1
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Tkach JM, Philip R, Sharma A, Strecker J, Durocher D, Pelletier L. Global cellular response to chemical perturbation of PLK4 activity and abnormal centrosome number. eLife 2022; 11:73944. [PMID: 35758262 PMCID: PMC9236612 DOI: 10.7554/elife.73944] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Accepted: 06/04/2022] [Indexed: 11/13/2022] Open
Abstract
Centrosomes act as the main microtubule organizing center (MTOC) in metazoans. Centrosome number is tightly regulated by limiting centriole duplication to a single round per cell cycle. This control is achieved by multiple mechanisms, including the regulation of the protein kinase PLK4, the most upstream facilitator of centriole duplication. Altered centrosome numbers in mouse and human cells cause p53-dependent growth arrest through poorly defined mechanisms. Recent work has shown that the E3 ligase TRIM37 is required for cell cycle arrest in acentrosomal cells. To gain additional insights into this process, we undertook a series of genome-wide CRISPR/Cas9 screens to identify factors important for growth arrest triggered by treatment with centrinone B, a selective PLK4 inhibitor. We found that TRIM37 is a key mediator of growth arrest after partial or full PLK4 inhibition. Interestingly, PLK4 cellular mobility decreased in a dose-dependent manner after centrinone B treatment. In contrast to recent work, we found that growth arrest after PLK4 inhibition correlated better with PLK4 activity than with mitotic length or centrosome number. These data provide insights into the global response to changes in centrosome number and PLK4 activity and extend the role for TRIM37 in regulating the abundance, localization, and function of centrosome proteins.
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Affiliation(s)
- Johnny M Tkach
- Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, Canada
| | - Reuben Philip
- Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, Canada
| | - Amit Sharma
- Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, Canada
| | - Jonathan Strecker
- Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, Canada
| | - Daniel Durocher
- Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, Canada
| | - Laurence Pelletier
- Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, Canada
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2
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Hsu HL, Chen HK, Tsai CH, Liao PL, Chan YJ, Lee YC, Lee CC, Li CH. Aryl Hydrocarbon Receptor Defect Attenuates Mitogen-Activated Signaling through Leucine-Rich Repeats and Immunoglobulin-like Domains 1 (LRIG1)-Dependent EGFR Degradation. Int J Mol Sci 2021; 22:9988. [PMID: 34576152 PMCID: PMC8464816 DOI: 10.3390/ijms22189988] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 09/05/2021] [Accepted: 09/11/2021] [Indexed: 11/17/2022] Open
Abstract
Aryl hydrocarbon receptor (AHR) genomic pathway has been well-characterized in a number of respiratory diseases. In addition, the cytoplasmic AHR protein may act as an adaptor of E3 ubiquitin ligase. In this study, the physiological functions of AHR that regulate cell proliferation were explored using the CRISPR/Cas9 system. The doubling-time of the AHR-KO clones of A549 and BEAS-2B was observed to be prolonged. The attenuation of proliferation potential was strongly associated with either the induction of p27Kip1 or the impairment in mitogenic signal transduction driven by the epidermal growth factor (EGF) and EGF receptor (EGFR). We found that the leucine-rich repeats and immunoglobulin-like domains 1 (LRIG1), a repressor of EGFR, was induced in the absence of AHR in vitro and in vivo. The LRIG1 tends to degrade via a proteasome dependent manner by interacting with AHR in wild-type cells. Either LRIG1 or a disintegrin and metalloprotease 17 (ADAM17) were accumulated in AHR-defective cells, consequently accelerating the degradation of EGFR, and attenuating the response to mitogenic stimulation. We also affirmed low AHR but high LRIG1 levels in lung tissues of chronic obstructive pulmonary disease (COPD) patients. This might partially elucidate the sluggish tissue repairment and developing inflammation in COPD patients.
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Affiliation(s)
- Han-Lin Hsu
- Division of Pulmonary Medicine, Department of Internal Medicine, Wan Fang Hospital, Taipei Medical University, Taipei 116, Taiwan;
- Pulmonary Research Center, Wan Fang Hospital, Taipei Medical University, Taipei 116, Taiwan
- School of Respiratory Therapy, College of Medicine, Taipei Medical University, Taipei 110, Taiwan;
| | - Hong-Kai Chen
- School of Respiratory Therapy, College of Medicine, Taipei Medical University, Taipei 110, Taiwan;
- Department of Physiology, School of Medicine, College of Medicine, Taipei Medical University, Taipei 110, Taiwan;
- Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei 110, Taiwan;
| | - Chi-Hao Tsai
- Department of Ophthalmology, University of North Carolina School of Medicine, Chapel Hill, NC 27517, USA;
| | - Po-Lin Liao
- Institute of Food Safety and Health Risk Assessment, School of Pharmaceutical Sciences, National Yang-Ming University, Taipei 112, Taiwan;
| | - Yen-Ju Chan
- Department of Physiology, School of Medicine, College of Medicine, Taipei Medical University, Taipei 110, Taiwan;
- Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei 110, Taiwan;
| | - Yu-Cheng Lee
- Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei 110, Taiwan;
| | - Chen-Chen Lee
- Department of Microbiology and Immunology, School of Medicine, China Medicine University, Taichung 404, Taiwan;
| | - Ching-Hao Li
- Department of Physiology, School of Medicine, College of Medicine, Taipei Medical University, Taipei 110, Taiwan;
- Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei 110, Taiwan;
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3
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Avilla MN, Malecki KMC, Hahn ME, Wilson RH, Bradfield CA. The Ah Receptor: Adaptive Metabolism, Ligand Diversity, and the Xenokine Model. Chem Res Toxicol 2020; 33:860-879. [PMID: 32259433 PMCID: PMC7175458 DOI: 10.1021/acs.chemrestox.9b00476] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Indexed: 12/12/2022]
Abstract
The Ah receptor (AHR) has been studied for almost five decades. Yet, we still have many important questions about its role in normal physiology and development. Moreover, we still do not fully understand how this protein mediates the adverse effects of a variety of environmental pollutants, such as the polycyclic aromatic hydrocarbons (PAHs), the chlorinated dibenzo-p-dioxins ("dioxins"), and many polyhalogenated biphenyls. To provide a platform for future research, we provide the historical underpinnings of our current state of knowledge about AHR signal transduction, identify a few areas of needed research, and then develop concepts such as adaptive metabolism, ligand structural diversity, and the importance of proligands in receptor activation. We finish with a discussion of the cognate physiological role of the AHR, our perspective on why this receptor is so highly conserved, and how we might think about its cognate ligands in the future.
