1
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Fairlamb MS, Spies M, Washington MT, Freudenthal BD. Visualizing the coordination of apurinic/apyrimidinic endonuclease (APE1) and DNA polymerase β during base excision repair. J Biol Chem 2023; 299:104636. [PMID: 36963489 PMCID: PMC10148159 DOI: 10.1016/j.jbc.2023.104636] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2023] [Revised: 03/05/2023] [Accepted: 03/10/2023] [Indexed: 03/26/2023] Open
Abstract
Base excision repair (BER) is carried out by a series of proteins that function in a step-by-step process to identify, remove, and replace DNA damage. During BER, the DNA transitions through various intermediate states as it is processed by each DNA repair enzyme. Left unrepaired, these BER intermediates can transition into double-stranded DNA breaks and promote genome instability. Previous studies have proposed a short-lived complex consisting of the BER intermediate, the incoming enzyme, and the outgoing enzyme at each step of the BER pathway to protect the BER intermediate. The transfer of BER intermediates between enzymes, known as BER coordination or substrate channeling, remains poorly understood. Here, we utilize single-molecule total internal reflection fluorescence microscopy to investigate the mechanism of BER coordination between apurinic/apyrimidinic endonuclease 1 (APE1) and DNA polymerase β (Pol β). When preformed complexes of APE1 and the incised abasic site product (APE1 product and Pol β substrate) were subsequently bound by Pol β, the Pol β enzyme dissociated shortly after binding in most of the observations. In the events where Pol β binding was followed by APE1 dissociation during substrate channeling, Pol β remained bound for a longer period of time to allow disassociation of APE1. Our results indicate that transfer of the BER intermediate from APE1 to Pol β during BER is dependent on the dissociation kinetics of APE1 and the duration of the ternary complex on the incised abasic site.
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Affiliation(s)
- Max S Fairlamb
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, Kansas, USA
| | - Maria Spies
- Department of Biochemistry and Molecular Biology, University of Iowa Carver College of Medicine, Iowa City, Iowa, USA
| | - M Todd Washington
- Department of Biochemistry and Molecular Biology, University of Iowa Carver College of Medicine, Iowa City, Iowa, USA
| | - Bret D Freudenthal
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, Kansas, USA; Department of Cancer Biology, University of Kansas Medical Center, Kansas City, Kansas, USA; University of Kansas Cancer Center, Kansas City, Kansas, USA.
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2
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Chinnam NB, Syed A, Burnett KH, Hura GL, Tainer JA, Tsutakawa SE. Universally Accessible Structural Data on Macromolecular Conformation, Assembly, and Dynamics by Small Angle X-Ray Scattering for DNA Repair Insights. Methods Mol Biol 2022; 2444:43-68. [PMID: 35290631 PMCID: PMC9020468 DOI: 10.1007/978-1-0716-2063-2_4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Structures provide a critical breakthrough step for biological analyses, and small angle X-ray scattering (SAXS) is a powerful structural technique to study dynamic DNA repair proteins. As toxic and mutagenic repair intermediates need to be prevented from inadvertently harming the cell, DNA repair proteins often chaperone these intermediates through dynamic conformations, coordinated assemblies, and allosteric regulation. By measuring structural conformations in solution for both proteins, DNA, RNA, and their complexes, SAXS provides insight into initial DNA damage recognition, mechanisms for validation of their substrate, and pathway regulation. Here, we describe exemplary SAXS analyses of a DNA damage response protein spanning from what can be derived directly from the data to obtaining super resolution through the use of SAXS selection of atomic models. We outline strategies and tactics for practical SAXS data collection and analysis. Making these structural experiments in reach of any basic and clinical researchers who have protein, SAXS data can readily be collected at government-funded synchrotrons, typically at no cost for academic researchers. In addition to discussing how SAXS complements and enhances cryo-electron microscopy, X-ray crystallography, NMR, and computational modeling, we furthermore discuss taking advantage of recent advances in protein structure prediction in combination with SAXS analysis.
