1
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Víšková P, Ištvánková E, Ryneš J, Džatko Š, Loja T, Živković ML, Rigo R, El-Khoury R, Serrano-Chacón I, Damha MJ, González C, Mergny JL, Foldynová-Trantírková S, Trantírek L. In-cell NMR suggests that DNA i-motif levels are strongly depleted in living human cells. Nat Commun 2024; 15:1992. [PMID: 38443388 PMCID: PMC10914786 DOI: 10.1038/s41467-024-46221-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2023] [Accepted: 02/13/2024] [Indexed: 03/07/2024] Open
Abstract
I-Motifs (iM) are non-canonical DNA structures potentially forming in the accessible, single-stranded, cytosine-rich genomic regions with regulatory roles. Chromatin, protein interactions, and intracellular properties seem to govern iM formation at sites with i-motif formation propensity (iMFPS) in human cells, yet their specific contributions remain unclear. Using in-cell NMR with oligonucleotide iMFPS models, we monitor iM-associated structural equilibria in asynchronous and cell cycle-synchronized HeLa cells at 37 °C. Our findings show that iMFPS displaying pHT < 7 under reference in vitro conditions occur predominantly in unfolded states in cells, while those with pHT > 7 appear as a mix of folded and unfolded states depending on the cell cycle phase. Comparing these results with previous data obtained using an iM-specific antibody (iMab) reveals that cell cycle-dependent iM formation has a dual origin, and iM formation concerns only a tiny fraction (possibly 1%) of genomic sites with iM formation propensity. We propose a comprehensive model aligning observations from iMab and in-cell NMR and enabling the identification of iMFPS capable of adopting iM structures under physiological conditions in living human cells. Our results suggest that many iMFPS may have biological roles linked to their unfolded states.
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Affiliation(s)
- Pavlína Víšková
- Central European Institute of Technology, Masaryk University, 625 00, Brno, Czech Republic
- National Centre for Biomolecular Research, Masaryk University, 625 00, Brno, Czech Republic
| | - Eva Ištvánková
- Central European Institute of Technology, Masaryk University, 625 00, Brno, Czech Republic
- National Centre for Biomolecular Research, Masaryk University, 625 00, Brno, Czech Republic
| | - Jan Ryneš
- Central European Institute of Technology, Masaryk University, 625 00, Brno, Czech Republic
| | - Šimon Džatko
- Central European Institute of Technology, Masaryk University, 625 00, Brno, Czech Republic
- Centre for Advanced Materials Application, Slovak Academy of Sciences, 845 11, Bratislava, Slovakia
| | - Tomáš Loja
- Central European Institute of Technology, Masaryk University, 625 00, Brno, Czech Republic
| | - Martina Lenarčič Živković
- Central European Institute of Technology, Masaryk University, 625 00, Brno, Czech Republic
- Slovenian NMR Centre, National Institute of Chemistry, SI-1000, Ljubljana, Slovenia
| | - Riccardo Rigo
- Central European Institute of Technology, Masaryk University, 625 00, Brno, Czech Republic
- Pharmaceutical and Pharmacological Sciences Department, University of Padova, 35131, Padova, Italy
| | - Roberto El-Khoury
- Department of Chemistry, McGill University, Montreal, QC, H3A0B8, Canada
| | - Israel Serrano-Chacón
- Instituto de Química Física 'Blas Cabrera', CSIC, C/Serrano 119, 28006, Madrid, Spain
| | - Masad J Damha
- Department of Chemistry, McGill University, Montreal, QC, H3A0B8, Canada
| | - Carlos González
- Instituto de Química Física 'Blas Cabrera', CSIC, C/Serrano 119, 28006, Madrid, Spain
| | - Jean-Louis Mergny
- Institute of Biophysics, Czech Academy of Sciences, Brno, 612 00, Czech Republic
- Laboratoire d'Optique & Biosciences, Institut Polytechnique de Paris, Inserm, CNRS, Ecole Polytechnique, Palaiseau, 91120, France
| | - Silvie Foldynová-Trantírková
- Central European Institute of Technology, Masaryk University, 625 00, Brno, Czech Republic.
- Institute of Biophysics, Czech Academy of Sciences, Brno, 612 00, Czech Republic.
| | - Lukáš Trantírek
- Central European Institute of Technology, Masaryk University, 625 00, Brno, Czech Republic.