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Affiliation(s)
- Mele N. Avilla
- Molecular and Environmental Toxicology
Center, Department of Population Health
Sciences, University of Wisconsin School
of Medicine and Public Health, Madison, Wisconsin 53726-2379, United States
| | - Kristen M. C. Malecki
- Molecular and Environmental Toxicology
Center, Department of Population Health
Sciences, University of Wisconsin School
of Medicine and Public Health, Madison, Wisconsin 53726-2379, United States
| | - Mark E. Hahn
- Biology
Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543-1050, United States
| | - Rachel H. Wilson
- Molecular and Environmental Toxicology
Center, Department of Population Health
Sciences, University of Wisconsin School
of Medicine and Public Health, Madison, Wisconsin 53726-2379, United States
| | - Christopher A. Bradfield
- Molecular and Environmental Toxicology
Center, Department of Population Health
Sciences, University of Wisconsin School
of Medicine and Public Health, Madison, Wisconsin 53726-2379, United States
- McArdle
Laboratory for Cancer Research, University of Wisconsin School of Medicine
and Public Health, Madison, Wisconsin 53705-227, United States
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4
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Flores-Pérez A, Elizondo G. Apoptosis induction and inhibition of HeLa cell proliferation by alpha-naphthoflavone and resveratrol are aryl hydrocarbon receptor-independent. Chem Biol Interact 2018; 281:98-105. [DOI: 10.1016/j.cbi.2017.12.029] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Revised: 11/30/2017] [Accepted: 12/18/2017] [Indexed: 12/20/2022]
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5
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Yao X, Tan J, Lim KJ, Koh J, Ooi WF, Li Z, Huang D, Xing M, Chan YS, Qu JZ, Tay ST, Wijaya G, Lam YN, Hong JH, Lee-Lim AP, Guan P, Ng MSW, He CZ, Lin JS, Nandi T, Qamra A, Xu C, Myint SS, Davies JOJ, Goh JY, Loh G, Tan BC, Rozen SG, Yu Q, Tan IBH, Cheng CWS, Li S, Chang KTE, Tan PH, Silver DL, Lezhava A, Steger G, Hughes JR, Teh BT, Tan P. VHL Deficiency Drives Enhancer Activation of Oncogenes in Clear Cell Renal Cell Carcinoma. Cancer Discov 2017; 7:1284-1305. [DOI: 10.1158/2159-8290.cd-17-0375] [Citation(s) in RCA: 83] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2017] [Revised: 07/19/2017] [Accepted: 08/25/2017] [Indexed: 11/16/2022]
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6
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Wright EJ, De Castro KP, Joshi AD, Elferink CJ. Canonical and non-canonical aryl hydrocarbon receptor signaling pathways. CURRENT OPINION IN TOXICOLOGY 2017; 2:87-92. [PMID: 32296737 DOI: 10.1016/j.cotox.2017.01.001] [Citation(s) in RCA: 78] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Decades of research on the Aryl hydrocarbon Receptor (AhR) has unveiled its involvement in the toxicity of halogenated and polycyclic aromatic hydrocarbons, and a myriad of normal physiological processes. The molecular dissection of AhR biology has centered on a canonical signaling pathway in an effort to mechanistically reconcile the diverse pathophysiological effects of exposure to environmental pollutants. As a consequence, we now know that canonical signaling can explain many but not all of the AhR-mediated effects. Here we describe recent findings that point to non-canonical signaling pathways, and focus on a novel AhR interaction with the Krüppel-like Factor 6 protein responsible for previously un-recognized epigenetic changes in the chromatin affecting gene expression.
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Affiliation(s)
- Eric J Wright
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, 301 University Blvd., Galveston, TX 77555-0654, USA
| | - Karen Pereira De Castro
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, 301 University Blvd., Galveston, TX 77555-0654, USA
| | - Aditya D Joshi
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, 301 University Blvd., Galveston, TX 77555-0654, USA
| | - Cornelis J Elferink
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, 301 University Blvd., Galveston, TX 77555-0654, USA
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7
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Villa M, Gialitakis M, Tolaini M, Ahlfors H, Henderson CJ, Wolf CR, Brink R, Stockinger B. Aryl hydrocarbon receptor is required for optimal B-cell proliferation. EMBO J 2017; 36:116-128. [PMID: 27875245 PMCID: PMC5210087 DOI: 10.15252/embj.201695027] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Revised: 10/05/2016] [Accepted: 10/11/2016] [Indexed: 12/18/2022] Open
Abstract
The aryl hydrocarbon receptor (AhR), a transcription factor known for mediating xenobiotic toxicity, is expressed in B cells, which are known targets for environmental pollutants. However, it is unclear what the physiological functions of AhR in B cells are. We show here that expression of Ahr in B cells is up-regulated upon B-cell receptor (BCR) engagement and IL-4 treatment. Addition of a natural ligand of AhR, FICZ, induces AhR translocation to the nucleus and transcription of the AhR target gene Cyp1a1, showing that the AhR pathway is functional in B cells. AhR-deficient (Ahr-/-) B cells proliferate less than AhR-sufficient (Ahr+/+) cells following in vitro BCR stimulation and in vivo adoptive transfer models confirmed that Ahr-/- B cells are outcompeted by Ahr+/+ cells. Transcriptome comparison of AhR-deficient and AhR-sufficient B cells identified cyclin O (Ccno), a direct target of AhR, as a top candidate affected by AhR deficiency.
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Affiliation(s)
- Matteo Villa
- The Francis Crick Institute, Mill Hill Laboratory, London, UK
| | | | - Mauro Tolaini
- The Francis Crick Institute, Mill Hill Laboratory, London, UK
| | - Helena Ahlfors
- The Francis Crick Institute, Mill Hill Laboratory, London, UK
| | - Colin J Henderson
- Division of Cancer Research, University of Dundee Ninewells Hospital and Medical School, Dundee, UK
| | - C Roland Wolf
- Division of Cancer Research, University of Dundee Ninewells Hospital and Medical School, Dundee, UK
| | - Robert Brink
- Garvan Institute of Medical Research, Sydney, NSW, Australia
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8
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Esakky P, Moley KH. Paternal smoking and germ cell death: A mechanistic link to the effects of cigarette smoke on spermatogenesis and possible long-term sequelae in offspring. Mol Cell Endocrinol 2016; 435:85-93. [PMID: 27424142 PMCID: PMC5014701 DOI: 10.1016/j.mce.2016.07.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Revised: 07/10/2016] [Accepted: 07/11/2016] [Indexed: 12/12/2022]
Abstract
Paternal exposure to constituents of cigarette smoke (CS) is reportedly associated with infertility, birth defects and childhood cancers even though the mechanism behind this relationship is still unclear. Chronic cigarette smoking by men leads to poor sperm quality and quantity mainly through oxidative stress and also direct assault by CS metabolites. Among several carcinogenic and teratogenic components of cigarette smoke condensate (CSC), polycyclic aromatic hydrocarbons (PAHs) display a preeminent role in accelerating germ cell death via the cytoplasmic transcription factor, aryl hydrocarbon receptor (AHR) that is present across all stages of spermatogenesis. Activation of AHR by growth factors though benefits normal cellular functions, its mediation by CSC in a spermatocyte cell line [Gc2(spd)ts] adversely affects the expression of a battery of genes associated with antioxidant mechanisms, cell proliferation and apoptosis, and cell cycle progress. Besides, the CSC-mediated cross talk either between AHR and NRF2 or AHR-NRF2 and MAPKs pathways inhibits normal proliferation of the spermatogenic GC-2spd(ts) cells in vitro and cell death of spermatocytes in vivo. Pharmacological inactivation of CSC-induced AHR but not its genetic manipulation seems preventing DNA and cell membrane damage in Gc2(spd)ts. Data from recent reports suggest that the cigarette smoke affects both the genomic and epigenomic components of the sperm and attributes any associated changes to developmental defects in the offspring. Thus, the studies discussed here in this review shed light on possible mechanistic factors that could probably be responsible for the paternally mediated birth defects in the offspring following exposure to the toxic constituents of cigarette smoke.
