1
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Revealing atomic-scale molecular diffusion of a plant-transcription factor WRKY domain protein along DNA. Proc Natl Acad Sci U S A 2021; 118:2102621118. [PMID: 34074787 PMCID: PMC8201915 DOI: 10.1073/pnas.2102621118] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
In transcription factors’ search for target genes, one-dimensional diffusion of the protein along DNA is essential. Experimentally, it remains challenging to resolve the individual diffusional steps of protein on DNA. Here, we report mainly all-atom equilibrium simulations of a WRKY domain protein in association with and diffusion along DNA. We demonstrate a complete stepping cycle of the protein for one base pair on DNA within microseconds, along with stochastic motions. Processive protein diffusions on DNA have been further sampled in a coarse-grained model. We have also found preferential DNA-strand association of the domain protein, which becomes most prominent at specific DNA binding, and it can be common for small-domain proteins to balance movements on the DNA with the sequence recognition. Transcription factor (TF) target search on genome is highly essential for gene expression and regulation. High-resolution determination of TF diffusion along DNA remains technically challenging. Here, we constructed a TF model system using the plant WRKY domain protein in complex with DNA from crystallography and demonstrated microsecond diffusion dynamics of WRKY on DNA by employing all-atom molecular-dynamics (MD) simulations. Notably, we found that WRKY preferentially binds to one strand of DNA with significant energetic bias compared with the other, or nonpreferred strand. The preferential DNA-strand binding becomes most prominent in the static process, from nonspecific to specific DNA binding, but less distinct during diffusive movements of the domain protein on the DNA. Remarkably, without employing acceleration forces or bias, we captured a complete one-base-pair stepping cycle of the protein tracking along major groove of DNA with a homogeneous poly-adenosine sequence, as individual hydrogen bonds break and reform at the protein–DNA binding interface. Further DNA-groove tracking motions of the protein forward or backward, with occasional sliding as well as strand crossing to minor groove of DNA, were also captured. The processive diffusion of WRKY along DNA has been further sampled via coarse-grained MD simulations. The study thus provides structural dynamics details on diffusion of a small TF domain protein, suggests how the protein approaches a specific recognition site on DNA, and supports further high-precision experimental detection. The stochastic movements revealed in the TF diffusion also provide general clues about how other protein walkers step and slide along DNA.
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2
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Landová B, Šilhán J. Conformational changes of DNA repair glycosylase MutM triggered by DNA binding. FEBS Lett 2020; 594:3032-3044. [PMID: 32598485 DOI: 10.1002/1873-3468.13876] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2020] [Revised: 05/28/2020] [Accepted: 06/23/2020] [Indexed: 12/22/2022]
Abstract
Bacterial MutM is a DNA repair glycosylase removing DNA damage generated from oxidative stress and, therefore, preventing mutations and genomic instability. MutM belongs to the Fpg/Nei family of prokaryotic enzymes sharing structural and functional similarities with their eukaryotic counterparts, for example, NEIL1-NEIL3. Here, we present two crystal structures of MutM from pathogenic Neisseria meningitidis: a MutM holoenzyme and MutM bound to DNA. The free enzyme exists in an open conformation, while upon binding to DNA, both the enzyme and DNA undergo substantial structural changes and domain rearrangement. Our data show that not only NEI glycosylases but also the MutMs undergo dramatic conformational changes. Moreover, crystallographic data support the previously published observations that MutM enzymes are rather flexible and dynamic molecules.
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Affiliation(s)
- Barbora Landová
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Prague, Czech Republic
| | - Jan Šilhán
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Prague, Czech Republic
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3
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Nelson SR, Kathe SD, Hilzinger TS, Averill AM, Warshaw DM, Wallace SS, Lee AJ. Single molecule glycosylase studies with engineered 8-oxoguanine DNA damage sites show functional defects of a MUTYH polyposis variant. Nucleic Acids Res 2019; 47:3058-3071. [PMID: 30698731 PMCID: PMC6451117 DOI: 10.1093/nar/gkz045] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 01/03/2019] [Accepted: 01/17/2019] [Indexed: 01/09/2023] Open
Abstract
Proper repair of oxidatively damaged DNA bases is essential to maintain genome stability. 8-Oxoguanine (7,8-dihydro-8-oxoguanine, 8-oxoG) is a dangerous DNA lesion because it can mispair with adenine (A) during replication resulting in guanine to thymine transversion mutations. MUTYH DNA glycosylase is responsible for recognizing and removing the adenine from 8-oxoG:adenine (8-oxoG:A) sites. Biallelic mutations in the MUTYH gene predispose individuals to MUTYH-associated polyposis (MAP), and the most commonly observed mutation in some MAP populations is Y165C. Tyr165 is a ‘wedge’ residue that intercalates into the DNA duplex in the lesion bound state. Here, we utilize single molecule fluorescence microscopy to visualize the real-time search behavior of Escherichia coli and Mus musculus MUTYH WT and wedge variant orthologs on DNA tightropes that contain 8-oxoG:A, 8-oxoG:cytosine, or apurinic product analog sites. We observe that MUTYH WT is able to efficiently find 8-oxoG:A damage and form highly stable bound complexes. In contrast, MUTYH Y150C shows decreased binding lifetimes on undamaged DNA and fails to form a stable lesion recognition complex at damage sites. These findings suggest that MUTYH does not rely upon the wedge residue for damage site recognition, but this residue stabilizes the lesion recognition complex.
