Figure 2.
TGF-β inactivation of Cdk2 is independent of Cdk inhibitors. (A) Primary anti-cyclin E immunoprecipitation (IP) followed by reimmunoprecipitation with anti-Cdk2 or anti-cyclin E antibodies from 35S-methionine-labeled control and TGF-β-treated HepG2 cells. (B and C) TGF-β treatment of HepG2 cells does not alter p21 or p27 levels associated with cyclin:Cdk complexes. Note increased association of cyclin E with p27 in HGF-treated cells. (D) In vitro mixing experiment of increasing amounts of TGF-β-treated WCE into control WCE followed by anti-cyclin E immunoprecipitation-kinase assay. (E) TGF-β treatment of HepG2 cells does not result in increased Thr14/Tyr15 phosphorylation. Anti-cyclin E immunoprecipitates from control and TGF-β-treated cells were incubated with glutathione S-transferase-CDC25A protein followed by Cdk2 kinase assay.