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Affiliation(s)
- Naga Babu Chinnam
- Department of Molecular and Cellular Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, TX, USA
| | - Aleem Syed
- Department of Molecular and Cellular Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, TX, USA
| | - Kathryn H Burnett
- Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Greg L Hura
- Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Chemistry and Biochemistry Department, University of California Santa Cruz, Santa Cruz, CA, USA
| | - John A Tainer
- Department of Molecular and Cellular Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, TX, USA
- Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Department of Cancer Biology, University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Susan E Tsutakawa
- Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
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3
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Thompson MK, Sobol RW, Prakash A. Exploiting DNA Endonucleases to Advance Mechanisms of DNA Repair. BIOLOGY 2021; 10:530. [PMID: 34198612 PMCID: PMC8232306 DOI: 10.3390/biology10060530] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 06/09/2021] [Accepted: 06/11/2021] [Indexed: 12/17/2022]
Abstract
The earliest methods of genome editing, such as zinc-finger nucleases (ZFN) and transcription activator-like effector nucleases (TALENs), utilize customizable DNA-binding motifs to target the genome at specific loci. While these approaches provided sequence-specific gene-editing capacity, the laborious process of designing and synthesizing recombinant nucleases to recognize a specific target sequence, combined with limited target choices and poor editing efficiency, ultimately minimized the broad utility of these systems. The discovery of clustered regularly interspaced short palindromic repeat sequences (CRISPR) in Escherichia coli dates to 1987, yet it was another 20 years before CRISPR and the CRISPR-associated (Cas) proteins were identified as part of the microbial adaptive immune system, by targeting phage DNA, to fight bacteriophage reinfection. By 2013, CRISPR/Cas9 systems had been engineered to allow gene editing in mammalian cells. The ease of design, low cytotoxicity, and increased efficiency have made CRISPR/Cas9 and its related systems the designer nucleases of choice for many. In this review, we discuss the various CRISPR systems and their broad utility in genome manipulation. We will explore how CRISPR-controlled modifications have advanced our understanding of the mechanisms of genome stability, using the modulation of DNA repair genes as examples.
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Affiliation(s)
- Marlo K. Thompson
- Mitchell Cancer Institute, University of South Alabama Health, Mobile, AL 36604, USA; (M.K.T.); (R.W.S.)
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, AL 36688, USA
| | - Robert W. Sobol
- Mitchell Cancer Institute, University of South Alabama Health, Mobile, AL 36604, USA; (M.K.T.); (R.W.S.)
- Department of Pharmacology, University of South Alabama, Mobile, AL 36688, USA
| | - Aishwarya Prakash
- Mitchell Cancer Institute, University of South Alabama Health, Mobile, AL 36604, USA; (M.K.T.); (R.W.S.)
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, AL 36688, USA
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4
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Kavli B, Iveland TS, Buchinger E, Hagen L, Liabakk NB, Aas PA, Obermann TS, Aachmann FL, Slupphaug G. RPA2 winged-helix domain facilitates UNG-mediated removal of uracil from ssDNA; implications for repair of mutagenic uracil at the replication fork. Nucleic Acids Res 2021; 49:3948-3966. [PMID: 33784377 PMCID: PMC8053108 DOI: 10.1093/nar/gkab195] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 03/04/2021] [Accepted: 03/10/2021] [Indexed: 01/14/2023] Open
Abstract
Uracil occurs at replication forks via misincorporation of deoxyuridine monophosphate (dUMP) or via deamination of existing cytosines, which occurs 2-3 orders of magnitude faster in ssDNA than in dsDNA and is 100% miscoding. Tethering of UNG2 to proliferating cell nuclear antigen (PCNA) allows rapid post-replicative removal of misincorporated uracil, but potential 'pre-replicative' removal of deaminated cytosines in ssDNA has been questioned since this could mediate mutagenic translesion synthesis and induction of double-strand breaks. Here, we demonstrate that uracil-DNA glycosylase (UNG), but not SMUG1 efficiently excises uracil from replication protein A (RPA)-coated ssDNA and that this depends on functional interaction between the flexible winged-helix (WH) domain of RPA2 and the N-terminal RPA-binding helix in UNG. This functional interaction is promoted by mono-ubiquitination and diminished by cell-cycle regulated phosphorylations on UNG. Six other human proteins bind the RPA2-WH domain, all of which are involved in DNA repair and replication fork remodelling. Based on this and the recent discovery of the AP site crosslinking protein HMCES, we propose an integrated model in which templated repair of uracil and potentially other mutagenic base lesions in ssDNA at the replication fork, is orchestrated by RPA. The UNG:RPA2-WH interaction may also play a role in adaptive immunity by promoting efficient excision of AID-induced uracils in transcribed immunoglobulin loci.
