The ethanol-active alcohol dehydrogenase (ADH-A2) expressed at high levels in mouse liver is encoded by the Adh-1 gene. Inbred strains differ in the amount of ADH-A2 expressed. We report here the cloning and sequencing of the Adh-1 genes from mouse strains that express high and low amounts of ADH-A2 in liver (strains YBR/Ki and Balb/c respectively). The gene contains nine exons, and encodes an ADH-A subunit identical to that encoded by the cDNA isolated from DBA/2J, a strain with low liver ADH activity. This demonstrates that the difference between strains in liver ADH activity is not due to differences in the amino acid sequence of the ADH-A2. The 5'-nontranslated region and at least the first 225 bp 5' to the transcriptional start point are identical in both strains. We have found restriction fragment length polymorphisms in the Adh1 gene that correlate with the level of expression of ADH-A2 in different strains. One of these RFLPs is within a remarkably long (288 bp) strictly alternating purine-pyrimidine sequence located in the first intron. This region in YBR/Ki contains 25 copies of the sequence ATGT(A/G)T (four of them inverted), which closely resembles important elements in the SV40 enhancer region. Balb/c mice, which express Adh-1 at lower levels, have a deletion that removes 101 bp of this sequence and also have several transition mutations; the comparable region has nine fewer ATGT(A/G)T repeats. These results suggest that the difference in gene expression may be due to differences in these hexamers or in other portions of the alternating purine-pyrimidine sequences, rather than in cis-acting sequences in the proximal 5' (promoter) region.
- phage M13 and λ Charon vectors
- Recombinant DNA
- restriction fragment length polymorphisms
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