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Qin G, Liu Z, Yang J, Liao X, Zhao C, Ren J, Qu X. Targeting specific DNA G-quadruplexes with CRISPR-guided G-quadruplex-binding proteins and ligands. Nat Cell Biol 2024; 26:1212-1224. [PMID: 38961283 DOI: 10.1038/s41556-024-01448-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Accepted: 05/30/2024] [Indexed: 07/05/2024]
Abstract
Despite the demonstrated importance of DNA G-quadruplexes (G4s) in health and disease, technologies to readily manipulate specific G4 folding for functional analysis and therapeutic purposes are lacking. Here we employ G4-stabilizing protein/ligand in conjunction with CRISPR to selectively facilitate single or multiple targeted G4 folding within specific genomic loci. We demonstrate that fusion of nucleolin with a catalytically inactive Cas9 can specifically stabilize G4s in the promoter of oncogene MYC and muscle-associated gene Itga7 as well as telomere G4s, leading to cell proliferation arrest, inhibition of myoblast differentiation and cell senescence, respectively. Furthermore, CRISPR can confer intra-G4 selectivity to G4-binding compounds pyridodicarboxamide and pyridostatin. Compared with traditional G4 ligands, CRISPR-guided biotin-conjugated pyridodicarboxamide enables a more precise investigation into the biological functionality of de novo G4s. Our study provides insights that will enhance understanding of G4 functions and therapeutic interventions.
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Affiliation(s)
- Geng Qin
- Laboratory of Chemical Biology and State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, P. R. China
- University of Science and Technology of China, Hefei, P. R. China
| | - Zhenqi Liu
- Laboratory of Chemical Biology and State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, P. R. China
- University of Science and Technology of China, Hefei, P. R. China
| | - Jie Yang
- Laboratory of Chemical Biology and State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, P. R. China
- University of Science and Technology of China, Hefei, P. R. China
| | - Xiaofeng Liao
- Laboratory of Chemical Biology and State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, P. R. China
- University of Science and Technology of China, Hefei, P. R. China
| | - Chuanqi Zhao
- Laboratory of Chemical Biology and State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, P. R. China
- University of Science and Technology of China, Hefei, P. R. China
| | - Jinsong Ren
- Laboratory of Chemical Biology and State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, P. R. China
- University of Science and Technology of China, Hefei, P. R. China
| | - Xiaogang Qu
- Laboratory of Chemical Biology and State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, P. R. China.
- University of Science and Technology of China, Hefei, P. R. China.
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2
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Celebi Torabfam G, K. Demir G, Demir D. Quantum tunneling time delay investigation of [Formula: see text] ion in human telomeric G-quadruplex systems. J Biol Inorg Chem 2023; 28:213-224. [PMID: 36656371 PMCID: PMC9851595 DOI: 10.1007/s00775-022-01982-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Accepted: 10/24/2022] [Indexed: 01/20/2023]
Abstract
Guanine-rich quadruplex DNA (G-quadruplex) is of interest both in cell biology and nanotechnology. Its biological functions necessitate a G-quadruplex to be stabilized against escape of the monovalent metal cations. The potassium ion ([Formula: see text]) is particularly important as it experiences a potential energy barrier while it enters and exits the G-quadruplex systems which are normally found in human telomere. In the present work, we analyzed the time it takes for the [Formula: see text] cations to get in and out of the G-quadruplex. Our time estimate is based on entropic tunneling time-a time formula which gave biologically relevant results for DNA point mutation by proton tunneling. The potential energy barrier experienced by [Formula: see text] ions is determined from a quantum mechanical simulation study, Schrodinger equation is solved using MATLAB, and the computed eigenfunctions and eigenenergies are used in the entropic tunneling time formula to compute the time delay and charge accumulation rate during the tunneling of [Formula: see text] in G-quadruplex. The computations have shown that ion tunneling takes picosecond times. In addition, average [Formula: see text] accumulation rate is found to be in the picoampere range. Our results show that time delay during the [Formula: see text] ion tunneling is in the ballpark of the conformational transition times in biological systems, and it could be an important parameter for understanding its biological role in human DNA as well as for the possible applications in biotechnology. To our knowledge, for the first time in the literature, time delay during the ion tunneling from and into G-quadruplexes is computed.
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Affiliation(s)
- Gizem Celebi Torabfam
- Faculty of Engineering and Natural Sciences, Sabancı University, Tuzla, 34956 Istanbul, Turkey
| | - Güleser K. Demir
- Department of Electrical and Electronics Engineering, Dokuz Eylül University, Buca, 35390 İzmir, Turkey
| | - Durmuş Demir
- Faculty of Engineering and Natural Sciences, Sabancı University, Tuzla, 34956 Istanbul, Turkey
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3
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Monsen RC, DeLeeuw LW, Dean W, Gray R, Chakravarthy S, Hopkins J, Chaires J, Trent J. Long promoter sequences form higher-order G-quadruplexes: an integrative structural biology study of c-Myc, k-Ras and c-Kit promoter sequences. Nucleic Acids Res 2022; 50:4127-4147. [PMID: 35325198 PMCID: PMC9023277 DOI: 10.1093/nar/gkac182] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 03/03/2022] [Accepted: 03/21/2022] [Indexed: 12/15/2022] Open
Abstract
We report on higher-order G-quadruplex structures adopted by long promoter sequences obtained by an iterative integrated structural biology approach. Our approach uses quantitative biophysical tools (analytical ultracentrifugation, small-angle X-ray scattering, and circular dichroism spectroscopy) combined with modeling and molecular dynamics simulations, to derive self-consistent structural models. The formal resolution of our approach is 18 angstroms, but in some cases structural features of only a few nucleotides can be discerned. We report here five structures of long (34-70 nt) wild-type sequences selected from three cancer-related promoters: c-Myc, c-Kit and k-Ras. Each sequence studied has a unique structure. Three sequences form structures with two contiguous, stacked, G-quadruplex units. One longer sequence from c-Myc forms a structure with three contiguous stacked quadruplexes. A longer c-Kit sequence forms a quadruplex-hairpin structure. Each structure exhibits interfacial regions between stacked quadruplexes or novel loop geometries that are possible druggable targets. We also report methodological advances in our integrated structural biology approach, which now includes quantitative CD for counting stacked G-tetrads, DNaseI cleavage for hairpin detection and SAXS model refinement. Our results suggest that higher-order quadruplex assemblies may be a common feature within the genome, rather than simple single quadruplex structures.
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Affiliation(s)
- Robert C Monsen
- UofL Health Brown Cancer Center, University of Louisville, Louisville, KY 40202, USA
| | - Lynn W DeLeeuw
- UofL Health Brown Cancer Center, University of Louisville, Louisville, KY 40202, USA
| | - William L Dean
- UofL Health Brown Cancer Center, University of Louisville, Louisville, KY 40202, USA
| | - Robert D Gray
- UofL Health Brown Cancer Center, University of Louisville, Louisville, KY 40202, USA
| | - Srinivas Chakravarthy
- The Biophysics Collaborative Access Team (BioCAT), Department of Biological, Chemical, and Physical Sciences, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Jesse B Hopkins
- The Biophysics Collaborative Access Team (BioCAT), Department of Biological, Chemical, and Physical Sciences, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Jonathan B Chaires
- UofL Health Brown Cancer Center, University of Louisville, Louisville, KY 40202, USA
- Department of Medicine, University of Louisville, Louisville, KY 40202, USA
- Department of Biochemistry and Molecular Genetics, University of Louisville, Louisville, KY 40202, USA
| | - John O Trent
- UofL Health Brown Cancer Center, University of Louisville, Louisville, KY 40202, USA
- Department of Medicine, University of Louisville, Louisville, KY 40202, USA
- Department of Biochemistry and Molecular Genetics, University of Louisville, Louisville, KY 40202, USA
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4
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Mechanisms of Binding Specificity among bHLH Transcription Factors. Int J Mol Sci 2021; 22:ijms22179150. [PMID: 34502060 PMCID: PMC8431614 DOI: 10.3390/ijms22179150] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Revised: 08/14/2021] [Accepted: 08/18/2021] [Indexed: 12/25/2022] Open
Abstract
The transcriptome of every cell is orchestrated by the complex network of interaction between transcription factors (TFs) and their binding sites on DNA. Disruption of this network can result in many forms of organism malfunction but also can be the substrate of positive natural selection. However, understanding the specific determinants of each of these individual TF-DNA interactions is a challenging task as it requires integrating the multiple possible mechanisms by which a given TF ends up interacting with a specific genomic region. These mechanisms include DNA motif preferences, which can be determined by nucleotide sequence but also by DNA’s shape; post-translational modifications of the TF, such as phosphorylation; and dimerization partners and co-factors, which can mediate multiple forms of direct or indirect cooperative binding. Binding can also be affected by epigenetic modifications of putative target regions, including DNA methylation and nucleosome occupancy. In this review, we describe how all these mechanisms have a role and crosstalk in one specific family of TFs, the basic helix-loop-helix (bHLH), with a very conserved DNA binding domain and a similar DNA preferred motif, the E-box. Here, we compile and discuss a rich catalog of strategies used by bHLH to acquire TF-specific genome-wide landscapes of binding sites.
