IDENTIFICATION OF THE PROXIMAL ERYTHROID PROMOTER REGION OF THE MOUSEANION-EXCHANGER GENE

The AE1 gene is expressed in erythrocytes and the A-type intercalated cells of the kidney distal collecting duct, Although the 5' end of the principal transcript expressed in murine erythroid cells has previous ly been mapped to a cluster of transcription start sites located immed iately upstream of exon 1, the 5' end of the mouse kidney transcript h as not been identified. Using the anchored polymerase chain reaction t echnique to analyze mouse kidney AE1 mRNA, we identified an internal t ranscription start site located within erythroid intron 3. This site d efines an exon of 37 nucleotides that forms the 5' end of the mouse ki dney AE1 transcript, AE1 transcripts beginning at this internal start site could not be detected in RNA isolated from purified erythroid pro genitor cells or from erythroid cells undergoing erythropoietin-depend ent terminal maturation, although transcripts derived from the upstrea m site were abundant, indicating that only the upstream promoter is ac tive during erythropoiesis, Transient expression of reporter construct s in erythroid and nonerythroid cell lines identified a proximal upstr eam region of similar to 135 nucleotides that was active as a basal pr omoter. However, an additional similar to 200 nucleotides of upstream sequence was required for induced levels of activity in erythroid cell s, Although our functional approach does not yet indicate the precise sequences required for erythroid induction, the AE1 gene upstream regi on contains potential GATA sites at -154, -141, and -60; an E-box at - 163; CACCC or GGTGG motifs at -188, -121, and -88; and an AP-1/NF-E2-l ike site at -42. (C) 1996 by The American Society of Hematology.