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Promoter bivalency favors an open chromatin architecture in embryonic stem cells. Nat Genet 2018; 50:1452-1462. [PMID: 30224650 DOI: 10.1038/s41588-018-0218-5] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2017] [Accepted: 08/01/2018] [Indexed: 11/08/2022]
Abstract
In embryonic stem cells (ESCs), developmental gene promoters are characterized by their bivalent chromatin state, with simultaneous modification by MLL2 and Polycomb complexes. Although essential for embryogenesis, bivalency is functionally not well understood. Here, we show that MLL2 plays a central role in ESC genome organization. We generate a catalog of bona fide bivalent genes in ESCs and demonstrate that loss of MLL2 leads to increased Polycomb occupancy. Consequently, promoters lose accessibility, long-range interactions are redistributed, and ESCs fail to differentiate. We pose that bivalency balances accessibility and long-range connectivity of promoters, allowing developmental gene expression to be properly modulated.
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52
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Zhang L, Ettou S, Khalid M, Taglienti M, Jain D, Jung YL, Seager C, Liu Y, Ng KH, Park PJ, Kreidberg JA. EED, a member of the polycomb group, is required for nephron differentiation and the maintenance of nephron progenitor cells. Development 2018; 145:dev.157149. [PMID: 29945864 DOI: 10.1242/dev.157149] [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] [Received: 07/12/2017] [Accepted: 06/14/2018] [Indexed: 12/26/2022]
Abstract
Epigenetic regulation of gene expression has a crucial role allowing for the self-renewal and differentiation of stem and progenitor populations during organogenesis. The mammalian kidney maintains a population of self-renewing stem cells that differentiate to give rise to thousands of nephrons, which are the functional units that carry out filtration to maintain physiological homeostasis. The polycomb repressive complex 2 (PRC2) epigenetically represses gene expression during development by placing the H3K27me3 mark on histone H3 at promoter and enhancer sites, resulting in gene silencing. To understand the role of PRC2 in nephron differentiation, we conditionally inactivated the Eed gene, which encodes a nonredundant component of the PRC2 complex, in nephron progenitor cells. Resultant kidneys were smaller and showed premature loss of progenitor cells. The progenitors in Eed mutant mice that were induced to differentiate did not develop into properly formed nephrons. Lhx1, normally expressed in the renal vesicle, was overexpressed in kidneys of Eed mutant mice. Thus, PRC2 has a crucial role in suppressing the expression of genes that maintain the progenitor state, allowing nephron differentiation to proceed.
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Affiliation(s)
- Le Zhang
- Department of Urology, Boston Children's Hospital, Boston, MA 02115, USA.,Division of Nephrology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Sandrine Ettou
- Department of Urology, Boston Children's Hospital, Boston, MA 02115, USA.,Department of Surgery, Harvard Medical School, Boston, MA 02115, USA
| | - Myda Khalid
- Division of Nephrology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.,Department of Pediatrics, Harvard Medical School, Boston, MA 02115, USA
| | - Mary Taglienti
- Department of Urology, Boston Children's Hospital, Boston, MA 02115, USA
| | - Dhawal Jain
- Biomedical Informatics, Harvard Medical School, Boston, MA 02115, USA
| | - Youngsook L Jung
- Biomedical Informatics, Harvard Medical School, Boston, MA 02115, USA
| | - Catherine Seager
- Department of Urology, Boston Children's Hospital, Boston, MA 02115, USA.,Department of Surgery, Harvard Medical School, Boston, MA 02115, USA
| | - Yongqing Liu
- Department of Pediatrics, Harvard Medical School, Boston, MA 02115, USA
| | - Kar-Hui Ng
- Department of Pediatrics, Harvard Medical School, Boston, MA 02115, USA
| | - Peter J Park
- Biomedical Informatics, Harvard Medical School, Boston, MA 02115, USA
| | - Jordan A Kreidberg
- Department of Urology, Boston Children's Hospital, Boston, MA 02115, USA .,Division of Nephrology, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.,Department of Surgery, Harvard Medical School, Boston, MA 02115, USA.,Department of Pediatrics, Harvard Medical School, Boston, MA 02115, USA.,Harvard Stem Cell Institute, Cambridge, MA 02139, USA
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53
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Polycomb-Dependent Chromatin Looping Contributes to Gene Silencing during Drosophila Development. Mol Cell 2018; 71:73-88.e5. [DOI: 10.1016/j.molcel.2018.05.032] [Citation(s) in RCA: 143] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Revised: 04/12/2018] [Accepted: 05/24/2018] [Indexed: 01/21/2023]
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Abstract
Polycomb Group (PcG) proteins assemble a chromatin state that maintains developmental gene repression. A new study combining structure and in vivo analysis details a molecular network from DNA recognition to PcG recruitment, highlighting the essential role of Sterile Alpha Motifs.
