1
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Alam P, Clovis NS, Chand AK, Khan MF, Sen S. Effect of molecular crowders on ligand binding kinetics with G-quadruplex DNA probed by fluorescence correlation spectroscopy. Methods Appl Fluoresc 2024; 12:045002. [PMID: 39013401 DOI: 10.1088/2050-6120/ad63f5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2024] [Accepted: 07/16/2024] [Indexed: 07/18/2024]
Abstract
Guanine-rich single-stranded DNA folds into G-quadruplex DNA (GqDNA) structures, which play crucial roles in various biological processes. These structures are also promising targets for ligands, potentially inducing antitumor effects. While thermodynamic parameters of ligand/DNA interactions are well-studied, the kinetics of ligand interaction with GqDNA, particularly in cell-like crowded environments, remain less explored. In this study, we investigate the impact of molecular crowding agents (glucose, sucrose, and ficoll 70) at physiologically relevant concentrations (20% w/v) on the association and dissociation rates of the benzophenoxazine-core based ligand, cresyl violet (CV), with human telomeric antiparallel-GqDNA. We utilized fluorescence correlation spectroscopy (FCS) along with other techniques. Our findings reveal that crowding agents decrease the binding affinity of CV to GqDNA, with the most significant effect-a nearly three-fold decrease-observed with ficoll 70. FCS measurements indicate that this decrease is primarily due to a viscosity-induced slowdown of ligand association in the crowded environment. Interestingly, dissociation rates remain largely unaffected by smaller crowders, with only small effect observed in presence of ficoll 70 due to direct but weak interaction between the ligand and ficoll. These results along with previously reported data provide valuable insights into ligand/GqDNA interactions in cellular contexts, suggesting a conserved mechanism of saccharide crowder influence, regardless of variations in GqDNA structure and ligand binding mode. This underscores the importance of considering crowding effects in the design and development of GqDNA-targeted drugs for potential cancer treatment.
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Affiliation(s)
- Parvez Alam
- Spectroscopy Laboratory, School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067, India
| | - Ndege Simisi Clovis
- Spectroscopy Laboratory, School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067, India
| | - Ajay Kumar Chand
- Spectroscopy Laboratory, School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067, India
| | - Mohammad Firoz Khan
- Spectroscopy Laboratory, School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067, India
| | - Sobhan Sen
- Spectroscopy Laboratory, School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067, India
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2
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Hussen AS, Kravitz HL, Freudenthal BD, Whitaker AM. Oxidative DNA damage on the VEGF G-quadruplex forming promoter is repaired via long-patch BER. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2024; 65 Suppl 1:25-39. [PMID: 37606505 PMCID: PMC10984112 DOI: 10.1002/em.22570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Revised: 08/01/2023] [Accepted: 08/20/2023] [Indexed: 08/23/2023]
Abstract
In response to oxidative damage, base excision repair (BER) enzymes perturb the structural equilibrium of the VEGF promoter between B-form and G4 DNA conformations, resulting in epigenetic-like modifications of gene expression. However, the mechanistic details remain enigmatic, including the activity and coordination of BER enzymes on the damaged G4 promoter. To address this, we investigated the ability of each BER factor to conduct its repair activity on VEGF promoter G4 DNA substrates by employing pre-steady-state kinetics assays and in vitro coupled BER assays. OGG1 was able to initiate BER on double-stranded VEGF promoter G4 DNA substrates. Moreover, pre-steady-state kinetics revealed that compared to B-form DNA, APE1 repair activity on the G4 was decreased ~two-fold and is the result of slower product release as opposed to inefficient strand cleavage. Interestingly, Pol β performs multiple insertions on G4 substrates via strand displacement DNA synthesis in contrast to a single insertion on B-form DNA. The multiple insertions inhibit ligation of the Pol β products, and hence BER is not completed on the VEGF G4 promoter substrates through canonical short-patch BER. Instead, repair requires the long-patch BER flap-endonuclease activity of FEN1 in response to the multiple insertions by Pol β prior to ligation. Because the BER proteins and their repair activities are a key part of the VEGF transcriptional enhancement in response to oxidative DNA damage of the G4 VEGF promoter, the new insights reported here on BER activity in the context of this promoter are relevant toward understanding the mechanism of transcriptional regulation.
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Affiliation(s)
- Adil S. Hussen
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, Kansas, USA
| | - Haley L. Kravitz
- Nuclear Dynamics and Cancer Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania, USA
| | - Bret D. Freudenthal
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, Kansas, USA
| | - Amy M. Whitaker
- Nuclear Dynamics and Cancer Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania, USA
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3
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Gumina JM, Richardson AE, Shojiv MH, Chambers AE, Sandwith SN, Reisinger MA, Karns TJ, Osborne TL, Alashi HN, Anderson QT, Sharlow ME, Seiler DC, Rogers EM, Bartosik AR, Smaldino MA, Vaughn JP, Wang YH, Smaldino PJ, Haney RA. Differential Gene Expression following DHX36/ G4R1 Knockout Is Associated with G-Quadruplex Content and Cancer. Int J Mol Sci 2024; 25:1753. [PMID: 38339029 PMCID: PMC10855491 DOI: 10.3390/ijms25031753] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Revised: 01/18/2024] [Accepted: 01/19/2024] [Indexed: 02/12/2024] Open
Abstract
G-quadruplexes (G4s) are secondary DNA and RNA structures stabilized by positive cations in a central channel formed by stacked tetrads of Hoogsteen base-paired guanines. G4s form from G-rich sequences across the genome, whose biased distribution in regulatory regions points towards a gene-regulatory role. G4s can themselves be regulated by helicases, such as DHX36 (aliases: G4R1 and RHAU), which possess the necessary activity to resolve these stable structures. G4s have been shown to both positively and negatively regulate gene expression when stabilized by ligands, or through the loss of helicase activity. Using DHX36 knockout Jurkat cell lines, we identified widespread, although often subtle, effects on gene expression that are associated with the presence or number of observed G-quadruplexes in promoters or gene regions. Genes that significantly change their expression, particularly those that show a significant increase in RNA abundance under DHX36 knockout, are associated with a range of cellular functions and processes, including numerous transcription factors and oncogenes, and are linked to several cancers. Our work highlights the direct and indirect role of DHX36 in the transcriptome of T-lymphocyte leukemia cells and the potential for DHX36 dysregulation in cancer.
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Affiliation(s)
- Joseph M. Gumina
- Department of Biology, Ball State University, Muncie, IN 47306, USA
| | | | | | | | | | | | - Taylor J. Karns
- Department of Biology, Ball State University, Muncie, IN 47306, USA
| | - Tyler L. Osborne
- Department of Biology, Ball State University, Muncie, IN 47306, USA
| | - Hasna N. Alashi
- Department of Biology, Ball State University, Muncie, IN 47306, USA
| | | | | | - Dylan C. Seiler
- Department of Biology, Ball State University, Muncie, IN 47306, USA
| | - Evan M. Rogers
- Department of Biology, Ball State University, Muncie, IN 47306, USA
| | - Anna R. Bartosik
- School of Medicine, University of Virginia, Charlottesville, VA 22908, USA
| | | | | | - Yuh-Hwa Wang
- School of Medicine, University of Virginia, Charlottesville, VA 22908, USA
| | | | - Robert A. Haney
- Department of Biology, Ball State University, Muncie, IN 47306, USA
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4
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Lee CSK, Weiβ M, Hamperl S. Where and when to start: Regulating DNA replication origin activity in eukaryotic genomes. Nucleus 2023; 14:2229642. [PMID: 37469113 PMCID: PMC10361152 DOI: 10.1080/19491034.2023.2229642] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 06/20/2023] [Accepted: 06/21/2023] [Indexed: 07/21/2023] Open
Abstract
In eukaryotic genomes, hundreds to thousands of potential start sites of DNA replication named origins are dispersed across each of the linear chromosomes. During S-phase, only a subset of origins is selected in a stochastic manner to assemble bidirectional replication forks and initiate DNA synthesis. Despite substantial progress in our understanding of this complex process, a comprehensive 'identity code' that defines origins based on specific nucleotide sequences, DNA structural features, the local chromatin environment, or 3D genome architecture is still missing. In this article, we review the genetic and epigenetic features of replication origins in yeast and metazoan chromosomes and highlight recent insights into how this flexibility in origin usage contributes to nuclear organization, cell growth, differentiation, and genome stability.
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Affiliation(s)
- Clare S K Lee
- Chromosome Dynamics and Genome Stability, Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München, Munich, Germany
| | - Matthias Weiβ
- Chromosome Dynamics and Genome Stability, Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München, Munich, Germany
| | - Stephan Hamperl
- Chromosome Dynamics and Genome Stability, Institute of Epigenetics and Stem Cells, Helmholtz Zentrum München, Munich, Germany
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5
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Pavlova I, Iudin M, Surdina A, Severov V, Varizhuk A. G-Quadruplexes in Nuclear Biomolecular Condensates. Genes (Basel) 2023; 14:genes14051076. [PMID: 37239436 DOI: 10.3390/genes14051076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 05/10/2023] [Accepted: 05/11/2023] [Indexed: 05/28/2023] Open
Abstract
G-quadruplexes (G4s) have long been implicated in the regulation of chromatin packaging and gene expression. These processes require or are accelerated by the separation of related proteins into liquid condensates on DNA/RNA matrices. While cytoplasmic G4s are acknowledged scaffolds of potentially pathogenic condensates, the possible contribution of G4s to phase transitions in the nucleus has only recently come to light. In this review, we summarize the growing evidence for the G4-dependent assembly of biomolecular condensates at telomeres and transcription initiation sites, as well as nucleoli, speckles, and paraspeckles. The limitations of the underlying assays and the remaining open questions are outlined. We also discuss the molecular basis for the apparent permissive role of G4s in the in vitro condensate assembly based on the interactome data. To highlight the prospects and risks of G4-targeting therapies with respect to the phase transitions, we also touch upon the reported effects of G4-stabilizing small molecules on nuclear biomolecular condensates.
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Affiliation(s)
- Iuliia Pavlova
- Lopukhin Federal Research and Clinical Center of Physical-Chemical Medicine, 119435 Moscow, Russia
- Moscow Institute of Physics and Technology, 141701 Dolgoprudny, Russia
| | - Mikhail Iudin
- Lopukhin Federal Research and Clinical Center of Physical-Chemical Medicine, 119435 Moscow, Russia
- Moscow Institute of Physics and Technology, 141701 Dolgoprudny, Russia
| | - Anastasiya Surdina
- Lopukhin Federal Research and Clinical Center of Physical-Chemical Medicine, 119435 Moscow, Russia
| | - Vjacheslav Severov
- Lopukhin Federal Research and Clinical Center of Physical-Chemical Medicine, 119435 Moscow, Russia
| | - Anna Varizhuk
- Lopukhin Federal Research and Clinical Center of Physical-Chemical Medicine, 119435 Moscow, Russia
- Moscow Institute of Physics and Technology, 141701 Dolgoprudny, Russia
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6
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Moreno SP, Fusté JM, Kaiser M, Li JSZ, Nassour J, Haggblom C, Denchi EL, Karlseder J. TZAP overexpression induces telomere dysfunction and ALT-like activity in ATRX/DAXX-deficient cells. iScience 2023; 26:106405. [PMID: 37013192 PMCID: PMC10066556 DOI: 10.1016/j.isci.2023.106405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2022] [Revised: 11/13/2022] [Accepted: 03/10/2023] [Indexed: 03/14/2023] Open
Abstract
The appropriate regulation of telomere length homeostasis is crucial for the maintenance of genome integrity. The telomere-binding protein TZAP has been suggested to regulate telomere length by promoting t-circle and c-circle excisions through telomere trimming, yet the molecular mechanisms by which TZAP functions at telomeres are not understood. Using a system based on TZAP overexpression, we show that efficient TZAP recruitment to telomeres occurs in the context of open telomeric chromatin caused by loss of ATRX/DAXX independently of H3.3 deposition. Moreover, our data indicate that TZAP binding to telomeres induces telomere dysfunction and ALT-like activity, resulting in the generation of t-circles and c-circles in a Bloom-Topoisomerase IIIα-RMI1-RMI2 (BTR)-dependent manner.
