Regulation of mouse p45 NF-E2 transcription by an erythroid-specific GATA-dependent intronic alternative promoter

The erythroid-enriched transcription factor NF-ES is composed of two subuni ts, p45 and p18, the former of which is mainly expressed in the hematopoiet ic system. We have isolated and characterized the mouse p45 NF-E2 gene; we show here that, similar to the human gene, the mouse gene has two alternati ve promoters, which are differentially active during development and in dif ferent hematopoietic cells. Transcripts from the distal promoter are presen t in both erythroid and myeloid cells; however, transcripts from an alterna tive proximal Ib promoter, lying in the first intron, are abundant in eryth roid cells, but barely detectable in myeloid cells. During development, bot h transcripts are detectable in yolk sac, fetal liver, and bone marrow. Tra nsfection experiments show that proximal promoter Ib has a strong activity in erythroid cells, which is completely dependent on the integrity of a pal indromic GATA-1 binding site. In contrast, the distal promoter la is not ac tive in this assay. When the promoter Ib is placed 3' to the promoter la an d reporter gene, in an arrangement that resembles the natural one, it acts as an enhancer to stimulate the activity of the upstream promoter la.