The repressive function of AP2 transcription factor on the hepatocyte growth factor gene promoter.

ABSTRACT

Hepatocyte growth factor is an important multifunctional growth factor whose gene expression is tightly regulated at the transcriptional level. Previous studies from our laboratory have shown that several cis-acting elements are present in the promoter and proximal promoter region of the HGF gene. In this study, we have uncovered that AP2 transcription factor specifically binds to a regulatory site located at -230 to -260 in the upstream region of the HGF gene promoter. Gelshift and supershift assays confirmed that AP2 has high binding affinity to this region. Functional studies which introduced a mutation in the AP2 core binding region as well as cotransfection experiments using an AP2 expression vector revealed that AP2 exerts a repressive role on the HGF gene promoter activity. The AP2 binding site overlaps with those of NF1 and USF/E-box binding sites which we have recently shown to constitute a composite multifunctional docking site for the members of the NF1 and USF transcription factor families. An inverse correlation was noted between AP2 binding activity to this composite site and HGF gene expression in different cell lines. Therefore, AP2-mediated repression of the HGF gene promoter may be part of the molecular mechanism responsible for regulating HGF expression.