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Affiliation(s)
- Prabagaran Esakky
- Research, Department of Veterans Affairs Medical Center, St. Louis, MO, USA; Department of Obstetrics and Gynecology, Washington University School of Medicine in St. Louis, MO 63110, USA.
| | - Kelle H Moley
- Research, Department of Veterans Affairs Medical Center, St. Louis, MO, USA; Department of Obstetrics and Gynecology, Washington University School of Medicine in St. Louis, MO 63110, USA.
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9
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Manzetti S, Andersen O. Biochemical and physiological effects from exhaust emissions. A review of the relevant literature. ACTA ACUST UNITED AC 2016; 23:285-293. [PMID: 27793419 DOI: 10.1016/j.pathophys.2016.10.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Accepted: 10/20/2016] [Indexed: 01/05/2023]
Abstract
Exhaust emissions are to date ranked among the most frequent causes of premature deaths worldwide. The combustion of fuels such as diesel, gasoline, and bio-blends provokes a series of pathophysiological responses in exposed subjects, which are associated with biochemical and immunological triggering. It is critical to understand these mechanisms, which are directly related to the levels of aerosol, liquid and gaseous components in fuel exhaust (e.g. nanoparticles, particulate matter, volatile compounds), so to cast attention on their toxicity and gradually minimize their use. This review reports findings in the recent literature concerning the biochemical and cellular pathways triggered during intoxication by exhaust emissions, and links these findings to pathophysiological responses such as inflammation and vasoconstriction. This study provides critical in vitro and in vivo data for the reduction of emissions in urban centers, with an emphasis on the prevention of exposure of groups such as children, the elderly, and other affected groups, and shows how the exposure to exhaust emissions induces mechanisms of pathogenesis related to cardiopulmonary pathologies and long-term diseases such as asthma, allergies, and cancer. This review summarizes the cellular and physiological responses of humans to exhaust emissions in a comprehensive fashion, and is important for legislative developments in fuel politics.
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Affiliation(s)
| | - Otto Andersen
- Vestlandsforskning, Fosshaugane Campus, 6851 Sogndal, Norway.
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10
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Kumar S, Wang J, Thomson AW, Gandhi CR. Hepatic stellate cells increase the immunosuppressive function of natural Foxp3+ regulatory T cells via IDO-induced AhR activation. J Leukoc Biol 2016; 101:429-438. [PMID: 27581538 DOI: 10.1189/jlb.2a0516-239r] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2016] [Revised: 07/20/2016] [Accepted: 08/04/2016] [Indexed: 12/14/2022] Open
Abstract
Immunosuppressive, naturally occurring CD4+CD25+forkhead box p3+ (Foxp3+) regulatory T cells (nTregs) offer potential for the treatment of immune-mediated inflammatory disorders. However, potential instability of ex vivo-expanded nTregs following their adoptive transfer may be a significant limitation. LPS-stimulated hepatic stellate cells (HSCs) induce expansion and enhance the suppressive function and stability of allogeneic nTregs We aimed to delineate mechanisms underlying HSC-induced expansion and increased potency of nTregs HSCs and nTregs were isolated from mouse livers and spleens, respectively. Following coculture with LPS-pretreated allogeneic HSCs (LPS/HSCs), proliferation of nTregs was measured by CFSE dilution, and Foxp3 expression and acetylation were determined by immunoprecipitation (IP) and Western blotting analysis. Expression of various genes associated with immunologic tolerance was determined by quantitative RT-PCR (qRT-PCR). LPS stimulation increased the expression and activity of the immunoregulatory enzyme IDO1 in HSCs, and LPS/HSCs stimulated aryl hydrocarbon receptor (AhR) signaling in cocultured nTregs Reciprocally, Tregs increased IDO1 expression in HSCs. IDO1-/- LPS/HSCs were inferior to WT LPS/HSCs in stimulating nTreg expansion. Pharmacologic inhibition of IDO1 in HSCs by 1-methyltryptophan (1MT) inhibited LPS/HSC-induced AhR signaling in nTregs, which was responsible for their expansion, Foxp3 expression, and stabilization of Foxp3 by increasing acetylation of lysine residues. Finally, HSCs cryopreserved, following 2-3 passages, were as potent as primary-cultured HSCs in expanding nTregs In conclusion, LPS/HSCs expand allogeneic nTregs through an IDO-dependent, AhR-mediated mechanism and increase their stability through lysine-acetylation of Foxp3. nTregs expanded by cryopreserved HSCs may have potential for clinical use.
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Affiliation(s)
- Sudhir Kumar
- Department of Surgery, University of Cincinnati, Cincinnati, Ohio, USA.,Cincinnati VA Medical Center, Cincinnati, Ohio, USA
| | - Jiang Wang
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, Ohio, USA
| | - Angus W Thomson
- Thomas E. Starzl Transplantation Institute, Departments of Surgery and Immunology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA; and
| | - Chandrashekhar R Gandhi
- Department of Surgery, University of Cincinnati, Cincinnati, Ohio, USA; .,Cincinnati VA Medical Center, Cincinnati, Ohio, USA.,Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
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11
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Aftabi Y, Colagar AH, Mehrnejad F. An in silico approach to investigate the source of the controversial interpretations about the phenotypic results of the human AhR-gene G1661A polymorphism. J Theor Biol 2016; 393:1-15. [PMID: 26776670 DOI: 10.1016/j.jtbi.2016.01.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2015] [Revised: 12/11/2015] [Accepted: 01/01/2016] [Indexed: 12/21/2022]
Abstract
Aryl hydrocarbon receptor (AhR) acts as an enhancer binding ligand-activated intracellular receptor. Chromatin remodeling components and general transcription factors such as TATA-binding protein (TBP) are evoked on AhR-target genes by interaction with its flexible transactivation domain (TAD). AhR-G1661A single nucleotide polymorphism (SNP: rs2066853) causes an arginine to lysine substitution in the acidic sub-domain of TAD at position 554 (R554K). Although, numerous studies associate the SNP with some abnormalities such as cancer, other reliable investigations refuse the associations. Consequently, the interpretation of the phenotypic results of G1661A-transition has been controversial. In this study, an in silico analysis were performed to investigate the possible effects of the transition on AhR-mRNA, protein structure, interaction properties and modifications. The analysis revealed that the R554K substitution affects secondary structure and solvent accessibility of adjacent residues. Also, it causes to decreasing of the AhR stability; altering the hydropathy features of the local sequence and changing the pattern of the residues at the binding site of the TAD-acidic sub-domain. Generating of new sites for ubiquitination and acetylation for AhR-K554 variant respectively at positions 544 and 560 was predicted. Our findings intensify the idea that the AhR-G1661A transition may affects AhR-TAD interactions, especially with the TBP, which influence AhR-target genes expression. However, the previously reported flexibility of the modular TAD could act as an intervening factor, moderate the SNP effects and causes distinct outcomes in different individuals and tissues.
