EMSA showing the binding of IRF-1 to a 32P labeled probe containing the IRF-1 consensus sequence. EMSA was performed with nuclear extracts obtained from untreated ESTDAB-056 (3) and ESTDAB-159 (5) melanoma cells or treated with 800 U/ml IFN-γ for 4 h (lanes 1, 4 and 7 corresponding to ESTDAB-056; and lanes 2, 6 and 8 corresponding to ESTDAB-159). A 50-fold molar excess of unlabeled IRF-1 probe was added to the binding reaction (lane 1, 2) to compete out the formation of a detectable complex. Anti-IRF-1 antibody was used to block IRF-1 binding to test the specificity of the interaction (lanes 7 and 8). Results shown are representative of at least three independent experiments.