Glucocorticoid receptor activates poised FKBP51 locus through long-distance interactions.
ABSTRACT Recent studies have identified FKBP51 (FK506-binding protein 51) as a sensitive biomarker of corticosteroid responsiveness in vivo. In this work, we have elucidated the molecular mechanisms underlying the induction of FKBP51 by the glucocorticoid receptor (GR) in human A549 lung cancer cells showing robust accumulation of FKBP51 mRNA in response to dexamethasone exposure. Our quantitative chromatin immunoprecipitation scans and enhancer activity analyses indicate that activation of the FKBP51 locus by glucocorticoids in vivo is triggered by the loading of GR to enhancers at about 34 kb 5' and about 87 kb 3' of the transcription start site. Interestingly, the region encompassing these enhancers is bordered by CCCTC-binding factor- and cohesin-binding sites. Dexamethasone treatment also decreased the histone density at several regions of the gene, which was paralleled with the occupancy of SWI/SNF chromatin remodeling complexes within the locus. Moreover, silencing of BRM subunit of the SWI/SNF complex blunted the glucocorticoid induction of the locus. The proximal promoter region along with the major intronic enhancer at approximately 87 kb, at which the GR binding peaked, had elevated levels of histone 3 acetylation and H3K4 trimethylation, whereas H3K36 trimethylation more generally marked the gene body and reflected the occupancy of RNA polymerase II. The occurrence of these active chromatin marks within the FKBP51 locus before glucocorticoid exposure suggests that it is poised for transcription in A549 cells. Taken together, these results indicate that the holo-GR is capable of activating transcription and evoking changes in chromatin structure through distant-acting enhancers.
- SourceAvailable from: Kellie L Tamashiro[show abstract] [hide abstract]
ABSTRACT: Glucocorticoids may play a significant role in the etiology of neuropsychiatric illnesses. Abnormalities in plasma cortisol levels, glucocorticoid sensitivity, and HPA-axis function often accompany clinical symptoms of stress-related illnesses such as PTSD and depression. Of particular interest are genetic association studies that link single nucleotide polymorphisms of HPA-axis genes with illnesses only in the context of an early-life trauma exposure such as child abuse. These studies suggest that dysregulation of HPA-axis function can have lasting repercussions in shaping mood and anxiety, long after termination of the traumatic experience. As persistent glucocorticoid-induced loss of DNA methylation in FK506 binding protein 5 (Fkbp5) was previously observed in the hippocampus and blood and in the neuronal cell line HT-22, we asked whether these epigenetic alterations occur in non-neuronal, HPA-axis relevant cells. We used the pituitary adenoma cell line AtT-20 to demonstrate that the intronic enhancer region of Fkbp5 undergoes loss of DNA methylation in response to dexamethasone treatment in a dose-dependent manner. We also focused on the mouse hippocampal dentate gyrus to test whether these changes would be enriched in a region implicated in the HPA-axis stress response, neurogenesis, and synaptic plasticity. We observed an increase in enrichment of DNA methylation loss in the dentate gyrus, as compared to whole hippocampal tissues that were similarly treated with glucocorticoids. We then asked whether DNA methyltransferase 1 (Dnmt1), a methyltransferase enzyme involved in maintaining DNA methylation following cell division, is involved in the observed epigenetic alterations. We found a dose-dependent decrease of Dnmt1 expression in the AtT-20 cells following dexamethasone treatment, and a similar decrease in corticosterone-treated mouse hippocampus. Taken together, we provide evidence that these glucocorticoid-induced epigenetic alterations have a broader validity in non-neuronal cells and that they may involve the DNA methylation machinery.Biochemical and Biophysical Research Communications 03/2012; 420(3):570-5. · 2.41 Impact Factor
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ABSTRACT: Glucocorticoid (GC) hormones, released by the adrenals in response to stress, are key regulators of neuronal plasticity. In the brain, the hippocampus is a major target of GC, with abundant expression of the GC receptor. GC differentially affect the hippocampal transcriptome and consequently neuronal plasticity in a subregion-specific manner, with consequences for hippocampal information flow and memory formation. Here, we show that GC directly affect the mammalian target of rapamycin (mTOR) signaling pathway, which plays a central role in translational control and has long-lasting effects on the plasticity of specific brain circuits. We demonstrate that regulators of the mTOR pathway, DNA damage-induced transcript (DDIT)4 and FK506-binding protein 51 are transcriptionally up-regulated by an acute GC challenge in the dentate gyrus (DG) subregion of the rat hippocampus, most likely via a GC-response element-driven mechanism. Furthermore, two other mTOR pathway members, the mTOR regulator DDIT4-like and the mTOR target DDIT3, are down-regulated by GC in the rat DG. Interestingly, the GC responsiveness of DDIT4 and DDIT3 was lost in animals with a recent history of chronic stress. Basal hippocampal mTOR protein levels were higher in animals exposed to chronic stress than in controls. Moreover, an acute GC challenge significantly reduced mTOR protein levels in the hippocampus of animals with a chronic stress history but not in unstressed controls. Based on these findings, we propose that direct regulation of the mTOR pathway by GC represents an important mechanism regulating neuronal plasticity in the rat DG, which changes after exposure to chronic stress.Endocrinology 07/2012; 153(9):4317-27. · 4.72 Impact Factor
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ABSTRACT: Although the fact that genetic predisposition and environmental exposures interact to shape development and function of the human brain and, ultimately, the risk of psychiatric disorders has drawn wide interest, the corresponding molecular mechanisms have not yet been elucidated. We found that a functional polymorphism altering chromatin interaction between the transcription start site and long-range enhancers in the FK506 binding protein 5 (FKBP5) gene, an important regulator of the stress hormone system, increased the risk of developing stress-related psychiatric disorders in adulthood by allele-specific, childhood trauma-dependent DNA demethylation in functional glucocorticoid response elements of FKBP5. This demethylation was linked to increased stress-dependent gene transcription followed by a long-term dysregulation of the stress hormone system and a global effect on the function of immune cells and brain areas associated with stress regulation. This identification of molecular mechanisms of genotype-directed long-term environmental reactivity will be useful for designing more effective treatment strategies for stress-related disorders.Nature Neuroscience 12/2012; · 15.25 Impact Factor