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Kim H, Pak Y. Isomerization Pathways of a Mismatched Base Pair of A:8OG in Free Duplex DNA. J Chem Inf Model 2024; 64:4511-4517. [PMID: 38767002 DOI: 10.1021/acs.jcim.4c00563] [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: 05/22/2024]
Abstract
The A:8OG base pair (bp) is the outcome of DNA replication of the mismatched C:8OG bp. A high A:8OG bp population increases the C/G to A/T transversion mutation, which is responsible for various diseases. MutY is an important enzyme in the error-proof cycle and reverts A:8OG to C:8OG bp by cleaving adenine from the A:8OG bp. Several X-ray crystallography studies have determined the structure of MutY during the lesion scanning and lesion recognition stages. Interestingly, glycosidic bond (χ) angles of A:8OG bp in those two lesion recognition structures were found to differ, which implies that χ-torsion isomerization should occur during the lesion recognition process. In this study, as a first step to understanding this isomerization process, we characterized the intrinsic dynamic features of A:8OG in free DNAs by a free energy landscape simulation at the all-atom level. In this study, four isomerization states were assigned in the order of abundance: Aanti:8OGsyn > Aanti:8OGanti > Asyn:8OGanti ≈ Asyn:8OGsyn. Of these bp states, only 8OG in Asyn:8OGanti was located in the extrahelical space, whereas the purine bases (A and 8OG) in the other bp states remained inside the DNA helix. Also, free energy landscapes showed that the isomerization processes connecting these four bp states proceeded mostly in the intrahelical space via successive single glycosidic bond rotations of either A or 8OG.
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Affiliation(s)
- Hyeonjun Kim
- Department of Chemistry and Institute of Functional Materials, Pusan National University, Busan 46241, South Korea
| | - Youngshang Pak
- Department of Chemistry and Institute of Functional Materials, Pusan National University, Busan 46241, South Korea
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2
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Maurer J, Albrecht CS, Herbert P, Heussman D, Chang A, von Hippel PH, Marcus AH. Studies of DNA 'Breathing' by Polarization-Sweep Single-Molecule Fluorescence Microscopy of Exciton-Coupled (iCy3) 2 Dimer-Labeled DNA Fork Constructs. J Phys Chem B 2023; 127:10730-10748. [PMID: 38060691 PMCID: PMC10754251 DOI: 10.1021/acs.jpcb.3c06463] [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] [Indexed: 12/22/2023]
Abstract
Local fluctuations of the sugar-phosphate backbones and bases of DNA (often called DNA 'breathing') play a variety of critical roles in controlling the functional interactions of the DNA genome with the protein complexes that regulate it. Here, we present a single-molecule fluorescence method that we have used to measure and characterize such conformational fluctuations at and near biologically important positions in model DNA replication fork constructs labeled with exciton-coupled cyanine [(iCy3)2] dimer probes. Previous work has shown that the constructs that we tested here exhibit a broad range of spectral properties at the ensemble level, and these differences can be structurally and dynamically interpreted using our present methodology at the single-molecule level. The (iCy3)2 dimer has one symmetric (+) and one antisymmetric (-) exciton, with the respective transition dipole moments oriented perpendicular to one another. We excite single-molecule samples using a continuous-wave linearly polarized laser, with the polarization direction continuously rotated at the frequency of 1 MHz. The ensuing fluorescence signal is modulated as the laser polarization alternately excites the symmetric and antisymmetric excitons of the (iCy3)2 dimer probe. Phase-sensitive detection of the modulated signal provides information about the distribution of local conformations and the conformational interconversion dynamics of the (iCy3)2 probe. We find that at most construct positions that we examined, the (iCy3)2 dimer-labeled DNA fork constructs can adopt four topologically distinct conformational macrostates. These results suggest that in addition to observing DNA breathing at and near ss-dsDNA junctions, our new methodology should be useful to determine which of these pre-existing macrostates are recognized by, bind to, and are stabilized by various genome-regulatory proteins.
