AP-1 is required for Nef-induced FasL promoter activation through p38. (A) Jurkat T cells were transfected with plasmid containing either the pVector or the AP1-Luc promoter plasmid, and the pNef plus AP1-Luc promoter plasmid or the pNef plus AP1-Luc promoter plasmid and treated with p38 inhibitors (1 μM) as indicated in “Materials and methods.” (B) Jurkat T cells were transfected with the hFasL-Luc promoter plasmid, hFasL-Luc promoter plasmid plus pNef, or pNef plus hFasL^mut-Luc (mutation in the AP-1 binding site) promoter plasmid as indicated. (C) As a control, Jurkat cells were transfected with hFasL^mut-Luc or hFasL^mut-Luc plus an expression construct for pRelA (p65) as indicated. Luciferase activity in whole-cell lysates was assayed after 12 to 18 hours and is shown as the mean value ± SEM. Transfection efficiency was monitored by cotransfection of a plasmid encoding β-gal, and results were normalized to β-gal levels. Similar results were obtained in 3 independent experiments. (D) Nef-deleted virus failed to induce AP-1 transcription. Jurkat cells were transiently transfected with pAP1-Luc vector as indicated. At 48 hours after transfection, cells were infected with NL4-3 Wt with or without p38 inhibitor or NL4-3 ΔNef viruses as indicated. Luciferase activity in whole-cell lysates was monitored after 24 hours and is shown as the mean value ± SEM. Transfection efficiency was monitored by cotransfection of a plasmid encoding β-gal. These data are representative of 2 independent experiments. The asterisks indicate significant differences between cells infected with Wt virus (P < .02).