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Affiliation(s)
- Younes Aftabi
- Department of Molecular and Cell Biology, Faculty of Basic Sciences, University of Mazandaran, Babolsar, Post Code: 47416-95447, Mazandaran, Iran
| | - Abasalt Hosseinzadeh Colagar
- Department of Molecular and Cell Biology, Faculty of Basic Sciences, University of Mazandaran, Babolsar, Post Code: 47416-95447, Mazandaran, Iran.
| | - Faramarz Mehrnejad
- Department of Life Science Engineering, Faculty of New Sciences & Technologies, University of Tehran, P.O. Box: 14395-1561, Tehran, Iran
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12
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Jackson DP, Joshi AD, Elferink CJ. Ah Receptor Pathway Intricacies; Signaling Through Diverse Protein Partners and DNA-Motifs. Toxicol Res (Camb) 2015; 4:1143-1158. [PMID: 26783425 PMCID: PMC4714567 DOI: 10.1039/c4tx00236a] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The Ah receptor is a transcription factor that modulates gene expression via interactions with multiple protein partners; these are reviewed, including the novel NC-XRE pathway involving KLF6.
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13
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Dever DP, Adham ZO, Thompson B, Genestine M, Cherry J, Olschowka JA, DiCicco-Bloom E, Opanashuk LA. Aryl hydrocarbon receptor deletion in cerebellar granule neuron precursors impairs neurogenesis. Dev Neurobiol 2015; 76:533-50. [PMID: 26243376 DOI: 10.1002/dneu.22330] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Accepted: 07/28/2015] [Indexed: 11/12/2022]
Abstract
The aryl hydrocarbon receptor (AhR) is a ligand-activated member of the basic-helix-loop-helix/PER-ARNT-SIM(PAS) transcription factor superfamily that also mediates the toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Increasing evidence suggests that AhR influences the development of many tissues, including the central nervous system. Our previous studies suggest that sustained AhR activation by TCDD and/or AhR deletion disrupts cerebellar granule neuron precursor (GNP) development. In the current study, to determine whether endogenous AhR controls GNP development in a cell-autonomous manner, we created a GNP-specific AhR deletion mouse, AhR(fx/fx) /Math1(CRE/+) (AhR CKO). Selective AhR deletion in GNPs produced abnormalities in proliferation and differentiation. Specifically, fewer GNPs were engaged in S-phase, as demonstrated by ∼25% reductions in thymidine (in vitro) and Bromodeoxyuridine (in vivo) incorporation. Furthermore, total granule neuron numbers in the internal granule layer at PND21 and PND60 were diminished in AhR conditional knockout (CKO) mice compared with controls. Conversely, differentiation was enhanced, including ∼40% increase in neurite outgrowth and 50% increase in GABARα6 receptor expression in deletion mutants. Our results suggest that AhR activity plays a role in regulating granule neuron number and differentiation, possibly by coordinating this GNP developmental transition. These studies provide novel insights for understanding the normal roles of AhR signaling during cerebellar granule cell neurogenesis and may have important implications for the effects of environmental factors in cerebellar dysgenesis.
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Affiliation(s)
- Daniel P Dever
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York, 14642
| | - Zachariah O Adham
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York, 14642
| | - Bryan Thompson
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York, 14642
| | - Matthieu Genestine
- Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, Rutgers, the State University of New Jersey, Piscataway, New Jersey, 08854
| | - Jonathan Cherry
- Department of Pathology and Laboratory Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York, 14642
| | - John A Olschowka
- Department of Neurobiology and Anatomy, University of Rochester School of Medicine and Dentistry, Rochester, New York, 14642
| | - Emanuel DiCicco-Bloom
- Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, Rutgers, the State University of New Jersey, Piscataway, New Jersey, 08854
| | - Lisa A Opanashuk
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York, 14642
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14
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Esakky P, Hansen DA, Drury AM, Moley KH. Modulation of cell cycle progression in the spermatocyte cell line [GC-2spd(ts) Cell-Line] by cigarette smoke condensate (CSC) via arylhydrocarbon receptor-nuclear factor erythroid 2-related factor 2 (Ahr-Nrf2) pathway. Biol Reprod 2014; 90:9. [PMID: 24258214 DOI: 10.1095/biolreprod.113.113225] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2023] Open
Abstract
Prior studies in our laboratory have demonstrated that cigarette smoke condensate (CSC) activates arylhydrocarbon receptor (Ahr) leading to upregulation of several antioxidant enzymes in murine spermatocytes. In this study, we show that exposure of the spermatocyte cell line GC-2spd(ts) to CSC induces an increase in Cyp1a1, demonstrating AHR activation, and simultaneous expression and nuclear translocation of nuclear factor erythroid 2-related factor 2 (NRF2), where it is believed to modulate Ahr expression by a feedback mechanism. Pharmacological inhibition by the AHR-antagonist CH223191 and interference by Ahr- and Nrf2-small interfering RNA followed by quantitative real-time PCR implicate the Ahr-Nrf2 pathway in the modulation of DNA damage and growth suppression genes such as Gadd45a and P21 and oxidative stress-related genes Cyp1a1, Nrf2, and Ahrr. Flow cytometry accompanied with cell proliferation assay indicate the CSC induces accumulation of spermatocytes at the S-G2/M phase of the cell cycle. Thus, the data obtained suggest that CSC contains several AHR-agonists that are capable of altering the growth pattern of spermatocytes in vitro through the Ahr-Nrf2 signaling mechanism.
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Affiliation(s)
- Prabagaran Esakky
- Research, Department of Veterans Affairs Medical Center, St. Louis, Missouri
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15
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Dioxins, the aryl hydrocarbon receptor and the central regulation of energy balance. Front Neuroendocrinol 2010; 31:452-78. [PMID: 20624415 DOI: 10.1016/j.yfrne.2010.07.002] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2010] [Revised: 06/15/2010] [Accepted: 07/05/2010] [Indexed: 01/03/2023]
Abstract
Dioxins are ubiquitous environmental contaminants that have attracted toxicological interest not only for the potential risk they pose to human health but also because of their unique mechanism of action. This mechanism involves a specific, phylogenetically old intracellular receptor (the aryl hydrocarbon receptor, AHR) which has recently proven to have an integral regulatory role in a number of physiological processes, but whose endogenous ligand is still elusive. A major acute impact of dioxins in laboratory animals is the wasting syndrome, which represents a puzzling and dramatic perturbation of the regulatory systems for energy balance. A single dose of the most potent dioxin, TCDD, can permanently readjust the defended body weight set-point level thus providing a potentially useful tool and model for physiological research. Recent evidence of response-selective modulation of AHR action by alternative ligands suggests further that even therapeutic implications might be possible in the future.