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Affiliation(s)
- Shane R Nelson
- Department of Molecular Physiology and Biophysics, Robert Larner College of Medicine, University of Vermont, Burlington, VT 05405, USA
| | - Scott D Kathe
- Department of Microbiology and Molecular Genetics, Robert Larner College of Medicine and College of Agriculture and Life Sciences, University of Vermont, Burlington, VT 05405, USA
| | - Thomas S Hilzinger
- Department of Microbiology and Molecular Genetics, Robert Larner College of Medicine and College of Agriculture and Life Sciences, University of Vermont, Burlington, VT 05405, USA
| | - April M Averill
- Department of Microbiology and Molecular Genetics, Robert Larner College of Medicine and College of Agriculture and Life Sciences, University of Vermont, Burlington, VT 05405, USA
| | - David M Warshaw
- Department of Molecular Physiology and Biophysics, Robert Larner College of Medicine, University of Vermont, Burlington, VT 05405, USA
| | - Susan S Wallace
- Department of Microbiology and Molecular Genetics, Robert Larner College of Medicine and College of Agriculture and Life Sciences, University of Vermont, Burlington, VT 05405, USA
| | - Andrea J Lee
- Department of Microbiology and Molecular Genetics, Robert Larner College of Medicine and College of Agriculture and Life Sciences, University of Vermont, Burlington, VT 05405, USA
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4
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Da LT, Yu J. Base-flipping dynamics from an intrahelical to an extrahelical state exerted by thymine DNA glycosylase during DNA repair process. Nucleic Acids Res 2019; 46:5410-5425. [PMID: 29762710 PMCID: PMC6009601 DOI: 10.1093/nar/gky386] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Accepted: 04/30/2018] [Indexed: 12/17/2022] Open
Abstract
Thymine DNA glycosylase (TDG) is a DNA repair enzyme that excises a variety of mismatched or damaged nucleotides (nts), e.g. dU, dT, 5fC and 5caC. TDG is shown to play essential roles in maintaining genome integrity and correctly programming epigenetic modifications through DNA demethylation. After locating the lesions, TDG employs a base-flipping strategy to recognize the damaged nucleobases, whereby the interrogated nt is extruded from the DNA helical stack and binds into the TDG active site. The dynamic mechanism of the base-flipping process at an atomistic resolution, however, remains elusive. Here, we employ the Markov State Model (MSM) constructed from extensive all-atom molecular dynamics (MD) simulations to reveal the complete base-flipping process for a G.T mispair at a tens of microsecond timescale. Our studies identify critical intermediates of the mispaired dT during its extrusion process and reveal the key TDG residues involved in the inter-state transitions. Notably, we find an active role of TDG in promoting the intrahelical nt eversion, sculpturing the DNA backbone, and penetrating into the DNA minor groove. Three additional TDG substrates, namely dU, 5fC, and 5caC, are further tested to evaluate the substituent effects of various chemical modifications of the pyrimidine ring on base-flipping dynamics.
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Affiliation(s)
- Lin-Tai Da
- Key Laboratory of Systems Biomedicine (Ministry of Education), Shanghai Center for Systems Biomedicine, Shanghai JiaoTong University, 800 Dongchuan Road, Shanghai 200240, China
| | - Jin Yu
- Beijing Computational Science Research Center, Beijing 100193, China
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5
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Endutkin AV, Zharkov DO. Critical Sites of DNA Backbone Integrity for Damaged Base Removal by Formamidopyrimidine-DNA Glycosylase. Biochemistry 2019; 58:2740-2749. [PMID: 31120733 DOI: 10.1021/acs.biochem.9b00134] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
DNA glycosylases, the enzymes that initiate base excision DNA repair, recognize damaged bases through a series of precisely orchestrated movements. Most glycosylases sharply kink the DNA axis at the lesion site and extrude the target base from the DNA double helix into the enzyme's active site. Little attention has been paid so far to the role of the physical continuity of the DNA backbone in allowing the required conformational distortion. Here, we analyze base excision by formamidopyrimidine-DNA glycosylase (Fpg) from substrates keeping all phosphates but containing a nick within three nucleotides of the lesion in either DNA strand. Four phosphoester linkages at the damaged nucleotide and two nucleotides 3' to it were essential for Fpg activity, while the breakage of the others, even at the same critical phosphates, had no effect or even stimulated the reaction. Reduction of the likelihood of hydrogen bonding at the nicks by using dideoxynucleotides as their 3'-terminal groups was more detrimental for the activity. All phosphoester bonds in the complementary strand were dispensable for base excision, but nicks close to the orphaned nucleotide caused early termination of damaged strand cleavage. Elastic network analysis of Fpg-DNA structures showed that the vibrational motions of the critical phosphates are strongly correlated, in part due to the presence of the protein. Overall, our results suggest that mechanical forces propagating along the DNA backbone play a critical role in the correct conformational distortion of DNA by Fpg and possibly by other target base-everting DNA glycosylases.
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Affiliation(s)
- Anton V Endutkin
- SB RAS Institute of Chemical Biology and Fundamental Medicine , 8 Lavrentieva Avenue , Novosibirsk 630090 , Russia.,Novosibirsk State University , 2 Pirogova Street , Novosibirsk 630090 , Russia
| | - Dmitry O Zharkov
- SB RAS Institute of Chemical Biology and Fundamental Medicine , 8 Lavrentieva Avenue , Novosibirsk 630090 , Russia.,Novosibirsk State University , 2 Pirogova Street , Novosibirsk 630090 , Russia
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6
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Abstract
7,8-Dihydro-8-oxoguanine (oxoG) is the most abundant oxidative DNA lesion with dual coding properties. It forms both Watson–Crick (anti)oxoG:(anti)C and Hoogsteen (syn)oxoG:(anti)A base pairs without a significant distortion of a B-DNA helix. DNA polymerases bypass oxoG but the accuracy of nucleotide incorporation opposite the lesion varies depending on the polymerase-specific interactions with the templating oxoG and incoming nucleotides. High-fidelity replicative DNA polymerases read oxoG as a cognate base for A while treating oxoG:C as a mismatch. The mutagenic effects of oxoG in the cell are alleviated by specific systems for DNA repair and nucleotide pool sanitization, preventing mutagenesis from both direct DNA oxidation and oxodGMP incorporation. DNA translesion synthesis could provide an additional protective mechanism against oxoG mutagenesis in cells. Several human DNA polymerases of the X- and Y-families efficiently and accurately incorporate nucleotides opposite oxoG. In this review, we address the mutagenic potential of oxoG in cells and discuss the structural basis for oxoG bypass by different DNA polymerases and the mechanisms of the recognition of oxoG by DNA glycosylases and dNTP hydrolases.
