Abstract
Primer extension and S1 nuclease analysis of human carbonic anhydrase I (HCA1) mRNA transcripts in erythroid and non-erythroid tissues show that the HCA1 gene has two promoters with different tissue specificities, separated by 36 kb of DNA. The promoter of the HCA1 gene which is active in non-erythroid tissue shows strong sequence similarity with a similar region in the mouse CA1 gene, but has two equally used transcription start sites.