1
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Trajkovski M, Pastore A, Plavec J. Dimeric structures of DNA ATTTC repeats promoted by divalent cations. Nucleic Acids Res 2024; 52:1591-1601. [PMID: 38296828 PMCID: PMC10899783 DOI: 10.1093/nar/gkae052] [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: 10/26/2023] [Revised: 01/10/2024] [Accepted: 01/16/2024] [Indexed: 02/02/2024] Open
Abstract
Structural studies of repetitive DNA sequences may provide insights why and how certain repeat instabilities in their number and nucleotide sequence are managed or even required for normal cell physiology, while genomic variability associated with repeat expansions may also be disease-causing. The pentanucleotide ATTTC repeats occur in hundreds of genes important for various cellular processes, while their insertion and expansion in noncoding regions are associated with neurodegeneration, particularly with subtypes of spinocerebellar ataxia and familial adult myoclonic epilepsy. We describe a new striking domain-swapped DNA-DNA interaction triggered by the addition of divalent cations, including Mg2+ and Ca2+. The results of NMR characterization of d(ATTTC)3 in solution show that the oligonucleotide folds into a novel 3D architecture with two central C:C+ base pairs sandwiched between a couple of T:T base pairs. This structural element, referred to here as the TCCTzip, is characterized by intercalative hydrogen-bonding, while the nucleobase moieties are poorly stacked. The 5'- and 3'-ends of TCCTzip motif are connected by stem-loop segments characterized by A:T base pairs and stacking interactions. Insights embodied in the non-canonical DNA structure are expected to advance our understanding of why only certain pyrimidine-rich DNA repeats appear to be pathogenic, while others can occur in the human genome without any harmful consequences.
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Affiliation(s)
- Marko Trajkovski
- Slovenian NMR Centre, National Institute of Chemistry, 1000 Ljubljana, Slovenia
| | - Annalisa Pastore
- King's College London, the Maurice Wohl Clinical Neuroscience Institute, London, UK
| | - Janez Plavec
- Slovenian NMR Centre, National Institute of Chemistry, 1000 Ljubljana, Slovenia
- Faculty of Chemistry and Chemical Technology, University of Ljubljana, 1000 Ljubljana, Slovenia
- EN-FIST, Center of Excellence, 1000 Ljubljana, Slovenia
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2
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Narum S, Deal B, Ogasawara H, Mancuso JN, Zhang J, Salaita K. An Endosomal Escape Trojan Horse Platform to Improve Cytosolic Delivery of Nucleic Acids. ACS NANO 2024; 18:6186-6201. [PMID: 38346399 PMCID: PMC10906071 DOI: 10.1021/acsnano.3c09027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Revised: 12/11/2023] [Accepted: 12/26/2023] [Indexed: 02/17/2024]
Abstract
Endocytosis is a major bottleneck toward cytosolic delivery of nucleic acids, as the vast majority of nucleic acid drugs remain trapped within endosomes. Current trends to overcome endosomal entrapment and subsequent degradation provide varied success; however, active delivery agents such as cell-penetrating peptides have emerged as a prominent strategy to improve cytosolic delivery. Yet, these membrane-active agents have poor selectivity for endosomal membranes, leading to toxicity. A hallmark of endosomes is their acidic environment, which aids in degradation of foreign materials. Here, we develop a pH-triggered spherical nucleic acid that provides smart antisense oligonucleotide (ASO) release upon endosomal acidification and selective membrane disruption, termed DNA EndosomaL Escape Vehicle Response (DELVR). We anchor i-Motif DNA to a nanoparticle (AuNP), where the complement strand contains both an ASO sequence and a functionalized endosomal escape peptide (EEP). By orienting the EEP toward the AuNP core, the EEP is inactive until it is released through acidification-induced i-Motif folding. In this study, we characterize a small library of i-Motif duplexes to develop a structure-switching nucleic acid sequence triggered by endosomal acidification. We evaluate antisense efficacy using HIF1a, a hypoxic indicator upregulated in many cancers, and demonstrate dose-dependent activity through RT-qPCR. We show that DELVR significantly improves ASO efficacy in vitro. Finally, we use fluorescence lifetime imaging and activity measurement to show that DELVR benefits synergistically from nuclease- and pH-driven release strategies with increased ASO endosomal escape efficiency. Overall, this study develops a modular platform that improves the cytosolic delivery of nucleic acid therapeutics and offers key insights for overcoming intracellular barriers.
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Affiliation(s)
- Steven Narum
- Department
of Biomedical Engineering, Georgia Institute
of Technology and Emory University, Atlanta, Georgia 30322, United States
| | - Brendan Deal
- Department
of Chemistry, Emory University, Atlanta, Georgia 30322, United States
| | - Hiroaki Ogasawara
- Department
of Chemistry, Emory University, Atlanta, Georgia 30322, United States
| | | | - Jiahui Zhang
- Department
of Biomedical Engineering, Georgia Institute
of Technology and Emory University, Atlanta, Georgia 30322, United States
| | - Khalid Salaita
- Department
of Biomedical Engineering, Georgia Institute
of Technology and Emory University, Atlanta, Georgia 30322, United States
- Department
of Chemistry, Emory University, Atlanta, Georgia 30322, United States
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3
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Guneri D, Waller ZAE. Utility of intercalator displacement assays for screening of ligands for i-motif DNA structures. Methods Enzymol 2024; 695:221-232. [PMID: 38521586 DOI: 10.1016/bs.mie.2023.12.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/25/2024]
Abstract
Cytosine rich sequences can form intercalated, i-motif DNA structures stabilized by hemi-protonated cytosine:cytosine base pairing. These sequences are often located in regulatory regions of genes such as promoters. Ligands targeting i-motif structures may provide potential leads for treatments for genetic disease. The focus on ligands interacting with i-motif DNA has been increasing in recent years. Here, we describe the fluorescent intercalator displacement (FID) assay using thiazole orange binding i-motif DNA and assess the binding affinity of a ligand to the i-motif DNA by displacing thiazole orange. This provides a time and cost-effective high throughput screening of ligands against secondary DNA structures for hit identification.
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Affiliation(s)
- Dilek Guneri
- School of Pharmacy, University College London, London, United Kingdom.
| | - Zoë A E Waller
- School of Pharmacy, University College London, London, United Kingdom.
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4
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Williams SL, Casas‐Delucchi CS, Raguseo F, Guneri D, Li Y, Minamino M, Fletcher EE, Yeeles JTP, Keyser UF, Waller ZAE, Di Antonio M, Coster G. Replication-induced DNA secondary structures drive fork uncoupling and breakage. EMBO J 2023; 42:e114334. [PMID: 37781931 PMCID: PMC10646557 DOI: 10.15252/embj.2023114334] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 09/20/2023] [Accepted: 09/21/2023] [Indexed: 10/03/2023] Open
Abstract
Sequences that form DNA secondary structures, such as G-quadruplexes (G4s) and intercalated-Motifs (iMs), are abundant in the human genome and play various physiological roles. However, they can also interfere with replication and threaten genome stability. Multiple lines of evidence suggest G4s inhibit replication, but the underlying mechanism remains unclear. Moreover, evidence of how iMs affect the replisome is lacking. Here, we reconstitute replication of physiologically derived structure-forming sequences to find that a single G4 or iM arrest DNA replication. Direct single-molecule structure detection within solid-state nanopores reveals structures form as a consequence of replication. Combined genetic and biophysical characterisation establishes that structure stability and probability of structure formation are key determinants of replisome arrest. Mechanistically, replication arrest is caused by impaired synthesis, resulting in helicase-polymerase uncoupling. Significantly, iMs also induce breakage of nascent DNA. Finally, stalled forks are only rescued by a specialised helicase, Pif1, but not Rrm3, Sgs1, Chl1 or Hrq1. Altogether, we provide a mechanism for quadruplex structure formation and resolution during replication and highlight G4s and iMs as endogenous sources of replication stress.
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Affiliation(s)
- Sophie L Williams
- Genome Replication Lab, Division of Cancer Biology, Institute of Cancer ResearchChester Beatty LaboratoriesLondonUK
| | - Corella S Casas‐Delucchi
- Genome Replication Lab, Division of Cancer Biology, Institute of Cancer ResearchChester Beatty LaboratoriesLondonUK
| | - Federica Raguseo
- Chemistry DepartmentImperial College London, MSRHLondonUK
- Institute of Chemical Biology, MSRHLondonUK
| | | | - Yunxuan Li
- Cavendish LaboratoryUniversity of CambridgeCambridgeUK
| | | | | | | | | | | | - Marco Di Antonio
- Chemistry DepartmentImperial College London, MSRHLondonUK
- Institute of Chemical Biology, MSRHLondonUK
- Francis Crick InstituteLondonUK
| | - Gideon Coster
- Genome Replication Lab, Division of Cancer Biology, Institute of Cancer ResearchChester Beatty LaboratoriesLondonUK
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5
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i-Motif folding intermediates with zero-nucleotide loops are trapped by 2'-fluoroarabinocytidine via F···H and O···H hydrogen bonds. Commun Chem 2023; 6:31. [PMID: 36797370 PMCID: PMC9935537 DOI: 10.1038/s42004-023-00831-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Accepted: 02/03/2023] [Indexed: 02/18/2023] Open
Abstract
G-quadruplex and i-motif nucleic acid structures are believed to fold through kinetic partitioning mechanisms. Such mechanisms explain the structural heterogeneity of G-quadruplex metastable intermediates which have been extensively reported. On the other hand, i-motif folding is regarded as predictable, and research on alternative i-motif folds is limited. While TC5 normally folds into a stable tetrameric i-motif in solution, we report that 2'-deoxy-2'-fluoroarabinocytidine (araF-C) substitutions can prompt TC5 to form an off-pathway and kinetically-trapped dimeric i-motif, thereby expanding the scope of i-motif folding landscapes. This i-motif is formed by two strands, associated head-to-head, and featuring zero-nucleotide loops which have not been previously observed. Through spectroscopic and computational analyses, we also establish that the dimeric i-motif is stabilized by fluorine and non-fluorine hydrogen bonds, thereby explaining the superlative stability of araF-C modified i-motifs. Comparative experimental findings suggest that the strength of these interactions depends on the flexible sugar pucker adopted by the araF-C residue. Overall, the findings reported here provide a new role for i-motifs in nanotechnology and also pose the question of whether unprecedented i-motif folds may exist in vivo.