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Affiliation(s)
- Chongwoo A Kim
- Department of Biochemistry, Midwestern University, 19555 N. 59th Avenue, Glendale, AZ 85308, USA
| | - Nicole J Francis
- Institut de recherches cliniques de Montréal, Montréal, Québec, Canada; Département de biochimie et medécine moléculaire, Université de Montréal, Montréal, Québec, Canada.
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55
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Keep Them Close: PRC2 Poises Enhancer-Promoter Interactions at Anterior Neuronal Genes. Cell Stem Cell 2018; 20:573-575. [PMID: 28475876 DOI: 10.1016/j.stem.2017.04.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Enhancers exist in different epigenetic states: active, primed, or poised. However, it is not yet understood how the different enhancer states influence gene activation. In this issue of Cell Stem Cell, Cruz-Molina et al. (2017) unravel how poised enhancers activate anterior neural genes and the role of Polycomb proteins in enhancer-promoter contacts.
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56
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Khan S, Iqbal M, Tariq M, Baig SM, Abbas W. Epigenetic regulation of HIV-1 latency: focus on polycomb group (PcG) proteins. Clin Epigenetics 2018; 10:14. [PMID: 29441145 PMCID: PMC5800276 DOI: 10.1186/s13148-018-0441-z] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Accepted: 01/05/2018] [Indexed: 01/10/2023] Open
Abstract
HIV-1 latency allows the virus to persist until reactivation, in a transcriptionally silent form in its cellular reservoirs despite the presence of effective cART. Such viral persistence represents a major barrier to HIV eradication since treatment interruption leads to rebound plasma viremia. Polycomb group (PcG) proteins have recently got a considerable attention in regulating HIV-1 post-integration latency as they are involved in the repression of proviral gene expression through the methylation of histones. This epigenetic regulation plays an important role in the establishment and maintenance of HIV-1 latency. In fact, PcG proteins act in complexes and modulate the epigenetic signatures of integrated HIV-1 promoter. Key role played by PcG proteins in the molecular control of HIV-1 latency has led to hypothesize that PcG proteins may represent a valuable target for future HIV-1 therapy in purging HIV-1 reservoirs. In this regard, various small molecules have been synthesized or explored to specifically block the epigenetic activity of PcG. In this review, we will highlight the possible therapeutic approaches to achieve either a functional or sterilizing cure of HIV-1 infection with special focus on histone methylation by PcG proteins together with current and novel pharmacological approaches to reactivate HIV-1 from latency that could ultimately lead towards a better clearance of viral latent reservoirs.
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Affiliation(s)
- Sheraz Khan
- Health Biotechnology Division (HBD), National Institute for Biotechnology and Genetic Engineering (NIBGE), PO Box 577, Jhang road, Faisalabad, 38000 Pakistan
- Pakistan Institute of Engineering and Applied Sciences (PIEAS), Nilore, Islamabad, Pakistan
| | - Mazhar Iqbal
- Health Biotechnology Division (HBD), National Institute for Biotechnology and Genetic Engineering (NIBGE), PO Box 577, Jhang road, Faisalabad, 38000 Pakistan
- Pakistan Institute of Engineering and Applied Sciences (PIEAS), Nilore, Islamabad, Pakistan
| | - Muhammad Tariq
- Department of Biology (Epigenetics group), SBA School of Science and Engineering, LUMS, Lahore, 54792 Pakistan
| | - Shahid M. Baig
- Health Biotechnology Division (HBD), National Institute for Biotechnology and Genetic Engineering (NIBGE), PO Box 577, Jhang road, Faisalabad, 38000 Pakistan
- Pakistan Institute of Engineering and Applied Sciences (PIEAS), Nilore, Islamabad, Pakistan
| | - Wasim Abbas
- Health Biotechnology Division (HBD), National Institute for Biotechnology and Genetic Engineering (NIBGE), PO Box 577, Jhang road, Faisalabad, 38000 Pakistan
- Pakistan Institute of Engineering and Applied Sciences (PIEAS), Nilore, Islamabad, Pakistan
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57
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DNA methylation regulates TMEM16A/ANO1 expression through multiple CpG islands in head and neck squamous cell carcinoma. Sci Rep 2017; 7:15173. [PMID: 29123240 PMCID: PMC5680248 DOI: 10.1038/s41598-017-15634-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Accepted: 10/31/2017] [Indexed: 01/22/2023] Open
Abstract
ANO1 is a calcium-activated chloride channel that is frequently overexpressed in head and neck squamous cell carcinoma (HNSCC) and other cancers. While ANO1 expression negatively correlates with survival in several cancers, its epigenetic regulation is poorly understood. We analyzed HNSCC samples from TCGA and a separate dataset of HPV+ oropharyngeal squamous cell carcinoma (OPSCC) samples to identify differentially methylated regions. E6 and E7 transfected normal oral keratinocytes (NOK) were used to induce hypermethylation of the ANO1 promoter. We found three CpG islands that correlated with ANO1 expression, including two positively correlated with expression. Using two HNSCC datasets with differential expression of ANO1, we showed hypermethylation of positively correlated CpG islands potentiates ANO1 expression. E7 but not E6 transfection of NOK cells led to hypermethylation of a positively correlated CpG island without a change in ANO1 expression. ANO1 promoter methylation was also correlated with patient survival. Our results are the first to show the contribution of positively correlated CpG’s for regulating gene expression in HNSCC. Hypermethylation of the ANO1 promoter was strongly correlated with but not sufficient to increase ANO1 expression, suggesting methylation of positively correlated CpG’s likely serves as an adjunct to other mechanisms of ANO1 activation.
