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Zhang Z, Mlýnský V, Krepl M, Šponer J, Stadlbauer P. Mechanical Stability and Unfolding Pathways of Parallel Tetrameric G-Quadruplexes Probed by Pulling Simulations. J Chem Inf Model 2024; 64:3896-3911. [PMID: 38630447 PMCID: PMC11094737 DOI: 10.1021/acs.jcim.4c00227] [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: 02/08/2024] [Revised: 04/02/2024] [Accepted: 04/02/2024] [Indexed: 05/14/2024]
Abstract
Guanine quadruplex (GQ) is a noncanonical nucleic acid structure formed by guanine-rich DNA and RNA sequences. Folding of GQs is a complex process, where several aspects remain elusive, despite being important for understanding structure formation and biological functions of GQs. Pulling experiments are a common tool for acquiring insights into the folding landscape of GQs. Herein, we applied a computational pulling strategy─steered molecular dynamics (SMD) simulations─in combination with standard molecular dynamics (MD) simulations to explore the unfolding landscapes of tetrameric parallel GQs. We identified anisotropic properties of elastic conformational changes, unfolding transitions, and GQ mechanical stabilities. Using a special set of structural parameters, we found that the vertical component of pulling force (perpendicular to the average G-quartet plane) plays a significant role in disrupting GQ structures and weakening their mechanical stabilities. We demonstrated that the magnitude of the vertical force component depends on the pulling anchor positions and the number of G-quartets. Typical unfolding transitions for tetrameric parallel GQs involve base unzipping, opening of the G-stem, strand slippage, and rotation to cross-like structures. The unzipping was detected as the first and dominant unfolding event, and it usually started at the 3'-end. Furthermore, results from both SMD and standard MD simulations indicate that partial spiral conformations serve as a transient ensemble during the (un)folding of GQs.
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Affiliation(s)
- Zhengyue Zhang
- Institute
of Biophysics of the Czech Academy of Sciences, Královopolská 135, Brno 61200, Czech Republic
- CEITEC−Central
European Institute of Technology, Masaryk
University, Kamenice
5, Brno 625 00, Czech Republic
- National
Center for Biomolecular Research,
Faculty of Science, Masaryk University, Kamenice 5, Brno 625 00, Czech Republic
| | - Vojtěch Mlýnský
- Institute
of Biophysics of the Czech Academy of Sciences, Královopolská 135, Brno 61200, Czech Republic
| | - Miroslav Krepl
- Institute
of Biophysics of the Czech Academy of Sciences, Královopolská 135, Brno 61200, Czech Republic
| | - Jiří Šponer
- Institute
of Biophysics of the Czech Academy of Sciences, Královopolská 135, Brno 61200, Czech Republic
| | - Petr Stadlbauer
- Institute
of Biophysics of the Czech Academy of Sciences, Královopolská 135, Brno 61200, Czech Republic
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2
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Stadlbauer P, Mlýnský V, Krepl M, Šponer J. Complexity of Guanine Quadruplex Unfolding Pathways Revealed by Atomistic Pulling Simulations. J Chem Inf Model 2023; 63:4716-4731. [PMID: 37458574 PMCID: PMC10428220 DOI: 10.1021/acs.jcim.3c00171] [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: 02/02/2023] [Indexed: 08/15/2023]
Abstract
Guanine quadruplexes (GQs) are non-canonical nucleic acid structures involved in many biological processes. GQs formed in single-stranded regions often need to be unwound by cellular machinery, so their mechanochemical properties are important. Here, we performed steered molecular dynamics simulations of human telomeric GQs to study their unfolding. We examined four pulling regimes, including a very slow setup with pulling velocity and force load accessible to high-speed atomic force microscopy. We identified multiple factors affecting the unfolding mechanism, i.e.,: (i) the more the direction of force was perpendicular to the GQ channel axis (determined by GQ topology), the more the base unzipping mechanism happened, (ii) the more parallel the direction of force was, GQ opening and cross-like GQs were more likely to occur, (iii) strand slippage mechanism was possible for GQs with an all-anti pattern in a strand, and (iv) slower pulling velocity led to richer structural dynamics with sampling of more intermediates and partial refolding events. We also identified that a GQ may eventually unfold after a force drop under forces smaller than those that the GQ withstood before the drop. Finally, we found out that different unfolding intermediates could have very similar chain end-to-end distances, which reveals some limitations of structural interpretations of single-molecule spectroscopic data.
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Affiliation(s)
- Petr Stadlbauer
- Institute of Biophysics of the Czech
Academy of Sciences, Královopolská 135, Brno 612 00, Czech Republic
| | - Vojtěch Mlýnský
- Institute of Biophysics of the Czech
Academy of Sciences, Královopolská 135, Brno 612 00, Czech Republic
| | - Miroslav Krepl
- Institute of Biophysics of the Czech
Academy of Sciences, Královopolská 135, Brno 612 00, Czech Republic
| | - Jiří Šponer
- Institute of Biophysics of the Czech
Academy of Sciences, Královopolská 135, Brno 612 00, Czech Republic
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3
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Cheng Y, Zhang Y, You H. Characterization of G-Quadruplexes Folding/Unfolding Dynamics and Interactions with Proteins from Single-Molecule Force Spectroscopy. Biomolecules 2021; 11:1579. [PMID: 34827577 PMCID: PMC8615981 DOI: 10.3390/biom11111579] [Citation(s) in RCA: 15] [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: 09/16/2021] [Revised: 10/16/2021] [Accepted: 10/19/2021] [Indexed: 12/19/2022] Open
Abstract
G-quadruplexes (G4s) are stable secondary nucleic acid structures that play crucial roles in many fundamental biological processes. The folding/unfolding dynamics of G4 structures are associated with the replication and transcription regulation functions of G4s. However, many DNA G4 sequences can adopt a variety of topologies and have complex folding/unfolding dynamics. Determining the dynamics of G4s and their regulation by proteins remains challenging due to the coexistence of multiple structures in a heterogeneous sample. Here, in this mini-review, we introduce the application of single-molecule force-spectroscopy methods, such as magnetic tweezers, optical tweezers, and atomic force microscopy, to characterize the polymorphism and folding/unfolding dynamics of G4s. We also briefly introduce recent studies using single-molecule force spectroscopy to study the molecular mechanisms of G4-interacting proteins.
