1
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Wang X, Martínez-Fernández L, Zhang Y, Wu P, Kohler B, Improta R, Chen J. Ultrafast Formation of a Delocalized Triplet-Excited State in an Epigenetically Modified DNA Duplex under Direct UV Excitation. J Am Chem Soc 2024; 146:1839-1848. [PMID: 38194423 DOI: 10.1021/jacs.3c04567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2024]
Abstract
Epigenetic modifications impart important functionality to nucleic acids during gene expression but may increase the risk of photoinduced gene mutations. Thus, it is crucial to understand how these modifications affect the photostability of duplex DNA. In this work, the ultrafast formation (<20 ps) of a delocalized triplet charge transfer (CT) state spreading over two stacked neighboring nucleobases after direct UV excitation is demonstrated in a DNA duplex, d(G5fC)9•d(G5fC)9, made of alternating guanine (G) and 5-formylcytosine (5fC) nucleobases. The triplet yield is estimated to be 8 ± 3%, and the lifetime of the triplet CT state is 256 ± 22 ns, indicating that epigenetic modifications dramatically alter the excited state dynamics of duplex DNA and may enhance triplet state-induced photochemistry.
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Affiliation(s)
- Xueli Wang
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Lara Martínez-Fernández
- Departamento de Química, Facultad de Ciencias and Institute for Advanced Research in Chemical Science (IADCHEM), Universidad Autónoma de Madrid, Campus de Excelencia UAM-CSIC, Cantoblanco, Madrid 28049, Spain
| | - Yuyuan Zhang
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, United States
| | - Peicong Wu
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
| | - Bern Kohler
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, United States
| | - Roberto Improta
- Istituto di Biostrutture e Bioimmagini CNR, Via De Amicis 95, Napoli I-80145, Italy
| | - Jinquan Chen
- State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200241, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, Shanxi, China
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2
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Bauer J, Reichl A, Tinnefeld P. Kinetic Referencing Allows Identification of Epigenetic Cytosine Modifications by Single-Molecule Hybridization Kinetics and Superresolution DNA-PAINT Microscopy. ACS NANO 2024; 18:1496-1503. [PMID: 38157484 DOI: 10.1021/acsnano.3c08451] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
We develop a DNA origami-based internal kinetic referencing system with a colocalized reference and target molecule to provide increased sensitivity and robustness for transient binding kinetics. To showcase this, we investigate the subtle changes in binding strength of DNA oligonucleotide hybrids induced by cytosine modifications. These cytosine modifications, especially 5-methylcytosine but also its oxidized derivatives, have been increasingly studied in the context of epigenetics. Recently revealed correlations of epigenetic modifications and disease also render them interesting biomarkers for early diagnosis. Internal kinetic referencing allows us to probe and compare the influence of the different epigenetic cytosine modifications on the strengths of 7-nucleotide long DNA hybrids with one or two modified nucleotides by single-molecule imaging of their transient binding, revealing subtle differences in binding times. Interestingly, the influence of epigenetic modifications depends on their position in the DNA strand, and in the case of two modifications, effects are additive. The sensitivity of the assay indicates its potential for the direct detection of epigenetic disease markers.
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Affiliation(s)
- Julian Bauer
- Department of Chemistry and Center for NanoScience, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377 München, Germany
| | - Andreas Reichl
- Department of Chemistry, Ludwig-Maximilians-Universität München, Würmtalstraße 201, 81377 München, Germany
| | - Philip Tinnefeld
- Department of Chemistry and Center for NanoScience, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377 München, Germany
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3
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Ashwood B, Jones MS, Lee Y, Sachleben JR, Ferguson AL, Tokmakoff A. Molecular insight into how the position of an abasic site modifies DNA duplex stability and dynamics. Biophys J 2024; 123:118-133. [PMID: 38006207 PMCID: PMC10808028 DOI: 10.1016/j.bpj.2023.11.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Revised: 10/19/2023] [Accepted: 11/22/2023] [Indexed: 11/26/2023] Open
Abstract
Local perturbations to DNA base-pairing stability from lesions and chemical modifications can alter the stability and dynamics of an entire oligonucleotide. End effects may cause the position of a disruption within a short duplex to influence duplex stability and structural dynamics, yet this aspect of nucleic acid modifications is often overlooked. We investigate how the position of an abasic site (AP site) impacts the stability and dynamics of short DNA duplexes. Using a combination of steady-state and time-resolved spectroscopy and molecular dynamics simulations, we unravel an interplay between AP-site position and nucleobase sequence that controls energetic and dynamic disruption to the duplex. The duplex is disrupted into two segments by an entropic barrier for base-pairing on each side of the AP site. The barrier induces fraying of the short segment when an AP site is near the termini. Shifting the AP site inward promotes a transition from short-segment fraying to fully encompassing the barrier into the thermodynamics of hybridization, leading to further destabilization of the duplex. Nucleobase sequence determines the length scale for this transition by tuning the barrier height and base-pair stability of the short segment, and certain sequences enable out-of-register base-pairing to minimize the barrier height.