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Affiliation(s)
- Sara Priego Moreno
- The Salk Institute for Biological Studies, Molecular and Cell Biology Department, 10010 N. Torrey pines Road, La Jolla, CA 92037, USA
| | - Javier Miralles Fusté
- The Salk Institute for Biological Studies, Molecular and Cell Biology Department, 10010 N. Torrey pines Road, La Jolla, CA 92037, USA
| | - Melanie Kaiser
- The Salk Institute for Biological Studies, Molecular and Cell Biology Department, 10010 N. Torrey pines Road, La Jolla, CA 92037, USA
| | - Julia Su Zhou Li
- The Ludwig Institute for Cancer Research, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Joe Nassour
- The Salk Institute for Biological Studies, Molecular and Cell Biology Department, 10010 N. Torrey pines Road, La Jolla, CA 92037, USA
| | - Candy Haggblom
- The Salk Institute for Biological Studies, Molecular and Cell Biology Department, 10010 N. Torrey pines Road, La Jolla, CA 92037, USA
| | - Eros Lazzerini Denchi
- Laboratory for Genome Integrity, National Cancer Institute, Building 37, Room 2144B, Bethesda, MD 20892, USA
| | - Jan Karlseder
- The Salk Institute for Biological Studies, Molecular and Cell Biology Department, 10010 N. Torrey pines Road, La Jolla, CA 92037, USA
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7
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Pavlova I, Barinov N, Novikov R, Severov V, Iudin M, Vedekhina T, Larin A, Babenko V, Aralov A, Gnuchikh E, Sardushkin M, Klinov D, Tsvetkov V, Varizhuk A. Modeling G4s in chromatin context confirms partial nucleosome exclusion and reveals nucleosome-disrupting effects of the least selective G4 ligands. Biochimie 2023; 204:8-21. [PMID: 36063975 DOI: 10.1016/j.biochi.2022.08.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 07/22/2022] [Accepted: 08/23/2022] [Indexed: 01/12/2023]
Abstract
G-quadruplexes (G4s) are gaining increasing attention as possible regulators of chromatin packaging, and robust approaches to their studies in pseudo-native context are much needed. Here, we designed a simple in vitro model of G4-prone genomic DNA and employed it to elucidate the impact of G4s and G4-stabilizing ligands on nucleosome occupancy. We obtained two 226-bp dsDNA constructs composed of the strong nucleosome positioning sequence and an internucleosomal DNA-imitating tail. The tail was G4-free in the control construct and harbored a "strong" (stable) G4 motif in the construct of interest. An additional "weak" (semi-stable) G4 motif was found within the canonical nucleosome positioning sequence. Both G4s were confirmed by optical methods and 1H NMR spectroscopy. Electrophoretic mobility assays showed that the weak G4 motif did not obstruct nucleosome assembly, while the strong G4 motif in the tail sequence diminished nucleosome yield. Atomic force microscopy data and molecular modeling confirmed that the strong G4 was maintained in the tail of the correctly assembled nucleosome structure. Using both in vitro and in silico models, we probed three known G4 ligands and detected nucleosome-disrupting effects of the least selective ligand. Our results are in line with the negative correlation between stable G4s and nucleosome density, support G4 tolerance between regularly positioned nucleosomes, and highlight the importance of considering chromatin context when targeting genomic G4s.
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Affiliation(s)
- Iuliia Pavlova
- Federal Research and Clinical Center of Physical-Chemical Medicine, Moscow, 119435, Russia; Moscow Institute of Physics and Technology, Dolgoprudny, 141701, Russia
| | - Nikolay Barinov
- Federal Research and Clinical Center of Physical-Chemical Medicine, Moscow, 119435, Russia
| | - Roman Novikov
- Engenlhardt Institute of Molecular Biology, Moscow, 119991, Russia; N.D. Zelinsky Institute of Organic Chemistry, Moscow, 19991, Russia
| | - Vjacheslav Severov
- Federal Research and Clinical Center of Physical-Chemical Medicine, Moscow, 119435, Russia
| | - Mikhail Iudin
- Federal Research and Clinical Center of Physical-Chemical Medicine, Moscow, 119435, Russia; Moscow Institute of Physics and Technology, Dolgoprudny, 141701, Russia
| | - Tatiana Vedekhina
- Federal Research and Clinical Center of Physical-Chemical Medicine, Moscow, 119435, Russia
| | - Andrey Larin
- Federal Research and Clinical Center of Physical-Chemical Medicine, Moscow, 119435, Russia; Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Federal Research and Clinical Center of Physical-Chemical Medicine of Federal Medical Biological Agency, Moscow, 119435, Russia
| | - Vladislav Babenko
- Federal Research and Clinical Center of Physical-Chemical Medicine, Moscow, 119435, Russia; Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Federal Research and Clinical Center of Physical-Chemical Medicine of Federal Medical Biological Agency, Moscow, 119435, Russia
| | - Andrey Aralov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Moscow, 117997, Russia
| | - Evgeny Gnuchikh
- National Research Center Kurchatov Institute, Kurchatov Genomic Center, Moscow, 123182, Russia
| | - Makar Sardushkin
- Mendeleev University of Chemical Technology of Russia, 125047, Moscow, Russia
| | - Dmitry Klinov
- Federal Research and Clinical Center of Physical-Chemical Medicine, Moscow, 119435, Russia; Peoples' Friendship University of Russia (RUDN University), 117198, Moscow, Russia
| | - Vladimir Tsvetkov
- Federal Research and Clinical Center of Physical-Chemical Medicine, Moscow, 119435, Russia; Institute of Biodesign and Complex System Modeling, I.M. Sechenov First Moscow State Medical University, Moscow, 119991, Russia; A.V. Topchiev Institute of Petrochemical Synthesis, Leninsky Prospect Str. 29, Moscow, 119991, Russia.
| | - Anna Varizhuk
- Federal Research and Clinical Center of Physical-Chemical Medicine, Moscow, 119435, Russia; Moscow Institute of Physics and Technology, Dolgoprudny, 141701, Russia; Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Federal Research and Clinical Center of Physical-Chemical Medicine of Federal Medical Biological Agency, Moscow, 119435, Russia.
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8
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Sahayasheela VJ, Yu Z, Hidaka T, Pandian GN, Sugiyama H. Mitochondria and G-quadruplex evolution: an intertwined relationship. Trends Genet 2023; 39:15-30. [PMID: 36414480 PMCID: PMC9772288 DOI: 10.1016/j.tig.2022.10.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Revised: 09/27/2022] [Accepted: 10/27/2022] [Indexed: 11/21/2022]
Abstract
G-quadruplexes (G4s) are non-canonical structures formed in guanine (G)-rich sequences through stacked G tetrads by Hoogsteen hydrogen bonding. Several studies have demonstrated the existence of G4s in the genome of various organisms, including humans, and have proposed that G4s have a regulatory role in various cellular functions. However, little is known regarding the dissemination of G4s in mitochondria. In this review, we report the observation that the number of potential G4-forming sequences in the mitochondrial genome increases with the evolutionary complexity of different species, suggesting that G4s have a beneficial role in higher-order organisms. We also discuss the possible function of G4s in mitochondrial (mt)DNA and long noncoding (lnc)RNA and their role in various biological processes.
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Affiliation(s)
- Vinodh J Sahayasheela
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan
| | - Zutao Yu
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan
| | - Takuya Hidaka
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan
| | - Ganesh N Pandian
- Institute for Integrated Cell-Material Science (WPI-iCeMS), Kyoto University, Sakyo, Kyoto 606-8501, Japan
| | - Hiroshi Sugiyama
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan; Institute for Integrated Cell-Material Science (WPI-iCeMS), Kyoto University, Sakyo, Kyoto 606-8501, Japan.
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9
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Mellor C, Perez C, Sale JE. Creation and resolution of non-B-DNA structural impediments during replication. Crit Rev Biochem Mol Biol 2022; 57:412-442. [PMID: 36170051 PMCID: PMC7613824 DOI: 10.1080/10409238.2022.2121803] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2022] [Revised: 08/02/2022] [Accepted: 08/25/2022] [Indexed: 01/27/2023]
Abstract
During replication, folding of the DNA template into non-B-form secondary structures provides one of the most abundant impediments to the smooth progression of the replisome. The core replisome collaborates with multiple accessory factors to ensure timely and accurate duplication of the genome and epigenome. Here, we discuss the forces that drive non-B structure formation and the evidence that secondary structures are a significant and frequent source of replication stress that must be actively countered. Taking advantage of recent advances in the molecular and structural biology of the yeast and human replisomes, we examine how structures form and how they may be sensed and resolved during replication.
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Affiliation(s)
- Christopher Mellor
- Division of Protein & Nucleic Acid Chemistry, MRC Laboratory of Molecular Biology, Cambridge, UK
| | - Consuelo Perez
- Division of Protein & Nucleic Acid Chemistry, MRC Laboratory of Molecular Biology, Cambridge, UK
| | - Julian E Sale
- Division of Protein & Nucleic Acid Chemistry, MRC Laboratory of Molecular Biology, Cambridge, UK
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10
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High-throughput techniques enable advances in the roles of DNA and RNA secondary structures in transcriptional and post-transcriptional gene regulation. Genome Biol 2022; 23:159. [PMID: 35851062 PMCID: PMC9290270 DOI: 10.1186/s13059-022-02727-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 07/07/2022] [Indexed: 12/27/2022] Open
Abstract
The most stable structure of DNA is the canonical right-handed double helix termed B DNA. However, certain environments and sequence motifs favor alternative conformations, termed non-canonical secondary structures. The roles of DNA and RNA secondary structures in transcriptional regulation remain incompletely understood. However, advances in high-throughput assays have enabled genome wide characterization of some secondary structures. Here, we describe their regulatory functions in promoters and 3’UTRs, providing insights into key mechanisms through which they regulate gene expression. We discuss their implication in human disease, and how advances in molecular technologies and emerging high-throughput experimental methods could provide additional insights.
