Isolation of a differentially regulated splicing isoform of human NF-E2

The transcription factor NF-E2 (nuclear factor erythroid 2), interacting via DNA motifs within regulatory regions of several hematopoietic genes, is thought to mediate the enhancer activity of the globin locus control regions. By screening a human fetal liver cDNA library with probes 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 from the previously reported cDNA (aNF- E2). The fNF-E2 isoform is transcribed from an alternative promoter located in the 3' end of the first intron and joined by alternative splicing to the second and third exons, which are shared by both RNA isoforms. Although the two forms produce the same protein, they are expressed in different ratios during development. fNF-E2 is more abundant in the fetal liver and less abundant in the adult bone marrow compared to the previously described form. Their distribution apparently follows the differential expression of fetal and adult hemoglobins.