Transcriptional activation of fibroblast growth factor 1.B promoter is mediated through an 18-base pair cis-acting element.
Four different transcripts encoding fibroblast growth factor 1 (FGF-1, also known as aFGF) have been previously identified in our laboratory. Among them, FGF-1.B is the major transcript expressed specifically in the neuronal cells in brain tissue. Using the transient transfection experiment in a glioblastoma cell line, U1240MG, that expresses 1.B, we previously identified two regulatory regions (RR1 and RR2) in the brain-specific promoter, FGF-1.B. In the present study, we showed that the minimal region required for the DNA-protein interaction in RR2 resides in an 18-base pair (-484 to -467) sequence, by using DNase I footprinting and methylation interference studies and electrophoretic mobility shift assays. This minimal cis-acting element was found to be sufficient in enhancing the reporter activity driven by the heterologous herpes simplex virus thymidine kinase promoter in the 1.B-positive U1240MG cell line. This enhancing effect, however, was not detected in a glioblastoma cell line, U1242MG, which is negative for 1.B expression. By electrophoretic mobility shift assays, we also identified a specific DNA-protein complex, namely complex I, which is specific for 1.B-positive cell lines and human brain tissue. By in situ UV cross-linking experiment, we further showed that complex I contains two major DNA-binding proteins of apparent molecular masses of 37 and 98 kDa. Our results suggest that the formation of complex I, resulting from the heterodimerization of a 37-kDa protein (1.B-specific) and a 98-kDa protein (ubiquitous) may likely be a prerequisite for the enhanced expression of 1.B transcript in neuronal cells.
Ray
S K
SK
Department of Internal Medicine and Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio 43210, USA.
Yang
X Q
XQ
Chiu
I M
IM
D004247:DNA / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics; D016220:Fibroblast Growth Factor 1 / Q000235:genetics*; D005909:Glioblastoma; D006801:Humans; D011401:Promoter Regions, Genetic / Q000235:genetics*; D017422:Sequence Analysis, DNA; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; D016220:Fibroblast Growth Factor 1; D004247:DNA