Chromatin-mediated restriction of nuclear factor 1/CTF binding in a repressed and hormone-activated promoter in vivo.
Mouse mammary tumor virus (MMTV) promoter-driven transcription is induced by glucocorticoid hormone via binding of the glucocorticoid receptor (GR). The MMTV promoter also harbors a binding site for nuclear factor 1 (NF1). NF1 and GR were expressed in Xenopus oocytes; this revealed GR-NF1 cooperativity both in terms of DNA binding and chromatin remodeling but not transcription. A fraction of NF1 sites were occupied in a hormone-dependent fashion, but a significant and NF1 concentration-dependent fraction were constitutively bound. Activation of the MMTV promoter resulted in an approximately 50-fold increase in the NF1 accessibility for its DNA site. The hormone-dependent component of NF1 binding was dissociated by addition of a GR antagonist; however, the antagonist RU486, which supports partial GR-DNA binding, also maintained partial NF1 binding. Hence GR-NF1 cooperativity is independent of agonist-driven chromatin remodeling. NF1 induced the formation of a micrococcal-nuclease-resistant protein-DNA complex containing the DNA segment from -185 to -55, the MMTV enhanceosome. Coexpression of NF1 and Oct1 resulted in a significant stimulation of hormone-induced MMTV transcription and also in increased basal transcription. We propose that hormone-independent NF1 binding may be involved in maintaining transcriptional competence and establishment of tissue-specific gene networks.
Belikov
Sergey
S
Department of Cell and Molecular Biology, The Medical Nobel Institute, Karolinska Institutet, SE-17177 Stockholm, Sweden.
Astrand
Carolina
C
Holmqvist
Per-Henrik
PH
Wrange
Orjan
O
D000818:Animals; D001483:Base Sequence; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism*; D002843:Chromatin / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005938:Glucocorticoids / Q000378:metabolism*; D051863:Host Cell Factor C1; D006801:Humans; D008324:Mammary Tumor Virus, Mouse / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D051839:NFI Transcription Factors; D009690:Nucleic Acid Conformation; D050811:Octamer Transcription Factor-1; D009865:Oocytes / Q000502:physiology; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011965:Receptors, Glucocorticoid / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D029867:Xenopus Proteins; D014982:Xenopus laevis
D022762:CCAAT-Enhancer-Binding Proteins; C077305:CTF-1 transcription factor; D002843:Chromatin; D004268:DNA-Binding Proteins; D005938:Glucocorticoids; C497692:HCFC1 protein, human; C497693:Hcfc1 protein, mouse; D051863:Host Cell Factor C1; D051839:NFI Transcription Factors; C497647:NFIC protein, human; C497648:Nfic protein, mouse; D050811:Octamer Transcription Factor-1; C494169:POU2F1 protein, Xenopus; C494165:POU2F1 protein, human; C494166:Pou2f1 protein, mouse; D011965:Receptors, Glucocorticoid; D014157:Transcription Factors; D029867:Xenopus Proteins