Human Chorionic Gonadotropin-α Gene Is Transcriptionally Activated by Epidermal Growth Factor through cAMP Response Element in Trophoblast Cells

Abstract The purpose of this study was to analyze the mechanism of transcriptional activation of human chorionic gonadotropin-α (hCGα) gene by epidermal growth factor (EGF) in trophoblast cells. We stably transfected hCGα promoter-chloramphenicol acetyltransferase constructs into Rcho-1 trophoblast cells and monitored the promoter activities. −290-base pair hCGα promoter containing a tandem repeat of cAMP response element (CRE) was activated by EGF in a dose- and time-dependent manner. Deletion analysis of hCGα promoter suggested an involvement of CRE in EGF-induced hCGα transcriptional activation. Moreover, the hCGα promoter, of which both CREs were mutated, did not respond to EGF. These results indicate that EGF activates the hCGα gene transcription through CRE. Although EGF did not alter the amount of CRE-binding protein (CREB), EGF induced CREB phosphorylation. We next examined the mechanism of CREB phosphorylation by EGF. Protein kinase C inhibitors (H7, staurosporin, and chelerythrine) inhibited EGF-induced CREB phosphorylation, whereas either mitogen-activated protein kinase kinase-1 inhibitor (PD98059) or protein kinase A inhibitor (H8) showed no effect. Furthermore, H7 and staurosporin but not H8 inhibited hCGα promoter activation by EGF. In conclusion, EGF promotes hCGα gene transcription via the CRE region probably by phosphorylating CREB mainly through the protein kinase C pathway in trophoblast cells.