Fig. 1. Lower signal-transducing activity of soluble Delta1 protein. (A) Comparison of signal-transducing activity of sD1–Fc, sD1-Flag(His)6 and fD1. A transient reporter assay with a TP1-luciferase reporter plasmid, pGa981-6, was performed using fN2-CHO cells. Following transfection of pGa981-6 into fN2-CHO, sD1–Fc, sD1-Flag(His)6 or fD1-CHO was added to the transfected cells. Fold induction of the luciferase activity for each sample (mean of triplet measurements with standard deviation) was calculated against the control. The values are also shown in the graph. (B) N2-mediated transcriptional activation by sD1–Fc at increasing concentrations. Various concentrations of sD1–Fc were added to fN2-CHO cells transfected with pGa981-6. (C) The inhibitory effect of sD1–Fc on fD1-induced N2 signaling. fD1-CHO cells and sD1–Fc proteins at various concentrations were added simultaneously to the pGa981-6-transfected fN2-CHO cells. The same concentration of hIgG was added as a control.