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6
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Serrano-Chacón I, Mir B, Cupellini L, Colizzi F, Orozco M, Escaja N, González C. pH-Dependent Capping Interactions Induce Large-Scale Structural Transitions in i-Motifs. J Am Chem Soc 2023; 145:3696-3705. [PMID: 36745195 PMCID: PMC9936585 DOI: 10.1021/jacs.2c13043] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Indexed: 02/07/2023]
Abstract
We study here a DNA oligonucleotide having the ability to form two different i-motif structures whose relative stability depends on pH and temperature. The major species at neutral pH is stabilized by two C:C+ base pairs capped by two minor groove G:C:G:C tetrads. The high pH and thermal stability of this structure are mainly due to the favorable effect of the minor groove tetrads on their adjacent positively charged C:C+ base pairs. At pH 5, we observe a more elongated i-motif structure consisting of four C:C+ base pairs capped by two G:T:G:T tetrads. Molecular dynamics calculations show that the conformational transition between the two structures is driven by the protonation state of key cytosines. In spite of large conformational differences, the transition between the acidic and neutral structures can occur without unfolding of the i-motif. These results represent the first case of a conformational switch between two different i-motif structures and illustrate the dramatic pH-dependent plasticity of this fascinating DNA motif.
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Affiliation(s)
- Israel Serrano-Chacón
- Instituto
de Química Física ”Rocasolano”, CSIC, Serrano 119, 28006Madrid, Spain
- Institute
for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology (BIST), 08028Barcelona, Spain
| | - Bartomeu Mir
- Instituto
de Química Física ”Rocasolano”, CSIC, Serrano 119, 28006Madrid, Spain
- Inorganic
and Organic Chemistry Department, Organic Chemistry Section, and IBUB, University of Barcelona, Martí i Franquès 1-11, 08028Barcelona, Spain
| | - Lorenzo Cupellini
- Institute
for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology (BIST), 08028Barcelona, Spain
| | - Francesco Colizzi
- Institute
for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology (BIST), 08028Barcelona, Spain
| | - Modesto Orozco
- Institute
for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology (BIST), 08028Barcelona, Spain
- Departament
de Bioquímica i Biomedicina. Facultat de Biologia, Universitat de Barcelona, 08028Barcelona, Spain
| | - Núria Escaja
- Inorganic
and Organic Chemistry Department, Organic Chemistry Section, and IBUB, University of Barcelona, Martí i Franquès 1-11, 08028Barcelona, Spain
- BIOESTRAN
Associated Unit UB-CSIC, 08028Barcelona, Spain
| | - Carlos González
- Instituto
de Química Física ”Rocasolano”, CSIC, Serrano 119, 28006Madrid, Spain
- BIOESTRAN
Associated Unit UB-CSIC, 08028Barcelona, Spain
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7
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Amato J, Iaccarino N, D'Aria F, D'Amico F, Randazzo A, Giancola C, Cesàro A, Di Fonzo S, Pagano B. Conformational plasticity of DNA secondary structures: probing the conversion between i-motif and hairpin species by circular dichroism and ultraviolet resonance Raman spectroscopies. Phys Chem Chem Phys 2022; 24:7028-7044. [PMID: 35258065 DOI: 10.1039/d2cp00058j] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The promoter regions of important oncogenes such as BCL2 and KRAS contain GC-rich sequences that can form distinctive noncanonical DNA structures involved in the regulation of transcription: G-quadruplexes on the G-rich strand and i-motifs on the C-rich strand. Interestingly, BCL2 and KRAS promoter i-motifs are highly dynamic in nature and exist in a pH-dependent equilibrium with hairpin and even with hybrid i-motif/hairpin species. Herein, the effects of pH and presence of cell-mimicking molecular crowding conditions on conformational equilibria of the BCL2 and KRAS i-motif-forming sequences were investigated by ultraviolet resonance Raman (UVRR) and circular dichroism (CD) spectroscopies. Multivariate analysis of CD data was essential to model the presence and identity of the species involved. Analysis of UVRR spectra measured as a function of pH, performed also by the two-dimensional correlation spectroscopy (2D-COS) technique, showed the role of several functional groups in the DNA conformational transitions, and provided structural and dynamic information. Thus, the UVRR investigation of intramolecular interactions and of local and environmental dynamics in promoting the different species induced by the solution conditions provided valuable insights into i-motif conformational transitions. The combined use of the two spectroscopic tools is emphasized by the relevant possibility of working in the same DNA concentration range and by the heterospectral UVRR/CD 2D-COS analysis. The results of this study shed light on the factors that can influence at the molecular level the equilibrium between the different conformational species putatively involved in the oncogene expression.
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Affiliation(s)
- Jussara Amato
- Department of Pharmacy, University of Naples Federico II, Naples, I-80131, Italy.
| | - Nunzia Iaccarino
- Department of Pharmacy, University of Naples Federico II, Naples, I-80131, Italy.
| | - Federica D'Aria
- Department of Pharmacy, University of Naples Federico II, Naples, I-80131, Italy.
| | - Francesco D'Amico
- Elettra-Sincrotrone Trieste S. C. p. A., Science Park, Trieste, I-34149, Italy.
| | - Antonio Randazzo
- Department of Pharmacy, University of Naples Federico II, Naples, I-80131, Italy.
| | - Concetta Giancola
- Department of Pharmacy, University of Naples Federico II, Naples, I-80131, Italy.
| | - Attilio Cesàro
- Elettra-Sincrotrone Trieste S. C. p. A., Science Park, Trieste, I-34149, Italy.
| | - Silvia Di Fonzo
- Elettra-Sincrotrone Trieste S. C. p. A., Science Park, Trieste, I-34149, Italy.
| | - Bruno Pagano
- Department of Pharmacy, University of Naples Federico II, Naples, I-80131, Italy.
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8
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Largy E, König A, Ghosh A, Ghosh D, Benabou S, Rosu F, Gabelica V. Mass Spectrometry of Nucleic Acid Noncovalent Complexes. Chem Rev 2021; 122:7720-7839. [PMID: 34587741 DOI: 10.1021/acs.chemrev.1c00386] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Nucleic acids have been among the first targets for antitumor drugs and antibiotics. With the unveiling of new biological roles in regulation of gene expression, specific DNA and RNA structures have become very attractive targets, especially when the corresponding proteins are undruggable. Biophysical assays to assess target structure as well as ligand binding stoichiometry, affinity, specificity, and binding modes are part of the drug development process. Mass spectrometry offers unique advantages as a biophysical method owing to its ability to distinguish each stoichiometry present in a mixture. In addition, advanced mass spectrometry approaches (reactive probing, fragmentation techniques, ion mobility spectrometry, ion spectroscopy) provide more detailed information on the complexes. Here, we review the fundamentals of mass spectrometry and all its particularities when studying noncovalent nucleic acid structures, and then review what has been learned thanks to mass spectrometry on nucleic acid structures, self-assemblies (e.g., duplexes or G-quadruplexes), and their complexes with ligands.
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Affiliation(s)
- Eric Largy
- Univ. Bordeaux, CNRS, INSERM, ARNA, UMR 5320, U1212, IECB, F-33600 Pessac, France
| | - Alexander König
- Univ. Bordeaux, CNRS, INSERM, ARNA, UMR 5320, U1212, IECB, F-33600 Pessac, France
| | - Anirban Ghosh
- Univ. Bordeaux, CNRS, INSERM, ARNA, UMR 5320, U1212, IECB, F-33600 Pessac, France
| | - Debasmita Ghosh
- Univ. Bordeaux, CNRS, INSERM, ARNA, UMR 5320, U1212, IECB, F-33600 Pessac, France
| | - Sanae Benabou
- Univ. Bordeaux, CNRS, INSERM, ARNA, UMR 5320, U1212, IECB, F-33600 Pessac, France
| | - Frédéric Rosu
- Univ. Bordeaux, CNRS, INSERM, IECB, UMS 3033, F-33600 Pessac, France
| | - Valérie Gabelica
- Univ. Bordeaux, CNRS, INSERM, ARNA, UMR 5320, U1212, IECB, F-33600 Pessac, France
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9
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Obtaining Precise Molecular Information via DNA Nanotechnology. MEMBRANES 2021; 11:membranes11090683. [PMID: 34564500 PMCID: PMC8466356 DOI: 10.3390/membranes11090683] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Revised: 08/28/2021] [Accepted: 08/30/2021] [Indexed: 11/17/2022]
Abstract
Precise characterization of biomolecular information such as molecular structures or intermolecular interactions provides essential mechanistic insights into the understanding of biochemical processes. As the resolution of imaging-based measurement techniques improves, so does the quantity of molecular information obtained using these methodologies. DNA (deoxyribonucleic acid) molecule have been used to build a variety of structures and dynamic devices on the nanoscale over the past 20 years, which has provided an accessible platform to manipulate molecules and resolve molecular information with unprecedented precision. In this review, we summarize recent progress related to obtaining precise molecular information using DNA nanotechnology. After a brief introduction to the development and features of structural and dynamic DNA nanotechnology, we outline some of the promising applications of DNA nanotechnology in structural biochemistry and in molecular biophysics. In particular, we highlight the use of DNA nanotechnology in determination of protein structures, protein-protein interactions, and molecular force.
