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Hyperacetylated chromatin domains mark cell type-specific genes and suggest distinct modes of enhancer function. Nat Commun 2020; 11:4544. [PMID: 32917861 PMCID: PMC7486385 DOI: 10.1038/s41467-020-18303-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Accepted: 07/08/2020] [Indexed: 01/24/2023] Open
Abstract
Stratification of enhancers by signal strength in ChIP-seq assays has resulted in the establishment of super-enhancers as a widespread and useful tool for identifying cell type-specific, highly expressed genes and associated pathways. We examine a distinct method of stratification that focuses on peak breadth, termed hyperacetylated chromatin domains (HCDs), which classifies broad regions exhibiting histone modifications associated with gene activation. We find that this analysis serves to identify genes that are both more highly expressed and more closely aligned to cell identity than super-enhancer analysis does using multiple data sets. Moreover, genetic manipulations of selected gene loci suggest that some enhancers located within HCDs work at least in part via a distinct mechanism involving the modulation of histone modifications across domains and that this activity can be imported into a heterologous gene locus. In addition, such genetic dissection reveals that the super-enhancer concept can obscure important functions of constituent elements. Super-enhancer are usually defined by high levels of chromatin modification and associate with cell-specific gene expression. Here, the authors define hyperacetylated chromatin domains (HCDs) by using histone hyperacetylation peak breadth information and show that HCDs associated more closely with cell identity than super-enhancers.
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Identification of a Novel Enhancer/Chromatin Opening Element Associated with High-Level γ-Globin Gene Expression. Mol Cell Biol 2018; 38:MCB.00197-18. [PMID: 30012865 PMCID: PMC6146835 DOI: 10.1128/mcb.00197-18] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Accepted: 07/10/2018] [Indexed: 01/05/2023] Open
Abstract
The organization of the five β-type globin genes on chromosome 11 reflects the timing of expression during erythroid cell development, with the embryonic ε-globin gene being located at the 5′ end, followed by the two fetal γ-globin genes, and with the adult β- and δ-globin genes being located at the 3′ end. Here, we functionally characterized a DNase I-hypersensitive site (HS) located 4 kb upstream of the Gγ-globin gene (HBG-4kb HS). The organization of the five β-type globin genes on chromosome 11 reflects the timing of expression during erythroid cell development, with the embryonic ε-globin gene being located at the 5′ end, followed by the two fetal γ-globin genes, and with the adult β- and δ-globin genes being located at the 3′ end. Here, we functionally characterized a DNase I-hypersensitive site (HS) located 4 kb upstream of the Gγ-globin gene (HBG-4kb HS). This site is occupied by transcription factors USF1, USF2, EGR1, MafK, and NF-E2 in the human erythroleukemia cell line K562 and exhibits histone modifications typical for enhancers. We generated a synthetic zinc finger (ZF) DNA-binding domain targeting the HBG-4kb HS (HBG-4kb ZF). The HBG-4kb ZF interacted with the target site in vitro and in the context of cells with a high affinity and specificity. Direct delivery of the HBG-4kb ZF to K562 and primary human erythroid cells caused a reduction in γ-globin gene expression which was associated with decreased binding of transcription factors and active histone marks at and downstream of the HS. The data demonstrate that the HBG-4kb HS is important for fetal globin production and suggest that it may act by opening chromatin in a directional manner.
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Lee WS, McColl B, Maksimovic J, Vadolas J. Epigenetic interplay at the β-globin locus. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2017; 1860:393-404. [DOI: 10.1016/j.bbagrm.2017.01.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Revised: 01/28/2017] [Accepted: 01/30/2017] [Indexed: 02/02/2023]
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Abstract
Although it was originally believed that enhancers activate only the nearest promoter, recent global analyses enabled by high-throughput technology suggest that the network of enhancer-promoter interactions is far more complex. The mechanisms that determine the specificity of enhancer-promoter interactions are still poorly understood, but they are thought to include biochemical compatibility, constraints imposed by the three-dimensional architecture of chromosomes, insulator elements, and possibly the effects of local chromatin composition. In this review, we assess the current insights into these determinants, and highlight the functional genomic approaches that will lead the way towards better mechanistic understanding.
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van Arensbergen J, van Steensel B, Bussemaker HJ. In search of the determinants of enhancer-promoter interaction specificity. Trends Cell Biol 2014; 24:695-702. [PMID: 25160912 DOI: 10.1016/j.tcb.2014.07.004] [Citation(s) in RCA: 120] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Revised: 07/15/2014] [Accepted: 07/21/2014] [Indexed: 02/07/2023]
Abstract
Although it was originally believed that enhancers activate only the nearest promoter, recent global analyses enabled by high-throughput technology suggest that the network of enhancer-promoter interactions is far more complex. The mechanisms that determine the specificity of enhancer-promoter interactions are still poorly understood, but they are thought to include biochemical compatibility, constraints imposed by the three-dimensional architecture of chromosomes, insulator elements, and possibly the effects of local chromatin composition. In this review, we assess the current insights into these determinants, and highlight the functional genomic approaches that will lead the way towards better mechanistic understanding.
