Stimulation of human DBH gene expression by prostaglandin E-2 in human neuroblastoma SK-N-BE(2)C cells

Abstract

Prostaglandin E-2 (PGE(2)) enhances transcription of the human dopamine P-hydroxylase (DBH) gene in human neuroblastoma SK-N-BE(2)C cells. To identify a PGE(2)-responsive cis-acting element in the human DBH gene, serial deletion constructs of the human DBH 5'-upstream region fused to the chloramphenicol acetyltransferase (CAT) reporter gene were transiently transfected into SK-N-BE(2)C cells. Treatment of the transformed cells with PGE(2) increased CAT expression two-to threefold in all constructs except where the promoter region was shortened beyond position -114 bp. There are several cis-regulatory elements in the region between -262 and -114 bp from the transcription initiation site that include a cyclic AMP response element (CRE) and a putative AP1 sequence. We presupposed that the CRE and AP1 might be candidates for PGE(2) stimulation, and therefore, used site-directed mutagenesis to change the CRE and AP1 motives and test which of the two elements mediated the transcriptional enhancement. Only a specific mutation within the CRE sequence abolished the PGE(2) effect. In addition, cotransfection with an expression vector expressing PKA inhibitor resulted in the specific blockage of the PGE(2) effect on DBH gene expression. Northern blot analysis revealed that the increase in DBH gene transcription caused by PGE(2) results in elevated DBH mRNA levels. Gel-retardation and competition assays confirmed that the binding of nuclear factors to the CRE site is sequence specific. Our data, therefore, indicate that PGE(2) enhances the transcription of the human DBH gene. The effect is mediated by the CRE motif through activation of PKA.