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58
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Samd7 is a cell type-specific PRC1 component essential for establishing retinal rod photoreceptor identity. Proc Natl Acad Sci U S A 2017; 114:E8264-E8273. [PMID: 28900001 DOI: 10.1073/pnas.1707021114] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Precise transcriptional regulation controlled by a transcription factor network is known to be crucial for establishing correct neuronal cell identities and functions in the CNS. In the retina, the expression of various cone and rod photoreceptor cell genes is regulated by multiple transcription factors; however, the role of epigenetic regulation in photoreceptor cell gene expression has been poorly understood. Here, we found that Samd7, a rod-enriched sterile alpha domain (SAM) domain protein, is essential for silencing nonrod gene expression through H3K27me3 regulation in rod photoreceptor cells. Samd7-null mutant mice showed ectopic expression of nonrod genes including S-opsin in rod photoreceptor cells and rod photoreceptor cell dysfunction. Samd7 physically interacts with Polyhomeotic homologs (Phc proteins), components of the Polycomb repressive complex 1 (PRC1), and colocalizes with Phc2 and Ring1B in Polycomb bodies. ChIP assays showed a significant decrease of H3K27me3 in the genes up-regulated in the Samd7-deficient retina, showing that Samd7 deficiency causes the derepression of nonrod gene expression in rod photoreceptor cells. The current study suggests that Samd7 is a cell type-specific PRC1 component epigenetically defining rod photoreceptor cell identity.
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Kundu S, Ji F, Sunwoo H, Jain G, Lee JT, Sadreyev RI, Dekker J, Kingston RE. Polycomb Repressive Complex 1 Generates Discrete Compacted Domains that Change during Differentiation. Mol Cell 2017; 65:432-446.e5. [PMID: 28157505 DOI: 10.1016/j.molcel.2017.01.009] [Citation(s) in RCA: 218] [Impact Index Per Article: 31.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Revised: 11/08/2016] [Accepted: 01/05/2017] [Indexed: 12/27/2022]
Abstract
Master regulatory genes require stable silencing by the polycomb group (PcG) to prevent misexpression during differentiation and development. Some PcG proteins covalently modify histones, which contributes to heritable repression. The role for other effects on chromatin structure is less understood. We characterized the organization of PcG target genes in ESCs and neural progenitors using 5C and super-resolution microscopy. The genomic loci of repressed PcG targets formed discrete, small (20-140 Kb) domains of tight interaction that corresponded to locations bound by canonical polycomb repressive complex 1 (PRC1). These domains changed during differentiation as PRC1 binding changed. Their formation depended upon the Polyhomeotic component of canonical PRC1 and occurred independently of PRC1-catalyzed ubiquitylation. PRC1 domains differ from topologically associating domains in size and boundary characteristics. These domains have the potential to play a key role in transmitting epigenetic silencing of PcG targets by linking PRC1 to formation of a repressive higher-order structure.
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Affiliation(s)
- Sharmistha Kundu
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
| | - Fei Ji
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
| | - Hongjae Sunwoo
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
| | - Gaurav Jain
- Program in Systems Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Jeannie T Lee
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02115, USA; Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA; Howard Hughes Medical Institute, Boston, MA 02115, USA
| | - Ruslan I Sadreyev
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA
| | - Job Dekker
- Howard Hughes Medical Institute, Boston, MA 02115, USA; Program in Systems Biology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Robert E Kingston
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02115, USA.
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60
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Schuettengruber B, Bourbon HM, Di Croce L, Cavalli G. Genome Regulation by Polycomb and Trithorax: 70 Years and Counting. Cell 2017; 171:34-57. [DOI: 10.1016/j.cell.2017.08.002] [Citation(s) in RCA: 611] [Impact Index Per Article: 87.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Revised: 07/17/2017] [Accepted: 08/01/2017] [Indexed: 01/05/2023]
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61
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Srivastava A, McGrath B, Bielas SL. Histone H2A Monoubiquitination in Neurodevelopmental Disorders. Trends Genet 2017; 33:566-578. [PMID: 28669576 PMCID: PMC5562288 DOI: 10.1016/j.tig.2017.06.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Accepted: 06/05/2017] [Indexed: 11/21/2022]
Abstract
Covalent histone modifications play an essential role in gene regulation and cellular specification required for multicellular organism development. Monoubiquitination of histone H2A (H2AUb1) is a reversible transcriptionally repressive mark. Exchange of histone H2A monoubiquitination and deubiquitination reflects the succession of transcriptional profiles during development required to produce cellular diversity from pluripotent cells. Germ-line pathogenic variants in components of the H2AUb1 regulatory axis are being identified as the genetic basis of congenital neurodevelopmental disorders. Here, we review the human genetics findings coalescing on molecular mechanisms that alter the genome-wide distribution of this histone modification required for development.
