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Dehingia B, Milewska M, Janowski M, Pękowska A. CTCF
shapes chromatin structure and gene expression in health and disease. EMBO Rep 2022; 23:e55146. [PMID: 35993175 PMCID: PMC9442299 DOI: 10.15252/embr.202255146] [Citation(s) in RCA: 34] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 05/31/2022] [Accepted: 07/14/2022] [Indexed: 11/09/2022] Open
Affiliation(s)
- Bondita Dehingia
- Dioscuri Centre for Chromatin Biology and Epigenomics, Nencki Institute of Experimental Biology Polish Academy of Sciences Warsaw Poland
| | - Małgorzata Milewska
- Dioscuri Centre for Chromatin Biology and Epigenomics, Nencki Institute of Experimental Biology Polish Academy of Sciences Warsaw Poland
| | - Marcin Janowski
- Dioscuri Centre for Chromatin Biology and Epigenomics, Nencki Institute of Experimental Biology Polish Academy of Sciences Warsaw Poland
| | - Aleksandra Pękowska
- Dioscuri Centre for Chromatin Biology and Epigenomics, Nencki Institute of Experimental Biology Polish Academy of Sciences Warsaw Poland
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Jafari H, Hussain S, Campbell MJ. Nuclear Receptor Coregulators in Hormone-Dependent Cancers. Cancers (Basel) 2022; 14:2402. [PMID: 35626007 PMCID: PMC9139824 DOI: 10.3390/cancers14102402] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Accepted: 05/09/2022] [Indexed: 12/10/2022] Open
Abstract
Nuclear receptors (NRs) function collectively as a transcriptional signaling network that mediates gene regulatory actions to either maintain cellular homeostasis in response to hormonal, dietary and other environmental factors, or act as orphan receptors with no known ligand. NR complexes are large and interact with multiple protein partners, collectively termed coregulators. Coregulators are essential for regulating NR activity and can dictate whether a target gene is activated or repressed by a variety of mechanisms including the regulation of chromatin accessibility. Altered expression of coregulators contributes to a variety of hormone-dependent cancers including breast and prostate cancers. Therefore, understanding the mechanisms by which coregulators interact with and modulate the activity of NRs provides opportunities to develop better prognostic and diagnostic approaches, as well as novel therapeutic targets. This review aims to gather and summarize recent studies, techniques and bioinformatics methods used to identify distorted NR coregulator interactions that contribute as cancer drivers in hormone-dependent cancers.
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Affiliation(s)
- Hedieh Jafari
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210, USA;
- Department of Pharmaceutics and Pharmaceutical Chemistry, College of Pharmacy, The Ohio State University, Columbus, OH 43210, USA;
| | - Shahid Hussain
- Department of Pharmaceutics and Pharmaceutical Chemistry, College of Pharmacy, The Ohio State University, Columbus, OH 43210, USA;
| | - Moray J. Campbell
- Department of Pharmaceutics and Pharmaceutical Chemistry, College of Pharmacy, The Ohio State University, Columbus, OH 43210, USA;
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Mackeh R, Marr AK, Fadda A, Kino T. C2H2-Type Zinc Finger Proteins: Evolutionarily Old and New Partners of the Nuclear Hormone Receptors. NUCLEAR RECEPTOR SIGNALING 2018; 15:1550762918801071. [PMID: 30718982 PMCID: PMC6348741 DOI: 10.1177/1550762918801071] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 02/02/2017] [Indexed: 12/21/2022]
Abstract
Nuclear hormone receptors (NRs) are evolutionarily conserved ligand-dependent
transcription factors. They are essential for human life, mediating the actions
of lipophilic molecules, such as steroid hormones and metabolites of fatty acid,
cholesterol, and external toxic compounds. The C2H2-type zinc finger proteins
(ZNFs) form the largest family of the transcription factors in humans and are
characterized by multiple, tandemly arranged zinc fingers. Many of the C2H2-type
ZNFs are conserved throughout evolution, suggesting their involvement in
preserved biological activities, such as general transcriptional regulation and
development/differentiation of organs/tissues observed in the early embryonic
phase. However, some C2H2-type ZNFs, such as those with the Krüppel-associated
box (KRAB) domain, appeared relatively late in evolution and have significantly
increased family members in mammals including humans, possibly modulating their
complicated transcriptional network and/or supporting the morphological
development/functions specific to them. Such evolutional characteristics of the
C2H2-type ZNFs indicate that these molecules influence the NR functions
conserved through evolution, whereas some also adjust them to meet with specific
needs of higher organisms. We review the interaction between NRs and C2H2-type
ZNFs by focusing on some of the latter molecules.
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Guo J, Li N, Han J, Pei F, Wang T, Lu D, Jiang J. DNA recognition patterns of the multi-zinc-finger protein CTCF: a mutagenesis study. Acta Pharm Sin B 2018; 8:900-908. [PMID: 30505659 PMCID: PMC6251859 DOI: 10.1016/j.apsb.2018.08.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 06/04/2018] [Accepted: 06/28/2018] [Indexed: 12/17/2022] Open
Abstract
CCCTC-binding factor (CTCF) is a zinc-finger protein, serving an important part in the genome architecture as well as some biochemical processes. Over 70,000 CTCF binding DNA sites have been detected genome-wide, and most anchors of chromatin loops are demarcated with the CTCF binding. Various protein or RNA molecules interact with DNA-bound CTCF to conduct different biological functions, and potentially the interfaces between CTCF and its cofactors can be targets for drug development. Here we identify the effective region of CTCF in DNA recognition, which defines the exposed CTCF surface feature for the interaction of cofactors. While the zinc-finger region contributes the most in DNA association, its binding affinity varies based on different DNA sequences. To investigate the effectiveness of individual zinc-fingers, the key residues are mutated to inactivate the DNA binding ability, while the finger configuration and the spacing between fingers are preserved. The strategy is proved to be successful, while clear differences are observed in the DNA binding affinities among the 11 finger mutants and the result is consistent to previous studies in general. With the help of inactivated finger mutants, we identify the ineffective fingers and the dominant effective fingers, which form distinctive patterns on different DNA targets.
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Song SH, Kim TY. CTCF, Cohesin, and Chromatin in Human Cancer. Genomics Inform 2017; 15:114-122. [PMID: 29307136 PMCID: PMC5769866 DOI: 10.5808/gi.2017.15.4.114] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Accepted: 11/29/2017] [Indexed: 12/20/2022] Open
Abstract
It is becoming increasingly clear that eukaryotic genomes are subjected to higher-order chromatin organization by the CCCTC-binding factor/cohesin complex. Their dynamic interactions in three dimensions within the nucleus regulate gene transcription by changing the chromatin architecture. Such spatial genomic organization is functionally important for the spatial disposition of chromosomes to control cell fate during development and differentiation. Thus, the dysregulation of proper long-range chromatin interactions may influence the development of tumorigenesis and cancer progression.
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Affiliation(s)
- Sang-Hyun Song
- Cancer Genomics Research Laboratory, Cancer Research Institute, Seoul National University, Seoul 03080, Korea
| | - Tae-You Kim
- Cancer Genomics Research Laboratory, Cancer Research Institute, Seoul National University, Seoul 03080, Korea.,Department of Molecular Medicine and Biopharmaceutical Sciences, Graduate School of Convergence Science and Technology, Seoul National University, Seoul 03080, Korea.,Department of Internal Medicine, Seoul National University Hospital, Seoul 03080, Korea
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Norton HK, Phillips-Cremins JE. Crossed wires: 3D genome misfolding in human disease. J Cell Biol 2017; 216:3441-3452. [PMID: 28855250 PMCID: PMC5674879 DOI: 10.1083/jcb.201611001] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 06/09/2017] [Accepted: 08/16/2017] [Indexed: 12/13/2022] Open
Abstract
Norton and Phillips-Cremins review the 3D architecture of the genome and discuss links between chromatin misfolding and human diseases. Mammalian genomes are folded into unique topological structures that undergo precise spatiotemporal restructuring during healthy development. Here, we highlight recent advances in our understanding of how the genome folds inside the 3D nucleus and how these folding patterns are miswired during the onset and progression of mammalian disease states. We discuss potential mechanisms underlying the link among genome misfolding, genome dysregulation, and aberrant cellular phenotypes. We also discuss cases in which the endogenous 3D genome configurations in healthy cells might be particularly susceptible to mutation or translocation. Together, these data support an emerging model in which genome folding and misfolding is critically linked to the onset and progression of a broad range of human diseases.
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Affiliation(s)
- Heidi K Norton
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA
| | - Jennifer E Phillips-Cremins
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA .,Epigenetics Program, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA
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Zia A, Bhatti A, John P, Kiani AK. Data interpretation: deciphering the biological function of Type 2 diabetes associated risk loci. Acta Diabetol 2015; 52:789-800. [PMID: 25585593 DOI: 10.1007/s00592-014-0700-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Accepted: 12/09/2014] [Indexed: 10/24/2022]
Abstract
AIMS Type 2 diabetes (T2D) is a complex multifactorial disorder with more than 40 loci associated with disease susceptibility. Most of these genome-wide significant loci reside in noncoding regions, it is important to decipher the potential regulatory function of these variants and to differentiate between true and tag signals. Nowadays, databases are being developed to study and predict the function of these associated variants, and RegulomeDB is one such database. METHODS We used RegulomeDB to analyze the potential function of the associated variants reported in five genome-wide association studies (GWAS) of T2D. RESULTS We investigated the 1,567 single nucleotide polymorphisms (SNPs) with 989 SNPs with a score of 1-6. Of those 989 SNPs, only 64 returned with RegulomeDB score <3 (evidence of regulatory function), and only four of these were GWAS significant SNPs (THADA/rs10203174, score = 1b; UBE2E2/rs7612463, score = 2a; ARAP1/rs1552224 and TP53INP1/rs8996852, score = 2b). But only 63 % of the annotated SNPs showed regulatory function that is an important limitation of the RegulomeDB as this database only provides information of few regulatory elements. CONCLUSION This study further supports that some of the noncoding GWAS variants are the true associations and not the tag ones. This study also proves the utility and importance of the RegulomeDB and other such databases. Although it is an extensive database of regulatory elements but has certain limitation due to utilization of only few types of regulatory elements and pathways.