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Affiliation(s)
- Joris van Arensbergen
- Division of Gene Regulation, Netherlands Cancer Institute, 1066 CX Amsterdam, The Netherlands
| | - Bas van Steensel
- Division of Gene Regulation, Netherlands Cancer Institute, 1066 CX Amsterdam, The Netherlands.
| | - Harmen J Bussemaker
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA; Center for Computational Biology and Bioinformatics, Columbia University, New York, NY 10032, USA.
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Abstract
Enhancer elements regulate the tissue- and developmental-stage-specific expression of genes. Recent estimates suggest that there are more than 50,000 enhancers in mammalian cells. At least a subset of enhancers has been shown to recruit RNA polymerase II transcription complexes and to generate enhancer transcripts. Here, we provide an overview of enhancer function and discuss how transcription of enhancers or enhancer-generated transcripts could contribute to the regulation of gene expression during development and differentiation.
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Cadiz-Rivera B, Fromm G, de Vries C, Fields J, McGrath KE, Fiering S, Bulger M. The chromatin "landscape" of a murine adult β-globin gene is unaffected by deletion of either the gene promoter or a downstream enhancer. PLoS One 2014; 9:e92947. [PMID: 24817273 PMCID: PMC4015891 DOI: 10.1371/journal.pone.0092947] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Accepted: 02/27/2014] [Indexed: 01/11/2023] Open
Abstract
In mammals, the complex tissue- and developmental-specific expression of genes within the β-globin cluster is known to be subject to control by the gene promoters, by a locus control region (LCR) located upstream of the cluster, and by sequence elements located across the intergenic regions. Despite extensive investigation, however, the complement of sequences that is required for normal regulation of chromatin structure and gene expression within the cluster is not fully defined. To further elucidate regulation of the adult β-globin genes, we investigate the effects of two deletions engineered within the endogenous murine β-globin locus. First, we find that deletion of the β2-globin gene promoter, while eliminating β2-globin gene expression, results in no additional effects on chromatin structure or gene expression within the cluster. Notably, our observations are not consistent with competition among the β-globin genes for LCR activity. Second, we characterize a novel enhancer located 3′ of the β2-globin gene, but find that deletion of this sequence has no effect whatsoever on gene expression or chromatin structure. This observation highlights the difficulty in assigning function to enhancer sequences identified by the chromatin “landscape” or even by functional assays.
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Affiliation(s)
- Brenda Cadiz-Rivera
- Department of Pediatrics, University of Rochester Medical Center and Center for Pediatric Biomedical Research, Rochester, New York, United States of America
| | - George Fromm
- Department of Pediatrics, University of Rochester Medical Center and Center for Pediatric Biomedical Research, Rochester, New York, United States of America
- National Institute for Environmental Health Sciences, NIH, Research Triangle Park, North Carolina, United States of America
| | - Christina de Vries
- Department of Pediatrics, University of Rochester Medical Center and Center for Pediatric Biomedical Research, Rochester, New York, United States of America
| | - Jennifer Fields
- Department of Microbiology and Immunology, Dartmouth Medical School, Hanover, New Hampshire, United States of America
| | - Kathleen E. McGrath
- Department of Pediatrics, University of Rochester Medical Center and Center for Pediatric Biomedical Research, Rochester, New York, United States of America
| | - Steven Fiering
- Department of Microbiology and Immunology, Dartmouth Medical School, Hanover, New Hampshire, United States of America
| | - Michael Bulger
- Department of Pediatrics, University of Rochester Medical Center and Center for Pediatric Biomedical Research, Rochester, New York, United States of America
- * E-mail:
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Fraser ST. The modern primitives: applying new technological approaches to explore the biology of the earliest red blood cells. ISRN HEMATOLOGY 2013; 2013:568928. [PMID: 24222861 PMCID: PMC3814094 DOI: 10.1155/2013/568928] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Accepted: 08/25/2013] [Indexed: 01/01/2023]
Abstract
One of the most critical stages in mammalian embryogenesis is the independent production of the embryo's own circulating, functional red blood cells. Correspondingly, erythrocytes are the first cell type to become functionally mature during embryogenesis. Failure to achieve this invariably leads to in utero lethality. The recent application of technologies such as transcriptome analysis, flow cytometry, mutant embryo analysis, and transgenic fluorescent gene expression reporter systems has shed new light on the distinct erythroid lineages that arise early in development. Here, I will describe the similarities and differences between the distinct erythroid populations that must form for the embryo to survive. While much of the focus of this review will be the poorly understood primitive erythroid lineage, a discussion of other erythroid and hematopoietic lineages, as well as the cell types making up the different niches that give rise to these lineages, is essential for presenting an appropriate developmental context of these cells.