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16
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Watabe Y, Nazuka N, Tezuka M, Shimba S. Aryl hydrocarbon receptor functions as a potent coactivator of E2F1-dependent trascription activity. Biol Pharm Bull 2010; 33:389-97. [PMID: 20190398 DOI: 10.1248/bpb.33.389] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that mediates a spectrum of toxic and biological effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin and related compounds. Several reports have shown that the AhR plays an important role in the control of cell-cycle progression, and this function is thought to be partly associated with the tumor promotion activity of dioxin. However, the underling mechanisms are not fully understood. We have previously shown that overexpression of AhR, as well as AhR ligand treatment, stimulates cell proliferation of human lung cancer A549 cells. In AhR-activated cells, the expression levels of DNA synthesis-related genes such as proliferating cell nuclear antigen (PCNA) and RFC38 are notably increased. Expression of these genes is mainly regulated by E2F1, a transcription factor that is crucial for transition of the cell cycle from G1 to S phase. We show here that the transcriptional activity of E2F1 is increased by the AhR agonist treatment and that this effect depends on the presence of AhR. Functional mapping of AhR showed that the Per-Arnt-Sim (PAS) B domain is required for promotion of E2F1 activity. The mechanism involves formation of a complex of AhR and E2F1 on the regulatory region in the E2F1 target gene, followed by recruitment of coactivator activator for thyroid hormone and retinoid receptors (ACTR). Consequently, the results in this study indicate the physiological function of AhR as a potent transcriptional coactivator of E2F1-dependent transcription and implicate the AhR-E2F1 interaction as a part of the mechanism by which AhR/Arnt promotes cell proliferation.
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Affiliation(s)
- Yuichi Watabe
- Department of Health Science, College of Pharmacy, Nihon University, Funabashi, Chiba 274-8555,Japan
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17
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Ma C, Marlowe JL, Puga A. The aryl hydrocarbon receptor at the crossroads of multiple signaling pathways. EXS 2009; 99:231-57. [PMID: 19157064 DOI: 10.1007/978-3-7643-8336-7_9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The aryl hydrocarbon receptor (AHR) has long been recognized as a ligand-activated transcription factor responsible for the induction of drug-metabolizing enzymes. Its role in the combinatorial matrix of cell functions was established long before the first report of an AHR cDNA sequence was published. It is only recently that other functions of this protein have begun to be recognized, and it is now clear that the AHR also functions in pathways outside of its well-characterized role in xenobiotic enzyme induction. Perturbation of these pathways by xenobiotic ligands may ultimately explain much of the toxicity of these compounds. This chapter focuses on the interactions of the AHR in pathways critical to cell cycle regulation, mitogen-activated protein kinase cascades, differentiation and apoptosis. Ultimately, the effect of a particular AHR ligand on the biology of the organism will depend on the milieu of critical pathways and proteins expressed in specific cells and tissues with which the AHR itself interacts.
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Affiliation(s)
- Ci Ma
- Department of Environmental Health and Center for Environmental Genetics, University of Cincinnati College of Medicine, Cincinnati, OH 45220, USA.
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18
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Min C, Eddy SF, Sherr DH, Sonenshein GE. NF-kappaB and epithelial to mesenchymal transition of cancer. J Cell Biochem 2008; 104:733-44. [PMID: 18253935 DOI: 10.1002/jcb.21695] [Citation(s) in RCA: 315] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
During progression of an in situ to an invasive cancer, epithelial cells lose expression of proteins that promote cell-cell contact, and acquire mesenchymal markers, which promote cell migration and invasion. These events bear extensive similarities to the process of epithelial to mesenchymal transition (EMT), which has been recognized for several decades as critical feature of embryogenesis. The NF-kappaB family of transcription factors plays pivotal roles in both promoting and maintaining an invasive phenotype. After briefly describing the NF-kappaB family and its role in cancer, in this review we will first describe studies elucidating the functions of NF-kappaB in transcription of master regulator genes that repress an epithelial phenotype. In the second half, we discuss the roles of NF-kappaB in control of mesenchymal genes critical for promoting and maintaining an invasive phenotype. Overall, NF-kappaB is identified as a key target in prevention and in the treatment of invasive carcinomas.
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Affiliation(s)
- Chengyin Min
- Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118-2394, USA
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19
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Puga A, Ma C, Marlowe JL. The aryl hydrocarbon receptor cross-talks with multiple signal transduction pathways. Biochem Pharmacol 2008; 77:713-22. [PMID: 18817753 DOI: 10.1016/j.bcp.2008.08.031] [Citation(s) in RCA: 288] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2008] [Revised: 08/20/2008] [Accepted: 08/21/2008] [Indexed: 12/13/2022]
Abstract
Exposure to toxic polycyclic aromatic hydrocarbons raises a number of toxic and carcinogenic responses in experimental animals and humans mediated for the most part by the aryl hydrocarbon -- or dioxin -- receptor (AHR). The AHR is a ligand-activated transcription factor whose central role in the induction of drug-metabolizing enzymes has long been recognized. For quite some time now, it has become clear that the AHR also functions in pathways outside of its role in detoxification and that perturbation of these pathways by xenobiotic ligands may be an important part of the toxicity of these compounds. AHR activation by some of its ligands participates among others in pathways critical to cell cycle regulation, mitogen-activated protein kinase cascades, immediate-early gene induction, cross-talk within the RB/E2F axis and mobilization of crucial calcium stores. Ultimately, the effect of a particular AHR ligand may depend as much on the adaptive interactions that it established with pathways and proteins expressed in a specific cell or tissue as on the toxic responses that it raises.
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Affiliation(s)
- Alvaro Puga
- Department of Environmental Health and Center for Environmental Genetics, University of Cincinnati College of Medicine, Cincinnati, OH 45220, USA.
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20
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Schlezinger JJ, Liu D, Farago M, Seldin DC, Belguise K, Sonenshein GE, Sherr DH. A role for the aryl hydrocarbon receptor in mammary gland tumorigenesis. Biol Chem 2008; 387:1175-87. [PMID: 16972784 DOI: 10.1515/bc.2006.145] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The aryl hydrocarbon receptor (AhR) is an evolutionarily conserved transcription factor bound and activated by ubiquitous environmental pollutants. Historically, the AhR has been studied for its transcriptional regulation of genes encoding cytochrome P450 enzymes, which metabolize many of these chemicals into mutagenic and toxic intermediates. However, recent studies demonstrate that the AhR plays an important role in the biology of several cell types in the absence of environmental chemicals. Here, this paradigm shift is discussed in the context of a putative role for the AhR in mammary gland tumorigenesis. Data demonstrating high levels of constitutively active AhR in mammary tumors are summarized. Particular focus is placed on the likelihood that the AhR contributes to ongoing mammary tumor cell growth and on the possibility that the AhR inhibits apoptosis while promoting transition to an invasive, metastatic phenotype. A working model is proposed that may help explain the sometimes contradictory outcomes observed after AhR manipulation and that serves as a blueprint for the design of therapeutics which target the AhR in breast cancer. The theme that malignant cells reveal the functions for which the AhR has been evolutionarily conserved is presented throughout this discussion.
