Cloning and characterization of the human ADH4 gene.
Human alcohol dehydrogenase (ADH) constitutes a set of isozymes and enzymes with different tissue and substrate specificities. The subunits are coded for by at least five gene loci, ADH1-ADH5. We now report the cloning and analysis of the human ADH4 gene coding for the class-II ADH with pi-subunits. The gene spans a region of 21 kb and is divided into nine exons and eight introns. The arrangement is the same as for all analyzed mammalian class-I genes, but the region covered is 50% larger than that in the human class-I genes. The nucleotide (nt) sequences of the exons, exon/intron boundaries and 5'- and 3'-untranslated regions were determined. The transcription start point (tsp) of the ADH4 gene was defined by primer extension and localized to a position 61 nt upstream from the ATG start codon. A TATA box and a CAAT element were identified by homology to consensus sequences for tsp. No DNA structures homologous to the glucocorticoid-responsive elements (GRE) present in the ADH2 gene were found in the upstream region of the ADH4 gene, but two structures with a 70% identity to the GRE consensus sequence were found at nonhomologous locations. The difference and the overall low degree of identity, 41%, of the upstream regions suggest different regulatory mechanisms for the class-I and class-II genes.