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Affiliation(s)
- Jack Maurer
- Center for Optical, Molecular and Quantum Science, University of Oregon, Eugene, Oregon 97403
- Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403
| | - Claire S. Albrecht
- Center for Optical, Molecular and Quantum Science, University of Oregon, Eugene, Oregon 97403
- Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403
- Department of Physics, University of Oregon, Eugene, Oregon 97403
| | - Patrick Herbert
- Center for Optical, Molecular and Quantum Science, University of Oregon, Eugene, Oregon 97403
- Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403
| | - Dylan Heussman
- Center for Optical, Molecular and Quantum Science, University of Oregon, Eugene, Oregon 97403
- Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403
| | - Anabel Chang
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403
| | - Peter H. von Hippel
- Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403
| | - Andrew H. Marcus
- Center for Optical, Molecular and Quantum Science, University of Oregon, Eugene, Oregon 97403
- Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403
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3
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Kole K, Gupta AM, Chakrabarti J. Conformational stability and order of Hoogsteen base pair induced by protein binding. Biophys Chem 2023; 301:107079. [PMID: 37523944 DOI: 10.1016/j.bpc.2023.107079] [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] [Received: 05/19/2023] [Revised: 07/18/2023] [Accepted: 07/24/2023] [Indexed: 08/02/2023]
Abstract
Several experimental studies have shown that Hoogsteen (HG) base pair (bp) stabilizes in the presence of proteins. The molecular mechanism underlying this stabilization is not well known. This leads us to examine the stability of the HG bp in duplex DNA using all-atom molecular dynamics simulation in both the absence and presence of proteins. We use conformational thermodynamics to investigate the stability of a HG bp in duplex DNA at the molecular level. We compute the changes in the conformational free energy and entropy of DNA when DNA adopts a HG bp in its bp sequence rather than a Watson-Crick (WC) bp in both naked DNA and protein-bound DNA complex. We observe that the presence of proteins stabilizes and organizes the HG bp and the entire DNA duplex. Sugar-phosphate, sugar-base, and sugar-pucker torsion angles play key roles in stabilizing and ordering the HG bp in the protein-bound DNA complex.
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Affiliation(s)
- Kanika Kole
- Department of Physics of Complex Systems, S. N. Bose National Centre for Basic Sciences, Block-JD, Sector-III, Salt Lake, Kolkata 700106, India
| | - Aayatti Mallick Gupta
- Department of Physics of Complex Systems, S. N. Bose National Centre for Basic Sciences, Block-JD, Sector-III, Salt Lake, Kolkata 700106, India.
| | - Jaydeb Chakrabarti
- Department of Physics of Complex Systems, S. N. Bose National Centre for Basic Sciences, Block-JD, Sector-III, Salt Lake, Kolkata 700106, India.
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4
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Stone S, Ray D, Andricioaei I. Force-Field-Dependent DNA Breathing Dynamics: A Case Study of Hoogsteen Base Pairing in A6-DNA. J Chem Inf Model 2022; 62:6749-6761. [PMID: 36049242 PMCID: PMC9795553 DOI: 10.1021/acs.jcim.2c00519] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The Hoogsteen (HG) base pairing conformation, commonly observed in damaged and mutated DNA helices, facilitates DNA repair and DNA recognition. The free energy difference between HG and Watson-Crick (WC) base pairs has been computed in previous studies. However, the mechanism of the conformational transition is not well understood. A detailed understanding of the process of WC to HG base pair transition can provide a deeper understanding of DNA repair and recognition. In an earlier study, we explored the free energy landscape for this process using extensive computer simulation with the CHARMM36 force field. In this work, we study the impact of force field models in describing the WC to HG base pairing transition using meta-eABF enhanced sampling, quasi-harmonic entropy calculation, and nonbonded energy analysis. The secondary structures of both base pairing forms and the topology of the free energy landscapes were consistent over different force field models, although the relative free energy, entropy, and the interaction energies tend to vary. The relative stability of the WC and HG conformations is dictated by a delicate balance between the enthalpic stabilization and the reduced entropy of the structurally rigid HG structure. These findings highlight the impact that subtleties in force field models can have on accurately modeling DNA base pair dynamics and should stimulate further computational investigations into other dynamically important motions in DNA.
