FIG. 9.

The down-regulation of p38 activity by dexamethasone is delayed and requires ongoing transcription. (A) HeLa-TO cells were UV stimulated, and p38 activity was measured after 30 min, with or without dexamethasone (Dex) treatment as shown. The times of addition of dexamethasone are indicated with respect to the UV stimulus at t = 0. (B) HeLa-TO cells were incubated in the absence or presence of actinomycin D (ActD; 5 μg/ml) 15 min before the addition of 1 μM dexamethasone. After 2 h, cells were UV stimulated, and p38 MAPK activity was measured in immune complex assays 30 min later. Fold activation compared to unstimulated cells is shown under the panel. Each experiment was performed twice, with qualitatively identical results.