51
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Shao Q, Zhu W. How Well Can Implicit Solvent Simulations Explore Folding Pathways? A Quantitative Analysis of α-Helix Bundle Proteins. J Chem Theory Comput 2017; 13:6177-6190. [DOI: 10.1021/acs.jctc.7b00726] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Qiang Shao
- Drug
Discovery and Design Center, CAS Key Laboratory of Receptor Research,
Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China
- University of
Chinese Academy of Sciences, Beijing 100049, China
| | - Weiliang Zhu
- Drug
Discovery and Design Center, CAS Key Laboratory of Receptor Research,
Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai 201203, China
- University of
Chinese Academy of Sciences, Beijing 100049, China
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52
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Yuan Y, Zhao Y, Chen L, Wu J, Chen G, Li S, Zou J, Chen R, Wang J, Jiang F, Tang Z. Selective tumor cell death induced by irradiated riboflavin through recognizing DNA G-T mismatch. Nucleic Acids Res 2017; 45:8676-8683. [PMID: 28911109 PMCID: PMC5587794 DOI: 10.1093/nar/gkx602] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2017] [Accepted: 07/04/2017] [Indexed: 12/04/2022] Open
Abstract
Riboflavin (vitamin B2) has been thought to be a promising antitumoral agent in photodynamic therapy, though the further application of the method was limited by the unclear molecular mechanism. Our work reveals that riboflavin was able to recognize G–T mismatch specifically and induce single-strand breaks in duplex DNA targets efficiently under irradiation. In the presence of riboflavin, the photo-irradiation could induce the death of tumor cells that are defective in mismatch repair system selectively, highlighting the G–T mismatch as potential drug target for tumor cells. Moreover, riboflavin is a promising leading compound for further drug design due to its inherent specific recognition of the G–T mismatch.
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Affiliation(s)
- Yi Yuan
- Natural Products Research Center, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, PR China.,College of pharmacy, Chengdu University of Traditional Chinese Medicine, Chengdu 611137, PR China
| | - Yongyun Zhao
- Natural Products Research Center, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, PR China
| | - Lianqi Chen
- Natural Products Research Center, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, PR China
| | - Jiasi Wu
- College of pharmacy, Chengdu University of Traditional Chinese Medicine, Chengdu 611137, PR China
| | - Gangyi Chen
- Natural Products Research Center, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, PR China
| | - Sheng Li
- Natural Products Research Center, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, PR China
| | - Jiawei Zou
- Natural Products Research Center, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, PR China
| | - Rong Chen
- Natural Products Research Center, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, PR China
| | - Jian Wang
- College of pharmacy, Chengdu University of Traditional Chinese Medicine, Chengdu 611137, PR China
| | - Fan Jiang
- Laboratory of Computational Chemistry and Drug Design, Laboratory of Chemical Genomics, Peking University Shenzhen Graduate School, Shenzhen 518055, PR China
| | - Zhuo Tang
- Natural Products Research Center, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, PR China
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53
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Shweta H, Singh MK, Yadav K, Verma SD, Pal N, Sen S. Effect of T·T Mismatch on DNA Dynamics Probed by Minor Groove Binders: Comparison of Dynamic Stokes Shifts of Hoechst and DAPI. J Phys Chem B 2017; 121:10735-10748. [PMID: 28922599 DOI: 10.1021/acs.jpcb.7b06937] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Recognition of DNA base mismatches and their subsequent repair by enzymes is vital for genomic stability. However, it is difficult to comprehend such a process in which enzymes sense and repair different types of mismatches with different ability. It has been suggested that the differential structural changes of mismatched bases act as cues to the repair enzymes, although the effect of such DNA structural changes on surrounding water and ion dynamics is inevitable due to strong electrostatic coupling among them. Thus, collective dynamics of DNA, water, and ions near the mismatch site is believed to be important for mismatch recognition and repair mechanism. Here we show that introduction of a T·T mismatch in the minor groove of DNA induces dispersed (collective) power-law solvation dynamics (of exponent ∼0.24), measured by monitoring the time-resolved fluorescence Stokes shifts (TRFSS) of two popular minor groove binders (Hoechst 33258 and DAPI) over five decades of time from 100 fs to 10 ns. The same ligands however sense different dynamics (power-law of exponent ∼0.15 or power-law multiplied with biexponential relaxation) in the minor groove of normal-DNA. The similar fluorescence anisotropy decays of ligands measured in normal- and T·T-DNA suggest that Stokes shift dynamics and their changes in T·T-DNA purely originate from the solvation process, and not from any internal rotational motion of probe-ligands. The dispersed power-law solvation dynamics seen in T·T-DNA indicate that the ligands do not sense any particular (exponential) relaxation specific to T·T wobbling and/or other conformational changes. This could be the reason why T·T mismatch is recognized by enzymes with lower efficiency compared to purine-pyrimidine and purine-purine mismatches.
