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Dean A. In the loop: long range chromatin interactions and gene regulation. Brief Funct Genomics 2011; 10:3-10. [PMID: 21258045 DOI: 10.1093/bfgp/elq033] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Enhancers, silencer and insulators are DNA elements that play central roles in regulation of the genome that are crucial for development and differentiation. In metazoans, these elements are often separated from target genes by distances that can reach 100 Kb. How regulation can be accomplished over long distances has long been intriguing. Current data indicate that although the mechanisms by which these diverse regulatory elements affect gene transcription may vary, an underlying feature is the establishment of close contacts or chromatin loops. With the generalization of this principle, new questions emerge, such as how the close contacts are formed and stabilized and, importantly, how they contribute to the regulation of transcriptional output at target genes. This review will concentrate on examples where a functional role and a mechanistic understanding has been explored for loops formed between genes and their regulatory elements or among the elements themselves.
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Affiliation(s)
- Ann Dean
- Laboratory of Cellular and Developmental Biology, NIDDK, NIH, Building 50, Room 3154, 50 South Drive, MSC 8028, Bethesda, MD 20892, USA.
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102
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Wicks K, Knight JC. Transcriptional repression and DNA looping associated with a novel regulatory element in the final exon of the lymphotoxin-β gene. Genes Immun 2011; 12:126-35. [PMID: 21248773 PMCID: PMC3049238 DOI: 10.1038/gene.2010.62] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Transcriptional regulation has a critical role in the coordinate and context-specific expression of a cluster of genes encoding members of the tumour necrosis factor (TNF) superfamily found at chromosome 6p21, comprising TNF, LTA (encoding lymphotoxin-α) and LTB (encoding lymphotoxin-β). This is important, as dysregulated expression of these genes is implicated in susceptibility to many autoimmune, inflammatory and infectious diseases. We describe here a novel regulatory element in the fourth exon of LTB, which is highly conserved, localises to the only CpG island in the locus, and is associated with a DNase I hypersensitive site and specific histone modifications. We find evidence of binding by Yin Yang 1 (YY1), cyclic AMP response element (CRE)-binding protein (CREB) and CCCTC-binding factor (CTCF) to this region in Jurkat T cells, which is associated with transcriptional repression on reporter gene analysis. Chromatin conformation capture experiments show evidence of DNA looping, involving interaction of this element with the LTB promoter, LTA promoter and TNF 3′ untranslated region (UTR). Small interfering RNA (siRNA) experiments demonstrate a functional role for YY1 and CREB in LTB expression. Our findings provide evidence of additional complexity in the transcriptional regulation of LTB with implications for coordinate expression of genes in this important genomic locus.
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Affiliation(s)
- K Wicks
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
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103
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Ling JQ, Hou A, Hoffman AR. Long-range DNA interactions are specifically altered by locked nucleic acid-targeting of a CTCF binding site. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2010; 1809:24-33. [PMID: 21111075 DOI: 10.1016/j.bbagrm.2010.11.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2010] [Revised: 11/10/2010] [Accepted: 11/15/2010] [Indexed: 01/21/2023]
Abstract
Long-range DNA interactions play an important role in gene expression. CCCTC-binding factor (CTCF), a ubiquitously expressed and evolutionarily conserved 11-zinc-finger DNA binding protein, is intimately involved in gene regulation, helping to establish and maintain chromatin architecture and long-range DNA interactions. In order to study the effects of manipulating long range chromatin interactions in the regulation of the neurofibromatosis gene NF1, we targeted Zorro locked nucleic acids (Zorro LNA) to a single CTCF binding site at an NF1 locus in human fibroblast cells. Using chromatin immunoprecipitation, we determined that this Zorro LNA altered CTCF and RNA polymerase II binding at three separate and distinct regions in the NF1 gene. This change in protein binding was associated with changes in long-range DNA interactions at the NF1 locus and downregulation of NF1 gene expression. This study describes an efficient and convenient method to manipulate chromatin structure and alter gene expression that is regulated by long-range DNA interactions without changing the DNA sequence. The use of specific Zorro LNA probes may facilitate our efforts to understand the interactions between chromatin architecture and gene expression.