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2
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Yazdani K, Seshadri S, Tillo D, Yang M, Sibley CD, Vinson C, Schneekloth JS. Decoding complexity in biomolecular recognition of DNA i-motifs with microarrays. Nucleic Acids Res 2023; 51:12020-12030. [PMID: 37962331 PMCID: PMC10711443 DOI: 10.1093/nar/gkad981] [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: 04/25/2023] [Revised: 09/28/2023] [Accepted: 10/24/2023] [Indexed: 11/15/2023] Open
Abstract
DNA i-motifs (iMs) are non-canonical C-rich secondary structures implicated in numerous cellular processes. Though iMs exist throughout the genome, our understanding of iM recognition by proteins or small molecules is limited to a few examples. We designed a DNA microarray containing 10976 genomic iM sequences to examine the binding profiles of four iM-binding proteins, mitoxantrone and the iMab antibody. iMab microarray screens demonstrated that pH 6.5, 5% BSA buffer was optimal, and fluorescence was correlated with iM C-tract length. hnRNP K broadly recognizes diverse iM sequences, favoring 3-5 cytosine repeats flanked by thymine-rich loops of 1-3 nucleotides. Array binding mirrored public ChIP-Seq datasets, in which 35% of well-bound array iMs are enriched in hnRNP K peaks. In contrast, other reported iM-binding proteins had weaker binding or preferred G-quadruplex (G4) sequences instead. Mitoxantrone broadly binds both shorter iMs and G4s, consistent with an intercalation mechanism. These results suggest that hnRNP K may play a role in iM-mediated regulation of gene expression in vivo, whereas hnRNP A1 and ASF/SF2 are possibly more selective in their binding preferences. This powerful approach represents the most comprehensive investigation of how biomolecules selectively recognize genomic iMs to date.
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Affiliation(s)
- Kamyar Yazdani
- Chemical Biology Laboratory, National Cancer Institute, 1050 Boyle St., Frederick, MD 21702, USA
| | - Srinath Seshadri
- Chemical Biology Laboratory, National Cancer Institute, 1050 Boyle St., Frederick, MD 21702, USA
| | - Desiree Tillo
- Genome Analysis Unit, National Cancer Institute, 37 Convent Dr., Bethesda, MD 20892, USA
| | - Mo Yang
- Chemical Biology Laboratory, National Cancer Institute, 1050 Boyle St., Frederick, MD 21702, USA
| | - Christopher D Sibley
- Chemical Biology Laboratory, National Cancer Institute, 1050 Boyle St., Frederick, MD 21702, USA
| | - Charles Vinson
- Laboratory of Metabolism, National Cancer Institute, 37 Convent Dr., Bethesda, MD 20892, USA
| | - John S Schneekloth
- Chemical Biology Laboratory, National Cancer Institute, 1050 Boyle St., Frederick, MD 21702, USA
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3
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Yazdani K, Seshadri S, Tillo D, Vinson C, Schneekloth JS. DECODING COMPLEXITY IN BIOMOLECULAR RECOGNITION OF DNA I-MOTIFS. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.19.537548. [PMID: 37131644 PMCID: PMC10153190 DOI: 10.1101/2023.04.19.537548] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
DNA i-motifs (iMs) are non-canonical C-rich secondary structures implicated in numerous cellular processes. Though iMs exist throughout the genome, our understanding of iM recognition by proteins or small molecules is limited to a few examples. We designed a DNA microarray containing 10,976 genomic iM sequences to examine the binding profiles of four iM-binding proteins, mitoxantrone, and the iMab antibody. iMab microarray screens demonstrated that pH 6.5, 5% BSA buffer was optimal, and fluorescence was correlated with iM C-tract length. hnRNP K broadly recognizes diverse iM sequences, favoring 3-5 cytosine repeats flanked by thymine-rich loops of 1-3 nucleotides. Array binding mirrored public ChIP-Seq datasets, in which 35% of well-bound array iMs are enriched in hnRNP K peaks. In contrast, other reported iM-binding proteins had weaker binding or preferred G-quadruplex (G4) sequences instead. Mitoxantrone broadly binds both shorter iMs and G4s, consistent with an intercalation mechanism. These results suggest that hnRNP K may play a role in iM-mediated regulation of gene expression in vivo, whereas hnRNP A1 and ASF/SF2 are possibly more selective in their binding preferences. This powerful approach represents the most comprehensive investigation of how biomolecules selectively recognize genomic iMs to date.