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Affiliation(s)
- Anshika Srivastava
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Brian McGrath
- Cell and Molecular Biology Program, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Stephanie L Bielas
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor, MI, USA; Cell and Molecular Biology Program, University of Michigan Medical School, Ann Arbor, MI, USA.
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62
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Molecular architecture of polycomb repressive complexes. Biochem Soc Trans 2017; 45:193-205. [PMID: 28202673 PMCID: PMC5310723 DOI: 10.1042/bst20160173] [Citation(s) in RCA: 127] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Revised: 11/24/2016] [Accepted: 12/02/2016] [Indexed: 01/05/2023]
Abstract
The polycomb group (PcG) proteins are a large and diverse family that epigenetically repress the transcription of key developmental genes. They form three broad groups of polycomb repressive complexes (PRCs) known as PRC1, PRC2 and Polycomb Repressive DeUBiquitinase, each of which modifies and/or remodels chromatin by distinct mechanisms that are tuned by having variable compositions of core and accessory subunits. Until recently, relatively little was known about how the various PcG proteins assemble to form the PRCs; however, studies by several groups have now allowed us to start piecing together the PcG puzzle. Here, we discuss some highlights of recent PcG structures and the insights they have given us into how these complexes regulate transcription through chromatin.
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63
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Three-Dimensional Genome Organization and Function in Drosophila. Genetics 2017; 205:5-24. [PMID: 28049701 PMCID: PMC5223523 DOI: 10.1534/genetics.115.185132] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Accepted: 10/15/2016] [Indexed: 12/18/2022] Open
Abstract
Understanding how the metazoan genome is used during development and cell differentiation is one of the major challenges in the postgenomic era. Early studies in Drosophila suggested that three-dimensional (3D) chromosome organization plays important regulatory roles in this process and recent technological advances started to reveal connections at the molecular level. Here we will consider general features of the architectural organization of the Drosophila genome, providing historical perspective and insights from recent work. We will compare the linear and spatial segmentation of the fly genome and focus on the two key regulators of genome architecture: insulator components and Polycomb group proteins. With its unique set of genetic tools and a compact, well annotated genome, Drosophila is poised to remain a model system of choice for rapid progress in understanding principles of genome organization and to serve as a proving ground for development of 3D genome-engineering techniques.
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64
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Cruz-Molina S, Respuela P, Tebartz C, Kolovos P, Nikolic M, Fueyo R, van Ijcken WF, Grosveld F, Frommolt P, Bazzi H, Rada-Iglesias A. PRC2 Facilitates the Regulatory Topology Required for Poised Enhancer Function during Pluripotent Stem Cell Differentiation. Cell Stem Cell 2017; 20:689-705.e9. [DOI: 10.1016/j.stem.2017.02.004] [Citation(s) in RCA: 151] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2016] [Revised: 12/19/2016] [Accepted: 02/07/2017] [Indexed: 01/28/2023]
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65
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Zhou Y, Romero-Campero FJ, Gómez-Zambrano Á, Turck F, Calonje M. H2A monoubiquitination in Arabidopsis thaliana is generally independent of LHP1 and PRC2 activity. Genome Biol 2017; 18:69. [PMID: 28403905 PMCID: PMC5389094 DOI: 10.1186/s13059-017-1197-z] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 03/22/2017] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Polycomb group complexes PRC1 and PRC2 repress gene expression at the chromatin level in eukaryotes. The classic recruitment model of Polycomb group complexes in which PRC2-mediated H3K27 trimethylation recruits PRC1 for H2A monoubiquitination was recently challenged by data showing that PRC1 activity can also recruit PRC2. However, the prevalence of these two mechanisms is unknown, especially in plants as H2AK121ub marks were examined at only a handful of Polycomb group targets. RESULTS By using genome-wide analyses, we show that H2AK121ub marks are surprisingly widespread in Arabidopsis thaliana, often co-localizing with H3K27me3 but also occupying a set of transcriptionally active genes devoid of H3K27me3. Furthermore, by profiling H2AK121ub and H3K27me3 marks in atbmi1a/b/c, clf/swn, and lhp1 mutants we found that PRC2 activity is not required for H2AK121ub marking at most genes. In contrast, loss of AtBMI1 function impacts the incorporation of H3K27me3 marks at most Polycomb group targets. CONCLUSIONS Our findings show the relationship between H2AK121ub and H3K27me3 marks across the A. thaliana genome and unveil that ubiquitination by PRC1 is largely independent of PRC2 activity in plants, while the inverse is true for H3K27 trimethylation.