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Affiliation(s)
- Brennan Ashwood
- Department of Chemistry, Institute for Biophysical Dynamics, and James Franck Institute, The University of Chicago, Chicago, Illinois
| | - Michael S Jones
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois
| | - Yumin Lee
- Department of Chemistry, Institute for Biophysical Dynamics, and James Franck Institute, The University of Chicago, Chicago, Illinois
| | - Joseph R Sachleben
- Biomolecular NMR Core Facility, Biological Sciences Division, The University of Chicago, Chicago, Illinois
| | - Andrew L Ferguson
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois.
| | - Andrei Tokmakoff
- Department of Chemistry, Institute for Biophysical Dynamics, and James Franck Institute, The University of Chicago, Chicago, Illinois.
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4
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Wu D, Huang K, Shi J, Liu S, Wang W, Jiang J, Ren H, Chen T, Ye S, Chen J, Wei W, Li X. Genome-Wide 5-Formylcytosine Redistribution in KCl-Stimulated Mouse Primary Cortical Neurons is Associated with Neuronal Activity. ACS Chem Neurosci 2023; 14:4352-4362. [PMID: 38019771 DOI: 10.1021/acschemneuro.3c00554] [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: 12/01/2023] Open
Abstract
An abundant accumulation of DNA demethylation intermediates has been identified in mammalian neurons. While the roles of 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) in neuronal function have been extensively studied, little is known about 5-formylcytosine (5fC) in neurons. Therefore, this study was to investigate the genome-wide distribution and potential functions of 5fC in neurons. In an in vitro culture model of mouse primary cortical neurons, we observed a dynamic increase in the total 5fC level in the neuronal genome after potassium chloride (KCl) stimulation. Subsequently, we employed chemical-labeling-enabled C-to-T conversion sequencing (CLEVER-seq) to examine the 5fC distribution at a single-base resolution. Bioinformatic analysis revealed that 5fC was enriched in promoter regions, and gene ontology (GO) analysis indicated that the differential formylation positions (DFP) were correlated with neuronal activities. Additionally, integration with previously published nascent RNA-seq data revealed a positive correlation between gene formylation and mRNA expression levels. As well, 6 neuro-activity-related genes with a positive correlation were validated. Furthermore, we observed higher chromatin accessibility and RNA pol II binding signals near the 5fC sites through multiomics analysis. Motif analysis identified potential reader proteins for 5fC. In conclusion, our work provides a valuable resource for studying the dynamic changes and functional roles of 5fC in activated mammalian neurons.