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Affiliation(s)
| | | | - Huijuan You
- Hubei Key Laboratory of Natural Medicinal Chemistry and Resource Evaluation, School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China; (Y.C.); (Y.Z.)
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4
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You H, Zhou Y, Yan J. Using Magnetic Tweezers to Unravel the Mechanism of the G-quadruplex Binding and Unwinding Activities of DHX36 Helicase. Methods Mol Biol 2021; 2209:175-191. [PMID: 33201470 DOI: 10.1007/978-1-0716-0935-4_12] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Single-molecule manipulation methods are useful techniques to probe the interactions of proteins and nucleic acid structures. Here, we describe the magnetic tweezers-based single-molecule investigation of the binding of helicases to G-quadruplex structures and their ATP-dependent unwinding activity, using DHX36 (also known as RHAU and G4R1) helicase and a DNA G-quadruplex structure for an example. We specifically emphasize on the principle and method to probe the interactions between DHX36 and the DNA G-quadruplex in different intermediate states during an ATPase cycle of DHX36, based on detecting the DHX36-induced changes in the lifetime of the DNA G-quadruplex under tension. The principle of the measurement can be broadly extended to the studies of other DNA or RNA G-quadruplex helicases.
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Affiliation(s)
- Huijuan You
- School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yu Zhou
- Mechanobiology Institute, National University of Singapore, Singapore, Singapore
| | - Jie Yan
- Mechanobiology Institute, National University of Singapore, Singapore, Singapore.
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5
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Shon MJ, Rah SH, Yoon TY. Submicrometer elasticity of double-stranded DNA revealed by precision force-extension measurements with magnetic tweezers. SCIENCE ADVANCES 2019; 5:eaav1697. [PMID: 31206015 PMCID: PMC6561745 DOI: 10.1126/sciadv.aav1697] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Accepted: 05/03/2019] [Indexed: 05/07/2023]
Abstract
Submicrometer elasticity of double-stranded DNA (dsDNA) governs nanoscale bending of DNA segments and their interactions with proteins. Single-molecule force spectroscopy, including magnetic tweezers (MTs), is an important tool for studying DNA mechanics. However, its application to short DNAs under 1 μm is limited. We developed an MT-based method for precise force-extension measurements in the 100-nm regime that enables in situ correction of the error in DNA extension measurement, and normalizes the force variability across beads by exploiting DNA hairpins. The method reduces the lower limit of tractable dsDNA length down to 198 base pairs (bp) (67 nm), an order-of-magnitude improvement compared to conventional tweezing experiments. Applying this method and the finite worm-like chain model we observed an essentially constant persistence length across the chain lengths studied (198 bp to 10 kbp), which steeply depended on GC content and methylation. This finding suggests a potential sequence-dependent mechanism for short-DNA elasticity.
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Affiliation(s)
- Min Ju Shon
- School of Biological Sciences and Institute for Molecular Biology and Genetics, Seoul National University, Seoul 08826, South Korea
- Corresponding author. (T.-Y.Y.); (M.J.S.)
| | - Sang-Hyun Rah
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, South Korea
| | - Tae-Young Yoon
- School of Biological Sciences and Institute for Molecular Biology and Genetics, Seoul National University, Seoul 08826, South Korea
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, South Korea
- Corresponding author. (T.-Y.Y.); (M.J.S.)
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6
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Abstract
Circular dichroism and stopped-flow UV spectroscopies were used to investigate the thermodynamic stability and the folding pathway of d[TGAG3TG3TAG3TG3TA2] at 25 °C in solutions containing 25 mM KCl. Under these conditions the oligonucleotide adopts a thermally stable, all-parallel G-quadruplex topography containing three stacked quartets. K+-induced folding shows three resolved relaxation times, each with distinctive spectral changes. Folding is complete within 200 s. These data indicate a folding pathway that involves at least two populated intermediates, one of which seems to be an antiparallel structure that rearranges to the final all-parallel conformation. Molecular dynamics reveals a stereochemically plausible folding pathway that does not involve complete unfolding of the intermediate. The rate of unfolding was determined using complementary DNA to trap transiently unfolded states to form a stable duplex. As assessed by 1D-1H NMR and fluorescence spectroscopy, unfolding is extremely slow with only one observable rate-limiting relaxation time.
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7
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Abstract
The genome-wide occurrence of G-quadruplexes and their demonstrated biological activities call for detailed understanding on the stability and transition kinetics of the structures. Although the core structural element in a G-quadruplex is simple and requires only four tandem repeats of Guanine rich sequences, there is rather rich conformational diversity in this structure. Corresponding to this structural diversity, it displays involved transition kinetics within individual G-quadruplexes and complicated interconversion among different G-quadruplex species. Due to the inherently high signal-to-noise ratio in the measurement, single-molecule tools offer a unique capability to investigate the thermodynamic, kinetic, and mechanical properties of G-quadruplexes with dynamic conformations. In this chapter, we describe different single molecule methods such as atomic-force microscopy (AFM), single-molecule fluorescence resonance energy transfer (smFRET), optical, magnetic, and magneto-optical tweezers to investigate G-quadruplex structures as well as their interactions with small-molecule ligands.
