Differential binding of the NFE3 and CP1/NFY transcription factors to the human γ- and ∈-globin CCAAT boxes

Naturally occurring nondeletional mutations affecting the distal CCAAT box of the human γ-globin gene promoter result in hereditary persistence of fetal hemoglobin in adult life. Although the distal CCAAT box is the target of several factors, including CP1/NFY, CDP, GATA-1 and NFE3, only NFE3 binding activity is consistently sensitive to well characterized mutations in this region such as G^-117 → A, C^-114 → T, and Δ13 hereditary persistence of fetal hemoglobin. We extensively characterized the binding specificities of NFE3 and demonstrated that NFE3 has unique properties with respect to other CCAAT box-binding proteins. Affinity-purified NFE3 from erythroid K562 cells binds the distal but not the proximal human γ-globin CCAAT box, the single CCAAT box of the human ∈-globin promoter, and the proximal CCAAT box of the evolutionarily related Galago crassicaudatus γ-globin gene. Within the ∈-globin CCAAT box, NFE3 represents the major and almost exclusive binding activity. Disruption of such a binding site essentially inactivates the ∈-globin promoter, suggesting that NFE3 plays an important role in the embryonic expression of this gene.