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Affiliation(s)
- Du Wu
- Department of Neurosurgery, Zhongnan Hospital of Wuhan University, 430071 Wuhan, China
- Brain Research Center, Zhongnan Hospital of Wuhan University, 430071 Wuhan, China
| | - Kaixin Huang
- Department of Neurosurgery, Zhongnan Hospital of Wuhan University, 430071 Wuhan, China
- Brain Research Center, Zhongnan Hospital of Wuhan University, 430071 Wuhan, China
| | - Jichun Shi
- Department of Neurosurgery, Zhongnan Hospital of Wuhan University, 430071 Wuhan, China
- Brain Research Center, Zhongnan Hospital of Wuhan University, 430071 Wuhan, China
| | - Sha Liu
- Department of General Practice, Zhongnan Hospital of Wuhan University, 430071 Wuhan, China
| | - Wenjing Wang
- Department of Neurosurgery, Zhongnan Hospital of Wuhan University, 430071 Wuhan, China
| | - Jiazhi Jiang
- Department of Neurosurgery, Zhongnan Hospital of Wuhan University, 430071 Wuhan, China
| | - Haobin Ren
- Cognitive Neuroepigenetics Laboratory, Queensland Brain Institute, The University of Queensland, Brisbane 4702, Australia
| | - Tongyu Chen
- Department of Neurosurgery, Zhongnan Hospital of Wuhan University, 430071 Wuhan, China
| | - Shengda Ye
- Department of Neurosurgery, Zhongnan Hospital of Wuhan University, 430071 Wuhan, China
| | - Jincao Chen
- Department of Neurosurgery, Zhongnan Hospital of Wuhan University, 430071 Wuhan, China
| | - Wei Wei
- Department of Neurosurgery, Zhongnan Hospital of Wuhan University, 430071 Wuhan, China
- Brain Research Center, Zhongnan Hospital of Wuhan University, 430071 Wuhan, China
| | - Xiang Li
- Department of Neurosurgery, Zhongnan Hospital of Wuhan University, 430071 Wuhan, China
- Brain Research Center, Zhongnan Hospital of Wuhan University, 430071 Wuhan, China
- Frontier Science Center for Immunology and Metabolism, Wuhan University, 430071 Wuhan, China
- Medical Research Institute, Wuhan University, 430071 Wuhan, China
- Sino-Italian Ascula Brain Science Joint Laboratory, Zhongnan Hospital of Wuhan University, 430071 Wuhan, China
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5
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Ashwood B, Jones MS, Lee Y, Sachleben JR, Ferguson AL, Tokmakoff A. Molecular insight into how the position of an abasic site and its sequence environment influence DNA duplex stability and dynamics. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.22.550182. [PMID: 37546925 PMCID: PMC10401965 DOI: 10.1101/2023.07.22.550182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/08/2023]
Abstract
Local perturbations to DNA base-pairing stability from lesions and chemical modifications can alter the stability and dynamics of an entire oligonucleotide. End effects may cause the position of a disruption within a short duplex to influence duplex stability and structural dynamics, yet this aspect of nucleic acid modifications is often overlooked. We investigate how the position of an abasic site (AP site) impacts the stability and dynamics of short DNA duplexes. Using a combination of steady-state and time-resolved spectroscopy and molecular dynamics simulations, we unravel an interplay between AP-site position and nucleobase sequence that controls energetic and dynamic disruption to the duplex. The duplex is disrupted into two segments by an entropic barrier for base pairing on each side of the AP site. The barrier induces fraying of the short segment when an AP site is near the termini. Shifting the AP site inward promotes a transition from short-segment fraying to fully encompassing the barrier into the thermodynamics of hybridization, leading to further destabilization the duplex. Nucleobase sequence determines the length scale for this transition by tuning the barrier height and base-pair stability of the short segment, and certain sequences enable out-of-register base pairing to minimize the barrier height.
