Variant chicken kidney AE1 anion exchanger transcripts are derived from a single promoter by alternative splicing

Abstract

Previous studies have demonstrated that three variant transcripts, AE1–3, AE1–4 and AE1–5, are derived from the AE1 gene in chicken kidney. These variant transcripts encode AE1 anion exchangers that possess alternative N-terminal cytoplasmic domains. To determine the mechanisms involved in generating these transcripts, a genomic clone, containing the unique sequences at the 5′ ends of the AE1–4 and AE1–5 transcripts, was isolated. Characterization of this clone revealed that the sequences at the 5′ ends of the AE1–3, AE1–4 and AE1–5 transcripts were each present within an approx. 1.2-kb BamHI fragment of the chicken AE1 gene. RNA blotting and RNase protection analyses using probes derived from this genomic clone have shown that the AE1–4 variant corresponds to the approx. 4.5-kb chicken kidney AE1 transcript, while the AE1–5 variant corresponds to the approx. 5.1-kb transcript. These studies have shown that the AE1–5 transcript extends further 5′ than had been previously shown from cDNA cloning studies, and contains the sequence present at the 5′ end of the AE1–4 transcript. In addition, primer extension analyses have shown that the variant kidney AE1 transcripts initiate transcription from a common site. This result indicates that the expression of the AE1–3, AE1–4 and AE1–5 transcripts is regulated by a single promoter, P3, that is distinct from the PI and P2 erythroid-specific promoters of the chicken AE1 gene.