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Affiliation(s)
- Him Shweta
- Spectroscopy Laboratory, School of Physical Sciences, Jawaharlal Nehru University , New Delhi 110067, India
| | - Moirangthem Kiran Singh
- Spectroscopy Laboratory, School of Physical Sciences, Jawaharlal Nehru University , New Delhi 110067, India
| | - Kavita Yadav
- Spectroscopy Laboratory, School of Physical Sciences, Jawaharlal Nehru University , New Delhi 110067, India
| | - Sachin Dev Verma
- Spectroscopy Laboratory, School of Physical Sciences, Jawaharlal Nehru University , New Delhi 110067, India
| | - Nibedita Pal
- Spectroscopy Laboratory, School of Physical Sciences, Jawaharlal Nehru University , New Delhi 110067, India
| | - Sobhan Sen
- Spectroscopy Laboratory, School of Physical Sciences, Jawaharlal Nehru University , New Delhi 110067, India
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54
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Krick M, Holstein JJ, Wuttke A, Mata RA, Clever GH. Temperature-Dependent Dynamics of Push-Pull Rotor Systems Based on Acridinylidene Cyanoacetic Esters. European J Org Chem 2017. [DOI: 10.1002/ejoc.201700873] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Marcel Krick
- Department of Chemistry and Chemical Biology; TU Dortmund University; Otto-Hahn-Straße 6 44227 Dortmund Germany
| | - Julian J. Holstein
- Department of Chemistry and Chemical Biology; TU Dortmund University; Otto-Hahn-Straße 6 44227 Dortmund Germany
| | - Axel Wuttke
- Institute for Physical Chemistry; Georg-August-University Göttingen; Tammannstr. 4 37077 Göttingen Germany
| | - Ricardo A. Mata
- Institute for Physical Chemistry; Georg-August-University Göttingen; Tammannstr. 4 37077 Göttingen Germany
| | - Guido H. Clever
- Department of Chemistry and Chemical Biology; TU Dortmund University; Otto-Hahn-Straße 6 44227 Dortmund Germany
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55
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Ma N, van der Vaart A. Free Energy Coupling between DNA Bending and Base Flipping. J Chem Inf Model 2017; 57:2020-2026. [PMID: 28696686 DOI: 10.1021/acs.jcim.7b00215] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Free energy simulations are presented to probe the energetic coupling between DNA bending and the flipping of a central thymine in double stranded DNA 13mers. The energetics are shown to depend on the neighboring base pairs, and upstream C or T or downstream C tended to make flipping more costly. Flipping to the major groove side was generally preferred. Bending aids flipping, by pushing the system up in free energy, but for small and intermediate bending angles the two were uncorrelated. At higher bending angles, bending and flipping became correlated, and bending primed the system for base flipping toward the major groove. Flipping of the 6-4 pyrimidine-pyrimidone and pyrimidine dimer photoproducts is shown to be more facile than for undamaged DNA. For the damages, major groove flipping was preferred, and DNA bending was much facilitated in the 6-4 pyrimidine-pyrimidone damaged system. Aspects of the calculations were verified by structural analyses of protein-DNA complexes with flipped bases.