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Affiliation(s)
- Kamyar Yazdani
- Chemical Biology Laboratory, National Cancer Institute, 1050 Boyle St., Frederick, MD 21702
| | - Srinath Seshadri
- Chemical Biology Laboratory, National Cancer Institute, 1050 Boyle St., Frederick, MD 21702
| | - Desiree Tillo
- Genome Analysis Unit, National Cancer Institute, 37 Convent Dr., Bethesda, MD 20892
| | - Charles Vinson
- Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, 37 Convent Dr., Bethesda MD 20892
| | - John S Schneekloth
- Chemical Biology Laboratory, National Cancer Institute, 1050 Boyle St., Frederick, MD 21702
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4
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Mustafa G, Gyawali P, Taylor JA, Maleki P, Nunez MV, Guntrum MC, Shiekh S, Balci H. A single molecule investigation of i-motif stability, folding intermediates, and potential as in-situ pH sensor. Front Mol Biosci 2022; 9:977113. [PMID: 36072435 PMCID: PMC9441956 DOI: 10.3389/fmolb.2022.977113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 07/26/2022] [Indexed: 11/13/2022] Open
Abstract
We present a collection of single molecule work on the i-motif structure formed by the human telomeric sequence. Even though it was largely ignored in earlier years of its discovery due to its modest stability and requirement for low pH levels (pH < 6.5), the i-motif has been attracting more attention recently as both a physiologically relevant structure and as a potent pH sensor. In this manuscript, we establish single molecule Förster resonance energy transfer (smFRET) as a tool to study the i-motif over a broad pH and ionic conditions. We demonstrate pH and salt dependence of i-motif formation under steady state conditions and illustrate the intermediate states visited during i-motif folding in real time at the single molecule level. We also show the prominence of intermediate folding states and reversible folding/unfolding transitions. We present an example of using the i-motif as an in-situ pH sensor and use this sensor to establish the time scale for the pH drop in a commonly used oxygen scavenging system.
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5
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Chikhale RV, Guneri D, Yuan R, Morris CJ, Waller ZAE. Identification of sugar-containing natural products that interact with i-motif DNA. Bioorg Med Chem Lett 2022; 73:128886. [PMID: 35835380 DOI: 10.1016/j.bmcl.2022.128886] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 07/05/2022] [Accepted: 07/07/2022] [Indexed: 11/30/2022]
Abstract
There are thousands of compounds shown to interact with G-quadruplex DNA, yet very few which target i-motif (iM) DNA. Previous work showed that tobramycin can interact with iM- DNA, indicating the potential for sugar-molecules to target these structures. Computational approaches indicated that the sugar-containing natural products baicalin and geniposidic acid had potential to target iM-DNA. We assessed the DNA interacting properties of these compounds using FRET-based DNA melting and a fluorescence-based displacement assay using iM-DNA structures from the human telomere and the insulin linked polymorphic region (ILPR), as well as complementary G-quadruplex and double stranded DNA. Both baicalin and geniposidic acid show promise as iM-interacting compounds with potential for use in experiments into the structure and function of i-motif forming DNA sequences and present starting points for further synthetic development of these as probes for iM-DNA.
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Affiliation(s)
| | - Dilek Guneri
- UCL School of Pharmacy, 29-39 Brunswick Square, London WC1N 1AX, UK
| | - Robert Yuan
- UCL School of Pharmacy, 29-39 Brunswick Square, London WC1N 1AX, UK
| | | | - Zoë A E Waller
- UCL School of Pharmacy, 29-39 Brunswick Square, London WC1N 1AX, UK.
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6
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Abstract
Invention of DNA origami has transformed the fabrication and application of biological nanomaterials. In this review, we discuss DNA origami nanoassemblies according to their four fundamental mechanical properties in response to external forces: elasticity, pliability, plasticity and stability. While elasticity and pliability refer to reversible changes in structures and associated properties, plasticity shows irreversible variation in topologies. The irreversible property is also inherent in the disintegration of DNA nanoassemblies, which is manifested by its mechanical stability. Disparate DNA origami devices in the past decade have exploited the mechanical regimes of pliability, elasticity, and plasticity, among which plasticity has shown its dominating potential in biomechanical and physiochemical applications. On the other hand, the mechanical stability of the DNA origami has been used to understand the mechanics of the assembly and disassembly of DNA nano-devices. At the end of this review, we discuss the challenges and future development of DNA origami nanoassemblies, again, from these fundamental mechanical perspectives.
