Sequences Distal to the AP1/E Box Motif Are Involved in the Cell Type‐Specific Expression of the Rat Tyrosine Hydroxylase Gene

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Abstract
In order to define cell type‐specific elements associated with the catecholamine biosynthetic enzyme, tyrosine hydroxylase (TH), transient transfections of promoter deletion constructs were used to test relative reporter‐gene activities in TH‐expressing and‐nonexpressing cell lines. Such assays demonstrated that a region between‐503 and‐578 contributed to rat TH promoter activity in the pheochromocytoma cell line PC12. Deletion of these sequences resulted in a 66% loss in cell type‐specific activity. Mutations within the E box/dyad symmetry element (CAGGTGCCTGTGACAGTG) did not affect the basal and cell type‐specific pattern of expression exhibited by the rat TH promoter. Promoter fusion constructs between the rat TH promoter (‐741 and‐197) and the human TH promoter (‐197 and +1) exhibited reporter‐gene activities equivalent to that of wild‐type‐741 rat TH constructs, further demonstrating that sequence elements upstream of the rat E box/dyad symmetry are important for cell type‐specific expression. Gel‐shift experiments indicated that a PC12 nuclear factor could bind to a 39‐bp sequence within this region in a cell type‐specific manner. The size of this factor was 52 kDa as determined by UV cross‐linking experiments.