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XB-ART-40203
Mol Cell Biol 2009 Oct 01;2920:5413-25. doi: 10.1128/MCB.00368-09.
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FoxA1 binding directs chromatin structure and the functional response of a glucocorticoid receptor-regulated promoter.

Belikov S , Astrand C , Wrange O .


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Reconstitution of the glucocorticoid receptor (GR)-regulated mouse mammary tumor virus (MMTV) promoter in Xenopus oocytes was used to monitor the effects of different transcription factor contexts. Three constitutively binding factors, nuclear factor 1 (NF1), octamer transcription factor 1 (Oct1), and the Forkhead box A1 (FoxA1), were shown to act in concert, to direct the chromatin structure, and to enhance the GR response. FoxA1 has a dominant effect in the absence of hormone and induces a cluster of DNase I-hypersensitive sites in the segment comprising bp -400 to +25. This FoxA1-mediated chromatin remodeling does not induce MMTV transcription, as opposed to that of the GR. However, the robust FoxA1-dependent chromatin opening has the following drastic functional consequences on the hormone regulation: (i) GR-DNA binding is facilitated, as revealed by dimethyl sulfate in vivo footprinting, leading to increased hormone-induced transcription, and (ii) the GR antagonist RU486 is converted into a partial agonist in the presence of FoxA1 via ligand-independent GR activation. We conclude that FoxA1 mediates a preset chromatin structure and directs a context-specific response of a nuclear receptor. Furthermore, the alternative nucleosome arrangement induced by GR and FoxA1 implies this to be determined by constitutive binding of transcription factors rather than by the DNA sequence itself.

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Species referenced: Xenopus laevis
Genes referenced: foxa1 nf1 nr3c1 pou2f1

References [+] :
Astrand, Histone acetylation characterizes chromatin presetting by NF1 and Oct1 and enhances glucocorticoid receptor binding to the MMTV promoter. 2009, Pubmed, Xenbase