Identification and Characterization of a Novel Phorbol Ester- responsive DNA Sequence in the 5*-Flanking Region of the Human Dopamine b-Hydroxylase Gene*

The phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA), enhances transcription of many eukaryotic genes, including that for dopamine b-hydroxylase (DBH). In the present study, we report identification and characterization of a novel sequence motif residing in the 5*-flanking region of the human DBH gene, which mediates transcriptional induction by TPA. Deletional analyses indicated the promoter region between 2223 and 2187 base pairs to be critical. Whereas this region does not contain any putative regulatory motifs with significant sequence homology to the AP-1 motif, extensive deletional and site-directed mutational analyses indicated that a sequence between 2210 and 2199 base pairs, 5*-ATCCGCCTGTCT-3*, may represent a novel TPA-response element (TRE). In addition, alteration of the YY1-binding site decreased TPA-mediated induction of the DBH promoter activity, suggesting that contiguous cis-regulatory element(s) cooperate with this novel sequence motif. Furthermore, insertional mutation analyses between the YY1-binding site and the cyclic AMP-responsive element indicated that the stereospecificity of these motifs is important for intact transcriptional induction by TPA. Taken together, these data suggest that transcriptional up-regulation of the human DBH gene in response to TPA requires coordination of a novel TRE (human DBH TRE, hDTRE), cyclic AMP-responsive element, and the YY1-binding site.