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10
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Xi D, Cui M, Zhou X, Zhuge X, Ge Y, Wang Y, Zhang S. Nanopore-Based Single-Molecule Investigation of DNA Sequences with Potential to Form i-Motif Structures. ACS Sens 2021; 6:2691-2699. [PMID: 34237940 DOI: 10.1021/acssensors.1c00712] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
i-Motifs are DNA secondary structures present in cytosine-rich sequences. These structures are formed in regulatory regions of the human genome and play key regulatory roles. The investigation of sequences capable of forming i-motif structures at the single-molecule level is highly important. In this study, we used α-hemolysin nanopores to systematically study a series of DNA sequences at the nanometer scale by providing structure-dependent signature current signals to gain in-sights into the i-motif DNA sequence and structural stability. Increasing the length of the cytosine tract in a range of 3-10 nucleobases resulted in a longer translocation time through the pore, indicating improved stability. Changing the loop sequence and length in the sequences did not affect the formation of the i-motif structure but changed its stability. Importantly, the application of all-atom molecular dynamics simulations revealed the structural morphology of all sequences. Based on these results, we postulated a folding rule for i-motif formation, suggesting that thousands of cytosine-rich sequences in the human genome might fold into i-motif structures. Many of these were found in locations where structure formation is likely to play regulatory roles. These findings provide insights into the application of nanopores as a powerful tool for discovering potential i-motif-forming sequences and lay a foundation for future studies exploring the biological roles of i-motifs.
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Affiliation(s)
- Dongmei Xi
- Shandong Provincial Key Laboratory of Detection Technology for Tumor Markers, College of Life Sciences, Linyi University, Linyi 276005, P. R. China
| | - Mengjie Cui
- Shandong Provincial Key Laboratory of Detection Technology for Tumor Markers, College of Chemistry and Chemical Engineering, Linyi University, Linyi 276005, P. R. China
| | - Xin Zhou
- Shandong Provincial Key Laboratory of Detection Technology for Tumor Markers, College of Chemistry and Chemical Engineering, Linyi University, Linyi 276005, P. R. China
| | - Xiao Zhuge
- Shandong Provincial Key Laboratory of Detection Technology for Tumor Markers, College of Chemistry and Chemical Engineering, Linyi University, Linyi 276005, P. R. China
| | - Yaxian Ge
- Shandong Provincial Key Laboratory of Detection Technology for Tumor Markers, College of Chemistry and Chemical Engineering, Linyi University, Linyi 276005, P. R. China
| | - Ying Wang
- Shandong Provincial Key Laboratory of Detection Technology for Tumor Markers, College of Life Sciences, Linyi University, Linyi 276005, P. R. China
| | - Shusheng Zhang
- Shandong Provincial Key Laboratory of Detection Technology for Tumor Markers, College of Chemistry and Chemical Engineering, Linyi University, Linyi 276005, P. R. China
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11
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Cheng M, Chen J, Ju H, Zhou J, Mergny JL. Drivers of i-DNA Formation in a Variety of Environments Revealed by Four-Dimensional UV Melting and Annealing. J Am Chem Soc 2021; 143:7792-7807. [PMID: 33988990 DOI: 10.1021/jacs.1c02209] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
i-DNA is a four-stranded, pH-sensitive structure formed by cytosine-rich DNA sequences. Previous reports have addressed the conditions for formation of this motif in DNA in vitro and validated its existence in human cells. Unfortunately, these in vitro studies have often been performed under different experimental conditions, making comparisons difficult. To overcome this, we developed a four-dimensional UV melting and annealing (4DUVMA) approach to analyze i-DNA formation under a variety of conditions (e.g., pH, temperature, salt, crowding). Analysis of 25 sequences provided a global understanding of i-DNA formation under disparate conditions, which should ultimately allow the design of accurate prediction tools. For example, we found reliable linear correlations between the midpoint of pH transition and temperature (-0.04 ± 0.003 pH unit per 1.0 °C temperature increment) and between the melting temperature and pH (-23.8 ± 1.1 °C per pH unit increment). In addition, by analyzing the hysteresis between denaturing and renaturing profiles in both pH and thermal transitions, we found that loop length, nature of the C-tracts, pH, temperature, and crowding agents all play roles in i-DNA folding kinetics. Interestingly, our data indicate which conformer is more favorable for the sequences with an odd number of cytosine base pairs. Then the thermal and pH stabilities of "native" i-DNAs from human promoter genes were measured under near physiological conditions (pH 7.0, 37 °C). The 4DUVMA method can become a universal resource to analyze the properties of any i-DNA-prone sequence.
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Affiliation(s)
- Mingpan Cheng
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry & Chemical Engineering, Nanjing University, Nanjing 210023, China.,ARNA Laboratory, Université de Bordeaux, INSERM U1212, CNRS UMR5320, IECB, Pessac 33607, France
| | - Jielin Chen
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry & Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Huangxian Ju
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry & Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Jun Zhou
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry & Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Jean-Louis Mergny
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry & Chemical Engineering, Nanjing University, Nanjing 210023, China.,ARNA Laboratory, Université de Bordeaux, INSERM U1212, CNRS UMR5320, IECB, Pessac 33607, France.,Laboratoire d'Optique et Biosciences, Ecole Polytechnique, CNRS, INSERM, Institut Polytechnique de Paris, Palaiseau Cedex 91128, France
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12
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Cheng M, Qiu D, Tamon L, Ištvánková E, Víšková P, Amrane S, Guédin A, Chen J, Lacroix L, Ju H, Trantírek L, Sahakyan AB, Zhou J, Mergny J. Thermal and pH Stabilities of i‐DNA: Confronting in vitro Experiments with Models and In‐Cell NMR Data. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202016801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Mingpan Cheng
- State Key Laboratory of Analytical Chemistry for Life Science School of Chemistry & Chemical Engineering Nanjing University Nanjing 210023 China
- ARNA Laboratory Université de Bordeaux, INSERM U 1212, CNRS UMR5320 IECB 33607 Pessac France
| | - Dehui Qiu
- State Key Laboratory of Analytical Chemistry for Life Science School of Chemistry & Chemical Engineering Nanjing University Nanjing 210023 China
| | - Liezel Tamon
- MRC WIMM Centre for Computational Biology MRC Weatherall Institute of Molecular Medicine Radcliffe Department of Medicine University of Oxford Oxford OX3 9DS UK
| | - Eva Ištvánková
- Central European Institute of Technology Masaryk University 62500 Brno Czech Republic
| | - Pavlína Víšková
- Central European Institute of Technology Masaryk University 62500 Brno Czech Republic
| | - Samir Amrane
- ARNA Laboratory Université de Bordeaux, INSERM U 1212, CNRS UMR5320 IECB 33607 Pessac France
| | - Aurore Guédin
- ARNA Laboratory Université de Bordeaux, INSERM U 1212, CNRS UMR5320 IECB 33607 Pessac France
| | - Jielin Chen
- State Key Laboratory of Analytical Chemistry for Life Science School of Chemistry & Chemical Engineering Nanjing University Nanjing 210023 China
| | - Laurent Lacroix
- IBENS Ecole Normale Supérieure CNRS INSERM PSL Research University 75005 Paris France
| | - Huangxian Ju
- State Key Laboratory of Analytical Chemistry for Life Science School of Chemistry & Chemical Engineering Nanjing University Nanjing 210023 China
| | - Lukáš Trantírek
- Central European Institute of Technology Masaryk University 62500 Brno Czech Republic
| | - Aleksandr B. Sahakyan
- MRC WIMM Centre for Computational Biology MRC Weatherall Institute of Molecular Medicine Radcliffe Department of Medicine University of Oxford Oxford OX3 9DS UK
| | - Jun Zhou
- State Key Laboratory of Analytical Chemistry for Life Science School of Chemistry & Chemical Engineering Nanjing University Nanjing 210023 China
| | - Jean‐Louis Mergny
- State Key Laboratory of Analytical Chemistry for Life Science School of Chemistry & Chemical Engineering Nanjing University Nanjing 210023 China
- ARNA Laboratory Université de Bordeaux, INSERM U 1212, CNRS UMR5320 IECB 33607 Pessac France
- Laboratoire d'Optique et Biosciences Ecole Polytechnique CNRS INSERM Institut Polytechnique de Paris 91128 Palaiseau France
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13
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Cheng M, Qiu D, Tamon L, Ištvánková E, Víšková P, Amrane S, Guédin A, Chen J, Lacroix L, Ju H, Trantírek L, Sahakyan AB, Zhou J, Mergny JL. Thermal and pH Stabilities of i-DNA: Confronting in vitro Experiments with Models and In-Cell NMR Data. Angew Chem Int Ed Engl 2021; 60:10286-10294. [PMID: 33605024 DOI: 10.1002/anie.202016801] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Indexed: 12/22/2022]
Abstract
Recent studies indicate that i-DNA, a four-stranded cytosine-rich DNA also known as the i-motif, is actually formed in vivo; however, a systematic study on sequence effects on stability has been missing. Herein, an unprecedented number of different sequences (271) bearing four runs of 3-6 cytosines with different spacer lengths has been tested. While i-DNA stability is nearly independent on total spacer length, the central spacer plays a special role on stability. Stability also depends on the length of the C-tracts at both acidic and neutral pHs. This study provides a global picture on i-DNA stability thanks to the large size of the introduced data set; it reveals unexpected features and allows to conclude that determinants of i-DNA stability do not mirror those of G-quadruplexes. Our results illustrate the structural roles of loops and C-tracts on i-DNA stability, confirm its formation in cells, and allow establishing rules to predict its stability.