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Affiliation(s)
- Shankar Mandal
- Department of Chemistry and Biochemistry, Kent State University, Kent, OH, USA
| | | | - Hanbin Mao
- Department of Chemistry and Biochemistry, Kent State University, Kent, OH, USA.
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8
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Kar A, Jones N, Arat NÖ, Fishel R, Griffith JD. Long repeating (TTAGGG) n single-stranded DNA self-condenses into compact beaded filaments stabilized by G-quadruplex formation. J Biol Chem 2018; 293:9473-9485. [PMID: 29674319 PMCID: PMC6005428 DOI: 10.1074/jbc.ra118.002158] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Revised: 04/04/2018] [Indexed: 11/06/2022] Open
Abstract
Conformations adopted by long stretches of single-stranded DNA (ssDNA) are of central interest in understanding the architecture of replication forks, R loops, and other structures generated during DNA metabolism in vivo This is particularly so if the ssDNA consists of short nucleotide repeats. Such studies have been hampered by the lack of defined substrates greater than ∼150 nt and the absence of high-resolution biophysical approaches. Here we describe the generation of very long ssDNA consisting of the mammalian telomeric repeat (5'-TTAGGG-3') n , as well as the interrogation of its structure by EM and single-molecule magnetic tweezers (smMT). This repeat is of particular interest because it contains a run of three contiguous guanine residues capable of forming G quartets as ssDNA. Fluorescent-dye exclusion assays confirmed that this G-strand ssDNA forms ubiquitous G-quadruplex folds. EM revealed thick bead-like filaments that condensed the DNA ∼12-fold. The bead-like structures were 5 and 8 nm in diameter and linked by thin filaments. The G-strand ssDNA displayed initial stability to smMT force extension that ultimately released in steps that were multiples ∼28 nm at forces between 6 and 12 pN, well below the >20 pN required to unravel G-quadruplexes. Most smMT steps were consistent with the disruption of the beads seen by EM. Binding by RAD51 distinctively altered the force extension properties of the G-strand ssDNA, suggesting a stochastic G-quadruplex-dependent condensation model that is discussed.
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Affiliation(s)
- Anirban Kar
- From the Lineberger Comprehensive Cancer Center, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina 27599
| | - Nathan Jones
- the Department of Cancer Biology and Genetics, Ohio State University Wexner Medical Center, Columbus, Ohio 43210
- the Interdisciplinary Biophysics Graduate Program, Ohio State University, Columbus, Ohio 43210, and
| | - N Özlem Arat
- From the Lineberger Comprehensive Cancer Center, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina 27599
- the Institute for Research in Immunology and Cancer, University of Montreal, Montreal, Quebec H3T 1J4, Canada
| | - Richard Fishel
- the Department of Cancer Biology and Genetics, Ohio State University Wexner Medical Center, Columbus, Ohio 43210,
- the Interdisciplinary Biophysics Graduate Program, Ohio State University, Columbus, Ohio 43210, and
| | - Jack D Griffith
- From the Lineberger Comprehensive Cancer Center, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina 27599,
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9
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Gutiérrez I, Garavís M, de Lorenzo S, Villasante A, González C, Arias-Gonzalez JR. Single-Stranded Condensation Stochastically Blocks G-Quadruplex Assembly in Human Telomeric RNA. J Phys Chem Lett 2018; 9:2498-2503. [PMID: 29688724 DOI: 10.1021/acs.jpclett.8b00722] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
TERRA is an RNA molecule transcribed from human subtelomeric regions toward chromosome ends potentially involved in regulation of heterochromatin stability, semiconservative replication, and telomerase inhibition, among others. TERRA contains tandem repeats of the sequence GGGUUA, with a strong tendency to fold into a four-stranded arrangement known as a parallel G-quadruplex. Here, we demonstrate by using single-molecule force spectroscopy that this potential is limited by the inherent capacity of RNA to self-associate randomly and further condense into entropically more favorable structures. We stretched RNA constructions with more than four and less than eight hexanucleotide repeats, thus unable to form several G-quadruplexes in tandem, flanked by non-G-rich overhangs of random sequence by optical tweezers on a one by one basis. We found that condensed RNA stochastically blocks G-quadruplex folding pathways with a near 20% probability, a behavior that is not found in DNA analogous molecules.
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Affiliation(s)
- Irene Gutiérrez
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA Nanociencia) , Cantoblanco, 28049 Madrid , Spain
| | - Miguel Garavís
- Instituto de Química Física Rocasolano, CSIC , C/Serrano 119 , 28006 Madrid , Spain
| | - Sara de Lorenzo
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA Nanociencia) , Cantoblanco, 28049 Madrid , Spain
| | - Alfredo Villasante
- Centro de Biología Molecular "Severo Ochoa" CSIC-UAM , C/Nicolás Cabrera 1 , 28049 Madrid , Spain
| | - Carlos González
- Instituto de Química Física Rocasolano, CSIC , C/Serrano 119 , 28006 Madrid , Spain
| | - J Ricardo Arias-Gonzalez
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA Nanociencia) , Cantoblanco, 28049 Madrid , Spain
- CNB-CSIC-IMDEA Nanociencia Associated Unit "Unidad de Nanobiotecnología" , Cantoblanco, 28049 Madrid , Spain
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10
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Abstract
Genomes contain rare guanine-rich sequences capable of assembling into four-stranded helical structures, termed G-quadruplexes, with potential roles in gene regulation and chromosome stability. Their mechanical unfolding has only been reported to date by all-atom simulations, which cannot dissect the major physical interactions responsible for their cohesion. Here, we propose a mesoscopic model to describe both the mechanical and thermal stability of DNA G-quadruplexes, where each nucleotide of the structure, as well as each central cation located at the inner channel, is mapped onto a single bead. In this framework we are able to simulate loading rates similar to the experimental ones, which are not reachable in simulations with atomistic resolution. In this regard, we present single-molecule force-induced unfolding experiments by a high-resolution optical tweezers on a DNA telomeric sequence capable of adopting a G-quadruplex conformation. Fitting the parameters of the model to the experiments we find a correct prediction of the rupture-force kinetics and a good agreement with previous near equilibrium measurements. Since G-quadruplex unfolding dynamics is halfway in complexity between secondary nucleic acids and tertiary protein structures, our model entails a nanoscale paradigm for non-equilibrium processes in the cell.