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Affiliation(s)
- Yue Zhou
- Max Planck Institute for Plant Breeding Research, Department of Plant Developmental Biology, Cologne, Germany
| | | | - Ángeles Gómez-Zambrano
- Institute of Plant Biochemistry and Photosynthesis (IBVF-CSIC-University of Sevilla), Seville, Spain
| | - Franziska Turck
- Max Planck Institute for Plant Breeding Research, Department of Plant Developmental Biology, Cologne, Germany.
| | - Myriam Calonje
- Institute of Plant Biochemistry and Photosynthesis (IBVF-CSIC-University of Sevilla), Seville, Spain.
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66
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Freire-Pritchett P, Schoenfelder S, Várnai C, Wingett SW, Cairns J, Collier AJ, García-Vílchez R, Furlan-Magaril M, Osborne CS, Fraser P, Rugg-Gunn PJ, Spivakov M. Global reorganisation of cis-regulatory units upon lineage commitment of human embryonic stem cells. eLife 2017; 6:21926. [PMID: 28332981 PMCID: PMC5407860 DOI: 10.7554/elife.21926] [Citation(s) in RCA: 106] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Accepted: 03/22/2017] [Indexed: 12/19/2022] Open
Abstract
Long-range cis-regulatory elements such as enhancers coordinate cell-specific transcriptional programmes by engaging in DNA looping interactions with target promoters. Deciphering the interplay between the promoter connectivity and activity of cis-regulatory elements during lineage commitment is crucial for understanding developmental transcriptional control. Here, we use Promoter Capture Hi-C to generate a high-resolution atlas of chromosomal interactions involving ~22,000 gene promoters in human pluripotent and lineage-committed cells, identifying putative target genes for known and predicted enhancer elements. We reveal extensive dynamics of cis-regulatory contacts upon lineage commitment, including the acquisition and loss of promoter interactions. This spatial rewiring occurs preferentially with predicted changes in the activity of cis-regulatory elements and is associated with changes in target gene expression. Our results provide a global and integrated view of promoter interactome dynamics during lineage commitment of human pluripotent cells. DOI:http://dx.doi.org/10.7554/eLife.21926.001 Virtually every cell in the body contains the same set of DNA, which encodes thousands of genes. The activities of these genes vary between different types of cells and at different points in time. As a result, our DNA contains a complex array of molecular switches that instruct genes to switch on and off at the right time and in the right cells. These molecular switches, termed regulatory elements, are often a long way away from the genes that they control, and this can make it difficult to find out which switch controls which genes. DNA is made up of several different building blocks known as bases and the order of these bases encodes specific information about the gene. Every human cell contains approximately two meters of DNA, which is highly folded in the cell nucleus. This three-dimensional folding allows regions that are far apart on the DNA thread to physically contact each other. To reach the genes they control, regulatory elements form loops on the DNA that are near-impossible to predict from looking at the sequence of bases alone. Mapping the locations of these loops can reveal the hidden circuitry within our DNA and help us to understand how unwanted changes (mutations) within regulatory elements may cause disease. Freire-Pritchett, Schoenfelder et al. set out to reveal how loops between genes and their regulatory elements change as the stem cells specialise into immature brain cells. The experiments show that the pattern of DNA loops is extensively altered after the stem cells specialise into brain cells, that is, some loops are lost and new ones form. Furthermore, the regulatory elements themselves were often toggled between “on” and “off” states. These two processes tend to occur together, so that new loops are formed at the same time as the switch is activated. Freire-Pritchett, Schoenfelder et al. also show that individual genes are often connected to many different regulatory elements. The next step is to understand how these multiple connections work together to coordinate gene activity, and whether this information could be used to control how stem cells specialise. This knowledge may lead to the development of stem cell-based therapies for stroke, Parkinson’s disease and other conditions. DOI:http://dx.doi.org/10.7554/eLife.21926.002
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Affiliation(s)
| | | | - Csilla Várnai
- Nuclear Dynamics Programme, Babraham Institute, Cambridge, United Kingdom
| | - Steven W Wingett
- Nuclear Dynamics Programme, Babraham Institute, Cambridge, United Kingdom
| | - Jonathan Cairns
- Nuclear Dynamics Programme, Babraham Institute, Cambridge, United Kingdom
| | - Amanda J Collier
- Epigenetics Programme, Babraham Institute, Cambridge, United Kingdom.,Wellcome Trust - Medical Research Council Cambridge Stem Cell Institute, University of Cambridge, Cambridge, United Kingdom
| | | | | | - Cameron S Osborne
- Department of Genetics and Molecular Medicine, King's College London School of Medicine, London, United Kingdom
| | - Peter Fraser
- Nuclear Dynamics Programme, Babraham Institute, Cambridge, United Kingdom
| | - Peter J Rugg-Gunn
- Epigenetics Programme, Babraham Institute, Cambridge, United Kingdom.,Wellcome Trust - Medical Research Council Cambridge Stem Cell Institute, University of Cambridge, Cambridge, United Kingdom
| | - Mikhail Spivakov
