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

Abstract

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.

Nuclear factor-erythroid 2 (NF-E2) expression in normal and malignant megakaryocytopoiesis

“…Our mRNA analysis indicated that in normal human MKs the a isoform is much more highly expressed than the f isoform. This finding is also consistent with the preponderance of the a isoform found by Pischedda et al 13 and Moroni et al 51 in adult human BM and the myeloid component of mouse BM, respectively.…”

“…Although both isoforms are always coexpressed in every human cell type, the f mRNA is more abundant in fetal liver and less abundant in adult bone marrow (BM) compared to the a isoform. 13 Mice lacking p45 NF-E2 show megakaryocytosis and severe thrombocytopenia leading to fatal hemorrhage, and also have mild to moderate anemia. 2 Loss of p45 NF-E2 interferes with MK maturation at an advanced stage: ultrastructural studies reveal a markedly reduced number of granules and failure to form platelet fields.…”

“…10 The p45 NF-E2 subunit is almost exclusively expressed in hematopoietic progenitors and differentiated cells of the erythroid, MK, granulocyte and mast cell lineages. 5,[11][12][13][14] Human p45 NF-E2 has two isoforms (a and f), which differ in the 5Ј untranslated region. 13 The gene has three exons: whereas exons 2 and 3 are common to both isoforms, exon 1 differs between the two species (exon 1a and exon 1f).…”

“…5,[11][12][13][14] Human p45 NF-E2 has two isoforms (a and f), which differ in the 5Ј untranslated region. 13 The gene has three exons: whereas exons 2 and 3 are common to both isoforms, exon 1 differs between the two species (exon 1a and exon 1f). The two isoforms produce the same protein but are regulated by two different promoters and are expressed in different ratios during development.…”

Identification of an alternative form of human lactoferrin mRNA that is expressed differentially in normal tissues and tumor-derived cell lines

“…Further, our finding of a promoter-like sequence (containing a TATA box) immediately upstream for the 5Ј end of the ⌬LF mRNA suggests that transcription could initiate from two different promoters within the same LF gene and, as a result, specify alternative first exons. This is the situation that occurs with the human NF-E2 gene (49). In this case, use of alternative promoters specifies the major fetal and adult forms of the NF-E2 mRNA.…”