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Affiliation(s)
- Asima Zia
- Healthcare Biotechnology, Atta-ur-Rahman School of Applied Biosciences (ASAB), National University of Sciences and Technology (NUST), Sector H-12, Islamabad, Pakistan
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CCCTC-binding factor recruitment to the early region of the human papillomavirus 18 genome regulates viral oncogene expression. J Virol 2015; 89:4770-85. [PMID: 25694598 PMCID: PMC4403478 DOI: 10.1128/jvi.00097-15] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 02/12/2015] [Indexed: 01/08/2023] Open
Abstract
UNLABELLED Host cell differentiation-dependent regulation of human papillomavirus (HPV) gene expression is required for productive infection. The host cell CCCTC-binding factor (CTCF) functions in genome-wide chromatin organization and gene regulation. We have identified a conserved CTCF binding site in the E2 open reading frame of high-risk HPV types. Using organotypic raft cultures of primary human keratinocytes containing high-risk HPV18 genomes, we show that CTCF recruitment to this conserved site regulates viral gene expression in differentiating epithelia. Mutation of the CTCF binding site increases the expression of the viral oncoproteins E6 and E7 and promotes host cell proliferation. Loss of CTCF binding results in a reduction of a specific alternatively spliced transcript expressed from the early gene region concomitant with an increase in the abundance of unspliced early transcripts. We conclude that high-risk HPV types have evolved to recruit CTCF to the early gene region to control the balance and complexity of splicing events that regulate viral oncoprotein expression. IMPORTANCE The establishment and maintenance of HPV infection in undifferentiated basal cells of the squamous epithelia requires the activation of a subset of viral genes, termed early genes. The differentiation of infected cells initiates the expression of the late viral transcripts, allowing completion of the virus life cycle. This tightly controlled balance of differentiation-dependent viral gene expression allows the virus to stimulate cellular proliferation to support viral genome replication with minimal activation of the host immune response, promoting virus productivity. Alternative splicing of viral mRNAs further increases the complexity of viral gene expression. In this study, we show that the essential host cell protein CTCF, which functions in genome-wide chromatin organization and gene regulation, is recruited to the HPV genome and plays an essential role in the regulation of early viral gene expression and transcript processing. These data highlight a novel virus-host interaction important for HPV pathogenicity.
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Interactive actions of Bdnf methylation and cell metabolism for building neural resilience under the influence of diet. Neurobiol Dis 2014; 73:307-18. [PMID: 25283985 DOI: 10.1016/j.nbd.2014.09.014] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Revised: 09/12/2014] [Accepted: 09/24/2014] [Indexed: 01/07/2023] Open
Abstract
Quality nutrition during the period of brain formation is a predictor of brain functional capacity and plasticity during adulthood; however it is not clear how this conferred plasticity imparts long-term neural resilience. Here we report that early exposure to dietary omega-3 fatty acids orchestrates key interactions between metabolic signals and Bdnf methylation creating a reservoir of neuroplasticity that can protect the brain against the deleterious effects of switching to a Western diet (WD). We observed that the switch to a WD increased Bdnf methylation specific to exon IV, in proportion to anxiety-like behavior, in Sprague Dawley rats reared in low omega-3 fatty acid diet, and these effects were abolished by the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine. Blocking methylation also counteracted the reducing action of WD on the transcription regulator CTCF binding to Bdnf promoter IV. In vitro studies confirmed that CTCF binding to Bdnf promoter IV is essential for the action of DHA on BDNF regulation. Diet is also intrinsically associated to cell metabolism, and here we show that the switch to WD downregulated cell metabolism (NAD/NADH ratio and SIRT1). The fact that DNA methyltransferase inhibitor did not alter these parameters suggests they occur upstream to methylation. In turn, the methylation inhibitor counteracted the action of WD on PGC-1α, a mitochondrial transcription co-activator and BDNF regulator, suggesting that PGC-1α is an effector of Bdnf methylation. Results support a model in which diet can build an "epigenetic memory" during brain formation that confers resilience to metabolic perturbations occurring in adulthood.
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Tsui S, Dai W, Lu L. CCCTC-binding factor mediates effects of glucose on beta cell survival. Cell Prolif 2013; 47:28-37. [PMID: 24354619 DOI: 10.1111/cpr.12085] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Accepted: 10/07/2013] [Indexed: 12/17/2022] Open
Abstract
OBJECTIVES Pancreatic islet β-cell survival is paramount for regulation of insulin activity and for maintaining glucose homeostasis. Recently, Pax6 has been shown to be essential for many vital functions in β-cells, although many molecular mechanisms of its homeostasis in β-cells remain unclear. The present study investigates novel effects of glucose- and insulin-induced CCCTC-binding factor (CTCF) activity on Pax6 gene expression as well as for subsequent effects of insulin-activated signalling pathways, on β-cell proliferation. MATERIALS AND METHODS Pancreatic β-TC-1-6 cells were cultured in DMEM and stimulated with high concentrations of glucose (5-125 mm); cell viability was assessed by MTT assay. Effects of CTCF on Pax6 were evaluated in the high glucose-induced environment and CTCF/Erk-suppressed cells, by promoter reporter and western blotting analyses. RESULTS Increases in glucose and insulin concentrations upregulated CTCF and consequently downregulated Pax6 in β-cell survival and proliferation. Knocking-down CTCF directly affected Pax6 transcription through CTCF binding and blocked the response to glucose. Altered Erk activity mediated effects of CTCF on controlling Pax6 expression, which partially regulated β-cell proliferation. CONCLUSIONS CTCF functioned as a molecular mediator between insulin-induced upstream Erk signalling and Pax6 expression in these pancreatic β-cells. This pathway may contribute to regulation of β-cell survival and proliferation.
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Affiliation(s)
- S Tsui
- Department of Medicine, David Geffen School of Medicine University of California Los Angeles, Torrance, CA, 90502, USA
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Tsui S, Gao J, Wang C, Lu L. CTCF mediates effect of insulin on glucagon expression. Exp Cell Res 2012; 318:887-95. [PMID: 22426149 DOI: 10.1016/j.yexcr.2012.03.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2011] [Revised: 02/29/2012] [Accepted: 03/01/2012] [Indexed: 11/15/2022]
Abstract
Pancreatic islet α-cell development and glucagon production are mainly regulated by Pax6 in the homeobox gene families. However, the molecular mechanism fine-tuning the regulation of these events in α-cell still remains unclear. In ocular cells, Pax6 transcription is regulated by CTCF through its binding to specific sites in Pax6 promoter. In this study, CTCF-mediated regulations of islet α-cell development and glucagon production were investigated in both CTCF transgenic mice and α-TC-1-6 cells. Over-expression of CTCF in transgenic mice affected development of pancreatic islets by significantly suppressing α-cell population in both embryonic and adult pancreases. The effect of CTCF on Pax6 gene expression and subsequently, on pro-glucagon production was however, examined in pancreatic islet α-cells. Over-expression and knock-down of CTCF directly affected Pax6 expression. More importantly, the CTCF binding sites upstream from Pax6 p0 promoter were required for regulating p0 promoter activity in islet α-cells. Stimulation of α-cells with insulin resulted in a significant increase in CTCF expression and a decrease in Pax6 expression, and consequently suppressed pro-glucagon expression. In contrast, these insulin-induced effects were blocked by knockdown of CTCF mRNA with specific siRNA in α-cells. Altogether, our results demonstrated for the first time that CTCF functions as a switch-like molecule between the insulin signaling and the regulations of Pax6 and glucagon expression in pancreatic islet α-cells.
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Affiliation(s)
- Shanli Tsui
- Department of Medicine, David Geffen School of Medicine University of California Los Angeles, Torrance, CA 90502, USA
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Abstract
CTCF is an evolutionary conserved and ubiquitously expressed protein that binds thousands of sites in the human genome. Ectopic expression of CTCF in various normal and tumoral human cell lines inhibits cell division and clonogenicity, with the consequence to consider CTCF a potential tumor-suppressor factor. In this review article, we focused on the molecular mechanisms engaged by CTCF to modulate the expression of several key-regulators of differentiation, cellular senescence, cell cycle control and progression, whose expression is frequently altered in tumors. Moreover, we discussed common features of CTCF at each tumor-related DNA-binding sequence, such as protein-partners, post-translational modifications, and distinctive epigenetic marks establishment. The investigation of the molecular mechanisms engaged by CTCF to modulate tumor-related genes emphasizes the cell-type dependency of its tumor suppressor role. Indeed, the ability of CTCF to bind their promoters strictly depends by cell-type features as DNA methylation, BORIS-binding and post-translational modifications as PARYlation.
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Affiliation(s)
- Francesco Paolo Fiorentino
- Sbarro Institute for Cancer Research and Molecular Medicine, Center for Biotechnology, Department of Biology, College of Science and Technology, Temple University, Philadelphia, Pennsylvania 19122, USA
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Schmidt D, Schwalie PC, Wilson MD, Ballester B, Gonçalves A, Kutter C, Brown GD, Marshall A, Flicek P, Odom DT. Waves of retrotransposon expansion remodel genome organization and CTCF binding in multiple mammalian lineages. Cell 2012; 148:335-48. [PMID: 22244452 PMCID: PMC3368268 DOI: 10.1016/j.cell.2011.11.058] [Citation(s) in RCA: 424] [Impact Index Per Article: 35.3] [Reference Citation Analysis] [Abstract] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Revised: 09/09/2011] [Accepted: 11/30/2011] [Indexed: 01/22/2023]
Abstract
CTCF-binding locations represent regulatory sequences that are highly constrained over the course of evolution. To gain insight into how these DNA elements are conserved and spread through the genome, we defined the full spectrum of CTCF-binding sites, including a 33/34-mer motif, and identified over five thousand highly conserved, robust, and tissue-independent CTCF-binding locations by comparing ChIP-seq data from six mammals. Our data indicate that activation of retroelements has produced species-specific expansions of CTCF binding in rodents, dogs, and opossum, which often functionally serve as chromatin and transcriptional insulators. We discovered fossilized repeat elements flanking deeply conserved CTCF-binding regions, indicating that similar retrotransposon expansions occurred hundreds of millions of years ago. Repeat-driven dispersal of CTCF binding is a fundamental, ancient, and still highly active mechanism of genome evolution in mammalian lineages. PaperClip
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Affiliation(s)
- Dominic Schmidt
- Cancer Research UK, Cambridge Research Institute, Li Ka Shing Centre, Robinson Way, Cambridge CB2 0RE, UK
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Ross-Innes CS, Brown GD, Carroll JS. A co-ordinated interaction between CTCF and ER in breast cancer cells. BMC Genomics 2011; 12:593. [PMID: 22142239 PMCID: PMC3248577 DOI: 10.1186/1471-2164-12-593] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2011] [Accepted: 12/05/2011] [Indexed: 11/11/2022] Open
Abstract
Background CCCTC-binding factor (CTCF) is a conserved zinc finger transcription factor that is involved in both intra- and interchromasomal looping. Recent research has shown a role for CTCF in estrogen receptor (ER) biology, at some individual loci, but a multi-context global analysis of CTCF binding and transcription activity is lacking. Results We now map CTCF binding genome wide in breast cancer cells and find that CTCF binding is unchanged in response to estrogen or tamoxifen treatment. We find a small but reproducible set of CTCF binding events that overlap with both the nuclear receptor, estrogen receptor, and the forkhead protein FOXA1. These overlapping binding events are likely functional as they are biased towards estrogen-regulated genes, compared to regions lacking either CTCF or ER binding. In addition we identify cell-line specific CTCF binding events. These binding events are more likely to be associated with cell-line specific ER binding events and are also more likely to be adjacent to genes that are expressed in that particular cell line. Conclusion The evolving role for CTCF in ER biology is complex, but is likely to be multifunctional and possibly influenced by the specific genomic locus. Our data suggest a positive, pro-transcriptional role for CTCF in ER-mediated gene expression in breast cancer cells. CTCF not only provides boundaries for accessible and 'protected' transcriptional blocks, but may also influence the actual binding of ER to the chromatin, thereby modulating the estrogen-mediated gene expression changes observed in breast cancer cells.