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Affiliation(s)
- Sharon
Emily Stone
- Department
of Chemistry, University of California Irvine, Irvine, California 92697, United States
| | - Dhiman Ray
- Department
of Chemistry, University of California Irvine, Irvine, California 92697, United States
| | - Ioan Andricioaei
- Department
of Chemistry, University of California Irvine, Irvine, California 92697, United States,Department
of Physics and Astronomy, University of
California Irvine, Irvine, California 92697, United States,
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5
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Sequence dependence of transient Hoogsteen base pairing in DNA. PLoS Comput Biol 2022; 18:e1010113. [PMID: 35617357 PMCID: PMC9177043 DOI: 10.1371/journal.pcbi.1010113] [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: 11/16/2021] [Revised: 06/08/2022] [Accepted: 04/19/2022] [Indexed: 11/19/2022] Open
Abstract
Hoogsteen (HG) base pairing is characterized by a 180° rotation of the purine base with respect to the Watson-Crick-Franklin (WCF) motif. Recently, it has been found that both conformations coexist in a dynamical equilibrium and that several biological functions require HG pairs. This relevance has motivated experimental and computational investigations of the base-pairing transition. However, a systematic simulation of sequence variations has remained out of reach. Here, we employ advanced path-based methods to perform unprecedented free-energy calculations. Our methodology enables us to study the different mechanisms of purine rotation, either remaining inside or after flipping outside of the double helix. We study seven different sequences, which are neighbor variations of a well-studied A⋅T pair in A6-DNA. We observe the known effect of A⋅T steps favoring HG stability, and find evidence of triple-hydrogen-bonded neighbors hindering the inside transition. More importantly, we identify a dominant factor: the direction of the A rotation, with the 6-ring pointing either towards the longer or shorter segment of the chain, respectively relating to a lower or higher barrier. This highlights the role of DNA’s relative flexibility as a modulator of the WCF/HG dynamic equilibrium. Additionally, we provide a robust methodology for future HG proclivity studies. Recently, an alternative DNA base-pairing conformation, known as Hoogsteen (HG), has been found to coexist with the well-known Watson-Crick-Franklin (WCF) pairing. Several experimental and computational studies have focused on this heterogeneity, as it is involved in various recognition and replication processes. The WCF-to-HG transition mechanisms consist of a ±180° rotation of the purine base, occurring either inside of the double helix or while flipping temporarily outside of it. Even though molecular dynamics simulations can provide fine details about the transition pathways and their free-energy barriers, the computational cost has limited most studies to focus on only one particular chain (A6-DNA). Here, we investigate the sequence dependence of the base-pairing transition, by systematically varying the direct neighbors of a transitioning A⋅T pair; probing inside and outside pathways in seven distinct systems. We discover that triple-hydrogen-bonded neighboring base-pairs hinder the inside rotation mechanism, due to the reduced flexibility needed for internal base rotation. Across all sequences, we confirm that outside transitions have a lower free-energy barrier. Most importantly, we observe that the direction of the A rotation, with the A 6-ring pointing either towards the long or short end of the modelled DNA chain, has a determinant effect on the height of the free-energy barrier. These results point to a critical role of DNA’s small- and medium-scale flexibility in modulating the proclivity of HG base pairs; providing a handle that might be employed by several biological mechanisms.
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Kim H, Yang C, Pak Y. Free-Energy Landscape of a pH-Modulated G·C Base Pair Transition from Watson-Crick to Hoogsteen State in Duplex DNA. J Chem Theory Comput 2021; 17:2556-2565. [PMID: 33689343 DOI: 10.1021/acs.jctc.0c01330] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In double-helical DNAs, the most stable Watson-Crick (WC) base pair (bp) can be in thermal equilibrium with much less abundant Hoogsteen (HG) bp by the spontaneous rotation of the glycosidic angle in purine bases. Previous experimental studies showed that in the case of a G·C bp, the population of the transient HG is enhanced as a protonated form (HG+) through the protonation of the cytosine base under weakly acidic conditions. Hence, pH is a key factor that can modulate this transition event from the WC to HG+ bp. In this study, to computationally probe the overall free-energy landscapes of this pH-modulated G·C HG breathing, a comprehensive classical molecular dynamics (MD) simulation protocol is proposed using an enhanced sampling MD in conjunction with the standard thermodynamic integration method. From this MD protocol proposed, the free-energy surfaces of the G·C bp transition from the WC to HG bp were constructed successfully at any pH range, producing pH-dependent free-energy quantities in close agreement with previously reported experimental results. The simulation protocol is expected to provide valuable atomistic insight into the DNA bp transition events coupled with protonation or tautomeric shift in a target bp.
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Affiliation(s)
- Hyeonjun Kim
- Department of Chemistry and Institute of Functional Materials, Pusan National University, Busandaehak-ro 63beon-gil, Geumjeong-gu, Busan 46241, South Korea
| | - Changwon Yang
- Department of Chemistry, Sejong University, 209, Neungdong-ro, Gwangjin-gu, Seoul 05006, South Korea
| | - Youngshang Pak
- Department of Chemistry and Institute of Functional Materials, Pusan National University, Busandaehak-ro 63beon-gil, Geumjeong-gu, Busan 46241, South Korea
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Wan L, Lam SL, Lee HK, Guo P. Effects of Adenine Methylation on the Structure and Thermodynamic Stability of a DNA Minidumbbell. Int J Mol Sci 2021; 22:3633. [PMID: 33807305 PMCID: PMC8037738 DOI: 10.3390/ijms22073633] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Revised: 03/24/2021] [Accepted: 03/25/2021] [Indexed: 11/17/2022] Open
Abstract
DNA methylation is a prevalent regulatory modification in prokaryotes and eukaryotes. N1-methyladenine (m1A) and N6-methyladenine (m6A) have been found to be capable of altering DNA structures via disturbing Watson-Crick base pairing. However, little has been known about their influences on non-B DNA structures, which are associated with genetic instabilities. In this work, we investigated the effects of m1A and m6A on both the structure and thermodynamic stability of a newly reported DNA minidumbbell formed by two TTTA tetranucleotide repeats. As revealed by the results of nuclear magnetic resonance spectroscopic studies, both m1A and m6A favored the formation of a T·m1A and T·m6A Hoogsteen base pair, respectively. More intriguingly, the m1A and m6A modifications brought about stabilization and destabilization effects on the DNA minidumbbell, respectively. This work provides new biophysical insights into the effects of adenine methylation on the structure and thermodynamic stability of DNA.
