A 66-base-pair enhancer module activates the expression of a distinct isoform of UDP-glucuronosyltransferase family 1 (UGT1A2) in primary hepatocytes

UGT1A2, an isoform of the UDP-glucuronosyltransferase family 1 (UGT1), is n ot expressed in the rat liver, but its expression was highly induced in pri mary cultures of rat hepatocytes, In primary hepatocytes that had been cult ured for 70 h, the amount of UGT1A2 mRNA was 100 times higher than that in the rat liver. Deletion analysis of a 4.8-kb promoter region of the UGT1A2 gene revealed that a 66-nucleotide region between -307 and -242 upstream of the transcription start site was required for induction of UGT1A2 expressi on. The 66-nucleotide region acted on a heterologous promoter in a manner i ndependent of its position and orientation in reporter constructs. Gel mobi lity shift assay showed that a specific binding protein to this region appe ared in the nuclei of cultured hepatocytes, but was not present in the rat liver. DNase I protection analysis revealed the existence of a CTG-GCAC cor e sequence between -274 and -268 of the UGT1A2 promoter. Methylation interf erence assay showed that the guanine residues at -294 and -287 on the upper strand and the guanine residue at -267 on the lower strand as well as the core sequence were required for the DNA-protein interaction. These results suggest that the 66-nucleotide region, which was designated culture-associa ted expression responsive enhancer module (CEREM), interacts with a specifi c nuclear protein and enhances the expression of UGT1A2 in cultured hepatoc ytes. (C) 2000 Academic Press.