title: Differential recruitment of nuclear receptor coregulators in ligand-dependent transcriptional repression by estrogen receptor-α.
abstract: Estrogen receptors (ERs) are normally expressed in breast tissues and mediate hormonal functions during development and in female reproductive physiology. In the majority of breast cancers, ERs are involved in regulating tumor cell proliferation and serve as prognostic markers and therapeutic targets in the management of hormone-dependent tumors. At the molecular level, ERs function as ligand-dependent transcription factors and activate target-gene expression following hormone stimulation. Recent transcriptomic and whole-genome-binding studies suggest, however, that ligand-activated ERs can also repress the expression of a significant subset of target genes. To characterize the molecular mechanisms of transcriptional repression by ERs, we examined recruitment of nuclear receptor coregulators, histone modifications and RNA polymerase II docking at ER-binding sites and cis-regulatory regions adjacent to repressed target genes. Moreover, we utilized gene expression data from patient samples to determine potential roles of repressed target genes in breast cancer biology. Results from these studies indicate that nuclear receptor corepressor recruitment is a key feature of ligand-dependent transcriptional repression by Ers, and some repressed target genes are associated with disease progression and response to endocrine therapy. These findings provide preliminary insights into a novel aspect of the molecular mechanisms of ER functions and their potential roles in hormonal carcinogenesis and breast cancer biology.
authors.affiliation: Department of Microbiology and Molecular Biology, Brigham Young University, Provo, UT 84602, USA.
authors.forename: K W
authors.initials: KW
authors.lastname: Merrell
authors.forename: J D
authors.initials: JD
authors.lastname: Crofts
authors.forename: R L
authors.initials: RL
authors.lastname: Smith
authors.forename: J H
authors.initials: JH
authors.lastname: Sin
authors.forename: K E
authors.initials: KE
authors.lastname: Kmetzsch
authors.forename: A
authors.initials: A
authors.lastname: Merrell
authors.forename: R O
authors.initials: RO
authors.lastname: Miguel
authors.forename: N R
authors.initials: NR
authors.lastname: Candelaria
authors.forename: C-Y
authors.initials: CY
authors.lastname: Lin
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000502:physiology; D056970:Co-Repressor Proteins; D047628:Estrogen Receptor alpha / Q000502:physiology*; D004967:Estrogens / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008024:Ligands; D009687:Nuclear Proteins / Q000502:physiology; D056971:Nuclear Receptor Co-Repressor 1 / Q000502:physiology; D056985:Nuclear Receptor Co-Repressor 2 / Q000502:physiology; D000078723:Nuclear Receptor Interacting Protein 1; D012097:Repressor Proteins / Q000502:physiology*; D020218:Response Elements / Q000502:physiology; D014158:Transcription, Genetic
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D056970:Co-Repressor Proteins; C506487:ESR1 protein, human; D047628:Estrogen Receptor alpha; D004967:Estrogens; D008024:Ligands; C539127:NCOR1 protein, human; C539130:NCOR2 protein, human; D009687:Nuclear Proteins; D056971:Nuclear Receptor Co-Repressor 1; D056985:Nuclear Receptor Co-Repressor 2; D000078723:Nuclear Receptor Interacting Protein 1; D012097:Repressor Proteins