Specificity of binding of STAT-like DNA-binding factors in Dami/HEL and Mo7e cells to DNA containing the IRF-1 GAS sequence. (A) Dami/HEL cell nuclear extracts were incubated with [³²P]-labeled IRF-I GAS probe (lane 1) or with [³²P]-labeled probe plus a 50-fold excess of unlabeled oligonucleotide FIRE, ISRE, SIE, or MGFe, respectively (lanes 2 to 5). The DNA-binding complexes were separated in a 5% nondenaturing polyacrylamide gel. (B) Mo7e cell nuclear extracts from untreated control cells (lane 1) or cells treated with 400 ng/mL TPO (lane 2) were incubated with [³²P]-labeled IRF-1 GAS probe or with [³²P]-labeled probe plus a 50-fold excess of unlabeled oligonucleotide FIRE, ISRE, SIE, or MGFe, respectively (lanes 3 to 6). The DNA-binding complexes were separated in a 5% nondenaturing polyacrylamide gel. The autoradiograph shows the STAT-like DBF and NS.