TISSUE-SPECIFIC DIFFERENCES IN THE EXPRESSION OF THE HUMAN ADH2 ALCOHOL-DEHYDROGENASE GENE AND IN BINDING OF FACTORS TO CIS-ACTING ELEMENTSIN ITS PROMOTER

The human alcohol dehydrogenase gene ADH2 is expressed at high levels in liver, at lower levels in kidney and several other tissues, and is not expressed in other tissues such as spleen. This pattern of express ion suggests a complex regulatory region that responds to a variety of transcription factors in different cellular contexts. Seven cis-actin g sequences in the proximal 271 bp of the ADH2 promoter were mapped. T he occupancy of these sites differed markedly among extracts from live r, kidney, spleen, H4IIE-C3 cells, HeLa cells, and CV-1 cells. These d ifferences in occupancy were accompanied by differences in gene expres sion in the three cell lines. The ADH2 promoter directed substantial C AT expression in H4IIE-C3 cells (rat hepatoma) and in HeLa cells, but only minimal expression in CV-1 cells (monkey kidney fibroblasts). The three cell lines differed in the effects of deletions within the prom oter. An ADH2 promoter that contained both the USF/MLTF site and the G 3T site gave four- to eight-fold higher expression in both H4IIE-C3 an d HeLa cells than a smaller promoter that lacked these sites; in contr ast, these sequences did not significantly stimulate transcription in CV-1 cells. A CTF/NF-I-related site acted as a negative element in all three cell lines. Coexpression of C/EBP alpha altered the cell specif icity. The ADH2 promoter was moderately stimulated (twofold) by coexpr ession of C/EBP alpha in H4IIE-C3 cells, but markedly stimulated in He La cells and in CV-1 cells (11- and 20-fold, respectively). These resu lts demonstrate the differential importance of cis-acting sequences an d of specific transcription factors in different cells, which allows r egulated expression of ADH2 in multiple tissues.