Bcl-3 expression in day-7, -10, and -14 BFU-E–derived erythroblasts. (A) Normal human BFU-E–derived erythroblasts were harvested and the whole cell lysates from 4 × 10⁵ (Bcl-3) or 2 × 10⁵ (IκB) cells were separated on a 10% polyacrylamide gel. Western analysis was performed with anti–Bcl-3 or anti-IκB antibodies and ECL. (B) Nuclear and cytoplasmic extracts were separated from day-10 cells. Fifty micrograms of nuclear (N) or cytoplasmic (C) extract was loaded onto each lane of a 10% gel and subjected to Western blotting. Two experiments were performed with anti–Bcl-3 or anti-IκB antibodies with identical results.