- Nuclear Dynamics Programme, Babraham Institute, Cambridge, United Kingdom
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67
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Kronfol MM, Dozmorov MG, Huang R, Slattum PW, McClay JL. The role of epigenomics in personalized medicine. EXPERT REVIEW OF PRECISION MEDICINE AND DRUG DEVELOPMENT 2017; 2:33-45. [PMID: 29276780 DOI: 10.1080/23808993.2017.1284557] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Introduction Epigenetics is the study of reversible modifications to chromatin and their extensive and profound effects on gene regulation. To date, the role of epigenetics in personalized medicine has been under-explored. Therefore, this review aims to highlight the vast potential that epigenetics holds. Areas covered We first review the cell-specific nature of epigenetic states and how these can vary with developmental stage and in response to environmental factors. We then summarize epigenetic biomarkers of disease, with a focus on diagnostic tests, followed by a detailed description of current and pipeline drugs with epigenetic modes of action. Finally, we discuss epigenetic biomarkers of drug response. Expert commentary Epigenetic variation can yield information on cellular states and developmental histories in ways that genotype information cannot. Furthermore, in contrast to fixed genome sequence, epigenetic patterns are plastic, so correcting aberrant, disease-causing epigenetic marks holds considerable therapeutic promise. While just six epigenetic drugs are currently approved for use in the United States, a larger number is being developed. However, a drawback to current therapeutics is their non-specific effects. Development of locus-specific epigenetic modifiers, used in conjunction with epigenetic biomarkers of response, will enable truly precision interventions.
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Affiliation(s)
- Mohamad M Kronfol
- Department of Pharmacotherapy and Outcomes Science, Virginia Commonwealth University School of Pharmacy, Richmond, Virginia, USA
| | - Mikhail G Dozmorov
- Department of Biostatistics, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA
| | - Rong Huang
- Department of Medicinal Chemistry, Virginia Commonwealth University School of Pharmacy, Richmond, Virginia, USA
| | - Patricia W Slattum
- Department of Pharmacotherapy and Outcomes Science, Virginia Commonwealth University School of Pharmacy, Richmond, Virginia, USA
| | - Joseph L McClay
- Department of Pharmacotherapy and Outcomes Science, Virginia Commonwealth University School of Pharmacy, Richmond, Virginia, USA
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Polycomb complexes PRC1 and their function in hematopoiesis. Exp Hematol 2017; 48:12-31. [PMID: 28087428 DOI: 10.1016/j.exphem.2016.12.006] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 12/19/2016] [Accepted: 12/20/2016] [Indexed: 12/31/2022]
Abstract
Hematopoiesis, the process by which blood cells are continuously produced, is one of the best studied differentiation pathways. Hematological diseases are associated with reiterated mutations in genes encoding important gene expression regulators, including chromatin regulators. Among them, the Polycomb group (PcG) of proteins is an essential system of gene silencing involved in the maintenance of cell identities during differentiation. PcG proteins assemble into two major types of Polycomb repressive complexes (PRCs) endowed with distinct histone-tail-modifying activities. PRC1 complexes are histone H2A E3 ubiquitin ligases and PRC2 trimethylates histone H3. Established conceptions about their activities, mostly derived from work in embryonic stem cells, are being modified by new findings in differentiated cells. Here, we focus on PRC1 complexes, reviewing recent evidence on their intricate architecture, the diverse mechanisms of their recruitment to targets, and the different ways in which they engage in transcriptional control. We also discuss hematopoietic PRC1 gain- and loss-of-function mouse strains, including those that model leukemic and lymphoma diseases, in the belief that these genetic analyses provide the ultimate test for molecular mechanisms driving normal hematopoiesis and hematological malignancies.
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69
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Connelly KE, Dykhuizen EC. Compositional and functional diversity of canonical PRC1 complexes in mammals. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2016; 1860:233-245. [PMID: 28007606 DOI: 10.1016/j.bbagrm.2016.12.006] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Revised: 12/12/2016] [Accepted: 12/15/2016] [Indexed: 12/17/2022]
Abstract
The compositional complexity of Polycomb Repressive Complex 1 (PRC1) increased dramatically during vertebrate evolution. What is considered the "canonical" PRC1 complex consists of four subunits originally identified as regulators of body segmentation in Drosophila. In mammals, each of these four canonical subunits consists of two to six paralogs that associate in a combinatorial manner to produce over a hundred possible distinct PRC1 complexes with unknown function. Genetic studies have begun to define the phenotypic roles for different PRC1 paralogs; however, relating these phenotypes to unique biochemical and transcriptional function for the different paralogs has been challenging. In this review, we attempt to address how the compositional diversity of canonical PRC1 complexes relates to unique roles for individual PRC1 paralogs in transcriptional regulation. This review focuses primarily on PRC1 complex composition, genome targeting, and biochemical function.
