A dyad symmetry element in the fibroblast growth factor-2 gene promoter with different levels of activity in astrocytoma and hepatocelluar carcinoma cell lines.

Fibroblast growth factor-2 (FGF-2) gene expression is reported to be spatially and temporally regulated in the process of development, normal growth, and wound healing. We postulated that its constitutive expression in human malignant astrocytoma cells is due to loss of function of the regulatory mechanism of FGF-2 gene expression. Here, we report the characterization of a unique element in the FGF-2 gene promoter. We investigated the transcriptional regulation of the FGF-2 gene in a human malignant astrocytoma (U87MG) and a human hepatocellular carcinoma (HepG2) cell line. We found that a dyad symmetry element (DSE) in the FGF-2 gene promoter exhibited different promoter activities; in HepG2 cells it did, while in U87MG cells it did not, exhibit repressive activity. Examination of the relative promoter activities of the DSE in a thymidine kinase promoter revealed it exerted different activities, just as it did in the 2 cell lines studied. Gel shift assay demonstrated that 2 proteins bound to the DSE in nuclear extracts from HepG2 cells and that one protein was missing in nuclear extracts from U87MG cells. These results suggest that the DSE has a crucial role as a transcriptional regulatory element of FGF-2 gene expression.