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Affiliation(s)
- Ning Ma
- Department of Chemistry, University of South Florida , 4202 East Fowler Avenue CHE 205, Tampa, Florida 33620, United States
| | - Arjan van der Vaart
- Department of Chemistry, University of South Florida , 4202 East Fowler Avenue CHE 205, Tampa, Florida 33620, United States
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56
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Paul T, Bera SC, Mishra PP. Direct observation of breathing dynamics at the mismatch induced DNA bubble with nanometre accuracy: a smFRET study. NANOSCALE 2017; 9:5835-5842. [PMID: 28332666 DOI: 10.1039/c6nr09348e] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The detailed conformational dynamics of the melted region in double-stranded DNA has been studied using a combination of ensemble and single-molecule FRET techniques. We monitored the millisecond time scale fluctuation kinetics of the two strands at the bubble region that varies with the size of the bubble. As the individual strands at the melting bubble behave as single-stranded DNA, and hence fluctuate dynamically to attain energetically favored configurations, the rates of these fluctuations increase with increase in the bubble size. In different short DNAs under investigation, the two strands never cross each other to form a knot, irrespective of the number of base pair mismatches present. Rather, they prefer to stay apart from each other, as the size of the bubble increases and follow exactly an opposite trend for bubbles of smaller size. The range within which the bubble strands fluctuate are monitored with great accuracy in the nanometre resolution from the single-molecule FRET measurements. The shape of the bubble that plays a crucial role in determining the activity of the DNA was speculated. These results shall be useful in quantifying the chemical processes within DNA as well as to develop a deeper understanding of the activity of the DNA due to induced mismatches.
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Affiliation(s)
- Tapas Paul
- Chemical Sciences Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064, India.
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57
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Lindahl V, Villa A, Hess B. Sequence dependency of canonical base pair opening in the DNA double helix. PLoS Comput Biol 2017; 13:e1005463. [PMID: 28369121 PMCID: PMC5393899 DOI: 10.1371/journal.pcbi.1005463] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Revised: 04/17/2017] [Accepted: 03/17/2017] [Indexed: 12/15/2022] Open
Abstract
The flipping-out of a DNA base from the double helical structure is a key step of many cellular processes, such as DNA replication, modification and repair. Base pair opening is the first step of base flipping and the exact mechanism is still not well understood. We investigate sequence effects on base pair opening using extensive classical molecular dynamics simulations targeting the opening of 11 different canonical base pairs in two DNA sequences. Two popular biomolecular force fields are applied. To enhance sampling and calculate free energies, we bias the simulation along a simple distance coordinate using a newly developed adaptive sampling algorithm. The simulation is guided back and forth along the coordinate, allowing for multiple opening pathways. We compare the calculated free energies with those from an NMR study and check assumptions of the model used for interpreting the NMR data. Our results further show that the neighboring sequence is an important factor for the opening free energy, but also indicates that other sequence effects may play a role. All base pairs are observed to have a propensity for opening toward the major groove. The preferred opening base is cytosine for GC base pairs, while for AT there is sequence dependent competition between the two bases. For AT opening, we identify two non-canonical base pair interactions contributing to a local minimum in the free energy profile. For both AT and CG we observe long-lived interactions with water and with sodium ions at specific sites on the open base pair. The DNA double helix, a molecule that stores biological information, has become an iconic image of biomedical research. In order to use or repair the information it carries, the bases that are stacked in the helix need to be chemically exposed. This can happen either by separating the two strands in the helix or by flipping out individual bases. Here, we focus on the latter process. Usually proteins are involved in interactions with bases, but it is still unclear if bases are pulled out actively by proteins or if they act on spontaneously flipped bases. Although experiments can detect base pair opening, it is difficult to detect which base moves in which direction. Here, we present results from molecular dynamics simulations using a recently developed sampling method which improves the statistics in the simulations by enhancing the probability of the base pair opening event. We observe differences in probability, modes and mechanism of opening that depend not only on the types of the bases in the pair, but also strongly on their neighbors. This provides essential information for understanding how DNA functions.