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11
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Endoh T, Sugimoto N. Conformational Dynamics of mRNA in Gene Expression as New Pharmaceutical Target. CHEM REC 2017; 17:817-832. [DOI: 10.1002/tcr.201700016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Indexed: 11/05/2022]
Affiliation(s)
- Tamaki Endoh
- Frontier Institute for Biomolecular Engineering Research (FIBER); Konan University; 7-1-20 Minatojima-minamimachi Chuo-ku, Kobe 650-0047 Japan
| | - Naoki Sugimoto
- Frontier Institute for Biomolecular Engineering Research (FIBER); Konan University; 7-1-20 Minatojima-minamimachi Chuo-ku, Kobe 650-0047 Japan
- Graduate School of Frontiers of Innovative Research in Science and Technology (FIRST); Konan University; 7-1-20 Minatojima-minamimachi Chuo-ku, Kobe 650-0047 Japan
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12
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Dolinnaya NG, Ogloblina AM, Yakubovskaya MG. Structure, Properties, and Biological Relevance of the DNA and RNA G-Quadruplexes: Overview 50 Years after Their Discovery. BIOCHEMISTRY (MOSCOW) 2017; 81:1602-1649. [PMID: 28260487 PMCID: PMC7087716 DOI: 10.1134/s0006297916130034] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
G-quadruplexes (G4s), which are known to have important roles in regulation of key biological processes in both normal and pathological cells, are the most actively studied non-canonical structures of nucleic acids. In this review, we summarize the results of studies published in recent years that change significantly scientific views on various aspects of our understanding of quadruplexes. Modern notions on the polymorphism of DNA quadruplexes, on factors affecting thermodynamics and kinetics of G4 folding–unfolding, on structural organization of multiquadruplex systems, and on conformational features of RNA G4s and hybrid DNA–RNA G4s are discussed. Here we report the data on location of G4 sequence motifs in the genomes of eukaryotes, bacteria, and viruses, characterize G4-specific small-molecule ligands and proteins, as well as the mechanisms of their interactions with quadruplexes. New information on the structure and stability of G4s in telomeric DNA and oncogene promoters is discussed as well as proof being provided on the occurrence of G-quadruplexes in cells. Prominence is given to novel experimental techniques (single molecule manipulations, optical and magnetic tweezers, original chemical approaches, G4 detection in situ, in-cell NMR spectroscopy) that facilitate breakthroughs in the investigation of the structure and functions of G-quadruplexes.
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Affiliation(s)
- N G Dolinnaya
- Lomonosov Moscow State University, Department of Chemistry, Moscow, 119991, Russia.
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13
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Mechanical insights into ribosomal progression overcoming RNA G-quadruplex from periodical translation suppression in cells. Sci Rep 2016; 6:22719. [PMID: 26948955 PMCID: PMC4780275 DOI: 10.1038/srep22719] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Accepted: 02/18/2016] [Indexed: 01/10/2023] Open
Abstract
G-quadruplexes formed on DNA and RNA can be roadblocks to movement of polymerases and ribosome on template nucleotides. Although folding and unfolding processes of the G-quadruplexes are deliberately studied in vitro, how the mechanical and physical properties of the G-quadruplexes affect intracellular biological systems is still unclear. In this study, mRNAs with G-quadruplex forming sequences located either in the 5′ untranslated region (UTR) or in the open reading frame (ORF) were constructed to evaluate positional effects of the G-quadruplex on translation suppression in cells. Periodic fluctuation of translation suppression was observed at every three nucleotides within the ORF but not within the 5′ UTR. The results suggested that difference in motion of ribosome at the 5′ UTR and the ORF determined the ability of the G-quadruplex structure to act as a roadblock to translation in cells and provided mechanical insights into ribosomal progression to overcome the roadblock.
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14
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Klejevskaja B, Pyne ALB, Reynolds M, Shivalingam A, Thorogate R, Hoogenboom BW, Ying L, Vilar R. Studies of G-quadruplexes formed within self-assembled DNA mini-circles. Chem Commun (Camb) 2016; 52:12454-12457. [DOI: 10.1039/c6cc07110d] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
We have developed self-assembled DNA mini-circles that contain a G-quadruplex-forming sequence and demonstrate by FRET that the G-quadruplex unfolding kinetics are 10-fold slower than for the simpler 24-mer G-quadruplex that is commonly used for FRET experiments.