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Affiliation(s)
- Jennifer J Schlezinger
- Department of Environmental Health, Boston University School of Public Health, Boston, MA 02118, USA
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21
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Murphy KA, Quadro L, White LA. The Intersection Between the Aryl Hydrocarbon Receptor (AhR)‐ and Retinoic Acid‐Signaling Pathways. VITAMIN A 2007; 75:33-67. [PMID: 17368311 DOI: 10.1016/s0083-6729(06)75002-6] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Data from a variety of animal and cell culture model systems have demonstrated an interaction between the aryl hydrocarbon receptor (AhR)- and retinoic acid (RA)-signaling pathways. The AhR(1) was originally identified as the receptor for the polycyclic aromatic hydrocarbon family of environmental contaminants; however, recent data indicate that the AhR binds to a variety of endogenous and exogenous compounds, including some synthetic retinoids. In addition, activation of the AhR pathway alters the function of nuclear hormone-signaling pathways, including the estrogen, thyroid, and RA pathways. Activation of the AhR pathway through exposure to environmental compounds results in significant changes in RA synthesis, catabolism, transport, and excretion. Some effects on retinoid homeostasis mediated by the AhR pathway may result from the interactions of these two pathways at the level of activating or repressing the expression of specific genes. This chapter will review these two pathways, the evidence demonstrating a link between them, and the data indicating the molecular basis of the interactions between these two pathways.
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Affiliation(s)
- Kyle A Murphy
- Department of Biochemistry and Microbiology, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08901, USA
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22
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Rifkind AB. CYP1A in TCDD toxicity and in physiology-with particular reference to CYP dependent arachidonic acid metabolism and other endogenous substrates. Drug Metab Rev 2006; 38:291-335. [PMID: 16684662 DOI: 10.1080/03602530600570107] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Toxicologic and physiologic roles of CYP1A enzyme induction, the major biochemical effect of aryl hydrocarbon receptor activation by TCDD and other receptor ligands, are unknown. Evidence is presented that CYP1A exerts biologic effects via metabolism of endogenous substrates (i.e., arachidonic acid, other eicosanoids, estrogens, bilirubin, and melatonin), production of reactive oxygen, and effects on K(+) and Ca(2+) channels. These interrelated pathways may connect CYP1A induction to TCDD toxicities, including cardiotoxicity, vascular dysfunction, and wasting. They may also underlie homeostatic roles for CYP1A, especially when transiently induced by common chemical exposures and environmental conditions (i.e., tryptophan photoproducts, dietary indoles, and changes in oxygen tension).
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Affiliation(s)
- Arleen B Rifkind
- Department of Pharmacology, Weill Medical College of Cornell University, New York, NY 10021, USA.
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23
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Kasper LH, Fukuyama T, Biesen MA, Boussouar F, Tong C, de Pauw A, Murray PJ, van Deursen JMA, Brindle PK. Conditional knockout mice reveal distinct functions for the global transcriptional coactivators CBP and p300 in T-cell development. Mol Cell Biol 2006; 26:789-809. [PMID: 16428436 PMCID: PMC1347027 DOI: 10.1128/mcb.26.3.789-809.2006] [Citation(s) in RCA: 162] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The global transcriptional coactivators CREB-binding protein (CBP) and the closely related p300 interact with over 312 proteins, making them among the most heavily connected hubs in the known mammalian protein-protein interactome. It is largely uncertain, however, if these interactions are important in specific cell lineages of adult animals, as homozygous null mutations in either CBP or p300 result in early embryonic lethality in mice. Here we describe a Cre/LoxP conditional p300 null allele (p300flox) that allows for the temporal and tissue-specific inactivation of p300. We used mice carrying p300flox and a CBP conditional knockout allele (CBPflox) in conjunction with an Lck-Cre transgene to delete CBP and p300 starting at the CD4- CD8- double-negative thymocyte stage of T-cell development. Loss of either p300 or CBP led to a decrease in CD4+ CD8+ double-positive thymocytes, but an increase in the percentage of CD8+ single-positive thymocytes seen in CBP mutant mice was not observed in p300 mutants. T cells completely lacking both CBP and p300 did not develop normally and were nonexistent or very rare in the periphery, however. T cells lacking CBP or p300 had reduced tumor necrosis factor alpha gene expression in response to phorbol ester and ionophore, while signal-responsive gene expression in CBP- or p300-deficient macrophages was largely intact. Thus, CBP and p300 each supply a surprising degree of redundant coactivation capacity in T cells and macrophages, although each gene has also unique properties in thymocyte development.
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Affiliation(s)
- Lawryn H Kasper
- Department of Biochemistry, St. Jude Children's Research Hospital, 332 N. Lauderdale, Memphis, TN 38105, USA
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24
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Yang X, Liu D, Murray TJ, Mitchell GC, Hesterman EV, Karchner SI, Merson RR, Hahn ME, Sherr DH. The aryl hydrocarbon receptor constitutively represses c-myc transcription in human mammary tumor cells. Oncogene 2005; 24:7869-81. [PMID: 16091746 DOI: 10.1038/sj.onc.1208938] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The aryl hydrocarbon receptor (AhR) is an environmental carcinogen-activated transcription factor associated with tumorigenesis. High levels of apparently active AhR characterize a variety of tumors, even in the absence of environmental ligands. Despite this association between transformation and AhR upregulation, little is known of the transcriptional consequences of constitutive AhR activation. Here, the effects of constitutively active and environmental ligand-induced AhR on c-myc, an oncogene whose promoter contains six AhR-binding sites (AhREs (aryl hydrocarbon response elements)), were investigated. A reporter containing the human c-myc promoter, with its six AhREs and two NF-kappaB-binding sites, was constructed. This vector, and variants with deletions in the NF-kappaB and/or AhR-binding sites, was transfected into a human breast cancer cell line, Hs578T, which expresses high levels of apparently active, nuclear AhR. Results indicate that: (1) the AhR constitutively binds the c-myc promoter; (2) there is a low but significant baseline level of c-myc promoter activity, which is not regulated by NF-kappaB and is not affected by an environmental AhR ligand; (3) deletion of any one of the AhREs has no effect on constitutive reporter activity, while deletion of all six increases reporter activity approximately fivefold; (4) a similar increase in reporter activity occurs when constitutively active AhR is suppressed by transfection with an AhR repressor plasmid (AhRR); (5) AhRR transfection significantly increases background levels of endogenous c-myc mRNA and c-Myc protein. These results suggest that the AhR influences the expression of c-Myc, a protein critical to malignant transformation.
