Notch1 intracellular domain induces the degradation of the Snail protein at endogenous levels. (A) Huh7 and Hep3B cells were transfected with control siRNA and Notch1 siRNA, then evaluated for the expression of Notch1 intracellular domain (NICD) and Snail using immunoblot analysis. Densitometry results of Snail expression are given as intensity ratios listed below the blot. Con, control. (B) Mouse embryonic fibroblast (MEFs) and Hep3B cells were infected with murine stem cell virus (MSCV) or MSCV-NICD. After puromycin selection, cells were treated with 300 μM H2O2 for 72 hours and then were evaluated for endogenous Snail protein levels using immunoblot analysis. (C) Huh7 cells were infected with MSCV-Jagged1, then treated with 300 μM H2O2 for 72 hours. The expression of Jagged1, NICD and Snail was then analyzed by immunoblotting. DAPT (N-[N-(3, 5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester), an inhibitor of γ-secretase, was used to inhibit NICD activation. β-actin was used as an internal control.