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Affiliation(s)
- Caryn S Ross-Innes
- Cancer Research UK, Cambridge Research Institute, Li Ka Shing Centre, Robinson Way, Cambridge CB20RE, UK
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MacPherson MJ, Sadowski PD. The CTCF insulator protein forms an unusual DNA structure. BMC Mol Biol 2010; 11:101. [PMID: 21176138 PMCID: PMC3014928 DOI: 10.1186/1471-2199-11-101] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2010] [Accepted: 12/21/2010] [Indexed: 11/19/2022] Open
Abstract
Background The CTCF insulator protein is a highly conserved zinc finger protein that has been implicated in many aspects of gene regulation and nuclear organization. The protein has been hypothesized to organize the human genome by forming DNA loops. Results In this paper, we report biochemical evidence to support the role for CTCF in forming DNA loops. We have measured DNA bending by CTCF at the chicken HS4 β-globin FII insulator element in vitro and have observed a unique DNA structure with aberrant electrophoretic mobility which we believe to be a DNA loop. CTCF is able to form this unusual DNA structure at two other binding sites: the c-myc P2 promoter and the chicken F1 lysozyme gene silencer. We also demonstrate that the length though not the sequence of the DNA downstream of the binding site is important for the ability of CTCF to form this unusual DNA structure. We hypothesize that a single CTCF protein molecule is able to act as a "looper" possibly through the use of several of its zinc fingers. Conclusions CTCF is able to form an unusual DNA structure through the zinc finger domain of the protein. This unusual DNA structure is formed in a directional manner by the CTCF protein. The findings described in this paper suggest mechanisms by which CTCF is able to form DNA loops, organize the mammalian genome and function as an insulator protein.
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Affiliation(s)
- Melissa J MacPherson
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
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Abstract
Various factors/pathways including hormonal regulation have been suggested to control HSV-1 latency and reactivation. Our computer analysis identified a DNA repeat containing thyroid hormone response elements (TRE) in the regulatory region of HSV-1 LAT. Thyroid hormone (T3) exerts its function via its receptor (TR), a transcriptional factor. Present study investigated the roles of TR and T3 on HSV-1 gene expression using cultured neuoroblastoma cell lines. We demonstrated that liganded TR activated LAT transcription but repressed ICP0 transcription in the presence of LAT TRE. The chromatin immunoprecipitation (ChIP) assays showed that TRs were recruited to LAT TREs independently of T3 and hyperacetylated H4 was associated with promoters that were transcriptionally active. In addition, ChIP results showed that a chromatin insulator protein CTCF was enriched at the LAT TREs in the presence of TR and T3. In addition, chromatin remodeling factor BRG1 complex is found to participate in the T3/TR-mediated LAT activation since overexpression of BRG1 enhanced the LAT transcription and the dominant negative mutant K785R abolished the activation. This is the first report revealing that TR exerted epigenetic regulation on HSV-1 ICP0 expression in neuronal cells and could have a role in the complex processes of HSV-1 latency/reactivation.
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Farrar D, Rai S, Chernukhin I, Jagodic M, Ito Y, Yammine S, Ohlsson R, Murrell A, Klenova E. Mutational analysis of the poly(ADP-ribosyl)ation sites of the transcription factor CTCF provides an insight into the mechanism of its regulation by poly(ADP-ribosyl)ation. Mol Cell Biol 2010; 30:1199-216. [PMID: 20038529 PMCID: PMC2820893 DOI: 10.1128/mcb.00827-09] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2009] [Revised: 08/02/2009] [Accepted: 12/10/2009] [Indexed: 12/13/2022] Open
Abstract
Poly(ADP-ribosyl)ation of the conserved multifunctional transcription factor CTCF was previously identified as important to maintain CTCF insulator and chromatin barrier functions. However, the molecular mechanism of this regulation and also the necessity of this modification for other CTCF functions remain unknown. In this study, we identified potential sites of poly(ADP-ribosyl)ation within the N-terminal domain of CTCF and generated a mutant deficient in poly(ADP-ribosyl)ation. Using this CTCF mutant, we demonstrated the requirement of poly(ADP-ribosyl)ation for optimal CTCF function in transcriptional activation of the p19ARF promoter and inhibition of cell proliferation. By using a newly generated isogenic insulator reporter cell line, the CTCF insulator function at the mouse Igf2-H19 imprinting control region (ICR) was found to be compromised by the CTCF mutation. The association and simultaneous presence of PARP-1 and CTCF at the ICR, confirmed by single and serial chromatin immunoprecipitation assays, were found to be independent of CTCF poly(ADP-ribosyl)ation. These results suggest a model of CTCF regulation by poly(ADP-ribosyl)ation whereby CTCF and PARP-1 form functional complexes at sites along the DNA, producing a dynamic reversible modification of CTCF. By using bioinformatics tools, numerous sites of CTCF and PARP-1 colocalization were demonstrated, suggesting that such regulation of CTCF may take place at the genome level.
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Affiliation(s)
- Dawn Farrar
- Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, United Kingdom, CRUK Cambridge Research Institute, Li Ka Shing Centre, Robinson Way, Cambridge CB2 0RE, United Kingdom, Box 280, Karolinska Institute, SE-171 77 Stockholm, Sweden
| | - Sushma Rai
- Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, United Kingdom, CRUK Cambridge Research Institute, Li Ka Shing Centre, Robinson Way, Cambridge CB2 0RE, United Kingdom, Box 280, Karolinska Institute, SE-171 77 Stockholm, Sweden
| | - Igor Chernukhin
- Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, United Kingdom, CRUK Cambridge Research Institute, Li Ka Shing Centre, Robinson Way, Cambridge CB2 0RE, United Kingdom, Box 280, Karolinska Institute, SE-171 77 Stockholm, Sweden
| | - Maja Jagodic
- Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, United Kingdom, CRUK Cambridge Research Institute, Li Ka Shing Centre, Robinson Way, Cambridge CB2 0RE, United Kingdom, Box 280, Karolinska Institute, SE-171 77 Stockholm, Sweden
| | - Yoko Ito
- Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, United Kingdom, CRUK Cambridge Research Institute, Li Ka Shing Centre, Robinson Way, Cambridge CB2 0RE, United Kingdom, Box 280, Karolinska Institute, SE-171 77 Stockholm, Sweden
| | - Samer Yammine
- Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, United Kingdom, CRUK Cambridge Research Institute, Li Ka Shing Centre, Robinson Way, Cambridge CB2 0RE, United Kingdom, Box 280, Karolinska Institute, SE-171 77 Stockholm, Sweden
| | - Rolf Ohlsson
- Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, United Kingdom, CRUK Cambridge Research Institute, Li Ka Shing Centre, Robinson Way, Cambridge CB2 0RE, United Kingdom, Box 280, Karolinska Institute, SE-171 77 Stockholm, Sweden
| | - Adele Murrell
- Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, United Kingdom, CRUK Cambridge Research Institute, Li Ka Shing Centre, Robinson Way, Cambridge CB2 0RE, United Kingdom, Box 280, Karolinska Institute, SE-171 77 Stockholm, Sweden
| | - Elena Klenova
- Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, United Kingdom, CRUK Cambridge Research Institute, Li Ka Shing Centre, Robinson Way, Cambridge CB2 0RE, United Kingdom, Box 280, Karolinska Institute, SE-171 77 Stockholm, Sweden
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18
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Bushey AM, Dorman ER, Corces VG. Chromatin insulators: regulatory mechanisms and epigenetic inheritance. Mol Cell 2008; 32:1-9. [PMID: 18851828 DOI: 10.1016/j.molcel.2008.08.017] [Citation(s) in RCA: 132] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2008] [Indexed: 10/21/2022]
Abstract
Enhancer-blocking insulators are DNA elements that disrupt the communication between a regulatory sequence, such as an enhancer or a silencer, and a promoter. Insulators participate in both transcriptional regulation and global nuclear organization, two features of chromatin that are thought to be maintained from one generation to the next through epigenetic mechanisms. Furthermore, there are many regulatory mechanisms in place that enhance or hinder insulator activity. These modes of regulation could be used to establish cell-type-specific insulator activity that is epigenetically inherited along a cell and/or organismal lineage. This review will discuss the evidence for epigenetic inheritance and regulation of insulator function.
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Affiliation(s)
- Ashley M Bushey
- Department of Biology, Emory University, Atlanta, GA 30322, USA
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19
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Murai J, Ikegami D, Okamoto M, Yoshikawa H, Tsumaki N. Insulation of the Ubiquitous Rxrb Promoter from the Cartilage-specific Adjacent Gene, Col11a2. J Biol Chem 2008; 283:27677-27687. [DOI: 10.1074/jbc.m803657200] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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20
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Soshnev AA, Li X, Wehling MD, Geyer PK. Context differences reveal insulator and activator functions of a Su(Hw) binding region. PLoS Genet 2008; 4:e1000159. [PMID: 18704163 PMCID: PMC2493044 DOI: 10.1371/journal.pgen.1000159] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2008] [Accepted: 07/10/2008] [Indexed: 11/19/2022] Open
Abstract
Insulators are DNA elements that divide chromosomes into independent transcriptional domains. The Drosophila genome contains hundreds of binding sites for the Suppressor of Hairy-wing [Su(Hw)] insulator protein, corresponding to locations of the retroviral gypsy insulator and non-gypsy binding regions (BRs). The first non-gypsy BR identified, 1A-2, resides in cytological region 1A. Using a quantitative transgene system, we show that 1A-2 is a composite insulator containing enhancer blocking and facilitator elements. We discovered that 1A-2 separates the yellow (y) gene from a previously unannotated, non-coding RNA gene, named yar for y-achaete (ac) intergenic RNA. The role of 1A-2 was elucidated using homologous recombination to excise these sequences from the natural location, representing the first deletion of any Su(Hw) BR in the genome. Loss of 1A-2 reduced yar RNA accumulation, without affecting mRNA levels from the neighboring y and ac genes. These data indicate that within the 1A region, 1A-2 acts an activator of yar transcription. Taken together, these studies reveal that the properties of 1A-2 are context-dependent, as this element has both insulator and enhancer activities. These findings imply that the function of non-gypsy Su(Hw) BRs depends on the genomic environment, predicting that Su(Hw) BRs represent a diverse collection of genomic regulatory elements.
