Article

Estrogen receptor alpha represses transcription of early target genes via p300 and CtBP1.

Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801-3704, USA.
Molecular and Cellular Biology (Impact Factor: 5.04). 03/2009; 29(7):1749-59. DOI: 10.1128/MCB.01476-08
Source: PubMed

ABSTRACT The regulation of gene expression by nuclear receptors controls the phenotypic properties and diverse biologies of target cells. In breast cancer cells, estrogen receptor alpha (ERalpha) is a master regulator of transcriptional stimulation and repression, yet the mechanisms by which agonist-bound ERalpha elicits repression are poorly understood. We analyzed early estrogen-repressed genes and found that ERalpha is recruited to ERalpha binding sites of these genes, albeit more transiently and less efficiently than for estrogen-stimulated genes. Of multiple cofactors studied, only p300 was recruited to ERalpha binding sites of repressed genes, and its knockdown prevented estrogen-mediated gene repression. Because p300 is involved in transcription initiation, we tested whether ERalpha might be trying to stimulate transcription at repressed genes, with ultimately failure and a shift to a repressive program. We found that estrogen increases transcription in a rapid but transient manner at early estrogen-repressed genes but that this is followed by recruitment of the corepressor CtBP1, a p300-interacting partner that plays an essential role in the repressive process. Thus, at early estrogen-repressed genes, ERalpha initiates transient stimulation of transcription but fails to maintain the transcriptional process observed at estrogen-stimulated genes; rather, it uses p300 to recruit CtBP1-containing complexes, eliciting chromatin modifications that lead to transcriptional repression.

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    • "The biological function of estrogen is largely mediated by ER, which is primarily associated with ductal elongation rather than lobuloalveolar formation in the mammary gland [45], [46]. Early and complete loss of ER in mammary epithelia prevents the formation of TEBs and severely impairs ductal elongation [47], [48]. "
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    • "In turn, the co-activator complex remodels the chromatin at this region through histone acetylation, facilitating RNA polymerase II-mediated transcription (Onate et al. 1995; Anzick et al. 1997; Torchia et al. 1997; Chen et al. 1999a, b). It has also been established that, in estrogenrepressed genes, estrogen–ER stimulates the selective association of co-repressors (Carroll et al. 2006; Stossi et al. 2009). "
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    • "p300 also plays roles in the regulation of CYP19 I.3/II (aromatase), the key enzyme in estrogen biosynthesis and an important target in breast cancer (Subbaramaiah et al., 2008). Fig. 4. Proposed model for ERα-mediated activation or repression of target genes via p300 (Stossi et al., 2009). "
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