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Affiliation(s)
- Viveca Lindahl
- Department of Physics and Swedish e-Science Research Center, KTH Royal Institute of Technology, Stockholm, Sweden
- Science for Life Laboratory, Stockholm and Uppsala, Stockholm, Sweden
| | - Alessandra Villa
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden
| | - Berk Hess
- Department of Physics and Swedish e-Science Research Center, KTH Royal Institute of Technology, Stockholm, Sweden
- Science for Life Laboratory, Stockholm and Uppsala, Stockholm, Sweden
- * E-mail:
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58
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Kilchherr F, Wachauf C, Pelz B, Rief M, Zacharias M, Dietz H. Single-molecule dissection of stacking forces in DNA. Science 2017; 353:353/6304/aaf5508. [PMID: 27609897 DOI: 10.1126/science.aaf5508] [Citation(s) in RCA: 141] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Accepted: 07/01/2016] [Indexed: 01/01/2023]
Abstract
We directly measured at the single-molecule level the forces and lifetimes of DNA base-pair stacking interactions for all stack sequence combinations. Our experimental approach combined dual-beam optical tweezers with DNA origami components to allow positioning of blunt-end DNA helices so that the weak stacking force could be isolated. Base-pair stack arrays that lacked a covalent backbone connection spontaneously dissociated at average rates ranging from 0.02 to 500 per second, depending on the sequence combination and stack array size. Forces in the range from 2 to 8 piconewtons that act along the helical direction only mildly accelerated the stochastic unstacking process. The free-energy increments per stack that we estimate from the measured forward and backward kinetic rates ranged from -0.8 to -3.4 kilocalories per mole, depending on the sequence combination. Our data contributes to understanding the mechanics of DNA processing in biology, and it is helpful for designing the kinetics of DNA-based nanoscale devices according to user specifications.
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Affiliation(s)
- Fabian Kilchherr
- Labor für Biomolekulare Nanotechnologie, Physik Department and Walter Schottky Institute, Technische Universität München, Am Coulombwall 4a, Garching near Munich, Germany
| | - Christian Wachauf
- Labor für Biomolekulare Nanotechnologie, Physik Department and Walter Schottky Institute, Technische Universität München, Am Coulombwall 4a, Garching near Munich, Germany
| | - Benjamin Pelz
- Lehrstuhl für Molekulare Biophysik, Physik Department, Technische Universität München, James-Franck-Strasse 1, Garching near Munich, Germany
| | - Matthias Rief
- Lehrstuhl für Molekulare Biophysik, Physik Department, Technische Universität München, James-Franck-Strasse 1, Garching near Munich, Germany. Munich Center for Integrated Protein Science, 81377 Munich, Germany
| | - Martin Zacharias
- Lehrstuhl für Theoretische Biophysik, Physik Department, Technische Universität München, James-Franck-Strasse 1, Garching near Munich, Germany. Munich Center for Integrated Protein Science, 81377 Munich, Germany
| | - Hendrik Dietz
- Labor für Biomolekulare Nanotechnologie, Physik Department and Walter Schottky Institute, Technische Universität München, Am Coulombwall 4a, Garching near Munich, Germany. Munich Center for Integrated Protein Science, 81377 Munich, Germany. Institute for Advanced Study, TUM, Germany.
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59
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Wu Z, Bi H, Pan S, Meng L, Zhao XS. Determination of Equilibrium Constant and Relative Brightness in Fluorescence Correlation Spectroscopy by Considering Third-Order Correlations. J Phys Chem B 2016; 120:11674-11682. [DOI: 10.1021/acs.jpcb.6b07953] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Zhenqin Wu
- Department of Chemical Biology, Beijing National Laboratory for Molecular
Sciences, State Key Laboratory for Structural Chemistry of Unstable
and Stable Species, College of Chemistry and Molecular Engineering, ‡Biodynamic Optical
Imaging Center (BIOPIC), and §School of Life Sciences, Peking University, Beijing 100871, China
| | - Huimin Bi
- Department of Chemical Biology, Beijing National Laboratory for Molecular
Sciences, State Key Laboratory for Structural Chemistry of Unstable
and Stable Species, College of Chemistry and Molecular Engineering, ‡Biodynamic Optical
Imaging Center (BIOPIC), and §School of Life Sciences, Peking University, Beijing 100871, China
| | - Sichen Pan
- Department of Chemical Biology, Beijing National Laboratory for Molecular
Sciences, State Key Laboratory for Structural Chemistry of Unstable
and Stable Species, College of Chemistry and Molecular Engineering, ‡Biodynamic Optical
Imaging Center (BIOPIC), and §School of Life Sciences, Peking University, Beijing 100871, China
| | - Lingyi Meng
- Department of Chemical Biology, Beijing National Laboratory for Molecular
Sciences, State Key Laboratory for Structural Chemistry of Unstable
and Stable Species, College of Chemistry and Molecular Engineering, ‡Biodynamic Optical
Imaging Center (BIOPIC), and §School of Life Sciences, Peking University, Beijing 100871, China
| | - Xin Sheng Zhao
- Department of Chemical Biology, Beijing National Laboratory for Molecular