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7
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Kladova OA, Grin IR, Fedorova OS, Kuznetsov NA, Zharkov DO. Conformational Dynamics of Damage Processing by Human DNA Glycosylase NEIL1. J Mol Biol 2019; 431:1098-1112. [DOI: 10.1016/j.jmb.2019.01.030] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Revised: 01/23/2019] [Accepted: 01/23/2019] [Indexed: 10/27/2022]
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8
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Endutkin AV, Koptelov SS, Popov AV, Torgasheva NA, Lomzov AA, Tsygankova AR, Skiba TV, Afonnikov DA, Zharkov DO. Residue coevolution reveals functionally important intramolecular interactions in formamidopyrimidine-DNA glycosylase. DNA Repair (Amst) 2018; 69:24-33. [DOI: 10.1016/j.dnarep.2018.07.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Revised: 07/04/2018] [Accepted: 07/04/2018] [Indexed: 10/28/2022]
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9
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Kladova OA, Krasnoperov LN, Kuznetsov NA, Fedorova OS. Kinetics and Thermodynamics of DNA Processing by Wild Type DNA-Glycosylase Endo III and Its Catalytically Inactive Mutant Forms. Genes (Basel) 2018; 9:genes9040190. [PMID: 29601551 PMCID: PMC5924532 DOI: 10.3390/genes9040190] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Revised: 03/22/2018] [Accepted: 03/27/2018] [Indexed: 02/01/2023] Open
Abstract
Endonuclease III (Endo III or Nth) is one of the key enzymes responsible for initiating the base excision repair of oxidized or reduced pyrimidine bases in DNA. In this study, a thermodynamic analysis of structural rearrangements of the specific and nonspecific DNA-duplexes during their interaction with Endo III is performed based on stopped-flow kinetic data. 1,3-diaza-2-oxophenoxazine (tCO), a fluorescent analog of the natural nucleobase cytosine, is used to record multistep DNA binding and lesion recognition within a temperature range (5-37 °C). Standard Gibbs energy, enthalpy, and entropy of the specific steps are derived from kinetic data using Van't Hoff plots. The data suggest that enthalpy-driven exothermic 5,6-dihydrouracil (DHU) recognition and desolvation-accompanied entropy-driven adjustment of the enzyme-substrate complex into a catalytically active state play equally important parts in the overall process. The roles of catalytically significant amino acids Lys120 and Asp138 in the DNA lesion recognition and catalysis are identified. Lys120 participates not only in the catalytic steps but also in the processes of local duplex distortion, whereas substitution Asp138Ala leads to a complete loss of the ability of Endo III to distort a DNA double chain during enzyme-DNA complex formation.
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Affiliation(s)
- Olga A Kladova
- Institute of Chemical Biology and Fundamental Medicine (ICBFM), 630090 Novosibirsk, Russia.
- Department of Natural Sciences, Novosibirsk State University, 630090 Novosibirsk, Russia.
| | - Lev N Krasnoperov
- New Jersey Institute of Technology, Department of Chemistry and Environment Sciences, University Heights, Newark, NJ 07102, USA.
| | - Nikita A Kuznetsov
- Institute of Chemical Biology and Fundamental Medicine (ICBFM), 630090 Novosibirsk, Russia.
| | - Olga S Fedorova
- Institute of Chemical Biology and Fundamental Medicine (ICBFM), 630090 Novosibirsk, Russia.
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10
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Lee AJ, Wallace SS. Hide and seek: How do DNA glycosylases locate oxidatively damaged DNA bases amidst a sea of undamaged bases? Free Radic Biol Med 2017; 107:170-178. [PMID: 27865982 PMCID: PMC5433924 DOI: 10.1016/j.freeradbiomed.2016.11.024] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 11/11/2016] [Accepted: 11/13/2016] [Indexed: 01/10/2023]
Abstract
The first step of the base excision repair (BER) pathway responsible for removing oxidative DNA damage utilizes DNA glycosylases to find and remove the damaged DNA base. How glycosylases find the damaged base amidst a sea of undamaged bases has long been a question in the BER field. Single molecule total internal reflection fluorescence microscopy (SM TIRFM) experiments have allowed for an exciting look into this search mechanism and have found that DNA glycosylases scan along the DNA backbone in a bidirectional and random fashion. By comparing the search behavior of bacterial glycosylases from different structural families and with varying substrate specificities, it was found that glycosylases search for damage by periodically inserting a wedge residue into the DNA stack as they redundantly search tracks of DNA that are 450-600bp in length. These studies open up a wealth of possibilities for further study in real time of the interactions of DNA glycosylases and other BER enzymes with various DNA substrates.
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Affiliation(s)
- Andrea J Lee
- Department of Microbiology and Molecular Genetics, The Markey Center for Molecular Genetics, The University of Vermont, 95 Carrigan Drive, Burlington, VT 05405, USA
| | - Susan S Wallace
- Department of Microbiology and Molecular Genetics, The Markey Center for Molecular Genetics, The University of Vermont, 95 Carrigan Drive, Burlington, VT 05405, USA.
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11
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Boiteux S, Coste F, Castaing B. Repair of 8-oxo-7,8-dihydroguanine in prokaryotic and eukaryotic cells: Properties and biological roles of the Fpg and OGG1 DNA N-glycosylases. Free Radic Biol Med 2017; 107:179-201. [PMID: 27903453 DOI: 10.1016/j.freeradbiomed.2016.11.042] [Citation(s) in RCA: 104] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Revised: 11/22/2016] [Accepted: 11/25/2016] [Indexed: 01/23/2023]
Abstract
Oxidatively damaged DNA results from the attack of sugar and base moieties by reactive oxygen species (ROS), which are formed as byproducts of normal cell metabolism and during exposure to endogenous or exogenous chemical or physical agents. Guanine, having the lowest redox potential, is the DNA base the most susceptible to oxidation, yielding products such as 8-oxo-7,8-dihydroguanine (8-oxoG) and 2-6-diamino-4-hydroxy-5-formamidopyrimidine (FapyG). In DNA, 8-oxoG was shown to be mutagenic yielding GC to TA transversions upon incorporation of dAMP opposite this lesion by replicative DNA polymerases. In prokaryotic and eukaryotic cells, 8-oxoG is primarily repaired by the base excision repair pathway (BER) initiated by a DNA N-glycosylase, Fpg and OGG1, respectively. In Escherichia coli, Fpg cooperates with MutY and MutT to prevent 8-oxoG-induced mutations, the "GO-repair system". In Saccharomyces cerevisiae, OGG1 cooperates with nucleotide excision repair (NER), mismatch repair (MMR), post-replication repair (PRR) and DNA polymerase η to prevent mutagenesis. Human and mouse cells mobilize all these pathways using OGG1, MUTYH (MutY-homolog also known as MYH), MTH1 (MutT-homolog also known as NUDT1), NER, MMR, NEILs and DNA polymerases η and λ, to prevent 8-oxoG-induced mutations. In fact, mice deficient in both OGG1 and MUTYH develop cancer in different organs at adult age, which points to the critical impact of 8-oxoG repair on genetic stability in mammals. In this review, we will focus on Fpg and OGG1 proteins, their biochemical and structural properties as well as their biological roles. Other DNA N-glycosylases able to release 8-oxoG from damaged DNA in various organisms will be discussed. Finally, we will report on the role of OGG1 in human disease and the possible use of 8-oxoG DNA N-glycosylases as therapeutic targets.
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Affiliation(s)
- Serge Boiteux
- Centre de Biophysique Moléculaire, CNRS, UPR4301, rue Charles Sadron, 45072 Orléans, France.
| | - Franck Coste
- Centre de Biophysique Moléculaire, CNRS, UPR4301, rue Charles Sadron, 45072 Orléans, France
| | - Bertrand Castaing
- Centre de Biophysique Moléculaire, CNRS, UPR4301, rue Charles Sadron, 45072 Orléans, France.