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Affiliation(s)
- Beata Klejevskaja
- Department of Chemistry
- Imperial College London
- London
- UK
- Institute of Chemical Biology
| | - Alice L. B. Pyne
- London Centre for Nanotechnology
- University College London
- London
- UK
| | | | | | | | - Bart W. Hoogenboom
- London Centre for Nanotechnology
- University College London
- London
- UK
- Department of Physics and Astronomy
| | - Liming Ying
- Institute of Chemical Biology
- Imperial College London
- London
- UK
- Molecular Medicine
| | - Ramon Vilar
- Department of Chemistry
- Imperial College London
- London
- UK
- Institute of Chemical Biology
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15
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Ray A, Panigrahi S, Bhattacharyya D. A comparison of four different conformations adopted by human telomeric G-quadruplex using computer simulations. Biopolymers 2015; 105:83-99. [PMID: 26448055 DOI: 10.1002/bip.22751] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Revised: 10/01/2015] [Accepted: 10/03/2015] [Indexed: 01/06/2023]
Abstract
The telomeric G-quadruplexes for their unique structural features are considered as potential anticancer drug targets. These, however, exhibit structural polymorphism as different topology types for the intra-molecular G-quadruplexes from human telomeric G-rich sequences have been reported based on NMR spectroscopy and X-ray crystallography. These techniques provide detailed atomic-level information about the molecule but relative conformational stability of the different topologies remains unsolved. Therefore, to understand the conformational preference, we have carried out quantum chemical calculations on G-quartets; used all-atom molecular dynamics (MD) simulations and steered molecular dynamics (SMD) simulations to characterize the four human telomeric G-quadruplex topologies based on its G-tetrad core-types, viz., parallel, anti-parallel, mixed-(3 + 1)-form1 and mixed-(3 + 1)-form2. We have also studied a non-telomeric sequence along with these telomeric forms giving a comparison between the two G-rich forms. The structural properties such as base pairing, stacking geometry and backbone conformations have been analyzed. The quantum calculations indicate that presence of a sodium ion inside the G-tetrad plane or two potassium ions on both sides of the plane give it an overall planarity which is much needed for good stacking to form a helix. MD simulations indicate that capping of the G-tetrad core by the TTA loops keep the terminal guanine bases away from water. The SMD simulations along with equilibrium MD studies indicate that the parallel and non-telomeric forms are comparatively less stable. We could come to the conclusion that the anti-parallel form and also the mixed-(3 + 1)-form1 topology are most likely to represent the major conformation., 2016. © 2015 Wiley Periodicals, Inc. Biopolymers 105: 83-99, 2016.
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Affiliation(s)
- Angana Ray
- Computational Science Division, Saha Institute of Nuclear Physics, Kolkata, 700064, India
| | - Swati Panigrahi
- Computational Science Division, Saha Institute of Nuclear Physics, Kolkata, 700064, India
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16
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Tan X, Litau S, Zhang X, Müller J. Single-Molecule Force Spectroscopy of an Artificial DNA Duplex Comprising a Silver(I)-Mediated Base Pair. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:11305-11310. [PMID: 26421907 DOI: 10.1021/acs.langmuir.5b03183] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Single-molecule force spectroscopy measurements of a DNA duplex comprising an artificial metal-mediated base pair are reported. The measurements reveal that DNA duplexes comprising one central imidazole:imidazole mispair rupture at lower forces than a related duplex with canonical base pairs only. In contrast, DNA duplexes with one central imidazole-Ag(+)-imidazole base pair (formed by the addition of Ag(+) to the aforementioned duplex with the mispair) rupture at higher forces. These measurements indicate for the first time that the increase in thermal stability of a nucleic acid duplex that is observed upon the formation of a metal-mediated base pair is accompanied by a concomitant mechanical stabilization. In fact, the mechanical stabilization even exceeds the thermal one. This result indicates that nucleic acids with metal-mediated base pairs should be ideal building blocks for rigid functionalized DNA nano-objects.
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Affiliation(s)
- Xinxin Tan
- Department of Chemistry, Key Lab of Organic Optoelectronics and Molecular Engineering, Tsinghua University , Beijing 100084, P. R. China
| | - Stefanie Litau
- Institut für Anorganische und Analytische Chemie, Westfälische Wilhelms-Universität Münster , Corrensstr. 28/30, 48149 Münster, Germany
| | - Xi Zhang
- Department of Chemistry, Key Lab of Organic Optoelectronics and Molecular Engineering, Tsinghua University , Beijing 100084, P. R. China
| | - Jens Müller
- Institut für Anorganische und Analytische Chemie, Westfälische Wilhelms-Universität Münster , Corrensstr. 28/30, 48149 Münster, Germany
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Bergues-Pupo AE, Arias-Gonzalez JR, Morón MC, Fiasconaro A, Falo F. Role of the central cations in the mechanical unfolding of DNA and RNA G-quadruplexes. Nucleic Acids Res 2015; 43:7638-47. [PMID: 26170233 PMCID: PMC4551928 DOI: 10.1093/nar/gkv690] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Accepted: 06/23/2015] [Indexed: 12/20/2022] Open
Abstract
Cations are known to mediate diverse interactions in nucleic acids duplexes but they are critical in the arrangement of four-stranded structures. Here, we use all-atom molecular dynamics simulations with explicit solvent to analyse the mechanical unfolding of representative intramolecular G-quadruplex structures: a parallel, a hybrid and an antiparallel DNA and a parallel RNA, in the presence of stabilising cations. We confirm the stability of these conformations in the presence of \documentclass[12pt]{minimal}
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}{}$\rm {K}^+$\end{document} central ions and observe distortions from the tetrad topology in their absence. Force-induced unfolding dynamics is then investigated. We show that the unfolding events in the force-extension curves are concomitant to the loss of coordination between the central ions and the guanines of the G-quadruplex. We found lower ruptures forces for the parallel configuration with respect to the antiparallel one, while the behaviour of the force pattern of the parallel RNA appears similar to the parallel DNA. We anticipate that our results will be essential to interpret the fine structure rupture profiles in stretching assays at high resolution and will shed light on the mechanochemical activity of G-quadruplex-binding machinery.