Sciences, State Key Laboratory for Structural Chemistry of Unstable
and Stable Species, College of Chemistry and Molecular Engineering, ‡Biodynamic Optical
Imaging Center (BIOPIC), and §School of Life Sciences, Peking University, Beijing 100871, China
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60
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Yang YI, Zhang J, Che X, Yang L, Gao YQ. Efficient sampling over rough energy landscapes with high barriers: A combination of metadynamics with integrated tempering sampling. J Chem Phys 2016; 144:094105. [PMID: 26957155 DOI: 10.1063/1.4943004] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
In order to efficiently overcome high free energy barriers embedded in a complex energy landscape and calculate overall thermodynamics properties using molecular dynamics simulations, we developed and implemented a sampling strategy by combining the metadynamics with (selective) integrated tempering sampling (ITS/SITS) method. The dominant local minima on the potential energy surface (PES) are partially exalted by accumulating history-dependent potentials as in metadynamics, and the sampling over the entire PES is further enhanced by ITS/SITS. With this hybrid method, the simulated system can be rapidly driven across the dominant barrier along selected collective coordinates. Then, ITS/SITS ensures a fast convergence of the sampling over the entire PES and an efficient calculation of the overall thermodynamic properties of the simulation system. To test the accuracy and efficiency of this method, we first benchmarked this method in the calculation of ϕ - ψ distribution of alanine dipeptide in explicit solvent. We further applied it to examine the design of template molecules for aromatic meta-C-H activation in solutions and investigate solution conformations of the nonapeptide Bradykinin involving slow cis-trans isomerizations of three proline residues.
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Affiliation(s)
- Y Isaac Yang
- Institute of Theoretical and Computational Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Jun Zhang
- Institute of Theoretical and Computational Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Xing Che
- Institute of Theoretical and Computational Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Lijiang Yang
- Institute of Theoretical and Computational Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Yi Qin Gao
- Institute of Theoretical and Computational Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
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61
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Structure of the EndoMS-DNA Complex as Mismatch Restriction Endonuclease. Structure 2016; 24:1960-1971. [PMID: 27773688 DOI: 10.1016/j.str.2016.09.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Revised: 08/08/2016] [Accepted: 09/28/2016] [Indexed: 01/17/2023]
Abstract
Archaeal NucS nuclease was thought to degrade the single-stranded region of branched DNA, which contains flapped and splayed DNA. However, recent findings indicated that EndoMS, the orthologous enzyme of NucS, specifically cleaves double-stranded DNA (dsDNA) containing mismatched bases. In this study, we determined the structure of the EndoMS-DNA complex. The complex structure of the EndoMS dimer with dsDNA unexpectedly revealed that the mismatched bases were flipped out into binding sites, and the overall architecture most resembled that of restriction enzymes. The structure of the apo form was similar to the reported structure of Pyrococcus abyssi NucS, indicating that movement of the C-terminal domain from the resting state was required for activity. In addition, a model of the EndoMS-PCNA-DNA complex was preliminarily verified with electron microscopy. The structures strongly support the idea that EndoMS acts in a mismatch repair pathway.
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62
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Bi H, Yin Y, Pan B, Li G, Zhao XS. Scanning Single-Molecule Fluorescence Correlation Spectroscopy Enables Kinetics Study of DNA Hairpin Folding with a Time Window from Microseconds to Seconds. J Phys Chem Lett 2016; 7:1865-1871. [PMID: 27140004 DOI: 10.1021/acs.jpclett.6b00720] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Single-molecule fluorescence measurements have been widely used to explore kinetics and dynamics of biological systems. Among them, single-molecule imaging (SMI) is good at tracking processes slower than tens of milliseconds, whereas fluorescence correlation spectroscopy (FCS) is good at probing processes faster than submilliseconds. However, there is still shortage of simple yet effective single-molecule fluorescence method to cover the time-scale between submilliseconds and tens of milliseconds. To effectively bridge this millisecond gap, we developed a single-molecule fluorescence correlation spectroscopy (smFCS) method that works on surface-immobilized single molecules through surface scanning. We validated it by monitoring the classical DNA hairpin folding process. With a wide time window from microseconds to seconds, the experimental data are well fitted to the two-state folding model. All relevant molecular parameters, including the relative fluorescence brightness, equilibrium constant, and reaction rate constants, were uniquely determined.