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12
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Popov AV, Endutkin AV, Vorobjev YN, Zharkov DO. Molecular dynamics simulation of the opposite-base preference and interactions in the active site of formamidopyrimidine-DNA glycosylase. BMC STRUCTURAL BIOLOGY 2017; 17:5. [PMID: 28482831 PMCID: PMC5422863 DOI: 10.1186/s12900-017-0075-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/12/2016] [Accepted: 04/20/2017] [Indexed: 01/20/2023]
Abstract
Background Formamidopyrimidine-DNA glycosylase (Fpg) removes abundant pre-mutagenic 8-oxoguanine (oxoG) bases from DNA through nucleophilic attack of its N-terminal proline at C1′ of the damaged nucleotide. Since oxoG efficiently pairs with both C and A, Fpg must excise oxoG from pairs with C but not with A, otherwise a mutation occurs. The crystal structures of several Fpg–DNA complexes have been solved, yet no structure with A opposite the lesion is available. Results Here we use molecular dynamic simulation to model interactions in the pre-catalytic complex of Lactococcus lactis Fpg with DNA containing oxoG opposite C or A, the latter in either syn or anti conformation. The catalytic dyad, Pro1–Glu2, was modeled in all four possible protonation states. Only one transition was observed in the experimental reaction rate pH dependence plots, and Glu2 kept the same set of interactions regardless of its protonation state, suggesting that it does not limit the reaction rate. The adenine base opposite oxoG was highly distorting for the adjacent nucleotides: in the more stable syn models it formed non-canonical bonds with out-of-register nucleotides in both the damaged and the complementary strand, whereas in the anti models the adenine either formed non-canonical bonds or was expelled into the major groove. The side chains of Arg109 and Phe111 that Fpg inserts into DNA to maintain its kinked conformation tended to withdraw from their positions if A was opposite to the lesion. The region showing the largest differences in the dynamics between oxoG:C and oxoG:A substrates was unexpectedly remote from the active site, located near the linker joining the two domains of Fpg. This region was also highly conserved among 124 analyzed Fpg sequences. Three sites trapping water molecules through multiple bonds were identified on the protein–DNA interface, apparently helping to maintain enzyme-induced DNA distortion and participating in oxoG recognition. Conclusion Overall, the discrimination against A opposite to the lesion seems to be due to incorrect DNA distortion around the lesion-containing base pair and, possibly, to gross movement of protein domains connected by the linker. Electronic supplementary material The online version of this article (doi:10.1186/s12900-017-0075-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Alexander V Popov
- SB RAS Institute of Chemical Biology and Fundamental Medicine, 8 Lavrentieva Ave., Novosibirsk, 630090, Russia
| | - Anton V Endutkin
- SB RAS Institute of Chemical Biology and Fundamental Medicine, 8 Lavrentieva Ave., Novosibirsk, 630090, Russia.,Novosibrsk State University, 2 Pirogova St., Novosibirsk, 630090, Russia
| | - Yuri N Vorobjev
- SB RAS Institute of Chemical Biology and Fundamental Medicine, 8 Lavrentieva Ave., Novosibirsk, 630090, Russia. .,Novosibrsk State University, 2 Pirogova St., Novosibirsk, 630090, Russia.
| | - Dmitry O Zharkov
- SB RAS Institute of Chemical Biology and Fundamental Medicine, 8 Lavrentieva Ave., Novosibirsk, 630090, Russia. .,Novosibrsk State University, 2 Pirogova St., Novosibirsk, 630090, Russia.
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13
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Robey-Bond SM, Benson MA, Barrantes-Reynolds R, Bond JP, Wallace SS. Probing the activity of NTHL1 orthologs by targeting conserved amino acid residues. DNA Repair (Amst) 2017; 53:43-51. [PMID: 28292631 PMCID: PMC5421317 DOI: 10.1016/j.dnarep.2017.02.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 02/01/2017] [Indexed: 01/01/2023]
Abstract
The base excision repair DNA glycosylases, EcoNth and hNTHL1, are homologous, with reported overlapping yet different substrate specificities. The catalytic amino acid residues are known and are identical between the two enzymes although the exact structures of the substrate binding pockets remain to be determined. We sought to explore the sequence basis of substrate differences using a phylogeny-based design of site-directed mutations. Mutations were made for each enzyme in the vicinity of the active site and we examined these variants for glycosylase and lyase activity. Single turnover kinetics were done on a subgroup of these, comparing activity on two lesions, 5,6-dihydrouracil and 5,6-dihydrothymine, with different opposite bases. We report that wild type hNTHL1 and EcoNth are remarkably alike with respect to the specificity of the glycosylase reaction, and although hNTHL1 is a much slower enzyme than EcoNth, the tighter binding of hNTHL1 compensates, resulting in similar kcat/Kd values for both enzymes with each of the substrates tested. For the hNTHL1 variant Gln287Ala, the specificity for substrates positioned opposite G is lost, but not that of substrates positioned opposite A, suggesting a discrimination role for this residue. The EcoNth Thr121 residue influences enzyme binding to DNA, as binding is significantly reduced with the Thr121Ala variant. Finally, we present evidence that hNTHL1 Asp144, unlike the analogous EcoNth residue Asp44, may be involved in resolving the glycosylase transition state.
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Affiliation(s)
- Susan M Robey-Bond
- Department of Microbiology and Molecular Genetics, The Markey Center for Molecular Genetics, University of Vermont, Stafford Hall, 95 Carrigan Drive, Burlington, VT 05405-0068, United States
| | - Meredith A Benson
- Department of Microbiology and Molecular Genetics, The Markey Center for Molecular Genetics, University of Vermont, Stafford Hall, 95 Carrigan Drive, Burlington, VT 05405-0068, United States
| | - Ramiro Barrantes-Reynolds
- Department of Microbiology and Molecular Genetics, The Markey Center for Molecular Genetics, University of Vermont, Stafford Hall, 95 Carrigan Drive, Burlington, VT 05405-0068, United States
| | - Jeffrey P Bond
- Department of Microbiology and Molecular Genetics, The Markey Center for Molecular Genetics, University of Vermont, Stafford Hall, 95 Carrigan Drive, Burlington, VT 05405-0068, United States
| | - Susan S Wallace
- Department of Microbiology and Molecular Genetics, The Markey Center for Molecular Genetics, University of Vermont, Stafford Hall, 95 Carrigan Drive, Burlington, VT 05405-0068, United States.