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11
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Pramanik S, Chen Y, Song H, Khutsishvili I, Marky LA, Ray S, Natarajan A, Singh P, Bhakat K. The human AP-endonuclease 1 (APE1) is a DNA G-quadruplex structure binding protein and regulates KRAS expression in pancreatic ductal adenocarcinoma cells. Nucleic Acids Res 2022; 50:3394-3412. [PMID: 35286386 PMCID: PMC8990529 DOI: 10.1093/nar/gkac172] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 02/14/2022] [Accepted: 03/08/2022] [Indexed: 11/12/2022] Open
Abstract
Pancreatic ductal adenocarcinoma (PDAC), one of the most aggressive types of cancer, is characterized by aberrant activity of oncogenic KRAS. A nuclease-hypersensitive GC-rich region in KRAS promoter can fold into a four-stranded DNA secondary structure called G-quadruplex (G4), known to regulate KRAS expression. However, the factors that regulate stable G4 formation in the genome and KRAS expression in PDAC are largely unknown. Here, we show that APE1 (apurinic/apyrimidinic endonuclease 1), a multifunctional DNA repair enzyme, is a G4-binding protein, and loss of APE1 abrogates the formation of stable G4 structures in cells. Recombinant APE1 binds to KRAS promoter G4 structure with high affinity and promotes G4 folding in vitro. Knockdown of APE1 reduces MAZ transcription factor loading onto the KRAS promoter, thus reducing KRAS expression in PDAC cells. Moreover, downregulation of APE1 sensitizes PDAC cells to chemotherapeutic drugs in vitro and in vivo. We also demonstrate that PDAC patients' tissue samples have elevated levels of both APE1 and G4 DNA. Our findings unravel a critical role of APE1 in regulating stable G4 formation and KRAS expression in PDAC and highlight G4 structures as genomic features with potential application as a novel prognostic marker and therapeutic target in PDAC.
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Affiliation(s)
- Suravi Pramanik
- Department of Genetics, Cell Biology and Anatomy, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Yingling Chen
- Department of Genetics, Cell Biology and Anatomy, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Heyu Song
- Department of Genetics, Cell Biology and Anatomy, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Irine Khutsishvili
- Department of Pharmaceutical Sciences, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Luis A Marky
- Department of Pharmaceutical Sciences, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Sutapa Ray
- Hematology/Oncology Division, Department of Pediatrics, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Amarnath Natarajan
- Eppley Institute for Research in Cancer and Allied Health, University of Nebraska Medical Center, Omaha, NE 68198, USA
- Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Pankaj K Singh
- Eppley Institute for Research in Cancer and Allied Health, University of Nebraska Medical Center, Omaha, NE 68198, USA
- Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Kishor K Bhakat
- Department of Genetics, Cell Biology and Anatomy, University of Nebraska Medical Center, Omaha, NE 68198, USA
- Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198, USA
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12
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Zyner KG, Simeone A, Flynn SM, Doyle C, Marsico G, Adhikari S, Portella G, Tannahill D, Balasubramanian S. G-quadruplex DNA structures in human stem cells and differentiation. Nat Commun 2022; 13:142. [PMID: 35013231 PMCID: PMC8748810 DOI: 10.1038/s41467-021-27719-1] [Citation(s) in RCA: 41] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 12/02/2021] [Indexed: 12/13/2022] Open
Abstract
The establishment of cell identity during embryonic development involves the activation of specific gene expression programmes and is underpinned by epigenetic factors including DNA methylation and histone post-translational modifications. G-quadruplexes are four-stranded DNA secondary structures (G4s) that have been implicated in transcriptional regulation and cancer. Here, we show that G4s are key genomic structural features linked to cellular differentiation. We find that G4s are highly abundant in human embryonic stem cells and are lost during lineage specification. G4s are prevalent in enhancers and promoters. G4s that are found in common between embryonic and downstream lineages are tightly linked to transcriptional stabilisation of genes involved in essential cellular functions as well as transitions in the histone post-translational modification landscape. Furthermore, the application of small molecules that stabilise G4s causes a delay in stem cell differentiation, keeping cells in a more pluripotent-like state. Collectively, our data highlight G4s as important epigenetic features that are coupled to stem cell pluripotency and differentiation.
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Affiliation(s)
- Katherine G Zyner
- Cancer Research UK Cambridge Institute, Li Ka Shing Centre, Robinson Way, Cambridge, CB2 0RE, UK
| | - Angela Simeone
- Cancer Research UK Cambridge Institute, Li Ka Shing Centre, Robinson Way, Cambridge, CB2 0RE, UK
| | - Sean M Flynn
- Cancer Research UK Cambridge Institute, Li Ka Shing Centre, Robinson Way, Cambridge, CB2 0RE, UK
| | - Colm Doyle
- Cancer Research UK Cambridge Institute, Li Ka Shing Centre, Robinson Way, Cambridge, CB2 0RE, UK
| | - Giovanni Marsico
- Cancer Research UK Cambridge Institute, Li Ka Shing Centre, Robinson Way, Cambridge, CB2 0RE, UK
| | - Santosh Adhikari
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
| | - Guillem Portella
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
| | - David Tannahill
- Cancer Research UK Cambridge Institute, Li Ka Shing Centre, Robinson Way, Cambridge, CB2 0RE, UK
| | - Shankar Balasubramanian
- Cancer Research UK Cambridge Institute, Li Ka Shing Centre, Robinson Way, Cambridge, CB2 0RE, UK.
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.
- School of Clinical Medicine, University of Cambridge, Cambridge, CB2 0SP, UK.
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13
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Kretzmann JA, Irving KL, Smith NM, Evans CW. Modulating gene expression in breast cancer via DNA secondary structure and the CRISPR toolbox. NAR Cancer 2022; 3:zcab048. [PMID: 34988459 PMCID: PMC8693572 DOI: 10.1093/narcan/zcab048] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 11/26/2021] [Accepted: 12/01/2021] [Indexed: 12/11/2022] Open
Abstract
Breast cancer is the most commonly diagnosed malignancy in women, and while the survival prognosis of patients with early-stage, non-metastatic disease is ∼75%, recurrence poses a significant risk and advanced and/or metastatic breast cancer is incurable. A distinctive feature of advanced breast cancer is an unstable genome and altered gene expression patterns that result in disease heterogeneity. Transcription factors represent a unique therapeutic opportunity in breast cancer, since they are known regulators of gene expression, including gene expression involved in differentiation and cell death, which are themselves often mutated or dysregulated in cancer. While transcription factors have traditionally been viewed as 'undruggable', progress has been made in the development of small-molecule therapeutics to target relevant protein-protein, protein-DNA and enzymatic active sites, with varying levels of success. However, non-traditional approaches such as epigenetic editing, transcriptional control via CRISPR/dCas9 systems, and gene regulation through non-canonical nucleic acid secondary structures represent new directions yet to be fully explored. Here, we discuss these new approaches and current limitations in light of new therapeutic opportunities for breast cancers.
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Affiliation(s)
- Jessica A Kretzmann
- Laboratory for Biomolecular Nanotechnology, Department of Physics, Technical University of Munich, Am Coulombwall 4a, 85748 Garching, Germany
| | - Kelly L Irving
- School of Molecular Sciences, The University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia
| | - Nicole M Smith
- School of Molecular Sciences, The University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia
| | - Cameron W Evans
- School of Molecular Sciences, The University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia
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14
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Forsyth RG, Krenács T, Athanasou N, Hogendoorn PCW. Cell Biology of Giant Cell Tumour of Bone: Crosstalk between m/wt Nucleosome H3.3, Telomeres and Osteoclastogenesis. Cancers (Basel) 2021; 13:5119. [PMID: 34680268 PMCID: PMC8534144 DOI: 10.3390/cancers13205119] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Revised: 10/06/2021] [Accepted: 10/08/2021] [Indexed: 12/14/2022] Open
Abstract
Giant cell tumour of bone (GCTB) is a rare and intriguing primary bone neoplasm. Worrisome clinical features are its local destructive behaviour, its high tendency to recur after surgical therapy and its ability to create so-called benign lung metastases (lung 'plugs'). GCTB displays a complex and difficult-to-understand cell biological behaviour because of its heterogenous morphology. Recently, a driver mutation in histone H3.3 was found. This mutation is highly conserved in GCTB but can also be detected in glioblastoma. Denosumab was recently introduced as an extra option of medical treatment next to traditional surgical and in rare cases, radiotherapy. Despite these new insights, many 'old' questions about the key features of GCTB remain unanswered, such as the presence of telomeric associations (TAs), the reactivation of hTERT, and its slight genomic instability. This review summarises the recent relevant literature of histone H3.3 in relation to the GCTB-specific G34W mutation and pays specific attention to the G34W mutation in relation to the development of TAs, genomic instability, and the characteristic morphology of GCTB. As pieces of an etiogenetic puzzle, this review tries fitting all these molecular features and the unique H3.3 G34W mutation together in GCTB.
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Affiliation(s)
- Ramses G. Forsyth
- Department of Pathology, University Hospital Brussels (UZB), Laarbeeklaan 101, 1090 Brussels, Belgium;
- Labaratorium for Experimental Pathology (EXPA), Vrije Universiteit Brussel (VUB), Laarbeeklaan 103, 1090 Brussels, Belgium
| | - Tibor Krenács
- 1st Department of Pathology and Experimental Cancer Research, Semmelweis University, Üllöi ut 26, 1085 Budapest, Hungary;
| | - Nicholas Athanasou
- Department of Histopathology, Nuffield Orthopaedic Centre, University of Oxford, NDORMS, Oxford OX3 7HE, UK;
| | - Pancras C. W. Hogendoorn
- Department of Pathology, University Hospital Brussels (UZB), Laarbeeklaan 101, 1090 Brussels, Belgium;
- Labaratorium for Experimental Pathology (EXPA), Vrije Universiteit Brussel (VUB), Laarbeeklaan 103, 1090 Brussels, Belgium
- 1st Department of Pathology and Experimental Cancer Research, Semmelweis University, Üllöi ut 26, 1085 Budapest, Hungary;
- Department of Histopathology, Nuffield Orthopaedic Centre, University of Oxford, NDORMS, Oxford OX3 7HE, UK;
- Department of Pathology, Leiden University Medical Center (LUMC), Albinusdreef 2, 2300 RC Leiden, The Netherlands
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15
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Robinson J, Raguseo F, Nuccio SP, Liano D, Di Antonio M. DNA G-quadruplex structures: more than simple roadblocks to transcription? Nucleic Acids Res 2021; 49:8419-8431. [PMID: 34255847 PMCID: PMC8421137 DOI: 10.1093/nar/gkab609] [Citation(s) in RCA: 113] [Impact Index Per Article: 37.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 07/01/2021] [Accepted: 07/05/2021] [Indexed: 12/12/2022] Open
Abstract
It has been >20 years since the formation of G-quadruplex (G4) secondary structures in gene promoters was first linked to the regulation of gene expression. Since then, the development of small molecules to selectively target G4s and their cellular application have contributed to an improved understanding of how G4s regulate transcription. One model that arose from this work placed these non-canonical DNA structures as repressors of transcription by preventing polymerase processivity. Although a considerable number of studies have recently provided sufficient evidence to reconsider this simplistic model, there is still a misrepresentation of G4s as transcriptional roadblocks. In this review, we will challenge this model depicting G4s as simple 'off switches' for gene expression by articulating how their formation has the potential to alter gene expression at many different levels, acting as a key regulatory element perturbing the nature of epigenetic marks and chromatin architecture.