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Ultrafast excited state dynamics and light-switching of [Ru(phen) 2(dppz)] 2+ in G-quadruplex DNA. Commun Chem 2021; 4:68. [PMID: 36697709 PMCID: PMC9814642 DOI: 10.1038/s42004-021-00507-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Accepted: 04/09/2021] [Indexed: 01/28/2023] Open
Abstract
The triplet metal to ligand charge transfer (3MLCT) luminescence of ruthenium (II) polypyridyl complexes offers attractive imaging properties, specifically towards the development of sensitive and structure-specific DNA probes. However, rapidly-deactivating dark state formation may compete with 3MLCT luminescence depending on different DNA structures. In this work, by combining femtosecond and nanosecond pump-probe spectroscopy, the 3MLCT relaxation dynamics of [Ru(phen)2(dppz)]2+ (phen = 1,10-phenanthroline, dppz = dipyridophenazine) in two iconic G-quadruplexes has been scrutinized. The binding modes of stacking of dppz ligand on the terminal G-quartet fully and partially are clearly identified based on the biexponential decay dynamics of the 3MLCT luminescence at 620 nm. Interestingly, the inhibited dark state channel in ds-DNA is open in G-quadruplex, featuring an ultrafast picosecond depopulation process from 3MLCT to a dark state. The dark state formation rates are found to be sensitive to the content of water molecules in local G-quadruplex structures, indicating different patterns of bound water. The unique excited state dynamics of [Ru(phen)2(dppz)]2+ in G-quadruplex is deciphered, providing mechanistic basis for the rational design of photoactive ruthenium metal complexes in biological applications.
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Kim J, Sahloul S, Orozaliev A, Do VQ, Pham VS, Martins D, Wei X, Levicky R, Song YA. Microfluidic Electrokinetic Preconcentration Chips: Enhancing the detection of nucleic acids and exosomes. IEEE NANOTECHNOLOGY MAGAZINE 2020. [DOI: 10.1109/mnano.2020.2966064] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Lu Y, Dohno C, Nakatani K. A novel naphthyridine tetramer that recognizes tandem G–G mismatches by the formation of an interhelical complex. Chem Commun (Camb) 2020; 56:754-757. [DOI: 10.1039/c9cc08111a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A novel naphthyridine tetramer, p-NCTB, was reported to bind two distal CGGG/CGGG via noncovalent binding forming inter- and intrastrand complexes.
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Affiliation(s)
- Yihuan Lu
- The Institute of Scientific and Industrial Research
- Osaka University
- Ibaraki 567-0047
- Japan
| | - Chikara Dohno
- The Institute of Scientific and Industrial Research
- Osaka University
- Ibaraki 567-0047
- Japan
| | - Kazuhiko Nakatani
- The Institute of Scientific and Industrial Research
- Osaka University
- Ibaraki 567-0047
- Japan
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8
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Kolesnikova S, Curtis EA. Structure and Function of Multimeric G-Quadruplexes. Molecules 2019; 24:molecules24173074. [PMID: 31450559 PMCID: PMC6749722 DOI: 10.3390/molecules24173074] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Revised: 08/21/2019] [Accepted: 08/22/2019] [Indexed: 11/16/2022] Open
Abstract
G-quadruplexes are noncanonical nucleic acid structures formed from stacked guanine tetrads. They are frequently used as building blocks and functional elements in fields such as synthetic biology and also thought to play widespread biological roles. G-quadruplexes are often studied as monomers, but can also form a variety of higher-order structures. This increases the structural and functional diversity of G-quadruplexes, and recent evidence suggests that it could also be biologically important. In this review, we describe the types of multimeric topologies adopted by G-quadruplexes and highlight what is known about their sequence requirements. We also summarize the limited information available about potential biological roles of multimeric G-quadruplexes and suggest new approaches that could facilitate future studies of these structures.
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Affiliation(s)
- Sofia Kolesnikova
- The Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, 166 10 Prague, Czech Republic
- Department of Biochemistry and Microbiology, University of Chemistry and Technology, 166 28 Prague, Czech Republic
| | - Edward A Curtis
- The Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, 166 10 Prague, Czech Republic.
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9
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Bulged and Canonical G-Quadruplex Conformations Determine NDPK Binding Specificity. Molecules 2019; 24:molecules24101988. [PMID: 31126138 PMCID: PMC6572678 DOI: 10.3390/molecules24101988] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 05/20/2019] [Accepted: 05/22/2019] [Indexed: 11/17/2022] Open
Abstract
Guanine-rich DNA strands can adopt tertiary structures known as G-quadruplexes (G4s) that form when Hoogsteen base-paired guanines assemble as planar stacks, stabilized by a central cation like K+. In this study, we investigated the conformational heterogeneity of a G-rich sequence from the 5′ untranslated region of the Zea mayshexokinase4 gene. This sequence adopted an extensively polymorphic G-quadruplex, including non-canonical bulged G-quadruplex folds that co-existed in solution. The nature of this polymorphism depended, in part, on the incorporation of different sets of adjacent guanines into a quadruplex core, which permitted the formation of the different conformations. Additionally, we showed that the maize homolog of the human nucleoside diphosphate kinase (NDPK) NM23-H2 protein—ZmNDPK1—specifically recognizes and promotes formation of a subset of these conformations. Heteromorphic G-quadruplexes play a role in microorganisms’ ability to evade the host immune system, so we also discuss how the underlying properties that determine heterogeneity of this sequence could apply to microorganism G4s.
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10
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Abstract
G-quadruplexes (G4s) have become one of the most exciting nucleic acid secondary structures. A noncanonical, four-stranded structure formed in guanine-rich DNA and RNA sequences, G-quadruplexes can readily form under physiologically relevant conditions and are globularly folded structures. DNA is widely recognized as a double-helical structure essential in genetic information storage. However, only ~3% of the human genome is expressed in protein; RNA and DNA may form noncanonical secondary structures that are functionally important. G-quadruplexes are one such example which have gained considerable attention for their formation and regulatory roles in biologically significant regions, such as human telomeres, oncogene-promoter regions, replication initiation sites, and 5'- and 3'-untranslated region (UTR) of mRNA. They are shown to be a regulatory motif in a number of critical cellular processes including gene transcription, translation, replication, and genomic stability. G-quadruplexes are also found in nonhuman genomes, particularly those of human pathogens. Therefore, G-quadruplexes have emerged as a new class of molecular targets for drug development. In addition, there is considerable interest in the use of G-quadruplexes for biomaterials, biosensors, and biocatalysts. The First International Meeting on Quadruplex DNA was held in 2007, and the G-quadruplex field has been growing dramatically over the last decade. The methods used to study G-quadruplexes have been essential to the rapid progress in our understanding of this exciting nucleic acid secondary structure.
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Affiliation(s)
- Danzhou Yang
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University, Purdue Center for Cancer Research, Purdue Institute for Drug Discovery, West Lafayette, IN USA
| | - Clement Lin
- Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University, West Lafayette, IN USA
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Myoblast Myogenic Differentiation but Not Fusion Process Is Inhibited via MyoD Tetraplex Interaction. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2018; 2018:7640272. [PMID: 29854094 PMCID: PMC5964432 DOI: 10.1155/2018/7640272] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/10/2017] [Revised: 03/17/2018] [Accepted: 04/04/2018] [Indexed: 12/11/2022]
Abstract
The presence of tetraplex structures in the promoter region of the myogenic differentiation 1 gene (MyoD1) was investigated with a specific tetraplex-binding porphyrin (TMPyP4), to test its influence on the expression of MyoD1 itself and downstream-regulated genes during myogenic differentiation. TMPyP4-exposed C2C12 myoblasts, blocking MyoD1 transcription, proliferated reaching confluence and fused forming elongated structures, resembling myotubes, devoid of myosin heavy chain 3 (MHC) expression. Besides lack of MHC, upon MyoD1 inhibition, other myogenic gene expressions were also affected in treated cells, while untreated control cell culture showed normal myotube formation expressing MyoD1, Myog, MRF4, Myf5, and MHC. Unexpectedly, the myomaker (Mymk) gene expression was not affected upon TMPyP4 exposure during C2C12 myogenic differentiation. At the genomic level, the bioinformatic comparison of putative tetraplex sites found that three tetraplexes in MyoD1 and Myog are highly conserved in mammals, while Mymk and MHC did not show any conserved tetraplexes in the analysed regions. Thus, here, we report for the first time that the inhibition of the MyoD1 promoter function, stabilizing the tetraplex region, affects downstream myogenic genes by blocking their expression, while leaving the expression of Mymk unaltered. These results reveal the existence of two distinct pathways: one leading to cell fusion and one guaranteeing correct myotube differentiation.
