Fig 5.

TGF-β induction leads to a loss of BMP-induced Smad1/5-Smad4 complexes and an increase in Smad1/5-Smad2/3 complexes. (A to C) MDA-MB-231 cells that were either untransfected (A and B) or transfected with nontargeting (NT) siRNA or an siRNA against Smad4 (C) were treated for 1 h with the ligands indicated. Whole-cell extracts were subjected to IP followed by Western blot assays with the antibodies shown. The lane marked “beads” correspond to an IP using beads alone. The inputs correspond to lysates prior to IP. (D) A mixture of purified recombinant PSmad1 and PSmad3 was immunoprecipitated with the antibodies shown or beads alone and then Western blotted as indicated.