Mapping of SMAD1, HJV, BMP4, and BMP9 responsive region of Hamp1. Constructs containing various fragments of the murine Hamp1 promoter linked to a firefly reporter were transfected into HepG2 cells and either cotransfected with SMAD1 (A) or hemojuvelin (B) or treated with 10 ng/mL BMP4 (C) and BMP9 (D) for 12 to 16 hours. Firefly/Renilla ratio of untreated 2.5-kb Hamp1 WT construct was set as 1.00. Mean and SEM of the relative firefly/Renilla ratios of at least 3 independent experiments are shown.