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Kaulage MH, Maji B, Pasadi S, Ali A, Bhattacharya S, Muniyappa K. Targeting G-quadruplex DNA structures in the telomere and oncogene promoter regions by benzimidazole‒carbazole ligands. Eur J Med Chem 2018; 148:178-194. [DOI: 10.1016/j.ejmech.2018.01.091] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Revised: 01/17/2018] [Accepted: 01/27/2018] [Indexed: 10/18/2022]
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13
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Cheung LS, Wei X, Martins D, Song YA. Rapid detection of exosomal microRNA biomarkers by electrokinetic concentration for liquid biopsy on chip. BIOMICROFLUIDICS 2018; 12:014104. [PMID: 30867851 PMCID: PMC6404950 DOI: 10.1063/1.5009719] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Accepted: 12/12/2017] [Indexed: 06/09/2023]
Abstract
An ion concentration polarization (ICP)-based electrokinetic concentration device is used for accelerating the surface hybridization reaction between exosomal microRNAs (miRNAs) and morpholinos (MOs) as a synthetic oligo capture probe in the nanomolar concentration range in a microfluidic channel. Compared with standard hybridization at the same concentration, the hybridization time of the miRNA target on MO capture probes could be reduced from ∼24 h to 30 min, with an increase in detection speed by 48 times. This ICP-enhanced hybridization method not only significantly decreases the detection time but also makes workflow simple to use, circumventing use of quantitative reverse transcription polymerase chain reaction or other conventional enzyme-based amplification methods that can cause artifacts.
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Affiliation(s)
- Lucia S Cheung
- Division of Engineering, New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi, United Arab Emirates
| | | | - Diogo Martins
- NOVA Medical School, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisboa, Portugal
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Singh A, Kukreti S. A triple stranded G-quadruplex formation in the promoter region of human myosin β(Myh7) gene. J Biomol Struct Dyn 2017; 36:2773-2786. [PMID: 28927343 DOI: 10.1080/07391102.2017.1374211] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Regulatory regions in human genome, enriched in guanine-rich DNA sequences have the propensity to fold into G-quadruplex structures. On exploring the genome for search of G-tracts, it was interesting to find that promoter of Human Myosin Gene (MYH7) contains a conserved 23-mer G-rich sequence (HM-23). Mutations in this gene are associated with familial cardiomyopathy. Enrichment of MYH7 gene in G-rich sequences could possibly play a critical role in its regulation. We used polyacrylamide gel electrophoresis (PAGE), UV-Thermal denaturation (UV-Tm) and Circular Dichroism (CD), to demonstrate the formation of a G-quadruplex by 23-mer G-rich sequence HM23 in promoter location of MYH7 gene. We observed that the wild G-rich sequence HM23 containing consecutive G5 stretch in two stacks adopt G-quadruplexes of diverse molecularity by involvement of four-strand, three-strand and two-strands with same parallel topology. Interestingly, the mutated sequence in the absence of continuous G5 stretch obstructs the formation of three-stranded G-quadruplex. We demonstrated that continuous G5 stretch is mandatory for the formation of a unique three-stranded G-quadruplex. Presence of various transcription factors (TF) in vicinity of the sequence HM23 leave fair possibility of recognition by TF binding sites, and so modulate gene expression. These findings may add on our understanding about the effect of base change in the formation of varied structural species in similar solution condition. This study may give insight about structural polymorphism arising due to recognition of non-Watson-Crick G-quadruplex structures by cellular proteins and designing structure specific molecules.
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Affiliation(s)
- Anju Singh
- a Nucleic Acids Research Laboratory, Department of Chemistry , University of Delhi , North Campus, Delhi 110007 , India
| | - Shrikant Kukreti
- a Nucleic Acids Research Laboratory, Department of Chemistry , University of Delhi , North Campus, Delhi 110007 , India
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15
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Yan C, Xia X, He J, Ren Z, Xu D, Xiong Y, Zuo B. MyoD Is a Novel Activator of Porcine FIT1 Gene by Interacting with the Canonical E-Box Element during Myogenesis. Int J Mol Sci 2015; 16:25014-30. [PMID: 26492245 PMCID: PMC4632787 DOI: 10.3390/ijms161025014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Revised: 09/21/2015] [Accepted: 10/12/2015] [Indexed: 11/17/2022] Open
Abstract
Fat-induced transcript 1 (FIT1/FITM1) gene is a member of the conserved gene family important for triglyceride-rich lipid droplet accumulation. FIT1 gene displays a similar muscle-specific expression across pigs, mice, and humans. Thus pigs can act as a useful model of many human diseases resulting from misexpression of FIT1 gene. Triglyceride content in skeletal muscle plays a key role in pork meat quality and flavors. An insertion/deletion mutation in porcine FIT1 coding region shows a high correlation with a series of fat traits. To gain better knowledge of the potential role of FIT1 gene in human diseases and the correlations with pork meat quality, our attention is given to the region upstream of the porcine FIT1 coding sequence. We cloned ~1 kb of the 5′-flanking region of porcine FIT1 gene to define the role of this sequence in modulating the myogenic expression. A canonical E-box element that activated porcine FIT1 promoter activity during myogenesis was identified. Further analysis demonstrated that promoter activity was induced by overexpression of MyoD1, which bound to this canonical E-box during C2C12 differentiation. This is the first evidence that FIT1 as the direct novel target of MyoD is involved in muscle development.
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Affiliation(s)
- Chi Yan
- Key Laboratory of Swine Genetics and Breeding of the Ministry of Agriculture, College of Animal Sciences & Technology, Huazhong Agricultural University, Wuhan 430070, China.
| | - Xiaoliang Xia
- Key Laboratory of Swine Genetics and Breeding of the Ministry of Agriculture, College of Animal Sciences & Technology, Huazhong Agricultural University, Wuhan 430070, China.
| | - Junxian He
- Yuguan Agricultural Inc., Shuining 629208, China.
| | - Zhuqing Ren
- Key Laboratory of Swine Genetics and Breeding of the Ministry of Agriculture, College of Animal Sciences & Technology, Huazhong Agricultural University, Wuhan 430070, China.
| | - Dequan Xu
- Key Laboratory of Swine Genetics and Breeding of the Ministry of Agriculture, College of Animal Sciences & Technology, Huazhong Agricultural University, Wuhan 430070, China.
| | - Yuanzhu Xiong
- Key Laboratory of Swine Genetics and Breeding of the Ministry of Agriculture, College of Animal Sciences & Technology, Huazhong Agricultural University, Wuhan 430070, China.
| | - Bo Zuo
- Key Laboratory of Swine Genetics and Breeding of the Ministry of Agriculture, College of Animal Sciences & Technology, Huazhong Agricultural University, Wuhan 430070, China.
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16
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Chen Y, Yang D. Sequence, stability, and structure of G-quadruplexes and their interactions with drugs. CURRENT PROTOCOLS IN NUCLEIC ACID CHEMISTRY 2012; Chapter 17:Unit17.5. [PMID: 22956454 PMCID: PMC3463244 DOI: 10.1002/0471142700.nc1705s50] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Although DNA is most widely known for its ability to store and pass along genetic information, the discovery of G-quadruplex structures has illuminated a new role for DNA in biology. DNA G-quadruplexes are four-stranded globular nucleic acid secondary structures formed in specific G-rich sequences with biological significance, such as human telomeres and oncogene promoters. This review focuses on the unimolecular DNA G-quadruplexes, which can readily form in solution under physiological conditions and are considered to be the most biologically relevant. Available structural data show a great conformational diversity of unimolecular G-quadruplexes, which are amenable to small-molecule drug targeting. The relationships between sequence, structure, and stability of unimolecular DNA G-quadruplexes, as well as the recent progress on interactions with small-molecule compounds and insights into rational design of G-quadruplex-interactive molecules, will be discussed.
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Affiliation(s)
- Yuwei Chen
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, AZ
| | - Danzhou Yang
- College of Pharmacy, The University of Arizona, 1703 E. Mabel St, Tucson, AZ 85721
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, AZ
- BIO5 Institute, The University of Arizona, Tucson, AZ
- Arizona Cancer Center, 1515 N. Campbell Avenue, Tucson, AZ
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17
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Li Z, Tan JH, He JH, Long Y, Ou TM, Li D, Gu LQ, Huang ZS. Disubstituted quinazoline derivatives as a new type of highly selective ligands for telomeric G-quadruplex DNA. Eur J Med Chem 2011; 47:299-311. [PMID: 22104971 DOI: 10.1016/j.ejmech.2011.10.057] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Revised: 10/25/2011] [Accepted: 10/28/2011] [Indexed: 12/12/2022]
Abstract
A series of 2,4-disubstituted quinazoline derivatives found to be a new type of highly selective ligand to bind with telomeric G-quadruplex DNA, and their biological properties were reported for the first time.Their interactions with telomeric G-quadruplex DNA were evaluated by using fluorescence resonance energy transfer (FRET) melting assay, circular dichroism (CD) spectroscopy, surface plasmon resonance (SPR), nuclear magnetic resonance (NMR), and molecular modeling. Our results showed that these derivatives could well recognize G-quadruplex and have high selectivity toward G-quadruplex over duplex DNA. The structure-activity relationships (SARs) study revealed that the disubstitution of quinazoline and the length of the amide side chain were important for its interaction with the G-quadruplex. Furthermore, telomerase inhibition of the quinazoline derivatives and their cellular effects were studied.