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Affiliation(s)
- Jenna Robinson
- Imperial College London, Chemistry Department, Molecular Sciences Research Hub, 82 Wood Lane, London W12 0BZ, UK
- Institute of Chemical Biology, Molecular Sciences Research Hub, 82 Wood Lane, London W12 0BZ, UK
| | - Federica Raguseo
- Imperial College London, Chemistry Department, Molecular Sciences Research Hub, 82 Wood Lane, London W12 0BZ, UK
- Institute of Chemical Biology, Molecular Sciences Research Hub, 82 Wood Lane, London W12 0BZ, UK
| | - Sabrina Pia Nuccio
- Imperial College London, Chemistry Department, Molecular Sciences Research Hub, 82 Wood Lane, London W12 0BZ, UK
- Institute of Chemical Biology, Molecular Sciences Research Hub, 82 Wood Lane, London W12 0BZ, UK
| | - Denise Liano
- Imperial College London, Chemistry Department, Molecular Sciences Research Hub, 82 Wood Lane, London W12 0BZ, UK
- Institute of Chemical Biology, Molecular Sciences Research Hub, 82 Wood Lane, London W12 0BZ, UK
| | - Marco Di Antonio
- Imperial College London, Chemistry Department, Molecular Sciences Research Hub, 82 Wood Lane, London W12 0BZ, UK
- Institute of Chemical Biology, Molecular Sciences Research Hub, 82 Wood Lane, London W12 0BZ, UK
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
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16
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Tabor N, Ngwa C, Mitteaux J, Meyer MD, Moruno-Manchon JF, Zhu L, Liu F, Monchaud D, McCullough LD, Tsvetkov AS. Differential responses of neurons, astrocytes, and microglia to G-quadruplex stabilization. Aging (Albany NY) 2021; 13:15917-15941. [PMID: 34139671 PMCID: PMC8266374 DOI: 10.18632/aging.203222] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Accepted: 06/12/2021] [Indexed: 12/29/2022]
Abstract
The G-quadruplex (G4-DNA or G4) is a secondary DNA structure formed by DNA sequences containing multiple runs of guanines. While it is now firmly established that stabilized G4s lead to enhanced genomic instability in cancer cells, whether and how G4s contribute to genomic instability in brain cells is still not clear. We previously showed that, in cultured primary neurons, small-molecule G4 stabilizers promote formation of DNA double-strand breaks (DSBs) and downregulate the Brca1 gene. Here, we determined if G4-dependent Brca1 downregulation is unique to neurons or if the effects in neurons also occur in astrocytes and microglia. We show that primary neurons, astrocytes and microglia basally exhibit different G4 landscapes. Stabilizing G4-DNA with the G4 ligand pyridostatin (PDS) differentially modifies chromatin structure in these cell types. Intriguingly, PDS promotes DNA DSBs in neurons, astrocytes and microglial cells, but fails to downregulate Brca1 in astrocytes and microglia, indicating differences in DNA damage and repair pathways between brain cell types. Taken together, our findings suggest that stabilized G4-DNA contribute to genomic instability in the brain and may represent a novel senescence pathway in brain aging.
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Affiliation(s)
- Natalie Tabor
- Department of Neurology, The University of Texas McGovern Medical School at Houston, Houston, TX 77030, USA
| | - Conelius Ngwa
- Department of Neurology, The University of Texas McGovern Medical School at Houston, Houston, TX 77030, USA
| | - Jeremie Mitteaux
- Institut de Chimie Moléculaire (ICMUB), UBFC Dijon, CNRS UMR6302, Dijon, France
| | - Matthew D. Meyer
- Shared Equipment Authority, Rice University, Houston, TX 77005, USA
| | - Jose F. Moruno-Manchon
- Department of Neurology, The University of Texas McGovern Medical School at Houston, Houston, TX 77030, USA
| | - Liang Zhu
- Biostatistics and Epidemiology Research Design Core Center for Clinical and Translational Sciences, The University of Texas McGovern Medical School at Houston, Houston, TX 77030, USA
- Department of Internal Medicine, The University of Texas McGovern Medical School at Houston, Houston, TX 77030, USA
| | - Fudong Liu
- Department of Neurology, The University of Texas McGovern Medical School at Houston, Houston, TX 77030, USA
| | - David Monchaud
- Institut de Chimie Moléculaire (ICMUB), UBFC Dijon, CNRS UMR6302, Dijon, France
| | - Louise D. McCullough
- Department of Neurology, The University of Texas McGovern Medical School at Houston, Houston, TX 77030, USA
- The University of Texas Graduate School of Biomedical Sciences, Houston, TX 77030, USA
| | - Andrey S. Tsvetkov
- Department of Neurology, The University of Texas McGovern Medical School at Houston, Houston, TX 77030, USA
- The University of Texas Graduate School of Biomedical Sciences, Houston, TX 77030, USA
- UTHealth Consortium on Aging, The University of Texas McGovern Medical School, Houston, TX 77030, USA
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17
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Dey U, Sarkar S, Teronpi V, Yella VR, Kumar A. G-quadruplex motifs are functionally conserved in cis-regulatory regions of pathogenic bacteria: An in-silico evaluation. Biochimie 2021; 184:40-51. [PMID: 33548392 DOI: 10.1016/j.biochi.2021.01.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 01/28/2021] [Accepted: 01/29/2021] [Indexed: 02/06/2023]
Abstract
The role of G-quadruplexes in the cellular physiology of human pathogenesis is an intriguing area of research. Nonetheless, their functional roles and evolutionary conservation have not been compared comprehensively in pathogenic forms of various bacterial genera and species. In the current in silico study, we addressed the role of G-quadruplex-forming sequences (G4 motifs) in the context of cis-regulation, expression variation, regulatory networks, gene orthology and ontology. Genome-wide screening across seven pathogenic genomes using the G4Hunter tool revealed the significant prevalence of G4 motifs in cis-regulatory regions compared to the intragenic regions. Significant conservation of G4 motifs was observed in the regulatory region of 300 orthologous genes. Further analysis of published ChIP-Seq data (Minch et al., 2015) of 91 DNA-binding proteins of the M. tuberculosis genome revealed significant links between G4 motifs and target sites of transcriptional regulators. Interestingly, the transcription factors entangled with virulence, in specific, CsoR, Rv0081, DevR/DosR, and TetR family are found to have G4 motifs in their target regulatory regions. Overall the current study applies positional-functional relationship computation to delve into the cis-regulation of G-quadruplex structures in the context of gene orthology in pathogenic bacteria.
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Affiliation(s)
- Upalabdha Dey
- Department of Molecular Biology and Biotechnology, Tezpur University, Tezpur, 784028, Assam, India
| | - Sharmilee Sarkar
- Department of Molecular Biology and Biotechnology, Tezpur University, Tezpur, 784028, Assam, India
| | - Valentina Teronpi
- Department of Zoology, Pandit Deendayal Upadhyaya Adarsha Mahavidyalaya, Behali, Biswanath, 784184, Assam, India
| | - Venkata Rajesh Yella
- Department of Biotechnology, Koneru Lakshmaiah Education Foundation, Guntur, 522502, Andhra Pradesh, India.
| | - Aditya Kumar
- Department of Molecular Biology and Biotechnology, Tezpur University, Tezpur, 784028, Assam, India.
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18
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Sengupta A, Roy SS, Chowdhury S. Non-duplex G-Quadruplex DNA Structure: A Developing Story from Predicted Sequences to DNA Structure-Dependent Epigenetics and Beyond. Acc Chem Res 2021; 54:46-56. [PMID: 33347280 DOI: 10.1021/acs.accounts.0c00431] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The story of the non-duplex DNA form known as the G-quadruplex (G4) has traversed a winding path. From initial skepticism followed by debate to a surge in interest, the G4 story intertwines many threads. Starting with computational predictions of a gene regulatory role, which now include epigenetic functions, our group was involved in many of these advances along with many other laboratories. Following a brief background, set in the latter half of the last century when the concept of the G4 as a structure took ground, here we account the developments. This is through a lens that though focused on our groups' research presents work from many other groups that played significant roles. Together these provide a broad perspective to the G4 story. Initially we were intrigued on seeing potential G4 (pG4)-forming sequences, then known to be found primarily at the telomeres and immunoglobin switch regions, occurring throughout the genome and being particularly prevalent in promoters of bacteria. We further observed that pG4s were not only prevalent but also conserved through evolution in promoters of human, chimpanzee, mouse and rat genomes. This was between 2005 and 2007. Encouraged by these partly and partly in response to the view held by many that genome-wide presence of G4s were genomic "accidents", the focus shifted to seeking experimental evidence.In the next year, 2008, two independent findings showed promise. First, on treating human cancer cells with G4-binding ligands, we observed widespread change in gene expression. Second, our search for the missing G4-specific transcription factor, without which, importantly, G4s in promoters posed only half the story, yielded results. We determined how NM23-H2 (also known as NME2 or NDPK-B) interacts with G4s and how interaction of NM23-H2 with a G4 in the promoter of the oncogene c-myc was important for regulation of c-myc transcription. NM23-H2, and subsequently many other similar factors discovered by multiple groups, is possibly giving shape to what might be the "G4-transcriptome". Later, a close look at NM23-H2-G4 interaction in regulation of the human reverse transcriptase gene (hTERT) revealed the role of G4s in local epigenetic modifications. Meanwhile work from others showed how G4s impact histone modifications following replication. Together these show the intrinsic role of DNA sequence, through formation of DNA structure, in epigenetics.More recent work, however, was waiting to reveal aspects that tend to bring forth a completely new understanding of G4s. We observed that the telomere-repeat-binding-factor-2 (TRF2), known canonically to be telomere-associated, binds extensively outside telomeres throughout the genome. Moreover, a large fraction of the non-telomeric TRF2 sites comprise G4s. Second, the extent of non-telomeric TRF2 binding at promoters was dependent on telomere length. Thereby TRF2-induced epigenetic gene regulation was telomere-dependent. Together these implicate underlying connections that show signs of addressing an intriguing unanswered question that takes us back to the beginning: Why are G4s prevalent in two distinct regions, the telomeres and gene promoters?
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Affiliation(s)
- Antara Sengupta
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Shuvra Shekhar Roy
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Shantanu Chowdhury
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
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19
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Malousi A, Andreou AZ, Kouidou S. In silico structural analysis of sequences containing 5-hydroxymethylcytosine reveals its potential as binding regulator for development, ageing and cancer-related transcription factors. Epigenetics 2020; 16:503-518. [PMID: 32752914 DOI: 10.1080/15592294.2020.1805693] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The presence of 5-hydroxymethyl cytosine in DNA has been previously associated with ageing. Using in silico analysis of normal liver samples we presently observed that in 5-hydroxymethyl cytosine sequences, DNA methylation is dependent on the co-presence of G-quadruplexes and palindromes. This association exhibits discrete patterns depending on G-quadruplex and palindrome densities. DNase-Seq data show that 5-hydroxymethyl cytosine sequences are common among liver nucleosomes (p < 2.2x10-16) and threefold more frequent than nucleosome sequences. Nucleosomes lacking palindromes and potential G-quadruplexes are rare in vivo (1%) and nucleosome occupancy potential decreases with increasing G-quadruplexes. Palindrome distribution is similar to that previously reported in nucleosomes. In low and mixed complexity sequences 5-hydroxymethyl cytosine is frequently located next to three elements: G-quadruplexes or imperfect G-quadruplexes with CpGs, or unstable hairpin loops (TCCCAY6TGGGA) mostly located in antisense strands or finally A-/T-rich segments near these motifs. The high frequencies and selective distribution of pentamer sequences (including TCCCA, TGGGA) probably indicate the positive contribution of 5-hydroxymethyl cytosine to stabilize the formation of structures unstable in the absence of this cytosine modification. Common motifs identified in all total 5-hydroxymethyl cytosine-containing sequences exhibit high homology to recognition sites of several transcription factor families: homeobox, factors involved in growth, mortality/ageing, cancer, neuronal function, vision, and reproduction. We conclude that cytosine hydroxymethylation could play a role in the recognition of sequences with G-quadruplexes/palindromes by forming epigenetically regulated DNA 'springs' and governing expansions or compressions recognized by different transcription factors or stabilizing nucleosomes. The balance of these epigenetic elements is lost in hepatocellular carcinoma.
