Evidence for three genes encoding class-I alcohol dehydrogenase subunits in baboon and analysis of the 5' region of the gene encoding the ADH beta subunit

Abstract

Five alcohol dehydrogenases (ADH; alcohol: NAD+ oxidoreductase; EC 1.1.1.1) have been identified in the baboon. All are homodimers of five distinct ADH subunits, with the two class-I ADH subunits being differentially expressed in the liver (the beta-subunit) and kidney. We have hybridized restriction-enzyme-digested baboon DNA to a 30-bp probe or a 337-bp DNA fragment, to reveal the presence of three genes encoding class-I ADH subunits in the baboon genome. This result was confirmed by the amplification of three different baboon ADH (bADH) nucleotide (nt) sequences, corresponding to exon 5 in the human gene encoding ADH beta (hADHB) from baboon DNA. Two of these sequences are identical to previously isolated liver and kidney cDNA nt sequences. These results are consistent with a phylogenetic analysis of the nt sequences of class-I hADH and bADH genes. Then, using primers based on the nt sequence of hADHB, we amplified a 336-bp DNA fragment, from genomic DNA, encoding the 5' region of the bADHB gene. In a 49-bp region of overlap, the nt sequence of this DNA fragment was identical to the sequence of a cDNA fragment amplified from baboon liver mRNA, whereas there were seven differences between this DNA fragment and the sequence of a cDNA amplified from baboon kidney mRNA. We used primer extension analysis to identify three adjacent transcriptional start points (tsp) for bADHB mRNA. Initiation of transcription at the most 5' bp leaves a 72-bp untranslated region. Examination of the sequence upstream from the tsp reveals a number of conserved putative regulatory sequence elements.