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Affiliation(s)
- Jiahao Ji
- Department of Chemistry and Biochemistry, Kent State University, Kent, OH, 44240, USA.
| | - Deepak Karna
- Department of Chemistry and Biochemistry, Kent State University, Kent, OH, 44240, USA.
| | - Hanbin Mao
- Department of Chemistry and Biochemistry, Kent State University, Kent, OH, 44240, USA.
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7
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Buglione E, Salerno D, Marrano CA, Cassina V, Vesco G, Nardo L, Dacasto M, Rigo R, Sissi C, Mantegazza F. Nanomechanics of G-quadruplexes within the promoter of the KIT oncogene. Nucleic Acids Res 2021; 49:4564-4573. [PMID: 33849064 PMCID: PMC8096272 DOI: 10.1093/nar/gkab079] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 01/07/2021] [Accepted: 04/09/2021] [Indexed: 12/31/2022] Open
Abstract
G-quadruplexes (G4s) are tetrahelical DNA structures stabilized by four guanines paired via Hoogsteen hydrogen bonds into quartets. While their presence within eukaryotic DNA is known to play a key role in regulatory processes, their functional mechanisms are still under investigation. In the present work, we analysed the nanomechanical properties of three G4s present within the promoter of the KIT proto-oncogene from a single-molecule point of view through the use of magnetic tweezers (MTs). The study of DNA extension fluctuations under negative supercoiling allowed us to identify a characteristic fingerprint of G4 folding. We further analysed the energetic contribution of G4 to the double-strand denaturation process in the presence of negative supercoiling, and we observed a reduction in the energy required for strands separation.
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Affiliation(s)
- Enrico Buglione
- School of Medicine and Surgery, BioNanoMedicine Center NANOMIB, University of Milano-Bicocca, 20854 Vedano al Lambro (MB), Italy
| | - Domenico Salerno
- School of Medicine and Surgery, BioNanoMedicine Center NANOMIB, University of Milano-Bicocca, 20854 Vedano al Lambro (MB), Italy
| | - Claudia Adriana Marrano
- School of Medicine and Surgery, BioNanoMedicine Center NANOMIB, University of Milano-Bicocca, 20854 Vedano al Lambro (MB), Italy
| | - Valeria Cassina
- School of Medicine and Surgery, BioNanoMedicine Center NANOMIB, University of Milano-Bicocca, 20854 Vedano al Lambro (MB), Italy
| | - Guglielmo Vesco
- School of Medicine and Surgery, BioNanoMedicine Center NANOMIB, University of Milano-Bicocca, 20854 Vedano al Lambro (MB), Italy
| | - Luca Nardo
- School of Medicine and Surgery, BioNanoMedicine Center NANOMIB, University of Milano-Bicocca, 20854 Vedano al Lambro (MB), Italy
| | - Mauro Dacasto
- Department of Comparative Biomedicine and Food Science, University of Padova, 35020 Legnaro (PD), Italy
| | - Riccardo Rigo
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, 35131 Padova (PD), Italy
| | - Claudia Sissi
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, 35131 Padova (PD), Italy.,Interdepartmental Research Center for Innovative Biotechnologies (CRIBI), University of Padova, 35121 Padova (PD), Italy
| | - Francesco Mantegazza
- School of Medicine and Surgery, BioNanoMedicine Center NANOMIB, University of Milano-Bicocca, 20854 Vedano al Lambro (MB), Italy
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8
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Sengupta P, Bose D, Chatterjee S. The Molecular Tête-à-Tête between G-Quadruplexes and the i-motif in the Human Genome. Chembiochem 2021; 22:1517-1537. [PMID: 33355980 DOI: 10.1002/cbic.202000703] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 12/16/2020] [Indexed: 12/22/2022]
Abstract
G-Quadruplex (GQ) and i-motif structures are the paradigmatic examples of nonclassical tetrastranded nucleic acids having multifarious biological functions and widespread applications in therapeutics and material science. Recently, tetraplexes emerged as promising anticancer targets due to their structural robustness, gene-regulatory roles, and predominant distribution at specific loci of oncogenes. However, it is arguable whether the i-motif evolves in the complementary single-stranded region after GQ formation in its opposite strand and vice versa. In this review, we address the prerequisites and significance of the simultaneous and/or mutually exclusive formation of GQ and i-motif structures at complementary and sequential positions in duplexes in the cellular milieu. We discussed how their dynamic interplay Sets up cellular homeostasis and exacerbates carcinogenesis. The review gives insights into the spatiotemporal formation of GQ and i-motifs that could be harnessed to design different types of reporter systems and diagnostic platforms for potential bioanalytical and therapeutic intervention.