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Affiliation(s)
- Andigoni Malousi
- Lab. of Biological Chemistry, Medical School, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | | | - Sofia Kouidou
- Lab. of Biological Chemistry, Medical School, Aristotle University of Thessaloniki, Thessaloniki, Greece
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20
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Abstract
Several decades elapsed between the first descriptions of G-quadruplex nucleic acid structures (G4s) assembled in vitro and the emergence of experimental findings indicating that such structures can form and function in living systems. A large body of evidence now supports roles for G4s in many aspects of nucleic acid biology, spanning processes from transcription and chromatin structure, mRNA processing, protein translation, DNA replication and genome stability, and telomere and mitochondrial function. Nonetheless, it must be acknowledged that some of this evidence is tentative, which is not surprising given the technical challenges associated with demonstrating G4s in biology. Here I provide an overview of evidence for G4 biology, focusing particularly on the many potential pitfalls that can be encountered in its investigation, and briefly discuss some of broader biological processes that may be impacted by G4s including cancer.
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Affiliation(s)
- F. Brad Johnson
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, United States
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21
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Reina C, Cavalieri V. Epigenetic Modulation of Chromatin States and Gene Expression by G-Quadruplex Structures. Int J Mol Sci 2020; 21:E4172. [PMID: 32545267 PMCID: PMC7312119 DOI: 10.3390/ijms21114172] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 06/07/2020] [Accepted: 06/10/2020] [Indexed: 02/07/2023] Open
Abstract
G-quadruplexes are four-stranded helical nucleic acid structures formed by guanine-rich sequences. A considerable number of studies have revealed that these noncanonical structural motifs are widespread throughout the genome and transcriptome of numerous organisms, including humans. In particular, G-quadruplexes occupy strategic locations in genomic DNA and both coding and noncoding RNA molecules, being involved in many essential cellular and organismal functions. In this review, we first outline the fundamental structural features of G-quadruplexes and then focus on the concept that these DNA and RNA structures convey a distinctive layer of epigenetic information that is critical for the complex regulation, either positive or negative, of biological activities in different contexts. In this framework, we summarize and discuss the proposed mechanisms underlying the functions of G-quadruplexes and their interacting factors. Furthermore, we give special emphasis to the interplay between G-quadruplex formation/disruption and other epigenetic marks, including biochemical modifications of DNA bases and histones, nucleosome positioning, and three-dimensional organization of chromatin. Finally, epigenetic roles of RNA G-quadruplexes in post-transcriptional regulation of gene expression are also discussed. Undoubtedly, the issues addressed in this review take on particular importance in the field of comparative epigenetics, as well as in translational research.
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Affiliation(s)
- Chiara Reina
- Department of Health Promotion, Mother and Child Care, Internal Medicine and Medical Specialties (PROMISE), University of Palermo, 90127 Palermo, Italy;
| | - Vincenzo Cavalieri
- Department of Biological, Chemical and Pharmaceutical Sciences and Technologies (STEBICEF), University of Palermo, 90128 Palermo, Italy
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22
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Kim N. The Interplay between G-quadruplex and Transcription. Curr Med Chem 2019; 26:2898-2917. [PMID: 29284393 PMCID: PMC6026074 DOI: 10.2174/0929867325666171229132619] [Citation(s) in RCA: 83] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2017] [Revised: 11/22/2017] [Accepted: 12/21/2017] [Indexed: 12/25/2022]
Abstract
G4 DNA is a non-canonical DNA structure consisting of a stacked array of Gquartets held together by base pairing between guanine bases. The formation of G4 DNA requires a cluster of guanine-runs within a strand of DNA. Even though the chemistry of this remarkable DNA structure has been under investigation for decades, evidence supporting the biological relevance of G4 DNA has only begun to emerge and point to very important and conserved biological functions. This review will specifically focus on the interplay between transcription and G4 DNA and discuss two alternative but interconnected perspectives. The first part of the review will describe the evidence substantiating the intriguing idea that a shift in DNA structural conformation could be another layer of non-genetic or epigenetic regulator of gene expression and thereby an important determinant of cell fate. The second part will describe the recent genetic studies showing that those genomic loci containing G4 DNA-forming guanine-rich sequences are potential hotspots of genome instability and that the level and orientation of transcription is critical in the materialization of genome instability associated with these sequences.
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Affiliation(s)
- Nayun Kim
- Department of Microbiology and Molecular Genetics, The University of Texas Health Science Center at Houston; The University of Texas Graduate School of Biomedical Sciences, Houston, TX, United States
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23
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Hou Y, Li F, Zhang R, Li S, Liu H, Qin ZS, Sun X. Integrative characterization of G-Quadruplexes in the three-dimensional chromatin structure. Epigenetics 2019; 14:894-911. [PMID: 31177910 PMCID: PMC6691997 DOI: 10.1080/15592294.2019.1621140] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2019] [Revised: 05/05/2019] [Accepted: 05/14/2019] [Indexed: 12/14/2022] Open
Abstract
DNA molecules are highly compacted in the eukaryotic nucleus where distal regulatory elements reach their targets through three-dimensional chromosomal interactions. G-quadruplexes, stable four-stranded non-canonical DNA structures, can change local chromatin organization through the exclusion of nucleosomes. However, the relationship between G-quadruplexes and higher-order genome organization remains unknown. Here, we found that G-quadruplexes are significantly enriched at boundaries of topological associated domains (TADs). Architectural protein occupancy, which plays critical roles in the formation of TADs, was highly correlated with the content of G-quadruplexes at TAD boundaries. Moreover, adjacent boundaries containing G-quadruplexes frequently interacted with each other because of the high enrichment of architectural protein binding sites. Similar to CCCTC-binding factor (CTCF) binding sites, G-quadruplexes also showed strong insulation ability in the separation of adjacent regions. Additionally, the insulation ability of CTCF binding sites and TAD boundaries was significantly reinforced by G-quadruplexes. Furthermore, G-quadruplex motifs on different strands were associated with the orientation of CTCF binding sites. These findings suggest a potential role for G-quadruplexes in loop extrusion. The enrichment of transcription factor binding sites (TFBSs) around regulatory elements containing G-quadruplexes led to frequent interactions between regulatory elements containing G-quadruplexes. Intriguingly, more than 99% of G-quadruplexes overlapped with TFBSs. The binding sites of CTCF and cohesin proteins were preferentially located surrounding G-quadruplexes. Accordingly, we proposed a new mechanism of long-distance gene regulation in which G-quadruplexes are involved in distal interactions between enhancers and promoters.
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Affiliation(s)
- Yue Hou
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing, Jiangsu, China
| | - Fuyu Li
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing, Jiangsu, China
| | - Rongxin Zhang
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing, Jiangsu, China
| | - Sheng Li
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing, Jiangsu, China
| | - Hongde Liu
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing, Jiangsu, China
| | - Zhaohui S. Qin
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing, Jiangsu, China
- Department of Biostatistics and Bioinformatics, Emory University, Atlanta, GA USA
| | - Xiao Sun
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing, Jiangsu, China
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Sugimoto N, Maehara K, Yoshida K, Ohkawa Y, Fujita M. Genome-wide analysis of the spatiotemporal regulation of firing and dormant replication origins in human cells. Nucleic Acids Res 2019; 46:6683-6696. [PMID: 29893900 PMCID: PMC6061783 DOI: 10.1093/nar/gky476] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Accepted: 05/16/2018] [Indexed: 12/25/2022] Open
Abstract
In metazoan cells, only a limited number of mini chromosome maintenance (MCM) complexes are fired during S phase, while the majority remain dormant. Several methods have been used to map replication origins, but such methods cannot identify dormant origins. Herein, we determined MCM7-binding sites in human cells using ChIP-Seq, classified them into firing and dormant origins using origin data and analysed their association with various chromatin signatures. Firing origins, but not dormant origins, were well correlated with open chromatin regions and were enriched upstream of transcription start sites (TSSs) of transcribed genes. Aggregation plots of MCM7 signals revealed minimal difference in the efficacy of MCM loading between firing and dormant origins. We also analysed common fragile sites (CFSs) and found a low density of origins at these sites. Nevertheless, firing origins were enriched upstream of the TSSs. Based on the results, we propose a model in which excessive MCMs are actively loaded in a genome-wide manner, irrespective of chromatin status, but only a fraction are passively fired in chromatin areas with an accessible open structure, such as regions upstream of TSSs of transcribed genes. This plasticity in the specification of replication origins may minimize collisions between replication and transcription.
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Affiliation(s)
- Nozomi Sugimoto
- Department of Cellular Biochemistry, Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashiku, Fukuoka 812-8582, Japan
| | - Kazumitsu Maehara
- Division of Transcriptomics, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashiku, Fukuoka 812-8582, Japan
| | - Kazumasa Yoshida
- Department of Cellular Biochemistry, Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashiku, Fukuoka 812-8582, Japan
| | - Yasuyuki Ohkawa
- Division of Transcriptomics, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashiku, Fukuoka 812-8582, Japan
| | - Masatoshi Fujita
- Department of Cellular Biochemistry, Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashiku, Fukuoka 812-8582, Japan
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Falabella M, Fernandez RJ, Johnson FB, Kaufman BA. Potential Roles for G-Quadruplexes in Mitochondria. Curr Med Chem 2019; 26:2918-2932. [PMID: 29493440 PMCID: PMC6113130 DOI: 10.2174/0929867325666180228165527] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Revised: 02/16/2018] [Accepted: 02/16/2018] [Indexed: 02/07/2023]
Abstract
Some DNA or RNA sequences rich in guanine (G) nucleotides can adopt noncanonical conformations known as G-quadruplexes (G4). In the nuclear genome, G4 motifs have been associated with genome instability and gene expression defects, but they are increasingly recognized to be regulatory structures. Recent studies have revealed that G4 structures can form in the mitochondrial genome (mtDNA) and potential G4 forming sequences are associated with the origin of mtDNA deletions. However, little is known about the regulatory role of G4 structures in mitochondria. In this short review, we will explore the potential for G4 structures to regulate mitochondrial function, based on evidence from the nucleus.
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Affiliation(s)
- Micol Falabella
- University of Pittsburgh School of Medicine, Division of Cardiology, Center for Metabolism and Mitochondrial Medicine and Vascular Medicine Institute, Pittsburgh, PA, United States
| | - Rafael J Fernandez
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine University of Pennsylvania, Philadelphia, PA, United States
| | - F Brad Johnson
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine University of Pennsylvania, Philadelphia, PA, United States
| | - Brett A Kaufman
- University of Pittsburgh School of Medicine, Division of Cardiology, Center for Metabolism and Mitochondrial Medicine and Vascular Medicine Institute, Pittsburgh, PA, United States
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26
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Non-duplex G-Quadruplex Structures Emerge as Mediators of Epigenetic Modifications. Trends Genet 2018; 35:129-144. [PMID: 30527765 DOI: 10.1016/j.tig.2018.11.001] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 10/10/2018] [Accepted: 11/02/2018] [Indexed: 12/16/2022]
Abstract
The role of non-duplex DNA, the guanine-quadruplex structure in particular, is becoming widely appreciated. Increasing evidence in the last decade implicates quadruplexes in important processes such as transcription and replication. Interestingly, more recent work suggests roles for quadruplexes, in association with quadruplex-interacting proteins, in epigenetics through both DNA and histone modifications. Here, we review the effect of the quadruplex structure on post-replication epigenetic memory and quadruplex-induced promoter DNA/histone modifications. Furthermore, we highlight the epigenetic state of the telomerase promoter where quadruplexes could play a key regulatory role. Finally, we discuss the possibility that DNA structures such as quadruplexes, within a largely duplex DNA background, could act as molecular anchors for locally induced epigenetic modifications.