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Affiliation(s)
- Brennan Ashwood
- Department of Chemistry, Institute for Biophysical Dynamics, and James Franck Institute, The University of Chicago, 929 East 57 Street, Chicago, Illinois 60637, United States
| | - Michael S. Jones
- Pritzker School of Molecular Engineering, The University of Chicago, 5640 South Ellis Avenue, Chicago, Illinois 60637, United States
| | - Yumin Lee
- Department of Chemistry, Institute for Biophysical Dynamics, and James Franck Institute, The University of Chicago, 929 East 57 Street, Chicago, Illinois 60637, United States
| | - Joseph R. Sachleben
- Biomolecular NMR Core Facility, Biological Sciences Division, The University of Chicago, Chicago, IL 60637, United States
| | - Andrew L. Ferguson
- Pritzker School of Molecular Engineering, The University of Chicago, 5640 South Ellis Avenue, Chicago, Illinois 60637, United States
| | - Andrei Tokmakoff
- Department of Chemistry, Institute for Biophysical Dynamics, and James Franck Institute, The University of Chicago, 929 East 57 Street, Chicago, Illinois 60637, United States
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6
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Meng W, Peng HC, Liu Y, Stelling A, Wang L. Modeling the Infrared Spectroscopy of Oligonucleotides with 13C Isotope Labels. J Phys Chem B 2023; 127:2351-2361. [PMID: 36898003 DOI: 10.1021/acs.jpcb.2c08915] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/12/2023]
Abstract
The carbonyl stretching modes have been widely used in linear and two-dimensional infrared (IR) spectroscopy to probe the conformation, interaction, and biological functions of nucleic acids. However, due to their universal appearance in nucleobases, the IR absorption bands of nucleic acids are often highly congested in the 1600-1800 cm-1 region. Following the fruitful applications in proteins, 13C isotope labels have been introduced to the IR measurements of oligonucleotides to reveal their site-specific structural fluctuations and hydrogen bonding conditions. In this work, we combine recently developed frequency and coupling maps to develop a theoretical strategy that models the IR spectra of oligonucleotides with 13C labels directly from molecular dynamics simulations. We apply the theoretical method to nucleoside 5'-monophosphates and DNA double helices and demonstrate how elements of the vibrational Hamiltonian determine the spectral features and their changes upon isotope labeling. Using the double helices as examples, we show that the calculated IR spectra are in good agreement with experiments and the 13C isotope labeling technique can potentially be applied to characterize the stacking configurations and secondary structures of nucleic acids.
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Affiliation(s)
- Wenting Meng
- Department of Chemistry and Chemical Biology, Institute for Quantitative Biomedicine, Rutgers University, Piscataway, New Jersey 08854, United States
| | - Hao-Che Peng
- Department of Chemistry and Biochemistry, The University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Yuanhao Liu
- Department of Statistics, Institute for Quantitative Biomedicine, Rutgers University, Piscataway, New Jersey 08854, United States
| | - Allison Stelling
- Department of Chemistry and Biochemistry, The University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Lu Wang
- Department of Chemistry and Chemical Biology, Institute for Quantitative Biomedicine, Rutgers University, Piscataway, New Jersey 08854, United States
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7
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Zhao XC, Dong HL, Li XL, Yang HY, Chen XF, Dai L, Wu WQ, Tan ZJ, Zhang XH. 5-Methyl-cytosine stabilizes DNA but hinders DNA hybridization revealed by magnetic tweezers and simulations. Nucleic Acids Res 2022; 50:12344-12354. [PMID: 36477372 PMCID: PMC9757033 DOI: 10.1093/nar/gkac1122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 10/31/2022] [Accepted: 11/07/2022] [Indexed: 12/12/2022] Open
Abstract
5-Methyl-cytosine (5mC) is one of the most important DNA modifications and plays versatile biological roles. It is well known that 5mC stabilizes DNA duplexes. However, it remains unclear how 5mC affects the kinetics of DNA melting and hybridization. Here, we studied the kinetics of unzipping and rezipping using a 502-bp DNA hairpin by single-molecule magnetic tweezers. Under constant loading rates, 5mC increases the unzipping force but counterintuitively decreases the rezipping force at various salt and temperature conditions. Under constant forces, the non-methylated DNA hops between metastable states during unzipping and rezipping, which implies low energy barriers. Surprisingly, the 5mC DNA can't rezip after fully unzipping unless much lower forces are applied, where it rezips stochastically in a one-step manner, which implies 5mC kinetically hinders DNA hybridization and high energy barriers in DNA hybridization. All-atom molecular dynamics simulations reveal that the 5mC kinetically hinders DNA hybridization due to steric effects rather than electrostatic effects caused by the additional methyl groups of cytosines. Considering the possible high speed of DNA unzipping and zipping during replication and transcription, our findings provide new insights into the biological roles of 5mC.