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Affiliation(s)
- Stuart T. Fraser
- Disciplines of Physiology, Anatomy and Histology, Bosch Institute, School of Medical Sciences, University of Sydney, Medical Foundation Building K25, 92-94 Parramatta Road, Camperdown, NSW 2050, Australia
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Harth-Hertle ML, Scholz BA, Erhard F, Glaser LV, Dölken L, Zimmer R, Kempkes B. Inactivation of intergenic enhancers by EBNA3A initiates and maintains polycomb signatures across a chromatin domain encoding CXCL10 and CXCL9. PLoS Pathog 2013; 9:e1003638. [PMID: 24068939 PMCID: PMC3777872 DOI: 10.1371/journal.ppat.1003638] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Accepted: 08/03/2013] [Indexed: 01/28/2023] Open
Abstract
Epstein-Barr virus (EBV) causes a persistent infection in human B cells by establishing specific transcription programs to control B cell activation and differentiation. Transcriptional reprogramming of EBV infected B cells is predominantly driven by the action of EBV nuclear antigens, among them the transcriptional repressor EBNA3A. By comparing gene expression profiles of wt and EBNA3A negative EBV infected B cells, we have previously identified a broad array of cellular genes controlled by EBNA3A. We now find that genes repressed by EBNA3A in these cells are significantly enriched for the repressive histone mark H3K27me3, which is installed by Polycomb group (PcG) proteins. This PcG-controlled subset of genes also carries H3K27me3 marks in a variety of other tissues, suggesting that the commitment to PcG silencing is an intrinsic feature of these gene loci that can be used by EBNA3A. In addition, EBNA3A targets frequently reside in co-regulated gene clusters. To study the mechanism of gene repression by EBNA3A and to evaluate the relative contribution of PcG proteins during this process, we have selected the genomic neighbors CXCL10 and CXCL9 as a model for co-repressed and PcG-controlled genes. We show that EBNA3A binds to CBF1 occupied intergenic enhancers located between CXCL10 and CXCL9 and displaces the transactivator EBNA2. This impairs enhancer activity, resulting in a rapid transcriptional shut-down of both genes in a CBF1-dependent manner and initiation of a delayed gain of H3K27me3 marks covering an extended chromatin domain. H3K27me3 marks increase gradually and are maintained by EBNA3A. Our study provides direct evidence that repression by EBNA3A requires CBF1 and that EBNA3A and EBNA2 compete for access to CBF1 at identical genomic sites. Most importantly, our results demonstrate that transcriptional silencing by EBNA3A precedes the appearance of repressive PcG marks and indicate that both events are triggered by loss of enhancer activity. Epstein-Barr virus (EBV) is a γ-herpesvirus which establishes a latent infection in human B cells and is associated with the pathogenesis of several types of cancer. Here, we report that cellular genes repressed by the EBV nuclear antigen 3A (EBNA3A) in EBV infected B cells frequently form contiguous clusters in the human genome and are committed to epigenetic silencing by Polycomb group (PcG) proteins. The chemokine genes CXCL10 and CXCL9 and their receptors on NK and T cells are critical weapons of the infected host to control herpesvirus infections. CXCL10 and CXCL9 are close neighbors within an extended PcG-controlled domain. We show that EBNA3A binds to intergenic enhancers located between CXCL10 and CXCL9 and displaces the transactivator EBNA2. This process impairs enhancer activity, resulting in a rapid transcriptional shut-down of both genes followed by a delayed gain of PcG histone marks. These PcG marks increase within the following weeks and are maintained by EBNA3A. Our results show that rapid transcriptional shut-down of distal genes and domain-wide PcG silencing is triggered by loss of enhancer activity and suggest that EBNA3A can reprogram the cellular genome in order to escape the immune surveillance of the host.
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Affiliation(s)
- Marie L. Harth-Hertle
- Department of Gene Vectors, Helmholtz Center Munich, German Research Center for Environmental Health, Munich, Germany
| | - Barbara A. Scholz
- Department of Gene Vectors, Helmholtz Center Munich, German Research Center for Environmental Health, Munich, Germany
| | - Florian Erhard
- Institut für Informatik, Ludwig-Maximilians-Universität München, München, Germany
| | - Laura V. Glaser
- Department of Gene Vectors, Helmholtz Center Munich, German Research Center for Environmental Health, Munich, Germany
| | - Lars Dölken
- Department of Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Ralf Zimmer
- Institut für Informatik, Ludwig-Maximilians-Universität München, München, Germany
| | - Bettina Kempkes
- Department of Gene Vectors, Helmholtz Center Munich, German Research Center for Environmental Health, Munich, Germany
- * E-mail:
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