Differentiation of murine erythroleukemia cells results in the rapid repression of vimentin gene expression

Elucidation of the events occurring in mammalian erythro-poiesis has been facilitated by the study ofmurine erythroleu-kemia cell differentiation in vitro. Friend murine erythroleu-kemia (MEL) ' cells originally were derived from Friend leu-kemia virus-infected tumor,implants and proliferate rapidly in culture (13). Exposure to a variety of chemical agents, such as dimethyl sulfoxide (DMSO), hexamethylene-bisacetamide (HMBA), or butyric acid induces MEL cells to differentiate (14, 29, 48; for a review see reference 35). Among the char-acteristic phenomena observed during terminal differentiation ofMEL cells are a maturation from a basophilic erythroblastic appearance to an orthochromatophilic normoblastic pheno-type (14), a loss of proliferative capacity (12, 21), alterations in purine metabolism (46), increases in iron uptake and heme synthesis (14), an elevation of heme synthetic enzyme activi-ties (10, 54), the induction of globin mRNAs (43, 46, 50), and the accumulation of hemoglobin (14). The tremendous induction of hemoglobin synthesis and accumulation in chemically-induced MEL cells, a distinctive feature of eryth-roid terminal differentiation in vivo, is effected by transcrip-tional activation of globin genes (2, 34, 44) ; the relative accumulation of globin mRNAs also may be modulated by the stabilization of these messages and/or by the destabiliza