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Affiliation(s)
- Jian Qun Ling
- Medical Service, VA Palo Alto Health Care System and Department of Medicine, Stanford University School of Medicine, Palo Alto, CA 94304, USA
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104
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NPM1/B23: A Multifunctional Chaperone in Ribosome Biogenesis and Chromatin Remodeling. Biochem Res Int 2010; 2011:195209. [PMID: 21152184 PMCID: PMC2989734 DOI: 10.1155/2011/195209] [Citation(s) in RCA: 226] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Accepted: 08/29/2010] [Indexed: 12/21/2022] Open
Abstract
At a first glance, ribosome biogenesis and chromatin remodeling are quite different processes, but they share a common problem involving interactions between charged nucleic acids and small basic proteins that may result in unwanted intracellular aggregations. The multifunctional nuclear acidic chaperone NPM1 (B23/nucleophosmin) is active in several stages of ribosome biogenesis, chromatin remodeling, and mitosis as well as in DNA repair, replication and transcription. In addition, NPM1 plays an important role in the Myc-ARF-p53 pathway as well as in SUMO regulation. However, the relative importance of NPM1 in these processes remains unclear. Provided herein is an update on the expanding list of the diverse activities and interacting partners of NPM1. Mechanisms of NPM1 nuclear export functions of NPM1 in the nucleolus and at the mitotic spindle are discussed in relation to tumor development. It is argued that the suggested function of NPM1 as a histone chaperone could explain several, but not all, of the effects observed in cells following changes in NPM1 expression. A future challenge is to understand how NPM1 is activated, recruited, and controlled to carry out its functions.
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105
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Rocquain J, Gelsi-Boyer V, Adélaïde J, Murati A, Carbuccia N, Vey N, Birnbaum D, Mozziconacci MJ, Chaffanet M. Alteration of cohesin genes in myeloid diseases. Am J Hematol 2010; 85:717-9. [PMID: 20687102 DOI: 10.1002/ajh.21798] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
New genes involved in leukemogenesis, such as ASXL1 and TET2, have been identified recently using genomic analyses of DNA from patient samples. We have studied by array-comparative genomic hybridization (aCGH) a series of 167 samples including myelodysplastic syndromes, chronic myelomonocytic leukemias, and acute myeloid leukemias. We found a deletion of the RAD21 and STAG2 genes, which encode two components of the cohesin complex. We propose that these alterations may compromise the cohesin complex and its regulation of the transcription of genes.
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106
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Abstract
The human CCCTC-binding factor, CTCF, organizes and regulates transcription of the genome by colocalizing distant DNA elements on the same and even different chromosomes. This protein consists of 11 zinc fingers flanked by polypeptide segments of unknown structure and function. We purified recombinant terminal fragments and observed that both are extended, monomeric, and predominantly consist of unordered content. We thus speculate that the role of the terminal extensions, and perhaps all of CTCF, is to act as a scaffold for the assembly of other proteins on a specific binding site.
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Affiliation(s)
- Selena R Martinez
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, USA
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107
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The ratio of SRPK1/SRPK1a regulates erythroid differentiation in K562 leukaemic cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2010; 1803:1319-31. [PMID: 20708644 DOI: 10.1016/j.bbamcr.2010.07.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2009] [Revised: 07/19/2010] [Accepted: 07/26/2010] [Indexed: 11/22/2022]
Abstract
SRPK1, the prototype of the serine/arginine family of kinases, has been implicated in the regulation of multiple cellular processes such as pre-mRNA splicing, chromatin structure, nuclear import and germ cell development. SRPK1a is a much less studied isoform of SRPK1 that contains an extended N-terminal domain and so far has only been detected in human testis. In the present study we show that SRPK1 is the predominant isoform in K562 cells, with the ratio of the two isoforms being critical in determining cell fate. Stable overexpression of SRPK1a induces erythroid differentiation of K562 cells. The induction of globin synthesis was accompanied by a marked decrease in proliferation and a significantly reduced clonogenic potential. Small interfering RNA-mediated down-regulation of SRPK1 in K562 cells results similarly in a decrease in proliferative capacity and induction of globin synthesis. A decreased SRPK1/SRPK1a ratio is also observed upon hemin/DMSO-induced differentiation of K562 cells as well as in normal human erythroid progenitor cells. Mass spectrometric analysis of SRPK1a-associated proteins identified multiple classes of RNA-binding proteins including RNA helicases, heterogeneous nuclear ribonucleoproteins, ribosomal proteins, and mRNA-associated proteins. Several of the SRPK1a-copurifying proteins have been previously identified in ribosomal and pre-ribosomal complexes, thereby suggesting that SRPK1a may play an important role in linking ribosomal assembly and/or function to erythroid differentiation in human leukaemic cells.