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Affiliation(s)
- Zeng Li
- School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, People's Republic of China
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18
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Abstract
DNA G-quadruplexes are DNA secondary structures formed in specific G-rich sequences. DNA sequences that can form G-quadruplexes have been found in regions with biological significance, such as human telomeres and oncogene-promoter regions. DNA G-quadruplexes have recently emerged as a new class of novel molecular targets for anticancer drugs. Recent progress on structural studies of the biologically relevant G-quadruplexes formed in human telomeres and in the promoter regions of human oncogenes will be discussed, as well as recent advances in the design and development of G-quadruplex-interactive drugs. DNA G-quadruplexes can readily form in solution under physiological conditions and are globularly folded nucleic acid structures. The molecular structures of intramolecular G-quadruplexes appear to differ from one another and, therefore, in principle may be differentially regulated and targeted by different proteins and drugs.
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19
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Fu Y, Wang X, Zhang J, Xiao Y, Li W, Wang J. Orderly microaggregates of G-/C-rich oligonucleotides associated with spermine. Biomacromolecules 2011; 12:747-56. [PMID: 21235226 DOI: 10.1021/bm101372h] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Spermine-induced orderly assembling properties of G-/C-rich oligonucleotides are investigated in dilute and crowding conditions. The first time we report that the parallel G-quadruplexes is preferential to condense into anisotropic microaggregates in the presence of spermine, whereas the hybrid-type and the antiparallel G-quadruplexes have no significant interactions with spermine; and spermine can induce the condensation of i-motif C-rich oligonucleotides other than the random coiled C-rich strands. Moreover, the condensation of C-rich oligonucleotides can be reversibly regulated by pH and temperature. G-/C-rich oligonucleotides exhibit the cholesteric liquid crystalline phase at low strand concentration in the presence of spermine under crowding conditions. The results illuminate that the parallel G-quadruplex and i-motifs are probably necessity conformations for G-/C-rich oligonucleotides that involved in the regulation of chromosome organization in living cells.
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Affiliation(s)
- Yan Fu
- Key Laboratory for Green Chemical Technology MOE, Tianjin University, Tianjin 300072, People's Republic of China
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20
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Derecka K, Balkwill GD, Garner TP, Hodgman C, Flint APF, Searle MS. Occurrence of a quadruplex motif in a unique insert within exon C of the bovine estrogen receptor alpha gene (ESR1). Biochemistry 2010; 49:7625-33. [PMID: 20715834 DOI: 10.1021/bi100804f] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The 5' end of exon C of the bovine estrogen receptor alpha gene (bov-ESR1) includes a unique G-rich insert, not found in other closely related mammalian genes, which lies close to both a double E-box transcription factor binding site and the site of a single nucleotide (G/A) polymorphism. Biophysical studies, using CD and UV absorbance measurements, show that this 22 base insert leads to the formation of a family of stable G-quadruplex structures which are unaffected by the G/A polymorphism. Multiplex PCR shows that the region including the G-quadruplex is transcribed into RNA, and studies with a synthetic RNA transcript sequence demonstrated formation of a highly stable parallel-folded quadruplex structure. Luciferase reporter constructs demonstrate that the G-rich sequence reduces rates of translation when present in the 5'-UTR of mRNA transcripts. Mutations (GGG to AAA) that destabilize the quadruplex lead to a 15-fold enhancement of translational efficiency, suggesting that a possible biological role of the insert in exon C of the bov-ESR1 is to regulate translation of this exon.
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Affiliation(s)
- Kamila Derecka
- School of Biosciences, Division of Animal Sciences, University of Nottingham, Sutton Bonington, Leicestershire LE12 5RD, UK
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21
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Li H, Yuan G. Electrospray ionization mass spectrometry probing of formation and recognition of the G-quadruplex in the proximal promoter of the human vascular endothelial growth factor gene. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2010; 24:2030-2034. [PMID: 20552697 DOI: 10.1002/rcm.4613] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The formation of the G-quadruplex of the vascular endothelial growth factor (VEGF) gene was probed by electrospray ionization mass spectrometry (ESI-MS). It found that cations (K(+) and NH(4)(+)), CH(3)OH and pH influence significantly the formation of the G-quadruplex structure. Additionally, a perylene derivative (P3) and polydatin (P4) have shown to be potential G-quadruplex binding agents with structurally specific recognition.
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Affiliation(s)
- Huihui Li
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, Department of Chemical Biology, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
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Du Y, Zhang D, Chen W, Zhang M, Zhou Y, Zhou X. Cationic N-confused porphyrin derivative as a better molecule scaffold for G-quadruplex recognition. Bioorg Med Chem 2010; 18:1111-6. [DOI: 10.1016/j.bmc.2009.12.049] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2009] [Revised: 12/15/2009] [Accepted: 12/16/2009] [Indexed: 01/12/2023]
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Shklover J, Weisman-Shomer P, Yafe A, Fry M. Quadruplex structures of muscle gene promoter sequences enhance in vivo MyoD-dependent gene expression. Nucleic Acids Res 2010; 38:2369-77. [PMID: 20053730 PMCID: PMC2853122 DOI: 10.1093/nar/gkp1208] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Gene promoters are enriched in guanine clusters that potentially fold into quadruplex structures. Such quadruplexes were implicated in the regulation of gene expression, plausibly by interacting with transcription factors. We showed previously that homodimers of the myogenic transcription factor MyoD bound in vitro most tightly bimolecular quadruplexes of promoter sequences of muscle-specific genes. By contrast, MyoD-E47 heterodimers formed tighter complexes with d(CANNTG) E-box motifs that govern muscle gene expression. Here, we show that DNA quadruplexes enhance in vivo MyoD and E-box-driven expression of a firefly luciferase (FL) reporter gene. HEK293 cells were transfected with FL expressing p4RTK-FL vector alone or together with MyoD expressing pEMSV-MyoD plasmid, with quadruplexes of α7 integrin or sarcomeric mitochondrial creatine kinase (sMtCK) muscle gene promoters or with a combination thereof. Whereas MyoD elevated by ∼10-fold the levels of FL mRNA and protein, the DNA quadruplexes by themselves did not affect FL expression. However, together with MyoD, quadruplex DNA increased by ∼35-fold the amounts of FL mRNA and protein. Without affecting its expression, DNA quadruplexes bound MyoD in the cells. Based on these results, we propose models for the regulation of muscle gene transcription by direct interaction of MyoD with promoter quadruplex structures.
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Affiliation(s)
| | | | | | - Michael Fry
- *To whom correspondence should be addressed. Tel: +972 4 829 5328; Fax: +972 4 851 0735;
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24
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Wilson T, Williamson MP, Thomas JA. Differentiating quadruplexes: binding preferences of a luminescent dinuclear ruthenium(ii) complex with four-stranded DNA structures. Org Biomol Chem 2010; 8:2617-21. [DOI: 10.1039/b924263e] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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25
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Du Z, Zhao Y, Li N. Genome-wide colonization of gene regulatory elements by G4 DNA motifs. Nucleic Acids Res 2009; 37:6784-98. [PMID: 19759215 PMCID: PMC2777415 DOI: 10.1093/nar/gkp710] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
G-quadruplex (or G4 DNA), a stable four-stranded structure found in guanine-rich regions, is implicated in the transcriptional regulation of genes involved in growth and development. Previous studies on the role of G4 DNA in gene regulation mostly focused on genomic regions proximal to transcription start sites (TSSs). To gain a more comprehensive understanding of the regulatory role of G4 DNA, we examined the landscape of potential G4 DNA (PG4Ms) motifs in the human genome and found that G4 motifs, not restricted to those found in the TSS-proximal regions, are bias toward gene-associated regions. Significantly, analyses of G4 motifs in seven types of well-known gene regulatory elements revealed a constitutive enrichment pattern and the clusters of G4 motifs tend to be colocalized with regulatory elements. Considering our analysis from a genome evolutionary perspective, we found evidence that the occurrence and accumulation of certain progenitors and canonical G4 DNA motifs within regulatory regions were progressively favored by natural selection. Our results suggest that G4 DNA motifs are ‘colonized’ in regulatory regions, supporting a likely genome-wide role of G4 DNA in gene regulation. We hypothesize that G4 DNA is a regulatory apparatus situated in regulatory elements, acting as a molecular switch that can modulate the role of the host functional regions, by transition in DNA structure.
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Affiliation(s)
- Zhuo Du
- State Key Laboratory of Agrobiotechnology, College of Biological Science, China Agricultural University, Beijing 100193, PR China
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26
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Nakken S, Rognes T, Hovig E. The disruptive positions in human G-quadruplex motifs are less polymorphic and more conserved than their neutral counterparts. Nucleic Acids Res 2009; 37:5749-56. [PMID: 19617376 PMCID: PMC2761265 DOI: 10.1093/nar/gkp590] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Specific guanine-rich sequence motifs in the human genome have considerable potential to form four-stranded structures known as G-quadruplexes or G4 DNA. The enrichment of these motifs in key chromosomal regions has suggested a functional role for the G-quadruplex structure in genomic regulation. In this work, we have examined the spectrum of nucleotide substitutions in G4 motifs, and related this spectrum to G4 prevalence. Data collected from the large repository of human SNPs indicates that the core feature of G-quadruplex motifs, 5′-GGG-3′, exhibits specific mutational patterns that preserve the potential for G4 formation. In particular, we find a genome-wide pattern in which sites that disrupt the guanine triplets are more conserved and less polymorphic than their neutral counterparts. This also holds when considering non-CpG sites only. However, the low level of polymorphisms in guanine tracts is not only confined to G4 motifs. A complete mapping of DNA three-mers at guanine polymorphisms indicated that short guanine tracts are the most under-represented sequence context at polymorphic sites. Furthermore, we provide evidence for a strand bias upstream of human genes. Here, a significantly lower rate of G4-disruptive SNPs on the non-template strand supports a higher relative influence of G4 formation on this strand during transcription.
