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Zhu B, Zhu X, Borland MG, Ralph DH, Chiaro CR, Krausz KW, Ntambi JM, Glick AB, Patterson AD, Perdew GH, Gonzalez FJ, Peters JM. Activation of Peroxisome Proliferator-Activated Receptor-β/δ (PPARβ/δ) in Keratinocytes by Endogenous Fatty Acids. Biomolecules 2024; 14:606. [PMID: 38927010 PMCID: PMC11201440 DOI: 10.3390/biom14060606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2024] [Revised: 05/14/2024] [Accepted: 05/17/2024] [Indexed: 06/28/2024] Open
Abstract
Nuclear hormone receptors exist in dynamic equilibrium between transcriptionally active and inactive complexes dependent on interactions with ligands, proteins, and chromatin. The present studies examined the hypothesis that endogenous ligands activate peroxisome proliferator-activated receptor-β/δ (PPARβ/δ) in keratinocytes. The phorbol ester treatment or HRAS infection of primary keratinocytes increased fatty acids that were associated with enhanced PPARβ/δ activity. Fatty acids caused PPARβ/δ-dependent increases in chromatin occupancy and the expression of angiopoietin-like protein 4 (Angptl4) mRNA. Analyses demonstrated that stearoyl Co-A desaturase 1 (Scd1) mediates an increase in intracellular monounsaturated fatty acids in keratinocytes that act as PPARβ/δ ligands. The activation of PPARβ/δ with palmitoleic or oleic acid causes arrest at the G2/M phase of the cell cycle of HRAS-expressing keratinocytes that is not found in similarly treated HRAS-expressing Pparb/d-null keratinocytes. HRAS-expressing Scd1-null mouse keratinocytes exhibit enhanced cell proliferation, an effect that is mitigated by treatment with palmitoleic or oleic acid. Consistent with these findings, the ligand activation of PPARβ/δ with GW0742 or oleic acid prevented UVB-induced non-melanoma skin carcinogenesis, an effect that required PPARβ/δ. The results from these studies demonstrate that PPARβ/δ has endogenous roles in keratinocytes and can be activated by lipids found in diet and cellular components.
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Affiliation(s)
- Bokai Zhu
- Department of Veterinary and Biomedical Sciences, The Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, PA 16802, USA; (B.Z.); (X.Z.); (M.G.B.); (D.H.R.); (C.R.C.); (A.B.G.); (A.D.P.); (G.H.P.)
| | - Xiaoyang Zhu
- Department of Veterinary and Biomedical Sciences, The Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, PA 16802, USA; (B.Z.); (X.Z.); (M.G.B.); (D.H.R.); (C.R.C.); (A.B.G.); (A.D.P.); (G.H.P.)
| | - Michael G. Borland
- Department of Veterinary and Biomedical Sciences, The Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, PA 16802, USA; (B.Z.); (X.Z.); (M.G.B.); (D.H.R.); (C.R.C.); (A.B.G.); (A.D.P.); (G.H.P.)
- Department of Biochemistry, Microbiology and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA
| | - Douglas H. Ralph
- Department of Veterinary and Biomedical Sciences, The Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, PA 16802, USA; (B.Z.); (X.Z.); (M.G.B.); (D.H.R.); (C.R.C.); (A.B.G.); (A.D.P.); (G.H.P.)
| | - Christopher R. Chiaro
- Department of Veterinary and Biomedical Sciences, The Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, PA 16802, USA; (B.Z.); (X.Z.); (M.G.B.); (D.H.R.); (C.R.C.); (A.B.G.); (A.D.P.); (G.H.P.)
- Department of Genetics, The Pennsylvania State University, University Park, PA 16802, USA
| | - Kristopher W. Krausz
- Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA; (K.W.K.); (F.J.G.)
| | - James M. Ntambi
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI 53706, USA;
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Adam B. Glick
- Department of Veterinary and Biomedical Sciences, The Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, PA 16802, USA; (B.Z.); (X.Z.); (M.G.B.); (D.H.R.); (C.R.C.); (A.B.G.); (A.D.P.); (G.H.P.)
| | - Andrew D. Patterson
- Department of Veterinary and Biomedical Sciences, The Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, PA 16802, USA; (B.Z.); (X.Z.); (M.G.B.); (D.H.R.); (C.R.C.); (A.B.G.); (A.D.P.); (G.H.P.)
| | - Gary H. Perdew
- Department of Veterinary and Biomedical Sciences, The Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, PA 16802, USA; (B.Z.); (X.Z.); (M.G.B.); (D.H.R.); (C.R.C.); (A.B.G.); (A.D.P.); (G.H.P.)
- Department of Biochemistry, Microbiology and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA
- Department of Genetics, The Pennsylvania State University, University Park, PA 16802, USA
| | - Frank J. Gonzalez
- Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA; (K.W.K.); (F.J.G.)
| | - Jeffrey M. Peters
- Department of Veterinary and Biomedical Sciences, The Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, PA 16802, USA; (B.Z.); (X.Z.); (M.G.B.); (D.H.R.); (C.R.C.); (A.B.G.); (A.D.P.); (G.H.P.)
- Department of Biochemistry, Microbiology and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA
- Department of Genetics, The Pennsylvania State University, University Park, PA 16802, USA
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2
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Rizvi S, Chhabra A, Tripathi A, Tyagi RK. Mitotic genome-bookmarking by nuclear hormone receptors: A novel dimension in epigenetic reprogramming and disease assessment. Mol Cell Endocrinol 2023; 578:112069. [PMID: 37730146 DOI: 10.1016/j.mce.2023.112069] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2023] [Revised: 09/07/2023] [Accepted: 09/12/2023] [Indexed: 09/22/2023]
Abstract
Arrival of multi-colored fluorescent proteins and advances in live cell imaging has immensely contributed to our understanding of intracellular trafficking of nuclear receptors and their roles in gene regulatory functions. These regulatory events need to be faithfully propagated from progenitor to progeny cells. This is corroborated by multiple converging mechanisms that include histone modifications and lately, the phenomenon of 'mitotic genome-bookmarking' by specific transcription factors. This phenomenon refers to the retention and feed-forward transmission of progenitor's architectural blueprint of active transcription status which is silenced and preserved during mitosis. Upon mitotic exit, this phenomenon ensures accurate reactivation of transcriptome, proteome, cellular traits and phenotypes in the progeny cells. In addition to diverse modes of genome-bookmarking by nuclear receptors, a correlation between disease-associated receptor polymorphism and disruption of this phenomenon is apparent. However, breakthrough technologies shall reveal finer details of this phenomenon to help achieve normalcy in receptor-specific diseases.
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Affiliation(s)
- Sheeba Rizvi
- Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi, 110067, India
| | - Ayushi Chhabra
- Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi, 110067, India
| | - Anjali Tripathi
- Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi, 110067, India
| | - Rakesh K Tyagi
- Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi, 110067, India.
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3
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Hao Y, Han L, Wu A, Bochkis IM. Pioneer Factor Foxa2 Mediates Chromatin Conformation Changes for Activation of Bile Acid Targets of FXR. Cell Mol Gastroenterol Hepatol 2023; 17:237-249. [PMID: 37879405 PMCID: PMC10765059 DOI: 10.1016/j.jcmgh.2023.10.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Revised: 10/20/2023] [Accepted: 10/20/2023] [Indexed: 10/27/2023]
Abstract
BACKGROUND & AIMS Transcription factors regulate gene expression that orchestrates liver physiology. Many bind at distal enhancers and chromatin looping is required to activate their targets. Chromatin architecture has been linked to essential functions of the liver, including metabolism and sexually dimorphic gene expression. We have previously shown that pioneer factor Foxa2 opens chromatin for binding of nuclear receptors farnesoid X receptor (FXR) and liver X receptor-α during acute ligand activation. FXR is activated by bile acids and deletion of Foxa2 in the liver results in intrahepatic cholestasis. We hypothesized that Foxa2 also enables chromatin conformational changes during ligand activation and performed genome-wide studies to test this hypothesis. METHODS We performed Foxa2 HiChIP (Hi-C and ChIP) to assess Foxa2-dependent long-range interactions in mouse livers treated with either vehicle control or FXR agonist GW4064. RESULTS HiChIP contact analysis shows that global chromatin interactions are dramatically increased during FXR activation. Ligand-treated livers exhibit extensive redistribution of topological associated domains and substantial increase in Foxa2-anchored loops, suggesting Foxa2 is involved in dynamic chromatin conformational changes. We demonstrate that chromatin conformation, including genome-wide interactions, topological associated domains, and intrachromosomal and interchromosomal Foxa2-anchored loops, drastically changes on addition of FXR agonist. Additional Foxa2 binding in ligand-activated state leads to formation of Foxa2-anchored loops, leading to distal interactions and activation of gene expression of FXR targets. CONCLUSIONS Ligand activation of FXR, and likely of related receptors, requires global changes in chromatin architecture. We determine a novel role for Foxa2 in enabling these conformational changes, extending its function in bile acid metabolism.
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Affiliation(s)
- Yi Hao
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia
| | - Lu Han
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia
| | - Anqi Wu
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia
| | - Irina M Bochkis
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia.
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Zhu X, Liu Q, Patterson AD, Sharma AK, Amin SG, Cohen SM, Gonzalez FJ, Peters JM. Accumulation of Linoleic Acid by Altered Peroxisome Proliferator-Activated Receptor-α Signaling Is Associated with Age-Dependent Hepatocarcinogenesis in Ppara Transgenic Mice. Metabolites 2023; 13:936. [PMID: 37623879 PMCID: PMC10456914 DOI: 10.3390/metabo13080936] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 08/03/2023] [Accepted: 08/06/2023] [Indexed: 08/26/2023] Open
Abstract
Long-term ligand activation of PPARα in mice causes hepatocarcinogenesis through a mechanism that requires functional PPARα. However, hepatocarcinogenesis is diminished in both Ppara-null and PPARA-humanized mice, yet both lines develop age-related liver cancer independently of treatment with a PPARα agonist. Since PPARα is a master regulator of liver lipid metabolism in the liver, lipidomic analyses were carried out in wild-type, Ppara-null, and PPARA-humanized mice treated with and without the potent agonist GW7647. The levels of hepatic linoleic acid in Ppara-null and PPARA-humanized mice were markedly higher compared to wild-type controls, along with overall fatty liver. The number of liver CD4+ T cells was also lower in Ppara-null and PPARA-humanized mice and was negatively correlated with the elevated linoleic acid. Moreover, more senescent hepatocytes and lower serum TNFα and IFNγ levels were observed in Ppara-null and PPARA-humanized mice with age. These studies suggest a new role for PPARα in age-associated hepatocarcinogenesis due to altered lipid metabolism in Ppara-null and PPARA-humanized mice and the accumulation of linoleic acid as part of an overall fatty liver that is associated with loss of CD4+ T cells in the liver in both transgenic models. Since fatty liver is a known causal risk factor for liver cancer, Ppara-null and PPARA-humanized mice are valuable models for examining the mechanisms of PPARα and age-dependent hepatocarcinogenesis.
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Affiliation(s)
- Xiaoyang Zhu
- Department of Veterinary and Biomedical Science, The Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, State College, PA 16802, USA; (Q.L.); (A.D.P.); (J.M.P.)
| | - Qing Liu
- Department of Veterinary and Biomedical Science, The Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, State College, PA 16802, USA; (Q.L.); (A.D.P.); (J.M.P.)
| | - Andrew D. Patterson
- Department of Veterinary and Biomedical Science, The Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, State College, PA 16802, USA; (Q.L.); (A.D.P.); (J.M.P.)
| | - Arun K. Sharma
- Department of Pharmacology, The Pennsylvania State University, Hershey, PA 17033, USA; (A.K.S.); (S.G.A.)
| | - Shantu G. Amin
- Department of Pharmacology, The Pennsylvania State University, Hershey, PA 17033, USA; (A.K.S.); (S.G.A.)
| | - Samuel M. Cohen
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, NE 68198, USA;
| | - Frank J. Gonzalez
- Laboratory of Metabolism, National Cancer Institute, Bethesda, MD 20892, USA;
| | - Jeffrey M. Peters
- Department of Veterinary and Biomedical Science, The Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, State College, PA 16802, USA; (Q.L.); (A.D.P.); (J.M.P.)
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5
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Xia S, Lin Q. Estrogen Receptor Bio-Activities Determine Clinical Endocrine Treatment Options in Estrogen Receptor-Positive Breast Cancer. Technol Cancer Res Treat 2022; 21:15330338221090351. [PMID: 35450488 PMCID: PMC9036337 DOI: 10.1177/15330338221090351] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
In estrogen receptor positive (ER+) breast cancer therapy, estrogen receptors (ERs) are the major targeting molecules. ER-targeted therapy has provided clinical benefits for approximately 70% of all breast cancer patients through targeting the ERα subtype. In recent years, mechanisms underlying breast cancer occurrence and progression have been extensively studied and largely clarified. The PI3K/AKT/mTOR pathway, microRNA regulation, and other ER downstream signaling pathways are found to be the effective therapeutic targets in ER+ BC therapy. A number of the ER+ (ER+) breast cancer biomarkers have been established for diagnosis and prognosis. The ESR1 gene mutations that lead to endocrine therapy resistance in ER+ breast cancer had been identified. Mutations in the ligand-binding domain of ERα which encoded by ESR1 gene occur in most cases. The targeted drugs combined with endocrine therapy have been developed to improve the therapeutic efficacy of ER+ breast cancer, particularly the endocrine therapy resistance ER+ breast cancer. The combination therapy has been demonstrated to be superior to monotherapy in overall clinical evaluation. In this review, we focus on recent progress in studies on ERs and related clinical applications for targeted therapy and provide a perspective view for therapy of ER+ breast cancer.
