hGH-V gene expression and promoter activity under glucose and 5-azacytidine (5azaC) effects

Abstract

The metabolic conditions affecting placental development depend on nutritional state, genetic constitution and other external factors. The secretion of human placental growth hormone (hGH-V) had shown to be dependent of glucose, but the regulatory effects of this metabolite on hGH-V promoter activity and gene expression in presence of 5-azacytidine had not been studied. In this work we compared the hGH-V promoter activity and the endogenous mRNA expression in human placental choriocarcinoma cell line JAR in the presence of glucose and demethylating genome conditions. High glucose concentration in culture medium diminished hGH-V mRNA endogenous levels in JAR cells whereas the expression of hGH-V from transfected PACs was slightly higher; but in the presence of 5azaC a higher hGH-V gene expression from both the endogenous and the transfected ones was obtained. A drastic diminution of promoter analysis was shown when cells had no glucose (J0 cells) or in presence of 5azaC; the placental transcription factors that showed modified binding capacity were HES-2, PPAR-gamma, H4TF-1 and OCT-1. Our results suggest that in vitro suppressive glucose effect dictates a metabolic context to hGH-V gene expression and promoter regulation whereas a genomic methylation-dependent background is necessary to maintain placental transcription factors able to bind and regulate proximal promoter region of hGH-V in placental cells.