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Affiliation(s)
- Bodil Kavli
- Department of Clinical and Molecular Medicine, NTNU Norwegian University of Science and Technology, NO-7491 Trondheim, Norway.,Clinic of Laboratory Medicine, St. Olavs Hospital, Trondheim University Hospital, NO-7006 Trondheim, Norway
| | - Tobias S Iveland
- Department of Clinical and Molecular Medicine, NTNU Norwegian University of Science and Technology, NO-7491 Trondheim, Norway.,Cancer Clinic, St. Olavs Hospital, Trondheim University Hospital, NO-7006 Trondheim, Norway
| | - Edith Buchinger
- NOBIPOL, Department of Biotechnology and Food Science, NTNU Norwegian University of Science and Technology, N-7034 Trondheim, Norway
| | - Lars Hagen
- Department of Clinical and Molecular Medicine, NTNU Norwegian University of Science and Technology, NO-7491 Trondheim, Norway.,Clinic of Laboratory Medicine, St. Olavs Hospital, Trondheim University Hospital, NO-7006 Trondheim, Norway.,PROMEC Proteomics and Modomics Experimental Core at NTNU and the Central Norway Regional Health Authority, NO-7491 Trondheim, Norway
| | - Nina B Liabakk
- Department of Clinical and Molecular Medicine, NTNU Norwegian University of Science and Technology, NO-7491 Trondheim, Norway.,Clinic of Laboratory Medicine, St. Olavs Hospital, Trondheim University Hospital, NO-7006 Trondheim, Norway
| | - Per A Aas
- Department of Clinical and Molecular Medicine, NTNU Norwegian University of Science and Technology, NO-7491 Trondheim, Norway.,Clinic of Laboratory Medicine, St. Olavs Hospital, Trondheim University Hospital, NO-7006 Trondheim, Norway
| | - Tobias S Obermann
- Department of Clinical and Molecular Medicine, NTNU Norwegian University of Science and Technology, NO-7491 Trondheim, Norway.,Clinic of Laboratory Medicine, St. Olavs Hospital, Trondheim University Hospital, NO-7006 Trondheim, Norway
| | - Finn L Aachmann
- NOBIPOL, Department of Biotechnology and Food Science, NTNU Norwegian University of Science and Technology, N-7034 Trondheim, Norway
| | - Geir Slupphaug
- Department of Clinical and Molecular Medicine, NTNU Norwegian University of Science and Technology, NO-7491 Trondheim, Norway.,Clinic of Laboratory Medicine, St. Olavs Hospital, Trondheim University Hospital, NO-7006 Trondheim, Norway.,PROMEC Proteomics and Modomics Experimental Core at NTNU and the Central Norway Regional Health Authority, NO-7491 Trondheim, Norway
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5
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Nguyen MT, Moiani D, Ahmed Z, Arvai AS, Namjoshi S, Shin DS, Fedorov Y, Selvik EJ, Jones DE, Pink J, Yan Y, Laverty DJ, Nagel ZD, Tainer JA, Gerson SL. An effective human uracil-DNA glycosylase inhibitor targets the open pre-catalytic active site conformation. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2021; 163:143-159. [PMID: 33675849 PMCID: PMC8722130 DOI: 10.1016/j.pbiomolbio.2021.02.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 02/13/2021] [Accepted: 02/22/2021] [Indexed: 02/07/2023]
Abstract
Human uracil DNA-glycosylase (UDG) is the prototypic and first identified DNA glycosylase with a vital role in removing deaminated cytosine and incorporated uracil and 5-fluorouracil (5-FU) from DNA. UDG depletion sensitizes cells to high APOBEC3B deaminase and to pemetrexed (PEM) and floxuridine (5-FdU), which are toxic to tumor cells through incorporation of uracil and 5-FU into DNA. To identify small-molecule UDG inhibitors for pre-clinical evaluation, we optimized biochemical screening of a selected diversity collection of >3,000 small-molecules. We found aurintricarboxylic acid (ATA) as an inhibitor of purified UDG at an initial calculated IC50 < 100 nM. Subsequent enzymatic assays confirmed effective ATA inhibition but with an IC50 of 700 nM and showed direct binding to the human UDG with a KD of <700 nM. ATA displays preferential, dose-dependent binding to purified human UDG compared to human 8-oxoguanine DNA glycosylase. ATA did not bind uracil-containing DNA at these concentrations. Yet, combined crystal structure and in silico docking results unveil ATA interactions with the DNA binding channel and uracil-binding pocket in an open, destabilized UDG conformation. Biologically relevant ATA inhibition of UDG was measured in cell lysates from human DLD1 colon cancer cells and in MCF-7 breast cancer cells using a host cell reactivation assay. Collective findings provide proof-of-principle for development of an ATA-based chemotype and “door stopper” strategy targeting inhibitor binding to a destabilized, open pre-catalytic glycosylase conformation that prevents active site closing for functional DNA binding and nucleotide flipping needed to excise altered bases in DNA.