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Affiliation(s)
- Pallabi Sengupta
- Department of Biophysics, Bose Institute, Centenary Campus, P-1/12, C.I.T. Scheme VIIM, Kankurgachi, Kolkata, 700054, West Bengal, India
| | - Debopriya Bose
- Department of Biophysics, Bose Institute, Centenary Campus, P-1/12, C.I.T. Scheme VIIM, Kankurgachi, Kolkata, 700054, West Bengal, India
| | - Subhrangsu Chatterjee
- Department of Biophysics, Bose Institute, Centenary Campus, P-1/12, C.I.T. Scheme VIIM, Kankurgachi, Kolkata, 700054, West Bengal, India
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9
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Wang S, Liang L, Tang J, Cai Y, Zhao C, Fang S, Wang H, Weng T, Wang L, Wang D. Label-free single-molecule identification of telomere G-quadruplexes with a solid-state nanopore sensor. RSC Adv 2020; 10:27215-27224. [PMID: 35515777 PMCID: PMC9055465 DOI: 10.1039/d0ra05083k] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Accepted: 07/06/2020] [Indexed: 12/14/2022] Open
Abstract
Telomere sequences can spontaneously form G-quadruplexes (G4) in the presence of some cations. In view of their relevance to genetic processes and potential as therapeutic-targets, hitherto, a wealth of conventional techniques have been reported for interrogation of G4 conformation diversity and corresponding folding kinetics, most of which are limited in precision and sensitivity. This work introduces a label-free solid-state nanopore (SSN) approach for the determination of inter-, intra- and tandem molecular G4 with distinct base permutation in various cation buffers with a tailored aperture and meanwhile captures the single-molecule G4 folding process. SSN translocation properties elucidated that both inter- and intramolecular G4 generated higher current blockage with longer duration than flexible homopolymer nucleotide, and intramolecular G4 are structurally more stable with higher event frequency and longer blockage time than intermolecular ones; base arrangement played weak role in translocation behaviors; the same sequences with one, two and three G4 skeletons displayed an increase in current blockage and a gradual extension in dwell time with the increase of molecule size recorded in the same nanopore. We observed the conformation change of single-molecule G4 which indicated the existence of folding/unfolding equilibration in nanopore, and real-time test suggested a gradual formation of G4 with time. Our results could provide a continued and improved understanding of the underlying relevance of structural stability and G4 folding process by utilizing SSN platform which exhibits strategic potential advances over the other methods with high spatial and temporal resolution. Nanopore detection of single-molecule G-quadruplexes.![]()
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10
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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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11
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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: 235] [Impact Index Per Article: 47.0] [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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12
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Sabale PM, Tanpure AA, Srivatsan SG. Probing the competition between duplex and G-quadruplex/i-motif structures using a conformation-sensitive fluorescent nucleoside probe. Org Biomol Chem 2019; 16:4141-4150. [PMID: 29781489 PMCID: PMC6086326 DOI: 10.1039/c8ob00646f] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Double-stranded segments of a genome that can potentially form G-quadruplex (GQ) and/or i-motif (iM) structures are considered to be important regulatory elements. Hence, the development of a common probe that can detect GQ and iM structures and also distinguish them from a duplex structure will be highly useful in understanding the propensity of such segments to adopt duplex or non-canonical four-stranded structures. Here, we describe the utility of a conformation-sensitive fluorescent nucleoside analog, which was originally developed as a GQ sensor, in detecting the iM structures of C-rich DNA oligonucleotides (ONs). The analog is based on a 5-(benzofuran-2-yl)uracil scaffold, which when incorporated into C-rich ONs (e.g., telomeric repeats) fluorescently distinguishes an iM from random coil and duplex structures. Steady-state and time-resolved fluorescence techniques enabled the determination of transition pH for the transformation of a random coil to an iM structure. Furthermore, a qualitative understanding on the relative population of duplex and GQ/iM forms under physiological conditions could be gained by correlating the fluorescence, CD and thermal melting data. Taken together, this sensor could provide a general platform to profile double-stranded promoter regions in terms of their ability to adopt four-stranded structures, and also could support approaches to discover functional GQ and iM binders.
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Affiliation(s)
- Pramod M Sabale
- Department of Chemistry, Indian Institute of Science Education and Research (IISER), Pune, Dr. Homi Bhabha Road, Pune 411008, India.