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Affiliation(s)
- Alexey A. Soshnev
- Program in Molecular and Cellular Biology, University of Iowa, Iowa City, Iowa, United States of America
| | - Xingguo Li
- Department of Biochemistry, University of Iowa, Iowa City, Iowa, United States of America
| | - Misty D. Wehling
- Program in Molecular and Cellular Biology, University of Iowa, Iowa City, Iowa, United States of America
| | - Pamela K. Geyer
- Program in Molecular and Cellular Biology, University of Iowa, Iowa City, Iowa, United States of America
- Department of Biochemistry, University of Iowa, Iowa City, Iowa, United States of America
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21
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Zhou X, Weatherford ET, Liu X, Born E, Keen HL, Sigmund CD. Dysregulated human renin expression in transgenic mice carrying truncated genomic constructs: evidence supporting the presence of insulators at the renin locus. Am J Physiol Renal Physiol 2008; 295:F642-53. [PMID: 18632798 DOI: 10.1152/ajprenal.00384.2007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We previously generated transgenic mice carrying a large P1 artificial chromosome (PAC160) encompassing a 160-kb segment containing the human renin gene, two upstream genes, and one downstream gene. We also previously generated mutant PAC160 constructs lacking the distal enhancer and concluded it is required to maintain baseline expression of human renin, but is not required for tissue-specific, cell-specific, and regulated expression of renin in vivo. We now report two additional transgenic lines carrying random truncations of PAC160 upstream of the renin gene. Southern and PCR mapping studies indicate that the truncation break points in the two lines are located approximately 10.4 and 2.5 kb upstream of the renin gene causing a deletion of all DNA upstream of the break. We tested the hypothesis that large-scale deletion of DNA upstream of the human renin gene including the enhancer would cause dysregulation of human renin expression. Phenotypically, these truncations cause a severe dysregulation of human renin expression, but remarkably, a preservation of the normal tissue-specific expression of the human ethanolamine kinase 2 (ETNK2) gene which lies immediately downstream of renin. Several functional binding sites for CTCF, a mammalian insulator protein, were identified in and around the renin and ETNK2 loci by gel shift and chromatin immunoprecipitation. We conclude that there are sequences in and around the renin and ETNK2 loci which act as boundaries between neighboring genes which insulate them from each other. The study illustrates the value of taking a much wider genomic perspective when studying mechanisms regulating gene expression.
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Affiliation(s)
- Xiyou Zhou
- Molecular and Cellular Graduate Program, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
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22
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Li Y, Li G, Ivanova A, Aaron S, Simm M. The critical role of human transcriptional repressor CTCF mRNA up-regulation in the induction of anti-HIV-1 responses in CD4(+) T cells. Immunol Lett 2007; 117:35-44. [PMID: 18207574 DOI: 10.1016/j.imlet.2007.11.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2007] [Revised: 11/26/2007] [Accepted: 11/26/2007] [Indexed: 12/26/2022]
Abstract
We have employed our CD4(+) T cell model named HIV-1 resistance factor (HRF(+)) to study the inducible anti-HIV-1 responses mediated through novel soluble molecules. We found that exposure to the soluble products of HRF(+) cells activated CCCTC-binding factor (CTCF) mRNA expression in HIV-1 susceptible primary and transformed CD4(+) T cells and overlapped with their acquisition of transient resistance to virus. Conversely, the interference with the expression of CTCF gene in HRF(+) cells reversed the resistant phenotype and eliminated the biological potential of their cell culture supernatant to induce "HRF-like" activity in target cells. Band-shift analysis upon the nuclear fractions from HIV-1 resistant cells showed that CTCF protein bound to HIV-1 promoter and this binding prevented the formation of NF-kappaB/LTR complex. This evidence suggests that CTCF is an intracellular effector of HRF activity and that the acquisition of resistance to HIV-1 in CD4(+) T cells is a consequence of the prior activation of CTCF gene by the soluble entity secreted by HRF(+) cells.
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Affiliation(s)
- Yuchang Li
- Molecular Virology Division, St. Luke's-Roosevelt Hospital Center, Columbia University Medical Center, New York, NY 10019, USA
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23
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Li T, Lu L. Functional role of CCCTC binding factor (CTCF) in stress-induced apoptosis. Exp Cell Res 2007; 313:3057-65. [PMID: 17583694 PMCID: PMC2706011 DOI: 10.1016/j.yexcr.2007.05.018] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2007] [Revised: 05/02/2007] [Accepted: 05/17/2007] [Indexed: 10/23/2022]
Abstract
CTCF, a nuclear transcriptional factor, is a multifunctional protein and involves regulation of growth factor- and cytokine-induced cell proliferation/differentiation. In the present study, we investigated the role of CTCF in protecting stress-induced apoptosis in various human cell types. We found that UV irradiation and hyper-osmotic stress induced human corneal epithelial (HCE) and hematopoietic myeloid cell apoptosis detected by significantly increased caspase 3 activity and decreased cell viability. The stress-induced apoptotic response in these cells requires down-regulation of CTCF at both mRNA and protein levels, suggesting that CTCF may play an important role in downstream events of stress-induced signaling pathways. Inhibition of NFkappaB activity prevented stress-induced down-regulation of CTCF and increased cell viability against stress-induced apoptosis. The anti-apoptotic effect of CTCF was further studied by manipulating CTCF activities in HCE and hematopoietic cells. Transient transfection of cDNAs encoding full-length human CTCF markedly suppressed stress-induced apoptosis in these cells. In contrast, knocking down of CTCF mRNA using siRNA specific to CTCF significantly promoted stress-induced apoptosis. Thus, our results reveal that CTCF is a down stream target of stress-induced signaling cascades and it plays a significant anti-apoptotic role in regulation of stress-induced cellular responses in HCE and hematopoietic myeloid cells.
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Affiliation(s)
| | - Luo Lu
- Address correspondence to: Luo Lu, Division of Molecular Medicine, UCLA School of Medicine, Harbor-UCLA Medical Center, 1124 W. Carson Street, C-2, Torrance, CA 90502, Tel. 310 787-6853, Fax. 310 222-3781, E-mail:
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24
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Kim TH, Abdullaev ZK, Smith AD, Ching KA, Loukinov DI, Green RD, Zhang MQ, Lobanenkov VV, Ren B. Analysis of the vertebrate insulator protein CTCF-binding sites in the human genome. Cell 2007; 128:1231-45. [PMID: 17382889 PMCID: PMC2572726 DOI: 10.1016/j.cell.2006.12.048] [Citation(s) in RCA: 791] [Impact Index Per Article: 46.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2006] [Revised: 11/23/2006] [Accepted: 12/28/2006] [Indexed: 12/31/2022]
Abstract
Insulator elements affect gene expression by preventing the spread of heterochromatin and restricting transcriptional enhancers from activation of unrelated promoters. In vertebrates, insulator's function requires association with the CCCTC-binding factor (CTCF), a protein that recognizes long and diverse nucleotide sequences. While insulators are critical in gene regulation, only a few have been reported. Here, we describe 13,804 CTCF-binding sites in potential insulators of the human genome, discovered experimentally in primary human fibroblasts. Most of these sequences are located far from the transcriptional start sites, with their distribution strongly correlated with genes. The majority of them fit to a consensus motif highly conserved and suitable for predicting possible insulators driven by CTCF in other vertebrate genomes. In addition, CTCF localization is largely invariant across different cell types. Our results provide a resource for investigating insulator function and possible other general and evolutionarily conserved activities of CTCF sites.
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Affiliation(s)
- Tae Hoon Kim
- Ludwig Institute for Cancer Research, 9500 Gilman Drive, La Jolla, CA 92093-0653
- To whom correspondence should be addressed,
,
| | - Ziedulla K. Abdullaev
- National Institutes of Allergy and Infectious Disease, 5640 Fishers Lane, Rockville, MD 20852
| | - Andrew D. Smith
- Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724
| | - Keith A. Ching
- Ludwig Institute for Cancer Research, 9500 Gilman Drive, La Jolla, CA 92093-0653
| | - Dmitri I. Loukinov
- National Institutes of Allergy and Infectious Disease, 5640 Fishers Lane, Rockville, MD 20852
| | | | - Michael Q. Zhang
- Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724
| | - Victor V. Lobanenkov
- National Institutes of Allergy and Infectious Disease, 5640 Fishers Lane, Rockville, MD 20852
| | - Bing Ren
- Ludwig Institute for Cancer Research, 9500 Gilman Drive, La Jolla, CA 92093-0653
- To whom correspondence should be addressed,
,
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25
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Kouprina N, Noskov VN, Pavlicek A, Collins NK, Schoppee Bortz PD, Ottolenghi C, Loukinov D, Goldsmith P, Risinger JI, Kim JH, Westbrook VA, Solomon G, Sounders H, Herr JC, Jurka J, Lobanenkov V, Schlessinger D, Larionov V. Evolutionary diversification of SPANX-N sperm protein gene structure and expression. PLoS One 2007; 2:e359. [PMID: 17406683 PMCID: PMC1831492 DOI: 10.1371/journal.pone.0000359] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2007] [Accepted: 03/08/2007] [Indexed: 11/19/2022] Open
Abstract
The sperm protein associated with nucleus in the X chromosome (SPANX) genes cluster at Xq27 in two subfamilies, SPANX-A/D and SPANX-N. SPANX-A/D is specific for hominoids and is fairly well characterized. The SPANX-N gave rise to SPANX-A/D in the hominoid lineage ∼7 MYA. Given the proposed role of SPANX genes in spermatogenesis, we have extended studies to SPANX-N gene evolution, variation, regulation of expression, and intra-sperm localization. By immunofluorescence analysis, SPANX-N proteins are localized in post-meiotic spermatids exclusively, like SPANX-A/D. But in contrast to SPANX-A/D, SPANX-N are found in all ejaculated spermatozoa rather than only in a subpopulation, are localized in the acrosome rather than in the nuclear envelope, and are expressed at a low level in several nongametogenic adult tissues as well as many cancers. Presence of a binding site for CTCF and its testis-specific paralogue BORIS in the SPANX promoters suggests, by analogy to MAGE-A1 and NY-ESO-1, that their activation in spermatogenesis is mediated by the programmed replacement of CTCF by BORIS. Based on the relative density of CpG, the more extended expression of SPANX-N compared to SPANX-A/D in nongametogenic tissues is likely attributed to differences in promoter methylation. Our findings suggest that the recent duplication of SPANX genes in hominoids was accompanied by different localization of SPANX-N proteins in post-meiotic sperm and additional expression in several nongonadal tissues. This suggests a corresponding functional diversification of SPANX gene families in hominoids. SPANX proteins thus provide unique targets to investigate their roles in the function of spermatozoa, selected malignancies, and for SPANX-N, in other tissues as well.
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Affiliation(s)
- Natalay Kouprina
- Laboratory of Molecular Pharmacology, National Cancer Institute (NCI), National Institutes of Health, Bethesda, Maryland, United States of America.