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Affiliation(s)
- Sigve Nakken
- Centre for Molecular Biology and Neuroscience, Institute of Medical Microbiology, Oslo University Hospital, Rikshospitalet, NO-0027, Oslo, Norway.
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27
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Wang G, Zhao J, Vasquez KM. Methods to determine DNA structural alterations and genetic instability. Methods 2009; 48:54-62. [PMID: 19245837 PMCID: PMC2693251 DOI: 10.1016/j.ymeth.2009.02.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2008] [Accepted: 02/15/2009] [Indexed: 11/16/2022] Open
Abstract
Chromosomal DNA is a dynamic structure that can adopt a variety of non-canonical (i.e., non-B) conformations. In this regard, at least 10 different forms of non-B DNA conformations have been identified; many of them have been found to be mutagenic, and associated with human disease development. Despite the importance of non-B DNA structures in genetic instability and DNA metabolic processes, mechanisms by which instability occurs remain largely undefined. The purpose of this review is to summarize current methodologies that are used to address questions in the field of non-B DNA structure-induced genetic instability. Advantages and disadvantages of each method will be discussed. A focused effort to further elucidate the mechanisms of non-B DNA-induced genetic instability will lead to a better understanding of how these structure-forming sequences contribute to the development of human disease.
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Affiliation(s)
- Guliang Wang
- Department of Carcinogenesis, University of Texas M.D. Anderson Cancer Center, Science Park-Research Division, 1808 Park Road 1-C, Smithville, TX 78957
| | - Junhua Zhao
- Department of Carcinogenesis, University of Texas M.D. Anderson Cancer Center, Science Park-Research Division, 1808 Park Road 1-C, Smithville, TX 78957
| | - Karen M. Vasquez
- Department of Carcinogenesis, University of Texas M.D. Anderson Cancer Center, Science Park-Research Division, 1808 Park Road 1-C, Smithville, TX 78957
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28
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Zhang JL, Fu Y, Zheng L, Li W, Li H, Sun Q, Xiao Y, Geng F. Natural isoflavones regulate the quadruplex-duplex competition in human telomeric DNA. Nucleic Acids Res 2009; 37:2471-82. [PMID: 19261597 PMCID: PMC2677859 DOI: 10.1093/nar/gkp055] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Effects of natural isoflavones on the structural competition of human telomeric G-quadruplex d[AG(3)(T(2)AG(3))(3)] and its related Watson-Crick duplex d[AG(3)(T(2)AG(3))(3)-(C(3)TA(2))(3)C(3)T] are investigated by using circular dichroism (CD), ESI-MS, fluorescence quenching measurement, CD stopped-flow kinetic experiment, UV spectroscopy and molecular modeling methods. It is intriguing to find out that isoflavones can stabilize the G-quadruplex structure but destabilize its corresponding Watson-Crick duplex and this discriminated interaction is intensified by molecular crowding environments. Kinetic experiments indicate that the dissociation rate of quadruplex (k(obs290 nm)) is decreased by 40.3% at the daidzin/DNA molar ratio of 1.0 in K(+), whereas in Na(+) the observed rate constant is reduced by about 12.0%. Furthermore, glycosidic daidzin significantly induces a structural transition of the polymorphic G-quadruplex into the antiparallel conformation in K(+). This is the first report on the recognition of isoflavones with conformational polymorphism of G-quadruplex, which suggests that natural isoflavone constituents potentially exhibit distinct regulation on the structural competition of quadruplex versus duplex in human telomeric DNA.
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Affiliation(s)
- Jin-li Zhang
- Key Laboratory of Systems Bioengineering, Ministry of Education, School of Chemical Engineering & Technology, Tianjin University, Tianjin 300072, China
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29
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Thakur RK, Kumar P, Halder K, Verma A, Kar A, Parent JL, Basundra R, Kumar A, Chowdhury S. Metastases suppressor NM23-H2 interaction with G-quadruplex DNA within c-MYC promoter nuclease hypersensitive element induces c-MYC expression. Nucleic Acids Res 2008; 37:172-83. [PMID: 19033359 PMCID: PMC2615625 DOI: 10.1093/nar/gkn919] [Citation(s) in RCA: 143] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Regulatory influence of the G-quadruplex or G4 motif present within the nuclease hypersensitive element (NHE) in the promoter of c-MYC has been noted. On the other hand, association of NM23-H2 to the NHE leads to c-MYC activation. Therefore, NM23-H2 interaction with the G4 motif within the c-MYC NHE presents an interesting mechanistic possibility. Herein, using luciferase reporter assay and chromatin immunoprecipitation we show NM23-H2 mediated c-MYC activation involves NM23-H2-G4 motif binding within the c-MYC NHE. G4 motif complex formation with recombinant NM23-H2 was independently confirmed using fluorescence energy transfer, which also indicated that the G4 motif was resolved to an unfolded state within the protein-bound complex. Taken together, this supports transcriptional role of NM23-H2 via a G4 motif.
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Affiliation(s)
- Ram Krishna Thakur
- Proteomics and Structural Biology Unit, Institute of Genomics and Integrative Biology, CSIR, Delhi, India
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30
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Yafe A, Shklover J, Weisman-Shomer P, Bengal E, Fry M. Differential binding of quadruplex structures of muscle-specific genes regulatory sequences by MyoD, MRF4 and myogenin. Nucleic Acids Res 2008; 36:3916-25. [PMID: 18511462 PMCID: PMC2475631 DOI: 10.1093/nar/gkn340] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Four myogenic regulatory factors (MRFs); MyoD, Myf-5, MRF4 and Myogenin direct muscle tissue differentiation. Heterodimers of MRFs with E-proteins activate muscle-specific gene expression by binding to E-box motifs d(CANNTG) in their promoters or enhancers. We showed previously that in contrast to the favored binding of E-box by MyoD-E47 heterodimers, homodimeric MyoD associated preferentially with quadruplex structures of regulatory sequences of muscle-specific genes. To inquire whether other MRFs shared the DNA binding preferences of MyoD, the DNA affinities of hetero- and homo-dimeric MyoD, MRF4 and Myogenin were compared. Similarly to MyoD, heterodimers with E47 of MRF4 or Myogenin bound E-box more tightly than quadruplex DNA. However, unlike homodimeric MyoD or MRF4, Myogenin homodimers associated weakly and nonpreferentially with quadruplex DNA. By reciprocally switching basic regions between MyoD and Myogenin we demonstrated dominance of MyoD in determining the quadruplex DNA-binding affinity. Thus, Myogenin with an implanted MyoD basic region bound quadruplex DNA nearly as tightly as MyoD. However, a grafted Myogenin basic region did not diminish the high affinity of homodimeric MyoD for quadruplex DNA. We speculate that the dissimilar interaction of MyoD and Myogenin with tetrahelical domains in muscle gene promoters may differently regulate their myogenic activities.
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Affiliation(s)
- Anat Yafe
- Department of Biochemistry, Rappaport Faculty of Medicine, Technion - Israel Institute of Technology, POB 9649 Bat Galim, Haifa 31096, Israel
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31
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Cogoi S, Paramasivam M, Spolaore B, Xodo LE. Structural polymorphism within a regulatory element of the human KRAS promoter: formation of G4-DNA recognized by nuclear proteins. Nucleic Acids Res 2008; 36:3765-80. [PMID: 18490377 PMCID: PMC2441797 DOI: 10.1093/nar/gkn120] [Citation(s) in RCA: 118] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The human KRAS proto-oncogene contains a critical nuclease hypersensitive element (NHE) upstream of the major transcription initiation site. In this article, we demonstrate by primer-extension experiments, PAGE, chemical footprinting, CD, UV and FRET experiments that the G-rich strand of NHE (32R) folds into intra-molecular G-quadruplex structures. Fluorescence data show that 32R in 100 mM KCl melts with a biphasic profile, showing the formation of two distinct G-quadruplexes with Tm of ∼55°C (Q1) and ∼72°C (Q2). DMS-footprinting and CD suggest that Q1 can be a parallel and Q2 a mixed parallel/antiparallel G-quadruplex. When dsNHE (32R hybridized to its complementary) is incubated with a nuclear extract from Panc-1 cells, three DNA–protein complexes are observed by EMSA. The complex of slower mobility is competed by quadruplex 32R, but not by mutant oligonucleotides, which cannot form a quadruplex structure. Using paramagnetic beads coupled with 32R, we pulled down from the Panc-1 extract proteins with affinity for quadruplex 32R. One of these is the heterogeneous nuclear ribonucleoprotein A1, which was previously reported to unfold quadruplex DNA. Our study suggests a role of quadruplex DNA in KRAS transcription and provides the basis for the rationale design of molecular strategies to inhibit the expression of KRAS.
