Structure and expression of the rat class I alcohol dehydrogenase gene

Clones containing the rat class I alcohol dehydrogenase (ADH) gene were isolated from a Charon 4A genomic library. The gene spans approximately 13 kb and comprises nine exons and eight introns. The upstream 436 bp contain canonical TATA and CCAAT sequences, an inverted CACCC box, a TG3 box found in mouse and human ADH promoters, and regions of homology to glucocorticoid response elements. The 5'-untranslated region of the ADH transcript has the potential to form a stable stem-loop structure. The first intron contains an unusual stretch of alternating purines and pyrimidines similar to that found in the same location in the mouse ADH gene. The amino acid insertion found in rat alcohol dehydrogenase results from a shift in the 3' splice junction of the fourth intron which adds an extra three base pairs to the fifth exon. Intron-exon boundaries are otherwise identical to those in mouse and human ADH genes. H4IIE cells stably transfected with plasmids containing the chloramphenicol acetyltransferase (CAT) gene fused behind the first 436 bp of the promoter region express CAT, but the CAT activity is not inducible by dexamethasone. The elements responsible for glucocorticoid stimulation of ADH gene transcription appear to reside outside of this region.