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Affiliation(s)
- Song Xia
- School of Medicine, Jiangsu University, Zhenjiang, China
| | - Qiong Lin
- School of Medicine, Jiangsu University, Zhenjiang, China
- Qiong Lin, School of Medicine, Jiangsu University, 301 Xuefu Road, Zhenjiang, China.
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6
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Vini R, Rajavelu A, Sreeharshan S. 27-Hydroxycholesterol, The Estrogen Receptor Modulator, Alters DNA Methylation in Breast Cancer. Front Endocrinol (Lausanne) 2022; 13:783823. [PMID: 35360070 PMCID: PMC8961300 DOI: 10.3389/fendo.2022.783823] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 01/13/2022] [Indexed: 01/01/2023] Open
Abstract
27-hydroxycholesterol (27-HC) is the first known endogenous selective estrogen receptor modulator (SERM), and its elevation from normal levels is closely associated with breast cancer. A plethora of evidence suggests that aberrant epigenetic signatures in breast cancer cells can result in differential responses to various chemotherapeutics and often leads to the development of resistant cancer cells. Such aberrant epigenetic changes are mostly dictated by the microenvironment. The local concentration of oxygen and metabolites in the microenvironment of breast cancer are known to influence the development of breast cancer. Hence, we hypothesized that 27-HC, an oxysterol, which has been shown to induce breast cancer progression via estrogen receptor alpha (ERα) and liver X receptor (LXR) and by modulating immune cells, may also induce epigenetic changes. For deciphering the same, we treated the estrogen receptor-positive cells with 27-HC and identified DNA hypermethylation on a subset of genes by performing DNA bisulfite sequencing. The genes that showed significant DNA hypermethylation were phosphatidylserine synthase 2 (PTDSS2), MIR613, indoleamine 2,3-dioxygenase 1 (IDO1), thyroid hormone receptor alpha (THRA), dystrotelin (DTYN), and mesoderm induction early response 1, family member 3 (MIER). Furthermore, we found that 27-HC weakens the DNMT3B association with the ERα in MCF-7 cells. This study reports that 27-HC induces aberrant DNA methylation changes on the promoters of a subset of genes through modulation of ERα and DNMT3B complexes to induce the local DNA methylation changes, which may dictate drug responses and breast cancer development.
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Affiliation(s)
- Ravindran Vini
- Cancer Research Program, Rajiv Gandhi Centre for Biotechnology (RGCB), Thiruvananthapuram, India
| | - Arumugam Rajavelu
- Pathogen Biology, Rajiv Gandhi Centre for Biotechnology (RGCB), Thiruvananthapuram, India
- Department of Biotechnology, Bhupat & Jyoti Mehta School of Biosciences, Indian Institute of Technology, Chennai, India
- *Correspondence: Arumugam Rajavelu, ; Sreeja Sreeharshan,
| | - Sreeja Sreeharshan
- Cancer Research Program, Rajiv Gandhi Centre for Biotechnology (RGCB), Thiruvananthapuram, India
- *Correspondence: Arumugam Rajavelu, ; Sreeja Sreeharshan,
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7
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Suter DM. Transcription Factors and DNA Play Hide and Seek. Trends Cell Biol 2020; 30:491-500. [PMID: 32413318 DOI: 10.1016/j.tcb.2020.03.003] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 03/12/2020] [Accepted: 03/16/2020] [Indexed: 01/12/2023]
Abstract
Transcription factors (TFs) bind to specific DNA motifs to regulate the expression of target genes. To reach their binding sites, TFs diffuse in 3D and perform local motions such as 1D sliding, hopping, or intersegmental transfer. TF-DNA interactions depend on multiple parameters, such as the chromatin environment, TF partitioning into distinct subcellular regions, and cooperativity with other DNA-binding proteins. In this review, how current understanding of the search process has initially been shaped by prokaryotic studies is discussed, as well as what is known about the parameters regulating TF search efficiency in the context of the complex eukaryotic chromatin landscape.
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Affiliation(s)
- David M Suter
- Institute of Bioengineering, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
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8
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Borland MG, Yao PL, Kehres EM, Lee C, Pritzlaff AM, Ola E, Wagner AL, Shannon BE, Albrecht PP, Zhu B, Kang BH, Robertson GP, Gonzalez FJ, Peters JM. Editor's Highlight: PPARβ/δ and PPARγ Inhibit Melanoma Tumorigenicity by Modulating Inflammation and Apoptosis. Toxicol Sci 2018; 159:436-448. [PMID: 28962521 DOI: 10.1093/toxsci/kfx147] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Skin tumorigenesis results from DNA damage, increased inflammation, and evasion of apoptosis. The peroxisome proliferator-activated receptors (PPARs) can modulate these mechanisms in non-melanoma skin cancer. However, limited data exists regarding the role of PPARs in melanoma. This study examined the effect of proliferator-activated receptor-β/δ (PPARβ/δ) and PPARγ on cell proliferation, anchorage-dependent clonogenicity, and ectopic xenografts in the UACC903 human melanoma cell line. Stable overexpression of either PPARβ/δ or PPARγ enhanced ligand-induced expression of a PPARβ/δ/PPARγ target gene in UACC903 cell lines as compared with controls. The induction of target gene expression by ligand activation of PPARγ was not altered by overexpression of PPARβ/δ, or vice versa. Stable overexpression of either PPARβ/δ or PPARγ reduced the percentage of cells in the G1 and S phase of the cell cycle, and increased the percentage of cells in the G2/M phase of the cell cycle in UACC903 cell lines as compared with controls. Ligand activation of PPARβ/δ did not further alter the distribution of cells within each phase of the cell cycle. By contrast, ligand activation of PPARγ enhanced these changes in stable UACC903 cells overexpressing PPARγ compared with controls. Stable overexpression of either PPARβ/δ or PPARγ and/or ligand activation of either PPARβ/δ or PPARγ inhibited cell proliferation, and anchorage-dependent clonogenicity of UACC903 cell lines as compared with controls. Further, overexpression of either PPARβ/δ or PPARγ and/or ligand activation of either PPARβ/δ or PPARγ inhibited ectopic xenograft tumorigenicity derived from UACC903 melanoma cells as compared with controls, and this was likely due in part to induction of apoptosis. Results from these studies demonstrate the antitumorigenic effects of both PPARβ/δ and PPARγ and suggest that targeting these receptors may be useful for primary or secondary melanoma chemoprevention.
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Affiliation(s)
- Michael G Borland
- Department of Veterinary and Biomedical Sciences, The Center of Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, Pennsylvania 16802.,Department of Chemistry and Biochemistry, Bloomsburg University of Pennsylvania, Bloomsburg, Pennsylvania 17815
| | - Pei-Li Yao
- Department of Veterinary and Biomedical Sciences, The Center of Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Ellen M Kehres
- Department of Chemistry and Biochemistry, Bloomsburg University of Pennsylvania, Bloomsburg, Pennsylvania 17815
| | - Christina Lee
- Department of Veterinary and Biomedical Sciences, The Center of Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Amanda M Pritzlaff
- Department of Chemistry and Biochemistry, Bloomsburg University of Pennsylvania, Bloomsburg, Pennsylvania 17815
| | - Elizabeth Ola
- Department of Chemistry and Biochemistry, Bloomsburg University of Pennsylvania, Bloomsburg, Pennsylvania 17815
| | - Ashley L Wagner
- Department of Chemistry and Biochemistry, Bloomsburg University of Pennsylvania, Bloomsburg, Pennsylvania 17815
| | - Brooke E Shannon
- Department of Chemistry and Biochemistry, Bloomsburg University of Pennsylvania, Bloomsburg, Pennsylvania 17815
| | - Prajakta P Albrecht
- Department of Veterinary and Biomedical Sciences, The Center of Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Bokai Zhu
- Department of Veterinary and Biomedical Sciences, The Center of Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, Pennsylvania 16802
| | - Boo-Hyon Kang
- Non-clinical Research Institute, Chemon, Yangji-Myeon, Cheoin-Gu, Yongin-Si, Gyeonggi-Do 17162, Korea
| | - Gavin P Robertson
- Departments of Pharmacology, Pathology, Dermatology, Surgery, The Melanoma and Skin Cancer Center, and The Melanoma Therapeutics Program, The Pennsylvania State University, Hershey, Pennsylvania 17033
| | - Frank J Gonzalez
- Laboratory of Metabolism, National Cancer Institute, Bethesda, Maryland 20892
| | - Jeffrey M Peters
- Department of Veterinary and Biomedical Sciences, The Center of Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, Pennsylvania 16802
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9
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Majumder A, Singh M, Tyagi SC. Post-menopausal breast cancer: from estrogen to androgen receptor. Oncotarget 2017; 8:102739-102758. [PMID: 29254284 PMCID: PMC5731994 DOI: 10.18632/oncotarget.22156] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Accepted: 09/29/2017] [Indexed: 12/20/2022] Open
Abstract
In the United States, breast cancer is the second leading cause of death among women, and even though different therapies can treat primary breast tumors, most breast cancer-related deaths (>95%) occur due to metastasis. A majority (~70%) of breast tumors are found to express estrogen receptor, and a significant portion (~90%) of ER-positive (ER+) breast tumors are also androgen receptor-positive (AR+). Although ER is known to promote tumorigenesis, the role and underlying mechanism(s) of AR in these closely knit processes remain controversial. Endocrine therapies are the most commonly used treatment for patients with ER+ breast tumors; but, ~30%-50% of initially responsive patients develop resistance to these therapies. Whereas 70%–90% of all breast tumors are AR+ and AR overexpression is correlated with endocrine resistance, but the precise molecular mechanism(s) for this association is yet to be studied. Multiple mechanisms have been proposed to show AR and ER interactions, which indicate that AR may preferentially regulate expression of a subset of ER-responsive genes and that may be responsible for breast cancer and its progression in affected patients. On the other hand, most of the ER+ breast tumors found in post-menopausal women (~80%); and they have very low 17β-estradiol and high androgen levels, but how these hormonal changes make someone more prone to cancer phenotype has long been a disputed issue. In this study, we have discussed multiple molecular mechanisms that we believe are central to the understanding of the overall contributions of AR in breast cancer and its metastasis in post-menopausal women.
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Affiliation(s)
- Avisek Majumder
- Department of Biochemistry and Molecular Genetics, University of Louisville School of Medicine, Louisville 40202, Kentucky, USA.,Department of Physiology, University of Louisville School of Medicine, Louisville 40202, Kentucky, USA
| | - Mahavir Singh
- Department of Physiology, University of Louisville School of Medicine, Louisville 40202, Kentucky, USA
| | - Suresh C Tyagi
- Department of Physiology, University of Louisville School of Medicine, Louisville 40202, Kentucky, USA
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10
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Coons LA, Hewitt SC, Burkholder AB, McDonnell DP, Korach KS. DNA Sequence Constraints Define Functionally Active Steroid Nuclear Receptor Binding Sites in Chromatin. Endocrinology 2017; 158:3212-3234. [PMID: 28977594 PMCID: PMC5659708 DOI: 10.1210/en.2017-00468] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Accepted: 06/30/2017] [Indexed: 12/17/2022]
Abstract
Gene regulatory programs are encoded in the sequence of the DNA. Since the completion of the Human Genome Project, millions of gene regulatory elements have been identified in the human genome. Understanding how each of those sites functionally contributes to gene regulation, however, remains a challenge for nearly every field of biology. Transcription factors influence cell function by interpreting information contained within cis-regulatory elements in chromatin. Whereas chromatin immunoprecipitation-sequencing has been used to identify and map transcription factor-DNA interactions, it has been difficult to assign functionality to the binding sites identified. Thus, in this study, we probed the transcriptional activity, DNA-binding competence, and functional activity of select nuclear receptor mutants in cellular and animal model systems and used this information to define the sequence constraints of functional steroid nuclear receptor cis-regulatory elements. Analysis of the architecture within sNR chromatin interacting sites revealed that only a small fraction of all sNR chromatin-interacting events is associated with transcriptional output and that this functionality is restricted to elements that vary from the consensus palindromic elements by one or two nucleotides. These findings define the transcriptional grammar necessary to predict functionality from regulatory sequences, with a multitude of future implications.
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Affiliation(s)
- Laurel A Coons
- Receptor Biology Section, Reproductive and Developmental Biology Laboratory, National Institute of Environmental Health Sciences/National Institutes of Health, Research Triangle Park, North Carolina 27709
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, North Carolina 27710
| | - Sylvia C Hewitt
- Receptor Biology Section, Reproductive and Developmental Biology Laboratory, National Institute of Environmental Health Sciences/National Institutes of Health, Research Triangle Park, North Carolina 27709
| | - Adam B Burkholder
- Integrative Bioinformatics, National Institute of Environmental Health Sciences/National Institutes of Health, Research Triangle Park, North Carolina 27709
| | - Donald P McDonnell
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, North Carolina 27710
| | - Kenneth S Korach
- Receptor Biology Section, Reproductive and Developmental Biology Laboratory, National Institute of Environmental Health Sciences/National Institutes of Health, Research Triangle Park, North Carolina 27709
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11
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Abstract
Endogenous glucocorticoids are crucial to various physiological processes, including metabolism, development and inflammation. Since 1948, synthetic glucocorticoids have been used to treat various immune-related disorders. The mechanisms that underlie the immunosuppressive properties of these hormones have been intensely scrutinized, and it is widely appreciated that glucocorticoids have pleiotropic effects on the immune system. However, a clear picture of the cellular and molecular basis of glucocorticoid action has remained elusive. In this Review, we distil several decades of intense (and often conflicting) research that defines the interface between the endocrine stress response and the immune system.
