FUNCTION OF CIS-ACTING ELEMENTS IN HUMAN ALCOHOL-DEHYDROGENASE-4 (ADH4) PROMOTER AND ROLE OF C EBP PROTEINS IN GENE-EXPRESSION/

The ADH4 gene, which encodes human pi-alcohol dehydrogenase, is expres sed in a tissue-specific manner, with the highest level in liver and l ower levels in the gastrointestinal tract. We examined the location an d function of the cis-acting elements that regulate ADH4 transcription . Liver contains proteins that bound to seven sites in the proximal pr omoter (from bp -387 to bp +17). Proteins from other tissues bound to subsets of these sites and to two additional sites, one of which is a negative cis-acting element. Members of two important transcription fa ctor families, C/EBP and AP-1, bound to several sites in this promoter . The proximal ADH4 promoter functioned in a hepatoma cell line (H4IIE -C3) and a kidney cell line (CV-1). Coexpression of members of the C/E BP family strongly enhanced promoter activity, which can in part expla in the high level of expression of ADH4 in liver. At one site that can be bound by both C/EBP and c-Jun, a mutation that abolished binding b y C/EBP but not by c-Jun decreased promoter activity in both cell line s. This mutation had a stronger effect in the context of a longer prom oter, suggesting interaction among cis-acting elements.