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Affiliation(s)
- Susanna Cogoi
- Department of Biomedical Science and Technology, School of Medicine, Ple. Kolbe 4, 33100 Udine and CRIBI Biotechnology Centre, University of Padova, Viale G. Colombo 3, 35121 Padova, Italy
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32
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Tsumagari K, Qi L, Jackson K, Shao C, Lacey M, Sowden J, Tawil R, Vedanarayanan V, Ehrlich M. Epigenetics of a tandem DNA repeat: chromatin DNaseI sensitivity and opposite methylation changes in cancers. Nucleic Acids Res 2008; 36:2196-207. [PMID: 18281700 PMCID: PMC2367708 DOI: 10.1093/nar/gkn055] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
DNA methylation and chromatin DNaseI sensitivity were analyzed in and adjacent to D4Z4 repeat arrays, which consist of 1 to ∼100 tandem 3.3-kb units at subtelomeric 4q and 10q. D4Z4 displayed hypomethylation in some cancers and hypermethylation in others relative to normal tissues. Surprisingly, in cancers with extensive D4Z4 methylation there was a barrier to hypermethylation spreading to the beginning of this disease-associated array (facioscapulohumeral muscular dystrophy, FSHD) despite sequence conservation in repeat units throughout the array. We infer a different chromatin structure at the proximal end of the array than at interior repeats, consistent with results from chromatin DNaseI sensitivity assays indicating a boundary element near the beginning of the array. The relative chromatin DNaseI sensitivity in FSHD and control myoblasts and lymphoblasts was as follows: a non-genic D4Z4-adjacent sequence (p13E-11, array-proximal)> untranscribed gene standards > D4Z4 arrays> constitutive heterochromatin (satellite 2; P< 10−4 for all comparisons). Cancers displaying D4Z4 hypermethylation also exhibited a hypermethylation-resistant subregion within the 3.3-kb D4Z4 repeat units. This subregion contains runs of G that form G-quadruplexes in vitro. Unusual DNA structures might contribute to topological constraints that link short 4q D4Z4 arrays to FSHD and make long ones phenotypically neutral.
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Affiliation(s)
- Koji Tsumagari
- Human Genetics Program and Department of Biochemistry and Tulane Cancer Center, Tulane Medical School, Department of Mathematics, Tulane University, New Orleans, LA 70112, USA
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Bugaut A, Balasubramanian S. A sequence-independent study of the influence of short loop lengths on the stability and topology of intramolecular DNA G-quadruplexes. Biochemistry 2007; 47:689-97. [PMID: 18092816 DOI: 10.1021/bi701873c] [Citation(s) in RCA: 256] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
G-Rich sequences found within biologically important regions of the genome have been shown to form intramolecular G-quadruplexes with varied loop lengths and sequences. Many of these quadruplexes will be distinguishable from each other on the basis of their thermodynamic stabilities and folded conformations. It has been proposed that loop lengths can strongly influence the topology and stability of intramolecular G-quadruplexes. Previous studies have been limited to the analysis of quadruplex sequences with particular loop sequences, making it difficult to make generalizations. Here, we describe an original study that aimed to elucidate the effect of loop length on the biophysical properties of G-quadruplexes in a sequence-independent context. We employed UV melting and circular dichroism spectroscopy to examine and compare the properties of 21 DNA quadruplex libraries, each comprising partially randomized loop sequences with lengths ranging from one to three nucleotides. Our work supports a number of general predictions that can be made solely on the basis of loop lengths. In particular, the results emphasize the strong influence of single-nucleotide loops on quadruplex properties. This study provides a predictive framework that may help identify or classify biologically relevant G-quadruplex-forming sequences.
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Affiliation(s)
- Anthony Bugaut
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
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34
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Abstract
G-quadruplex or G4 DNA, a four-stranded DNA structure formed in G-rich sequences, has been hypothesized to be a structural motif involved in gene regulation. In this study, we examined the regulatory role of potential G4 DNA motifs (PG4Ms) located in the putative transcriptional regulatory region (TRR, -500 to +500) of genes across the human genome. We found that PG4Ms in the 500-bp region downstream of the annotated transcription start site (TSS; PG4M(D500)) are associated with gene expression. Generally, PG4M(D500)-positive genes are expressed at higher levels than PG4M(D500)-negative genes, and an increased number of PG4M(D500) provides a cumulative effect. This observation was validated by controlling for attributes, including gene family, function, and promoter similarity. We also observed an asymmetric pattern of PG4M(D500) distribution between strands, whereby the frequency of PG4M(D500) in the coding strand is generally higher than that in the template strand. Further analysis showed that the presence of PG4M(D500) and its strand asymmetry are associated with significant enrichment of RNAP II at the putative TRR. On the basis of these results, we propose a model of G4 DNA-mediated stimulation of transcription with the hypothesis that PG4M(D500) contributes to gene transcription by maintaining the DNA in an open conformation, while the asymmetric distribution of PG4M(D500) considerably reduces the probability of blocking the progression of the RNA polymerase complex on the template strand. Our findings provide a comprehensive view of the regulatory function of G4 DNA in gene transcription.
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Abstract
Over the past decade, nucleic acid chemists have seen the spectacular emergence of molecules designed to interact efficiently and selectively with a peculiar DNA structure named G-quadruplex. Initially derived from classical DNA intercalators, these G-quadruplex ligands progressively became the focal point of new excitement since they appear to inhibit selectively the growth of cancer cells thereby opening interesting perspectives towards the development of novel anti-cancer drugs. The present article aims to help researchers enter this exciting research field, and to highlight recent advances in the design of G-quadruplex ligands.
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Affiliation(s)
- David Monchaud
- Institut Curie, CNRS UMR176, Section Recherche, Centre Universitaire Paris XI, Bât. 110, 91405, Orsay, France
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36
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Hazel P, Parkinson GN, Neidle S. Topology variation and loop structural homology in crystal and simulated structures of a bimolecular DNA quadruplex. J Am Chem Soc 2007; 128:5480-7. [PMID: 16620121 DOI: 10.1021/ja058577+] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The topology of DNA quadruplexes depends on the nature and number of the nucleotides linking G-quartet motifs. To assess the effects of a three-nucleotide TTT linker, the crystal structure of the DNA sequence d(G(4)T(3)G(4)) has been determined at 1.5 A resolution, together with that of the brominated analogue d(G(4)(Br)UTTG(4)) at 2.4 A resolution. Both sequences form bimolecular intermolecular G-quadruplexes with lateral loops. d(G(4)(Br)UTTG(4)) crystallized in the monoclinic space group P2(1) with three quadruplex molecules in the asymmetric unit, two associating together as a head-to-head stacked dimer, and the third as a single head-to-tail dimer. The head-to-head dimers have two lateral loops on the same G-quadruplex face and form an eight-G-quartet stack, with a linear array of seven K(+) ions between the quartets. d(G(4)T(3)G(4)) crystallized in the orthorhombic space group C222 and has a structure very similar to the head-to-tail dimer in the P2(1) unit cell. The sequence studied here is able to form several different folds; however, all four quadruplexes in the two structures have lateral loops, in contrast to the diagonal loops reported for the analogous quadruplex with T(4) loops. A total of seven independent T(3) loops were observed in the two structures. These can be classified into two discrete conformational classes, suggesting that these represent preferred loop conformations that are independent of crystal-packing forces.
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Affiliation(s)
- Pascale Hazel
- Cancer Research U.K. Biomolecular Structure Group, The School of Pharmacy, University of London, 29-39 Brunswick Square, London WC1N 1AX, UK
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Shklover J, Etzioni S, Weisman-Shomer P, Yafe A, Bengal E, Fry M. MyoD uses overlapping but distinct elements to bind E-box and tetraplex structures of regulatory sequences of muscle-specific genes. Nucleic Acids Res 2007; 35:7087-95. [PMID: 17942416 PMCID: PMC2175354 DOI: 10.1093/nar/gkm746] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Muscle differentiation and expression of muscle-specific proteins are initiated by the binding of heterodimers of the transcription factor MyoD with E2A proteins to E-box motif d(CANNTG) in promoters or enhancers of muscle-specific genes. MyoD homodimers, however, form tighter complexes with tetraplex structures of guanine-rich regulatory sequences of some muscle genes. In this work, we identified elements in MyoD that bind E-box or tetraplex structures of promoter sequences of the muscle-specific genes α7 integrin and sarcomeric Mitochondrial Creatine Kinase (sMtCK). Deletions of large domains of the 315 amino acids long recombinant MyoD indicated that the binding site for both E-box and tetraplex DNA is its basic region KRKTTNADRRKAATMRERRR that encompasses the three underlined clusters of basic residues designated R1, R2 and R3. Deletion of a single or pairs of R triads or R111C substitution completely abolished the E-box-binding capacity of MyoD. By contrast, the MyoD deletion mutants Δ102–114, ΔR3, ΔR1R3 or ΔR2R3 maintained comparable tetraplex DNA-binding capacity as reflected by the similar dissociation constants of their protein–DNA complexes. Only deletion of all three basic clusters abolished the binding of tetraplex DNA. Implications of the binding of E-box and tetraplex DNA by non-identical MyoD elements are considered.