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Affiliation(s)
- Derek W Cain
- Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina 27709, USA
| | - John A Cidlowski
- Signal Transduction Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina 27709, USA
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12
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Gray GA, White CI, Castellan RFP, McSweeney SJ, Chapman KE. Getting to the heart of intracellular glucocorticoid regeneration: 11β-HSD1 in the myocardium. J Mol Endocrinol 2017; 58:R1-R13. [PMID: 27553202 PMCID: PMC5148800 DOI: 10.1530/jme-16-0128] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Accepted: 08/19/2016] [Indexed: 12/11/2022]
Abstract
Corticosteroids influence the development and function of the heart and its response to injury and pressure overload via actions on glucocorticoid (GR) and mineralocorticoid (MR) receptors. Systemic corticosteroid concentration depends largely on the activity of the hypothalamic-pituitary-adrenal (HPA) axis, but glucocorticoid can also be regenerated from intrinsically inert metabolites by the enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), selectively increasing glucocorticoid levels within cells and tissues. Extensive studies have revealed the roles for glucocorticoid regeneration by 11β-HSD1 in liver, adipose, brain and other tissues, but until recently, there has been little focus on the heart. This article reviews the evidence for glucocorticoid metabolism by 11β-HSD1 in the heart and for a role of 11β-HSD1 activity in determining the myocardial growth and physiological function. We also consider the potential of 11β-HSD1 as a therapeutic target to enhance repair after myocardial infarction and to prevent the development of cardiac remodelling and heart failure.
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Affiliation(s)
- Gillian A Gray
- University/BHF Centre for Cardiovascular ScienceQueen's Medical Research Institute, University of Edinburgh, Edinburgh, UK
| | - Christopher I White
- University/BHF Centre for Cardiovascular ScienceQueen's Medical Research Institute, University of Edinburgh, Edinburgh, UK
| | - Raphael F P Castellan
- University/BHF Centre for Cardiovascular ScienceQueen's Medical Research Institute, University of Edinburgh, Edinburgh, UK
| | - Sara J McSweeney
- University/BHF Centre for Cardiovascular ScienceQueen's Medical Research Institute, University of Edinburgh, Edinburgh, UK
| | - Karen E Chapman
- University/BHF Centre for Cardiovascular ScienceQueen's Medical Research Institute, University of Edinburgh, Edinburgh, UK
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13
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Corley SM, Tsai SY, Wilkins MR, Shannon Weickert C. Transcriptomic Analysis Shows Decreased Cortical Expression of NR4A1, NR4A2 and RXRB in Schizophrenia and Provides Evidence for Nuclear Receptor Dysregulation. PLoS One 2016; 11:e0166944. [PMID: 27992436 PMCID: PMC5161508 DOI: 10.1371/journal.pone.0166944] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Accepted: 11/06/2016] [Indexed: 12/14/2022] Open
Abstract
Many genes are differentially expressed in the cortex of people with schizophrenia, implicating factors that control transcription more generally. Hormone nuclear receptors dimerize to coordinate context-dependent changes in gene expression. We hypothesized that members of two families of nuclear receptors (NR4As), and retinoid receptors (RARs and RXRs), are altered in the dorsal lateral prefrontal cortex (DLPFC) of people with schizophrenia. We used next generation sequencing and then qPCR analysis to test for changes in mRNA levels for transcripts encoding nuclear receptors: orphan nuclear receptors (3 in the NR4A, 3 in the RAR, 3 in the RXR families and KLF4) in total RNA extracted from the DLPFC from people with schizophrenia compared to controls (n = 74). We also correlated mRNA levels with demographic factors and with estimates of antipsychotic drug exposure (schizophrenia group only). We tested for correlations between levels of transcription factor family members and levels of genes putatively regulated by these transcription factors. We found significantly down regulated expression of NR4A1 (Nurr 77) and KLF4 mRNAs in people with schizophrenia compared to controls, by both NGS and qPCR (p = or <0.01). We also detected decreases in NR4A2 (Nurr1) and RXRB mRNAs by using qPCR in the larger cohort (p<0.05 and p<0.01, respectively). We detected decreased expression of RARG and NR4A2 mRNAs in females with schizophrenia (p<0.05). The mRNA levels of NR4A1, NR4A2 and NR4A3 were all negative correlated with lifetime estimates of antipsychotic exposure. These novel findings, which may be influenced by antipsychotic drug exposure, implicate the orphan and retinoid nuclear receptors in the cortical pathology found in schizophrenia. Genes down stream of these receptors can be dysregulated as well, but the direction of change is not immediately predictable based on the putative transcription factor changes.
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Affiliation(s)
- Susan M. Corley
- Systems Biology Initiative, School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Shan-Yuan Tsai
- Schizophrenia Research Institute, Randwick, NSW, Australia
- Neuroscience Research Australia, Randwick, NSW, Australia
- School of Psychiatry, University of New South Wales Sydney, NSW, Australia
| | - Marc R. Wilkins
- Systems Biology Initiative, School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales, Australia
| | - Cynthia Shannon Weickert
- Schizophrenia Research Institute, Randwick, NSW, Australia
- Neuroscience Research Australia, Randwick, NSW, Australia
- School of Psychiatry, University of New South Wales Sydney, NSW, Australia
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14
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Protective Role of PPARdelta in Lipoapoptosis of Pancreatic β Cells. Lipids 2016; 51:1259-1268. [PMID: 27631677 DOI: 10.1007/s11745-016-4190-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Accepted: 08/18/2016] [Indexed: 02/05/2023]
Abstract
Lipoapoptosis plays an important role in the pathogenesis of type 2 diabetes. Peroxisome proliferator-activated receptor delta (PPARdelta), a vital regulator of glucose and lipid metabolism, may reduce fatty acid-induced pancreatic β cell lipotoxicity in diabetes. However, the detailed molecular mechanisms underlying this process are not fully understood. In this study, we investigated the effect of activation of PPARdelta on palmitate-induced β cell apoptosis, and we explored the potential mechanism of the antiapoptotic effect. The cell apoptosis was determined by DNA fragmentation analysis and Hoechst 33342 staining. The expressing of glucagon-like peptide-1 receptor (GLP-1R) in INS-1 cells was assessed by Western blotting, quantification of PCR, and was further confirmed by immunofluorescence staining. The potential of PPARdelta to interact with homologous PPRE in the GLP-1R gene was determined by Chromatin immunoprecipitation (ChIP). Our results showed that exposure of INS-1 cells to palmitate for 24 h caused a significant increase in cell apoptosis, which was inhibited by GW501516. PPARdelta exerted anti-apoptotic effects in pancreatic β cells via the PI3 K/PKB/FoxO1 signaling pathway. Moreover, PPARdelta upregulated the GLP-1R expression under lipotoxic conditions. The ChIP assay revealed a direct binding of PPARdelta to a noncanonical PPRE motif of the GLP-1R gene in INS-1 cells. Our study suggested that the anti-apoptotic action of PPARdelta may involve its transcriptional regulation of GLP-1R and PI3 K/PKB/FoxO1 signaling. GW501516 and possible other GW-based strategies may confer additional benefit beyond improved glycemic control.
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15
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Hartmann K, Koenen M, Schauer S, Wittig-Blaich S, Ahmad M, Baschant U, Tuckermann JP. Molecular Actions of Glucocorticoids in Cartilage and Bone During Health, Disease, and Steroid Therapy. Physiol Rev 2016; 96:409-47. [PMID: 26842265 DOI: 10.1152/physrev.00011.2015] [Citation(s) in RCA: 141] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Cartilage and bone are severely affected by glucocorticoids (GCs), steroid hormones that are frequently used to treat inflammatory diseases. Major complications associated with long-term steroid therapy include impairment of cartilaginous bone growth and GC-induced osteoporosis. Particularly in arthritis, GC application can increase joint and bone damage. Contrarily, endogenous GC release supports cartilage and bone integrity. In the last decade, substantial progress in the understanding of the molecular mechanisms of GC action has been gained through genome-wide binding studies of the GC receptor. These genomic approaches have revolutionized our understanding of gene regulation by ligand-induced transcription factors in general. Furthermore, specific inactivation of GC signaling and the GC receptor in bone and cartilage cells of rodent models has enabled the cell-specific effects of GCs in normal tissue homeostasis, inflammatory bone diseases, and GC-induced osteoporosis to be dissected. In this review, we summarize the current view of GC action in cartilage and bone. We further discuss future research directions in the context of new concepts for optimized steroid therapies with less detrimental effects on bone.
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Affiliation(s)
- Kerstin Hartmann
- Institute for Comparative Molecular Endocrinology, University of Ulm, Ulm, Germany; and Division of Endocrinology, Diabetes, and Bone Diseases, Department of Medicine III, Technische Universität Dresden, Dresden, Germany
| | - Mascha Koenen
- Institute for Comparative Molecular Endocrinology, University of Ulm, Ulm, Germany; and Division of Endocrinology, Diabetes, and Bone Diseases, Department of Medicine III, Technische Universität Dresden, Dresden, Germany
| | - Sebastian Schauer
- Institute for Comparative Molecular Endocrinology, University of Ulm, Ulm, Germany; and Division of Endocrinology, Diabetes, and Bone Diseases, Department of Medicine III, Technische Universität Dresden, Dresden, Germany
| | - Stephanie Wittig-Blaich
- Institute for Comparative Molecular Endocrinology, University of Ulm, Ulm, Germany; and Division of Endocrinology, Diabetes, and Bone Diseases, Department of Medicine III, Technische Universität Dresden, Dresden, Germany
| | - Mubashir Ahmad
- Institute for Comparative Molecular Endocrinology, University of Ulm, Ulm, Germany; and Division of Endocrinology, Diabetes, and Bone Diseases, Department of Medicine III, Technische Universität Dresden, Dresden, Germany
| | - Ulrike Baschant
- Institute for Comparative Molecular Endocrinology, University of Ulm, Ulm, Germany; and Division of Endocrinology, Diabetes, and Bone Diseases, Department of Medicine III, Technische Universität Dresden, Dresden, Germany
| | - Jan P Tuckermann
- Institute for Comparative Molecular Endocrinology, University of Ulm, Ulm, Germany; and Division of Endocrinology, Diabetes, and Bone Diseases, Department of Medicine III, Technische Universität Dresden, Dresden, Germany
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16
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Kommagani R, Szwarc MM, Vasquez YM, Peavey MC, Mazur EC, Gibbons WE, Lanz RB, DeMayo FJ, Lydon JP. The Promyelocytic Leukemia Zinc Finger Transcription Factor Is Critical for Human Endometrial Stromal Cell Decidualization. PLoS Genet 2016; 12:e1005937. [PMID: 27035670 PMCID: PMC4817989 DOI: 10.1371/journal.pgen.1005937] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Accepted: 02/24/2016] [Indexed: 11/17/2022] Open
Abstract
Progesterone, via the progesterone receptor (PGR), is essential for endometrial stromal cell decidualization, a cellular transformation event in which stromal fibroblasts differentiate into decidual cells. Uterine decidualization supports embryo implantation and placentation as well as subsequent events, which together ensure a successful pregnancy. Accordingly, impaired decidualization results not only in implantation failure or early fetal miscarriage, but also may lead to potential adverse outcomes in all three pregnancy trimesters. Transcriptional reprogramming on a genome-wide scale underlies progesterone dependent decidualization of the human endometrial stromal cell (hESC). However, identification of the functionally essential signals encoded by these global transcriptional changes remains incomplete. Importantly, this knowledge-gap undercuts future efforts to improve diagnosis and treatment of implantation failure based on a dysfunctional endometrium. By integrating genome-wide datasets derived from decidualization of hESCs in culture, we reveal that the promyelocytic leukemia zinc finger (PLZF) transcription factor is rapidly induced by progesterone and that this induction is indispensable for progesterone-dependent decidualization. Chromatin immunoprecipitation followed by next generation sequencing (ChIP-Seq) identified at least ten progesterone response elements within the PLZF gene, indicating that PLZF may act as a direct target of PGR signaling. The spatiotemporal expression profile for PLZF in both the human and mouse endometrium offers further support for stromal PLZF as a mediator of the progesterone decidual signal. To identify functional targets of PLZF, integration of PLZF ChIP-Seq and RNA Pol II RNA-Seq datasets revealed that the early growth response 1 (EGR1) transcription factor is a PLZF target for which its level of expression must be reduced to enable progesterone dependent hESC decidualization. Apart from furnishing essential insights into the molecular mechanisms by which progesterone drives hESC decidualization, our findings provide a new conceptual framework that could lead to new avenues for diagnosis and/or treatment of adverse reproductive outcomes associated with a dysfunctional uterus.