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Affiliation(s)
| | | | - Xiao-Lu Li
- The Institute for Advanced Studies, College of Life Sciences, State Key Laboratory of Virology, Hubei Key Laboratory of Cell Homeostasis, Wuhan University, Wuhan 430072, China
| | - Hong-Yu Yang
- The Institute for Advanced Studies, College of Life Sciences, State Key Laboratory of Virology, Hubei Key Laboratory of Cell Homeostasis, Wuhan University, Wuhan 430072, China
| | - Xue-Feng Chen
- The Institute for Advanced Studies, College of Life Sciences, State Key Laboratory of Virology, Hubei Key Laboratory of Cell Homeostasis, Wuhan University, Wuhan 430072, China
| | - Liang Dai
- Department of Physics, City University of Hong Kong, Hong Kong 999077, China
| | - Wen-Qiang Wu
- School of Life Sciences, State Key Laboratory of Crop Stress Adaptation and Improvement, Key Laboratory of Plant Stress Biology, Henan University, Kaifeng 475001, China
| | - Zhi-Jie Tan
- Correspondence may also be addressed to Zhi-Jie Tan. Tel: +86 15827627809; Fax: +86 02768752569;
| | - Xing-Hua Zhang
- To whom correspondence should be addressed. Tel: +86 15827632615; Fax: +86 02768753780;
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8
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Dubini RA, Korytiaková E, Schinkel T, Heinrichs P, Carell T, Rovó P. 1H NMR Chemical Exchange Techniques Reveal Local and Global Effects of Oxidized Cytosine Derivatives. ACS PHYSICAL CHEMISTRY AU 2022; 2:237-246. [PMID: 35637781 PMCID: PMC9137243 DOI: 10.1021/acsphyschemau.1c00050] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 01/25/2022] [Accepted: 01/26/2022] [Indexed: 11/29/2022]
Abstract
5-Carboxycytosine (5caC) is a rare epigenetic modification found in nucleic acids of all domains of life. Despite its sparse genomic abundance, 5caC is presumed to play essential regulatory roles in transcription, maintenance and base-excision processes in DNA. In this work, we utilize nuclear magnetic resonance (NMR) spectroscopy to address the effects of 5caC incorporation into canonical DNA strands at multiple pH and temperature conditions. Our results demonstrate that 5caC has a pH-dependent global destabilizing and a base-pair mobility enhancing local impact on dsDNA, albeit without any detectable influence on the ground-state B-DNA structure. Measurement of hybridization thermodynamics and kinetics of 5caC-bearing DNA duplexes highlighted how acidic environment (pH 5.8 and 4.7) destabilizes the double-stranded structure by ∼10-20 kJ mol-1 at 37 °C when compared to the same sample at neutral pH. Protonation of 5caC results in a lower activation energy for the dissociation process and a higher barrier for annealing. Studies on conformational exchange on the microsecond time scale regime revealed a sharply localized base-pair motion involving exclusively the modified site and its immediate surroundings. By direct comparison with canonical and 5-formylcytosine (5fC)-edited strands, we were able to address the impact of the two most oxidized naturally occurring cytosine derivatives in the genome. These insights on 5caC's subtle sensitivity to acidic pH contribute to the long-standing questions of its capacity as a substrate in base excision repair processes and its purpose as an independent, stable epigenetic mark.
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Affiliation(s)
- Romeo
C. A. Dubini
- Faculty
of Chemistry and Pharmacy, Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstraße 5-13, 81377 Munich, Germany
- Center
for Nanoscience (CeNS), Faculty of Physics, Ludwig-Maximilians-Universität München, Schellingstraße 4, 5th floor, 80799 Munich, Germany
| | - Eva Korytiaková
- Faculty
of Chemistry and Pharmacy, Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstraße 5-13, 81377 Munich, Germany
| | - Thea Schinkel
- Faculty
of Chemistry and Pharmacy, Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstraße 5-13, 81377 Munich, Germany
| | - Pia Heinrichs
- Faculty
of Chemistry and Pharmacy, Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstraße 5-13, 81377 Munich, Germany
| | - Thomas Carell
- Faculty
of Chemistry and Pharmacy, Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstraße 5-13, 81377 Munich, Germany
| | - Petra Rovó
- Faculty
