The AP-1 site and the cAMP- and serum response elements of the c-fos gene are constitutively occupied in vivo.
The c-fos proto-oncogene is inducible by cAMP, phorbol esters, serum, and growth factors. The induction by cAMP is mediated by the conserved cAMP response element (CRE), while induction by phorbol esters, serum, and growth factors requires a distal element called the serum response element (SRE). In addition to these elements, a consensus AP-1 transcription factor binding site is located next to SRE. Upstream regions of the mouse and human c-fos genes were footprinted in vivo by the ligation-mediated polymerase chain (PCR). Our results show that all three elements are constitutively protected in mouse liver and lung and in cultured human A431 cells. No major change in the protection profile was detected in A431 cells following stimulation with epidermal growth factor or in mice at birth, when c-fos is known to be induced. These results suggest that the inducible cis elements of the c-fos gene are poised, ready to respond immediately to external signals.
Dey
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A
Laboratory of Developmental and Molecular Immunity, National Institute of Child Health and Human Development, Bethesda, MD 20892.
Nebert
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DW
Ozato
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D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins / Q000235:genetics*; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics*; D000090063:Proto-Oncogene Mas; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics*; D011519:Proto-Oncogenes; D012045:Regulatory Sequences, Nucleic Acid; D012091:Repetitive Sequences, Nucleic Acid; D026362:Serum Response Factor; D014157:Transcription Factors / Q000235:genetics
D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; C000715470:MAS1 protein, human; D009687:Nuclear Proteins; D000090063:Proto-Oncogene Mas; D016755:Proto-Oncogene Proteins c-jun; D026362:Serum Response Factor; D014157:Transcription Factors