Digitoxin induces degradation of SRp20 and Tra2-β proteins. (A) Immunoblot analysis of digitoxin-treated HEK293 cells shows decreased expression of SRp20 and Tra2-β proteins. An unrelated splicing factor, PTB, remains unchanged. (B) Quantification of SRp20 and Tra2-β protein expression normalized to GAPDH and β-tubulin. Error bars, SE across three independent digitoxin treatments. (C) Immunoblot with pan-SR antibody reveals that other members of the SR family are largely unchanged after digitoxin treatment. (D) Co-incubation with MG-132 prevents depletion of SRp20 and Tra2-β and is quantified in E for three independent experiments. Error bars, SEM protein level.