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Dhapola P, Chowdhury S. QuadBase2: web server for multiplexed guanine quadruplex mining and visualization. Nucleic Acids Res 2016; 44:W277-83. [PMID: 27185890 PMCID: PMC4987949 DOI: 10.1093/nar/gkw425] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 05/03/2016] [Indexed: 02/01/2023] Open
Abstract
DNA guanine quadruplexes or G4s are non-canonical DNA secondary structures which affect genomic processes like replication, transcription and recombination. G4s are computationally identified by specific nucleotide motifs which are also called putative G4 (PG4) motifs. Despite the general relevance of these structures, there is currently no tool available that can allow batch queries and genome-wide analysis of these motifs in a user-friendly interface. QuadBase2 (quadbase.igib.res.in) presents a completely reinvented web server version of previously published QuadBase database. QuadBase2 enables users to mine PG4 motifs in up to 178 eukaryotes through the EuQuad module. This module interfaces with Ensembl Compara database, to allow users mine PG4 motifs in the orthologues of genes of interest across eukaryotes. PG4 motifs can be mined across genes and their promoter sequences in 1719 prokaryotes through ProQuad module. This module includes a feature that allows genome-wide mining of PG4 motifs and their visualization as circular histograms. TetraplexFinder, the module for mining PG4 motifs in user-provided sequences is now capable of handling up to 20 MB of data. QuadBase2 is a comprehensive PG4 motif mining tool that further expands the configurations and algorithms for mining PG4 motifs in a user-friendly way.
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Affiliation(s)
- Parashar Dhapola
- GNR Knowledge Center for Genome Informatics, CSIR-Institute of Genomics and Integrative Biology, New Delhi 110 025, India
| | - Shantanu Chowdhury
- GNR Knowledge Center for Genome Informatics, CSIR-Institute of Genomics and Integrative Biology, New Delhi 110 025, India Proteomics and Structural Biology Unit, CSIR-Institute of Genomics and Integrative Biology, New Delhi 110 025, India
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Cayrou C, Ballester B, Peiffer I, Fenouil R, Coulombe P, Andrau JC, van Helden J, Méchali M. The chromatin environment shapes DNA replication origin organization and defines origin classes. Genome Res 2015; 25:1873-85. [PMID: 26560631 PMCID: PMC4665008 DOI: 10.1101/gr.192799.115] [Citation(s) in RCA: 112] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2015] [Accepted: 10/14/2015] [Indexed: 12/22/2022]
Abstract
To unveil the still-elusive nature of metazoan replication origins, we identified them genome-wide and at unprecedented high-resolution in mouse ES cells. This allowed initiation sites (IS) and initiation zones (IZ) to be differentiated. We then characterized their genetic signatures and organization and integrated these data with 43 chromatin marks and factors. Our results reveal that replication origins can be grouped into three main classes with distinct organization, chromatin environment, and sequence motifs. Class 1 contains relatively isolated, low-efficiency origins that are poor in epigenetic marks and are enriched in an asymmetric AC repeat at the initiation site. Late origins are mainly found in this class. Class 2 origins are particularly rich in enhancer elements. Class 3 origins are the most efficient and are associated with open chromatin and polycomb protein-enriched regions. The presence of Origin G-rich Repeated elements (OGRE) potentially forming G-quadruplexes (G4) was confirmed at most origins. These coincide with nucleosome-depleted regions located upstream of the initiation sites, which are associated with a labile nucleosome containing H3K64ac. These data demonstrate that specific chromatin landscapes and combinations of specific signatures regulate origin localization. They explain the frequently observed links between DNA replication and transcription. They also emphasize the plasticity of metazoan replication origins and suggest that in multicellular eukaryotes, the combination of distinct genetic features and chromatin configurations act in synergy to define and adapt the origin profile.
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Affiliation(s)
| | - Benoit Ballester
- INSERM, U1090 TAGC, Marseille F-13288, France; Aix Marseille University, U1090 TAGC, Marseille F-13288, France
| | | | - Romain Fenouil
- Centre d'Immunologie de Marseille-Luminy (CIML), 13009 Marseille, France
| | | | | | - Jacques van Helden
- INSERM, U1090 TAGC, Marseille F-13288, France; Aix Marseille University, U1090 TAGC, Marseille F-13288, France
| | - Marcel Méchali
- Institute of Human Genetics, CNRS, 34396 Montpellier, France
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Udugama M, M Chang FT, Chan FL, Tang MC, Pickett HA, R McGhie JD, Mayne L, Collas P, Mann JR, Wong LH. Histone variant H3.3 provides the heterochromatic H3 lysine 9 tri-methylation mark at telomeres. Nucleic Acids Res 2015; 43:10227-37. [PMID: 26304540 PMCID: PMC4666390 DOI: 10.1093/nar/gkv847] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2015] [Accepted: 08/11/2015] [Indexed: 11/15/2022] Open
Abstract
In addition to being a hallmark at active genes, histone variant H3.3 is deposited by ATRX at repressive chromatin regions, including the telomeres. It is unclear how H3.3 promotes heterochromatin assembly. We show that H3.3 is targeted for K9 trimethylation to establish a heterochromatic state enriched in trimethylated H3.3K9 at telomeres. In H3f3a−/− and H3f3b−/− mouse embryonic stem cells (ESCs), H3.3 deficiency results in reduced levels of H3K9me3, H4K20me3 and ATRX at telomeres. The H3f3b−/− cells show increased levels of telomeric damage and sister chromatid exchange (t-SCE) activity when telomeres are compromised by treatment with a G-quadruplex (G4) DNA binding ligand or by ASF1 depletion. Overexpression of wild-type H3.3 (but not a H3.3K9 mutant) in H3f3b−/− cells increases H3K9 trimethylation level at telomeres and represses t-SCE activity induced by a G4 ligand. This study demonstrates the importance of H3.3K9 trimethylation in heterochromatin formation at telomeres. It provides insights into H3.3 function in maintaining integrity of mammalian constitutive heterochromatin, adding to its role in mediating transcription memory in the genome.
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Affiliation(s)
- Maheshi Udugama
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Fiona T M Chang
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - F Lyn Chan
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Michelle C Tang
- Department of Zoology, University of Melbourne, Parkville, Victoria 3052, Australia
| | - Hilda A Pickett
- Telomere Length Regulation Group, Children's Medical Research Institute, University of Sydney, Westmead, New South Wales, Australia
| | - James D R McGhie
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Lynne Mayne
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Philippe Collas
- Department of Molecular Medicine, Institute of Basic Medical Sciences, Faculty of Medicine, and Norwegian Center for Stem Cell Research, University of Oslo, 0317 Oslo, Norway
| | - Jeffrey R Mann
- Department of Anatomy and Developmental Biology, Monash University, Clayton, Victoria 3800, Australia
| | - Lee H Wong
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia
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30
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Foulk MS, Urban JM, Casella C, Gerbi SA. Characterizing and controlling intrinsic biases of lambda exonuclease in nascent strand sequencing reveals phasing between nucleosomes and G-quadruplex motifs around a subset of human replication origins. Genome Res 2015; 25:725-35. [PMID: 25695952 PMCID: PMC4417120 DOI: 10.1101/gr.183848.114] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Accepted: 02/18/2015] [Indexed: 01/02/2023]
Abstract
Nascent strand sequencing (NS-seq) is used to discover DNA replication origins genome-wide, allowing identification of features for their specification. NS-seq depends on the ability of lambda exonuclease (λ-exo) to efficiently digest parental DNA while leaving RNA-primer protected nascent strands intact. We used genomics and biochemical approaches to determine if λ-exo digests all parental DNA sequences equally. We report that λ-exo does not efficiently digest G-quadruplex (G4) structures in a plasmid. Moreover, λ-exo digestion of nonreplicating genomic DNA (LexoG0) enriches GC-rich DNA and G4 motifs genome-wide. We used LexoG0 data to control for nascent strand–independent λ-exo biases in NS-seq and validated this approach at the rDNA locus. The λ-exo–controlled NS-seq peaks are not GC-rich, and only 35.5% overlap with 6.8% of all G4s, suggesting that G4s are not general determinants for origin specification but may play a role for a subset. Interestingly, we observed a periodic spacing of G4 motifs and nucleosomes around the peak summits, suggesting that G4s may position nucleosomes at this subset of origins. Finally, we demonstrate that use of Na+ instead of K+ in the λ-exo digestion buffer reduced the effect of G4s on λ-exo digestion and discuss ways to increase both the sensitivity and specificity of NS-seq.
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Affiliation(s)
- Michael S Foulk
- Brown University Division of Biology and Medicine, Department of Molecular Biology, Cell Biology and Biochemistry, Providence, Rhode Island 02912, USA
| | - John M Urban
- Brown University Division of Biology and Medicine, Department of Molecular Biology, Cell Biology and Biochemistry, Providence, Rhode Island 02912, USA
| | - Cinzia Casella
- Brown University Division of Biology and Medicine, Department of Molecular Biology, Cell Biology and Biochemistry, Providence, Rhode Island 02912, USA
| | - Susan A Gerbi
- Brown University Division of Biology and Medicine, Department of Molecular Biology, Cell Biology and Biochemistry, Providence, Rhode Island 02912, USA
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31
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Andorf CM, Kopylov M, Dobbs D, Koch KE, Stroupe ME, Lawrence CJ, Bass HW. G-Quadruplex (G4) Motifs in the Maize (Zea mays L.) Genome Are Enriched at Specific Locations in Thousands of Genes Coupled to Energy Status, Hypoxia, Low Sugar, and Nutrient Deprivation. J Genet Genomics 2014; 41:627-47. [DOI: 10.1016/j.jgg.2014.10.004] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2014] [Revised: 10/16/2014] [Accepted: 10/24/2014] [Indexed: 02/07/2023]
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32
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Sherstyuk VV, Shevchenko AI, Zakian SM. Epigenetic landscape for initiation of DNA replication. Chromosoma 2013; 123:183-99. [PMID: 24337246 DOI: 10.1007/s00412-013-0448-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2013] [Revised: 11/27/2013] [Accepted: 12/02/2013] [Indexed: 02/07/2023]
Abstract
The key genetic process of DNA replication is initiated at specific sites referred to as replication origins. In eukaryotes, origins of DNA replication are not specified by a defined nucleotide sequence. Recent studies have shown that the structural context and topology of DNA sequence, chromatin features, and its transcriptional activity play an important role in origin choice. During differentiation and development, significant changes in chromatin organization and transcription occur, influencing origin activity and choice. In the last few years, a number of different genome-wide studies have broadened the understanding of replication origin regulation. In this review, we discuss the epigenetic factors and mechanisms that modulate origin choice and firing.