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Affiliation(s)
- Ramakrishna Kommagani
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Maria M. Szwarc
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Yasmin M. Vasquez
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Mary C. Peavey
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, United States of America
- Department of Obstetrics and Gynecology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Erik C. Mazur
- Houston Fertility Specialists, Houston, Texas, United States of America
| | - William E. Gibbons
- Department of Obstetrics and Gynecology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Rainer B. Lanz
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Francesco J. DeMayo
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, United States of America
| | - John P. Lydon
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, United States of America
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17
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Thompson B, Varticovski L, Baek S, Hager GL. Genome-Wide Chromatin Landscape Transitions Identify Novel Pathways in Early Commitment to Osteoblast Differentiation. PLoS One 2016; 11:e0148619. [PMID: 26890492 PMCID: PMC4759368 DOI: 10.1371/journal.pone.0148619] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Accepted: 01/20/2016] [Indexed: 12/17/2022] Open
Abstract
Bone continuously undergoes remodeling by a tightly regulated process that involves osteoblast differentiation from Mesenchymal Stem Cells (MSC). However, commitment of MSC to osteoblastic lineage is a poorly understood process. Chromatin organization functions as a molecular gatekeeper of DNA functions. Detection of sites that are hypersensitive to Dnase I has been used for detailed examination of changes in response to hormones and differentiation cues. To investigate the early steps in commitment of MSC to osteoblasts, we used a model human temperature-sensitive cell line, hFOB. When shifted to non-permissive temperature, these cells undergo "spontaneous" differentiation that takes several weeks, a process that is greatly accelerated by osteogenic induction media. We performed Dnase I hypersensitivity assays combined with deep sequencing to identify genome-wide potential regulatory events in cells undergoing early steps of commitment to osteoblasts. Massive reorganization of chromatin occurred within hours of differentiation. Whereas ~30% of unique DHS sites were located in the promoters, the majority was outside of the promoters, designated as enhancers. Many of them were at novel genomic sites and need to be confirmed experimentally. We developed a novel method for identification of cellular networks based solely on DHS enhancers signature correlated to gene expression. The analysis of enhancers that were unique to differentiating cells led to identification of bone developmental program encompassing 147 genes that directly or indirectly participate in osteogenesis. Identification of these pathways provided an unprecedented view of genomic regulation during early steps of differentiation and changes related to WNT, AP-1 and other pathways may have therapeutic implications.
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Affiliation(s)
- Bethtrice Thompson
- Laboratory of Receptor Biology and Gene Expression, NCI, NIH, Bethesda, MD, United States of America
- Center for Cancer Research and Therapeutic Development, Clark Atlanta University, Atlanta, GA, United States of America
| | - Lyuba Varticovski
- Laboratory of Receptor Biology and Gene Expression, NCI, NIH, Bethesda, MD, United States of America
- * E-mail:
| | - Songjoon Baek
- Laboratory of Receptor Biology and Gene Expression, NCI, NIH, Bethesda, MD, United States of America
| | - Gordon L. Hager
- Laboratory of Receptor Biology and Gene Expression, NCI, NIH, Bethesda, MD, United States of America
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18
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Abstract
Estrogen receptor alpha (ERα) is a critical player in development and function of the female reproductive system. Perturbations in ERα response can affect wide-ranging aspects of health in humans as well as in livestock and wildlife. Because of its long-known and broad impact, ERα mechanisms of action continue to be the focus on cutting-edge research efforts. Consequently, novel insights have greatly advanced understanding of every aspect of estrogen signaling. In this review, we attempt to briefly outline the current understanding of ERα mediated mechanisms in the context of the female reproductive system.
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Affiliation(s)
- Sylvia C Hewitt
- Receptor Biology GroupReproductive and Developmental Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USASchool of Molecular BiosciencesCollege of Veterinary Medicine, Washington State University, Pullman, Washington 99164, USA
| | - Wipawee Winuthayanon
- Receptor Biology GroupReproductive and Developmental Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USASchool of Molecular BiosciencesCollege of Veterinary Medicine, Washington State University, Pullman, Washington 99164, USA
| | - Kenneth S Korach
- Receptor Biology GroupReproductive and Developmental Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USASchool of Molecular BiosciencesCollege of Veterinary Medicine, Washington State University, Pullman, Washington 99164, USA
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19
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Thomas AL, Coarfa C, Qian J, Wilkerson JJ, Rajapakshe K, Krett NL, Gunaratne PH, Rosen ST. Identification of potential glucocorticoid receptor therapeutic targets in multiple myeloma. NUCLEAR RECEPTOR SIGNALING 2015; 13:e006. [PMID: 26715915 PMCID: PMC4693629 DOI: 10.1621/nrs.13006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/31/2015] [Accepted: 10/27/2015] [Indexed: 12/29/2022]
Abstract
Glucocorticoids (GC) are a cornerstone of combination therapies for multiple myeloma. However, patients ultimately develop resistance to GCs frequently based on decreased glucocorticoid receptor (GR) expression. An understanding of the direct targets of GC actions, which induce cell death, is expected to culminate in potential therapeutic strategies for inducing cell death by regulating downstream targets in the absence of a functional GR. The specific goal of our research is to identify primary GR targets that contribute to GC-induced cell death, with the ultimate goal of developing novel therapeutics around these targets that can be used to overcome resistance to GCs in the absence of GR. Using the MM.1S glucocorticoid-sensitive human myeloma cell line, we began with the broad platform of gene expression profiling to identify glucocorticoid-regulated genes further refined by combination treatment with phosphatidylinositol-3’-kinase inhibition (PI3Ki). To further refine the search to distinguish direct and indirect targets of GR that respond to the combination GC and PI3Ki treatment of MM.1S cells, we integrated 1) gene expression profiles of combination GC treatment with PI3Ki, which induces synergistic cell death; 2) negative correlation between genes inhibited by combination treatment in MM.1S cells and genes over-expressed in myeloma patients to establish clinical relevance and 3) GR chromatin immunoprecipitation with massively parallel sequencing (ChIP-Seq) in myeloma cells to identify global chromatin binding for the glucocorticoid receptor (GR). Using established bioinformatics platforms, we have integrated these data sets to identify a subset of candidate genes that may form the basis for a comprehensive picture of glucocorticoid actions in multiple myeloma. As a proof of principle, we have verified two targets, namely RRM2 and BCL2L1, as primary functional targets of GR involved in GC-induced cell death.
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Affiliation(s)
- Alexandra L Thomas
- Northwestern University, Robert H. Lurie Comprehensive Cancer Center, Chicago, Illinois (ALT, JQ, NLK, STR); Baylor College of Medicine, Department of Molecular and Human Genetics, Houston, Texas (CC, JJW, KR); University of Houston, Department of Biology and Biochemistry, Houston, Texas (JJW, PHG) and Feinberg School of Medicine, Northwestern University, Department of Medicine, Chicago, Illinois (STR)
| | - Cristian Coarfa
- Northwestern University, Robert H. Lurie Comprehensive Cancer Center, Chicago, Illinois (ALT, JQ, NLK, STR); Baylor College of Medicine, Department of Molecular and Human Genetics, Houston, Texas (CC, JJW, KR); University of Houston, Department of Biology and Biochemistry, Houston, Texas (JJW, PHG) and Feinberg School of Medicine, Northwestern University, Department of Medicine, Chicago, Illinois (STR)
| | - Jun Qian
- Northwestern University, Robert H. Lurie Comprehensive Cancer Center, Chicago, Illinois (ALT, JQ, NLK, STR); Baylor College of Medicine, Department of Molecular and Human Genetics, Houston, Texas (CC, JJW, KR); University of Houston, Department of Biology and Biochemistry, Houston, Texas (JJW, PHG) and Feinberg School of Medicine, Northwestern University, Department of Medicine, Chicago, Illinois (STR)
| | - Joseph J Wilkerson
- Northwestern University, Robert H. Lurie Comprehensive Cancer Center, Chicago, Illinois (ALT, JQ, NLK, STR); Baylor College of Medicine, Department of Molecular and Human Genetics, Houston, Texas (CC, JJW, KR); University of Houston, Department of Biology and Biochemistry, Houston, Texas (JJW, PHG) and Feinberg School of Medicine, Northwestern University, Department of Medicine, Chicago, Illinois (STR)
| | - Kimal Rajapakshe
- Northwestern University, Robert H. Lurie Comprehensive Cancer Center, Chicago, Illinois (ALT, JQ, NLK, STR); Baylor College of Medicine, Department of Molecular and Human Genetics, Houston, Texas (CC, JJW, KR); University of Houston, Department of Biology and Biochemistry, Houston, Texas (JJW, PHG) and Feinberg School of Medicine, Northwestern University, Department of Medicine, Chicago, Illinois (STR)
| | - Nancy L Krett
- Northwestern University, Robert H. Lurie Comprehensive Cancer Center, Chicago, Illinois (ALT, JQ, NLK, STR); Baylor College of Medicine, Department of Molecular and Human Genetics, Houston, Texas (CC, JJW, KR); University of Houston, Department of Biology and Biochemistry, Houston, Texas (JJW, PHG) and Feinberg School of Medicine, Northwestern University, Department of Medicine, Chicago, Illinois (STR)
| | - Preethi H Gunaratne
- Northwestern University, Robert H. Lurie Comprehensive Cancer Center, Chicago, Illinois (ALT, JQ, NLK, STR); Baylor College of Medicine, Department of Molecular and Human Genetics, Houston, Texas (CC, JJW, KR); University of Houston, Department of Biology and Biochemistry, Houston, Texas (JJW, PHG) and Feinberg School of Medicine, Northwestern University, Department of Medicine, Chicago, Illinois (STR)
| | - Steven T Rosen
- Northwestern University, Robert H. Lurie Comprehensive Cancer Center, Chicago, Illinois (ALT, JQ, NLK, STR); Baylor College of Medicine, Department of Molecular and Human Genetics, Houston, Texas (CC, JJW, KR); University of Houston, Department of Biology and Biochemistry, Houston, Texas (JJW, PHG) and Feinberg School of Medicine, Northwestern University, Department of Medicine, Chicago, Illinois (STR)
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20
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Peters JM, Gonzalez FJ, Müller R. Establishing the Role of PPARβ/δ in Carcinogenesis. Trends Endocrinol Metab 2015; 26:595-607. [PMID: 26490384 PMCID: PMC4631629 DOI: 10.1016/j.tem.2015.09.004] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Revised: 09/10/2015] [Accepted: 09/12/2015] [Indexed: 12/16/2022]
Abstract
The role of the nuclear hormone receptor peroxisome proliferator-activated receptor β/δ (PPARβ/δ) in carcinogenesis is controversial because conflicting studies indicate that it both inhibits and promotes tumorigenesis. In this review, we focus on recent studies on PPARβ/δ including the significance of increased or decreased PPARβ/δ expression in cancers; a range of opposing mechanisms describing how PPARβ/δ agonists, antagonists, and inverse agonists regulate tumorigenesis and/or whether there may be cell context-specific mechanisms; and whether activating or inhibiting PPARβ/δ is feasible for cancer chemoprevention and/or therapy. Research questions that need to be addressed are highlighted to establish whether PPARβ/δ can be effectively targeted for cancer chemoprevention.
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Affiliation(s)
- Jeffrey M Peters
- Department of Veterinary and Biomedical Sciences and The Center of Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, PA 16802, USA.
| | - Frank J Gonzalez
- Laboratory of Metabolism, National Cancer Institute, Bethesda, MD 20892, USA
| | - Rolf Müller
- Institute of Molecular Biology and Tumor Research, Center for Tumor Biology and Immunology, Philipps University, Hans-Meerwein-Straße 3, 35043 Marburg, Germany
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21
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DNA methylation of oestrogen-regulated enhancers defines endocrine sensitivity in breast cancer. Nat Commun 2015; 6:7758. [PMID: 26169690 PMCID: PMC4510968 DOI: 10.1038/ncomms8758] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Accepted: 06/06/2015] [Indexed: 12/15/2022] Open
Abstract
Expression of oestrogen receptor (ESR1) determines whether a breast cancer patient receives endocrine therapy, but does not guarantee patient response. The molecular factors that define endocrine response in ESR1-positive breast cancer patients remain poorly understood. Here we characterize the DNA methylome of endocrine sensitivity and demonstrate the potential impact of differential DNA methylation on endocrine response in breast cancer. We show that DNA hypermethylation occurs predominantly at oestrogen-responsive enhancers and is associated with reduced ESR1 binding and decreased gene expression of key regulators of ESR1 activity, thus providing a novel mechanism by which endocrine response is abated in ESR1-positive breast cancers. Conversely, we delineate that ESR1-responsive enhancer hypomethylation is critical in transition from normal mammary epithelial cells to endocrine-responsive ESR1-positive cancer. Cumulatively, these novel insights highlight the potential of ESR1-responsive enhancer methylation to both predict ESR1-positive disease and stratify ESR1-positive breast cancer patients as responders to endocrine therapy. The molecular factors influencing patient response to endocrine therapy are poorly understood. Here Stone et al. characterize the DNA methylome of endocrine response and show that methylation of oestrogen receptor-associated enhancers underpins endocrine sensitivity in human breast cancer.
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22
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Makkonen H, Palvimo JJ. Androgen receptor: acting in the three-dimensional chromatin landscape of prostate cancer cells. Horm Mol Biol Clin Investig 2015; 5:17-26. [PMID: 25961240 DOI: 10.1515/hmbci.2010.055] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Accepted: 10/05/2010] [Indexed: 01/08/2023]
Abstract
Androgen receptor (AR) acts as a hormone-controlled transcription factor that conveys the messages of both natural and synthetic androgens to the level of genes and gene programs. Defective AR signaling leads to a wide array of androgen insensitivity disorders, and deregulated AR function, in particular overexpression of AR, is involved in the growth and progression of prostate cancer. Classic models of AR action view AR-binding sites as upstream regulatory elements in gene promoters or their proximity. However, recent wider genomic screens indicate that AR target genes are commonly activated through very distal chromatin-binding sites. This highlights the importance of long-range chromatin regulation of transcription by the AR, shifting the focus from the linear gene models to three-dimensional models of AR target genes and gene programs. The capability of AR to regulate promoters from long distances in the chromatin is particularly important when evaluating the role of AR in the regulation of genes in malignant prostate cells that frequently show striking genomic aberrations, especially gene fusions. Therefore, in addition to the mechanisms of DNA loop formation between the enhancer bound ARs and the transcription apparatus at the target core promoter, the mechanisms insulating distally bound ARs from promiscuously making contacts and activating other than their normal target gene promoters are critical for proper physiological regulation and thus currently under intense investigation. This review discusses the current knowledge about the AR action in the context of gene aberrations and the three-dimensional chromatin landscape of prostate cancer cells.