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26
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Abstract
PURPOSE A previous study demonstrated that CTCF (CCCTC binding factor) regulates homeobox Pax6 gene expression in early embryonic stages and plays a dominant role in eye development. The purpose of the present study was to explore further the mechanism of CTCF controlling Pax6 gene expression in human retinoblastoma (Rb) cells and in the development of chicken and mouse retinas. METHODS Northern and Western analyses were used to detect expressions of CTCF and Pax6 in Rb cells. Pax6 transcription reporter and deletion mutants were used to study the regulatory interaction between CTCF and Pax6 in Rb cells and in the retina of chicken embryos. CTCF transgenic chicken embryos and mice were established by lipofection and microinjection of linearized cytomegalovirus (CMV)-CTCF construct into fertilized eggs and mouse oocytes, respectively. Injected oocytes were implanted in the uterus of foster mothers through microinjection into the ovarian duct. The expression of CTCF and Pax6 was determined in embryo sections by immunochemistry. RESULTS Stimulation of Rb cells with 10% FBS resulted in an increase in CTCF expression and a decrease in Pax6 expression. To study the regulatory mechanism, the Pax6 reporter and its deletion mutant activities were determined in transfected Rb cells and chicken embryonic retinas, revealing that CTCF interacts with the Pax6 gene in Rb cells through transcription control in the 5'-flanking region upstream from the Pax6 P0 promoter. Overexpression of CTCF in Rb cells suppressed Pax6 reporter activity and downregulated endogenous Pax6 expression. In contrast, downregulation of CTCF expression by knockdown of CTCF mRNA using specific small interfering (si)RNA markedly enhanced Pax6 expression in Rb cells. Further study in CTCF transgenic mouse embryos verified that overexpression of CTCF suppressed Pax6 gene expression in the retina. CONCLUSIONS CTCF plays an important role in regulating Pax6 expression in Rb cells and in the developmental retina, and the regulation of Pax6 gene expression by CTCF in the retina is through transcriptional regulation.
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Affiliation(s)
- Tie Li
- Division of Molecular Medicine, Harbor-UCLA Medical Center, David Geffen School of Medicine, University of California Los Angeles, Torrance, California
| | - Zhenyu Lu
- Department of Medical Genetics, Shanghai Second Medical University, Shanghai, Peoples Republic of China
| | - Luo Lu
- Division of Molecular Medicine, Harbor-UCLA Medical Center, David Geffen School of Medicine, University of California Los Angeles, Torrance, California
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27
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Fitzpatrick GV, Pugacheva EM, Shin JY, Abdullaev Z, Yang Y, Khatod K, Lobanenkov VV, Higgins MJ. Allele-specific binding of CTCF to the multipartite imprinting control region KvDMR1. Mol Cell Biol 2007; 27:2636-47. [PMID: 17242189 PMCID: PMC1899897 DOI: 10.1128/mcb.02036-06] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Paternal deletion of the imprinting control region (ICR) KvDMR1 results in loss of expression of the Kcnq1ot1 noncoding RNA and derepression of flanking paternally silenced genes. Truncation of Kcnq1ot1 also results in the loss of imprinted expression of these genes in most cases, demonstrating a role for the RNA or its transcription in gene silencing. However, enhancer-blocking studies indicate that KvDMR1 also contains chromatin insulator or silencer activity. In this report we demonstrate by electrophoretic mobility shift assays and chromatin immunoprecipitation the existence of two CTCF binding sites within KvDMR1 that are occupied in vivo only on the unmethylated paternally derived allele. Methylation interference and mutagenesis allowed the precise mapping of protein-DNA contact sites for CTCF within KvDMR1. Using a luciferase reporter assay, we mapped the putative transcriptional promoter for Kcnq1ot1 upstream and to a site functionally separable from enhancer-blocking activity and CTCF binding sites. Luciferase reporter assays also suggest the presence of an additional cis-acting element in KvDMR1 upstream of the putative promoter that can function as an enhancer. These results suggest that the KvDMR1 ICR consists of multiple, independent cis-acting modules. Dissection of KvDMR1 into its functional components should help elucidate the mechanism of its function in vivo.
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Affiliation(s)
- Galina V Fitzpatrick
- Department of Cancer Genetics, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, NY 14263, USA
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28
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Hancock AL, Brown KW, Moorwood K, Moon H, Holmgren C, Mardikar SH, Dallosso AR, Klenova E, Loukinov D, Ohlsson R, Lobanenkov VV, Malik K. A CTCF-binding silencer regulates the imprinted genes AWT1 and WT1-AS and exhibits sequential epigenetic defects during Wilms' tumourigenesis. Hum Mol Genet 2007; 16:343-54. [PMID: 17210670 DOI: 10.1093/hmg/ddl478] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We have shown previously that AWT1 and WT1-AS are functionally imprinted in human kidney. In the adult kidney, expression of both transcripts is restricted to the paternal allele, with the silent maternal allele retaining methylation at the WT1 antisense regulatory region (WT1 ARR). Here, we report characterization of the WT1 ARR differentially methylated region and show that it contains a transcriptional silencer element acting on both the AWT1 and WT1-AS promoters. DNA methylation of the silencer results in increased transcriptional repression, and the silencer is also shown to be an in vitro and in vivo target site for the imprinting regulator protein CTCF. Binding of CTCF is methylation-sensitive and limited to the unmethylated silencer. Potentiation of the silencer activity is demonstrated after CTCF protein is knocked down, suggesting a novel silencer-blocking activity for CTCF. We also report assessment of WT1 ARR methylation in developmental and tumour tissues, including the first analysis of Wilms' tumour precursor lesions, nephrogenic rests. Nephrogenic rests show increases in methylation levels relative to foetal kidney and reductions relative to the adult kidney, together with biallelic expression of AWT1 and WT1-AS. Notably, the methylation status of CpG residues within the CTCF target site appears to distinguish monoallelic and biallelic expression states. Our data suggest that failure of methylation spreading at the WT1 ARR early in renal development, followed by imprint erasure, occurs during Wilms' tumourigenesis. We propose a model wherein imprinting defects at chromosome 11p13 may contribute to Wilms' tumourigenesis.
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Affiliation(s)
- Anne L Hancock
- Cancer and Leukaemia in Childhood, Sargent Research Unit, Department of Cellular and Molecular Medicine, School of Medical Sciences, University of Bristol, University Walk, Bristol, UK
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29
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Abstract
Recent advances in studying long-range chromatin interactions have shifted focus from the transcriptional regulation by nearby regulatory elements to recognition of the role of higher-order chromatin organization within the nucleus. These advances have also suggested that CCCTC-binding factor (CTCF), a known chromatin insulator protein, may play a central role in mediating long-range chromatin interactions, directing DNA segments into transcription factories and/or facilitating interactions with other DNA regions. Several models that describe possible mechanisms for multiple functions of CTCF in establishment and maintenance of epigenetic programs are now emerging. Epigenetics plays an important role in normal development and disease including cancer. CTCF involvement in multiple aspects of epigenetic regulation, including regulation of genomic imprinting and X-chromosome inactivation, has been well established. More recently, CTCF was found to play a role in regulation of noncoding transcription and establishing local chromatin structure at the repetitive elements in mammalian genomes, suggesting a new epigenetic basis for several repeat-associated genetic disorders. Emerging evidence also points to the role of CTCF deregulation in the epigenetic imbalance in cancer. These studies provide some of the important missing links in our understanding of epigenetic control of both development and cancer.
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Affiliation(s)
- Galina N Filippova
- Human Biology Division, Fred Hutchinson Cancer Research Center Seattle, Washington 98109, USA
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30
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Kurukuti S, Tiwari VK, Tavoosidana G, Pugacheva E, Murrell A, Zhao Z, Lobanenkov V, Reik W, Ohlsson R. CTCF binding at the H19 imprinting control region mediates maternally inherited higher-order chromatin conformation to restrict enhancer access to Igf2. Proc Natl Acad Sci U S A 2006; 103:10684-9. [PMID: 16815976 PMCID: PMC1484419 DOI: 10.1073/pnas.0600326103] [Citation(s) in RCA: 393] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
It is thought that the H19 imprinting control region (ICR) directs the silencing of the maternally inherited Igf2 allele through a CTCF-dependent chromatin insulator. The ICR has been shown to interact physically with a silencer region in Igf2, differentially methylated region (DMR)1, but the role of CTCF in this chromatin loop and whether it restricts the physical access of distal enhancers to Igf2 is not known. We performed systematic chromosome conformation capture analyses in the Igf2/H19 region over >160 kb, identifying sequences that interact physically with the distal enhancers and the ICR. We found that, on the paternal chromosome, enhancers interact with the Igf2 promoters but that, on the maternal allele, this is prevented by CTCF binding within the H19 ICR. CTCF binding in the maternal ICR regulates its interaction with matrix attachment region (MAR)3 and DMR1 at Igf2, thus forming a tight loop around the maternal Igf2 locus, which may contribute to its silencing. Mutation of CTCF binding sites in the H19 ICR leads to loss of CTCF binding and de novo methylation of a CTCF target site within Igf2 DMR1, showing that CTCF can coordinate regional epigenetic marks. This systematic chromosome conformation capture analysis of an imprinting cluster reveals that CTCF has a critical role in the epigenetic regulation of higher-order chromatin structure and gene silencing over considerable distances in the genome.
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Affiliation(s)
- Sreenivasulu Kurukuti
- Department of Development and Genetics, Uppsala University, Norbyvägen 18A, S-752 36 Uppsala, Sweden
| | - Vijay Kumar Tiwari
- Department of Development and Genetics, Uppsala University, Norbyvägen 18A, S-752 36 Uppsala, Sweden
| | - Gholamreza Tavoosidana
- Department of Development and Genetics, Uppsala University, Norbyvägen 18A, S-752 36 Uppsala, Sweden
| | - Elena Pugacheva
- Laboratory of Immunopathology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892-0760
| | - Adele Murrell
- Department of Oncology and The Hutchison/Medical Research Council Research Centre, University of Cambridge, Cambridge CB2 2XE, United Kingdom; and
| | - Zhihu Zhao
- Department of Development and Genetics, Uppsala University, Norbyvägen 18A, S-752 36 Uppsala, Sweden
| | - Victor Lobanenkov
- Laboratory of Immunopathology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892-0760
| | - Wolf Reik
- Laboratory of Developmental Genetics and Imprinting, The Babraham Institute, Cambridge CB2 4AT, United Kingdom
- To whom correspondence may be addressed. E-mail:
or
| | - Rolf Ohlsson
- Department of Development and Genetics, Uppsala University, Norbyvägen 18A, S-752 36 Uppsala, Sweden
- To whom correspondence may be addressed. E-mail:
or
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31
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Pugacheva EM, Kwon YW, Hukriede NA, Pack S, Flanagan PT, Ahn JC, Park JA, Choi KS, Kim KW, Loukinov D, Dawid IB, Lobanenkov VV. Cloning and characterization of zebrafish CTCF: Developmental expression patterns, regulation of the promoter region, and evolutionary aspects of gene organization. Gene 2006; 375:26-36. [PMID: 16647825 DOI: 10.1016/j.gene.2006.01.036] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2005] [Revised: 12/28/2005] [Accepted: 01/31/2006] [Indexed: 11/20/2022]
Abstract
CTCF is a nuclear phosphoprotein capable of using different subsets of its 11 Zn fingers (ZF) for sequence-specific binding to many dissimilar DNA CTCF-target sites. Such sites were identified in the genomic DNA of various multicellular organisms, in which the CTCF gene was cloned, including insects, birds, rodents, and primates. CTCF/DNA-complexes formed in vivo with different 50-bp-long sequences mediate diverse functions such as positive and negative regulation of promoters, and organization of all known enhancer-blocking elements ("chromatin insulators") including constitutive and epigenetically regulated elements. Abnormal functions of certain CTCF sites are implicated in cancer and in epigenetic syndromes such as BWS and skewed X-inactivation. We describe here the cloning and characterization of the CTCF cDNA and promoter region from zebrafish, a valuable vertebrate model organism. The full-length zebrafish CTCF cDNA clone is 4244 bp in length with an open reading frame (ORF) of 2391 bp that encodes 797 amino acids. The zebrafish CTCF amino acid sequence shows high identity (up to 98% in the zinc finger region) with human CTCF, and perfect conservation of exon-intron organization. Southern blot analyses indicated that the zebrafish genome contains a single copy of the CTCF gene. In situ hybridization revealed the presence of zebrafish CTCF transcripts in all early stages of embryogenesis. Transfection assays with luciferase reporter-constructs identified a core promoter region within 146 bp immediately upstream of the transcriptional start site of zebrafish CTCF that is located at a highly conserved YY1/Initiator element.