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Affiliation(s)
- Ana Elisa Bergues-Pupo
- Departamento de Física de la Materia Condensada, Facultad de Ciencias, Universidad de Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza, Spain Instituto de Biocomputación y Física de Sistemas Complejos (BIFI), Universidad de Zaragoza, Mariano Esquillor, 50018 Zaragoza, Spain Departamento de Física, Universidad de Oriente, 90500 Santiago de Cuba, Cuba
| | - J Ricardo Arias-Gonzalez
- Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA Nanociencia), Cantoblanco, 28049 Madrid, Spain CNB-CSIC-IMDEA Nanociencia Associated Unit 'Unidad de Nanobiotecnología, Madrid, Spain'
| | - María Carmen Morón
- Departamento de Física de la Materia Condensada, Facultad de Ciencias, Universidad de Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza, Spain Instituto de Ciencia de Materiales de Aragón (ICMA), Consejo Superior de Investigaciones Científicas, Universidad de Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza, Spain
| | - Alessandro Fiasconaro
- School of Mathematical Sciences, Queen Mary University of London - Mile End Road, London E1 4NS, UK
| | - Fernando Falo
- Departamento de Física de la Materia Condensada, Facultad de Ciencias, Universidad de Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza, Spain Instituto de Biocomputación y Física de Sistemas Complejos (BIFI), Universidad de Zaragoza, Mariano Esquillor, 50018 Zaragoza, Spain
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18
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Molecular mechanism of G-quadruplex unwinding helicase: sequential and repetitive unfolding of G-quadruplex by Pif1 helicase. Biochem J 2015; 466:189-99. [PMID: 25471447 DOI: 10.1042/bj20140997] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Recent advances in G-quadruplex (G4) studies have confirmed that G4 structures exist in living cells and may have detrimental effects on various DNA transactions. How helicases resolve G4, however, has just begun to be studied and remains largely unknown. In the present paper, we use single-molecule fluorescence assays to probe Pif1-catalysed unfolding of G4 in a DNA construct resembling an ongoing synthesis of lagging strand stalled by G4. Strikingly, Pif1 unfolds and then halts at the ss/dsDNA junction, followed by rapid reformation of G4 and 'acrobatic' re-initiation of unfolding by the same monomer. Thus, Pif1 unfolds single G4 structures repetitively. Furthermore, it is found that Pif1 unfolds G4 sequentially in two large steps. Our study has revealed that, as a stable intermediate, G-triplex (G3) plays an essential role in this process. The repetitive unfolding activity may facilitate Pif1 disrupting the continuously reforming obstructive G4 structures to rescue a stalled replication fork. The proposed mechanism for step-wise unfolding of G4 is probably applicable to other helicases that resolve G4 structures for maintaining genome stability.
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Dzubiel D, Ihmels H, Mahmoud MMA, Thomas L. A comparative study of the interactions of cationic hetarenes with quadruplex-DNA forming oligonucleotide sequences of the insulin-linked polymorphic region (ILPR). Beilstein J Org Chem 2014; 10:2963-74. [PMID: 25550763 PMCID: PMC4273293 DOI: 10.3762/bjoc.10.314] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2014] [Accepted: 11/26/2014] [Indexed: 11/23/2022] Open
Abstract
The interactions of the ILPR sequence (ILPR = "insulin-linked polymorphic region") a2 [d(ACAG4TGTG4ACAG4TGTG4)] with [2.2.2]heptamethinecyanine derivatives 1a–e and with the already established quadruplex ligands coralyne (2), 3,3′-[2,6-pyridinediylbis(carbonylimino)]bis[1-methylquinolinium] (3), 4,4′,4′′,4′′′-(21H,23H-porphine-5,10,15,20-tetrayl)tetrakis[1-methylpyridinium] (4), naphtho[2,1-b:3,4-b′:6,5-b′′:7,8-b′′′]tetraquinolizinium (5) and thiazole orange (6) were studied. It is demonstrated with absorption, fluorescence and CD spectroscopy that all investigated ligands bind with relatively high affinity to the ILPR-quadruplex DNA a2 (0.2–5.5 × 106 M−1) and that in most cases the binding parameters of ligand-ILPR complexes are different from the ones observed with other native quadruplex-forming DNA sequences.
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Affiliation(s)
- Darinka Dzubiel
- Department Chemie-Biologie, Universität Siegen, Adolf-Reichwein-Str. 2, 57068 Siegen, Germany
| | - Heiko Ihmels
- Department Chemie-Biologie, Universität Siegen, Adolf-Reichwein-Str. 2, 57068 Siegen, Germany
| | - Mohamed M A Mahmoud
- Department Chemie-Biologie, Universität Siegen, Adolf-Reichwein-Str. 2, 57068 Siegen, Germany
| | - Laura Thomas
- Department Chemie-Biologie, Universität Siegen, Adolf-Reichwein-Str. 2, 57068 Siegen, Germany
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Abstract
Folding may be described conceptually in terms of trajectories over a landscape of free energies corresponding to different molecular configurations. In practice, energy landscapes can be difficult to measure. Single-molecule force spectroscopy (SMFS), whereby structural changes are monitored in molecules subjected to controlled forces, has emerged as a powerful tool for probing energy landscapes. We summarize methods for reconstructing landscapes from force spectroscopy measurements under both equilibrium and nonequilibrium conditions. Other complementary, but technically less demanding, methods provide a model-dependent characterization of key features of the landscape. Once reconstructed, energy landscapes can be used to study critical folding parameters, such as the characteristic transition times required for structural changes and the effective diffusion coefficient setting the timescale for motions over the landscape. We also discuss issues that complicate measurement and interpretation, including the possibility of multiple states or pathways and the effects of projecting multiple dimensions onto a single coordinate.