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Affiliation(s)
- My T Nguyen
- Case Western Reserve University, Department of Biochemistry, Cleveland, OH, 44106, USA
| | - Davide Moiani
- Departments of Cancer Biology and of Molecular & Cellular Oncology, University of Texas MD Anderson Cancer Center, 1515 Holcomb Blvd, Houston, TX, 77030, USA
| | - Zamal Ahmed
- Departments of Cancer Biology and of Molecular & Cellular Oncology, University of Texas MD Anderson Cancer Center, 1515 Holcomb Blvd, Houston, TX, 77030, USA
| | - Andrew S Arvai
- Integrative Structural & Computational Biology, The Scripps Research Institute, La Jolla, CA, 92037, USA
| | - Sarita Namjoshi
- Departments of Cancer Biology and of Molecular & Cellular Oncology, University of Texas MD Anderson Cancer Center, 1515 Holcomb Blvd, Houston, TX, 77030, USA
| | - Dave S Shin
- Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Yuriy Fedorov
- Case Small-Molecule Screening Core, School of Medicine, Case Western Reserve University, Cleveland, OH, 44016, USA
| | - Edward J Selvik
- Department of Pharmaceutical Sciences, The University of Arkansas for Medical Sciences, 4301 West Markham Street, Little Rock, AR, 72205, USA
| | - Darin E Jones
- Department of Pharmaceutical Sciences, The University of Arkansas for Medical Sciences, 4301 West Markham Street, Little Rock, AR, 72205, USA
| | - John Pink
- Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Yan Yan
- Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Daniel J Laverty
- Department of Environmental Health, Harvard TH Chan School of Public Health, Boston, MA, 02115, USA
| | - Zachary D Nagel
- Department of Environmental Health, Harvard TH Chan School of Public Health, Boston, MA, 02115, USA
| | - John A Tainer
- Departments of Cancer Biology and of Molecular & Cellular Oncology, University of Texas MD Anderson Cancer Center, 1515 Holcomb Blvd, Houston, TX, 77030, USA; Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
| | - Stanton L Gerson
- Case Western Reserve University, Department of Biochemistry, Cleveland, OH, 44106, USA; Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, OH, 44106, USA.
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6
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Raper AT, Maxwell BA, Suo Z. Dynamic Processing of a Common Oxidative DNA Lesion by the First Two Enzymes of the Base Excision Repair Pathway. J Mol Biol 2021; 433:166811. [PMID: 33450252 DOI: 10.1016/j.jmb.2021.166811] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2020] [Revised: 12/23/2020] [Accepted: 01/02/2021] [Indexed: 01/25/2023]
Abstract
Base excision repair (BER) is the primary pathway by which eukaryotic cells resolve single base damage. One common example of single base damage is 8-oxo-7,8-dihydro-2'-deoxoguanine (8-oxoG). High incidence and mutagenic potential of 8-oxoG necessitate rapid and efficient DNA repair. How BER enzymes coordinate their activities to resolve 8-oxoG damage while limiting cytotoxic BER intermediates from propagating genomic instability remains unclear. Here we use single-molecule Förster resonance energy transfer (smFRET) and ensemble-level techniques to characterize the activities and interactions of consecutive BER enzymes important for repair of 8-oxoG. In addition to characterizing the damage searching and processing mechanisms of human 8-oxoguanine glycosylase 1 (hOGG1), our data support the existence of a ternary complex between hOGG1, the damaged DNA substrate, and human AP endonuclease 1 (APE1). Our results indicate that hOGG1 is actively displaced from its abasic site containing product by protein-protein interactions with APE1 to ensure timely repair of damaged DNA.
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Affiliation(s)
- Austin T Raper
- The Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA
| | - Brian A Maxwell
- The Ohio State Biophysics Ph.D. Program, The Ohio State University, Columbus, OH 43210, USA
| | - Zucai Suo
- The Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA; The Ohio State Biophysics Ph.D. Program, The Ohio State University, Columbus, OH 43210, USA; Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL 32306, USA.