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23
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Borland MG, Krishnan P, Lee C, Albrecht PP, Shan W, Bility MT, Marcus CB, Lin JM, Amin S, Gonzalez FJ, Perdew GH, Peters JM. Modulation of aryl hydrocarbon receptor (AHR)-dependent signaling by peroxisome proliferator-activated receptor β/δ (PPARβ/δ) in keratinocytes. Carcinogenesis 2014; 35:1602-12. [PMID: 24639079 PMCID: PMC4076811 DOI: 10.1093/carcin/bgu067] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Revised: 02/26/2014] [Accepted: 03/10/2014] [Indexed: 12/11/2022] Open
Abstract
Whether peroxisome proliferator-activated receptor β/δ (PPARβ/δ) reduces skin tumorigenesis by altering aryl hydrocarbon receptor (AHR)-dependent activities was examined. Polycyclic aromatic hydrocarbons (PAH) increased expression of cytochrome P4501A1 (CYP1A1), CYP1B1 and phase II xenobiotic metabolizing enzymes in wild-type skin and keratinocytes. Surprisingly, this effect was not found in Pparβ/δ-null skin and keratinocytes. Pparβ/δ-null keratinocytes exhibited decreased AHR occupancy and histone acetylation on the Cyp1a1 promoter in response to a PAH compared with wild-type keratinocytes. Bisulfite sequencing of the Cyp1a1 promoter and studies using a DNA methylation inhibitor suggest that PPARβ/δ promotes demethylation of the Cyp1a1 promoter. Experiments with human HaCaT keratinocytes stably expressing shRNA against PPARβ/δ also support this conclusion. Consistent with the lower AHR-dependent activities in Pparβ/δ-null mice compared with wild-type mice, 7,12-dimethylbenz[a]anthracene (DMBA)-induced skin tumorigenesis was inhibited in Pparβ/δ-null mice compared with wild-type. Results from these studies demonstrate that PPARβ/δ is required to mediate complete carcinogenesis by DMBA. The mechanisms underlying this PPARβ/δ-dependent reduction of AHR signaling by PAH are not due to alterations in the expression of AHR auxiliary proteins, ligand binding or AHR nuclear translocation between genotypes, but are likely influenced by PPARβ/δ-dependent demethylation of AHR target gene promoters including Cyp1a1 that reduces AHR accessibility as shown by reduced promoter occupancy. This PPARβ/δ/AHR crosstalk is unique to keratinocytes and conserved between mice and humans.
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MESH Headings
- 9,10-Dimethyl-1,2-benzanthracene/toxicity
- Animals
- Basic Helix-Loop-Helix Transcription Factors/physiology
- Blotting, Western
- Carcinogens/toxicity
- Cell Transformation, Neoplastic/chemically induced
- Cell Transformation, Neoplastic/metabolism
- Cell Transformation, Neoplastic/pathology
- Cells, Cultured
- Chromatin Immunoprecipitation
- Dermis/cytology
- Dermis/metabolism
- Female
- Fibroblasts/cytology
- Fibroblasts/metabolism
- Humans
- Immunoenzyme Techniques
- Keratinocytes/cytology
- Keratinocytes/metabolism
- Mice
- Mice, Knockout
- PPAR delta/physiology
- PPAR-beta/physiology
- RNA, Messenger/genetics
- Real-Time Polymerase Chain Reaction
- Receptors, Aryl Hydrocarbon/physiology
- Reverse Transcriptase Polymerase Chain Reaction
- Signal Transduction
- Skin Neoplasms/chemically induced
- Skin Neoplasms/metabolism
- Skin Neoplasms/pathology
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Affiliation(s)
- Michael G Borland
- Department of Veterinary and Biomedical Sciences and the Center of Molecular Toxicology and Carcinogenesis and The Graduate Program in Biochemistry, Microbiology, and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA
| | - Prasad Krishnan
- Department of Veterinary and Biomedical Sciences and the Center of Molecular Toxicology and Carcinogenesis and
| | - Christina Lee
- Department of Veterinary and Biomedical Sciences and the Center of Molecular Toxicology and Carcinogenesis and
| | - Prajakta P Albrecht
- Department of Veterinary and Biomedical Sciences and the Center of Molecular Toxicology and Carcinogenesis and
| | - Weiwei Shan
- Department of Veterinary and Biomedical Sciences and the Center of Molecular Toxicology and Carcinogenesis and
| | - Moses T Bility
- Department of Veterinary and Biomedical Sciences and the Center of Molecular Toxicology and Carcinogenesis and
| | - Craig B Marcus
- Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, OR 97331, USA
| | - Jyh M Lin
- Department of Pharmacology, Penn State Cancer Institute, The Pennsylvania State University, Milton S. Hershey Medical Center, Hershey, PA 17033, USA and
| | - Shantu Amin
- Department of Pharmacology, Penn State Cancer Institute, The Pennsylvania State University, Milton S. Hershey Medical Center, Hershey, PA 17033, USA and
| | - Frank J Gonzalez
- Laboratory of Metabolism, National Cancer Institute, Bethesda, MD 20892, USA
| | - Gary H Perdew
- Department of Veterinary and Biomedical Sciences and the Center of Molecular Toxicology and Carcinogenesis and The Graduate Program in Biochemistry, Microbiology, and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA
| | - Jeffrey M Peters
- Department of Veterinary and Biomedical Sciences and the Center of Molecular Toxicology and Carcinogenesis and The Graduate Program in Biochemistry, Microbiology, and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA,
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24
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Electrophilic lipid mediator 15-deoxy-Δ12,14-prostaglandin j2 modifies glucocorticoid signaling via receptor SUMOylation. Mol Cell Biol 2014; 34:3202-13. [PMID: 24980431 DOI: 10.1128/mcb.00748-14] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Cortisol, the central stress hormone in humans, activates the glucocorticoid receptor (GR). Anti-inflammatory effects are the most important pharmaceutical effects mediated by the GR. Inasmuch as electrophilic cyclopentenone prostaglandin 15-deoxy-Δ(12,14)-prostaglandin J2 (15d-PGJ2) has potent anti-inflammatory properties and activates the SUMOylation pathway, we have investigated the effect of 15d-PGJ2 on glucocorticoid signaling and receptor SUMOylation. To this end, we studied isogenic HEK293 cells expressing either wild-type GR or SUMOylation-defective GR. Interestingly, 15d-PGJ2 triggered SUMO-2 and -3 (SUMO-2/3) modification in the primary SUMOylation sites of the GR. Gene expression profiling and pathway analyses indicate that 15d-PGJ2 inhibits GR signaling in a genome-wide fashion that is significantly dependent on the GR SUMOylation sites. Chromatin immunoprecipitation assays showed that the repressive effect of 15d-PGJ2 on GR target gene expression occurs in parallel with the inhibition of receptor binding to the target gene chromatin. Furthermore, depletion of UBC9, the sole SUMO E2 conjugase, from HEK293 cells confirmed the involvement of active SUMOylation in the regulatory process. Taken together, our data indicate that GR SUMOylation modulates the glucocorticoid signaling during acute cell stress. Our data also suggest that GR SUMOylation modulates cross talk of the glucocorticoid signaling with other transcription factors that are responsive to cell stress.
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25
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Patani N, Martin LA. Understanding response and resistance to oestrogen deprivation in ER-positive breast cancer. Mol Cell Endocrinol 2014; 382:683-694. [PMID: 24121024 DOI: 10.1016/j.mce.2013.09.038] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Revised: 09/30/2013] [Accepted: 09/30/2013] [Indexed: 01/01/2023]
Abstract
Oestrogens (E) and oestrogen receptor alpha (ERα) play fundamental roles in the development and progression of more than three-quarters of breast cancers (BC). The ability to influence the natural history of BC by hormonal manipulation is well established and endocrine therapies represent the cornerstone of systemic management for women with ERα-positive disease. Endocrine agents abrogate oestrogenic signalling through distinct and incompletely overlapping mechanisms, either impeding the transcriptional activity of ERα or diminishing E-synthesis. In post-menopausal women, E-production is chiefly attributable to the enzymatic conversion of androgens in extra-gonadal tissues by the cytochrome P-450 superfamily member aromatase. Greater understanding of steroid biosynthesis has underpinned rational drug design and pharmacological development of potent and specific aromatase inhibitors (AIs). Contemporary agents induce profound E-suppression in post-menopausal women and are first-line neo-adjuvant, adjuvant and metastatic therapies, with greater efficacy and tolerability than tamoxifen. The principal qualifier for endocrine treatment, including AIs, remains ERα expression. However, it is increasingly apparent that ERα expression is not synonymous with sensitivity to treatment and insufficient to account for the considerable heterogeneity of response. Better predictive biomarkers of de novo resistance are required to improve patient selection and identify those poor-responders who may benefit from alternative or additional systemic treatment from the outset. Among patients who do respond well initially, many relapse during their clinical course and there is also an unmet need for biomarkers of acquired resistance. The majority of women who relapse on AIs continue to express functional ERα which remains a legitimate target for second-line endocrine therapy. Understanding and overcoming acquired resistance to AIs requires a greater appreciation of ERα biology and the mechanisms though which E-dependence can be subverted. In this article, we review the impact of therapeutic E-deprivation on the natural history of ERα-positive breast cancer. Consideration is given to established and emerging biomarkers and/or determinants of response and resistance to E-deprivation. In vitro and in vivo evidence of the molecular mechanisms underpinning the transition from sensitivity to resistance are reviewed in the context of current models of ERα activity and their potential translational relevance.
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Affiliation(s)
- N Patani
- Academic Department of Biochemistry, Royal Marsden Foundation Trust, London, UK; Breakthrough Breast Cancer Research Centre, Institute of Cancer Research, London SW3 6JB, UK
| | - L-A Martin
- Breakthrough Breast Cancer Research Centre, Institute of Cancer Research, London SW3 6JB, UK.
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26
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Morris SA, Baek S, Sung MH, John S, Wiench M, Johnson TA, Schiltz RL, Hager GL. Overlapping chromatin-remodeling systems collaborate genome wide at dynamic chromatin transitions. Nat Struct Mol Biol 2013; 21:73-81. [PMID: 24317492 PMCID: PMC3947387 DOI: 10.1038/nsmb.2718] [Citation(s) in RCA: 115] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Accepted: 10/17/2013] [Indexed: 12/24/2022]
Abstract
ATP-dependent chromatin remodeling is an essential process required for the dynamic organization of chromatin structure. Here we describe the genome-wide location and activity of three remodeler proteins with diverse physiological functions in the mouse genome: Brg1, Chd4, and Snf2h. The localization patterns of all three proteins significantly overlap with one another and with regions of accessible chromatin. Furthermore, using inducible mutant variants, we demonstrate that the catalytic activity of these proteins contributes to the remodeling of chromatin genome-wide, and that each of these remodelers can independently regulate chromatin reorganization at distinct sites. Many regions require the activity of more than one remodeler to regulate accessibility. These findings provide a dynamic view of chromatin organization, and highlight the differential contributions of remodelers to chromatin maintenance in higher eukaryotes.
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Affiliation(s)
- Stephanie A Morris
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Songjoon Baek
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Myong-Hee Sung
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Sam John
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Malgorzata Wiench
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Thomas A Johnson
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - R Louis Schiltz
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Gordon L Hager
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
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27
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Ratman D, Vanden Berghe W, Dejager L, Libert C, Tavernier J, Beck IM, De Bosscher K. How glucocorticoid receptors modulate the activity of other transcription factors: a scope beyond tethering. Mol Cell Endocrinol 2013; 380:41-54. [PMID: 23267834 DOI: 10.1016/j.mce.2012.12.014] [Citation(s) in RCA: 279] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Revised: 12/13/2012] [Accepted: 12/16/2012] [Indexed: 01/11/2023]
Abstract
The activity of the glucocorticoid receptor (GR), a nuclear receptor transcription factor belonging to subclass 3C of the steroid/thyroid hormone receptor superfamily, is typically triggered by glucocorticoid hormones. Apart from driving gene transcription via binding onto glucocorticoid response elements in regulatory regions of particular target genes, GR can also inhibit gene expression via transrepression, a mechanism largely based on protein:protein interactions. Hereby GR can influence the activity of other transcription factors, without contacting DNA itself. GR is known to inhibit the activity of a growing list of immune-regulating transcription factors. Hence, GCs still rule the clinic for treatments of inflammatory disorders, notwithstanding concomitant deleterious side effects. Although patience is a virtue when it comes to deciphering the many mechanisms GR uses to influence various signaling pathways, the current review is testimony of the fact that groundbreaking mechanistic work has been accumulating over the past years and steadily continues to grow.
