(A) STAT binding to the IRF-1 GAS by IFN-, IL-2, IL-12, or IL-15. T cells were stimulated with IFN-, IL-2, IL-12, or IL-15 for the times indicated, and nuclear extracts were prepared. The extracts were incubated with ³²P-labeledIRF-1 GAS probe, and the DNA binding activity was analyzed by EMSA. (B) IFN-–induced STAT1, STAT3, and STAT4 DNA binding toIRF-1 GAS. T cells were stimulated with IFN- for 30 minutes, and nuclear extracts were prepared and incubated for 1 hour on ice with anti-STAT antibodies, followed by binding to ³²P-labeledIRF-1 GAS. The experiment was repeated three times with similar results.