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108
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Raab JR, Kamakaka RT. Insulators and promoters: closer than we think. Nat Rev Genet 2010; 11:439-46. [PMID: 20442713 DOI: 10.1038/nrg2765] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Insulators prevent promiscuous gene regulation by restricting the action of enhancers and silencers. Recent studies have revealed a number of similarities between insulators and promoters, including binding of specific transcription factors, chromatin-modification signatures and localization to specific subnuclear positions. We propose that enhancer-blockers and silencing barrier-insulators might have evolved as specialized derivatives of promoters and that the two types of element use related mechanisms to mediate their distinct functions. These insights can help to reconcile different models of insulator action.
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Affiliation(s)
- Jesse R Raab
- Department of Molecular Cell and Developmental Biology, Sinsheimer Labs, University of California, Santa Cruz, California 95064, USA
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109
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Modular insulators: genome wide search for composite CTCF/thyroid hormone receptor binding sites. PLoS One 2010; 5:e10119. [PMID: 20404925 PMCID: PMC2852416 DOI: 10.1371/journal.pone.0010119] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2009] [Accepted: 03/18/2010] [Indexed: 02/07/2023] Open
Abstract
The conserved 11 zinc-finger protein CTCF is involved in several transcriptional mechanisms, including insulation and enhancer blocking. We had previously identified two composite elements consisting of a CTCF and a TR binding site at the chicken lysozyme and the human c-myc genes. Using these it has been demonstrated that thyroid hormone mediates the relief of enhancer blocking even though CTCF remains bound to its binding site. Here we wished to determine whether CTCF and TR combined sites are representative of a general feature of the genome, and whether such sites are functional in regulating enhancer blocking. Genome wide analysis revealed that about 18% of the CTCF regions harbored at least one of the four different palindromic or repeated sequence arrangements typical for the binding of TR homodimers or TR/RXR heterodimers. Functional analysis of 10 different composite elements of thyroid hormone responsive genes was performed using episomal constructs. The episomal system allowed recapitulating CTCF mediated enhancer blocking function to be dependent on poly (ADP)-ribose modification and to mediate histone deacetylation. Furthermore, thyroid hormone sensitive enhancer blocking could be shown for one of these new composite elements. Remarkably, not only did the regulation of enhancer blocking require functional TR binding, but also the basal enhancer blocking activity of CTCF was dependent on the binding of the unliganded TR. Thus, a number of composite CTCF/TR binding sites may represent a subset of other modular CTCF composite sites, such as groups of multiple CTCF sites or of CTCF/Oct4, CTCF/Kaiso or CTCF/Yy1 combinations.
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110
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Abstract
Chromatin interactions, both in cis and trans and between transcriptionally active and silent regions, mean that the spatial organization of the genome is non-random. Spatial organization of the genome is non-random. Preferential chromatin interactions, both in cis and in trans and between transcriptionally active and silent regions, influence organization.
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Affiliation(s)
- Nathan F Cope
- Laboratory of Chromatin and Gene Expression, The Babraham Institute, Babraham Research Campus, Cambridge, UK
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111
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Meyer MB, Goetsch PD, Pike JW. A downstream intergenic cluster of regulatory enhancers contributes to the induction of CYP24A1 expression by 1alpha,25-dihydroxyvitamin D3. J Biol Chem 2010; 285:15599-15610. [PMID: 20236932 DOI: 10.1074/jbc.m110.119958] [Citation(s) in RCA: 117] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
CYP24A1 expression is up-regulated by 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) via a vitamin D receptor (VDR)/retinoid X receptor (RXR) heterodimer that binds to two vitamin D response elements (VDREs) located near the proximal promoter. Interestingly, although 1,25(OH)(2)D(3) induced VDR/RXR binding to the VDRE-containing proximal promoter, the VDR/RXR heterodimer also localized to a cluster of at least four potential enhancers located in intergenic regions 50-69 kb downstream of the human CYP24A1 gene and 35-45 kb downstream of the mouse Cyp24a1 gene as revealed by ChIP-chip and ChIP-seq analyses. To address whether this downstream region and potential VDREs located within mediated CYP24A1 induction, we constructed recombinant wild-type and mutant bacterial artificial chromosome clones that spanned mouse and human loci and contained luciferase reporters inserted into their 3'-untranslated regions. The activity of these clones in stably transfected cells revealed that both the proximal and the putative downstream elements contributed to CYP24A1 up-regulation by 1,25(OH)(2)D(3). Further analysis using transfected enhancer fragments led to the identification of contributing regulatory elements in several of these downstream regions. Additional studies of coregulator recruitment using ChIP-chip analysis revealed both similarities and differences between the region located proximal to and those located downstream of the promoter. Recruitment of these coregulators was likely responsible for the increase in RNA polymerase II and histone H4 acetylation, which was also observed in response to 1,25(OH)(2)D(3) at the enhancer sites across the locus. We conclude that a more complex mechanism is responsible for the striking CYP24A1 up-regulation induced by the vitamin D hormone in target cells.