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Affiliation(s)
- Dariusz Ratman
- Cytokine Receptor Lab, VIB Department of Medical Protein Research, VIB, UGent, Albert Baertsoenkaai 3, B-9000 Gent, Belgium.
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28
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Corton JC, Cunningham ML, Hummer BT, Lau C, Meek B, Peters JM, Popp JA, Rhomberg L, Seed J, Klaunig JE. Mode of action framework analysis for receptor-mediated toxicity: The peroxisome proliferator-activated receptor alpha (PPARα) as a case study. Crit Rev Toxicol 2013; 44:1-49. [PMID: 24180432 DOI: 10.3109/10408444.2013.835784] [Citation(s) in RCA: 161] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Several therapeutic agents and industrial chemicals induce liver tumors in rodents through the activation of the peroxisome proliferator-activated receptor alpha (PPARα). The cellular and molecular events by which PPARα activators induce rodent hepatocarcinogenesis has been extensively studied and elucidated. This review summarizes the weight of evidence relevant to the hypothesized mode of action (MOA) for PPARα activator-induced rodent hepatocarcinogenesis and identifies gaps in our knowledge of this MOA. Chemical-specific and mechanistic data support concordance of temporal and dose-response relationships for the key events associated with many PPARα activators including a phthalate ester plasticizer di(2-ethylhexyl) phthalate (DEHP) and the drug gemfibrozil. While biologically plausible in humans, the hypothesized key events in the rodent MOA, for PPARα activators, are unlikely to induce liver tumors in humans because of toxicodynamic and biological differences in responses. This conclusion is based on minimal or no effects observed on growth pathways, hepatocellular proliferation and liver tumors in humans and/or species (including hamsters, guinea pigs and cynomolgous monkeys) that are more appropriate human surrogates than mice and rats at overlapping dose levels. Overall, the panel concluded that significant quantitative differences in PPARα activator-induced effects related to liver cancer formation exist between rodents and humans. On the basis of these quantitative differences, most of the workgroup felt that the rodent MOA is "not relevant to humans" with the remaining members concluding that the MOA is "unlikely to be relevant to humans". The two groups differed in their level of confidence based on perceived limitations of the quantitative and mechanistic knowledge of the species differences, which for some panel members strongly supports but cannot preclude the absence of effects under unlikely exposure scenarios.
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29
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Luo M, Lu X, Zhu R, Zhang Z, Chow CC, Li R, Simons SS. A conserved protein motif is required for full modulatory activity of negative elongation factor subunits NELF-A and NELF-B in modifying glucocorticoid receptor-regulated gene induction properties. J Biol Chem 2013; 288:34055-34072. [PMID: 24097989 DOI: 10.1074/jbc.m113.512426] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
NELF-B is a BRCA1-interacting protein and subunit (with NELF-A, -C/D, and -E) of the human negative elongation factor (NELF) complex, which participates in RNA polymerase II pausing shortly after transcription initiation, especially for synchronized gene expression. We now report new activities of NELF-B and other NELF complex subunits, which are to attenuate glucocorticoid receptor (GR)-mediated gene induction, reduce the partial agonist activity of an antagonist, and increase the EC50 of an agonist during nonsynchronized expression of exogenous and endogenous reporters. Stable knockdown of endogenous NELF-B has the opposite effects on an exogenous gene. The GR ligand-binding domain suffices for these biological responses. ChIP assays reveal that NELF-B diminishes GR recruitment to promoter regions of two endogenous genes. Using a new competition assay, NELF-A and NELF-B are each shown to act independently as competitive decelerators at two steps after the site of GR action and before or at the site of reporter gene activity. A common motif in each NELF was identified that is required for full activity of both NELF-A and NELF-B. These studies allow us to position the actions of two new modulators of GR-regulated transactivation, NELF-A and NELF-B, relative to other factors in the overall gene induction sequence.
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Affiliation(s)
- Min Luo
- Steroid Hormones Section, NIDDK/Laboratory of Endocrinology and Receptor Biology (LERB), National Institutes of Health, Bethesda, Maryland 20892
| | - Xinping Lu
- Steroid Hormones Section, NIDDK/Laboratory of Endocrinology and Receptor Biology (LERB), National Institutes of Health, Bethesda, Maryland 20892
| | - Rong Zhu
- Steroid Hormones Section, NIDDK/Laboratory of Endocrinology and Receptor Biology (LERB), National Institutes of Health, Bethesda, Maryland 20892
| | - Zhenhuan Zhang
- Steroid Hormones Section, NIDDK/Laboratory of Endocrinology and Receptor Biology (LERB), National Institutes of Health, Bethesda, Maryland 20892
| | - Carson C Chow
- Laboratory of Biological Modeling, NIDDK, National Institutes of Health, Bethesda, Maryland 20892
| | - Rong Li
- Cancer Therapy and Research Center, University of Texas Health Science Center, San Antonio, Texas 78229
| | - S Stoney Simons
- Steroid Hormones Section, NIDDK/Laboratory of Endocrinology and Receptor Biology (LERB), National Institutes of Health, Bethesda, Maryland 20892.
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30
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Treviño LS, Weigel NL. Phosphorylation: a fundamental regulator of steroid receptor action. Trends Endocrinol Metab 2013; 24:515-24. [PMID: 23838532 PMCID: PMC3783573 DOI: 10.1016/j.tem.2013.05.008] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Revised: 05/21/2013] [Accepted: 05/29/2013] [Indexed: 12/23/2022]
Abstract
Steroid hormone receptors (SHRs) are hormone-activated transcription factors involved in numerous cellular functions and in health and disease. Their activities depend on the cellular level of the receptor, the presence of coregulator proteins, and the cell signaling pathways that are active in the cell. SHRs and their coregulators are phosphorylated on multiple sites by a wide variety of kinases. Each site may contribute to multiple functions and the net effect of an individual phosphorylation depends on the activating kinase. Here we discuss functions of known SHR phosphorylation sites, kinase regulation, evidence of translational relevance, and crosstalk between SHRs and cell signaling pathways. Understanding how cell signaling pathways regulate SHRs might yield novel therapeutic targets for multiple human diseases.
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Affiliation(s)
- Lindsey S Treviño
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030, USA
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31
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Rousseau GG. Fifty years ago: the quest for steroid hormone receptors. Mol Cell Endocrinol 2013; 375:10-3. [PMID: 23684885 DOI: 10.1016/j.mce.2013.05.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Revised: 04/29/2013] [Accepted: 05/07/2013] [Indexed: 01/18/2023]
Abstract
In 1963 Peter Karlson put forward the revolutionary "hormone-gene" hypothesis, which would change drastically the way in which steroid hormones were thought to act at the time. From a historical perspective, this review relates the acceptance of this initially controversial idea, the discovery of the steroid receptors and the key experiments that have led to the current understanding of the mechanism of steroid hormone action. It shows how, over 50years, the field has widened beyond all expectation and has contributed to major advances not only in endocrinology, but also in molecular biology, pharmacology and therapeutics.
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Affiliation(s)
- Guy G Rousseau
- de Duve Institute and Université Catholique de Louvain, Brussels, Belgium.
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32
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Auvinen HE, Wang Y, Princen H, Romijn JA, Havekes LM, Smit JWA, Meijer OC, Biermasz NR, Rensen PCN, Pereira AM. Both transient and continuous corticosterone excess inhibit atherosclerotic plaque formation in APOE*3-leiden.CETP mice. PLoS One 2013; 8:e63882. [PMID: 23717502 PMCID: PMC3661690 DOI: 10.1371/journal.pone.0063882] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Accepted: 04/09/2013] [Indexed: 01/28/2023] Open
Abstract
Introduction The role of glucocorticoids in atherosclerosis development is not clearly established. Human studies show a clear association between glucocorticoid excess and cardiovascular disease, whereas most animal models indicate an inhibitory effect of glucocorticoids on atherosclerosis development. These animal models, however, neither reflect long-term glucocorticoid overexposure nor display human-like lipoprotein metabolism. Aim To investigate the effects of transient and continuous glucocorticoid excess on atherosclerosis development in a mouse model with human-like lipoprotein metabolism upon feeding a Western-type diet. Methods Pair-housed female APOE*3-Leiden.CETP (E3L.CETP) mice fed a Western-type containing 0.1% cholesterol for 20 weeks were given corticosterone (50 µg/ml) for either 5 (transient group) or 17 weeks (continuous group), or vehicle (control group) in the drinking water. At the end of the study, atherosclerosis severity, lesion area in the aortic root, the number of monocytes adhering to the endothelial wall and macrophage content of the plaque were measured. Results Corticosterone treatment increased body weight and food intake for the duration of the treatment and increased gonadal and subcutaneous white adipose tissue weight in transient group by +35% and +31%, and in the continuous group by +140% and 110%. Strikingly, both transient and continuous corticosterone treatment decreased total atherosclerotic lesion area by −39% without lowering plasma cholesterol levels. In addition, there was a decrease of −56% in macrophage content of the plaque with continuous corticosterone treatment, and a similar trend was present with the transient treatment. Conclusion Increased corticosterone exposure in mice with human-like lipoprotein metabolism has beneficial, long-lasting effects on atherosclerosis, but negatively affects body fat distribution by promoting fat accumulation in the long-term. This indicates that the increased atherosclerosis observed in humans in states of glucocorticoid excess may not be related to cortisol per se, but might be the result of complex indirect effects of cortisol.
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Affiliation(s)
- Hanna E Auvinen
- Department of Endocrinology and Metabolic Diseases, Leiden University Medical Center, Leiden, The Netherlands.
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33
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Grøntved L, John S, Baek S, Liu Y, Buckley JR, Vinson C, Aguilera G, Hager GL. C/EBP maintains chromatin accessibility in liver and facilitates glucocorticoid receptor recruitment to steroid response elements. EMBO J 2013; 32:1568-83. [PMID: 23665916 DOI: 10.1038/emboj.2013.106] [Citation(s) in RCA: 169] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Accepted: 04/10/2013] [Indexed: 01/22/2023] Open
Abstract
Mechanisms regulating transcription factor interaction with chromatin in intact mammalian tissues are poorly understood. Exploiting an adrenalectomized mouse model with depleted endogenous glucocorticoids, we monitor changes of the chromatin landscape in intact liver tissue following glucocorticoid injection. Upon activation of the glucocorticoid receptor (GR), proximal regions of activated and repressed genes are remodelled, and these remodelling events correlate with RNA polymerase II occupancy of regulated genes. GR is exclusively associated with accessible chromatin and 62% percent of GR-binding sites are occupied by C/EBPβ. At the majority of these sites, chromatin is preaccessible suggesting a priming function of C/EBPβ for GR recruitment. Disruption of C/EBPβ binding to chromatin results in attenuation of pre-programmed chromatin accessibility, GR recruitment and GR-induced chromatin remodelling specifically at sites co-occupied by GR and C/EBPβ. Collectively, we demonstrate a highly cooperative mechanism by which C/EBPβ regulates selective GR binding to the genome in liver tissue. We suggest that selective targeting of GR in other tissues is likely mediated by the combined action of cell-specific priming proteins and chromatin remodellers.
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Affiliation(s)
- Lars Grøntved
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, NIH, Bethesda, MD 20892, USA
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34
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Stanczyk FZ, Hapgood JP, Winer S, Mishell DR. Progestogens used in postmenopausal hormone therapy: differences in their pharmacological properties, intracellular actions, and clinical effects. Endocr Rev 2013; 34:171-208. [PMID: 23238854 PMCID: PMC3610676 DOI: 10.1210/er.2012-1008] [Citation(s) in RCA: 280] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The safety of progestogens as a class has come under increased scrutiny after the publication of data from the Women's Health Initiative trial, particularly with respect to breast cancer and cardiovascular disease risk, despite the fact that only one progestogen, medroxyprogesterone acetate, was used in this study. Inconsistency in nomenclature has also caused confusion between synthetic progestogens, defined here by the term progestin, and natural progesterone. Although all progestogens by definition have progestational activity, they also have a divergent range of other properties that can translate to very different clinical effects. Endometrial protection is the primary reason for prescribing a progestogen concomitantly with postmenopausal estrogen therapy in women with a uterus, but several progestogens are known to have a range of other potentially beneficial effects, for example on the nervous and cardiovascular systems. Because women remain suspicious of the progestogen component of postmenopausal hormone therapy in the light of the Women's Health Initiative trial, practitioners should not ignore the potential benefits to their patients of some progestogens by considering them to be a single pharmacological class. There is a lack of understanding of the differences between progestins and progesterone and between individual progestins differing in their effects on the cardiovascular and nervous systems, the breast, and bone. This review elucidates the differences between the substantial number of individual progestogens employed in postmenopausal hormone therapy, including both progestins and progesterone. We conclude that these differences in chemical structure, metabolism, pharmacokinetics, affinity, potency, and efficacy via steroid receptors, intracellular action, and biological and clinical effects confirm the absence of a class effect of progestogens.
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Affiliation(s)
- Frank Z Stanczyk
- Department of Obstetrics and Gynecology, University of Southern California Keck School of Medicine, Livingston Research Building, 1321 North Mission Road, Room 201, Los Angeles, California 90033, USA.