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Affiliation(s)
- Katelyn E Connelly
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University, 201 S. University St., West Lafayette, IN 47907, USA
| | - Emily C Dykhuizen
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University, 201 S. University St., West Lafayette, IN 47907, USA; Purdue University Center for Cancer Research, 201 S. University St., West Lafayette, IN 47907, USA.
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70
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Festuccia N, Gonzalez I, Navarro P. The Epigenetic Paradox of Pluripotent ES Cells. J Mol Biol 2016; 429:1476-1503. [PMID: 27988225 DOI: 10.1016/j.jmb.2016.12.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Revised: 12/02/2016] [Accepted: 12/05/2016] [Indexed: 12/15/2022]
Abstract
The propagation and maintenance of gene expression programs are at the foundation of the preservation of cell identity. A large and complex set of epigenetic mechanisms enables the long-term stability and inheritance of transcription states. A key property of authentic epigenetic regulation is being independent from the instructive signals used for its establishment. This makes epigenetic regulation, particularly epigenetic silencing, extremely robust and powerful to lock regulatory states and stabilise cell identity. In line with this, the establishment of epigenetic silencing during development restricts cell potency and maintains the cell fate choices made by transcription factors (TFs). However, how more immature cells that have not yet established their definitive fate maintain their transitory identity without compromising their responsiveness to signalling cues remains unclear. A paradigmatic example is provided by pluripotent embryonic stem (ES) cells derived from a transient population of cells of the blastocyst. Here, we argue that ES cells represent an interesting "epigenetic paradox": even though they are captured in a self-renewing state characterised by extremely efficient maintenance of their identity, which is a typical manifestation of robust epigenetic regulation, they seem not to heavily rely on classical epigenetic mechanisms. Indeed, self-renewal strictly depends on the TFs that previously instructed their undifferentiated identity and relies on a particular signalling-dependent chromatin state where repressive chromatin marks play minor roles. Although this "epigenetic paradox" may underlie their exquisite responsiveness to developmental cues, it suggests that alternative mechanisms to faithfully propagate gene regulatory states might be prevalent in ES cells.
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Affiliation(s)
- Nicola Festuccia
- Epigenetics of Stem Cells, Department of Stem Cell and Developmental Biology, Institut Pasteur, CNRS UMR3738, 25 rue du Docteur Roux, 75015 Paris, France
| | - Inma Gonzalez
- Epigenetics of Stem Cells, Department of Stem Cell and Developmental Biology, Institut Pasteur, CNRS UMR3738, 25 rue du Docteur Roux, 75015 Paris, France
| | - Pablo Navarro
- Epigenetics of Stem Cells, Department of Stem Cell and Developmental Biology, Institut Pasteur, CNRS UMR3738, 25 rue du Docteur Roux, 75015 Paris, France.
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71
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H3K27 methylation: a promiscuous repressive chromatin mark. Curr Opin Genet Dev 2016; 43:31-37. [PMID: 27940208 DOI: 10.1016/j.gde.2016.11.001] [Citation(s) in RCA: 167] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 10/21/2016] [Accepted: 11/04/2016] [Indexed: 12/24/2022]
Abstract
Polycomb Repressive Complex 2 (PRC2) is a multiprotein complex that catalyzes the methylation of lysine 27 on histone H3 (H3K27me). This histone modification is a feature of facultative heterochromatin in many eukaryotes and maintains transcriptional repression established during early development. Understanding how PRC2 targets regions of the genome to be methylated remains poorly understood. Different cell types can show disparate patterns of H3K27me, and chromatin perturbations, such as loss of marks of constitutive heterochromatin, can cause redistribution of H3K27me, implying that DNA sequence, per se, is not sufficient to define the distribution of this mark. Emerging information supports the idea that the chromatin context-including histone modifications, DNA methylation, transcription, chromatin structure and organization within the nucleus-informs PRC2 target selection.
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72
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Mas G, Di Croce L. The role of Polycomb in stem cell genome architecture. Curr Opin Cell Biol 2016; 43:87-95. [PMID: 27690123 DOI: 10.1016/j.ceb.2016.09.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Revised: 09/02/2016] [Accepted: 09/12/2016] [Indexed: 02/06/2023]
Abstract
Polycomb-group proteins maintain embryonic stem cell identity by repressing genes that encode for developmental regulatory factors. Failure to properly control developmental transcription programs by Polycomb proteins is linked to disease and embryonic lethality. Recent technological advances have revealed that developmentally repressed genes tend to cluster in the three-dimensional space of the nucleus. Importantly, spatial clustering of developmental genes is fundamental for the correct regulation of gene expression during early development. Here, we outline novel insights and perspectives regarding the function of Polycomb complexes in shaping the stem cell genome architecture, and discuss how this function might be required to properly orchestrate transcriptional programs during differentiation.
