Fig. 4.
Sp1 trans-activates αENaC via the +222/+229 Sp1 element. A: stable mIMCD3 cell lines harboring the pcDNA3.1-Zeo-1.3ENaCα-Luc (WT) or pcDNA3.1-Zeo-1.3ENaCαΔSp1+222/+229-Luc (ΔSp1+222/+229) constructs in Fig. 2 were transiently transfected with an Sp1 expression vector or its gutless vector. After 24 h, the cells were treated with vehicle or aldosterone for 24 h, and then the firefly activities were measured and normalized to cell protein content. The value obtained for vehicle-treated, empty vector-transfected cells harboring pcDNA3.1-Zeo-1.3ENaCα-Luc (WT) was set to 1, and the other conditions were normalized to it. The values shown are the mean of triplicate determinations or 4 independent experiments. Error bars indicate ± SE. *P < 0.05 vs. vehicle-treated, empty vector-transfected WT controls. **P < 0.05 vs. aldosterone-treated, empty vector-transfected WT controls. B: pcDNA3.1-Zeo-1.3ENaCα-Luc (WT) and pcDNA3.1-Zeo-1.3ENaCαΔSp1+222/+229-Luc (ΔSp1+222/+229) cell lines were transiently transfected with control siRNA or Sp1-specific siRNA. After 24 h, the cells were treated with vehicle or aldosterone for 24 h, and then the firefly activities were measured and normalized to cell protein content. The value obtained for control siRNA-transfected cells harboring pcDNA3.1-Zeo-1.3ENaCα-Luc (WT) was set to 1, and the other conditions were normalized to it. The values shown are the mean of triplicate determinations of 3 independent experiments. Error bars indicate ± SE. *P < 0.05 vs. vehicle-treated, control siRNA-transfected. **P < 0.05 vs. aldosterone-treated, control siRNA-transfected.