Osx inhibits IL-1α promoter activity through one Sp1-binding site on IL-1α promoter. Intracellular occupancy of Osx on the IL-1α promoter in Dunn and DLM8 cells. Top, primers used to amplify the putative regulatory and non-regulatory regions present in the IL-1α gene. P1, P2, P3, and P4, four pairs of primers used in the ChIP assay. Arrowheads, boundaries of the PCR products. Formaldehyde cross-linked chromatin samples (1 mg) from mouse osteosarcoma cell lines Dunn or DLM8 were subjected to immunoprecipitation with either affinity-purified Osx antibody or acetylated histone H3 antibody and subjected to PCR amplification with primer pair P1, P2, P3, and P4. Normal rabbit IgG (1 μg) was used as control for each ChIP. Input represents 0.2% of each soluble chromatin fraction used for immunoprecipitation.