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7
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Pol β gap filling, DNA ligation and substrate-product channeling during base excision repair opposite oxidized 5-methylcytosine modifications. DNA Repair (Amst) 2020; 95:102945. [PMID: 32853828 DOI: 10.1016/j.dnarep.2020.102945] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Revised: 07/07/2020] [Accepted: 07/24/2020] [Indexed: 12/13/2022]
Abstract
DNA methylation on cytosine in CpG islands generates 5-methylcytosine (5mC), and further modification of 5mC can result in the oxidized variants 5-hydroxymethyl (5hmC), 5-formyl (5fC), and 5-carboxy (5caC). Base excision repair (BER) is crucial for both genome maintenance and active DNA demethylation of modified cytosine products and involves substrate-product channeling from nucleotide insertion by DNA polymerase (pol) β to the subsequent ligation step. Here, we report that, in contrast to the pol β mismatch insertion products (dCTP, dATP, and dTTP), the nicked products after pol β dGTP insertion can be ligated by DNA ligase I or DNA ligase III/XRCC1 complex when a 5mC oxidation modification is present opposite in the template position in vitro. A Pol β K280A mutation, which perturbates the stabilization of these base modifications within the active site, hinders the BER ligases. Moreover, the nicked repair intermediates that mimic pol β mismatch insertion products, i.e., with 3'-preinserted dGMP or dTMP opposite templating 5hmC, 5fC or 5caC, can be efficiently ligated, whereas preinserted 3'-dAMP or dCMP mismatches result in failed ligation reactions. These findings herein contribute to our understanding of the insertion tendencies of pol β opposite different cytosine base forms, the ligation properties of DNA ligase I and DNA ligase III/XRCC1 complex in the context of gapped and nicked damage-containing repair intermediates, and the efficiency and fidelity of substrate channeling during the final steps of BER in situations involving oxidative 5mC base modifications in the template strand.
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8
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Biochemical and Cellular Assays to Assess the Effects of Acetylation on Base Excision Repair Enzymes. Methods Mol Biol 2020. [PMID: 31087299 DOI: 10.1007/978-1-4939-9434-2_11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Protein posttranslational modifications (PTMs), including acetylation, have emerged as important regulators for controlling many cellular processes. DNA base excision repair (BER), a highly coordinated multistep cellular process, is primarily involved in the repair of both endogenous and drug-induced exogenous DNA base damages. BER relies on sequential recruitment and coordinated actions of multiple proteins. Increasing evidence suggests that acetylation of lysine residues of BER proteins facilitates fine-tuning of enzymatic activities, protein-protein interactions, and coordination of the steps in BER pathway. In this chapter, we describe detailed in vitro and in vivo approaches to examine the effect of acetylation on BER enzymes, focusing on the impact of acetylation of AP-endonuclease (APE1), a key enzyme in BER pathway, on its DNA damage repair activity, substrate-binding, and subcellular localization.
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9
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Brosey CA, Tainer JA. Evolving SAXS versatility: solution X-ray scattering for macromolecular architecture, functional landscapes, and integrative structural biology. Curr Opin Struct Biol 2019; 58:197-213. [PMID: 31204190 PMCID: PMC6778498 DOI: 10.1016/j.sbi.2019.04.004] [Citation(s) in RCA: 106] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Revised: 04/10/2019] [Accepted: 04/15/2019] [Indexed: 11/27/2022]
Abstract
Small-angle X-ray scattering (SAXS) has emerged as an enabling
integrative technique for comprehensive analyses of macromolecular structures
and interactions in solution. Over the past two decades, SAXS has become a
mainstay of the structural biologist’s toolbox, supplying multiplexed
measurements of molecular shape and dynamics that unveil biological function.
Here, we discuss evolving SAXS theory, methods, and applications that extend the
field of small-angle scattering beyond simple shape characterization. SAXS,
coupled with size-exclusion chromatography (SEC-SAXS) and time-resolved
(TR-SAXS) methods, is now providing high-resolution insight into macromolecular
flexibility and ensembles, delineating biophysical landscapes, and facilitating
high-throughput library screening to assess macromolecular properties and to
create opportunities for drug discovery. Looking forward, we consider SAXS in
the integrative era of hybrid structural biology methods, its potential for
illuminating cellular supramolecular and mesoscale structures, and its capacity
to complement high-throughput bioinformatics sequencing data. As advances in the
field continue, we look forward to proliferating uses of SAXS based upon its
abilities to robustly produce mechanistic insights for biology and medicine.