of Chemistry and Pharmacy, Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstraße 5-13, 81377 Munich, Germany
- Center
for Nanoscience (CeNS), Faculty of Physics, Ludwig-Maximilians-Universität München, Schellingstraße 4, 5th floor, 80799 Munich, Germany
- Institute
of Science and Technology Austria (ISTA), Am Campus 1, 3400 Klosterneuburg, Austria
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9
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Interaction of Thymine DNA Glycosylase with Oxidised 5-Methyl-cytosines in Their Amino- and Imino-Forms. Molecules 2021; 26:molecules26195728. [PMID: 34641273 PMCID: PMC8510025 DOI: 10.3390/molecules26195728] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 09/03/2021] [Accepted: 09/13/2021] [Indexed: 11/16/2022] Open
Abstract
Thymine DNA Glycosylase (TDG) is an enzyme of the base excision repair mechanism and removes damaged or mispaired bases from DNA via hydrolysis of the glycosidic bond. Specificity is of high importance for such a glycosylase, so as to avoid the damage of intact DNA. Among the substrates reported for TDG are mispaired uracil and thymine but also formyl-cytosine and carboxyl-cytosine. Methyl-cytosine and hydroxylmethyl-cytosine are, in contrast, not processed by the TDG enzyme. We have in this work employed molecular dynamics simulations to explore the conformational dynamics of DNA carrying a formyl-cytosine or carboxyl-cytosine and compared those to DNA with the non-cognate bases methyl-cytosine and hydroxylmethyl-cytosine, as amino and imino tautomers. Whereas for the mispairs a wobble conformation is likely decisive for recognition, all amino tautomers of formyl-cytosine and carboxyl-cytosine exhibit the same Watson–Crick conformation, but all imino tautomers indeed form wobble pairs. The conformational dynamics of the amino tautomers in free DNA do not exhibit differences that could be exploited for recognition, and also complexation to the TDG enzyme does not induce any alteration that would indicate preferable binding to one or the other oxidised methyl-cytosine. The imino tautomers, in contrast, undergo a shift in the equilibrium between a closed and a more open, partially flipped state, towards the more open form upon complexation to the TDG enzyme. This stabilisation of the more open conformation is most pronounced for the non-cognate bases methyl-cytosine and hydroxyl-cytosine and is thus not a likely mode for recognition. Moreover, calculated binding affinities for the different forms indicate the imino forms to be less likely in the complexed DNA. These findings, together with the low probability of imino tautomers in free DNA and the indifference of the complexed amino tautomers, suggest that discrimination of the oxidised methyl-cytosines does not take place in the initial complex formation.
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10
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Wong KL, Liu J. Factors and methods to modulate DNA hybridization kinetics. Biotechnol J 2021; 16:e2000338. [PMID: 34411451 DOI: 10.1002/biot.202000338] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 08/11/2021] [Accepted: 08/12/2021] [Indexed: 11/09/2022]
Abstract
DNA oligonucleotides are widely used in a diverse range of research fields from analytical chemistry, molecular biology, nanotechnology to drug delivery. In these applications, DNA hybridization is often the most important enabling reaction. Achieving control over hybridization kinetics and a high yield of hybridized products is needed to ensure high-quality and reproducible results. Since DNA strands are highly negatively charged and can also fold upon itself to form various intramolecular structures, DNA hybridization needs to overcome these barriers. Nucleation and diffusion are two main kinetic limiting steps although their relative importance differs in different conditions. The effects of length and sequence, temperature, pH, salt concentration, cationic polymers, organic solvents, freezing and crowding agents are summarized in the context of overcoming these barriers. This article will help researchers in the biotechnology-related fields to better understand and control DNA hybridization, as well as provide a landscape for future work in simulation and experiment to optimize DNA hybridization systems.
