FIG. 3.

(A) Schematic representation of IL-15 promoter deletion constructs subcloned into pGL3-basic luciferase plasmid. (B) Induction of IL-15 promoter reporter activity in NDV(+) L929 cells. Reporter assays were carried out in NDV(+) and NDV(−) L929 cells. The luciferase activity is shown as the fold induction over the negative control, which is the luciferase plasmid with no promoter sequence (pGL3-basic). A maximum of 40-fold induction in the reporter activity was observed after NDV infection of L929 cells only when these cells were transfected with constructs bearing the IRF-E and NF-κB motifs (−706/Luc and −295/Luc). Deletion of this region containing IRF-E and NF-κB motifs in −243/Luc construct resulted in the loss of promoter activity after NDV infection, indicating that this region is essential for IL-15 promoter activation by NDV. Addition of NF-κB motif to the −243/Luc construct [−243(+NF-κB)/Luc] decreased the reporter activity about fourfold over that of −295/Luc after NDV infection. Addition of IRF-E motif to the −243/Luc construct [−243(+IRF-E)/Luc] caused an approximately twofold decrease in the promoter activity of the −295/Luc construct.