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Affiliation(s)
- Huimin Bi
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Department of Chemical Biology, College of Chemistry and Molecular Engineering, and Biodynamic Optical Imaging Center (BIOPIC), Peking University , Beijing 100871, China
| | - Yandong Yin
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Department of Chemical Biology, College of Chemistry and Molecular Engineering, and Biodynamic Optical Imaging Center (BIOPIC), Peking University , Beijing 100871, China
| | - Bailong Pan
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Department of Chemical Biology, College of Chemistry and Molecular Engineering, and Biodynamic Optical Imaging Center (BIOPIC), Peking University , Beijing 100871, China
| | - Geng Li
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Department of Chemical Biology, College of Chemistry and Molecular Engineering, and Biodynamic Optical Imaging Center (BIOPIC), Peking University , Beijing 100871, China
| | - Xin Sheng Zhao
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Department of Chemical Biology, College of Chemistry and Molecular Engineering, and Biodynamic Optical Imaging Center (BIOPIC), Peking University , Beijing 100871, China
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63
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Johnson RP, Fleming AM, Beuth LR, Burrows CJ, White HS. Base Flipping within the α-Hemolysin Latch Allows Single-Molecule Identification of Mismatches in DNA. J Am Chem Soc 2016; 138:594-603. [PMID: 26704521 PMCID: PMC4828915 DOI: 10.1021/jacs.5b10710] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
A method for identifying and differentiating DNA duplexes containing the mismatched base pairs CC and CA at single molecule resolution with the protein pore α-hemolysin (αHL) is presented. Unique modulating current signatures are observed for duplexes containing the CC and CA mismatches when the mismatch site in the duplex is situated in proximity to the latch constriction of αHL during DNA residence inside the pore. The frequency and current amplitude of the modulation states are dependent on the mismatch type (CC or CA) permitting easy discrimination of these mismatches from one another, and from a fully complementary duplex that exhibits no modulation. We attribute the modulating current signatures to base flipping and subsequent interaction with positively charged lysine residues at the latch constriction of αHL. Our hypothesis is supported by the extended residence times of DNA duplexes within the pore when a mismatch is in proximity to the latch constriction, and by the loss of the two-state current signature in low pH buffers (<6.3), where the protonation of one of the cytosine bases increases the stability of the intrahelical state.
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Affiliation(s)
- Robert P Johnson
- Department of Chemistry, University of Utah , 315 S. 1400 East, Salt Lake City, Utah 84112-0850, United States
| | - Aaron M Fleming
- Department of Chemistry, University of Utah , 315 S. 1400 East, Salt Lake City, Utah 84112-0850, United States
| | - Laura R Beuth
- Department of Chemistry, University of Utah , 315 S. 1400 East, Salt Lake City, Utah 84112-0850, United States
| | - Cynthia J Burrows
- Department of Chemistry, University of Utah , 315 S. 1400 East, Salt Lake City, Utah 84112-0850, United States
| | - Henry S White
- Department of Chemistry, University of Utah , 315 S. 1400 East, Salt Lake City, Utah 84112-0850, United States
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64
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Jena NR, Bansal M, Mishra PC. Conformational stabilities of iminoallantoin and its base pairs in DNA: implications for mutagenicity. Phys Chem Chem Phys 2016; 18:12774-83. [DOI: 10.1039/c6cp02212j] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Under acidic conditions, insertion of G opposite Ia may lead to G to C mutations in DNA.