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Affiliation(s)
- Mingpan Cheng
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry & Chemical Engineering, Nanjing University, Nanjing, 210023, China.,ARNA Laboratory, Université de Bordeaux, INSERM U 1212, CNRS UMR5320, IECB, 33607, Pessac, France
| | - Dehui Qiu
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry & Chemical Engineering, Nanjing University, Nanjing, 210023, China
| | - Liezel Tamon
- MRC WIMM Centre for Computational Biology, MRC Weatherall Institute of Molecular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford, OX3 9DS, UK
| | - Eva Ištvánková
- Central European Institute of Technology, Masaryk University, 62500, Brno, Czech Republic
| | - Pavlína Víšková
- Central European Institute of Technology, Masaryk University, 62500, Brno, Czech Republic
| | - Samir Amrane
- ARNA Laboratory, Université de Bordeaux, INSERM U 1212, CNRS UMR5320, IECB, 33607, Pessac, France
| | - Aurore Guédin
- ARNA Laboratory, Université de Bordeaux, INSERM U 1212, CNRS UMR5320, IECB, 33607, Pessac, France
| | - Jielin Chen
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry & Chemical Engineering, Nanjing University, Nanjing, 210023, China
| | - Laurent Lacroix
- IBENS, Ecole Normale Supérieure, CNRS, INSERM, PSL Research University, 75005, Paris, France
| | - Huangxian Ju
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry & Chemical Engineering, Nanjing University, Nanjing, 210023, China
| | - Lukáš Trantírek
- Central European Institute of Technology, Masaryk University, 62500, Brno, Czech Republic
| | - Aleksandr B Sahakyan
- MRC WIMM Centre for Computational Biology, MRC Weatherall Institute of Molecular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford, OX3 9DS, UK
| | - Jun Zhou
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry & Chemical Engineering, Nanjing University, Nanjing, 210023, China
| | - Jean-Louis Mergny
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry & Chemical Engineering, Nanjing University, Nanjing, 210023, China.,ARNA Laboratory, Université de Bordeaux, INSERM U 1212, CNRS UMR5320, IECB, 33607, Pessac, France.,Laboratoire d'Optique et Biosciences, Ecole Polytechnique, CNRS, INSERM, Institut Polytechnique de Paris, 91128, Palaiseau, France
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14
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Gargallo R, Aviñó A, Eritja R, Jarosova P, Mazzini S, Scaglioni L, Taborsky P. Study of alkaloid berberine and its interaction with the human telomeric i-motif DNA structure. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2021; 248:119185. [PMID: 33234477 DOI: 10.1016/j.saa.2020.119185] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Revised: 10/30/2020] [Accepted: 11/01/2020] [Indexed: 06/11/2023]
Abstract
The alkaloid berberine presents many biological activities related to its potential to bind DNA structures, such as duplex or G-quadruplex. Recently, it has been proposed that berberine may interact with i-motif structures formed from the folding of cytosine-rich sequences. In the present work, the interaction of this alkaloid with the i-motif formed by the human telomere cytosine-rich sequence, as well as with several positive and negative controls, has been studied. Molecular fluorescence and circular dichroism spectroscopies, as well as nuclear magnetic resonance spectrometry and competitive dialysis, have been used with this purpose. The results shown here reveal that the interaction of berberine with this i-motif is weak, mostly electrostatics in nature and takes place with bases not involved in C·C+ base pairs. Moreover, this ligand is not selective for i-motif structures, as binds equally to both, folded structure, and unfolded strand, without producing any stabilization of the i-motif. As a conclusion, the development of analytical methods based on the interaction of fluorescent ligands, such as berberine, with i-motif structures should consider the thermodynamic aspects related with the interaction, as well as the selectivity of the proposed ligands with different DNA structures, including unfolded strands.
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Affiliation(s)
- R Gargallo
- Dept. of Chemical Engineering and Analytical Chemistry, University of Barcelona, Marti i Franquès 1, E-08028 Barcelona, Spain.
| | - A Aviñó
- Institute for Advanced Chemistry of Catalonia (IQAC-CSIC), CIBER-BBN, Jordi Girona 18-26, E-08034 Barcelona, Spain
| | - R Eritja
- Institute for Advanced Chemistry of Catalonia (IQAC-CSIC), CIBER-BBN, Jordi Girona 18-26, E-08034 Barcelona, Spain
| | - P Jarosova
- Department of Chemistry, Faculty of Science, Masaryk University, Kamenice 5, 62500 Brno, Czech Republic
| | - S Mazzini
- Department of Food, Environmental and Nutritional Sciences (DEFENS), Section of Chemical and Biomolecular Sciences, University of Milan, Via Celoria 2, 20133 Milan, Italy
| | - L Scaglioni
- Department of Food, Environmental and Nutritional Sciences (DEFENS), Section of Chemical and Biomolecular Sciences, University of Milan, Via Celoria 2, 20133 Milan, Italy
| | - P Taborsky
- Department of Chemistry, Faculty of Science, Masaryk University, Kamenice 5, 62500 Brno, Czech Republic.
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15
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Lobato R. A quantum mechanical approach to random X chromosome inactivation. AIMS BIOPHYSICS 2021. [DOI: 10.3934/biophy.2021026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
<abstract>
<p>The X chromosome inactivation is an essential mechanism in mammals' development, that despite having been investigated for 60 years, many questions about its choice process have yet to be fully answered. Therefore, a theoretical model was proposed here for the first time in an attempt to explain this puzzling phenomenon through a quantum mechanical approach. Based on previous data, this work theoretically demonstrates how a shared delocalized proton at a key base pair position could explain the random, instantaneous, and mutually exclusive nature of the choice process in X chromosome inactivation. The main purpose of this work is to contribute to a comprehensive understanding of the X inactivation mechanism with a model proposal that can complement the existent ones, along with introducing a quantum mechanical approach that could be applied to other cell differentiation mechanisms.</p>
</abstract>
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16
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Chalikian TV, Liu L, Macgregor RB. Duplex-tetraplex equilibria in guanine- and cytosine-rich DNA. Biophys Chem 2020; 267:106473. [PMID: 33031980 DOI: 10.1016/j.bpc.2020.106473] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Accepted: 09/03/2020] [Indexed: 02/07/2023]
Abstract
Noncanonical four-stranded DNA structures, including G-quadruplexes and i-motifs, have been discovered in the cell and are implicated in a variety of genomic regulatory functions. The tendency of a specific guanine- and cytosine-rich region of genomic DNA to adopt a four-stranded conformation depends on its ability to overcome the constraints of duplex base-pairing by undergoing consecutive duplex-to-coil and coil-to-tetraplex transitions. The latter ability is determined by the balance between the free energies of participating ordered and disordered structures. In this review, we present an overview of the literature on the stability of G-quadruplex and i-motif structures and discuss the extent of duplex-tetraplex competition as a function of the sequence context of the DNA and environmental conditions including temperature, pH, salt, molecular crowding, and the presence of G-quadruplex-binding ligands. We outline how the results of in vitro studies can be expanded to understanding duplex-tetraplex equilibria in vivo.
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Affiliation(s)
- Tigran V Chalikian
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, 144 College Street, Toronto, Ontario M5S 3M2, Canada.
| | - Lutan Liu
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, 144 College Street, Toronto, Ontario M5S 3M2, Canada
| | - Robert B Macgregor
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, 144 College Street, Toronto, Ontario M5S 3M2, Canada
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17
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Školáková P, Badri Z, Foldynová-Trantírková S, Ryneš J, Šponer J, Fojtová M, Fajkus J, Marek R, Vorlíčková M, Mergny JL, Trantírek L. Composite 5-methylations of cytosines modulate i-motif stability in a sequence-specific manner: Implications for DNA nanotechnology and epigenetic regulation of plant telomeric DNA. Biochim Biophys Acta Gen Subj 2020; 1864:129651. [DOI: 10.1016/j.bbagen.2020.129651] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 05/23/2020] [Accepted: 05/28/2020] [Indexed: 12/14/2022]
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18
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Rogers RA, Meyer MR, Stewart KM, Eyring GM, Fleming AM, Burrows CJ. Hysteresis in poly-2'-deoxycytidine i-motif folding is impacted by the method of analysis as well as loop and stem lengths. Biopolymers 2020; 112:e23389. [PMID: 33098582 DOI: 10.1002/bip.23389] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Revised: 06/06/2020] [Accepted: 06/11/2020] [Indexed: 02/06/2023]
Abstract
In DNA, i-motif (iM) folds occur under slightly acidic conditions when sequences rich in 2'-deoxycytidine (dC) nucleotides adopt consecutive dC self base pairs. The pH stability of an iM is defined by the midpoint in the pH transition (pHT ) between the folded and unfolded states. Two different experiments to determine pHT values via circular dichroism (CD) spectroscopy were performed on poly-dC iMs of length 15, 19, or 23 nucleotides. These experiments demonstrate two points: (1) pHT values were dependent on the titration experiment performed, and (2) pH-induced denaturing or annealing processes produced isothermal hysteresis in the pHT values. These results in tandem with model iMs with judicious mutations of dC to thymidine to favor particular folds found the hysteresis was maximal for the shorter poly-dC iMs and those with an even number of base pairs, while the hysteresis was minimal for longer poly-dC iMs and those with an odd number of base pairs. Experiments to follow the iM folding via thermal changes identified thermal hysteresis between the denaturing and annealing cycles. Similar trends were found to those observed in the CD experiments. The results demonstrate that the method of iM analysis can impact the pHT parameter measured, and hysteresis was observed in the pHT and Tm values.