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Affiliation(s)
- Mark B Meyer
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706
| | - Paul D Goetsch
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706
| | - J Wesley Pike
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706.
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112
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Expression of a testis-specific form of Gal3st1 (CST), a gene essential for spermatogenesis, is regulated by the CTCF paralogous gene BORIS. Mol Cell Biol 2010; 30:2473-84. [PMID: 20231363 DOI: 10.1128/mcb.01093-09] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Previously, it was shown that the CTCF paralogous gene, BORIS (brother of the regulator of imprinted sites) is expressed in male germ cells, but its function in spermatogenesis has not been defined. To develop an understanding of the functional activities of BORIS, we generated BORIS knockout (KO) mice. Mice homozygous for the null allele had a defect in spermatogenesis that resulted in small testes associated with increased cell death. The defect was evident as early as postnatal day 21 and was manifested by delayed production of haploid cells. By gene expression profiling, we found that transcript levels for Gal3st1 (also known as cerebroside sulfotransferase [CST]), known to play a crucial role in meiosis, were dramatically reduced in BORIS KO testes. We found that CST is expressed in testis as a novel testis-specific isoform, CST form F(TS), that has a short exon 1f. We showed that BORIS bound to and activated the promoter of CST form F(TS). Mutation of the BORIS binding site in the promoter reduced the ability of BORIS to activate the promoter. These findings define transcriptional regulation of CST expression as a critical role for BORIS in spermatogenesis.
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113
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Díaz-Martínez LA, Yu H. Cohesin: a multi-purpose chromatin glue. J Mol Cell Biol 2009; 1:58-60. [PMID: 19684050 DOI: 10.1093/jmcb/mjp014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Long thought to be the glue responsible for holding sister chromatids together, cohesin has been found to be stickier than previously thought. Recent discoveries point to cohesin having a role in transcription regulation by mediating long-distance intra-chromosomal interactions.
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Affiliation(s)
- Laura A Díaz-Martínez
- Department of Pharmacology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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114
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Essien K, Vigneau S, Apreleva S, Singh LN, Bartolomei MS, Hannenhalli S. CTCF binding site classes exhibit distinct evolutionary, genomic, epigenomic and transcriptomic features. Genome Biol 2009; 10:R131. [PMID: 19922652 PMCID: PMC3091324 DOI: 10.1186/gb-2009-10-11-r131] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2009] [Accepted: 11/18/2009] [Indexed: 11/18/2022] Open
Abstract
CTCF DNA binding sites are classified into distinct functional classes, with distinct biological properties, shedding light on the differing functional roles of CTCF binding. Background CTCF (CCCTC-binding factor) is an evolutionarily conserved zinc finger protein involved in diverse functions ranging from negative regulation of MYC, to chromatin insulation of the beta-globin gene cluster, to imprinting of the Igf2 locus. The 11 zinc fingers of CTCF are known to differentially contribute to the CTCF-DNA interaction at different binding sites. It is possible that the differences in CTCF-DNA conformation at different binding sites underlie CTCF's functional diversity. If so, the CTCF binding sites may belong to distinct classes, each compatible with a specific functional role. Results We have classified approximately 26,000 CTCF binding sites in CD4+ T cells into three classes based on their similarity to the well-characterized CTCF DNA-binding motif. We have comprehensively characterized these three classes of CTCF sites with respect to several evolutionary, genomic, epigenomic, transcriptomic and functional features. We find that the low-occupancy sites tend to be cell type specific. Furthermore, while the high-occupancy sites associate with repressive histone marks and greater gene co-expression within a CTCF-flanked block, the low-occupancy sites associate with active histone marks and higher gene expression. We found that the low-occupancy sites have greater conservation in their flanking regions compared to high-occupancy sites. Interestingly, based on a novel class-conservation metric, we observed that human low-occupancy sites tend to be conserved as low-occupancy sites in mouse (and vice versa) more frequently than expected. Conclusions Our work reveals several key differences among CTCF occupancy-based classes and suggests a critical, yet distinct functional role played by low-occupancy sites.
