An E2F binding sequence negatively regulates the response of the insulin-like growth factor 1 (IGF-I) promoter to simian virus 40T antigen and to serum.
The promoter of the Insulin-like growth factor I (IGF-I) gene is activated by the Simian Virus 40 large T antigen (SVLT), and one of the elements responding to SVLT activation has been localized to a short 124 bp immediately upstream of the first initiation of transcription site. This short promoter contains an E2F binding site, that, in gel shifts, binds a protein complex, but only when the promoter activity is reduced or absent. A mutation in the E2F binding site deregulates the activity of the promoter, which becomes active even in those conditions in which the wild type promoter is inactive. By using antibodies in gel retardation analyses, we can show that the different protein complexes include, at least, the following proteins: E2F, cyclin A and p107. We conclude that the short IGF-I promoter is negatively regulated by an E2F binding site that complexes with several proteins. Our data suggest that disaggregation of these complexes by the action of SVLT (or other activators) increases expression from the promoter, thus establishing a link between the regulation of cell proliferation by growth factors and the E2F-associated proteins.
Jefferson Cancer Institute, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.
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Porcu
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Graña
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Li
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Swantek
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De Luca
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Giordano
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Baserga
D016475:3T3 Cells; D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000502:physiology*; D001483:Base Sequence; D001665:Binding Sites; D001790:Blood Physiological Phenomena; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004247:DNA / Q000096:biosynthesis; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D008156:Luciferases / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D056465:Retinoblastoma-Binding Protein 1; D013539:Simian virus 40 / Q000276:immunology*; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic
D000952:Antigens, Polyomavirus Transforming; C533431:Arid4a protein, mouse; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors; D007334:Insulin-Like Growth Factor I; D004247:DNA; D008156:Luciferases