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14
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Ovchinnikov V, Nam K, Karplus M. A Simple and Accurate Method To Calculate Free Energy Profiles and Reaction Rates from Restrained Molecular Simulations of Diffusive Processes. J Phys Chem B 2016; 120:8457-72. [PMID: 27135391 DOI: 10.1021/acs.jpcb.6b02139] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A method is developed to obtain simultaneously free energy profiles and diffusion constants from restrained molecular simulations in diffusive systems. The method is based on low-order expansions of the free energy and diffusivity as functions of the reaction coordinate. These expansions lead to simple analytical relationships between simulation statistics and model parameters. The method is tested on 1D and 2D model systems; its accuracy is found to be comparable to or better than that of the existing alternatives, which are briefly discussed. An important aspect of the method is that the free energy is constructed by integrating its derivatives, which can be computed without need for overlapping sampling windows. The implementation of the method in any molecular simulation program that supports external umbrella potentials (e.g., CHARMM) requires modification of only a few lines of code. As a demonstration of its applicability to realistic biomolecular systems, the method is applied to model the α-helix ↔ β-sheet transition in a 16-residue peptide in implicit solvent, with the reaction coordinate provided by the string method. Possible modifications of the method are briefly discussed; they include generalization to multidimensional reaction coordinates [in the spirit of the model of Ermak and McCammon (Ermak, D. L.; McCammon, J. A. J. Chem. Phys. 1978, 69, 1352-1360)], a higher-order expansion of the free energy surface, applicability in nonequilibrium systems, and a simple test for Markovianity. In view of the small overhead of the method relative to standard umbrella sampling, we suggest its routine application in the cases where umbrella potential simulations are appropriate.
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Affiliation(s)
- Victor Ovchinnikov
- Department of Chemistry and Chemical Biology, Harvard University , Cambridge, Massachusetts 02138, United States
| | - Kwangho Nam
- Department of Chemistry, Umeå University , Umeå, Sweden , 901 87
| | - Martin Karplus
- Department of Chemistry and Chemical Biology, Harvard University , Cambridge, Massachusetts 02138, United States.,Laboratoire de Chimie Biophysique, ISIS, Université de Strasbourg , 67000 Strasbourg, France
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15
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Lee AJ, Wallace SS. Visualizing the Search for Radiation-damaged DNA Bases in Real Time. Radiat Phys Chem Oxf Engl 1993 2016; 128:126-133. [PMID: 27818579 DOI: 10.1016/j.radphyschem.2016.05.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The Base Excision Repair (BER) pathway removes the vast majority of damages produced by ionizing radiation, including the plethora of radiation-damaged purines and pyrimidines. The first enzymes in the BER pathway are DNA glycosylases, which are responsible for finding and removing the damaged base. Although much is known about the biochemistry of DNA glycosylases, how these enzymes locate their specific damage substrates among an excess of undamaged bases has long remained a mystery. Here we describe the use of single molecule fluorescence to observe the bacterial DNA glycosylases, Nth, Fpg and Nei, scanning along undamaged and damaged DNA. We show that all three enzymes randomly diffuse on the DNA molecule and employ a wedge residue to search for and locate damage. The search behavior of the Escherichia coli DNA glycosylases likely provides a paradigm for their homologous mammalian counterparts.
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Affiliation(s)
- Andrea J Lee
- Department of Microbiology and Molecular Genetics, The Markey Center for Molecular Genetics, The University of Vermont, 95 Carrigan Drive, Burlington, Vermont, 05405, USA
| | - Susan S Wallace
- Department of Microbiology and Molecular Genetics, The Markey Center for Molecular Genetics, The University of Vermont, 95 Carrigan Drive, Burlington, Vermont, 05405, USA
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16
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Kuznetsov NA, Kladova OA, Kuznetsova AA, Ishchenko AA, Saparbaev MK, Zharkov DO, Fedorova OS. Conformational Dynamics of DNA Repair by Escherichia coli Endonuclease III. J Biol Chem 2015; 290:14338-49. [PMID: 25869130 DOI: 10.1074/jbc.m114.621128] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Indexed: 11/06/2022] Open
Abstract
Escherichia coli endonuclease III (Endo III or Nth) is a DNA glycosylase with a broad substrate specificity for oxidized or reduced pyrimidine bases. Endo III possesses two types of activities: N-glycosylase (hydrolysis of the N-glycosidic bond) and AP lyase (elimination of the 3'-phosphate of the AP-site). We report a pre-steady-state kinetic analysis of structural rearrangements of the DNA substrates and uncleavable ligands during their interaction with Endo III. Oligonucleotide duplexes containing 5,6-dihydrouracil, a natural abasic site, its tetrahydrofuran analog, and undamaged duplexes carried fluorescent DNA base analogs 2-aminopurine and 1,3-diaza-2-oxophenoxazine as environment-sensitive reporter groups. The results suggest that Endo III induces several fast sequential conformational changes in DNA during binding, lesion recognition, and adjustment to a catalytically competent conformation. A comparison of two fluorophores allowed us to distinguish between the events occurring in the damaged and undamaged DNA strand. Combining our data with the available structures of Endo III, we conclude that this glycosylase uses a multistep mechanism of damage recognition, which likely involves Gln(41) and Leu(81) as DNA lesion sensors.