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Affiliation(s)
- N. R. Jena
- Discipline of Natural Sciences
- Indian Institute of Information Technology
- Design and Manufacturing
- Jabalpur-482005
- India
| | - Manju Bansal
- Molecular Biophysics Unit
- Indian Institute of Science
- Bangalore-560012
- India
| | - P. C. Mishra
- Department of Physics
- Banaras Hindu University
- Varanasi-221005
- India
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65
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Hoffman EA, Frey BL, Smith LM, Auble DT. Formaldehyde crosslinking: a tool for the study of chromatin complexes. J Biol Chem 2015; 290:26404-11. [PMID: 26354429 DOI: 10.1074/jbc.r115.651679] [Citation(s) in RCA: 239] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Formaldehyde has been used for decades to probe macromolecular structure and function and to trap complexes, cells, and tissues for further analysis. Formaldehyde crosslinking is routinely employed for detection and quantification of protein-DNA interactions, interactions between chromatin proteins, and interactions between distal segments of the chromatin fiber. Despite widespread use and a rich biochemical literature, important aspects of formaldehyde behavior in cells have not been well described. Here, we highlight features of formaldehyde chemistry relevant to its use in analyses of chromatin complexes, focusing on how its properties may influence studies of chromatin structure and function.
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Affiliation(s)
- Elizabeth A Hoffman
- From the Department of Biochemistry and Molecular Genetics, University of Virginia Health System, Charlottesville, Virginia 22908 and
| | - Brian L Frey
- the Department of Chemistry and Genome Center of Wisconsin, University of Wisconsin, Madison, Wisconsin 53706
| | - Lloyd M Smith
- the Department of Chemistry and Genome Center of Wisconsin, University of Wisconsin, Madison, Wisconsin 53706
| | - David T Auble
- From the Department of Biochemistry and Molecular Genetics, University of Virginia Health System, Charlottesville, Virginia 22908 and
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66
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Nardo L, Lamperti M, Salerno D, Cassina V, Missana N, Bondani M, Tempestini A, Mantegazza F. Effects of non-CpG site methylation on DNA thermal stability: a fluorescence study. Nucleic Acids Res 2015; 43:10722-33. [PMID: 26354864 PMCID: PMC4678853 DOI: 10.1093/nar/gkv884] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 08/21/2015] [Indexed: 11/14/2022] Open
Abstract
Cytosine methylation is a widespread epigenetic regulation mechanism. In healthy mature cells, methylation occurs at CpG dinucleotides within promoters, where it primarily silences gene expression by modifying the binding affinity of transcription factors to the promoters. Conversely, a recent study showed that in stem cells and cancer cell precursors, methylation also occurs at non-CpG pairs and involves introns and even gene bodies. The epigenetic role of such methylations and the molecular mechanisms by which they induce gene regulation remain elusive. The topology of both physiological and aberrant non-CpG methylation patterns still has to be detailed and could be revealed by using the differential stability of the duplexes formed between site-specific oligonucleotide probes and the corresponding methylated regions of genomic DNA. Here, we present a systematic study of the thermal stability of a DNA oligonucleotide sequence as a function of the number and position of non-CpG methylation sites. The melting temperatures were determined by monitoring the fluorescence of donor-acceptor dual-labelled oligonucleotides at various temperatures. An empirical model that estimates the methylation-induced variations in the standard values of hybridization entropy and enthalpy was developed.