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Affiliation(s)
- Xinhai Yang
- Department of Environmental Health, Boston University School of Public Health, Boston, MA 02118, USA
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25
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Mulero-Navarro S, Pozo-Guisado E, Pérez-Mancera PA, Alvarez-Barrientos A, Catalina-Fernández I, Hernández-Nieto E, Sáenz-Santamaria J, Martínez N, Rojas JM, Sánchez-García I, Fernández-Salguero PM. Immortalized mouse mammary fibroblasts lacking dioxin receptor have impaired tumorigenicity in a subcutaneous mouse xenograft model. J Biol Chem 2005; 280:28731-41. [PMID: 15946950 DOI: 10.1074/jbc.m504538200] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Although the dioxin receptor, the aryl hydrocarbon receptor (AhR), is considered a major regulator of xenobiotic-induced carcinogenesis, its role in tumor formation in the absence of xenobiotics is still largely unknown. Trying to address this question, we have produced immortalized cell lines from wild-type (T-FGM-AhR+/+) and mutant (T-FGM-AhR-/-) mouse mammary fibroblasts by stable co-transfection with the simian virus 40 (SV-40) large T antigen and proto-oncogenic c-H-Ras. Both cell lines had a myofibroblast phenotype and similar proliferation, doubling time, SV-40 and c-H-Ras expression and activity, and cell cycle distribution. AhR+/+ and AhR-/- cells were also equally able to support growth factor- and anchorage-independent proliferation. However, the ability of T-FGM-AhR-/- to induce subcutaneous tumors (leimyosarcomas) in NOD/SCID-immunodeficient mice was close to 4-fold lower than T-FGM-AhR+/+. In culture, T-FGM-AhR-/- had diminished migration in collagen-I and decreased lamellipodia formation. VEGFR-1/Flt-1, a VEGF receptor that regulates cell migration and blood vessel formation, was also down-regulated in AhR-/- cells. Signaling through the ERK-FAK-PKB/AKT-Rac-1 pathway, which contributes to cell motility and invasion, was also significantly inhibited in T-FGM-AhR-/-. Thus, the lower tumorigenic potential of T-FGM-AhR-/- could result from a compromised adaptability of these cells to the in vivo microenvironment, possibly because of an impaired ability to migrate and to respond to angiogenesis.
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Affiliation(s)
- Sonia Mulero-Navarro
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias, Universidad de Extremadura, Avenida de Elvas s/n, 06071 Badajoz, Spain
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26
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Marlowe JL, Puga A. Aryl hydrocarbon receptor, cell cycle regulation, toxicity, and tumorigenesis. J Cell Biochem 2005; 96:1174-84. [PMID: 16211578 DOI: 10.1002/jcb.20656] [Citation(s) in RCA: 237] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Most effects of exposure to halogenated and polycyclic aromatic hydrocarbons are mediated by the aryl hydrocarbon receptor (AHR). It has long been recognized that the AHR is a ligand-activated transcription factor that plays a central role in the induction of drug-metabolizing enzymes and hence in xenobiotic detoxification. Of late, it has become evident that outside this well-characterized role, the AHR also functions as a modulator of cellular signaling pathways. In this Prospect, we discuss the involvement of the AHR in pathways critical to cell cycle regulation, mitogen-activated protein kinase cascades, immediate-early gene induction, and the functions of the RB protein. Ultimately, the toxicity of AHR xenobiotic ligands may be intrinsically connected with the perturbation of these pathways and depend on the many critical signaling pathways and effectors with which the AHR itself interacts.
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Affiliation(s)
- Jennifer L Marlowe
- Department of Environmental Health and Center for Environmental Genetics, University of Cincinnati Medical Center, Cincinnati, Ohio 45267-0056, USA
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27
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Huang G, Elferink CJ. Multiple mechanisms are involved in Ah receptor-mediated cell cycle arrest. Mol Pharmacol 2004; 67:88-96. [PMID: 15492120 DOI: 10.1124/mol.104.002410] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The liver is the only solid organ that can respond to major tissue loss or damage by regeneration to restore liver biomass. The aryl hydrocarbon receptor (AhR) agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) can disrupt the regenerative process, as evidenced by suppression of DNA synthesis in rat primary hepatocytes in culture and in vivo liver regeneration after partial hepatectomy. Independent observations demonstrated that AhR-mediated G(1) phase cell cycle arrest depends on an interaction with the retinoblastoma tumor suppressor protein (pRb), but differences exist regarding proposed mechanisms of action. Two distinct models have been proposed, one supporting the AhR-pRb interaction functioning in corepression of E2F activity and the other favoring an AhR-pRb interaction participating in transcriptional coactivation of genes encoding G(1) phase regulatory proteins. In the present study, experiments in rat hepatoma cells using dominant-negative DNA-binding-defective AhR and Ah receptor nuclear translocator (Arnt) mutants provided evidence that TCDD-induced AhR-mediated G(1) arrest is only partially regulated by direct AhR transcriptional activity, suggesting that both coactivation and corepression are involved. Studies using a small interfering RNA to down-regulate Arnt protein expression revealed that TCDD-induced G(1) arrest is absolutely dependent on the Arnt protein.
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Affiliation(s)
- Gengming Huang
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX, USA
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28
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Levine-Fridman A, Chen L, Elferink CJ. Cytochrome P4501A1 promotes G1 phase cell cycle progression by controlling aryl hydrocarbon receptor activity. Mol Pharmacol 2004; 65:461-9. [PMID: 14742689 DOI: 10.1124/mol.65.2.461] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The aryl hydrocarbon receptor (AhR) transcription factor is increasingly recognized as functioning in cell cycle control. Several recent reports have shown that AhR activity in the absence of exogenous agonists or presence of the prototypical ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin can affect G1 phase progression in cultured cells. Serum release of serum-starved (G0) 5L rat hepatoma cells triggers transient AhR activation and P4501A1 protein expression concomitant with the G0/G1-to-S phase transition. In contrast, sustained AhR activation in response to TCDD treatment increases p27Kip1 expression in addition to P4501A1, resulting in G1 phase cell cycle arrest. Treating serum-released 5L cells with the alkyne metabolism-based P4501A1 inhibitor 1-(1-propynyl)pyrene results in prolonged AhR activation, enhanced p27Kip1 expression, and G1 phase arrest after serum release. The data are consistent with a cell cycle role for P4501A1 because they show that P4501A1 negatively regulates the duration of AhR action through the metabolic removal of the receptor agonist, thereby preventing AhR-mediated G1 phase arrest.
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Affiliation(s)
- Aviva Levine-Fridman
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, Texas 77555-1031, USA
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29
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Huang X, Powell-Coffman JA, Jin Y. The AHR-1 aryl hydrocarbon receptor and its co-factor the AHA-1 aryl hydrocarbon receptor nuclear translocator specify GABAergic neuron cell fate inC. elegans. Development 2004; 131:819-28. [PMID: 14757639 DOI: 10.1242/dev.00959] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The aryl hydrocarbon receptors (AHR) are bHLH-PAS domain containing transcription factors. In mammals, they mediate responses to environmental toxins such as 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD). Such functions of AHRs require a cofactor, the aryl hydrocarbon receptor nuclear translocator (ARNT), and the cytoplasmic chaperonins HSP90 and XAP2. AHR homologs have been identified throughout the animal kingdom. We report here that the C. elegans orthologs of AHR and ARNT, ahr-1 and aha-1, regulate GABAergic motor neuron fate specification. Four C. elegans neurons known as RMED, RMEV, RMEL and RMER express the neurotransmitter GABA and control head muscle movements. ahr-1 is expressed in RMEL and RMER neurons. Loss of function in ahr-1 causes RMEL and RMER neurons to adopt a RMED/RMEV-like fate, whereas the ectopic expression of ahr-1 in RMED and RMEV neurons can transform them into RMEL/RMER-like neurons. This function of ahr-1 requires aha-1, but not daf-21/hsp90. Our results demonstrate that C. elegans ahr-1 functions as a cell-type specific determinant. This study further supports the notion that the ancestral role of the AHR proteins is in regulating cellular differentiation in animal development.
