FIGURE 3.
p38δ is required for PKCδ and MEK3-dependent activation of p21Cip1 promoter transcription. A, KERn were transfected with 1 μg of p21-2326 luciferase reporter plasmid in the presence of 1 μg of empty vector or vector encoding PKCδ, MEK3, or DNp38α. Levels were adjusted to a total of 3 μg per transfection by addition of empty vector (EV). At 24 h post-transfection, cell extracts were prepared and assayed for promoter activity. B, KERn (1 million cells per group) were electroporated with 3 μg of control or p38δ siRNA. At 48 h post electroporation, the cells were harvested and counted, and 0.5 million cells from each group were re-electroporated with 1 μg of endotoxin-free p21-2326 luciferase reporter plasmid in the presence of 2 μg of PKCδ or MEK3 encoding endotoxin-free plasmid or the empty vector. After an additional 24 h, cell extracts were prepared for luciferase assay. The values are mean ± S.E. (n = 3). The asterisks indicate significant differences (*, p < 0.005).