PURIFICATION OF THE HUMAN NF-E2 COMPLEX - CDNA CLONING OF THE HEMATOPOIETIC CELL-SPECIFIC SUBUNIT AND EVIDENCE FOR AN ASSOCIATED PARTNER

The human globin locus control region-binding protein, NF-E2, was puri fied by DNA affinity chromatography. Its tissue-specific component, p4 5 NF-E2, was cloned by use of a low-stringency library screen with mur ine p45 NF-E2 cDNA (N. C. Andrews, H. Erdjument-Bromage, M. B. Davidso n, P. Tempst, and S. H. Orkin, Nature (London] 362:722-728, 1993). The human p45 NF-E2 gene was localized to chromosome 12q13 by fluorescent in situ hybridization. Human p45 NF-E2 and murine p45 NF-E2 are highl y homologous basic region-leucine zipper (bZIP) proteins with identica l DNA-binding domains. Immunoprecipitation experiments demonstrated th at p45 NF-E2 is associated in vivo with an 18-kDa protein (p18). Becau se bZIP proteins bind DNA as dimers, we infer that native NF-E2 must b e a heterodimer of 45- and 18-kDa subunits. Although AP-1 and CREB cop urified with NF-E2, no evidence was found for heterodimer formation be tween p45 NF-E2 and proteins other than p18. Thus, p18 appears to be t he sole specific partner of p45 NF-E2 in erythroid cells. Cloning of h uman p45 NF-E2 should permit studies of the role of NF-E2 in globin ge ne regulation and erythroid differentiation.