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Affiliation(s)
- Jeny Shklover
- Department of Biochemistry, Rappaport Faculty of Medicine, Technion - Israel Institute of Technology, POB 9649 Bat Galim, Haifa 31096, Israel
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Rachwal PA, Findlow IS, Werner JM, Brown T, Fox KR. Intramolecular DNA quadruplexes with different arrangements of short and long loops. Nucleic Acids Res 2007; 35:4214-22. [PMID: 17576685 PMCID: PMC1919480 DOI: 10.1093/nar/gkm316] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
We have examined the folding, stability and kinetics of intramolecular quadruplexes formed by DNA sequences containing four G3 tracts separated by either single T or T4 loops. All these sequences fold to form intramolecular quadruplexes and 1D-NMR spectra suggest that they each adopt unique structures (with the exception of the sequence with all three loops containing T4, which is polymorphic). The stability increases with the number of single T loops, though the arrangement of different length loops has little effect. In the presence of potassium ions, the oligonucleotides that contain at least one single T loop exhibit similar CD spectra, which are indicative of a parallel topology. In contrast, when all three loops are substituted with T4 the CD spectrum is typical of an antiparallel arrangement. In the presence of sodium ions, the sequences with two and three single T loops also adopt a parallel folded structure. Kinetic studies on the complexes with one or two T4 loops in the presence of potassium ions reveal that sequences with longer loops display slower folding rates.
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Affiliation(s)
- Phillip A. Rachwal
- School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton SO16 7PX, UK and School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK
| | - I. Stuart Findlow
- School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton SO16 7PX, UK and School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK
| | - Joern M. Werner
- School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton SO16 7PX, UK and School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK
| | - Tom Brown
- School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton SO16 7PX, UK and School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK
| | - Keith R. Fox
- School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton SO16 7PX, UK and School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK
- *To whom correspondence should be addressed. +44 23 8059 4374+44 23 8059 4459
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Wang L, Bai J, Luo J, Chen H, Ye X, Jian Q, Lao H. Molecular cloning and expression of grass carp MyoD in yeast Pichia pastoris. BMB Rep 2007; 40:22-8. [PMID: 17244478 DOI: 10.5483/bmbrep.2007.40.1.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
MyoD, expressed in skeletal muscle lineages of vertebrate embryo, is one of muscle-specific basic helix-loop-helix (bHLH) transcription factors, which plays a key role in the determination and differentiation of all skeletal muscle lineages. In this study, a cDNA of grass carp MyoD was cloned and characterized from total RNA of grass carp embryos by RT-PCR. The full-length cDNA of grass carp MyoD is 1597 bp. The cDNA sequence analysis reveals an open reading frame of 825 bp coding for a protein of 275 amino acids, which includes a bHLH domain composed of basic domain (1-84(th) amino acids) and HLH domain (98-142(th) amino acids), without signal peptide. Then the MyoD cDNA of grass carp was cloned to yeast expression vector pPICZalphaA and transformed into P. pastoris GS115 strain, the recombinant MyoD protein with a molecular weight of about 31KD was obtained after inducing for 2d with 0.5% methanol in pH 8.0 BMGY medium, and the maximum yield was about 250 mg/L in shaking-flask fermentation. The results were expected to benefit for further studies on the crystal structure and physiological function of fish MyoD.
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Affiliation(s)
- Lixin Wang
- Pearl River Fisheries Research Institute, CAFS. Key Lab. of Tropical & Subtropical Fish Breeding & Cultivation of CAFS, Guangzhou 510380, P. R. China
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Dai J, Chen D, Jones RA, Hurley LH, Yang D. NMR solution structure of the major G-quadruplex structure formed in the human BCL2 promoter region. Nucleic Acids Res 2006; 34:5133-44. [PMID: 16998187 PMCID: PMC1636422 DOI: 10.1093/nar/gkl610] [Citation(s) in RCA: 287] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2006] [Revised: 08/03/2006] [Accepted: 08/03/2006] [Indexed: 01/22/2023] Open
Abstract
BCL2 protein functions as an inhibitor of cell apoptosis and has been found to be aberrantly expressed in a wide range of human diseases. A highly GC-rich region upstream of the P1 promoter plays an important role in the transcriptional regulation of BCL2. Here we report the NMR solution structure of the major intramolecular G-quadruplex formed on the G-rich strand of this region in K+ solution. This well-defined mixed parallel/antiparallel-stranded G-quadruplex structure contains three G-tetrads of mixed G-arrangements, which are connected with two lateral loops and one side loop, and four grooves of different widths. The three loops interact with the core G-tetrads in a specific way that defines and stabilizes the overall G-quadruplex structure. The loop conformations are in accord with the experimental mutation and footprinting data. The first 3-nt loop adopts a lateral loop conformation and appears to determine the overall folding of the BCL2 G-quadruplex. The third 1-nt double-chain-reversal loop defines another example of a stable parallel-stranded structural motif using the G3NG3 sequence. Significantly, the distinct major BCL2 promoter G-quadruplex structure suggests that it can be specifically involved in gene modulation and can be an attractive target for pathway-specific drug design.
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Affiliation(s)
- Jixun Dai
- College of Pharmacy, The University of Arizona1703 E. Mabel Street, Tucson, AZ 85721, USA
| | - Ding Chen
- College of Pharmacy, The University of Arizona1703 E. Mabel Street, Tucson, AZ 85721, USA
| | - Roger A. Jones
- Department of Chemistry and Chemical Biology, Rutgers University610 Taylor Road, Piscataway, NJ 08854, USA
| | - Laurence H. Hurley
- College of Pharmacy, The University of Arizona1703 E. Mabel Street, Tucson, AZ 85721, USA
- Arizona Cancer Center1515 N. Campbell Avenue, Tucson, AZ 85724, USA
- BIO5 Institute, The University of Arizona1140 E. South Campus Dr, Tucson, AZ 85721, USA
| | - Danzhou Yang
- College of Pharmacy, The University of Arizona1703 E. Mabel Street, Tucson, AZ 85721, USA
- Arizona Cancer Center1515 N. Campbell Avenue, Tucson, AZ 85724, USA
- BIO5 Institute, The University of Arizona1140 E. South Campus Dr, Tucson, AZ 85721, USA
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Sharov AA, Dudekula DB, Ko MSH. CisView: a browser and database of cis-regulatory modules predicted in the mouse genome. DNA Res 2006; 13:123-34. [PMID: 16980320 DOI: 10.1093/dnares/dsl005] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
To facilitate the analysis of gene regulatory regions of the mouse genome, we developed a CisView (http://lgsun.grc.nia.nih.gov/cisview), a browser and database of genome-wide potential transcription factor binding sites (TFBSs) that were identified using 134 position-weight matrices and 219 sequence patterns from various sources and were presented with the information about sequence conservation, neighboring genes and their structures, GO annotations, protein domains, DNA repeats and CpG islands. Analysis of the distribution of TFBSs revealed that many TFBSs (N = 145) were over-represented near transcription start sites. We also identified potential cis-regulatory modules (CRMs) defined as clusters of conserved TFBSs in the entire mouse genome. Out of 739 074 CRMs, 157 442 had a significantly higher regulatory potential score than semi-random sequences generated with a 3rd-order Markov process. The CisView browser provides a user-friendly computer environment for studying transcription regulation on a whole-genome scale and can also be used for interpreting microarray experiments and identifying putative targets of transcription factors.
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Affiliation(s)
- Alexei A Sharov
- Developmental Genomics and Aging Section, Laboratory of Genetics, National Institute on Aging, National Institutes of Health 333 Cassell Drive, Suite 3000, Baltimore, MD 21224, USA
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Ambrus A, Chen D, Dai J, Bialis T, Jones RA, Yang D. Human telomeric sequence forms a hybrid-type intramolecular G-quadruplex structure with mixed parallel/antiparallel strands in potassium solution. Nucleic Acids Res 2006; 34:2723-35. [PMID: 16714449 PMCID: PMC1464114 DOI: 10.1093/nar/gkl348] [Citation(s) in RCA: 901] [Impact Index Per Article: 50.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2006] [Revised: 04/04/2006] [Accepted: 04/19/2006] [Indexed: 11/23/2022] Open
Abstract
Human telomeric DNA consists of tandem repeats of the sequence d(TTAGGG). The formation and stabilization of DNA G-quadruplexes in the human telomeric sequence have been shown to inhibit the activity of telomerase, thus the telomeric DNA G-quadruplex has been considered as an attractive target for cancer therapeutic intervention. However, knowledge of the intact human telomeric G-quadruplex structure(s) formed under physiological conditions is a prerequisite for structure-based rational drug design. Here we report the folding structure of the human telomeric sequence in K+ solution determined by NMR. Our results demonstrate a novel, unprecedented intramolecular G-quadruplex folding topology with hybrid-type mixed parallel/antiparallel G-strands. This telomeric G-quadruplex structure contains three G-tetrads with mixed G-arrangements, which are connected consecutively with a double-chain-reversal side loop and two lateral loops, each consisting of three nucleotides TTA. This intramolecular hybrid-type telomeric G-quadruplex structure formed in K+ solution is distinct from those reported on the 22 nt Tel22 in Na+ solution and in crystalline state in the presence of K+, and appears to be the predominant conformation for the extended 26 nt telomeric sequence Tel26 in the presence of K+, regardless of the presence or absence of Na+. Furthermore, the addition of K+ readily converts the Na+-form conformation to the K+-form hybrid-type G-quadruplex. Our results explain all the reported experimental data on the human telomeric G-quadruplexes formed in the presence of K+, and provide important insights for understanding the polymorphism and interconversion of various G-quadruplex structures formed within the human telomeric sequence, as well as the effects of sequence and cations. This hybrid-type G-quadruplex topology suggests a straightforward pathway for the secondary structure formation with effective packing within the extended human telomeric DNA. The hybrid-type telomeric G-quadruplex is most likely to be of pharmacological relevance, and the distinct folding topology of this G-quadruplex suggests that it can be specifically targeted by G-quadruplex interactive small molecule drugs.