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Affiliation(s)
- Michael T Woodside
- Department of Physics, University of Alberta, Edmonton, Alberta T6G2E1, Canada;
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21
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Leuchter JD, Green AT, Gilyard J, Rambarat CG, Cho SS. Coarse-Grained and Atomistic MD Simulations of RNA and DNA Folding. Isr J Chem 2014. [DOI: 10.1002/ijch.201400022] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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22
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Interrogating biology with force: single molecule high-resolution measurements with optical tweezers. Biophys J 2014; 105:1293-303. [PMID: 24047980 DOI: 10.1016/j.bpj.2013.08.007] [Citation(s) in RCA: 108] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Revised: 07/26/2013] [Accepted: 08/07/2013] [Indexed: 11/20/2022] Open
Abstract
Single molecule force spectroscopy methods, such as optical and magnetic tweezers and atomic force microscopy, have opened up the possibility to study biological processes regulated by force, dynamics of structural conformations of proteins and nucleic acids, and load-dependent kinetics of molecular interactions. Among the various tools available today, optical tweezers have recently seen great progress in terms of spatial resolution, which now allows the measurement of atomic-scale conformational changes, and temporal resolution, which has reached the limit of the microsecond-scale relaxation times of biological molecules bound to a force probe. Here, we review different strategies and experimental configurations recently developed to apply and measure force using optical tweezers. We present the latest progress that has pushed optical tweezers' spatial and temporal resolution down to today's values, discussing the experimental variables and constraints that are influencing measurement resolution and how these can be optimized depending on the biological molecule under study.
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Lavelle C. Pack, unpack, bend, twist, pull, push: the physical side of gene expression. Curr Opin Genet Dev 2014; 25:74-84. [PMID: 24576847 DOI: 10.1016/j.gde.2014.01.001] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Accepted: 01/03/2014] [Indexed: 12/31/2022]
Abstract
Molecular motors such as polymerases produce physical constraints on DNA and chromatin. Recent techniques, in particular single-molecule micromanipulation, provide estimation of the forces and torques at stake. These biophysical approaches have improved our understanding of chromatin behaviour under physiological physical constraints and should, in conjunction with genome wide and in vivo studies, help to build more realistic mechanistic models of transcription in the context of chromatin. Here, we wish to provide a brief overview of our current knowledge in the field, and emphasize at the same time the importance of DNA supercoiling as a major parameter in gene regulation.
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Affiliation(s)
- Christophe Lavelle
- National Museum of Natural History, Paris, France; CNRS UMR7196, Paris, France; INSERM U1154, Paris, France; Nuclear Architecture and Dynamics, CNRS GDR3536, Paris, France.
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Lin J, Kaur P, Countryman P, Opresko PL, Wang H. Unraveling secrets of telomeres: one molecule at a time. DNA Repair (Amst) 2014; 20:142-153. [PMID: 24569170 DOI: 10.1016/j.dnarep.2014.01.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2013] [Revised: 01/03/2014] [Accepted: 01/13/2014] [Indexed: 01/23/2023]
Abstract
Telomeres play important roles in maintaining the stability of linear chromosomes. Telomere maintenance involves dynamic actions of multiple proteins interacting with long repetitive sequences and complex dynamic DNA structures, such as G-quadruplexes, T-loops and t-circles. Given the heterogeneity and complexity of telomeres, single-molecule approaches are essential to fully understand the structure-function relationships that govern telomere maintenance. In this review, we present a brief overview of the principles of single-molecule imaging and manipulation techniques. We then highlight results obtained from applying these single-molecule techniques for studying structure, dynamics and functions of G-quadruplexes, telomerase, and shelterin proteins.
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Affiliation(s)
- Jiangguo Lin
- Physics Department, North Carolina State University, Raleigh, NC 27695, USA
| | - Parminder Kaur
- Physics Department, North Carolina State University, Raleigh, NC 27695, USA
| | - Preston Countryman
- Physics Department, North Carolina State University, Raleigh, NC 27695, USA
| | - Patricia L Opresko
- Department of Environmental and Occupational Health, University of Pittsburgh Graduate School of Public Health, Pittsburgh, PA 15219, USA
| | - Hong Wang
- Physics Department, North Carolina State University, Raleigh, NC 27695, USA.
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25
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Yangyuoru PM, Zhang AYQ, Shi Z, Koirala D, Balasubramanian S, Mao H. Mechanochemical Properties of Individual Human Telomeric RNA (TERRA) G-Quadruplexes. Chembiochem 2013; 14:1931-5. [DOI: 10.1002/cbic.201300350] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Indexed: 12/12/2022]
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26
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Savage AL, Bubb VJ, Breen G, Quinn JP. Characterisation of the potential function of SVA retrotransposons to modulate gene expression patterns. BMC Evol Biol 2013; 13:101. [PMID: 23692647 PMCID: PMC3667099 DOI: 10.1186/1471-2148-13-101] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Accepted: 05/15/2013] [Indexed: 12/24/2022] Open
Abstract
Background Retrotransposons are a major component of the human genome constituting as much as 45%. The hominid specific SINE-VNTR-Alus are the youngest of these elements constituting 0.13% of the genome; they are therefore a practical and amenable group for analysis of both their global integration, polymorphic variation and their potential contribution to modulation of genome regulation. Results Consistent with insertion into active chromatin we have determined that SVAs are more prevalent in genic regions compared to gene deserts. The consequence of which, is that their integration has greater potential to have affects on gene regulation. The sequences of SVAs show potential for the formation of secondary structure including G-quadruplex DNA. We have shown that the human specific SVA subtypes (E-F1) show the greatest potential for forming G-quadruplexes within the central tandem repeat component in addition to the 5’ ‘CCCTCT’ hexamer. We undertook a detailed analysis of the PARK7 SVA D, located in the promoter of the PARK7 gene (also termed DJ-1), in a HapMap cohort where we identified 2 variable number tandem repeat domains and 1 tandem repeat within this SVA with the 5’ CCCTCT element being one of the variable regions. Functionally we were able to demonstrate that this SVA contains multiple regulatory elements that support reporter gene expression in vitro and further show these elements exhibit orientation dependency. Conclusions Our data supports the hypothesis that SVAs integrate preferentially in to open chromatin where they could modify the existing transcriptional regulatory domains or alter expression patterns by a variety of mechanisms.