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Affiliation(s)
- Kobby Essien
- Penn Center for Bioinformatics, Department of Genetics, 415 Curie Boulevard, University of Pennsylvania, Philadelphia, PA 19104, USA.
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115
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Heger P, Marin B, Schierenberg E. Loss of the insulator protein CTCF during nematode evolution. BMC Mol Biol 2009; 10:84. [PMID: 19712444 PMCID: PMC2749850 DOI: 10.1186/1471-2199-10-84] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2009] [Accepted: 08/27/2009] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The zinc finger (ZF) protein CTCF (CCCTC-binding factor) is highly conserved in Drosophila and vertebrates where it has been shown to mediate chromatin insulation at a genomewide level. A mode of genetic regulation that involves insulators and insulator binding proteins to establish independent transcriptional units is currently not known in nematodes including Caenorhabditis elegans. We therefore searched in nematodes for orthologs of proteins that are involved in chromatin insulation. RESULTS While orthologs for other insulator proteins were absent in all 35 analysed nematode species, we find orthologs of CTCF in a subset of nematodes. As an example for these we cloned the Trichinella spiralis CTCF-like gene and revealed a genomic structure very similar to the Drosophila counterpart. To investigate the pattern of CTCF occurrence in nematodes, we performed phylogenetic analysis with the ZF protein sets of completely sequenced nematodes. We show that three ZF proteins from three basal nematodes cluster together with known CTCF proteins whereas no zinc finger protein of C. elegans and other derived nematodes does so. CONCLUSION Our findings show that CTCF and possibly chromatin insulation are present in basal nematodes. We suggest that the insulator protein CTCF has been secondarily lost in derived nematodes like C. elegans. We propose a switch in the regulation of gene expression during nematode evolution, from the common vertebrate and insect type involving distantly acting regulatory elements and chromatin insulation to a so far poorly characterised mode present in more derived nematodes. Here, all or some of these components are missing. Instead operons, polycistronic transcriptional units common in derived nematodes, seemingly adopted their function.
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Affiliation(s)
- Peter Heger
- Zoological Institute, University of Cologne, Kerpener Strasse 15, 50937 Köln, Germany.
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116
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Gombert WM, Krumm A. Targeted deletion of multiple CTCF-binding elements in the human C-MYC gene reveals a requirement for CTCF in C-MYC expression. PLoS One 2009; 4:e6109. [PMID: 19568426 PMCID: PMC2699473 DOI: 10.1371/journal.pone.0006109] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Accepted: 06/01/2009] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Insulators and domain boundaries both shield genes from adjacent enhancers and inhibit intrusion of heterochromatin into transgenes. Previous studies examined the functional mechanism of the MYC insulator element MINE and its CTCF binding sites in the context of transgenes that were randomly inserted into the genome by transfection. However, the contribution of CTCF binding sites to both gene regulation and maintenance of chromatin has not been tested at the endogenous MYC gene. METHODOLOGY/PRINCIPAL FINDINGS To determine the impact of CTCF binding on MYC expression, a series of mutant human chromosomal alleles was prepared in homologous recombination-efficient DT40 cells and individually transferred by microcell fusion into murine cells. Functional tests reported here reveal that deletion of CTCF binding elements within the MINE does not impact the capacity of this locus to correctly organize an 'accessible' open chromatin domain, suggesting that these sites are not essential for the formation of a competent, transcriptionally active locus. Moreover, deletion of the CTCF site at the MYC P2 promoter reduces transcription but does not affect promoter acetylation or serum-inducible transcription. Importantly, removal of either CTCF site leads to DNA methylation of flanking sequences, thereby contributing to progressive loss of transcriptional activity. CONCLUSIONS These findings collectively demonstrate that CTCF-binding at the human MYC locus does not repress transcriptional activity but is required for protection from DNA methylation.
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Affiliation(s)
- Wendy M. Gombert
- Black Lowe & Graham PLLC, Seattle, Washington, United States of America
| | - Anton Krumm
- Department of Radiation Oncology, University of Washington School of Medicine, Seattle, Washington, United States of America
- Institute for Stem Cell and Regenerative Medicine, University of Washington School of Medicine, Seattle, Washington, United States of America
- * E-mail:
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117
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Abstract
In a recent issue of Molecular Cell, Witcher and Emerson (2009) demonstrate that CTCF loss of function, via defective steps in poly (ADP-ribosyl)ation, may predispose key genes in cancer cells to addition of abnormal promoter DNA methylation and silencing.
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