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Affiliation(s)
- Elena M Pugacheva
- Molecular Pathology Section, Laboratory of Immunopathology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA.
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32
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Hong JA, Kang Y, Abdullaev Z, Flanagan PT, Pack SD, Fischette MR, Adnani MT, Loukinov DI, Vatolin S, Risinger JI, Custer M, Chen GA, Zhao M, Nguyen DM, Barrett JC, Lobanenkov VV, Schrump DS. Reciprocal binding of CTCF and BORIS to the NY-ESO-1 promoter coincides with derepression of this cancer-testis gene in lung cancer cells. Cancer Res 2005; 65:7763-74. [PMID: 16140944 DOI: 10.1158/0008-5472.can-05-0823] [Citation(s) in RCA: 141] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Regulatory sequences recognized by the unique pair of paralogous factors, CTCF and BORIS, have been implicated in epigenetic regulation of imprinting and X chromosome inactivation. Lung cancers exhibit genome-wide demethylation associated with derepression of a specific class of genes encoding cancer-testis (CT) antigens such as NY-ESO-1. CT genes are normally expressed in BORIS-positive male germ cells deficient in CTCF and meCpG contents, but are strictly silenced in somatic cells. The present study was undertaken to ascertain if aberrant activation of BORIS contributes to derepression of NY-ESO-1 during pulmonary carcinogenesis. Preliminary experiments indicated that NY-ESO-1 expression coincided with derepression of BORIS in cultured lung cancer cells. Quantitative reverse transcription-PCR analysis revealed robust, coincident induction of BORIS and NY-ESO-1 expression in lung cancer cells, but not normal human bronchial epithelial cells following 5-aza-2'-deoxycytidine (5-azadC), Depsipeptide FK228 (DP), or sequential 5-azadC/DP exposure under clinically relevant conditions. Bisulfite sequencing, methylation-specific PCR, and chromatin immunoprecipitation (ChIP) experiments showed that induction of BORIS coincided with direct modulation of chromatin structure within a CpG island in the 5'-flanking noncoding region of this gene. Cotransfection experiments using promoter-reporter constructs confirmed that BORIS modulates NY-ESO-1 expression in lung cancer cells. Gel shift and ChIP experiments revealed a novel CTCF/BORIS-binding site in the NY-ESO-1 promoter, which unlike such sites in the H19-imprinting control region and X chromosome, is insensitive to CpG methylation in vitro. In vivo occupancy of this site by CTCF was associated with silencing of the NY-ESO-1 promoter, whereas switching from CTCF to BORIS occupancy coincided with derepression of NY-ESO-1. Collectively, these data indicate that reciprocal binding of CTCF and BORIS to the NY-ESO-1 promoter mediates epigenetic regulation of this CT gene in lung cancer cells, and suggest that induction of BORIS may be a novel strategy to augment immunogenicity of pulmonary carcinomas.
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Affiliation(s)
- Julie A Hong
- Thoracic Oncology Section, Surgery Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892-1201, USA
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33
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Vatolin S, Abdullaev Z, Pack SD, Flanagan PT, Custer M, Loukinov DI, Pugacheva E, Hong JA, Morse H, Schrump DS, Risinger JI, Barrett JC, Lobanenkov VV. Conditional Expression of the CTCF-Paralogous Transcriptional Factor BORIS in Normal Cells Results in Demethylation and Derepression of MAGE-A1 and Reactivation of Other Cancer-Testis Genes. Cancer Res 2005; 65:7751-62. [PMID: 16140943 DOI: 10.1158/0008-5472.can-05-0858] [Citation(s) in RCA: 149] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Brother of the Regulator of Imprinted Sites (BORIS) is a mammalian CTCF paralog with the same central 11Zn fingers (11ZF) that mediate specific interactions with varying approximately 50-bp target sites. Regulated in vivo occupancy of such sites may yield structurally and functionally distinct CTCF/DNA complexes involved in various aspects of gene regulation, including epigenetic control of gene imprinting and X chromosome inactivation. The latter functions are mediated by meCpG-sensitive 11ZF binding. Because CTCF is normally present in all somatic cells, whereas BORIS is active only in CTCF- and 5-methylcytosine-deficient adult male germ cells, switching DNA occupancy from CTCF to BORIS was suggested to regulate site specificity and timing of epigenetic reprogramming. In addition to 11ZF-binding paternal imprinting control regions, cancer-testis gene promoters also undergo remethylation during CTCF/BORIS switching in germ cells. Only promoters of cancer testis genes are normally silenced in all somatic cells but activated during spermatogenesis when demethylated in BORIS-positive germ cells and are found aberrantly derepressed in various tumors. We show here that BORIS is also expressed in multiple cancers and is thus itself a cancer-testis gene and that conditional expression of BORIS in normal fibroblasts activates cancer-testis genes selectively. We tested if replacement of CTCF by BORIS on regulatory DNA occurs in vivo on activation of a prototype cancer-testis gene, MAGE-A1. Transition from a hypermethylated/silenced to a hypomethylated/activated status induced in normal cells by 5-aza-2'-deoxycytidine (5-azadC) was mimicked by conditional input of BORIS and is associated with complete switching from CTCF to BORIS occupancy at a single 11ZF target. This site manifested a novel type of CTCF/BORIS 11ZF binding insensitive to CpG methylation. Whereas 5-azadC induction of BORIS takes only few hours, derepression of MAGE-A1 occurred 1 to 2 days later, suggesting that BORIS mediates cancer-testis gene activation by 5-azadC. Indeed, infection of normal fibroblasts with anti-BORIS short hairpin RNA retroviruses before treatment with 5-azadC blocked reactivation of MAGE-A1. We suggest that BORIS is likely tethering epigenetic machinery to a novel class of CTCF/BORIS 11ZF target sequences that mediate induction of cancer-testis genes.
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Affiliation(s)
- Sergei Vatolin
- Laboratory of Immunopathology, National Institutes of Allergy and Infectious Disease, NIH, Bethesda, Maryland, USA
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El-Kady A, Klenova E. Regulation of the transcription factor, CTCF, by phosphorylation with protein kinase CK2. FEBS Lett 2005; 579:1424-34. [PMID: 15733852 DOI: 10.1016/j.febslet.2005.01.044] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2004] [Revised: 12/10/2004] [Accepted: 01/13/2005] [Indexed: 01/30/2023]
Abstract
CTCF is a transcription factor involved in various aspects of gene regulation. We previously reported that CTCF function is modulated by protein kinase CK2. In this report we investigate further the role of CK2 in regulating the transcriptional properties of CTCF. We demonstrate that coexpression of CTCF with CK2 switches function of CTCF from repressor to activator. The non-phosphorylatable mutant increases repression by CTCF and potentiates the growth-suppressive ability of the protein, whereas the phospho-mimetic mutant behaves in the opposite fashion. Mutation of the individual serines reveals that Serine 612 is a critical residue in regulation of CTCF by CK2.
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Affiliation(s)
- Ayman El-Kady
- Genetics Unit, Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
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35
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Pugacheva EM, Tiwari VK, Abdullaev Z, Vostrov AA, Flanagan PT, Quitschke WW, Loukinov DI, Ohlsson R, Lobanenkov VV. Familial cases of point mutations in the XIST promoter reveal a correlation between CTCF binding and pre-emptive choices of X chromosome inactivation. Hum Mol Genet 2005; 14:953-65. [PMID: 15731119 DOI: 10.1093/hmg/ddi089] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The choice mechanisms that determine the future inactive X chromosome in somatic cells of female mammals involve the regulated expression of the XIST gene. A familial C(-43)G mutation in the XIST promoter results in skewing of X chromosome inactivation (XCI) towards the inactive X chromosome of heterozygous females, whereas a C(-43)A mutation found primarily in the active X chromosome results in the opposite skewing pattern. Both mutations point to the existence of a factor that might be responsible for the skewed patterns. Here we identify this factor as CTCF, a conserved protein with a 11 Zn-finger (ZF) domain that can mediate multiple sequence-specificity and interactions between DNA-bound CTCF molecules. We show that mouse and human Xist/XIST promoters contain one homologous CTCF-binding sequence with the matching dG-contacts, which in the human XIST include the -43 position within the DNase I footprint of CTCF. While the C(-43)A mutation abrogates CTCF binding, the C(-43)G mutation results in a dramatic increase in CTCF-binding efficiency by altering ZF-usage mode required for recognition of the altered dG-contacts of the mutant site. Thus, the skewing effect of the two -43C mutations correlates with their effects on CTCF binding. Finally, CTCF interacts with the XIST/Xist promoter only in female human and mouse cells. The interpretation that this reflected a preferential interaction with the promoter of the active Xist allele was confirmed in mouse fetal placenta. These observations are in keeping with the possibility that the choice of X chromosome inactivation reflects stabilization of a higher order chromatin conformation impinging on the CTCF-XIST promoter complex.