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Affiliation(s)
- Abigail L Savage
- Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, The University of Liverpool, Liverpool L69 3BX, UK
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Li W, Hou XM, Wang PY, Xi XG, Li M. Direct measurement of sequential folding pathway and energy landscape of human telomeric G-quadruplex structures. J Am Chem Soc 2013; 135:6423-6. [PMID: 23631592 DOI: 10.1021/ja4019176] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Single-stranded guanine-rich sequences fold into compact G-quadruplexes. Although G-triplexes have been proposed and demonstrated as intermediates in the folding of G-quadruplexes, there is still a debate on their folding pathways. In this work, we employed magnetic tweezers to investigate the folding kinetics of single human telomeric G-quadruplexes in 100 mM Na(+) buffer. The results are consistent with a model in which the G-triplex is an in-pathway intermediate in the folding of the G-quadruplex. By finely tuning the force exerted on the G-quadruplex, we observed reversible transitions from the G-quadruplex to the G-triplex as well as from the G-triplex to the unfolded coil when the force was increased from 26 to 39 pN. The energy landscape derived from the probability distribution shows clearly that the G-quadruplex goes through an intermediate when it is unfolded, and vice versa.
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Affiliation(s)
- Wei Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
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28
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Yu Z, Mao H. Non-B DNA structures show diverse conformations and complex transition kinetics comparable to RNA or proteins--a perspective from mechanical unfolding and refolding experiments. CHEM REC 2013; 13:102-16. [PMID: 23389854 DOI: 10.1002/tcr.201200021] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2012] [Indexed: 01/03/2023]
Abstract
With the firm demonstration of the in vivo presence and biological functions of many non-B DNA structures, it is of great significance to understand their physiological roles from the perspective of structural conformation, stability, and transition kinetics. Although relatively simple in primary sequences compared to proteins, non-B DNA species show rather versatile conformations and dynamic transitions. As the most-studied non-B DNA species, the G-quadruplex displays a myriad of conformations that can interconvert between each other in different solutions. These features impose challenges for ensemble-average techniques, such as X-ray crystallography, NMR spectroscopy, and circular dichroism (CD), but leave room for single-molecular approaches to illustrate the structure, stability, and transition kinetics of individual non-B DNA species in a solution mixture. Deconvolution of the mixture can be further facilitated by statistical data treatment, such as iPoDNano (integrated population deconvolution with nanometer resolution), which resolves populations with subnanometer size differences. This Personal Account summarizes current mechanical unfolding and refolding methods to interrogate single non-B DNA species, with an emphasis on DNA G-quadruplexes and i-motifs. These single-molecule studies start to demonstrate that structures and transitions in non-B DNA species can approach the complexity of those in RNA or proteins, which provides solid justification for the biological functions carried out by non-B DNA species.
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Affiliation(s)
- Zhongbo Yu
- Department of Chemistry and Biochemistry, Kent State University, Kent, Ohio 44242, USA
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29
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Long X, Parks JW, Bagshaw CR, Stone MD. Mechanical unfolding of human telomere G-quadruplex DNA probed by integrated fluorescence and magnetic tweezers spectroscopy. Nucleic Acids Res 2013; 41:2746-55. [PMID: 23303789 PMCID: PMC3575832 DOI: 10.1093/nar/gks1341] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Single-molecule techniques facilitate analysis of mechanical transitions within nucleic acids and proteins. Here, we describe an integrated fluorescence and magnetic tweezers instrument that permits detection of nanometer-scale DNA structural rearrangements together with the application of a wide range of stretching forces to individual DNA molecules. We have analyzed the force-dependent equilibrium and rate constants for telomere DNA G-quadruplex (GQ) folding and unfolding, and have determined the location of the transition state barrier along the well-defined DNA-stretching reaction coordinate. Our results reveal the mechanical unfolding pathway of the telomere DNA GQ is characterized by a short distance (<1 nm) to the transition state for the unfolding reaction. This mechanical unfolding response reflects a critical contribution of long-range interactions to the global stability of the GQ fold, and suggests that telomere-associated proteins need only disrupt a few base pairs to destabilize GQ structures. Comparison of the GQ unfolded state with a single-stranded polyT DNA revealed the unfolded GQ exhibits a compacted non-native conformation reminiscent of the protein molten globule. We expect the capacity to interrogate macromolecular structural transitions with high spatial resolution under conditions of low forces will have broad application in analyses of nucleic acid and protein folding.
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Affiliation(s)
- Xi Long
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, Santa Cruz, CA 95064, USA
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30
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Garavís M, Bocanegra R, Herrero-Galán E, González C, Villasante A, Arias-Gonzalez JR. Mechanical unfolding of long human telomeric RNA (TERRA). Chem Commun (Camb) 2013; 49:6397-9. [DOI: 10.1039/c3cc42981d] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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