Distal enhancer of the mouse FGF-4 gene and its human counterpart exhibit differential activity: critical role of a GT box.
Previous studies have shown that there is a strict requirement for fibroblast growth factor-4 (FGF-4) during mammalian embryogenesis, and that FGF-4 expression in embryonic stem (ES) cells and embryonal carcinoma (EC) cells are controlled by a powerful downstream distal enhancer. More recently, mouse ES cells were shown to express significantly more FGF-4 mRNA than human ES cells. In the work reported here, we demonstrate that mouse EC cells also express far more FGF-4 mRNA than human EC cells. Using a panel of FGF-4 promoter/reporter gene constructs, we demonstrate that the enhancer of the mouse FGF-4 gene is approximately tenfold more active than its human counterpart. Moreover, we demonstrate that the critical difference between the mouse and the human FGF-4 enhancer is a 4 bp difference in the sequence of an essential GT box. Importantly, we demonstrate that changing 4 bp in the human enhancer to match the sequence of the mouse GT box elevates the activity of the human FGF-4 enhancer to the same level as that of the mouse enhancer. We extended these studies by examining the roles of Sp1 and Sp3 in FGF-4 expression. Although we demonstrate that Sp3, but not Sp1, can activate the FGF-4 promoter when artificially tethered to the FGF-4 enhancer, we show that Sp3 is not essential for expression of FGF-4 mRNA in mouse ES cells. Finally, our studies with human EC cells suggest that the factor responsible for mediating the effect of the mouse GT box is unlikely to be Sp1 or Sp3, and this factor is either not expressed in human EC cells or it is not sufficiently active in these cells.
Boer
Brian
B
Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-6805, USA.
Luster
Troy A
TA
Bernadt
Cory
C
Rizzino
Angie
A
D000818:Animals; D004268:DNA-Binding Proteins / Q000378:metabolism; D004622:Embryo, Mammalian / Q000166:cytology / Q000502:physiology*; D054278:Embryonal Carcinoma Stem Cells; D004742:Enhancer Elements, Genetic / Q000235:genetics / Q000502:physiology*; D051519:Fibroblast Growth Factor 4; D005346:Fibroblast Growth Factors / Q000096:biosynthesis* / Q000235:genetics; D018507:Gene Expression Regulation, Developmental / Q000235:genetics / Q000502:physiology*; D006801:Humans; D051379:Mice; D014411:Neoplastic Stem Cells / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis* / Q000235:genetics; D016329:Sp1 Transcription Factor / Q000378:metabolism; D051705:Sp3 Transcription Factor; D013234:Stem Cells / Q000166:cytology / Q000502:physiology*; D014157:Transcription Factors / Q000378:metabolism; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; C496445:FGF4 protein, human; C496446:Fgf4 protein, mouse; D051519:Fibroblast Growth Factor 4; D011518:Proto-Oncogene Proteins; C497121:SP3 protein, human; D016329:Sp1 Transcription Factor; C497122:Sp3 protein, mouse; D014157:Transcription Factors; D051705:Sp3 Transcription Factor; D005346:Fibroblast Growth Factors