Activation of the ΔNp63 promoter by Smad2 and IKKα, and by stimulation with TGF-β in A431 cells. Results of the luciferase assay with 2kΔN (A),2kΔN mutants (B), 2kTA (C) and the PAI-1 promoter (D) are shown. Cells were incubated with (+) or without (-) TGF-β1 (TGF-b1) (10 ng/ml [32]) for 24 hours after serum starvation for 6 hours. Data (mean ± SD; n ≥ 3) are presented as relative luciferase activities in comparison with the control activity (1.0) produced by 2kΔN-luc transfected with empty expression vector pRcCMV (Vec). Statistic significance: **P < .01, *P < .05, versus control experiment with Vec. Indicated in parentheses are amounts of the cytomegalovirus promoter-driven gene expression vectors relative to 2kΔN-luc (= 1). IKKa indicates IKKα.