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Affiliation(s)
- Vladimir V Sherstyuk
- Russian Academy of Sciences, Siberian Branch, Institute of Cytology and Genetics, pr. Akad. Lavrentieva 10, Novosibirsk, 630090, Russia
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Belan E. LINEs of evidence: noncanonical DNA replication as an epigenetic determinant. Biol Direct 2013; 8:22. [PMID: 24034780 PMCID: PMC3868326 DOI: 10.1186/1745-6150-8-22] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 09/06/2013] [Indexed: 12/17/2022] Open
Abstract
LINE-1 (L1) retrotransposons are repetitive elements in mammalian genomes. They are
capable of synthesizing DNA on their own RNA templates by harnessing reverse
transcriptase (RT) that they encode. Abundantly expressed full-length L1s and their
RT are found to globally influence gene expression profiles, differentiation state,
and proliferation capacity of early embryos and many types of cancer, albeit by yet
unknown mechanisms. They are essential for the progression of early development and
the establishment of a cancer-related undifferentiated state. This raises important
questions regarding the functional significance of L1 RT in these cell systems.
Massive nuclear L1-linked reverse transcription has been shown to occur in mouse
zygotes and two-cell embryos, and this phenomenon is purported to be DNA replication
independent. This review argues against this claim with the goal of understanding the
nature of this phenomenon and the role of L1 RT in early embryos and cancers.
Available L1 data are revisited and integrated with relevant findings accumulated in
the fields of replication timing, chromatin organization, and epigenetics, bringing
together evidence that strongly supports two new concepts. First, noncanonical
replication of a portion of genomic full-length L1s by means of L1 RNP-driven reverse
transcription is proposed to co-exist with DNA polymerase-dependent replication of
the rest of the genome during the same round of DNA replication in embryonic and
cancer cell systems. Second, the role of this mechanism is thought to be epigenetic;
it might promote transcriptional competence of neighboring genes linked to
undifferentiated states through the prevention of tethering of involved L1s to the
nuclear periphery. From the standpoint of these concepts, several hitherto
inexplicable phenomena can be explained. Testing methods for the model are
proposed.
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Affiliation(s)
- Ekaterina Belan
- Genetics Laboratory, Royal University Hospital, Saskatoon, SK S7N 0W8, Canada.
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34
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Abstract
Recent experiments provide fascinating examples of how G4 DNA and G4 RNA structures—aka quadruplexes—may contribute to normal biology and to genomic pathologies. Quadruplexes are transient and therefore difficult to identify directly in living cells, which initially caused skepticism regarding not only their biological relevance but even their existence. There is now compelling evidence for functions of some G4 motifs and the corresponding quadruplexes in essential processes, including initiation of DNA replication, telomere maintenance, regulated recombination in immune evasion and the immune response, control of gene expression, and genetic and epigenetic instability. Recognition and resolution of quadruplex structures is therefore an essential component of genome biology. We propose that G4 motifs and structures that participate in key processes compose the G4 genome, analogous to the transcriptome, proteome, or metabolome. This is a new view of the genome, which sees DNA as not only a simple alphabet but also a more complex geography. The challenge for the future is to systematically identify the G4 motifs that form quadruplexes in living cells and the features that confer on specific G4 motifs the ability to function as structural elements.
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35
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Baral A, Kumar P, Pathak R, Chowdhury S. Emerging trends in G-quadruplex biology – role in epigenetic and evolutionary events. MOLECULAR BIOSYSTEMS 2013; 9:1568-75. [DOI: 10.1039/c3mb25492e] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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36
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Beaume N, Pathak R, Yadav VK, Kota S, Misra HS, Gautam HK, Chowdhury S. Genome-wide study predicts promoter-G4 DNA motifs regulate selective functions in bacteria: radioresistance of D. radiodurans involves G4 DNA-mediated regulation. Nucleic Acids Res 2012; 41:76-89. [PMID: 23161683 PMCID: PMC3592403 DOI: 10.1093/nar/gks1071] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
A remarkable number of guanine-rich sequences with potential to adopt non-canonical secondary structures called G-quadruplexes (or G4 DNA) are found within gene promoters. Despite growing interest, regulatory role of quadruplex DNA motifs in intrinsic cellular function remains poorly understood. Herein, we asked whether occurrence of potential G4 (PG4) DNA in promoters is associated with specific function(s) in bacteria. Using a normalized promoter-PG4-content (PG4P) index we analysed >60 000 promoters in 19 well-annotated species for (a) function class(es) and (b) gene(s) with enriched PG4P. Unexpectedly, PG4-associated functional classes were organism specific, suggesting that PG4 motifs may impart specific function to organisms. As a case study, we analysed radioresistance. Interestingly, unsupervised clustering using PG4P of 21 genes, crucial for radioresistance, grouped three radioresistant microorganisms including Deinococcus radiodurans. Based on these predictions we tested and found that in presence of nanomolar amounts of the intracellular quadruplex-binding ligand N-methyl mesoporphyrin (NMM), radioresistance of D. radiodurans was attenuated by ∼60%. In addition, important components of the RecF recombinational repair pathway recA, recF, recO, recR and recQ genes were found to harbour promoter-PG4 motifs and were also down-regulated in presence of NMM. Together these results provide first evidence that radioresistance may involve G4 DNA-mediated regulation and support the rationale that promoter-PG4s influence selective functions.
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Affiliation(s)
- Nicolas Beaume
- GNR Knowledge Centre for Genome Informatics, Division of Comparative Genomics, Institute of Genomics and Integrative Biology, CSIR, Mall Road, Delhi 110 007, India
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Unraveling cell type-specific and reprogrammable human replication origin signatures associated with G-quadruplex consensus motifs. Nat Struct Mol Biol 2012; 19:837-44. [PMID: 22751019 DOI: 10.1038/nsmb.2339] [Citation(s) in RCA: 295] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 06/01/2012] [Indexed: 11/08/2022]
Abstract
DNA replication is highly regulated, ensuring faithful inheritance of genetic information through each cell cycle. In metazoans, this process is initiated at many thousands of DNA replication origins whose cell type-specific distribution and usage are poorly understood. We exhaustively mapped the genome-wide location of replication origins in human cells using deep sequencing of short nascent strands and identified ten times more origin positions than we expected; most of these positions were conserved in four different human cell lines. Furthermore, we identified a consensus G-quadruplex-forming DNA motif that can predict the position of DNA replication origins in human cells, accounting for their distribution, usage efficiency and timing. Finally, we discovered a cell type-specific reprogrammable signature of cell identity that was revealed by specific efficiencies of conserved origin positions and not by the selection of cell type-specific subsets of origins.
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38
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Halder R, Riou JF, Teulade-Fichou MP, Frickey T, Hartig JS. Bisquinolinium compounds induce quadruplex-specific transcriptome changes in HeLa S3 cell lines. BMC Res Notes 2012; 5:138. [PMID: 22414013 PMCID: PMC3375199 DOI: 10.1186/1756-0500-5-138] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Accepted: 03/13/2012] [Indexed: 05/02/2023] Open
Abstract
Background Guanosine rich sequences capable of forming G-quadruplex (G4) motifs are enriched near the gene transcription start site (TSS) in the human genome. When probed at the single gene level, G-quadruplex motifs residing in promoter regions show substantial effects on gene transcription. Moreover, further changes in transcription levels are noticed when G4-motifs are targeted with G-quadruplex-specific small molecules. Results Global studies concerning general changes of the transcriptome via targeting promoter-based G-quadruplex motifs are very limited and have so far only been carried out with compounds displaying weak selectivity for quadruplex sequences. Here we utilize two G-quadruplex-specific bisquinolinium derivatives PhenDC3 and 360A and investigate their effects on the expression of the HeLa S3 transcriptome. Our results show wide-spread changes in the transcriptome with specificity for genes with G-quadruplex motifs near their transcription start sites (TSS). Using real-time PCR we further confirmed the specificity of PhenDC3 and 360A as potent molecules to target G-quadruplex-regulated genes. Conclusions Specific effects on quadruplex-containing genes have been observed utilizing whole-transcriptome analysis upon treatment of cultured cells with quadruplex-selective bisquinolinium compounds.
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Affiliation(s)
- Rashi Halder
- Department of Chemistry and Konstanz Research School Chemical Biology (KoRS-CB), University of Konstanz, Universitätsstraße 10, Konstanz, Germany
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Halder K, Benzler M, Hartig JS. Reporter assays for studying quadruplex nucleic acids. Methods 2012; 57:115-21. [PMID: 22388183 DOI: 10.1016/j.ymeth.2012.02.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2011] [Revised: 02/13/2012] [Accepted: 02/14/2012] [Indexed: 11/25/2022] Open
Abstract
DNA and RNA G-quadruplexes have gained increasing attention due to their potential role in a wide range of biological functions. The majority of functional studies characterize the influence of quadruplexes in gene expression including transcription and translation. Many of these studies have used reporter assays to elucidate the effect of quadruplexes at certain positions in promoters and untranslated mRNA regions (UTRs). Reporter assays are the preferred method to ascertain the biological function of DNA or RNA G-quadruplexes intracellularly due to their ready availability, fast cloning and experimental setup and reproducibility. Moreover, these reporter assays are also helpful to compare or screen for selectivity and efficacy of small molecules that target DNA and RNA G-quadruplexes in the cellular context. Here we briefly discuss various aspects of reporter assays followed by a review of available studies using reporter assays to understand the role and functions of DNA and RNA quadruplexes in gene expression.
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Affiliation(s)
- Kangkan Halder
- Department of Chemistry and Konstanz Research School Chemical Biology (KoRS-CB), University of Konstanz, 78457 Konstanz, Germany
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Baral A, Kumar P, Halder R, Mani P, Yadav VK, Singh A, Das SK, Chowdhury S. Quadruplex-single nucleotide polymorphisms (Quad-SNP) influence gene expression difference among individuals. Nucleic Acids Res 2012; 40:3800-11. [PMID: 22238381 PMCID: PMC3351168 DOI: 10.1093/nar/gkr1258] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Non-canonical guanine quadruplex structures are not only predominant but also conserved among bacterial and mammalian promoters. Moreover recent findings directly implicate quadruplex structures in transcription. These argue for an intrinsic role of the structural motif and thereby posit that single nucleotide polymorphisms (SNP) that compromise the quadruplex architecture could influence function. To test this, we analysed SNPs within quadruplex motifs (Quad-SNP) and gene expression in 270 individuals across four populations (HapMap) representing more than 14,500 genotypes. Findings reveal significant association between quadruplex-SNPs and expression of the corresponding gene in individuals (P < 0.0001). Furthermore, analysis of Quad-SNPs obtained from population-scale sequencing of 1000 human genomes showed relative selection bias against alteration of the structural motif. To directly test the quadruplex-SNP-transcription connection, we constructed a reporter system using the RPS3 promoter-remarkable difference in promoter activity in the 'quadruplex-destabilized' versus 'quadruplex-intact' promoter was noticed. As a further test, we incorporated a quadruplex motif or its disrupted counterpart within a synthetic promoter reporter construct. The quadruplex motif, and not the disrupted-motif, enhanced transcription in human cell lines of different origin. Together, these findings build direct support for quadruplex-mediated transcription and suggest quadruplex-SNPs may play significant role in mechanistically understanding variations in gene expression among individuals.