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Affiliation(s)
- R Aaron Rogers
- Department of Chemistry, University of Utah, Salt Lake City, Utah, U.S.A
| | - Madeline R Meyer
- Department of Chemistry, University of Utah, Salt Lake City, Utah, U.S.A
| | - Kayla M Stewart
- Department of Chemistry, University of Utah, Salt Lake City, Utah, U.S.A
| | - Gabriela M Eyring
- Department of Chemistry, University of Utah, Salt Lake City, Utah, U.S.A
| | - Aaron M Fleming
- Department of Chemistry, University of Utah, Salt Lake City, Utah, U.S.A
| | - Cynthia J Burrows
- Department of Chemistry, University of Utah, Salt Lake City, Utah, U.S.A
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19
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Abdelhamid MAS, Waller ZAE. Tricky Topology: Persistence of Folded Human Telomeric i-Motif DNA at Ambient Temperature and Neutral pH. Front Chem 2020; 8:40. [PMID: 32083057 PMCID: PMC7005205 DOI: 10.3389/fchem.2020.00040] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Accepted: 01/14/2020] [Indexed: 12/30/2022] Open
Abstract
i-Motifs are four-stranded DNA structures formed from sequences rich in cytosine, held together by hemi-protonated cytosine-cytosine base pairs. These structures have been utilized extensively as pH-switches in DNA-based nanotechnology. Recently there has been an increasing interest in i-motif structures in biology, fuelled by examples of when these can form under neutral conditions. Herein we describe a cautionary tale regarding handling of i-motif samples. Using CD and UV spectroscopy we show that it is important to be consistent in annealing i-motif DNA samples as at neutral pH, i-motif unfolding kinetics is dependent on the time allowed for annealing and equilibration. We describe how the quadruplex structure formed by the human telomeric i-motif sequence can be shown to form and persist in the same conditions of neutral pH and ambient temperature in which, once at thermodynamic equilibrium, it exists predominantly as a random coil. This study has implications not only for work with i-motif DNA structures, but also in the uses and applications of these in nanotechnological devices.
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Affiliation(s)
- Mahmoud A S Abdelhamid
- School of Pharmacy, University of East Anglia, Norwich Research Park, Norwich, United Kingdom.,Centre for Molecular and Structural Biochemistry, University of East Anglia, Norwich Research Park, Norwich, United Kingdom
| | - Zoë A E Waller
- School of Pharmacy, University of East Anglia, Norwich Research Park, Norwich, United Kingdom.,Centre for Molecular and Structural Biochemistry, University of East Anglia, Norwich Research Park, Norwich, United Kingdom
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20
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Školáková P, Renčiuk D, Palacký J, Krafčík D, Dvořáková Z, Kejnovská I, Bednářová K, Vorlíčková M. Systematic investigation of sequence requirements for DNA i-motif formation. Nucleic Acids Res 2019; 47:2177-2189. [PMID: 30715498 PMCID: PMC6412112 DOI: 10.1093/nar/gkz046] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Revised: 01/16/2019] [Accepted: 01/18/2019] [Indexed: 12/13/2022] Open
Abstract
The formation of intercalated motifs (iMs) - secondary DNA structures based on hemiprotonated C.C+ pairs in suitable cytosine-rich DNA sequences, is reflected by typical changes in CD and UV absorption spectra. By means of spectroscopic methods, electrophoresis, chemical modifications and other procedures, we characterized iM formation and stability in sequences with different cytosine block lengths interrupted by various numbers and types of nucleotides. Particular attention was paid to the formation of iMs at pH conditions close to neutral. We identified the optimal conditions and minimal requirements for iM formation in DNA sequences, and addressed gaps and inaccurate data interpretations in existing studies to specify principles of iM formation and modes of their folding.
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Affiliation(s)
- Petra Školáková
- Institute of Biophysics of the Czech Academy of Sciences, v.v.i., Královopolská 135, 612 65 Brno, Czech Republic
| | - Daniel Renčiuk
- Institute of Biophysics of the Czech Academy of Sciences, v.v.i., Královopolská 135, 612 65 Brno, Czech Republic
| | - Jan Palacký
- Institute of Biophysics of the Czech Academy of Sciences, v.v.i., Královopolská 135, 612 65 Brno, Czech Republic
| | - Daniel Krafčík
- CEITEC-Central European Institute of Technology, Masaryk University, Kamenice 735/5, 625 00 Brno, Czech Republic
| | - Zuzana Dvořáková
- Institute of Biophysics of the Czech Academy of Sciences, v.v.i., Královopolská 135, 612 65 Brno, Czech Republic
| | - Iva Kejnovská
- Institute of Biophysics of the Czech Academy of Sciences, v.v.i., Královopolská 135, 612 65 Brno, Czech Republic
| | - Klára Bednářová
- Institute of Biophysics of the Czech Academy of Sciences, v.v.i., Královopolská 135, 612 65 Brno, Czech Republic
| | - Michaela Vorlíčková
- Institute of Biophysics of the Czech Academy of Sciences, v.v.i., Královopolská 135, 612 65 Brno, Czech Republic
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21
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Dvoráková Z, Renciuk D, Kejnovská I, Školáková P, Bednárová K, Sagi J, Vorlícková M. i-Motif of cytosine-rich human telomere DNA fragments containing natural base lesions. Nucleic Acids Res 2019; 46:1624-1634. [PMID: 29378012 PMCID: PMC5829569 DOI: 10.1093/nar/gky035] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Accepted: 01/15/2018] [Indexed: 12/01/2022] Open
Abstract
i-Motif (iM) is a four stranded DNA structure formed by cytosine-rich sequences, which are often present in functionally important parts of the genome such as promoters of genes and telomeres. Using electronic circular dichroism and UV absorption spectroscopies and electrophoretic methods, we examined the effect of four naturally occurring DNA base lesions on the folding and stability of the iM formed by the human telomere DNA sequence (C3TAA)3C3T. The results demonstrate that the TAA loop lesions, the apurinic site and 8-oxoadenine substituting for adenine, and the 5-hydroxymethyluracil substituting for thymine only marginally disturb the formation of iM. The presence of uracil, which is formed by enzymatic or spontaneous deamination of cytosine, shifts iM formation towards substantially more acidic pH values and simultaneously distinctly reduces iM stability. This effect depends on the position of the damage sites in the sequence. The results have enabled us to formulate additional rules for iM formation.
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Affiliation(s)
- Zuzana Dvoráková
- Institute of Biophysics of the Czech Academy of Sciences, Královopolská 135, 612 65 Brno, Czech Republic
| | - Daniel Renciuk
- Institute of Biophysics of the Czech Academy of Sciences, Královopolská 135, 612 65 Brno, Czech Republic
| | - Iva Kejnovská
- Institute of Biophysics of the Czech Academy of Sciences, Královopolská 135, 612 65 Brno, Czech Republic
| | - Petra Školáková
- Institute of Biophysics of the Czech Academy of Sciences, Královopolská 135, 612 65 Brno, Czech Republic
| | - Klára Bednárová
- Institute of Biophysics of the Czech Academy of Sciences, Královopolská 135, 612 65 Brno, Czech Republic
| | - Janos Sagi
- Rimstone Laboratory, RLI, Carlsbad, CA 92010, USA
| | - Michaela Vorlícková
- Institute of Biophysics of the Czech Academy of Sciences, Královopolská 135, 612 65 Brno, Czech Republic
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22
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Abou Assi H, Garavís M, González C, Damha MJ. i-Motif DNA: structural features and significance to cell biology. Nucleic Acids Res 2019; 46:8038-8056. [PMID: 30124962 PMCID: PMC6144788 DOI: 10.1093/nar/gky735] [Citation(s) in RCA: 236] [Impact Index Per Article: 47.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Accepted: 08/13/2018] [Indexed: 12/20/2022] Open
Abstract
The i-motif represents a paradigmatic example of the wide structural versatility of nucleic acids. In remarkable contrast to duplex DNA, i-motifs are four-stranded DNA structures held together by hemi- protonated and intercalated cytosine base pairs (C:C+). First observed 25 years ago, and considered by many as a mere structural oddity, interest in and discussion on the biological role of i-motifs have grown dramatically in recent years. In this review we focus on structural aspects of i-motif formation, the factors leading to its stabilization and recent studies describing the possible role of i-motifs in fundamental biological processes.
