Location of the Repressor Site of Rat Hepatic Hydroxysteroid Sulfotransferase (SULT2-40/41)
Ebenhoe, Emily L.
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Understanding the molecular mechanisms that regulate the expression of the rat hepatic hydroxysteroid sulfotransferase gene (SULT2-40/41) is important in understanding its role in drug metabolism, carcinogen activation, bile acid detoxification and regulation of intra-tissue active hormone levels. Glucocorticoids have been shown to induce SULT2-40/41 gene transcription. A recent study of the activating region has pointed to an inhibiting region in the ~2000 bp 5' upstream promoting region of this gene. The location of this inhibiting region was investigated by making several deletion constructs of a previously made construct not containing the activating site (-227/-158). The promoter region constructs ligated into luciferase reporter vectors were transiently transfected into primary rat hepatocytes. Treatment with a synthetic glucocorticoid, dexamethasone, induced gene transcription in all of the constructs. However, the smallest construct, beginning 158 bp upstream (-158) from the transcription start site, continued to have significantly higher SULT2-40/41 gene expression than any of the other constructs. This implies that the repressor site is located within the next smallest DNA construct, -268 from the transcription start site. Since this region does not contain the -227/-158 activating region, the inhibiting region is therefore located in the -268/-227 region. This region has previously been studied in relation to androgen responsiveness, and it is already known that there are three protein binding sites within this -268 5'-flanking region. With further study, it is likely that one of these three sites can be implicated as the site that regulates the inhibition of SULT2-40/41 gene expression.