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Affiliation(s)
- Kingsley L Wong
- Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario, Canada
| | - Juewen Liu
- Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario, Canada
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11
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Dale J, Howe CP, Toncrova H, Fritzsch R, Greetham GM, Clark IP, Towrie M, Parker AW, McLeish TC, Hunt NT. Combining steady state and temperature jump IR spectroscopy to investigate the allosteric effects of ligand binding to dsDNA. Phys Chem Chem Phys 2021; 23:15352-15363. [PMID: 34254612 DOI: 10.1039/d1cp02233d] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Changes in the structural dynamics of double stranded (ds)DNA upon ligand binding have been linked to the mechanism of allostery without conformational change, but direct experimental evidence remains elusive. To address this, a combination of steady state infrared (IR) absorption spectroscopy and ultrafast temperature jump IR absorption measurements has been used to quantify the extent of fast (∼100 ns) fluctuations in (ds)DNA·Hoechst 33258 complexes at a range of temperatures. Exploiting the direct link between vibrational band intensities and base stacking shows that the absolute magnitude of the change in absorbance caused by fast structural fluctuations following the temperature jump is only weakly dependent on the starting temperature of the sample. The observed fast dynamics are some two orders of magnitude faster than strand separation and associated with all points along the 10-base pair duplex d(GCATATATCC). Binding the Hoechst 33258 ligand causes a small but consistent reduction in the extent of these fast fluctuations of base pairs located outside of the ligand binding region. These observations point to a ligand-induced reduction in the flexibility of the dsDNA near the binding site, consistent with an estimated allosteric propagation length of 15 Å, about 5 base pairs, which agrees well with both molecular simulation and coarse-grained statistical mechanics models of allostery leading to cooperative ligand binding.
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Affiliation(s)
- Jessica Dale
- Department of Chemistry and York Biomedical Research Institute, University of York, Heslington, York YO10 5DD, UK.
| | - C Peter Howe
- Department of Chemistry and York Biomedical Research Institute, University of York, Heslington, York YO10 5DD, UK.
| | - Hedvika Toncrova
- Department of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, UK
| | - Robby Fritzsch
- Department of Physics, SUPA, University of Strathclyde, Glasgow, G4 0NG, UK
| | - Gregory M Greetham
- STFC Central Laser Facility, Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell Campus, Didcot, OX11 0QX, UK
| | - Ian P Clark
- STFC Central Laser Facility, Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell Campus, Didcot, OX11 0QX, UK
| | - Michael Towrie
- STFC Central Laser Facility, Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell Campus, Didcot, OX11 0QX, UK
| | - Anthony W Parker
- STFC Central Laser Facility, Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell Campus, Didcot, OX11 0QX, UK
| | - Thomas C McLeish
- Department of Physics, University of York, Heslington, York YO10 5DD, UK.
| | - Neil T Hunt
- Department of Chemistry and York Biomedical Research Institute, University of York, Heslington, York YO10 5DD, UK.
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12
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Ashwood B, Lewis NHC, Sanstead PJ, Tokmakoff A. Temperature-Jump 2D IR Spectroscopy with Intensity-Modulated CW Optical Heating. J Phys Chem B 2020; 124:8665-8677. [PMID: 32902979 DOI: 10.1021/acs.jpcb.0c07177] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Pulsed temperature-jump (T-jump) spectroscopy with infrared (IR) detection has been widely used to study biophysical processes occurring from nanoseconds to ∼1 ms with structural sensitivity. However, many systems exhibit structural dynamics on time scales longer than the millisecond barrier that is set by the time scale for thermal relaxation of the sample. We developed a linear and nonlinear infrared spectrometer coupled to an intensity-modulated continuous wave (CW) laser to probe T-jump-initiated chemical reactions from <1 ms to seconds. Time-dependent modulation of the CW laser leads to a <1 ms heating time as well as a constant final temperature (±3%) for the duration of the heating time. Temperature changes of up to 75 °C in D2O are demonstrated, allowing for nonequilibrium measurements inaccessible to standard pulsed optical T-jump setups. T-jump linear absorption, pump-probe, and two-dimensional IR (2D IR) spectroscopy are applied to the unfolding and refolding of ubiquitin and a model intercalated motif (i-motif) DNA sequence, and analysis of the observed signals is used to demonstrate the limits and utility of each method. Overall, the ability to probe temperature-induced chemical processes from <1 ms to many seconds with 2D IR spectroscopy provides multiple new avenues for time-dependent spectroscopy in chemistry and biophysics.
