Figure 1.

Decreased NOTCH1 levels in As₂O₃-treated keratinocytes. A and B, HaCaT cells were untreated or treated with As₂O₃ (As). 24 h post-treatment, cells were either untreated or treated with MG132/carfizomib for 5 h before collection; immunoblotting was performed with the indicated antibodies. C, HaCaT cells were treated with As₂O₃ for 24 h before collection, cell extract was immunoprecipitated (IP) using an antibody against NOTCH1, and immunoblotting (WB) was performed with the indicated antibodies. D, HaCaT cells were transfected with either pCDNA3 or NOTCH1-IC (encoding the human Notch1-IC, 1757–2555). 36 h post-transfection, cells were treated with As₂O₃ for 24 h before collection; immunoblotting was performed with the indicated antibodies. D (right), HaCaT cells were co-transfected with the NOTCH-responsive promoter 12xCSL, and the NOTCH1-IC plasmid was then treated with increasing amounts of As₂O₃ (5 and 10 μm) 12 h before collection. Average and S.D. values were calculated from triplicate samples. ***, p < 0.0001.