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Affiliation(s)
- Nikita A Kuznetsov
- From the Institute of Chemical Biology and Fundamental Medicine, 8 Lavrentyev Ave., Novosibirsk 630090, Russia, the Department of Natural Sciences, Novosibirsk State University, 2 Pirogova St., Novosibirsk 630090, Russia, and
| | - Olga A Kladova
- From the Institute of Chemical Biology and Fundamental Medicine, 8 Lavrentyev Ave., Novosibirsk 630090, Russia, the Department of Natural Sciences, Novosibirsk State University, 2 Pirogova St., Novosibirsk 630090, Russia, and
| | - Alexandra A Kuznetsova
- From the Institute of Chemical Biology and Fundamental Medicine, 8 Lavrentyev Ave., Novosibirsk 630090, Russia, the Department of Natural Sciences, Novosibirsk State University, 2 Pirogova St., Novosibirsk 630090, Russia, and
| | - Alexander A Ishchenko
- the Groupe "Réparation de l'ADN," Université Paris-Sud XI, UMR8200 CNRS, Institute Gustave Roussy, Villejuif Cedex F-94805, France
| | - Murat K Saparbaev
- the Groupe "Réparation de l'ADN," Université Paris-Sud XI, UMR8200 CNRS, Institute Gustave Roussy, Villejuif Cedex F-94805, France
| | - Dmitry O Zharkov
- From the Institute of Chemical Biology and Fundamental Medicine, 8 Lavrentyev Ave., Novosibirsk 630090, Russia, the Department of Natural Sciences, Novosibirsk State University, 2 Pirogova St., Novosibirsk 630090, Russia, and
| | - Olga S Fedorova
- From the Institute of Chemical Biology and Fundamental Medicine, 8 Lavrentyev Ave., Novosibirsk 630090, Russia, the Department of Natural Sciences, Novosibirsk State University, 2 Pirogova St., Novosibirsk 630090, Russia, and
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17
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Kuznetsov NA, Bergonzo C, Campbell AJ, Li H, Mechetin GV, de los Santos C, Grollman AP, Fedorova OS, Zharkov DO, Simmerling C. Active destabilization of base pairs by a DNA glycosylase wedge initiates damage recognition. Nucleic Acids Res 2014; 43:272-81. [PMID: 25520195 PMCID: PMC4288190 DOI: 10.1093/nar/gku1300] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Formamidopyrimidine-DNA glycosylase (Fpg) excises 8-oxoguanine (oxoG) from DNA but ignores normal guanine. We combined molecular dynamics simulation and stopped-flow kinetics with fluorescence detection to track the events in the recognition of oxoG by Fpg and its mutants with a key phenylalanine residue, which intercalates next to the damaged base, changed to either alanine (F110A) or fluorescent reporter tryptophan (F110W). Guanine was sampled by Fpg, as evident from the F110W stopped-flow traces, but less extensively than oxoG. The wedgeless F110A enzyme could bend DNA but failed to proceed further in oxoG recognition. Modeling of the base eversion with energy decomposition suggested that the wedge destabilizes the intrahelical base primarily through buckling both surrounding base pairs. Replacement of oxoG with abasic (AP) site rescued the activity, and calculations suggested that wedge insertion is not required for AP site destabilization and eversion. Our results suggest that Fpg, and possibly other DNA glycosylases, convert part of the binding energy into active destabilization of their substrates, using the energy differences between normal and damaged bases for fast substrate discrimination.
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Affiliation(s)
- Nikita A Kuznetsov
- SB RAS Institute of Chemical Biology and Fundamental Medicine, 8 Lavrentieva Ave., Novosibirsk 630090, Russia Department of Natural Sciences, Novosibirsk State University, 2 Pirogova St., Novosibirsk 630090, Russia
| | - Christina Bergonzo
- Department of Chemistry, Stony Brook University, Stony Brook, NY 11794, USA
| | - Arthur J Campbell
- Department of Chemistry, Stony Brook University, Stony Brook, NY 11794, USA
| | - Haoquan Li
- Department of Chemistry, Stony Brook University, Stony Brook, NY 11794, USA
| | - Grigory V Mechetin
- SB RAS Institute of Chemical Biology and Fundamental Medicine, 8 Lavrentieva Ave., Novosibirsk 630090, Russia
| | - Carlos de los Santos
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY 11794, USA
| | - Arthur P Grollman
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY 11794, USA
| | - Olga S Fedorova
- SB RAS Institute of Chemical Biology and Fundamental Medicine, 8 Lavrentieva Ave., Novosibirsk 630090, Russia Department of Natural Sciences, Novosibirsk State University, 2 Pirogova St., Novosibirsk 630090, Russia
| | - Dmitry O Zharkov
- SB RAS Institute of Chemical Biology and Fundamental Medicine, 8 Lavrentieva Ave., Novosibirsk 630090, Russia Department of Natural Sciences, Novosibirsk State University, 2 Pirogova St., Novosibirsk 630090, Russia
| | - Carlos Simmerling
- Department of Chemistry, Stony Brook University, Stony Brook, NY 11794, USA Laufer Center for Physical and Quantitative Biology, Stony Brook University, Stony Brook, NY 11794, USA
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18
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Cravens SL, Hobson M, Stivers JT. Electrostatic properties of complexes along a DNA glycosylase damage search pathway. Biochemistry 2014; 53:7680-92. [PMID: 25408964 PMCID: PMC4263432 DOI: 10.1021/bi501011m] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Human uracil DNA glycosylase (hUNG) follows an extended reaction coordinate for locating rare uracil bases in genomic DNA. This process begins with diffusion-controlled engagement of undamaged DNA, followed by a damage search step in which the enzyme remains loosely associated with the DNA chain (translocation), and finally, a recognition step that allows the enzyme to efficiently bind and excise uracil when it is encountered. At each step along this coordinate, the enzyme must form DNA interactions that are highly specialized for either rapid damage searching or catalysis. Here we make extensive measurements of hUNG activity as a function of salt concentration to dissect the thermodynamic, kinetic, and electrostatic properties of key enzyme states along this reaction coordinate. We find that the interaction of hUNG with undamaged DNA is electrostatically driven at a physiological concentration of potassium ions (ΔGelect = -3.5 ± 0.5 kcal mol(-1)), with only a small nonelectrostatic contribution (ΔGnon = -2.0 ± 0.2 kcal mol(-1)). In contrast, the interaction with damaged DNA is dominated by the nonelectrostatic free energy term (ΔGnon = -7.2 ± 0.1 kcal mol(-1)), yet retains the nonspecific electrostatic contribution (ΔGelect = -2.3 ± 0.2 kcal mol(-1)). Stopped-flow kinetic experiments established that the salt sensitivity of damaged DNA binding originates from a reduction of kon, while koff is weakly dependent on salt. Similar findings were obtained from the salt dependences of the steady-state kinetic parameters, where the diffusion-controlled kcat/Km showed a salt dependence similar to kon, while kcat (limited by product release) was weakly dependent on salt. Finally, the salt dependence of translocation between two uracil sites separated by 20 bp in the same DNA chain was indistinguishable from that of kon. This result suggests that the transition-state for translocation over this spacing resembles that for DNA association from bulk solution and that hUNG escapes the DNA ion cloud during translocation. These findings provide key insights into how the ionic environment in cells influences the DNA damage search pathway.
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Affiliation(s)
- Shannen L Cravens
- Department of Pharmacology and Molecular Sciences, The Johns Hopkins University School of Medicine , 725 North Wolfe Street, Baltimore, Maryland 21205-2185, United States
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19
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Two glycosylase families diffusively scan DNA using a wedge residue to probe for and identify oxidatively damaged bases. Proc Natl Acad Sci U S A 2014; 111:E2091-9. [PMID: 24799677 DOI: 10.1073/pnas.1400386111] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
DNA glycosylases are enzymes that perform the initial steps of base excision repair, the principal repair mechanism that identifies and removes endogenous damages that occur in an organism's DNA. We characterized the motion of single molecules of three bacterial glycosylases that recognize oxidized bases, Fpg, Nei, and Nth, as they scan for damages on tightropes of λ DNA. We find that all three enzymes use a key "wedge residue" to scan for damage because mutation of this residue to an alanine results in faster diffusion. Moreover, all three enzymes bind longer and diffuse more slowly on DNA that contains the damages they recognize and remove. Using a sliding window approach to measure diffusion constants and a simple chemomechanical simulation, we demonstrate that these enzymes diffuse along DNA, pausing momentarily to interrogate random bases, and when a damaged base is recognized, they stop to evert and excise it.
