Regulation of PGF gene expression by GCM1 and MTF1

Abstract

PGF is a member of VEGF family. PGF is highly expressed in placenta during normal pregnancy. Previous study showed that it plays a pivotal role for vasculogenesis and angiogenesis in endothelial cells via paracrine action. In addition, PGF is also expressed during early embryonic development and control early embryogenesis. The placenta-specific transcription factor GCM1 is critical for placental cell differentiation. We have recently identified PGF as a GCM1 target gene by ChIP-chip analysis. Although GCM1 has been showed to regulate PGF expression transcriptionally, the mechanism of PGF expression is still not clear. Other study demonstrate that MTF1 takes part in the induction of PGF expression in Bewo cell, the trophoblast-derived choriocarcinoma cell line. MTF1 is a transcription factor that responds to a variety of stresses including metal load, hypoxia and oxidative stress. Here, we also investigated whether MTF1 is involved in PGF expression. We demonstrated that the PGF mRNA and protein levels are significantly decreased in GCM1-knockdown and hypoxia Bewo cells. Conversely, the results were increased in GCM1-overexpressed JAR cells. Furthermore, GCM1 stimulated the PGF promoter activity by luciferase reporter construct harboring the PGF promoter region from -1000 to -345 and +5 to +100 relative to the transcriptional start site. By site-directed mutagenesis, we further identified a GCM1-binding site that is essential for GCM1 to upregulate PGF promoter activity. On the other hand, the PGF mRNA level was slightly decreased on MTF1 -knockdown and hypoxia condition. But we failed to observe that MTF1 regulate PGF promoter activity. Based on the above results, we get the following inference in this paper. In placental cells, it may mainly bind to PGF promoter 5’ UTR region and turn on PGF gene by GCM1 transcription factor. In the non-placental cells, MTF1 may transcriptionally regulate PGF gene.