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35
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Al Tanoury Z, Piskunov A, Rochette-Egly C. Vitamin A and retinoid signaling: genomic and nongenomic effects. J Lipid Res 2013; 54:1761-75. [PMID: 23440512 DOI: 10.1194/jlr.r030833] [Citation(s) in RCA: 262] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Vitamin A or retinol is arguably the most multifunctional vitamin in the human body, as it is essential from embryogenesis to adulthood. The pleiotropic effects of vitamin A are exerted mainly by one active metabolite, all-trans retinoic acid (atRA), which regulates the expression of a battery of target genes through several families of nuclear receptors (RARs, RXRs, and PPARβ/δ), polymorphic retinoic acid (RA) response elements, and multiple coregulators. It also involves extranuclear and nontranscriptional effects, such as the activation of kinase cascades, which are integrated in the nucleus via the phosphorylation of several actors of RA signaling. However, vitamin A itself proved recently to be active and RARs to be present in the cytosol to regulate translation and cell plasticity. These new concepts expand the scope of the biologic functions of vitamin A and RA.
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Affiliation(s)
- Ziad Al Tanoury
- Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Institut National de la Santé et de la Recherche Médicale (INSERM), U964, CNRS, UMR7104, Université de Strasbourg, 67404 Illkirch Cedex, France
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Hakim O, Sung MH, Nakayamada S, Voss TC, Baek S, Hager GL. Spatial congregation of STAT binding directs selective nuclear architecture during T-cell functional differentiation. Genome Res 2012; 23:462-72. [PMID: 23212947 PMCID: PMC3589535 DOI: 10.1101/gr.147652.112] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Higher-order genome organization shows tissue-specific patterns. However, functional relevance and the mechanisms shaping the genome architecture are poorly understood. Here we report a profound shift from promiscuous to highly selective genome organization that accompanies the effector lineage choice of differentiating T cells. As multipotent naive cells receive antigenic signals and commit to a T helper (Th) pathway, the genome-wide contacts of a lineage-specific cytokine locus are preferentially enriched for functionally relevant genes. Despite the establishment of divergent interactomes and global reprogramming of transcription in Th1 versus Th2, the overall expression status of the contact genes is surprisingly similar between the two lineages. Importantly, during differentiation, the genomic contacts are retained and strengthened precisely at DNA binding sites of the specific lineage-determining STAT transcription factor. In cells from the specific STAT knock-out mouse, the signature cytokine locus is unable to shed the promiscuous contacts established in the naive T cells, indicating the importance of genomic STAT binding. Altogether, the global aggregation of STAT binding loci from genic and nongenic regions highlights a new role for differentiation-promoting transcription factors in direct specification of higher-order nuclear architecture through interacting with regulatory regions. Such subnuclear environments have significant implications for efficient functioning of the mature effector lymphocytes.
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Affiliation(s)
- Ofir Hakim
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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37
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Khozoie C, Borland MG, Zhu B, Baek S, John S, Hager GL, Shah YM, Gonzalez FJ, Peters JM. Analysis of the peroxisome proliferator-activated receptor-β/δ (PPARβ/δ) cistrome reveals novel co-regulatory role of ATF4. BMC Genomics 2012; 13:665. [PMID: 23176727 PMCID: PMC3556323 DOI: 10.1186/1471-2164-13-665] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Accepted: 11/22/2012] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND The present study coupled expression profiling with chromatin immunoprecipitation sequencing (ChIP-seq) to examine peroxisome proliferator-activated receptor-β/δ (PPARβ/δ)-dependent regulation of gene expression in mouse keratinocytes, a cell type that expresses PPARβ/δ in high concentration. RESULTS Microarray analysis elucidated eight different types of regulation that modulated PPARβ/δ-dependent gene expression of 612 genes ranging from repression or activation without an exogenous ligand, repression or activation with an exogenous ligand, or a combination of these effects. Bioinformatic analysis of ChIP-seq data demonstrated promoter occupancy of PPARβ/δ for some of these genes, and also identified the presence of other transcription factor binding sites in close proximity to PPARβ/δ bound to chromatin. For some types of regulation, ATF4 is required for ligand-dependent induction of PPARβ/δ target genes. CONCLUSIONS PPARβ/δ regulates constitutive expression of genes in keratinocytes, thus suggesting the presence of one or more endogenous ligands. The diversity in the types of gene regulation carried out by PPARβ/δ is consistent with dynamic binding and interactions with chromatin and indicates the presence of complex regulatory networks in cells expressing high levels of this nuclear receptor such as keratinocytes. Results from these studies are the first to demonstrate that differences in DNA binding of other transcription factors can directly influence the transcriptional activity of PPARβ/δ.
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Affiliation(s)
- Combiz Khozoie
- Department of Veterinary and Biomedical Sciences and The Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Michael G Borland
- Department of Veterinary and Biomedical Sciences and The Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, PA, 16802, USA
- Present address: Department of Chemistry and Biochemistry, Bloomsburg University of Pennsylvania, Bloomsburg, PA, USA
| | - Bokai Zhu
- Department of Veterinary and Biomedical Sciences and The Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Songjoon Baek
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, Bethesda, MD, 20892, USA
| | - Sam John
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, Bethesda, MD, 20892, USA
- Present address: Genome Sciences, University of Washington, Seattle, WA, USA
| | - Gordon L Hager
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, Bethesda, MD, 20892, USA
| | - Yatrik M Shah
- Laboratory of Metabolism, National Cancer Institute, Bethesda, MD, 20892, USA
- Present address: Department of Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Frank J Gonzalez
- Laboratory of Metabolism, National Cancer Institute, Bethesda, MD, 20892, USA
| | - Jeffrey M Peters
- Department of Veterinary and Biomedical Sciences and The Center for Molecular Toxicology and Carcinogenesis, The Pennsylvania State University, University Park, PA, 16802, USA
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Blackford JA, Guo C, Zhu R, Dougherty EJ, Chow CC, Simons SS. Identification of location and kinetically defined mechanism of cofactors and reporter genes in the cascade of steroid-regulated transactivation. J Biol Chem 2012; 287:40982-95. [PMID: 23055525 DOI: 10.1074/jbc.m112.414805] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A currently obscure area of steroid hormone action is where the component factors, including receptor and reporter gene, act. The DNA binding of factors can be precisely defined, but the location and timing of factor binding and action are usually not equivalent. These questions are addressed for several factors (e.g. glucocorticoid receptor (GR), reporter, TIF2, NCoR, NELF-A, sSMRT, and STAMP) using our recently developed competition assay. This assay reveals both the kinetically defined mechanism of factor action and where the above factors act relative to both each other and the equilibrium equivalent to the rate-limiting step, which we call the concentration limiting step (CLS). The utility of this competition assay would be greatly increased if the position of the CLS is invariant and if the factor acting at the CLS is known. Here we report that the exogenous GREtkLUC reporter acts at the CLS as an accelerator for gene induction by GRs in U2OS cells. This mechanism of reporter function at the CLS persists with different reporters, factors, receptors, and cell types. We, therefore, propose that the reporter gene always acts at the CLS during gene induction and constitutes a landmark around which one can order the actions of all other factors. Current data suggest that how and where GR and the short form of SMRT act is also constant. These results validate a novel and rational methodology for identifying distally acting factors that would be attractive targets for pharmaceutical intervention in the treatment of diseases involving GR-regulated genes.
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Affiliation(s)
- John A Blackford
- Steroid Hormones Section, Laboratory of Endocrinology and Receptor Biology, NIDDK, National Institutes of Health, Bethesda, Maryland 20892, USA
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39
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Polman JAE, Welten JE, Bosch DS, de Jonge RT, Balog J, van der Maarel SM, de Kloet ER, Datson NA. A genome-wide signature of glucocorticoid receptor binding in neuronal PC12 cells. BMC Neurosci 2012; 13:118. [PMID: 23031785 PMCID: PMC3519639 DOI: 10.1186/1471-2202-13-118] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2012] [Accepted: 09/24/2012] [Indexed: 12/22/2022] Open
Abstract
Background Glucocorticoids, secreted by the adrenals in response to stress, profoundly affect structure and plasticity of neurons. Glucocorticoid action in neurons is mediated by glucocorticoid receptors (GR) that operate as transcription factors in the regulation of gene expression and either bind directly to genomic glucocorticoid response elements (GREs) or indirectly to the genome via interactions with bound transcription factors. These two modes of action, respectively called transactivation and transrepression, result in the regulation of a wide variety of genes important for neuronal function. The objective of the present study was to identify genome-wide glucocorticoid receptor binding sites in neuronal PC12 cells using Chromatin ImmunoPrecipitation combined with next generation sequencing (ChIP-Seq). Results In total we identified 1183 genomic binding sites of GR, the majority of which were novel and not identified in other ChIP-Seq studies on GR binding. More than half (58%) of the binding sites contained a GRE. The remaining 42% of the GBS did not harbour a GRE and therefore likely bind GR via an intermediate transcription factor tethering GR to the DNA. While the GRE-containing binding sites were more often located nearby genes involved in general cell functions and processes such as apoptosis, cell motion, protein dimerization activity and vasculature development, the binding sites without a GRE were located nearby genes with a clear role in neuronal processes such as neuron projection morphogenesis, neuron projection regeneration, synaptic transmission and catecholamine biosynthetic process. A closer look at the sequence of the GR binding sites revealed the presence of several motifs for transcription factors that are highly divergent from those previously linked to GR-signaling, including Gabpa, Prrx2, Zfp281, Gata1 and Zbtb3. These transcription factors may represent novel crosstalk partners of GR in a neuronal context. Conclusions Here we present the first genome-wide inventory of GR-binding sites in a neuronal context. These results provide an exciting first global view into neuronal GR targets and the neuron-specific modes of GR action and potentially contributes to our understanding of glucocorticoid action in the brain.
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Affiliation(s)
- J Annelies E Polman
- Division of Medical Pharmacology, Leiden/Amsterdam Center for Drug Research, Leiden University Medical Center, Leiden, 2333 CC, The Netherlands
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40
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Al-Sabbagh M, Lam EWF, Brosens JJ. Mechanisms of endometrial progesterone resistance. Mol Cell Endocrinol 2012; 358:208-15. [PMID: 22085558 DOI: 10.1016/j.mce.2011.10.035] [Citation(s) in RCA: 115] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Revised: 10/31/2011] [Accepted: 10/31/2011] [Indexed: 10/15/2022]
Abstract
Throughout the reproductive years, the rise and fall in ovarian hormones elicit in the endometrium waves of cell proliferation, differentiation, recruitment of inflammatory cells, apoptosis, tissue breakdown and regeneration. The activated progesterone receptor, a member of the superfamily of ligand-dependent transcription factors, is the master regulator of this intense tissue remodelling process in the uterus. Its activity is tightly regulated by interaction with cell-specific transcription factors and coregulators as well as by specific posttranslational modifications that respond dynamically to a variety of environmental and inflammatory signals. Endometriosis, a chronic inflammatory disorder, disrupts coordinated progesterone responses throughout the reproductive tract, including in the endometrium. This phenomenon is increasingly referred to as 'progesterone resistance'. Emerging evidence suggests that progesterone resistance in endometriosis is not just a consequence of perturbed progesterone signal transduction caused by chronic inflammation but associated with epigenetic chromatin changes that determine the intrinsic responsiveness of endometrial cells to differentiation cues.
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Affiliation(s)
- Marwa Al-Sabbagh
- Institute of Reproductive and Developmental Biology, Department of Surgery and Cancer, Imperial College London, Hammersmith Hospital, London, United Kingdom
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41
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Caiozzi G, Wong BS, Ricketts ML. Dietary modification of metabolic pathways via nuclear hormone receptors. Cell Biochem Funct 2012; 30:531-51. [PMID: 23027406 DOI: 10.1002/cbf.2842] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Revised: 04/07/2012] [Accepted: 05/09/2012] [Indexed: 12/17/2022]
Abstract
Nuclear hormone receptors (NHRs), as ligand-dependent transcription factors, have emerged as important mediators in the control of whole body metabolism. Because of the promiscuous nature of several members of this superfamily that have been found to bind ligand with lower affinity than the classical steroid NHRs, they consequently display a broader ligand selectivity. This promiscuous nature has facilitated various bioactive dietary components being able to act as agonist ligands for certain members of the NHR superfamily. By binding to these NHRs, bioactive dietary components are able to mediate changes in various metabolic pathways, including, glucose, cholesterol and triglyceride homeostasis among others. This review will provide a general overview of the nuclear hormone receptors that have been shown to be activated by dietary components. The physiological consequences of such receptor activation by these dietary components will then be discussed in more detail.
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Affiliation(s)
- Gianella Caiozzi
- Department of Agriculture, Nutrition and Veterinary Sciences, University of Nevada Reno, Reno, NV 89557, USA
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42
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Hickey TE, Robinson JLL, Carroll JS, Tilley WD. Minireview: The androgen receptor in breast tissues: growth inhibitor, tumor suppressor, oncogene? Mol Endocrinol 2012; 26:1252-67. [PMID: 22745190 DOI: 10.1210/me.2012-1107] [Citation(s) in RCA: 203] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Androgen receptor (AR) signaling exerts an antiestrogenic, growth-inhibitory influence in normal breast tissue, and this role may be sustained in estrogen receptor α (ERα)-positive luminal breast cancers. Conversely, AR signaling may promote growth of a subset of ERα-negative, AR-positive breast cancers with a molecular apocrine phenotype. Understanding the molecular mechanisms whereby androgens can elicit distinct gene expression programs and opposing proliferative responses in these two breast cancer phenotypes is critical to the development of new therapeutic strategies to target the AR in breast cancer.
