Role of the transcription factor Sox-2 in the expression of the FGF-4 gene in embryonal carcinoma cells.
It has been shown previously that the FGF-4 gene is regulated by a powerful downstream enhancer in embryonal carcinoma (EC) cells. This enhancer contains an essential HMG motif; however, the transcription factor that binds to the HMG motif in EC cells has not been determined definitively. In earlier studies, this HMG motif was shown to bind a heat-stable, redox-insensitive factor expressed by F9 EC cells. Others have proposed that the transcription factor Sox-2 binds to the FGF-4 enhancer HMG motif. In this study, we demonstrate that the N-terminal half of Sox-2, which contains the DNA binding domain, binds to the FGF-4 enhancer HMG motif and we show that this binding is unaffected by heat and oxidation. In addition, we employed two experimental approaches to demonstrate that Sox-2 regulates the transcription of the FGF-4 gene in EC cells. As part of these studies, an expression plasmid that codes for a dominant-negative form of Sox-2 was used in transient expression assays. In other experiments, a Sox-2 antisense expression plasmid was used. When co-transfected into F9 EC cells along with an FGF-4 promoter/reporter gene construct, each expression plasmid caused a significant reduction in reporter activity. Our studies also demonstrate that Sox-2 affects the expression of the FGF-4 gene in the multipotent EC cell line, P19. Taken together, these studies argue strongly that Sox-2 plays an important role in the expression of the FGF-4 gene in vivo.
Johnson
L R
LR
Eppley Institute for Cancer Research and Allied Diseases, University of Nebraska Medical Center, Omaha 68198-6805, USA.
Lamb
K A
KA
Gao
Q
Q
Nowling
T K
TK
Rizzino
A
A
D000818:Animals; D018236:Carcinoma, Embryonal; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D051519:Fibroblast Growth Factor 4; D005346:Fibroblast Growth Factors / Q000235:genetics*; D005786:Gene Expression Regulation; D024002:HMGB Proteins; D051379:Mice; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000502:physiology; D055748:SOXB1 Transcription Factors; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; C496446:Fgf4 protein, mouse; D051519:Fibroblast Growth Factor 4; D024002:HMGB Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D055748:SOXB1 Transcription Factors; C527783:Sox2 protein, mouse; D014157:Transcription Factors; D005346:Fibroblast Growth Factors