FIG. 3.

Inducer-specific binding of Ets-1 to the endogenous TNF-α promoter. Formaldehyde cross-linking and chromatin immunoprecipitation of unstimulated (UN) and ionomycin-stimulated (Io)- or virus-stimulated (V) 68-41 T cells are shown. Following stimulation, the cells were treated with formaldehyde to cross-link endogenous protein and DNA. Samples of sonicated and purified chromatin were immunoprecipitated with the indicated antibodies, and DNA isolated from immunoprecipitated material was amplified by PCR with primers specific for the TNF-α gene. An increase in the relative amount of the amplified TNF-α promoter-specific PCR product indicates binding of the protein to the endogenous TNF-α promoter. To demonstrate that the efficiencies of cross-linking and immunoprecipitation of Ets-1 to the TNF-α promoter were equivalent in the mock-, virus-, and ionophore-treated samples, we included isotype-matched IgG antibodies (IgG control [IgG cont.]). gen., genomic.