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Affiliation(s)
- Attila Ambrus
- College of Pharmacy, The University of Arizona1703 E. Mabel St, Tucson, AZ 85721, USA
| | - Ding Chen
- College of Pharmacy, The University of Arizona1703 E. Mabel St, Tucson, AZ 85721, USA
| | - Jixun Dai
- College of Pharmacy, The University of Arizona1703 E. Mabel St, Tucson, AZ 85721, USA
| | - Tiffanie Bialis
- Arizona Cancer Center1515 N. Campbell Avenue, Tucson, AZ 85724, USA
| | - Roger A. Jones
- Department of Chemistry and Chemical Biology, Rutgers University610 Taylor Road, Piscataway, NJ 08854, USA
| | - Danzhou Yang
- College of Pharmacy, The University of Arizona1703 E. Mabel St, Tucson, AZ 85721, USA
- Arizona Cancer Center1515 N. Campbell Avenue, Tucson, AZ 85724, USA
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Dexheimer TS, Sun D, Hurley LH. Deconvoluting the structural and drug-recognition complexity of the G-quadruplex-forming region upstream of the bcl-2 P1 promoter. J Am Chem Soc 2006; 128:5404-15. [PMID: 16620112 PMCID: PMC2580050 DOI: 10.1021/ja0563861] [Citation(s) in RCA: 303] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The human bcl-2 gene contains a GC-rich region upstream of the P1 promoter that has been shown to be critically involved in the regulation of bcl-2 gene expression. We have demonstrated that the guanine-rich strand of the DNA in this region can form any one of three distinct intramolecular G-quadruplex structures. Mutation and deletion analysis permitted isolation and identification of three overlapping DNA sequences within this element that formed the three individual G-quadruplexes. Each of these was characterized using nondenaturing gel analysis, DMS footprinting, and circular dichroism. The central G-quadruplex, which is the most stable, forms a mixed parallel/antiparallel structure consisting of three tetrads connected by loops of one, seven, and three bases. Three different G-quadruplex-interactive agents were found to further stabilize these structures, with individual selectivity toward one or more of these G-quadruplexes. Collectively, these results suggest that the multiple G-quadruplexes identified in the promoter region of the bcl-2 gene are likely to play a similar role to the G-quadruplexes in the c-myc promoter in that their formation could serve to modulate gene transcription. Last, we demonstrate that the complexity of the G-quadruplexes in the bcl-2 promoter extends beyond the ability to form any one of three separate G-quadruplexes to each having the capacity to form either three or six different loop isomers. These results are discussed in relation to the biological significance of this G-quadruplex-forming element in modulation of bcl-2 gene expression and the inherent complexity of the system where different G-quadruplexes and loop isomers are possible.
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Affiliation(s)
| | - Daekyu Sun
- College of Pharmacy, University of Arizona, Tucson, Arizona 85721
| | - Laurence H. Hurley
- College of Pharmacy, University of Arizona, Tucson, Arizona 85721
- Arizona Cancer Center, 1515 N. Campbell Ave., Tucson, Arizona 85724
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721
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Sun D, Guo K, Rusche JJ, Hurley LH. Facilitation of a structural transition in the polypurine/polypyrimidine tract within the proximal promoter region of the human VEGF gene by the presence of potassium and G-quadruplex-interactive agents. Nucleic Acids Res 2005; 33:6070-80. [PMID: 16239639 PMCID: PMC1266068 DOI: 10.1093/nar/gki917] [Citation(s) in RCA: 328] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The proximal promoter region of the human vascular endothelial growth factor (VEGF) gene contains a polypurine/polypyrimidine tract that serves as a multiple binding site for Sp1 and Egr-1 transcription factors. This tract contains a guanine-rich sequence consisting of four runs of three or more contiguous guanines separated by one or more bases, corresponding to a general motif for the formation of an intramolecular G-quadruplex. In this study, we observed the progressive unwinding of the oligomer duplex DNA containing this region into single-stranded forms in the presence of KCl and the G-quadruplex-interactive agents TMPyP4 and telomestatin, suggesting the dynamic nature of this tract under conditions which favor the formation of the G-quadruplex structures. Subsequent footprinting studies with DNase I and S1 nucleases using a supercoiled plasmid DNA containing the human VEGF promoter region also revealed a long protected region, including the guanine-rich sequences, in the presence of KCl and telomestatin. Significantly, a striking hypersensitivity to both nucleases was observed at the 3′-side residue of the predicted G-quadruplex-forming region in the presence of KCl and telomestatin, indicating altered conformation of the human VEGF proximal promoter region surrounding the guanine-rich sequence. In contrast, when specific point mutations were introduced into specific guanine residues within the G-quadruplex-forming region (Sp1 binding sites) to abolish G-quadruplex-forming ability, the reactivity of both nucleases toward the mutated human VEGF proximal promoter region was almost identical, even in the presence of telomestatin with KCl. This comparison of wild-type and mutant sequences strongly suggests that the formation of highly organized secondary structures such as G-quadruplexes within the G-rich region of the human VEGF promoter region is responsible for observed changes in the reactivity of both nucleases within the polypurine/polypyrimidine tract of the human VEGF gene. The formation of the G-quadruplex structures from this G-rich sequence in the human VEGF promoter is further confirmed by the CD experiments. Collectively, our results provide strong evidence that specific G-quadruplex structures can naturally be formed by the G-rich sequence within the polypurine/polypyrimidine tract of the human VEGF promoter region, raising the possibility that the transcriptional control of the VEGF gene can be modulated by G-quadruplex-interactive agents.
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Affiliation(s)
- Daekyu Sun
- College of Pharmacy, University of Arizona, Tucson, AZ 85721, USA.
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Etzioni S, Yafe A, Khateb S, Weisman-Shomer P, Bengal E, Fry M. Homodimeric MyoD preferentially binds tetraplex structures of regulatory sequences of muscle-specific genes. J Biol Chem 2005; 280:26805-12. [PMID: 15923190 DOI: 10.1074/jbc.m500820200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Myogenic transcription is activated by the binding of heterodimers of the basic helix-loop-helix proteins MyoD and E12 or E47 to a consensus E-box sequence, d(CANNTG), in promoter or enhancer regions of muscle-specific genes. Homodimers of MyoD bind E-box less tightly and are less efficient activators of transcription. Recent results from our laboratory (Yafe, A., Etzioni, S., Weisman-Shomer, P., and Fry, M. (2005) Nucleic Acids Res. 33, 2887-2900) indicate that regulatory sequences of several muscle-specific genes contain a disproportionate high content of guanine clusters that readily form hairpin and parallel-stranded unimolecular and bimolecular tetraplex structures. Here we have shown that homodimers of full-length recombinant MyoD formed complexes with bimolecular tetraplex structures of muscle-specific regulatory sequences but not with their double-stranded, hairpin, or unimolecular tetraplex forms. Preferential binding of homodimeric MyoD to bimolecular tetraplex DNA structures over E-box DNA was reflected by the 18.7-39.9-fold lower dissociation constants, Kd, of the MyoD-tetraplex DNA complexes. Conversely, MyoD-E47 heterodimers formed tighter complexes with E-box as indicated by their 6.8-19.0-fold lower Kd relative to complexes with bimolecular tetraplex DNA structures. Similarly, homodimers of the 60-amino acid basic helix-loop-helix domain of MyoD bound E-box more efficiently and tetraplex DNA less efficiently than homodimers of full-length MyoD. It might be that the favored binding of MyoD homodimers to tetraplex DNA structures lowers their ability to activate muscle-specific gene transcription, whereas the formation of MyoD-E47 heterodimers and their preferential binding to E-box DNA enhance transcription.
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Affiliation(s)
- Shulamit Etzioni
- Department of Biochemistry, Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, P. O. Box 9649 Bat Galim, Haifa 31096, Israel
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