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Affiliation(s)
- Xun Huang
- Department of Molecular, Cellular and Developmental Biology, Howard Hughes Medical Institute, University of California, Santa Cruz, CA 95064, USA
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30
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Santiago-Josefat B, Mulero-Navarro S, Dallas SL, Fernandez-Salguero PM. Overexpression of latent transforming growth factor-beta binding protein 1 (LTBP-1) in dioxin receptor-null mouse embryo fibroblasts. J Cell Sci 2004; 117:849-59. [PMID: 14762110 DOI: 10.1242/jcs.00932] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The aryl hydrocarbon receptor (AhR) is a transcriptional regulator of genes involved in xenobiotic metabolism. Increasingly clear is also the role of the AhR in the control of cell growth and proliferation. By analyzing differential patterns of gene expression between wild-type (AhR+/+) and null (AhR-/-) mouse embryo fibroblasts (MEF), we have identified latent transforming growth factor-beta binding protein 1 (LTBP-1) as a negatively AhR-regulated gene in the absence of xenobiotics. Ltbp-1 mRNA and protein expression were markedly increased in AhR-/- MEF. Furthermore, secreted LTBP-1 was elevated in the culture medium and the extracellular matrix of AhR-null MEF. Actinomycin D inhibited Ltbp-1 mRNA overexpression, suggesting regulation at the transcriptional level. AhR activation by dioxin (TCDD) downregulated Ltbp-1, again suggesting an AhR-regulated mechanism. Treatment of AhR+/+ MEF with transforming growth factor-beta(TGF-beta) downregulated AhR and, simultaneously, increased Ltbp-1, further supporting the role of this receptor in LTBP-1 expression. AhR-/- conditioned medium had higher levels of active and total TGF-beta activity, suggesting a role for LTBP-1 in maintaining extracellular TGF-beta concentrations. TGF-beta did not appear to directly regulate Ltbp-1 given that addition of TGFbeta neutralizing antibody or TGFbeta protein to AhR-/- MEF had no effect on Ltbp-1 expression. AhR-/- MEF had lower levels of matrix metalloproteinase 2 (MMP-2) activity, which could not be attributable to MMP-2 mRNA downregulation or MMP-inhibitors Timp-1 and Timp-2 overexpression. These data identify LTBP-1 as one of the few AhR-regulated genes not involved in xenobiotic metabolism and also support the implication of the AhR in controlling TGFbeta activity and cell proliferation.
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Affiliation(s)
- Belen Santiago-Josefat
- Departamento de Bioquimica y Biologia Molecular, Facultad de Ciencias, Universidad de Extremadura, Avenida de Elvas s/n, 06071-Badajoz, Spain
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31
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Carlson DB, Perdew GH. A dynamic role for the Ah receptor in cell signaling? Insights from a diverse group of Ah receptor interacting proteins. J Biochem Mol Toxicol 2003; 16:317-25. [PMID: 12481307 DOI: 10.1002/jbt.10051] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The aryl hydrocarbon (Ah) receptor (AhR) is a member of the basic helix-loop-helix PER-ARNT-SIM (PAS) transcription factor family. Consistent with the notion that PAS proteins are biological sensors, AhR binding to Ah toxicants induces or represses transcription of a wide range of genes and results in a cascade of toxic responses. However, an endogenous role for AhR in development and homeostasis is supported by (1) the discovery of low affinity, endogenous ligands; (2) studies demonstrating a role for the receptor in development of liver and vascular systems, that were established using mice lacking AhR expression; and (3) the presence of functional dioxin-responsive elements in promoter regions of genes involved in cellular growth and differentiation. A large body of recent literature has implicated AhR in multiple signal transduction pathways. AhR is known to interact with signaling pathways that are mediated by estrogen receptor and other hormone receptors, hypoxia, nuclear factor kappaB, and retinoblastoma protein. In addition, AhR complexes may affect cellular signaling through interactions with various other regulatory and signaling proteins, including PAS heterodimerization partners (ARNT), chaperone and immunophilin-like proteins (e.g. HSP90, XAP2/ARA9/AIP, p23), protein kinases and phosphatases (e.g. tyrosine kinases, casein kinase 2, protein kinase C), and coactivators (e.g. SRC-1, RIP 140, CBP/p300). Here we summarize the types of molecular cross talk that have been identified between AhR and cell signaling pathways.
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Affiliation(s)
- David B Carlson
- Center for Molecular Toxicology and Carcinogenesis, Department of Veterinary Science, Pennsylvania State University, University Park, PA 16802, USA
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Swanson HI. DNA binding and protein interactions of the AHR/ARNT heterodimer that facilitate gene activation. Chem Biol Interact 2002; 141:63-76. [PMID: 12213385 DOI: 10.1016/s0009-2797(02)00066-2] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Gene activation by the aryl hydrocarbon receptor (AHR) and its DNA binding partner, the aryl hydrocarbon receptor nuclear translocator (ARNT) requires a number of sequential steps that occur following the binding of ligand and entry of the AHR into the nuclear compartment. This includes heterodimerization of the AHR and ARNT, formation of the appropriate amino acid/nucleotide contacts at the GCGTG recognition site and interactions between either the AHR or ARNT with proteins that facilitate changes in chromatin structure. The majority of these steps are likely modulated by changes in both phosphorylation and oxidation status of the AHR, ARNT and associated proteins. Studies of both the basic helix-loop-helix transcription factors and the nuclear hormone receptor family can provide significant insights into how this unique signaling pathway activates its target genes.
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Affiliation(s)
- Hollie I Swanson
- Department of Molecular and Biomedical Pharmacology, University of Kentucky Medical Center, MS 303, Lexington 40536, USA.
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Abstract
Traditionally, the aryl hydrocarbon receptor (AHR) is considered to be a ligand-activated receptor and transcription factor responsible for the induction of drug-metabolizing enzymes. Its role in the combinatorial matrix of cell functions was neatly established long before the first report of an AHR cDNA sequence was published. Only recently, other functions of this protein have begun to be recognized. This review addresses novel findings relating to AHR functions that have resulted from experimental approaches markedly outside traditional receptor analyses. Here we examine the aspects of AHR biology relevant to its role in cell cycle regulation, from the activation of mitogen-activated protein kinases to the cross-talk between AHR and the RAS pathway and the functional significance of the interaction between AHR and the retinoblastoma protein. We have attempted to provide the reader with a balanced interpretation of the evidence, highlighting areas of consensus as well as areas still being contested.
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Affiliation(s)
- Alvaro Puga
- Center for Environmental Genetics and Department of Environmental Health, University of Cincinnati Medical Center, P.O. Box 670056, OH 45267-0056, USA.
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