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MESH Headings
- Alleles
- Animals
- Base Sequence
- CCCTC-Binding Factor
- Cell Nucleus/metabolism
- Chromatin/metabolism
- Chromatin Immunoprecipitation
- Chromosomes, Human, X
- DNA Methylation
- DNA-Binding Proteins/genetics
- DNA-Binding Proteins/metabolism
- Deoxyribonuclease I/metabolism
- Dosage Compensation, Genetic
- Family Health
- Female
- Heterozygote
- Humans
- Immunoprecipitation
- Male
- Mice
- Models, Genetic
- Molecular Sequence Data
- Mutation
- Plasmids/metabolism
- Point Mutation
- Promoter Regions, Genetic
- Protein Binding
- Protein Biosynthesis
- Protein Conformation
- Protein Structure, Tertiary
- RNA, Long Noncoding
- RNA, Untranslated/genetics
- Repressor Proteins/genetics
- Repressor Proteins/metabolism
- Sequence Homology, Nucleic Acid
- Sex Factors
- Transcription, Genetic
- Zinc Fingers
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Affiliation(s)
- Elena M Pugacheva
- Molecular Pathology Section, Laboratory of Immunopathology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 5640 Fishers Lane, Twinbrook I Rm. 1417, Rockville, MD 20852, USA
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36
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Weidman JR, Murphy SK, Nolan CM, Dietrich FS, Jirtle RL. Phylogenetic footprint analysis of IGF2 in extant mammals. Genome Res 2004; 14:1726-32. [PMID: 15342558 PMCID: PMC515318 DOI: 10.1101/gr.2774804] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Genomic imprinting results in monoallelic gene transcription that is directed by cis-acting regulatory elements epigenetically marked in a parent-of-origin-dependent manner. We performed phylogenetic sequence and epigenetic comparisons of IGF2 between the nonimprinted platypus (Ornithorhynchus anatinus) and imprinted opossum (Didelphis virginiana), mouse (Mus musculus), and human (Homo sapiens) to determine if their divergent imprint status would reflect differences in the conservation of genomic elements important in the regulation of imprinting. We report herein that IGF2 imprinting does not correlate evolutionarily with differential intragenic methylation, nor is it associated with motif 13, a reported IGF2-specific "imprint signature" located in the coding region. Instead, IGF2 imprinting is strongly associated with both the lack of short interspersed transposable elements (SINEs) and an intragenic conserved inverted repeat that contains candidate CTCF-binding sites, a role not previously ascribed to this particular sequence element. Our results are the first to demonstrate that comparative footprint analysis of species from evolutionarily distant mammalian clades, and exhibiting divergent imprint status is a powerful bioinformatics-based approach for identifying cis-acting elements potentially involved not only in the origins of genomic imprinting, but also in its maintenance in humans.
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Affiliation(s)
- Jennifer R Weidman
- Department of Radiation Oncology, Duke University, Durham, North Carolina 27710, USA
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37
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Kim SW, Hong SJ, Kim KM, Ho SC, So EC, Harney JW, Larsen PR. A novel cell type-specific mechanism for thyroid hormone-dependent negative regulation of the human type 1 deiodinase gene. Mol Endocrinol 2004; 18:2924-36. [PMID: 15331760 DOI: 10.1210/me.2004-0255] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
We have identified a cell type-specific, negative thyroid hormone-responsive element in the human type 1 iodothyronine deiodinase (hdio1) gene. This fragment, termed a JEG response element, bound tightly to a JEG-cell nuclear protein [JEG cell-specific transcription factor (JTF)] also present in placenta but not in COS-7, HeLa, or human embryonic kidney-293 cells. In JEG-3 cells, three copies of the JEG response element conferred a more than 40-fold transcriptional stimulation to the heterologous rat GH promoter which was further increased 2-fold by apo-thyroid hormone receptor (TR) and reduced 3-fold by T(3). Dimethyl sulfide footprinting showed overlapping contact sites for the high-affinity interaction of JTF and low-affinity binding of TR-retinoid X receptor. Expression of the same construct was unaffected by TR or T(3) in COS cells, indicating JTF was required for negative regulation by T(3)-TR. Mutations of the critical thyroid hormone responsive element binding P box amino acids EG to GS in TRalpha1 or TRbeta2 eliminated the apo-TR and T(3)-TR effects. These studies identify a novel mechanism for cell type-specific, promoter-independent negative regulation by T(3).
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Affiliation(s)
- Sung-Woo Kim
- Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, Brigham and Women's Hospital, Harvard Institute of Medicine, 77 Avenue Louis Pasteur, Boston, Massachusetts 02115, USA.
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38
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Li T, Lu Z, Lu L. Regulation of eye development by transcription control of CCCTC binding factor (CTCF). J Biol Chem 2004; 279:27575-83. [PMID: 15096508 DOI: 10.1074/jbc.m313942200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
CCCTC binding factor (CTCF), a transcriptional regulator, plays important roles in epigenetics and development. In the present study, we report that overexpression of CTCF in transgenic mice during embryonic development suppresses Pax6 gene expression. This effect causes defects in ocular development that result in microophthalmia. In eye-derived cells transfected with a tetracycline turn-on CTCF system, up-regulation of CTCF expression significantly suppressed Pax6 expression. In contrast, the knockdown of CTCF mRNA resulted in the down-regulation of CTCF protein expression, which in turn enhanced the Pax6 expression. CTCF controls Pax6 transcription by interacting with a repressor element located in the 5'-flanking region upstream of the Pax6 P0 promoter. This interaction suppressed Pax6 gene transcription by blocking the effect of an ectoderm enhancer located 3.5 kb upstream from the P0 promoter. We also found an 80-bp sequence in a region -1.2 kbp upstream from the P0 promoter that contained multiple CTCF binding sites and interacted with nuclear proteins obtained from eye-derived cells forming electrophoretic mobility shift assay complexes with CTCF. We conclude that a novel function of CTCF is to regulate Pax6 transcription by binding to the repressor element, which in turn blocks the effect of the ectoderm enhancer resulting in the inhibition of P0 promoter activity.
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Affiliation(s)
- Tie Li
- Division of Molecular Medicine, Harbor-UCLA Medical Center, David Geffen School of Medicine, University of California-Los Angeles, Torrance, California 90502-2006, USA
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39
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Du M, Beatty LG, Zhou W, Lew J, Schoenherr C, Weksberg R, Sadowski PD. Insulator and silencer sequences in the imprinted region of human chromosome 11p15.5. Hum Mol Genet 2003; 12:1927-39. [PMID: 12874112 DOI: 10.1093/hmg/ddg194] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The imprinting of the genes on human chromosome 11p15.5 is thought to be controlled by two imprinting control regions located in two differentially methylated CpG islands upstream of the H19 gene (H19 DMR) and in intron 10 of the KCNQ1 gene (KvDMR). We have examined sequences in the human 11p15.5 genomic imprinted region for the presence of insulators and silencers using a position- and enhancer-dependent stable transfection assay. We have confirmed the existence of insulators in H19 DMR and discovered two novel insulators in the IGF2 gene. We have also found two novel silencer sequences; one is located in KvDMR, a region that is thought to contain the promoter for the KCNQ1OT1 transcript, and another is in the CDKN1C gene. We have demonstrated binding of CTCF protein in vitro to all the insulator and silencer sequences that we have detected. We discuss the differences in the regulation of imprinting controlled by the two imprinting control regions in chromosome 11p.
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Affiliation(s)
- Minjie Du
- Department of Molecular and Medical Genetics, University of Toronto, Toronto, Ontario, Canada M5S 1A8
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40
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Lutz M, Burke LJ, LeFevre P, Myers FA, Thorne AW, Crane-Robinson C, Bonifer C, Filippova GN, Lobanenkov V, Renkawitz R. Thyroid hormone-regulated enhancer blocking: cooperation of CTCF and thyroid hormone receptor. EMBO J 2003; 22:1579-87. [PMID: 12660164 PMCID: PMC152892 DOI: 10.1093/emboj/cdg147] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The highly conserved, ubiquitously expressed, zinc finger protein CTCF is involved in enhancer blocking, a mechanism crucial for shielding genes from illegitimate enhancer effects. Interestingly, CTCF-binding sites are often flanked by thyroid hormone response elements (TREs), as at the chicken lysozyme upstream silencer. Here we identify a similar composite site positioned upstream of the human c-myc gene. For both elements, we demonstrate that thyroid hormone abrogates enhancer blocking. Relief of enhancer blocking occurs even though CTCF remains bound to the lysozyme chromatin. Furthermore, chromatin immunoprecipitation analysis of the lysozyme upstream region revealed that histone H4 is acetylated at the CTCF-binding site. Loss of enhancer blocking by the addition of T3 led to increased histone acetylation, not only at the CTCF site, but also at the enhancer and the promoter. Thus, when TREs are adjacent to CTCF-binding sites, thyroid hormone can regulate enhancer blocking, thereby providing a new property for what was previously thought to be constitutive enhancer shielding by CTCF.
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Affiliation(s)
- Marcus Lutz
- Institute for Genetics, Justus-Liebig-Universitaet Giessen, Heinrich-Buff-Ring 58-62, D-35392 Giessen, Germany
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41
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Dostert A, Heinzel T. DNA-dependent cofactor selectivity of the glucocorticoid receptor. ERNST SCHERING RESEARCH FOUNDATION WORKSHOP 2003:279-95. [PMID: 12355721 DOI: 10.1007/978-3-662-04660-9_15] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- A Dostert
- Chemotherapeutisches Forschungsinstitut, Georg-Speyer-Haus, Paul-Ehrlich-Str. 42-44, 60594 Frankfurt/Main, Germany.
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42
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Burke LJ, Zhang R, Lutz M, Renkawitz R. The thyroid hormone receptor and the insulator protein CTCF: two different factors with overlapping functions. J Steroid Biochem Mol Biol 2002; 83:49-57. [PMID: 12650701 DOI: 10.1016/s0960-0760(02)00256-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Thyroid hormones and thyroid hormone receptors (TRs) confer a fundamental regulation of critical genes involved in metabolism, differentiation, and development. A similar role is attributed to the highly conserved zinc-finger factor CTCF. Furthermore, a potential role in tumour suppression has been attributed to CTCF. In addition to promoter regulation, CTCF has also been shown to be involved in chromatin insulation or enhancer blocking. In several cases, binding sites for TR and for CTCF have been found next to each other. Functionally, these sites mediate synergistic repression or induction dependent on the type of binding site and on the presence or absence of thyroid hormone. Here we discuss functional similarities between TR and CTCF and their roles within these composite elements.
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Affiliation(s)
- L J Burke
- Institute for Genetics, Justus-Liebig-Universitaet Giessen, Heinrich-Buff-Ring 58-62, D-35392 Giessen, Germany.
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43
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Klenova EM, Morse HC, Ohlsson R, Lobanenkov VV. The novel BORIS + CTCF gene family is uniquely involved in the epigenetics of normal biology and cancer. Semin Cancer Biol 2002; 12:399-414. [PMID: 12191639 DOI: 10.1016/s1044-579x(02)00060-3] [Citation(s) in RCA: 205] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
CTCF is a ubiquitous 11 zinc finger (ZF) protein with highly versatile functions: in addition to transcriptional silencing or activating in a context-dependent fashion, it organizes epigenetically controlled chromatin insulators that regulate imprinted genes in soma. Recently, we have identified a CTCF paralogue, termed BORIS for Brother of the Regulator of Imprinted Sites, that is expressed only in the testis. BORIS has the same exons encoding the 11 ZF domain as mammalian CTCF genes, and hence interacts with similar cis elements, but encodes amino and carboxy termini distinct from those in CTCF. Normally, CTCF and BORIS are expressed in a mutually exclusive pattern that correlates with re-setting of methylation marks during male germ cell differentiation. The antagonistic features of these two gene siblings are underscored by showing that while CTCF overexpression blocks cell proliferation, expression of BORIS in normally BORIS-negative cells promotes cell growth which can lead to transformation. The suggestion that BORIS directs epigenetic reprogramming at CTCF target sites impinges on the observations that human BORIS is not only abnormally activated in a wide range of human cancers, but also maps to the cancer-associated amplification region at 20q13. The sibling rivalry occasioned by aberrant expression of BORIS in cancer may interfere with normal functions of CTCF including growth suppression, and contribute to epigenetic dysregulation which is a common feature in human cancer.
