Identification of a negative regulatory element in the 5'-flanking region of the human dopamine beta-hydroxylase gene.

Transient transfection experiments indicate that a 5'-flanking upstream domain, residing between -437 and -262 bp of the human dopamine beta-hydroxylase (DBH) gene, has a cell type-specific silencer function. This domain contains a putative silencer motif (which we designate DBH negative regulatory element, DNRE), showing sequence homology with the neural-restrictive silencer element (NRSE or RE-1) recently characterized in type II sodium channel, SCG10 and synapsin I genes. When the DNRE was placed at the proximal 262 bp of the homologous (DBH) promoter, it exhibited strong silencer activity both in DBH-expressing SK-N-BE(2)C as well as in DBH-nonexpressing HeLa cells. In addition, the DNRE also exhibited modest silencer activity upon a heterologous tk (herpes simplex virus thymidine kinase) promoter in both cell lines. Electrophoretic mobility shift assay demonstrated that nuclear extracts from both SK-N-BE(2)C and HeLa cells contain protein(s) that specifically bind to the DNRE. Formation of this DNRE/protein complex was specifically inhibited by an excess of unlabeled DNRE or NRSE. Finally, a similar sequence motif residing in the corresponding upstream area of the rat DBH gene also had a negative regulatory function, indicating that the silencer function of the DNRE is conserved in human and rat DBH genes.