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20
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LeGresley SE, Wilt J, Antonik M. DNA damage may drive nucleosomal reorganization to facilitate damage detection. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2014; 89:032708. [PMID: 24730875 DOI: 10.1103/physreve.89.032708] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Indexed: 06/03/2023]
Abstract
One issue in genome maintenance is how DNA repair proteins find lesions at rates that seem to exceed diffusion-limited search rates. We propose a phenomenon where DNA damage induces nucleosomal rearrangements which move lesions to potential rendezvous points in the chromatin structure. These rendezvous points are the dyad and the linker DNA between histones, positions in the chromatin which are more likely to be accessible by repair proteins engaged in a random search. The feasibility of this mechanism is tested by considering the statistical mechanics of DNA containing a single lesion wrapped onto the nucleosome. We consider lesions which make the DNA either more flexible or more rigid by modeling the lesion as either a decrease or an increase in the bending energy. We include this energy in a partition function model of nucleosome breathing. Our results indicate that the steady state for a breathing nucleosome will most likely position the lesion at the dyad or in the linker, depending on the energy of the lesion. A role for DNA binding proteins and chromatin remodelers is suggested based on their ability to alter the mechanical properties of the DNA and DNA-histone binding, respectively. We speculate that these positions around the nucleosome potentially serve as rendezvous points where DNA lesions may be encountered by repair proteins which may be sterically hindered from searching the rest of the nucleosomal DNA. The strength of the repositioning is strongly dependent on the structural details of the DNA lesion and the wrapping and breathing of the nucleosome. A more sophisticated evaluation of this proposed mechanism will require detailed information about breathing dynamics, the structure of partially wrapped nucleosomes, and the structural properties of damaged DNA.
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Affiliation(s)
- Sarah E LeGresley
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, USA
| | - Jamie Wilt
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, USA
| | - Matthew Antonik
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, USA
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21
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Wallace SS. DNA glycosylases search for and remove oxidized DNA bases. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2013; 54:691-704. [PMID: 24123395 PMCID: PMC3997179 DOI: 10.1002/em.21820] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Revised: 09/04/2013] [Accepted: 09/05/2013] [Indexed: 05/19/2023]
Abstract
This review article presents, an overview of the DNA glycosylases that recognize oxidized DNA bases using the Fpg/Nei family of DNA glycosylases as models for how structure can inform function. For example, even though human NEIL1 and the plant and fungal orthologs lack the zinc finger shown to be required for binding, DNA crystal structures revealed a "zincless finger" with the same properties. Moreover, the "lesion recognition loop" is not involved in lesion recognition, rather, it stabilizes 8-oxoG in the active site pocket. Unlike the other Fpg/Nei family members, Neil3 lacks two of the three void-filling residues that stabilize the DNA duplex and interact with the opposite strand to the damage which may account for its preference for lesions in single-stranded DNA. Also single-molecule approaches show that DNA glycosylases search for their substrates in a sea of undamaged DNA by using a wedge residue that is inserted into the DNA helix to probe for the presence of damage.
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Affiliation(s)
- Susan S. Wallace
- Department of Microbiology and Molecular Genetics The Markey Center for Molecular Genetics The University of Vermont Stafford Hall, 95 Carrigan Drive Burlington, VT 05405-0068, USA Tel: (802) 656-2164; Fax: (802) 656-8749
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22
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Dršata T, Kara M, Zacharias M, Lankaš F. Effect of 8-oxoguanine on DNA structure and deformability. J Phys Chem B 2013; 117:11617-22. [PMID: 24028561 DOI: 10.1021/jp407562t] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
8-Oxoguanine (oxoG) is an abundant product of oxidative DNA damage. It is removed by repair glycosylases, but exactly how the enzymes recognize oxoG in the large surplus of undamaged bases is not fully understood. The lesion may induce changes in the properties of naked DNA that facilitate the recognition. In this work, we assess the effect of oxoG on DNA structure and mechanical deformability. We performed extensive unrestrained, atomic resolution molecular dynamics simulations to parametrize a nonlocal, rigid base mechanical model of DNA. Our data indicate that oxoG induces unwinding of the base pair step at the 5'-side of the lesion. This brings the damaged DNA closer to its conformation in the initial complex with bacterial glycosylase MutM. The untwisting is partially caused by different BII substate populations and is further enhanced by the base-sugar repulsion within oxoG. On the other hand, our analysis shows that damaged and undamaged DNA have very similar harmonic stiffness. These results suggest an indirect readout component of the MutM-DNA initial complex formation. They also help one to understand the effect of oxoG on the formation of nucleosomes and looped gene regulatory complexes.
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Affiliation(s)
- Tomáš Dršata
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic , Flemingovo náměstı́ 2, 166 10, Praha 6, Czech Republic
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23
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Parrilla-Doblas JT, Ponferrada-Marín MI, Roldán-Arjona T, Ariza RR. Early steps of active DNA demethylation initiated by ROS1 glycosylase require three putative helix-invading residues. Nucleic Acids Res 2013; 41:8654-64. [PMID: 23868090 PMCID: PMC3794587 DOI: 10.1093/nar/gkt625] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Active DNA demethylation is crucial for epigenetic control, but the underlying enzymatic mechanisms are incompletely understood. REPRESSOR OF SILENCING 1 (ROS1) is a 5-methylcytosine (5-meC) DNA glycosylase/lyase that initiates DNA demethylation in plants through a base excision repair process. The enzyme binds DNA nonspecifically and slides along the substrate in search of 5-meC. In this work, we have used homology modelling and biochemical analysis to gain insight into the mechanism of target location and recognition by ROS1. We have found that three putative helix-intercalating residues (Q607, R903 and M905) are required for processing of 5-meC:G pairs, but dispensable for excision of mismatched 5-meC. Mutant proteins Q607A, R903A and M905G retain the capacity to process an abasic site opposite G, thus suggesting that all three residues play a critical role in early steps of the base extrusion process and likely contribute to destabilization of 5-meC:G pairs. While R903 and M905 are not essential for DNA binding, mutation of Q607 abrogates stable binding to both methylated and nonmethylated DNA. However, the mutant protein Q607A can form stable complexes with DNA substrates containing blocked ends, which suggests that Q607 intercalates into the helix and inhibits sliding. Altogether, our results suggest that ROS1 uses three predicted helix-invading residues to actively interrogate DNA in search for 5-meC.