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Affiliation(s)
- Elena M Klenova
- Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester CQ4 3SQ, UK
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44
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Loukinov DI, Pugacheva E, Vatolin S, Pack SD, Moon H, Chernukhin I, Mannan P, Larsson E, Kanduri C, Vostrov AA, Cui H, Niemitz EL, Rasko JEJ, Docquier FM, Kistler M, Breen JJ, Zhuang Z, Quitschke WW, Renkawitz R, Klenova EM, Feinberg AP, Ohlsson R, Morse HC, Lobanenkov VV. BORIS, a novel male germ-line-specific protein associated with epigenetic reprogramming events, shares the same 11-zinc-finger domain with CTCF, the insulator protein involved in reading imprinting marks in the soma. Proc Natl Acad Sci U S A 2002; 99:6806-11. [PMID: 12011441 PMCID: PMC124484 DOI: 10.1073/pnas.092123699] [Citation(s) in RCA: 262] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
CTCF, a conserved, ubiquitous, and highly versatile 11-zinc-finger factor involved in various aspects of gene regulation, forms methylation-sensitive insulators that regulate X chromosome inactivation and expression of imprinted genes. We document here the existence of a paralogous gene with the same exons encoding the 11-zinc-finger domain as mammalian CTCF genes and thus the same DNA-binding potential, but with distinct amino and carboxy termini. We named this gene BORIS for Brother of the Regulator of Imprinted Sites. BORIS is present only in the testis, and expressed in a mutually exclusive manner with CTCF during male germ cell development. We show here that erasure of methylation marks during male germ-line development is associated with dramatic up-regulation of BORIS and down-regulation of CTCF expression. Because BORIS bears the same DNA-binding domain that CTCF employs for recognition of methylation marks in soma, BORIS is a candidate protein for the elusive epigenetic reprogramming factor acting in the male germ line.
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Affiliation(s)
- Dmitri I Loukinov
- Laboratory of Immunopathology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892-0760, USA
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45
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Vostrov AA, Taheny MJ, Quitschke WW. A region to the N-terminal side of the CTCF zinc finger domain is essential for activating transcription from the amyloid precursor protein promoter. J Biol Chem 2002; 277:1619-27. [PMID: 11706010 DOI: 10.1074/jbc.m109748200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Transcription from the amyloid precursor protein (APP) promoter is largely dependent on a nuclear factor binding site designated as APBbeta. The protein that binds to this site is the multifunctional transcription factor CTCF, which consists of 727 amino acids and contains a domain of 11 zinc finger motifs that is flanked by 267 amino acids on the N-terminal side and 150 amino acids on the C-terminal side. Depleting HeLa cell nuclear extract of endogenous CTCF specifically reduced transcriptional activity from the APP promoter. However, transcriptional activity was restored by replenishing the depleted extract with recombinant CTCF. Deleting 201 amino acids from the C-terminal end of CTCF had no detrimental effect on transcriptional activation, whereas deleting either 248 or 284 amino acids from the N-terminal end abolished transcriptional activation. Competing endogenous CTCF in vivo was accomplished by cotransfecting COS-1 cells with a plasmid overexpressing CTCF constructs and a reporter plasmid containing the APP promoter. Under these conditions, an N-terminal deletion of CTCF reduced expression from the APP promoter, whereas the C-terminal deletion had no effect. These results demonstrate that CTCF activates transcription from the APP promoter and that the activation domain is located on the N-terminal side of the zinc finger domain.
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Affiliation(s)
- Alexander A Vostrov
- Department of Psychiatry and Behavioral Science, State University of New York, Stony Brook, New York 11794-8101, USA
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46
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Ohlsson R, Renkawitz R, Lobanenkov V. CTCF is a uniquely versatile transcription regulator linked to epigenetics and disease. Trends Genet 2001; 17:520-7. [PMID: 11525835 DOI: 10.1016/s0168-9525(01)02366-6] [Citation(s) in RCA: 471] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
CTCF is an evolutionarily conserved zinc finger (ZF) phosphoprotein that binds through combinatorial use of its 11 ZFs to approximately 50 bp target sites that have remarkable sequence variation. Formation of different CTCF-DNA complexes, some of which are methylation-sensitive, results in distinct functions, including gene activation, repression, silencing and chromatin insulation. Disrupting the spectrum of target specificities by ZF mutations or by abnormal selective methylation of targets is associated with cancer. CTCF emerges, therefore, as a central player in networks linking expression domains with epigenetics and cell growth regulation.
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Affiliation(s)
- R Ohlsson
- Dept of Genetics and Development, Evolution Biology Centre, Uppsala University, Norbyvägen 18A, S-752 36 Uppsala, Sweden.
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Filippova GN, Thienes CP, Penn BH, Cho DH, Hu YJ, Moore JM, Klesert TR, Lobanenkov VV, Tapscott SJ. CTCF-binding sites flank CTG/CAG repeats and form a methylation-sensitive insulator at the DM1 locus. Nat Genet 2001; 28:335-43. [PMID: 11479593 DOI: 10.1038/ng570] [Citation(s) in RCA: 232] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
An expansion of a CTG repeat at the DM1 locus causes myotonic dystrophy (DM) by altering the expression of the two adjacent genes, DMPK and SIX5, and through a toxic effect of the repeat-containing RNA. Here we identify two CTCF-binding sites that flank the CTG repeat and form an insulator element between DMPK and SIX5. Methylation of these sites prevents binding of CTCF, indicating that the DM1 locus methylation in congenital DM would disrupt insulator function. Furthermore, CTCF-binding sites are associated with CTG/CAG repeats at several other loci. We suggest a general role for CTG/CAG repeats as components of insulator elements at multiple sites in the human genome.
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Affiliation(s)
- G N Filippova
- Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA
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48
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Reed MR, Huang CF, Riggs AD, Mann JR. A complex duplication created by gene targeting at the imprinted H19 locus results in two classes of methylation and correlated Igf2 expression phenotypes. Genomics 2001; 74:186-96. [PMID: 11386755 DOI: 10.1006/geno.2001.6520] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Imprinting of the mouse H19 and Igf2 genes is dependent on the presence of an intervening imprinting control region (ICR) situated 2 kb upstream of H19 and approximately 70 kb downstream of Igf2. Several recent studies have provided substantial evidence that the unmethylated maternal ICR acts as an insulator that prevents activation of Igf2 by a suite of enhancers downstream of the H19 gene. The methylated paternal ICR and H19 promoter have no activity, allowing sole activation of Igf2 expression. We have produced mice in which a duplication of the H19/Igf2 ICR produces, in each generation, two classes of methylation levels that correlated with two Igf2 imprinting phenotypes. One hypermethylated class also shows activation of the normally silent Igf2 gene, whereas the other hypomethylated class shows only slight activation of Igf2, in agreement with methylation's role in ICR function. This study describes a rare, possibly unique type of mutation that induces two distinct phenotypes in each generation.
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Affiliation(s)
- M R Reed
- Division of Biology, Beckman Research Institute of the City of Hope, 1450 E. Duarte Road, Duarte, California 91010-3011, USA
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Klenova EM, Chernukhin IV, El-Kady A, Lee RE, Pugacheva EM, Loukinov DI, Goodwin GH, Delgado D, Filippova GN, León J, Morse HC, Neiman PE, Lobanenkov VV. Functional phosphorylation sites in the C-terminal region of the multivalent multifunctional transcriptional factor CTCF. Mol Cell Biol 2001; 21:2221-34. [PMID: 11238955 PMCID: PMC86856 DOI: 10.1128/mcb.21.6.2221-2234.2001] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
CTCF is a widely expressed and highly conserved multi-Zn-finger (ZF) nuclear factor. Binding to various CTCF target sites (CTSs) is mediated by combinatorial contributions of different ZFs. Different CTSs mediate distinct CTCF functions in transcriptional regulation, including promoter repression or activation and hormone-responsive gene silencing. In addition, the necessary and sufficient core sequences of diverse enhancer-blocking (insulator) elements, including CpG methylation-sensitive ones, have recently been pinpointed to CTSs. To determine whether a posttranslational modification may modulate CTCF functions, we studied CTCF phosphorylation. We demonstrated that most of the modifications that occur at the carboxy terminus in vivo can be reproduced in vitro with casein kinase II (CKII). Major modification sites map to four serines within the S(604)KKEDS(609)S(610)DS(612)E motif that is highly conserved in vertebrates. Specific mutations of these serines abrogate phosphorylation of CTCF in vivo and CKII-induced phosphorylation in vitro. In addition, we showed that completely preventing phosphorylation by substituting all serines within this site resulted in markedly enhanced repression of the CTS-bearing vertebrate c-myc promoters, but did not alter CTCF nuclear localization or in vitro DNA-binding characteristics assayed with c-myc CTSs. Moreover, these substitutions manifested a profound effect on negative cell growth regulation by wild-type CTCF. CKII may thus be responsible for attenuation of CTCF activity, either acting on its own or by providing the signal for phosphorylation by other kinases and for CTCF-interacting protein partners.
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Affiliation(s)
- E M Klenova
- Genetics Laboratory, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
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Pombo PM, Barettino D, Espliguero G, Metsis M, Iglesias T, Rodriguez-Pena A. Transcriptional repression of neurotrophin receptor trkB by thyroid hormone in the developing rat brain. J Biol Chem 2000; 275:37510-7. [PMID: 10978336 DOI: 10.1074/jbc.m006440200] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Expression of the neurotrophin receptor trkB is regulated by thyroid hormone (T3) during development of the rat brain. trkB mRNA levels, coding for the full-length and the truncated isoforms, are increased in the cerebral cortex of neonatal experimental hypothyroid animals. Run-on transcription assays with nuclei from postnatal day 15, hypothyroid, and control cerebral cortices demonstrated that an increase in the transcription rate of the trkB gene accounts for the observed effect. Transient transfection experiments using a reporter plasmid containing a 7-kilobase pair DNA fragment upstream of the mouse trkB gene showed that unliganded thyroid hormone receptor (T3R) increases promoter activity, whereas addition of T3 reverses that activity below basal levels. Deletion analysis shows that the T3-dependent repression requires binding of the T3R to a specific region located downstream of the transcription start site. This region, at nucleotide position -465/-432, contains an array of thyroid hormone response half-sites that bind preferentially T3R as heterodimers with retinoid X receptor and whose deletion causes loss of the T3-dependent repression. These half-sites are able to confer negative regulation by T3 to a heterologous promoter, thus indicating the functionality of these sequences. These results demonstrate that, in the developing rat brain, T3 down-regulates the expression of the trkB gene through the active repression of a novel negative response element located downstream of its transcription initiation site.
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Affiliation(s)
- P M Pombo
- Instituto de Investigaciones Biomédicas "Alberto Sols," Consejo Superior Investigaciones Cientificas and Universidad Autónoma de Madrid, 28029 Madrid, Spain
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