Cul4A-enforced expression attenuates differentiation into erythrocytes and reduces the accumulation of p27 protein.Cul4A-HA and empty vector control cells were induced to differentiate and aliquots of cells were taken 0, 24, and 48 hours after induction. Protein lysates were prepared, and 10 to 20 μg total protein for each sample was analyzed by immunoblot probed with antibodies that recognize HA, Cul4A, β-globin, c-Myc, GATA-1, p27, or actin. Actin was used as a loading control. Representative results of 3 independent experiments are shown.