells. Cells were treated for 1 h with solvent (mock) or with 10 μg/ml IFN-γ (IFNγ), 20 ng/ml (33.1 nM) TSA alone (TSA), or IFN-γ and TSA together (IFN+TSA). Expression levels of Irf1 and Gbp2 were normalized to tubulin α1 levels and are shown relative to the expression levels in wild-type ES cells. Data presented are mean values for three independent experiments. (B) Presence of HDAC1 and hypoacetylation of histone H4 on Irf1 promoter are associated with its IFN-γ induction. Formaldehyde-cross-linked chromatin from wild-type and HDAC1 KO ES cells treated as described for panel A was immunoprecipitated with control antibodies (con) or antibodies specific for HDAC1, acetyl-H3 (AcH3), acetyl-H4 (AcH4), or the C terminus of histone H3 (cH3). DNA isolated from immunoprecipitated fractions was analyzed by semiquantitative PCR specific for proximal promoter regions of the Irf1 (left) and Gbp2 (right) genes.