Bcl-3 is hyperphosphorylated in TF-1 cells and BFU-E–derived erythroblasts. (Top) Whole cell lysates (W) and nuclear (N) and cytoplasmic (C) extracts were prepared from Epo-induced or GM-CSF–induced TF-1 cells. Thirty micrograms of each extract was incubated with or without 26 U of CIP at 37°C for 40 minutes and then subjected to Western blotting assay with anti–Bcl-3 antibody and ECL. (Bottom) Thirty micrograms of whole cell lysate (W) from normal human heart tissue or 50 μg from day-10 BFU-E–derived erythroblasts was also incubated with or without 26 U CIP and subjected to Western blotting with anti–Bcl-3 as described in the Materials and Methods. Three experiments were performed with similar results. (+) with CIP; (−) without CIP.