title: Chromatin-dependent cooperativity between site-specific transcription factors in vivo.
abstract: Accessing binding sites in DNA wrapped around histones in condensed chromatin is an obstacle that transcription factors must overcome to regulate gene expression. Here we demonstrate cooperativity between two transcription factors, the glucocorticoid receptor (GR) and nuclear factor 1 (NF1) to bind the mouse mammary tumor virus promoter organized as regular chromatin in vivo. This cooperativity is not observed when the promoter is introduced transiently into cells. Using RNA interference to deplete NF1 protein levels in the cells, we confirmed that NF1 promotes binding of GR to the promoter. Furthermore, we observed a similar synergism between GR and NF1 binding on the endogenous 11beta-hydroxysteroid dehydrogenase promoter, also regulated by GR and NF1. Our results suggest that the chromatin architecture of the promoters does not permit strong association of GR in the absence of NF1. Therefore we propose that cooperativity among DNA binding factors in binding to their cognate recognition sites in chromatin may be an important feature in the regulation of gene expression.
authors.affiliation: Laboratory of Molecular Carcinogenesis, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA.
authors.forename: Pratibha B
authors.initials: PB
authors.lastname: Hebbar
authors.forename: Trevor K
authors.initials: TK
authors.lastname: Archer
mesh_terms: D000818:Animals; D001665:Binding Sites; D002843:Chromatin / Q000378:metabolism*; D047369:Chromatin Immunoprecipitation; D005786:Gene Expression Regulation; D006801:Humans; D051379:Mice; D008954:Models, Biological; D051839:NFI Transcription Factors / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D020033:Protein Isoforms; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D011965:Receptors, Glucocorticoid / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection
chemical_list: D002843:Chromatin; D051839:NFI Transcription Factors; D020033:Protein Isoforms; D034741:RNA, Small Interfering; D011965:Receptors, Glucocorticoid; D014157:Transcription Factors