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Affiliation(s)
- Aradhita Baral
- Proteomics and Structural Biology Unit, Institute of Genomics and Integrative Biology, CSIR, Mall Road, Delhi 110 007, India
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Kumar P, Yadav VK, Baral A, Kumar P, Saha D, Chowdhury S. Zinc-finger transcription factors are associated with guanine quadruplex motifs in human, chimpanzee, mouse and rat promoters genome-wide. Nucleic Acids Res 2011; 39:8005-16. [PMID: 21729868 PMCID: PMC3185432 DOI: 10.1093/nar/gkr536] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Function of non-B DNA structures are poorly understood though several bioinformatics studies predict role of the G-quadruplex DNA structure in transcription. Earlier, using transcriptome profiling we found evidence of widespread G-quadruplex-mediated gene regulation. Herein, we asked whether potential G-quadruplex (PG4) motifs associate with transcription factors (TF). This was analyzed using 220 position weight matrices [designated as transcription factor binding sites (TFBS)], representing 187 unique TF, in >75 000 genes in human, chimpanzee, mouse and rat. Results show binding sites of nine TFs, including that of AP-2, SP1, MAZ and VDR, occurred significantly within 100 bases of the PG4 motif (P < 1.24E-10). PG4–TFBS combinations were conserved in ‘orthologously’ related promoters across all four organisms and were associated with >850 genes in each genome. Remarkably, seven of the nine TFs were zinc-finger binding proteins indicating a novel characteristic of PG4 motifs. To test these findings, transcriptome profiles from human cell lines treated with G-quadruplex-specific molecules were used; 66 genes were significantly differentially expressed across both cell-types, which also harbored conserved PG4 motifs along with one/more of the nine TFBS. In addition, genes regulated by PG4–TFBS combinations were found to be co-regulated in human tissues, further emphasizing the regulatory significance of the associations.
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Affiliation(s)
- Pankaj Kumar
- GNR Knowledge Centre for Genome Informatics, Institute of Genomics and Integrative Biology, CSIR, Mall Road, Delhi 110 007, India
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DNA secondary structures and epigenetic determinants of cancer genome evolution. Nat Struct Mol Biol 2011; 18:950-5. [PMID: 21725294 DOI: 10.1038/nsmb.2089] [Citation(s) in RCA: 181] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2010] [Accepted: 05/04/2011] [Indexed: 12/16/2022]
Abstract
An unstable genome is a hallmark of many cancers. It is unclear, however, whether some mutagenic features driving somatic alterations in cancer are encoded in the genome sequence and whether they can operate in a tissue-specific manner. We performed a genome-wide analysis of 663,446 DNA breakpoints associated with somatic copy-number alterations (SCNAs) from 2,792 cancer samples classified into 26 cancer types. Many SCNA breakpoints are spatially clustered in cancer genomes. We observed a significant enrichment for G-quadruplex sequences (G4s) in the vicinity of SCNA breakpoints and established that SCNAs show a strand bias consistent with G4-mediated structural alterations. Notably, abnormal hypomethylation near G4s-rich regions is a common signature for many SCNA breakpoint hotspots. We propose a mechanistic hypothesis that abnormal hypomethylation in genomic regions enriched for G4s acts as a mutagenic factor driving tissue-specific mutational landscapes in cancer.
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Halder K, Largy E, Benzler M, Teulade-Fichou MP, Hartig JS. Efficient Suppression of Gene Expression by Targeting 5′-UTR-Based RNA Quadruplexes with Bisquinolinium Compounds. Chembiochem 2011; 12:1663-8. [DOI: 10.1002/cbic.201100228] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Indexed: 12/30/2022]
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Abstract
G-quadruplexes are four-stranded DNA structures that are over-represented in gene promoter regions and are viewed as emerging therapeutic targets in oncology, as transcriptional repression of oncogenes through stabilization of these structures could be a novel anticancer strategy. Many gene promoter G-quadruplexes have physicochemical properties and structural characteristics that might make them druggable, and their structural diversity suggests that a high degree of selectivity might be possible. Here, we describe the evidence for G-quadruplexes in gene promoters and discuss their potential as therapeutic targets, as well as progress in the development of strategies to harness this potential through intervention with small-molecule ligands.
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Abstract
Opposed to DNA quadruplex sequences, RNA quadruplexes are still less well characterized. On the other hand, RNA quadruplexes are found to be at least as stable as their DNA counterparts. They show the same dependence on metal ions but seem to be much more restricted with respect to the adopted conformations. Other than DNA, which is mostly found to be double-stranded inside cells, RNAs are produced during transcription without its complementary sequence. The absence of a second strand that is able to hybridize and form a duplex makes the folding of RNA quadruplexes a likely event of intramolecular structure formation. Consequently, the formation of RNA quadruplexes in cellular RNAs has recently been suggested and the study of their influence and potential roles in cellular processes has just started. Here we give an overview of the RNA quadruplex field, summarizing issues such as structures, stabilities, and anticipated roles of these interesting four-stranded, guanosine-rich sequences.
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Affiliation(s)
- Kangkan Halder
- Department of Chemistry, University of Konstanz, Universitätsstrasse 10, D-78457 Konstanz, Germany
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Micheli E, Martufi M, Cacchione S, De Santis P, Savino M. Self-organization of G-quadruplex structures in the hTERT core promoter stabilized by polyaminic side chain perylene derivatives. Biophys Chem 2010; 153:43-53. [PMID: 21036459 DOI: 10.1016/j.bpc.2010.10.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2010] [Revised: 10/05/2010] [Accepted: 10/05/2010] [Indexed: 01/05/2023]
Abstract
hTERT core promoter regulates telomerase transcription in human cells, thus its structural features are of large interest. We have found that the G-rich hTERT core promoter region, corresponding to the major DNase I hypersensitive site in chromatin organization, contains nine putative G-quadruplex forming sequences (PQS) and is unfavorable for nucleosome formation. Here we show that four PQS are effectively able to form stable parallel intramolecular G-quadruplexes, using PAGE and CD spectroscopy analysis. The PQS-region, as a whole, appears to be organized in three self-interacting G-quadruplexes, probably giving rise to a helicoidal superstructure, as shown by CD and polymerase stop assay. POL-HPDI drugs, that we previously found useful in selectively stabilizing telomeric G-quadruplex, are able to stabilize both the single intramolecular G-quadruplex and the PQS-region superstructure. The features of their induced CD spectra suggest that POL-HPDIs bind to single G-quadruplexes and to whole PQS-region superstructure, mainly by end-stacking interactions.
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Affiliation(s)
- Emanuela Micheli
- Dipartimento di Biologia e Biotecnologie, "Sapienza" Università di Roma, Italy
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Halder R, Halder K, Sharma P, Garg G, Sengupta S, Chowdhury S. Guanine quadruplex DNA structure restricts methylation of CpG dinucleotides genome-wide. MOLECULAR BIOSYSTEMS 2010; 6:2439-47. [PMID: 20877913 DOI: 10.1039/c0mb00009d] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Cytosine methylation in mammals is important for epigenetic control of the transcriptome. Although altered methylation is frequently encountered in disease situations, particularly cancer, the relationship between genome-wide methylation and DNA structure is poorly understood. It is now evident that alternative DNA forms are functionally relevant in replication, recombination and transcription. Herein, we researched the role of alternative DNA structure in cytosine methylation using quadruplex DNA as a case study. Our findings from analysis of 2.1 million CpGs in humans, across 12 tissues from the Human Epigenome Project (HEP), revealed a striking correlation within each tissue: CpGs with low methylation were enriched (P = 5.24E(-20)) whereas CpGs with high methylation were relatively depleted (P = 9.28E(-15)), within quadruplex-forming regions. This was further substantiated on considering 1.07E(8) methylcytosines from genome-wide sequencing within embryonic stem cells and differentiated fibroblasts. To further test the predictions we experimentally determined methylation in >600,000 CpGs across 18 individuals using bisulfite mapping and found significantly low methylation of CpGs within quadruplex-forming regions (P = 1.36E(-08)). Together, these suggest the role of guanine-quadruplexes in CpG methylation and directly impact our understanding of the inter-relationship between DNA conformation and global cytosine methylation.
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Affiliation(s)
- Rashi Halder
- G.N.R. Knowledge Centre for Genome Informatics, Institute of Genomics and Integrative Biology, CSIR, Mall Road, Delhi 110 007, India
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Basundra R, Kumar A, Amrane S, Verma A, Phan AT, Chowdhury S. A novel G-quadruplex motif modulates promoter activity of human thymidine kinase 1. FEBS J 2010; 277:4254-64. [DOI: 10.1111/j.1742-4658.2010.07814.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Johnson JE, Cao K, Ryvkin P, Wang LS, Johnson FB. Altered gene expression in the Werner and Bloom syndromes is associated with sequences having G-quadruplex forming potential. Nucleic Acids Res 2009; 38:1114-22. [PMID: 19966276 PMCID: PMC2831322 DOI: 10.1093/nar/gkp1103] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The human Werner and Bloom syndromes (WS and BS) are caused by deficiencies in the WRN and BLM RecQ helicases, respectively. WRN, BLM and their Saccharomyces cerevisiae homologue Sgs1, are particularly active in vitro in unwinding G-quadruplex DNA (G4-DNA), a family of non-canonical nucleic acid structures formed by certain G-rich sequences. Recently, mRNA levels from loci containing potential G-quadruplex-forming sequences (PQS) were found to be preferentially altered in sgs1Δ mutants, suggesting that G4-DNA targeting by Sgs1 directly affects gene expression. Here, we extend these findings to human cells. Using microarrays to measure mRNAs obtained from human fibroblasts deficient for various RecQ family helicases, we observe significant associations between loci that are upregulated in WS or BS cells and loci that have PQS. No such PQS associations were observed for control expression datasets, however. Furthermore, upregulated genes in WS and BS showed no or dramatically reduced associations with sequences similar to PQS but that have considerably reduced potential to form intramolecular G4-DNA. These findings indicate that, like Sgs1, WRN and BLM can regulate transcription globally by targeting G4-DNA.
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Affiliation(s)
- Jay E Johnson
- Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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Halder K, Wieland M, Hartig JS. Predictable suppression of gene expression by 5'-UTR-based RNA quadruplexes. Nucleic Acids Res 2009; 37:6811-7. [PMID: 19740765 PMCID: PMC2777418 DOI: 10.1093/nar/gkp696] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Four-stranded DNA and RNA quadruplexes or G4 motifs are non-B DNA conformations that are presumed to form in vivo, although only few explicit evidence has been reported. Using bioinformatics the presence of putative DNA G-quadruplexes within critical promoter regions has been demonstrated and a regulatory role in transcription has been suspected. However, in genomic DNA the presence of the complementary strand interferes with the potential to form a quadruplex motif. Contrarily RNA G4 motifs have no such limitation and consequently strong interference with gene expression is suspected. Nevertheless, experimental evidence is scarce. Here we show a well-defined structure–function relationship of synthetic quadruplex sequences in 5′-UTRs in multiple mammalian cell-lines. We establish a universal ‘translational suppressor’ effect of these motifs on gene expression at the translational level and show for the first time that specific features such as loop-length and the number of ‘GGG’-repeats further determine the suppressive impact. Moreover, a consistent and predictable repression of gene expression is observed for naturally occurring RNA G4 motifs, augmenting the functional relevance of these unusual nucleic acid structures.
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Affiliation(s)
- Kangkan Halder
- Department of Chemistry, Konstanz Research School Chemical Biology and Zukunftskolleg, University of Konstanz, Universitätsstr 10, 78457 Konstanz, Germany
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