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Affiliation(s)
- Liqi Wan
- MOE International Joint Research Laboratory on Synthetic Biology and Medicines, School of Biology and Biological Engineering, South China University of Technology, Guangzhou 510006, China;
- Department of Chemistry, The Chinese University of Hong Kong, Hong Kong SAR 999077, China;
| | - Sik Lok Lam
- Department of Chemistry, The Chinese University of Hong Kong, Hong Kong SAR 999077, China;
| | - Hung Kay Lee
- Department of Chemistry, The Chinese University of Hong Kong, Hong Kong SAR 999077, China;
| | - Pei Guo
- MOE International Joint Research Laboratory on Synthetic Biology and Medicines, School of Biology and Biological Engineering, South China University of Technology, Guangzhou 510006, China;
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Ray D, Andricioaei I. Free Energy Landscape and Conformational Kinetics of Hoogsteen Base Pairing in DNA vs. RNA. Biophys J 2020; 119:1568-1579. [PMID: 32946766 DOI: 10.1016/j.bpj.2020.08.031] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Revised: 05/10/2020] [Accepted: 08/25/2020] [Indexed: 10/23/2022] Open
Abstract
Genetic information is encoded in the DNA double helix, which, in its physiological milieu, is characterized by the iconical Watson-Crick nucleo-base pairing. Recent NMR relaxation experiments revealed the transient presence of an alternative, Hoogsteen (HG) base pairing pattern in naked DNA duplexes, and estimated its relative stability and lifetime. In contrast with DNA, such structures were not observed in RNA duplexes. Understanding HG base pairing is important because the underlying "breathing" motion between the two conformations can significantly modulate protein binding. However, a detailed mechanistic insight into the transition pathways and kinetics is still missing. We performed enhanced sampling simulation (with combined metadynamics and adaptive force-bias method) and Markov state modeling to obtain accurate free energy, kinetics, and the intermediates in the transition pathway between Watson-Crick and HG base pairs for both naked B-DNA and A-RNA duplexes. The Markov state model constructed from our unbiased MD simulation data revealed previously unknown complex extrahelical intermediates in the seemingly simple process of base flipping in B-DNA. Extending our calculation to A-RNA, for which HG base pairing is not observed experimentally, resulted in relatively unstable, single-hydrogen-bonded, distorted Hoogsteen-like bases. Unlike B-DNA, the transition pathway primarily involved base paired and intrahelical intermediates with transition timescales much longer than that of B-DNA. The seemingly obvious flip-over reaction coordinate (i.e., the glycosidic torsion angle) is unable to resolve the intermediates. Instead, a multidimensional picture involving backbone dihedral angles and distance between hydrogen bond donor and acceptor atoms is required to gain insight into the molecular mechanism.
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Affiliation(s)
| | - Ioan Andricioaei
- Department of Chemistry; Department of Physics and Astronomy, University of California Irvine, Irvine, California.
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Kim H, Pak Y. Balancing All‐Atom Force Field for
DNA
Simulations Using Osmotic Pressure Data. B KOREAN CHEM SOC 2020. [DOI: 10.1002/bkcs.12065] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Hyeonjun Kim
- Department of Chemistry and Institute of Functional MaterialsPusan National University Busan 46241 South Korea
| | - Youngshang Pak
- Department of Chemistry and Institute of Functional MaterialsPusan National University Busan 46241 South Korea
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10
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Khoshbin Z, Housaindokht MR, Izadyar M, Bozorgmehr MR, Verdian A. Temperature and molecular crowding effects on the sensitivity of T30695 aptamer toward Pb2+ion: a joint molecular dynamics simulation and experimental study. MOLECULAR SIMULATION 2020. [DOI: 10.1080/08927022.2020.1751842] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Zahra Khoshbin
- Department of Chemistry, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran
| | | | - Mohammad Izadyar
- Department of Chemistry, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran
| | | | - Asma Verdian
- Department of Food Safety and Quality Control, Research Institute of Food Science and Technology (RIFST), Mashhad, Iran
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11
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Theoretical design and experimental study of new aptamers with the improved target-affinity: New insights into the Pb2+-specific aptamers as a case study. J Mol Liq 2019. [DOI: 10.1016/j.molliq.2019.111159] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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