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Affiliation(s)
- T E Hickey
- Dame Roma Mitchell Cancer Research Laboratory, School of Medicine, Hanson Institute and University of Adelaide, Adelaide SA 5000, Australia
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43
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Epigenetic impact of dietary polyphenols in cancer chemoprevention: Lifelong remodeling of our epigenomes. Pharmacol Res 2012; 65:565-76. [DOI: 10.1016/j.phrs.2012.03.007] [Citation(s) in RCA: 183] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Revised: 03/10/2012] [Accepted: 03/13/2012] [Indexed: 02/07/2023]
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44
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Awasthi S, Simons SS. Separate regions of glucocorticoid receptor, coactivator TIF2, and comodulator STAMP modify different parameters of glucocorticoid-mediated gene induction. Mol Cell Endocrinol 2012; 355:121-34. [PMID: 22342989 PMCID: PMC3312974 DOI: 10.1016/j.mce.2012.02.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Accepted: 02/02/2012] [Indexed: 11/16/2022]
Abstract
Increased specificity in steroid-regulated gene expression is a long-sought goal of endocrinologists. Considerable progress has resulted from the discovery of coactivators, corepressors, and comodulators that adjust the total activity (A(max)) of gene induction. Two less frequently quantitated, but equally potent, means of improving specificity are the concentration of agonist steroid required for half-maximal activity (EC(50)) and the residual or partial agonist activity displayed by most antisteroids (PAA). It is usually assumed that the modulatory activity of transcriptional cofactors coordinately regulates A(max), EC(50), and PAA. Here we examine the hypothesis that these three parameters can be independently modified by separate protein domains. The test system involves three differently sized fragments of each of three factors (glucocorticoid receptor [GR], coactivator TIF2, and comodulator STAMP), which are shown to form a ternary complex and similarly affect the induction properties of transfected and endogenous genes. Twenty-five different fragment combinations of the ternary complex are examined for their ability to modulate the A(max), EC(50), and PAA of a transiently transfected synthetic reporter gene. Different combinations selectively alter one, two, or all three parameters. These results clearly demonstrate that A(max), EC(50), and PAA can be independently regulated under some conditions by different pathways or molecular interactions. This new mechanistic insight suggests that selected activities of individual transcription factors are attractive targets for small molecules, which would have obvious clinical applications for increasing the specificity of steroids during endocrine therapies.
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Affiliation(s)
- Smita Awasthi
- Steroid Hormones Section, NIDDK/LERB, National Institutes of Health, Bethesda, MD, United States
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45
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King HA, Trotter KW, Archer TK. Chromatin remodeling during glucocorticoid receptor regulated transactivation. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2012; 1819:716-26. [PMID: 22425674 DOI: 10.1016/j.bbagrm.2012.02.019] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2012] [Revised: 02/24/2012] [Accepted: 02/28/2012] [Indexed: 12/21/2022]
Abstract
Steroid hormone receptor (SR) signaling leads to widespread changes in gene expression, and aberrant SR signaling can lead to malignancies including breast, prostate, and lung cancers. Chromatin remodeling is an essential component of SR signaling, and defining the process of chromatin and nucleosome remodeling during signaling is critical to the continued development of related therapies. The glucocorticoid receptor (GR) is a key SR that activates numerous promoters including the well defined MMTV promoter. The activation of MMTV by GR provides an excellent model for teasing apart the sequence of events between hormone treatment and changes in gene expression. Comparing hormone-induced transcription from stably integrated promoters with defined nucleosomal structure to that from transiently expressed, unstructured promoters permits key distinctions between interactions that require remodeling and those that do not. The importance of co-activators and histone modifications prior to remodeling and the formation of the preinitiation complex that follows can also be clarified by defining key transition points in the propagation of hormonal signals. Combined with detailed mapping of proteins along the promoter, a temporal and spatial understanding of the signaling and remodeling processes begins to emerge. In this review, we examine SR signaling with a focus on GR activation of the MMTV promoter. We also discuss the ATP-dependent remodeling complex SWI/SNF, which provides the necessary remodeling activity during GR signaling and interacts with several SRs. BRG1, the central ATPase of SWI/SNF, also interacts with a set of BAF proteins that help determine the specialized function and fine-tuned regulation of BRG1 remodeling activity. BRG1 regulation comes from its own subdomains as well as its interactive partners. In particular, the HSA domain region of BRG1 and unique features of its ATPase homology appear to play key roles in regulating remodeling function. Details of the inter-workings of this chromatin remodeling protein continue to be revealed and promise to improve our understanding of the mechanism of chromatin remodeling during steroid hormone signaling. This article is part of a Special Issue entitled: Chromatin in time and space.
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Affiliation(s)
- Heather A King
- Laboratory of Molecular Carcinogenesis, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
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46
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Fang B, Mane-Padros D, Bolotin E, Jiang T, Sladek FM. Identification of a binding motif specific to HNF4 by comparative analysis of multiple nuclear receptors. Nucleic Acids Res 2012; 40:5343-56. [PMID: 22383578 PMCID: PMC3384313 DOI: 10.1093/nar/gks190] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Nuclear receptors (NRs) regulate gene expression by binding specific DNA sequences consisting of AG[G/T]TCA or AGAACA half site motifs in a variety of configurations. However, those motifs/configurations alone do not adequately explain the diversity of NR function in vivo. Here, a systematic examination of DNA binding specificity by protein-binding microarrays (PBMs) of three closely related human NRs—HNF4α, retinoid X receptor alpha (RXRα) and COUPTF2—reveals an HNF4-specific binding motif (H4-SBM), xxxxCAAAGTCCA, as well as a previously unrecognized polarity in the classical DR1 motif (AGGTCAxAGGTCA) for HNF4α, RXRα and COUPTF2 homodimers. ChIP-seq data indicate that the H4-SBM is uniquely bound by HNF4α but not 10 other NRs in vivo, while NRs PXR, FXRα, Rev-Erbα appear to bind adjacent to H4-SBMs. HNF4-specific DNA recognition and transactivation are mediated by residues Asp69 and Arg76 in the DNA-binding domain; this combination of amino acids is unique to HNF4 among all human NRs. Expression profiling and ChIP data predict ∼100 new human HNF4α target genes with an H4-SBM site, including several Co-enzyme A-related genes and genes with links to disease. These results provide important new insights into NR DNA binding.
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Affiliation(s)
- Bin Fang
- Department of Cell Biology and Neuroscience, University of California Riverside, Riverside, CA 92521, USA
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47
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Samarut E, Rochette-Egly C. Nuclear retinoic acid receptors: conductors of the retinoic acid symphony during development. Mol Cell Endocrinol 2012; 348:348-60. [PMID: 21504779 DOI: 10.1016/j.mce.2011.03.025] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2011] [Revised: 03/21/2011] [Accepted: 03/31/2011] [Indexed: 11/18/2022]
Abstract
The vitamin A derivative, retinoic acid (RA), is essential for embryonic development through the activation of cognate nuclear receptors, RARs, which work as ligand dependent regulators of transcription. In vitro studies revealed how RARs control gene expression at the molecular level and now it appears that it is fine-tuned by a phosphorylation code. In addition, several genetic approaches provided valuable insights on the functions of RARs during development and on the influence of other actors such as the enzymes involved in RA synthesis and degradation and other signaling pathways. It appears that RARs are the conductors of the RA signaling symphony through controlling the dynamics and the coordination of the different players and development steps.
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Affiliation(s)
- Eric Samarut
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, INSERM, U596; CNRS, UMR7104; Université de Strasbourg, 1 rue Laurent Fries, BP 10142, 67404 Illkirch Cedex, France.
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48
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Clark AR, Belvisi MG. Maps and legends: the quest for dissociated ligands of the glucocorticoid receptor. Pharmacol Ther 2011; 134:54-67. [PMID: 22212616 DOI: 10.1016/j.pharmthera.2011.12.004] [Citation(s) in RCA: 171] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2011] [Accepted: 12/07/2011] [Indexed: 01/19/2023]
Abstract
Glucocorticoids are steroid hormones that have pleiotropic effects on development, metabolism, cognitive function and other aspects of physiology. Since the demonstration more than sixty years ago of their capacity to suppress inflammation, synthetic glucocorticoids have been extremely widely used in the treatment of inflammatory diseases. However, their clinical use is limited by numerous, unpredictable and potentially serious side effects. Glucocorticoids regulate gene expression both positively and negatively. Both of these effects are mediated by the glucocorticoid receptor, a ligand-dependent transcription factor. It has become widely accepted that anti-inflammatory effects of glucocorticoids are mostly due to inhibition of transcription, whereas the activation of transcription by the glucocorticoid receptor accounts for the majority of side effects. This dogma (which we refer to as the "transrepression hypothesis") predicts the possibility of uncoupling therapeutic, anti-inflammatory effects from side effects by identifying novel, selective ligands of the glucocorticoid receptor, which preferentially mediate inhibition rather than activation of transcription. It is argued that such "dissociated" glucocorticoid receptor ligands should retain anti-inflammatory potency but cause fewer side effects. Here we critically re-examine the history and foundations of the transrepression hypothesis. We argue that it is incompatible with the complexity of gene regulation by glucocorticoids and poorly supported by experimental evidence; that it no longer aids clear thinking about the actions of the glucocorticoid receptor; and that it will not prove a fruitful basis for continued refinement and improvement of anti-inflammatory drugs that target the glucocorticoid receptor.
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Affiliation(s)
- Andrew R Clark
- Kennedy Institute of Rheumatology, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, 65 Aspenlea Road, Hammersmith, London W6 8LH, United Kingdom.
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49
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Datson NA, Polman JAE, de Jonge RT, van Boheemen PTM, van Maanen EMT, Welten J, McEwen BS, Meiland HC, Meijer OC. Specific regulatory motifs predict glucocorticoid responsiveness of hippocampal gene expression. Endocrinology 2011; 152:3749-57. [PMID: 21846803 DOI: 10.1210/en.2011-0287] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The glucocorticoid receptor (GR) is an ubiquitously expressed ligand-activated transcription factor that mediates effects of cortisol in relation to adaptation to stress. In the brain, GR affects the hippocampus to modulate memory processes through direct binding to glucocorticoid response elements (GREs) in the DNA. However, its effects are to a high degree cell specific, and its target genes in different cell types as well as the mechanisms conferring this specificity are largely unknown. To gain insight in hippocampal GR signaling, we characterized to which GRE GR binds in the rat hippocampus. Using a position-specific scoring matrix, we identified evolutionary-conserved putative GREs from a microarray based set of hippocampal target genes. Using chromatin immunoprecipitation, we were able to confirm GR binding to 15 out of a selection of 32 predicted sites (47%). The majority of these 15 GREs are previously undescribed and thus represent novel GREs that bind GR and therefore may be functional in the rat hippocampus. GRE nucleotide composition was not predictive for binding of GR to a GRE. A search for conserved flanking sequences that may predict GR-GRE interaction resulted in the identification of GC-box associated motifs, such as Myc-associated zinc finger protein 1, within 2 kb of GREs with GR binding in the hippocampus. This enrichment was not present around nonbinding GRE sequences nor around proven GR-binding sites from a mesenchymal stem-like cell dataset that we analyzed. GC-binding transcription factors therefore may be unique partners for DNA-bound GR and may in part explain cell-specific transcriptional regulation by glucocorticoids in the context of the hippocampus.
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Affiliation(s)
- N A Datson
- Division of Medical Pharmacology, Leiden/Amsterdam Center for Drug Research, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands.
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50
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Buchanan G, Need EF, Barrett JM, Bianco-Miotto T, Thompson VC, Butler LM, Marshall VR, Tilley WD, Coetzee GA. Corepressor effect on androgen receptor activity varies with the length of the CAG encoded polyglutamine repeat and is dependent on receptor/corepressor ratio in prostate cancer cells. Mol Cell Endocrinol 2011; 342:20-31. [PMID: 21664238 PMCID: PMC3314496 DOI: 10.1016/j.mce.2011.05.023] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Revised: 04/12/2011] [Accepted: 05/09/2011] [Indexed: 01/01/2023]
Abstract
The response of prostate cells to androgens reflects a combination of androgen receptor (AR) transactivation and transrepression, but how these two processes differ mechanistically and influence prostate cancer risk and disease outcome remain elusive. Given recent interest in targeting AR transrepressive processes, a better understanding of AR/corepressor interaction and responses is warranted. Here, we used transactivation and interaction assays with wild-type and mutant ARs, and deletion AR fragments, to dissect the relationship between AR and the corepressor, silencing mediator for retinoic acid and thyroid hormone receptors (SMRT). We additionally tested how these processes are influenced by AR agonist and antagonist ligands, as well as by variation in the polyglutamine tract in the AR amino terminal domain (NTD), which is encoded by a polymorphic CAG repeat in the gene. SMRT was recruited to the AR ligand binding domain by agonist ligand, and as determined by the effect of strategic mutations in activation function 2 (AF-2), requires a precise conformation of that domain. A distinct region of SMRT also mediated interaction with the AR-NTD via the transactivation unit 5 (TAU5; residues 315-538) region. The degree to which SMRT was able to repress AR increased from 17% to 56% as the AR polyglutamine repeat length was increased from 9 to 42 residues, but critically this effect could be abolished by increasing the SMRT:AR molar ratio. These data suggest that the extent to which the CAG encoded polyglutamine repeat influences AR activity represents a balance between corepressor and coactivator occupancy of the same ligand-dependent and independent AR interaction surfaces. Changes in the homeostatic relationship of AR to these molecules, including SMRT, may explain the variable penetrance of the CAG repeat and the loss of AR signaling flexibility in prostate cancer progression.
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Affiliation(s)
- Grant Buchanan
- Department of Preventive Medicine, Norris Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, USA.
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