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13
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Manna S, Srivatsan SG. Fluorescence-based tools to probe G-quadruplexes in cell-free and cellular environments. RSC Adv 2018; 8:25673-25694. [PMID: 30210793 PMCID: PMC6130854 DOI: 10.1039/c8ra03708f] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Accepted: 07/08/2018] [Indexed: 12/26/2022] Open
Abstract
Biophysical and biochemical investigations provide compelling evidence connecting the four-stranded G-quadruplex (GQ) structure with its role in regulating multiple cellular processes. Hence, modulating the function of GQs by using small molecule binders is being actively pursued as a strategy to develop new chemotherapeutic agents. However, sequence diversity and structural polymorphism of GQs have posed immense challenges in terms of understanding what conformation a G-rich sequence adopts inside the cell and how to specifically target a GQ motif amidst several other GQ-forming sequences. In this context, here we review recent developments in the applications of biophysical tools that use fluorescence readout to probe the GQ structure and recognition in cell-free and cellular environments. First, we provide a detailed discussion on the utility of covalently labeled environment-sensitive fluorescent nucleoside analogs in assessing the subtle difference in GQ structures and their ligand binding abilities. Furthermore, a detailed discussion on structure-specific antibodies and small molecule probes used to visualize and confirm the existence of DNA and RNA GQs in cells is provided. We also highlight the open challenges in the study of tetraplexes (GQ and i-motif structures) and how addressing these challenges by developing new tools and techniques will have a profound impact on tetraplex-directed therapeutic strategies.
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Affiliation(s)
- Sudeshna Manna
- Department of Chemistry, Indian Institute of Science Education and Research (IISER), PuneDr. Homi Bhabha RoadPune 411008India
| | - Seergazhi G. Srivatsan
- Department of Chemistry, Indian Institute of Science Education and Research (IISER), PuneDr. Homi Bhabha RoadPune 411008India
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14
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Jonchhe S, Shrestha P, Ascencio K, Mao H. A New Concentration Jump Strategy Reveals the Lifetime of i-Motif at Physiological pH without Force. Anal Chem 2018; 90:3205-3210. [DOI: 10.1021/acs.analchem.7b04661] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Sagun Jonchhe
- Department of Chemistry and Biochemistry, Kent State University, Kent, Ohio 44242, United States
| | - Prakash Shrestha
- Department of Chemistry and Biochemistry, Kent State University, Kent, Ohio 44242, United States
| | - Katia Ascencio
- Department of Chemistry and Biochemistry, Kent State University, Kent, Ohio 44242, United States
| | - Hanbin Mao
- Department of Chemistry and Biochemistry, Kent State University, Kent, Ohio 44242, United States
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15
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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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16
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Yin B, Xie W, Liang L, Deng Y, He S, He F, Zhou D, Tlili C, Wang D. Covalent Modification of Silicon Nitride Nanopore by Amphoteric Polylysine for Short DNA Detection. ACS OMEGA 2017; 2:7127-7135. [PMID: 31457292 PMCID: PMC6645049 DOI: 10.1021/acsomega.7b01245] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Accepted: 10/06/2017] [Indexed: 05/11/2023]
Abstract
In this work, we demonstrate a chemical modification approach, by means of covalent-bonding amphoteric poly-l-lysine (PLL) on the interior nanopore surface, which could intensively protect the pore from etching when exposed in the electrolyte under various pH conditions (from pH 4 to 12). Nanopore was generated via simple current dielectric breakdown methodology, covalent modification was performed in three steps, and the functional nanopore was fully characterized in terms of chemical structure, hydrophilicity, and surface morphology. I-V curves were recorded under a broad range of pH stimuli to evaluate the stability of the chemical bonding layer; the plotted curves demonstrated that nanopore with a covalent bonding layer has good pH tolerance and showed apparent reversibility. In addition, we have also measured the conductance of modified nanopore with varied KCl concentration (from 0.1 mM to 1 M) at different pH conditions (pHs 5, 7, 9, and 11). The results suggested that the surface charge density does not fluctuate with variation in salt concentration, which inferred that the SiN x nanopore was fully covered by PLL. Moreover, the PLL functionalized nanopore has realized the detection of single-stranded DNA homopolymer translocation under bias voltage of 500 mV, and the 20 nt homopolymers could be evidently differentiated in terms of the current amplitude and dwell time at pHs 5, 8, and 11.
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