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Affiliation(s)
- Brennan Ashwood
- Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Nicholas H C Lewis
- Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Paul J Sanstead
- Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Andrei Tokmakoff
- Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
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13
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Dubini RCA, Schön A, Müller M, Carell T, Rovó P. Impact of 5-formylcytosine on the melting kinetics of DNA by 1H NMR chemical exchange. Nucleic Acids Res 2020; 48:8796-8807. [PMID: 32652019 PMCID: PMC7470965 DOI: 10.1093/nar/gkaa589] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2020] [Revised: 06/24/2020] [Accepted: 07/02/2020] [Indexed: 12/23/2022] Open
Abstract
5-Formylcytosine (5fC) is a chemically edited, naturally occurring nucleobase which appears in the context of modified DNA strands. The understanding of the impact of 5fC on dsDNA physical properties is to date limited. In this work, we applied temperature-dependent 1H Chemical Exchange Saturation Transfer (CEST) NMR experiments to non-invasively and site-specifically measure the thermodynamic and kinetic influence of formylated cytosine nucleobase on the melting process involving dsDNA. Incorporation of 5fC within symmetrically positioned CpG sites destabilizes the whole dsDNA structure-as witnessed from the ∼2°C decrease in the melting temperature and 5-10 kJ mol-1 decrease in ΔG°-and affects the kinetic rates of association and dissociation. We observed an up to ∼5-fold enhancement of the dsDNA dissociation and an up to ∼3-fold reduction in ssDNA association rate constants, over multiple temperatures and for several proton reporters. Eyring and van't Hoff analysis proved that the destabilization is not localized, instead all base-pairs are affected and the transition states resembles the single-stranded conformation. These results advance our knowledge about the role of 5fC as a semi-permanent epigenetic modification and assist in the understanding of its interactions with reader proteins.
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Affiliation(s)
- Romeo C A Dubini
- Faculty of Chemistry and Pharmacy, Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstraße 5-13, 81377 Munich, Germany
- Center for Nanoscience (CeNS), Faculty of Physics, Ludwig-Maximilians-Universität München, Schellingstraße 4, 80799 Munich, Germany
| | - Alexander Schön
- Faculty of Chemistry and Pharmacy, Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstraße 5-13, 81377 Munich, Germany
| | - Markus Müller
- Faculty of Chemistry and Pharmacy, Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstraße 5-13, 81377 Munich, Germany
| | - Thomas Carell
- Faculty of Chemistry and Pharmacy, Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstraße 5-13, 81377 Munich, Germany
| | - Petra Rovó
- Faculty of Chemistry and Pharmacy, Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstraße 5-13, 81377 Munich, Germany
- Center for Nanoscience (CeNS), Faculty of Physics, Ludwig-Maximilians-Universität München, Schellingstraße 4, 80799 Munich, Germany
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14
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Ashwood B, Sanstead PJ, Dai Q, He C, Tokmakoff A. 5-Carboxylcytosine and Cytosine Protonation Distinctly Alter the Stability and Dehybridization Dynamics of the DNA Duplex. J Phys Chem B 2020; 124:627-640. [PMID: 31873021 DOI: 10.1021/acs.jpcb.9b11510] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Applications associated with nucleobase protonation events are grounded in their fundamental impact on DNA thermodynamics, structure, and hybridization dynamics. Of the canonical nucleobases, N3 protonation of cytosine (C) is the most widely utilized in both biology and nanotechnology. Naturally occurring C derivatives that shift the N3 pKa introduce an additional level of tunability. The epigenetic nucleobase 5-carboxylcytosine (caC) presents a particularly interesting example since this derivative forms Watson-Crick base pairs of similar stability and displays pH-dependent behavior over the same range as the canonical nucleobase. However, the titratable group in caC corresponds to the exocyclic carboxyl group rather than N3, and the implications of these divergent protonation events toward DNA hybridization thermodynamics, kinetics, and base pairing dynamics remain poorly understood. Here, we study the pH dependence of these physical properties using model oligonucleotides containing C and caC with FTIR and temperature-jump IR spectroscopy. We demonstrate that N3 protonation of C completely disrupts duplex stability, leading to large shifts in the duplex/single-strand equilibrium, a reduction in the cooperativity of melting, and an acceleration in the rate of duplex dissociation. In contrast, while increasing 5-carboxyl protonation in caC-containing duplexes induces an increase in base pair fluctuations, the DNA duplex can tolerate substantial protonation without significant perturbation to the duplex/single-strand equilibrium. However, 5-carboxyl protonation has a large impact on hybridization kinetics by reducing the transition state free energy. Our thermodynamic and kinetic analysis provides new insight on the impact of two divergent protonation mechanisms in naturally occurring nucleobases on the biophysical properties of DNA.
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