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Affiliation(s)
- Hala Abou Assi
- Department of Chemistry, McGill University, Montreal, QC H3A 0B8, Canada
| | - Miguel Garavís
- Instituto de Química Física 'Rocasolano', CSIC, C/Serrano 119, 28006 Madrid, Spain
| | - Carlos González
- Instituto de Química Física 'Rocasolano', CSIC, C/Serrano 119, 28006 Madrid, Spain
| | - Masad J Damha
- Department of Chemistry, McGill University, Montreal, QC H3A 0B8, Canada
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23
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Rogers RA, Fleming AM, Burrows CJ. Unusual Isothermal Hysteresis in DNA i-Motif pH Transitions: A Study of the RAD17 Promoter Sequence. Biophys J 2019; 114:1804-1815. [PMID: 29694860 DOI: 10.1016/j.bpj.2018.03.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Revised: 03/07/2018] [Accepted: 03/14/2018] [Indexed: 11/15/2022] Open
Abstract
We have interrogated the isothermal folding behavior of the DNA i-motif of the human telomere, dC19, and a high-stability i-motif-forming sequence in the promoter of the human DNA repair gene RAD17 using human physiological solution and temperature conditions. We developed a circular-dichroism-spectroscopy-based pH titration method that is followed by analysis of titration curves in the derivative domain and found that the observed pH-dependent folding behavior can be significantly different and, in some cases, multiphasic, with a dependence on how rapidly i-motif folding is induced. Interestingly, the human telomere sequence exhibits unusual isothermal hysteresis in which the unfolding process always occurs at a higher pH than the folding process. For the RAD17 i-motif, rapid folding by injection into a low-pH solution results in triphasic unfolding behavior that is completely diminished when samples are slowly folded in a stepwise manner via pH titration. Chemical footprinting of the RAD17 sequence and pH titrations of dT-substituted mutants of the RAD17 sequence were used to develop a model of RAD17 folding and unfolding. These results may provide valuable information pertinent to i-motif use in sensors and materials, as well as insight into the potential biological activity of i-motif-forming sequences under stepwise or instantaneous changes in pH.
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Affiliation(s)
- R Aaron Rogers
- Department of Chemistry, University of Utah, Salt Lake City, Utah
| | - Aaron M Fleming
- Department of Chemistry, University of Utah, Salt Lake City, Utah
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24
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Fleming AM, Stewart KM, Eyring GM, Ball TE, Burrows CJ. Unraveling the 4n - 1 rule for DNA i-motif stability: base pairs vs. loop lengths. Org Biomol Chem 2019; 16:4537-4546. [PMID: 29873385 DOI: 10.1039/c8ob01198b] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Previously our laboratory identified that poly-2'-deoxycytidine (dCn) strands of DNA with lengths greater than 12 nucleotides could adopt i-motif folds, while the pH-dependent stabilities follow a 4n - 1 repeat pattern with respect to chain length (J. Am. Chem. Soc., 2017, 139, 4682-4689). Herein, model i-motif folds in which loop configurations were forced by judiciously mutating dC to non-dC nucleotides allowed a structural model to be proposed to address this phenomenon. The model was developed by systematically studying two i-motifs with either an even or odd number of d(C·C)+ hemiprotonated base pairs in the core. First, a trend in the pH-dependent stability vs. loop nucleotide identity was observed: dC > dT ∼ dU ≫ dA ∼ dG. Next, loops comprised of dT nucleotides in the two different core base pair configurations were studied while systematically changing the loop lengths. We found that an i-motif with an even number of base pairs in the core with a single nucleotide in each of the three loops was the most stable, as well as an i-motif with an odd number of core base pairs having one nucleotide in the two exterior loops and three nucleotides in the central loop. A systematic increase in the central loop from 1-4 nucleotides for an odd number of base pairs in the i-motif core reproduced the 4n - 1 repeat pattern observed in the poly-dCn strands. Additional loop configurations were studied to further support the model. The results are discussed with respect to their biological relevance.
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Affiliation(s)
- Aaron M Fleming
- Department of Chemistry, 315 S. 1400 East. and University of Utah, Salt Lake City, UT 84112-0850, USA.
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25
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Ma C, Chan RCT, Chan CTL, Wong AKW, Chung BPY, Kwok WM. Fluorescence and Ultrafast Fluorescence Unveil the Formation, Folding Molecularity, and Excitation Dynamics of Homo-Oligomeric and Human Telomeric i-Motifs at Acidic and Neutral pH. Chem Asian J 2018; 13:3706-3717. [PMID: 30230251 DOI: 10.1002/asia.201801117] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Revised: 08/28/2018] [Indexed: 01/07/2023]
Abstract
i-Motifs are tetraplex DNAs known to be stable at acidic pH. The structure of i-motifs is important in DNA nanotechnology; i-motif-forming sequences with consecutive cytosine (C) molecules are abundant throughout the human genome. There is, however, little information on the structure of C-rich DNAs under physiologically relevant neutral conditions. The electron dynamics of i-motifs, crucial to both biology and materials applications, also remains largely unexplored. In this work, we report a combined femtosecond and nanosecond broadband time-resolved fluorescence (TRF) and steady-state fluorescence investigation on homo-oligomer dC20 , a human telomeric sequence (HTS) 5'-dC3 (TA2 C3 )3 , and its analogue performed with different excitation at both acidic and neutral pH. Our study provides direct observation of intrinsic fluorescence and the first full probe of the real-time dynamics of the intrinsic fluorescence from i-motifs formed from varied sequences and pH conditions. The results obtained demonstrate concrete evidence for the existence at neutral pH of i-motifs from both dC20 and the HTS. It also identifies that, under neutral conditions, the i-motif from dC20 adopting the bimolecular folding structure is significantly more stable than the HTS i-motif featuring the unimolecular topology. Our femtosecond and nanosecond TRF study unveils excitation dynamics distinctive of the interdigitated architecture of i-motifs with the excited states involved exhibiting deactivation over a remarkably broad timescale through multiple channels involving proton-coupled electron transfer lasting tens of picoseconds, as signified by the solvent kinetic isotope effect, and structure-dependent charge recombination in the hundreds of picoseconds to tens of nanoseconds time regime.
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Affiliation(s)
- Chensheng Ma
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, Guangdong, P. R. China
| | - Ruth Chau-Ting Chan
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, P. R. China
| | - Chris Tsz-Leung Chan
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen, Guangdong, P. R. China
| | - Allen Ka-Wa Wong
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, P. R. China
| | - Bowie Po-Yee Chung
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, P. R. China
| | - Wai-Ming Kwok
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, P. R. China
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26
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Liu L, Kim BG, Feroze U, Macgregor RB, Chalikian TV. Probing the Ionic Atmosphere and Hydration of the c-MYC i-Motif. J Am Chem Soc 2018; 140:2229-2238. [DOI: 10.1021/jacs.7b11537] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Lutan Liu
- Department of Pharmaceutical Sciences,
Leslie Dan Faculty of Pharmacy, University of Toronto, 144 College
Street, Toronto, Ontario M5S 3M2, Canada
| | - Byul G. Kim
- Department of Pharmaceutical Sciences,
Leslie Dan Faculty of Pharmacy, University of Toronto, 144 College
Street, Toronto, Ontario M5S 3M2, Canada
| | - Ujala Feroze
- Department of Pharmaceutical Sciences,
Leslie Dan Faculty of Pharmacy, University of Toronto, 144 College
Street, Toronto, Ontario M5S 3M2, Canada
| | - Robert B. Macgregor
- Department of Pharmaceutical Sciences,
Leslie Dan Faculty of Pharmacy, University of Toronto, 144 College
Street, Toronto, Ontario M5S 3M2, Canada
| | - Tigran V. Chalikian
- Department of Pharmaceutical Sciences,
Leslie Dan Faculty of Pharmacy, University of Toronto, 144 College
Street, Toronto, Ontario M5S 3M2, Canada
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27
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Nguyen T, Fraire C, Sheardy RD. Linking pH, Temperature, and K+ Concentration for DNA i-Motif Formation. J Phys Chem B 2017; 121:7872-7877. [DOI: 10.1021/acs.jpcb.7b06317] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Tra Nguyen
- Department of Chemistry and
Biochemistry, Texas Woman’s University, Denton, Texas 76204, United States
| | - Claudette Fraire
- Department of Chemistry and
Biochemistry, Texas Woman’s University, Denton, Texas 76204, United States
| | - Richard D. Sheardy
- Department of Chemistry and
Biochemistry, Texas Woman’s University, Denton, Texas 76204, United States
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28
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Wright EP, Huppert JL, Waller ZAE. Identification of multiple genomic DNA sequences which form i-motif structures at neutral pH. Nucleic Acids Res 2017; 45:2951-2959. [PMID: 28180276 PMCID: PMC5605235 DOI: 10.1093/nar/gkx090] [Citation(s) in RCA: 148] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Accepted: 02/06/2017] [Indexed: 01/15/2023] Open
Abstract
i-Motifs are alternative DNA secondary structures formed in cytosine-rich sequences. Particular examples of these structures, traditionally assumed to be stable only at acidic pH, have been found to form under near-physiological conditions. To determine the potential impact of these structures on physiological processes, investigation of sequences with the capacity to fold under physiological conditions is required. Here we describe a systematic study of cytosine-rich DNA sequences, with varying numbers of consecutive cytosines, to gain insights into i-motif DNA sequence and structure stability. i-Motif formation was assessed using ultraviolet spectroscopy, circular dichroism and native gel electrophoresis. We found that increasing cytosine tract lengths resulted in increased thermal stability; sequences with at least five cytosines per tract folded into i-motif at room temperature and neutral pH. Using these results, we postulated a folding rule for i-motif formation, analogous to (but different from) that for G-quadruplexes. This indicated that thousands of cytosine-rich sequences in the human genome may fold into i-motif structures under physiological conditions. Many of these were found in locations where structure formation is likely to influence gene expression. Characterization of a selection of these identified i-motif forming sequences uncovered 17 genomic i-motif forming sequence examples which were stable at neutral pH.
