Figure 3

Regulation of ATF-2 phosphorylation by p38 MAPK and inhibition by RA. B16 cells were treated with 10 μM RA for the indicated times. Cells were then harvested, extracted, and protein from each sample examined for total and phospho-specific JNK (A) or total and phospho-specific p38 (B) by western blotting as described in Materials and Methods. The results shown are representative of three individual experiments, which gave similar results. To determine the effect of inhibition of p38 enzyme activity on ATF-2 phosphorylation, we treated cells with or without 10 μM SB203580. At the indicated times, cells were harvested, extracted, and protein from each sample was examined for phospho-specific ATF-2 using western blotting as described in Materials and Methods. The result (C) shown is representative of three individual experiments, which yielded similar results.