Fig. 4. BMP4 and Notch 1 ICD synergistically activate the Hey1 promoter. (A) Transfection of C2C12 cells with SMAD1 in the absence (–) or presence (+) of exogenous BMP4 (50 ng/ml), measured by activation of a Hey1-luciferase reporter construct. Note the induction when SMAD1-transfected cells are exposed to BMP4. (B) Transfection with Notch 1 ICD combined with BMP4 stimulation (50 ng/ml). Note the effect of BMP4 on Notch 1 ICD-transfected cells. (C) Co-transfection with Notch 1 ICD and SMAD1, in the absence (white bars) or presence (black bars) of exogenous BMP4 (50 ng/ml). (D) Transfection of Cos-7 cells with Notch 1 ICD, combined with BMP4 stimulation (50 ng/ml) or transfection with Alk6CA.