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Affiliation(s)
- Jara Teresa Parrilla-Doblas
- Department of Genetics, University of Córdoba/Maimónides Institute for Research in Biomedicine of Córdoba (IMIBIC)/Reina Sofía University Hospital, 14071 Córdoba, Spain
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24
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Schonhoft JD, Kosowicz JG, Stivers JT. DNA translocation by human uracil DNA glycosylase: role of DNA phosphate charge. Biochemistry 2013; 52:2526-35. [PMID: 23506309 DOI: 10.1021/bi301561d] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Human DNA repair glycosylases must encounter and inspect each DNA base in the genome to discover damaged bases that may be present at a density of <1 in 10 million normal base pairs. This remarkable example of specific molecular recognition requires a reduced dimensionality search process (facilitated diffusion) that involves both hopping and sliding along the DNA chain. Despite the widely accepted importance of facilitated diffusion in protein-DNA interactions, the molecular features of DNA that influence hopping and sliding are poorly understood. Here we explore the role of the charged DNA phosphate backbone in sliding and hopping by human uracil DNA glycosylase (hUNG), which is an exemplar that efficiently locates rare uracil bases in both double-stranded DNA and single-stranded DNA. Substitution of neutral methylphosphonate groups for anionic DNA phosphate groups weakened nonspecific DNA binding affinity by 0.4-0.5 kcal/mol per substitution. In contrast, sliding of hUNG between uracil sites embedded in duplex and single-stranded DNA substrates persisted unabated when multiple methylphosphonate linkages were inserted between the sites. Thus, a continuous phosphodiester backbone negative charge is not essential for sliding over nonspecific DNA binding sites. We consider several alternative mechanisms for these results. A model consistent with previous structural and nuclear magnetic resonance dynamic results invokes the presence of open and closed conformational states of hUNG. The open state is short-lived and has weak or nonexistent interactions with the DNA backbone that are conducive for sliding, and the populated closed state has stronger interactions with the phosphate backbone. These data suggest that the fleeting sliding form of hUNG is a distinct weakly interacting state that facilitates rapid movement along the DNA chain and resembles the transition state for DNA dissociation.
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Affiliation(s)
- Joseph D Schonhoft
- Department of Pharmacology and Molecular Sciences, The Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, Maryland 21205-2185, USA
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25
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Abstract
Base excision repair (BER) is a frontline repair system that is responsible for maintaining genome integrity and thus preventing premature aging, cancer and many other human diseases by repairing thousands of DNA lesions and strand breaks continuously caused by endogenous and exogenous mutagens. This fundamental and essential function of BER not only necessitates tight control of the continuous availability of basic components for fast and accurate repair, but also requires temporal and spatial coordination of BER and cell cycle progression to prevent replication of damaged DNA. The major goal of this review is to critically examine controversial and newly emerging questions about mammalian BER pathways, mechanisms regulating BER capacity, BER responses to DNA damage and their links to checkpoint control of DNA replication.
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Affiliation(s)
- Grigory L Dianov
- Department of Oncology, Gray Institute for Radiation Oncology and Biology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK.
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26
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Sung RJ, Zhang M, Qi Y, Verdine GL. Structural and biochemical analysis of DNA helix invasion by the bacterial 8-oxoguanine DNA glycosylase MutM. J Biol Chem 2013; 288:10012-10023. [PMID: 23404556 DOI: 10.1074/jbc.m112.415612] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
MutM is a bacterial DNA glycosylase that serves as the first line of defense against the highly mutagenic 8-oxoguanine (oxoG) lesion, catalyzing glycosidic bond cleavage of oxoG to initiate base excision DNA repair. Previous work has shown that MutM actively interrogates DNA for the presence of an intrahelical oxoG lesion. This interrogation process involves significant buckling and bending of the DNA to promote extrusion of oxoG from the duplex. Structural snapshots have revealed several different highly conserved residues that are prominently inserted into the duplex in the vicinity of the target oxoG before and after base extrusion has occurred. However, the roles of these helix-invading residues during the lesion recognition and base extrusion process remain unclear. In this study, we set out to probe the function of residues Phe(114) and Met(77) in oxoG recognition and repair. Here we report a detailed biochemical and structural characterization of MutM variants containing either a F114A or M77A mutation, both of which showed significant decreases in the efficiency of oxoG repair. These data reveal that Met(77) plays an important role in stabilizing the lesion-extruded conformation of the DNA. Phe(114), on the other hand, appears to destabilize the intrahelical state of the oxoG lesion, primarily by buckling the target base pair. We report the observation of a completely unexpected interaction state, in which the target base pair is ruptured but remains fully intrahelical; this structure vividly illustrates the disruptive influence of MutM on the target base pair.
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Affiliation(s)
- Rou-Jia Sung
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138; Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, Massachusetts 02138
| | - Michael Zhang
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138
| | - Yan Qi
- Graduate Program in Biophysics, Harvard Medical School, Boston, Massachusetts 02115
| | - Gregory L Verdine
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138; Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, Massachusetts 02138; Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138; Chemical Biology Initiative and Program in Cancer Chemical Biology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115.
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27
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Odell ID, Wallace SS, Pederson DS. Rules of engagement for base excision repair in chromatin. J Cell Physiol 2013; 228:258-66. [PMID: 22718094 DOI: 10.1002/jcp.24134] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Most of the DNA in eukaryotes is packaged in tandemly arrayed nucleosomes that, together with numerous DNA- and nucleosome-associated enzymes and regulatory factors, make up chromatin. Chromatin modifying and remodeling agents help regulate access to selected DNA segments in chromatin, thereby facilitating transcription and DNA replication and repair. Studies of nucleotide excision repair (NER), single strand break repair (SSBR), and the homology-directed repair (HDR), and non-homologous end-joining (NHEJ) double strand break repair pathways have led to an "access-repair-restore" paradigm, in which chromatin in the vicinity of damaged DNA is disrupted, thereby enabling efficient repair and the subsequent repackaging of DNA into nucleosomes. When damage is extensive, these repair processes are accompanied by cell cycle checkpoint activation, which provides cells with sufficient time to either complete the repair or initiate apoptosis. It is not clear, however, if base excision repair (BER) of the ~20,000 or more oxidative DNA damages that occur daily in each nucleated human cell can be viewed through this same lens. Until recently, we did not know if BER requires or is accompanied by nucleosome disruption, and it is not yet clear that anything short of overwhelming oxidative damage (resulting in the shunting of DNA substrates into other repair pathways) results in checkpoint activation. This review highlights studies of how oxidatively damaged DNA in nucleosomes is discovered and repaired, and offers a working model of events associated with BER in chromatin that we hope will have heuristic value.
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Affiliation(s)
- Ian D Odell
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont 05405, USA
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