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Affiliation(s)
- Elisé P Wright
- School of Pharmacy, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Julian L Huppert
- Intellectual Forum, Jesus College, University of Cambridge, Cambridge CB5 8BL, UK
| | - Zoë A E Waller
- School of Pharmacy, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.,Centre for Molecular and Structural Biochemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
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29
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Fleming AM, Ding Y, Rogers RA, Zhu J, Zhu J, Burton AD, Carlisle CB, Burrows CJ. 4n-1 Is a "Sweet Spot" in DNA i-Motif Folding of 2'-Deoxycytidine Homopolymers. J Am Chem Soc 2017; 139:4682-4689. [PMID: 28290680 DOI: 10.1021/jacs.6b10117] [Citation(s) in RCA: 82] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Strands of DNA with four or more contiguous runs of 2'-deoxycytidine (dC) nucleotides have the potential to adopt i-motif folds, generally under mildly acidic conditions. Analysis of dC homo-oligonucleotide strands ranging in length from 10 to 30 nucleotides by five different pH-dependent methods identified a pattern in strand length vs stability. Beginning with dC11, which does not fold, the transition pH (pHT) increased with chain length with the addition of up to four nucleotides, after which the stability dramatically decreased, and the trend repeated this cycle up to dC27. The analysis found dCn strands of length 15, 19, 23, and 27 nucleotides (i.e., 4n-1) to have pHT values >7.2 and thermal stabilities >37 °C at pH 7.0. Model studies using thymidine nucleotides to lock in i-motif loop lengths support the conclusion that the most stable dCn i-motifs possess one nucleotide in each of the three loops and a core built of an even number of base pairs. The pattern identified from the model studies occurs with a frequency of four nucleotides at lengths of 15, 19, 23, and 27 in accordance with the results obtained for the dCn strands. This observation led us to interrogate the human genome for dCn runs. Inspection of the human genome indicates that dCn runs are enriched in critical regions of the genome (promoters, UTRs, and introns), while being depleted in coding and intergenic regions, and these findings may have biological implications. Lastly, the ability to tune i-motif stabilities by the length of the strand might be harnessed for stimulus-responsive applications in DNA scaffolds, sensors, nanotechnology, and other chemical applications.
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Affiliation(s)
- Aaron M Fleming
- Department of Chemistry, University of Utah , 315 South 1400 East, Salt Lake City, Utah 84112-0850, United States
| | - Yun Ding
- Department of Chemistry, University of Utah , 315 South 1400 East, Salt Lake City, Utah 84112-0850, United States
| | - R Aaron Rogers
- Department of Chemistry, University of Utah , 315 South 1400 East, Salt Lake City, Utah 84112-0850, United States
| | - Judy Zhu
- Department of Chemistry, University of Utah , 315 South 1400 East, Salt Lake City, Utah 84112-0850, United States
| | - Julia Zhu
- Department of Chemistry, University of Utah , 315 South 1400 East, Salt Lake City, Utah 84112-0850, United States
| | - Ashlee D Burton
- Department of Chemistry, University of Utah , 315 South 1400 East, Salt Lake City, Utah 84112-0850, United States
| | - Connor B Carlisle
- Department of Chemistry, University of Utah , 315 South 1400 East, Salt Lake City, Utah 84112-0850, United States
| | - Cynthia J Burrows
- Department of Chemistry, University of Utah , 315 South 1400 East, Salt Lake City, Utah 84112-0850, United States
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30
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Alba JJ, Sadurní A, Gargallo R. Nucleic Acid i-Motif Structures in Analytical Chemistry. Crit Rev Anal Chem 2016; 46:443-54. [DOI: 10.1080/10408347.2016.1143347] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Joan Josep Alba
- Department of Analytical Chemistry, University of Barcelona, Barcelona, Spain
| | - Anna Sadurní
- Department of Analytical Chemistry, University of Barcelona, Barcelona, Spain
| | - Raimundo Gargallo
- Department of Analytical Chemistry, University of Barcelona, Barcelona, Spain
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31
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Fujii T, Sugimoto N. Loop nucleotides impact the stability of intrastrand i-motif structures at neutral pH. Phys Chem Chem Phys 2016; 17:16719-22. [PMID: 26058487 DOI: 10.1039/c5cp02794b] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The stability of i-motif structures at neutral pH is of interest due to the potential of these structures to impact gene expression. A systematic investigation of loop sequence and length revealed that certain loop nucleobases stabilize i-motif quadruplexes.
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Affiliation(s)
- Taiga Fujii
- Frontier Institute for Biomolecular Engineering Research (FIBER), Konan University, 8-9-1 Minatojima-minamimachi, Chuo-ku, Kobe 650-0047, Japan.
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32
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Bedrat A, Lacroix L, Mergny JL. Re-evaluation of G-quadruplex propensity with G4Hunter. Nucleic Acids Res 2016; 44:1746-59. [PMID: 26792894 PMCID: PMC4770238 DOI: 10.1093/nar/gkw006] [Citation(s) in RCA: 423] [Impact Index Per Article: 52.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Accepted: 01/03/2016] [Indexed: 01/01/2023] Open
Abstract
Critical evidence for the biological relevance of G-quadruplexes (G4) has recently been obtained in seminal studies performed in a variety of organisms. Four-stranded G-quadruplex DNA structures are promising drug targets as these non-canonical structures appear to be involved in a number of key biological processes. Given the growing interest for G4, accurate tools to predict G-quadruplex propensity of a given DNA or RNA sequence are needed. Several algorithms such as Quadparser predict quadruplex forming propensity. However, a number of studies have established that sequences that are not detected by these tools do form G4 structures (false negatives) and that other sequences predicted to form G4 structures do not (false positives). Here we report development and testing of a radically different algorithm, G4Hunter that takes into account G-richness and G-skewness of a given sequence and gives a quadruplex propensity score as output. To validate this model, we tested it on a large dataset of 392 published sequences and experimentally evaluated quadruplex forming potential of 209 sequences using a combination of biophysical methods to assess quadruplex formation in vitro. We experimentally validated the G4Hunter algorithm on a short complete genome, that of the human mitochondria (16.6 kb), because of its relatively high GC content and GC skewness as well as the biological relevance of these quadruplexes near instability hotspots. We then applied the algorithm to genomes of a number of species, including humans, allowing us to conclude that the number of sequences capable of forming stable quadruplexes (at least in vitro) in the human genome is significantly higher, by a factor of 2–10, than previously thought.
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Affiliation(s)
- Amina Bedrat
- Université de Bordeaux, ARNA Laboratory, F-33000 Bordeaux, France Inserm U1212, CNRS UMR 5320, IECB, F-33600 Pessac, France
| | - Laurent Lacroix
- CNRS-Université de Toulouse UMR5099, F-31000 Toulouse, France
| | - Jean-Louis Mergny
- Université de Bordeaux, ARNA Laboratory, F-33000 Bordeaux, France Inserm U1212, CNRS UMR 5320, IECB, F-33600 Pessac, France
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33
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Benabou S, Garavís M, Lyonnais S, Eritja R, González C, Gargallo R. Understanding the effect of the nature of the nucleobase in the loops on the stability of the i-motif structure. Phys Chem Chem Phys 2016; 18:7997-8004. [DOI: 10.1039/c5cp07428b] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The nature of bases in the loops affects the acid–base and thermal stability of i-motif structures.
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Affiliation(s)
- Sanae Benabou
- Department of Analytical Chemistry
- University of Barcelona
- E-08028 Barcelona
- Spain
| | - Miguel Garavís
- Institute of Physical Chemistry “Rocasolano”
- CSIC
- E-28006 Madrid
- Spain
| | - Sébastien Lyonnais
- Institute of Molecular Biology of Barcelona (IBMB-CSIC)
- 08028 Barcelona
- Spain
| | - Ramon Eritja
- Institute for Advanced Chemistry of Catalonia (IQAC-CSIC)
- CIBER-BBN
- E-08034 Barcelona
- Spain
| | - Carlos González
- Institute of Physical Chemistry “Rocasolano”
- CSIC
- E-28006 Madrid
- Spain
- BIOESTRAN
| | - Raimundo Gargallo
- Department of Analytical Chemistry
- University of Barcelona
- E-08028 Barcelona
- Spain
- BIOESTRAN
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34
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Ding Y, Fleming AM, He L, Burrows CJ. Unfolding Kinetics of the Human Telomere i-Motif Under a 10 pN Force Imposed by the α-Hemolysin Nanopore Identify Transient Folded-State Lifetimes at Physiological pH. J Am Chem Soc 2015; 137:9053-60. [PMID: 26110559 PMCID: PMC4513840 DOI: 10.1021/jacs.5b03912] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
![]()
Cytosine
(C)-rich DNA can adopt i-motif folds under acidic conditions,
with the human telomere i-motif providing a well-studied example.