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Affiliation(s)
- Luca Nardo
- Department of Health Sciences, University of Milano Bicocca, Via Cadore 48, Monza, MB 20900, Italy
| | - Marco Lamperti
- Department of Science and High Technology, University of Insubria, Via Valleggio 11, Como, CO 22100, Italy
| | - Domenico Salerno
- Department of Health Sciences, University of Milano Bicocca, Via Cadore 48, Monza, MB 20900, Italy
| | - Valeria Cassina
- Department of Health Sciences, University of Milano Bicocca, Via Cadore 48, Monza, MB 20900, Italy
| | - Natalia Missana
- Department of Health Sciences, University of Milano Bicocca, Via Cadore 48, Monza, MB 20900, Italy
| | - Maria Bondani
- Institute for Photonics and Nanotechnology, National Research Council, Via Valleggio 11, Como, CO 22100, Italy
| | - Alessia Tempestini
- LENS-Department of Physics and Astronomy, University of Firenze, Via Sansone 1, Sesto Fiorentino, FI 50019, Italy
| | - Francesco Mantegazza
- Department of Health Sciences, University of Milano Bicocca, Via Cadore 48, Monza, MB 20900, Italy
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67
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Zhang J, Yang YI, Yang L, Gao YQ. Conformational Preadjustment in Aqueous Claisen Rearrangement Revealed by SITS-QM/MM MD Simulations. J Phys Chem B 2015; 119:5518-30. [DOI: 10.1021/jp511057f] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jun Zhang
- Institute of Theoretical and Computational Chemistry,
College of
Chemistry and Molecular Engineering, and ‡Biodynamic Optical Imaging Center, Peking University, Beijing 100871, China
| | - Yi Isaac Yang
- Institute of Theoretical and Computational Chemistry,
College of
Chemistry and Molecular Engineering, and ‡Biodynamic Optical Imaging Center, Peking University, Beijing 100871, China
| | - Lijiang Yang
- Institute of Theoretical and Computational Chemistry,
College of
Chemistry and Molecular Engineering, and ‡Biodynamic Optical Imaging Center, Peking University, Beijing 100871, China
| | - Yi Qin Gao
- Institute of Theoretical and Computational Chemistry,
College of
Chemistry and Molecular Engineering, and ‡Biodynamic Optical Imaging Center, Peking University, Beijing 100871, China
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68
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Visualizing transient Watson-Crick-like mispairs in DNA and RNA duplexes. Nature 2015; 519:315-20. [PMID: 25762137 DOI: 10.1038/nature14227] [Citation(s) in RCA: 176] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Accepted: 01/09/2015] [Indexed: 11/08/2022]
Abstract
Rare tautomeric and anionic nucleobases are believed to have fundamental biological roles, but their prevalence and functional importance has remained elusive because they exist transiently, in low abundance, and involve subtle movements of protons that are difficult to visualize. Using NMR relaxation dispersion, we show here that wobble dG•dT and rG•rU mispairs in DNA and RNA duplexes exist in dynamic equilibrium with short-lived, low-populated Watson-Crick-like mispairs that are stabilized by rare enolic or anionic bases. These mispairs can evade Watson-Crick fidelity checkpoints and form with probabilities (10(-3) to 10(-5)) that strongly imply a universal role in replication and translation errors. Our results indicate that rare tautomeric and anionic bases are widespread in nucleic acids, expanding their structural and functional complexity beyond that attainable with canonical bases.
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69
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Buechner CN, Maiti A, Drohat AC, Tessmer I. Lesion search and recognition by thymine DNA glycosylase revealed by single molecule imaging. Nucleic Acids Res 2015; 43:2716-29. [PMID: 25712093 PMCID: PMC4357730 DOI: 10.1093/nar/gkv139] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The ability of DNA glycosylases to rapidly and efficiently detect lesions among a vast excess of nondamaged DNA bases is vitally important in base excision repair (BER). Here, we use single molecule imaging by atomic force microscopy (AFM) supported by a 2-aminopurine fluorescence base flipping assay to study damage search by human thymine DNA glycosylase (hTDG), which initiates BER of mutagenic and cytotoxic G:T and G:U mispairs in DNA. Our data reveal an equilibrium between two conformational states of hTDG–DNA complexes, assigned as search complex (SC) and interrogation complex (IC), both at target lesions and undamaged DNA sites. Notably, for both hTDG and a second glycosylase, hOGG1, which recognizes structurally different 8-oxoguanine lesions, the conformation of the DNA in the SC mirrors innate structural properties of their respective target sites. In the IC, the DNA is sharply bent, as seen in crystal structures of hTDG lesion recognition complexes, which likely supports the base flipping required for lesion identification. Our results support a potentially general concept of sculpting of glycosylases to their targets, allowing them to exploit the energetic cost of DNA bending for initial lesion sensing, coupled with continuous (extrahelical) base interrogation during lesion search by DNA glycosylases.
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Affiliation(s)
- Claudia N Buechner
- Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg, Würzburg, Germany
| | - Atanu Maiti
- Department of Biochemistry and Molecular Biology and Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Alexander C Drohat
- Department of Biochemistry and Molecular Biology and Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Ingrid Tessmer
- Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg, Würzburg, Germany
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