Multiple tissue-specific sites of transcriptional initiation of the mouse anion antiport gene in erythroid and renal cells.

Primer extension and nuclease protection analysis were used to map the 5' end of mRNA transcripts of the single gene encoding the mouse erythroid anion-exchange protein, band 3. RNA from induced Friend murine erythroleukemia cells contains transcripts whose 5' ends are heterogeneous but that map to five clustered sites between 146 and 189 nucleotides upstream of the initiator AUG codon. The steady-state level of band 3 mRNA increases markedly following dimethyl sulfoxide-induced differentiation, but the pattern of transcription initiation does not vary. mRNA from anemic and normal mouse spleen exhibits the same pattern, with the addition of another transcript whose 5' end maps to position -260. In contrast, mRNA from mouse kidney has a single predominant transcript, mapping to -260. These data establish that the band 3 gene is expressed in kidney as well as in erythroid cells and suggest the presence of tissue-specific alternate promoter elements within the first exon of the band 3 gene. The nucleotide sequence of 1.7 kilobases of genomic DNA 5' to the first intron of the single-copy mouse band 3 gene, although moderately (G + C)-rich, has no "TATA" or "CAAT" boxes or other homologies with globin or other eukaryotic polymerase II promoter regions.