Figure 3.

Loss of Cdk2 Thr¹⁶⁰ phosphorylation in TGF-β-treated HepG2 cells. Primary immunoprecipitation (IP) with anti-Cdk2 (A) and anti-cyclin E (B) antibodies followed by reimmunoprecipitation with anti-Cdk2 antibodies from ³⁵S-methionine-labeled control (ctrl) and TGF-β-treated cells. Cdk2 migrates as two species: the faster migrating, active form contains phospho-Thr¹⁶⁰ whereas the slower migrating, inactive forms contain nonphosphorylated Thr¹⁶⁰. The presence of phospho-Thr¹⁴ and phospho-Tyr¹⁵ on Cdk2 do not affect migration (32).