CHOP protein increases during erythroid differentiation of Rauscher cells. Purified recombinant CHOP protein (rCHOP) or lysates from uninduced (0 hours) or DMSO-induced (48 and 72 hours) cells were subjected to SDS-PAGE and electrophoretic transfer. They were probed with either affinity-purified anti-CHOP antibodies (left panel) or purified preimmune IgG (right panel). Note the prominent increase in CHOP protein detected after 72 hours of induction (left panel, 72 hours).