The dimensions of this i-motif are appropriate for capture in the
nanocavity of the α-hemolysin (α-HL) protein pore under
an electrophoretic force. Interrogation of the current vs time (i–t) traces when the i-motif interacts
with α-HL identified characteristic signals that were pH dependent.
These features were evaluated from pH 5.0 to 7.2, a region surrounding
the transition pH of the i-motif (6.1). When the i-motif without polynucleotide
tails was studied at pH 5.0, the folded structure entered the nanocavity
of α-HL from either the top or bottom face to yield characteristic
current patterns. Addition of a 5′ 25-mer poly-2′-deoxyadensosine
tail allowed capture of the i-motif from the unfolded terminus, and
this was used to analyze the pH dependency of unfolding. At pH values
below the transition point, only folded strands were observed, and
when the pH was increased above the transition pH, the number of folded
events decreased, while the unfolded events increased. At pH 6.8 and
7.2 4% and 2% of the strands were still folded, respectively. The
lifetimes for the folded states at pH 6.8 and 7.2 were 21 and 9 ms,
respectively, at 160 mV electrophoretic force. These lifetimes are
sufficiently long to affect enzymes operating on DNA. Furthermore,
these transient lifetimes are readily obtained using the α-HL
nanopore, a feature that is not easily achievable by other methods.
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Affiliation(s)
- Yun Ding
- Department of Chemistry, University of Utah, 315 S 1400 East, Salt Lake City, Utah 84112-0850, United States
| | - Aaron M Fleming
- Department of Chemistry, University of Utah, 315 S 1400 East, Salt Lake City, Utah 84112-0850, United States
| | - Lidong He
- Department of Chemistry, University of Utah, 315 S 1400 East, Salt Lake City, Utah 84112-0850, United States
| | - Cynthia J Burrows
- Department of Chemistry, University of Utah, 315 S 1400 East, Salt Lake City, Utah 84112-0850, United States
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35
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Lannes L, Halder S, Krishnan Y, Schwalbe H. Tuning the pH Response of i-Motif DNA Oligonucleotides. Chembiochem 2015; 16:1647-56. [PMID: 26032298 DOI: 10.1002/cbic.201500182] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Indexed: 12/19/2022]
Abstract
Cytosine-rich single-stranded DNA oligonucleotides are able to adopt an i-motif conformation, a four-stranded structure, near a pH of 6. This unique pH-dependent conformational switch is reversible and hence can be controlled by changing the pH. Here, we show that the pH response range of the human telomeric i-motif can be shifted towards more basic pH values by introducing 5-methylcytidines (5-MeC) and towards more acidic pH values by introducing 5-bromocytidines (5-BrC). No thermal destabilisation was observed in these chemically modified i-motif sequences. The time required to attain the new conformation in response to sudden pH changes was slow for all investigated sequences but was found to be ten times faster in the 5-BrC derivative of the i-motif.
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Affiliation(s)
- Laurie Lannes
- Institute for Organic Chemistry and Chemical Biology, Center for Biomolecular Magnetic Resonance (BMRZ), Johann Wolfgang Goethe-University Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt/Main (Germany)
| | - Saheli Halder
- National Centre for Biological Sciences, TIFR, GKVK Campus, Bellary Road, Bangalore 560065 (India)
| | - Yamuna Krishnan
- National Centre for Biological Sciences, TIFR, GKVK Campus, Bellary Road, Bangalore 560065 (India).,Department of Chemistry, University of Chicago, E305, GCIS, 929 E, 57th Street, Chicago, IL 60637 (USA)
| | - Harald Schwalbe
- Institute for Organic Chemistry and Chemical Biology, Center for Biomolecular Magnetic Resonance (BMRZ), Johann Wolfgang Goethe-University Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt/Main (Germany).
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36
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Halder S, Krishnan Y. Design of ultrasensitive DNA-based fluorescent pH sensitive nanodevices. NANOSCALE 2015; 7:10008-10012. [PMID: 25990365 DOI: 10.1039/c5nr01158b] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Here we tune the pH sensitivity of a DNA-based conformational switch, called the I-switch, to yield a set of fluorescent pH sensitive nanodevices with a collective, expanded pH sensing regime from 5.3 to 7.5. The expanded pH regime of this new family of I-switches originates from a dramatic improvement in the overall percentage signal change in response to pH of these nanodevices.
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Affiliation(s)
- Saheli Halder
- National Centre for Biological Sciences, TIFR, GKVK, Bellary Road, Bangalore 560 065, India
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37
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Garavís M, Escaja N, Gabelica V, Villasante A, González C. Centromeric Alpha-Satellite DNA Adopts Dimeric i-Motif Structures Capped by AT Hoogsteen Base Pairs. Chemistry 2015; 21:9816-24. [PMID: 26013031 DOI: 10.1002/chem.201500448] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Indexed: 11/11/2022]
Abstract
Human centromeric alpha-satellite DNA is composed of tandem arrays of two types of 171 bp monomers; type A and type B. The differences between these types are concentrated in a 17 bp region of the monomer called the A/B box. Here, we have determined the solution structure of the C-rich strand of the two main variants of the human alpha-satellite A box. We show that, under acidic conditions, the C-rich strands of two A boxes self-recognize and form a head-to-tail dimeric i-motif stabilized by four intercalated hemi-protonated C:C(+) base pairs. Interestingly, the stack of C:C(+) base pairs is capped by T:T and Hoogsteen A:T base pairs. The two main variants of the A box adopt a similar three-dimensional structure, although the residues involved in the formation of the i-motif core are different in each case. Together with previous studies showing that the B box (known as the CENP-B box) also forms dimeric i-motif structures, our finding of this non-canonical structure in the A box shows that centromeric alpha satellites in all human chromosomes are able to form i-motifs, which consequently raises the possibility that these structures may play a role in the structural organization of the centromere.
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Affiliation(s)
- Miguel Garavís
- Instituto de Química Física Rocasolano, CSIC, Serrano 119, 28006 Madrid (Spain).,Centro de Biología Molecular, "Severo Ochoa" (CSIC-UAM), Universidad Autónoma de Madrid, Nicolás Cabrera 1, 28049 Madrid (Spain)
| | - Núria Escaja
- Departament de Química Orgànica and IBUB, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona (Spain)
| | - Valérie Gabelica
- Univ. Bordeaux, ARNA Laboratory, IECB, 2 rue Robert Escarpit 33600 Pessac (France).,Inserm, ARNA Laboratory, 146 Rue Leo Saignat, 33000 Bordeaux (France)
| | - Alfredo Villasante
- Centro de Biología Molecular, "Severo Ochoa" (CSIC-UAM), Universidad Autónoma de Madrid, Nicolás Cabrera 1, 28049 Madrid (Spain)
| | - Carlos González
- Instituto de Química Física Rocasolano, CSIC, Serrano 119, 28006 Madrid (Spain).
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38
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Ung HU, Moehlig AR, Kudla RA, Mueller LJ, Oomens J, Berden G, Morton TH. Proton-bound dimers of 1-methylcytosine and its derivatives: vibrational and NMR spectroscopy. Phys Chem Chem Phys 2014; 15:19001-12. [PMID: 24096726 DOI: 10.1039/c3cp52260a] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Vibrational spectroscopy and NMR demonstrate that the proton-bound dimer of 1-methylcytosine, 1, has an unsymmetrical structure at room temperature. In the gas phase, investigation of isolated homodimer 1 reveals five fundamental NH vibrations by IR Multiple Photon Dissociation (IRMPD) action spectroscopy. The NH···N stretching vibration between the two ring nitrogens exhibits a frequency of 1570 cm(-1), as confirmed by examination of the proton-bound homodimers of 5-fluoro-1-methycytosine, 2, and of 1,5-dimethylcytosine, 3, which display absorptions in the same region that disappear upon deuterium substitution. (13)C, and (15)N NMR of the solid iodide salt of 1 confirm the nonequivalence of the two rings in the anhydrous proton-bound homodimer at room temperature. IRMPD spectra of the three possible heterodimers also show NH···N stretches in the same domain, and at least one of the heterodimers, the proton-bound dimer of 1,5-dimethylcytosine with 1-methylcytosine, exhibits two bands suggestive of the presence of two tautomers close in energy.
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Affiliation(s)
- Hou U Ung
- Department of Chemistry, University of California, Riverside, CA 92521-0403, USA.
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39
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Benabou S, Aviñó A, Eritja R, González C, Gargallo R. Fundamental aspects of the nucleic acid i-motif structures. RSC Adv 2014. [DOI: 10.1039/c4ra02129k] [Citation(s) in RCA: 129] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The latest research on fundamental aspects of i-motif structures is reviewed with special attention to their hypothetical rolein vivo.
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Affiliation(s)
- S. Benabou
- Department of Analytical Chemistry
- University of Barcelona
- E-08028 Barcelona, Spain
| | - A. Aviñó
- Institute for Advanced Chemistry of Catalonia (IQAC-CSIC)
- CIBER-BBN Networking Centre on Bioengineering
- Biomaterials and Nanomedicine
- E-08034 Barcelona, Spain
| | - R. Eritja
- Institute for Advanced Chemistry of Catalonia (IQAC-CSIC)
- CIBER-BBN Networking Centre on Bioengineering
- Biomaterials and Nanomedicine
- E-08034 Barcelona, Spain
| | - C. González
- Institute of Physical Chemistry “Rocasolano”
- CSIC
- E-28006 Madrid, Spain
| | - R. Gargallo
- Department of Analytical Chemistry
- University of Barcelona
- E-08028 Barcelona, Spain
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