The effect of SMAD1, SMAD4, and HJV on endogenous HAMP (A) or Hamp1 promoter-driven reporter expression (B) in HepG2 cells. Overexpression of SMAD1 andHJV induced expression of endogenous HAMP mRNA as assessed by Q-RT-PCR (A) as well as expression of firefly luciferase reporter driven by the 2.5-kb Hamp1 promoter (B), while the common mediator SMAD4 affected neither endogenous nor reporter expression. Values represent means and standard error of the mean (SEM) of at least 3 independent experiments.