DNA-binding by STAT-pTyr proteins in nuclear extracts from resistant (D_W^R) and sensitive (D_W^S) Daudi cells. EMSA was performed using indicated [³²P]-oligonucleotide probes. (A) After cell treatments with IFN-α (100 U/mL) for the times indicated, mobility shifts were evident for up to 48 hours with D_W^Sextracts, but for a maximum of just 8 hours with D_W^R extracts. Probes represented either theIRF-1 GAS promoter sequence or an ISG15 ISRE promoter element. (B) The D_W^S or D_W^R cells were treated with IFN-α (100 U/mL) for 2 hours. STAT DNA-binding complexes were identified by incubation of nuclear extracts with or without specific rabbit antisera before EMSA with the IRF-1 GAS probe. Supershifts were confined to samples treated with anti-STAT1.