FIG. 7.

The c-myc IRES is downstream of p38 MAPK. (A) cells were cotransfected with dicistronic reporter plasmids containing the c-myc IRES (pGL3Rutr) and β-galactosidase (pcDNA3.1/HisB/LacZ), and half the samples were preincubated for 1 h with 40 μM SB203580. Open circles, absence of inhibitor; closed circles, presence of inhibitor. Cells were then treated with 0.25 μg of TRAIL per ml, and samples were harvested at the time points shown and assayed for firefly luciferase and β-galactosidase activity. The relative ratio of firefly luciferase to β-galactosidase is shown. (B) Cells (10⁶) were incubated with TRAIL with or without a 1-h preincubation with 40 μM SB203580. Samples were harvested at the time points shown, analyzed by PAGE and Western blotting with an anti-c-Myc antibody, and then stripped and reprobed with an anti-PARP antibody. (C) p38 MAPK activity was assayed in the presence (closed squares) or absence (open squares) of SB203580 (preincubation for 1 h) followed by the addition of 0.25 μg of TRAIL per ml. As expected, the activity of this enzyme is induced up to 10-fold during apoptosis, and this induction is inhibited by the presence of the inhibitor.