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Affiliation(s)
- Gloria Mas
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Dr. Aiguader 88, Barcelona 08003, Spain; Universitat Pompeu Fabra (UPF), Barcelona, Spain.
| | - Luciano Di Croce
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Dr. Aiguader 88, Barcelona 08003, Spain; Universitat Pompeu Fabra (UPF), Barcelona, Spain; ICREA, Pg. Lluis Companys 23, 08010 Barcelona, Spain.
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73
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Wong SJ, Gearhart MD, Taylor AB, Nanyes DR, Ha DJ, Robinson AK, Artigas JA, Lee OJ, Demeler B, Hart PJ, Bardwell VJ, Kim CA. KDM2B Recruitment of the Polycomb Group Complex, PRC1.1, Requires Cooperation between PCGF1 and BCORL1. Structure 2016; 24:1795-1801. [PMID: 27568929 DOI: 10.1016/j.str.2016.07.011] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Revised: 07/05/2016] [Accepted: 07/07/2016] [Indexed: 12/31/2022]
Abstract
KDM2B recruits H2A-ubiquitinating activity of a non-canonical Polycomb Repression Complex 1 (PRC1.1) to CpG islands, facilitating gene repression. We investigated the molecular basis of recruitment using in vitro assembly assays to identify minimal components, subcomplexes, and domains required for recruitment. A minimal four-component PRC1.1 complex can be assembled by combining two separately isolated subcomplexes: the DNA-binding KDM2B/SKP1 heterodimer and the heterodimer of BCORL1 and PCGF1, a core component of PRC1.1. The crystal structure of the KDM2B/SKP1/BCORL1/PCGF1 complex illustrates the crucial role played by the PCGF1/BCORL1 heterodimer. The BCORL1 PUFD domain positions residues preceding the RAWUL domain of PCGF1 to create an extended interface for interaction with KDM2B, which is unique to the PCGF1-containing PRC1.1 complex. The structure also suggests how KDM2B might simultaneously function in PRC1.1 and an SCF ubiquitin ligase complex and the possible molecular consequences of BCOR PUFD internal tandem duplications found in pediatric kidney and brain tumors.
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Affiliation(s)
- Sarah J Wong
- Department of Biochemistry and CTRC, University of Texas Health Science Center at San Antonio, MSC 7760, 7703 Floyd Curl Drive, San Antonio, TX 78229-3990, USA
| | - Micah D Gearhart
- Department of Genetics, Cell Biology and Development, Masonic Cancer Center and Developmental Biology Center, University of Minnesota, Minneapolis, MN 55455, USA
| | - Alexander B Taylor
- Department of Biochemistry and CTRC, University of Texas Health Science Center at San Antonio, MSC 7760, 7703 Floyd Curl Drive, San Antonio, TX 78229-3990, USA
| | - David R Nanyes
- Department of Biochemistry and CTRC, University of Texas Health Science Center at San Antonio, MSC 7760, 7703 Floyd Curl Drive, San Antonio, TX 78229-3990, USA
| | - Daniel J Ha
- Department of Biochemistry and CTRC, University of Texas Health Science Center at San Antonio, MSC 7760, 7703 Floyd Curl Drive, San Antonio, TX 78229-3990, USA
| | - Angela K Robinson
- Department of Biochemistry and CTRC, University of Texas Health Science Center at San Antonio, MSC 7760, 7703 Floyd Curl Drive, San Antonio, TX 78229-3990, USA
| | - Jason A Artigas
- Department of Biochemistry, Midwestern University, 19555 North 59(th) Avenue, Glendale, AZ 85308, USA
| | - Oliver J Lee
- Department of Biochemistry, Midwestern University, 19555 North 59(th) Avenue, Glendale, AZ 85308, USA
| | - Borries Demeler
- Department of Biochemistry and CTRC, University of Texas Health Science Center at San Antonio, MSC 7760, 7703 Floyd Curl Drive, San Antonio, TX 78229-3990, USA
| | - P John Hart
- Department of Biochemistry and CTRC, University of Texas Health Science Center at San Antonio, MSC 7760, 7703 Floyd Curl Drive, San Antonio, TX 78229-3990, USA; Department of Veterans Affairs, Geriatric Research, Education, and Clinical Center, South Texas Veterans Health Care System, San Antonio TX 78229, USA
| | - Vivian J Bardwell
- Department of Genetics, Cell Biology and Development, Masonic Cancer Center and Developmental Biology Center, University of Minnesota, Minneapolis, MN 55455, USA
| | - Chongwoo A Kim
- Department of Biochemistry, Midwestern University, 19555 North 59(th) Avenue, Glendale, AZ 85308, USA.
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