ISOLATION OF A DIFFERENTIALLY REGULATED SPLICING ISOFORM OF HUMAN NF-E2

The transcription factor NF-E2 (nuclear factor erythroid 2), interacti ng via DNA motifs within regulatory regions of several hematopoietic g enes, is thought to mediate the enhancer activity of the globin locus control regions. By screening a human fetal liver cDNA library with pr obes derived from mouse NF-E2, we have isolated a splicing variant of the NF-E2 gene (fNF-E2) that differs in the 5' untranslated region fro m the previously reported cDNA (aNF-E2). The fNF-E2 isoform is transcr ibed from an alternative promoter located in the 3' end of the first i ntron and joined by alternative splicing to the second and third exons , which are shared by both RNA isoforms. Although the two forms produc e the same protein, they are expressed in different ratios during deve lopment, fNF-E2 is more abundant in the fetal liver and less abundant in the adult bone marrow compared to the previously described form. Th eir distribution apparently follows the differential expression of fet al and adult hemoglobins.