Two independent pathways for transcription from the MMTV promoter.
The influence of progesterone receptor (PR) and glucocorticoid receptor (GR) on transcription from the mouse mammary tumour virus (MMTV) promoter was analyzed using cell-free transcription of DNA templates with a G-free cassette. Preincubation of the templates with either PR or GR stimulates the rate of transcription initiation 10-50 fold, whereas the recombinant DNA binding domain of GR is inactive. Mutations that inactivate the nuclear factor I (NFI) binding site, or NFI depletion of the nuclear extract, decrease basal transcription without influencing receptor-dependent induction. Recombinant NFI, but not its DNA-binding domain, restores efficient basal transcription of the depleted extract. Recombinant OTF1 or OTF2, but not the POU domain of OTF1, enhance MMTV transcription independently of NF1. In agreement with this finding, NFI and OTF1 do not cooperate, but rather compete for binding to the wild type MMTV promoter, though they have the potential to bind simultaneously to properly oriented sites. Our results imply the existence of two independent pathways for MMTV transcription: one initiated by NFI and the other dependent on octamer transcription factors. Only the second pathway is stimulated by steroid hormone receptors in vitro.
Möws
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Institut für Molekularbiologie und Tumorforschung (IMT), Phillips Universität, Marburg, Germany.
Preiss
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Slater
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Cao
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Verrijzer
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van Der Vliet
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Beato
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D001483:Base Sequence; D001665:Binding Sites; D022762:CCAAT-Enhancer-Binding Proteins; D002457:Cell Extracts / Q000494:pharmacology; D002474:Cell-Free System; D004268:DNA-Binding Proteins / Q000494:pharmacology; D006367:HeLa Cells; D051863:Host Cell Factor C1; D006801:Humans; D008324:Mammary Tumor Virus, Mouse / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation / Q000502:physiology; D051839:NFI Transcription Factors; D009687:Nuclear Proteins; D050811:Octamer Transcription Factor-1; D010957:Plasmids / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011965:Receptors, Glucocorticoid / Q000378:metabolism*; D011980:Receptors, Progesterone / Q000378:metabolism*; D011994:Recombinant Proteins / Q000494:pharmacology; D014157:Transcription Factors / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects; D051840:Y-Box-Binding Protein 1
D022762:CCAAT-Enhancer-Binding Proteins; D002457:Cell Extracts; D004268:DNA-Binding Proteins; C497692:HCFC1 protein, human; D051863:Host Cell Factor C1; D051839:NFI Transcription Factors; D009687:Nuclear Proteins; D050811:Octamer Transcription Factor-1; C494165:POU2F1 protein, human; D011965:Receptors, Glucocorticoid; D011980:Receptors, Progesterone; D011994:Recombinant Proteins; D014157:Transcription Factors; D051840:Y-Box-Binding Protein 1; C070856:YBX1 protein, human