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Affiliation(s)
- Chris A Brosey
- Molecular and Cellular Oncology and Cancer Biology, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
| | - John A Tainer
- Molecular and Cellular Oncology and Cancer Biology, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA; MBIB Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
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10
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Tainer JA. Uncovering the secrets of protein interactions with the DNA enforcing genomic stability. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2017; 127:89-92. [PMID: 28709479 DOI: 10.1016/j.pbiomolbio.2017.07.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- John A Tainer
- Department of Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Holcombe Blvd., Houston, TX 77030, United States; SIBYLS, Advanced Light Source, Lawrence Berkeley National Lab, United States. http://bl1231.als.lbl.gov
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11
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Banda DM, Nuñez NN, Burnside MA, Bradshaw KM, David SS. Repair of 8-oxoG:A mismatches by the MUTYH glycosylase: Mechanism, metals and medicine. Free Radic Biol Med 2017; 107:202-215. [PMID: 28087410 PMCID: PMC5457711 DOI: 10.1016/j.freeradbiomed.2017.01.008] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Revised: 01/01/2017] [Accepted: 01/04/2017] [Indexed: 12/12/2022]
Abstract
Reactive oxygen and nitrogen species (RONS) may infringe on the passing of pristine genetic information by inducing DNA inter- and intra-strand crosslinks, protein-DNA crosslinks, and chemical alterations to the sugar or base moieties of DNA. 8-Oxo-7,8-dihydroguanine (8-oxoG) is one of the most prevalent DNA lesions formed by RONS and is repaired through the base excision repair (BER) pathway involving the DNA repair glycosylases OGG1 and MUTYH in eukaryotes. MUTYH removes adenine (A) from 8-oxoG:A mispairs, thus mitigating the potential of G:C to T:A transversion mutations from occurring in the genome. The paramount role of MUTYH in guarding the genome is well established in the etiology of a colorectal cancer predisposition syndrome involving variants of MUTYH, referred to as MUTYH-associated polyposis (MAP). In this review, we highlight recent advances in understanding how MUTYH structure and related function participate in the manifestation of human disease such as MAP. Here we focus on the importance of MUTYH's metal cofactor sites, including a recently discovered "Zinc linchpin" motif, as well as updates to the catalytic mechanism. Finally, we touch on the insight gleaned from studies with MAP-associated MUTYH variants and recent advances in understanding the multifaceted roles of MUTYH in the cell, both in the prevention of mutagenesis and tumorigenesis.
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Affiliation(s)
- Douglas M Banda
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, CA 95616, United States
| | - Nicole N Nuñez
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, CA 95616, United States
| | - Michael A Burnside
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, CA 95616, United States
| | - Katie M Bradshaw
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, CA 95616, United States
| | - Sheila S David
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, CA 95616, United States.
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12
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Brosey CA, Ahmed Z, Lees-Miller SP, Tainer JA. What Combined Measurements From Structures and Imaging Tell Us About DNA Damage Responses. Methods Enzymol 2017; 592:417-455. [PMID: 28668129 DOI: 10.1016/bs.mie.2017.04.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
DNA damage outcomes depend upon the efficiency and fidelity of DNA damage responses (DDRs) for different cells and damage. As such, DDRs represent tightly regulated prototypical systems for linking nanoscale biomolecular structure and assembly to the biology of genomic regulation and cell signaling. However, the dynamic and multifunctional nature of DDR assemblies can render elusive the correlation between the structures of DDR factors and specific biological disruptions to the DDR when these structures are altered. In this chapter, we discuss concepts and strategies for combining structural, biophysical, and imaging techniques to investigate DDR recognition and regulation, and thus bridge sequence-level structural biochemistry to quantitative biological outcomes visualized in cells. We focus on representative DDR responses from PARP/PARG/AIF damage signaling in DNA single-strand break repair and nonhomologous end joining complexes in double-strand break repair. Methods with exemplary experimental results are considered with a focus on strategies for probing flexibility, conformational changes, and assembly processes that shape a predictive understanding of DDR mechanisms in a cellular context. Integration of structural and imaging measurements promises to provide foundational knowledge to rationally control and optimize DNA damage outcomes for synthetic lethality and for immune activation with resulting insights for biology and cancer interventions.
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Affiliation(s)
- Chris A Brosey
- The University of Texas, M.D. Anderson Cancer Center, Houston, TX, United States
| | - Zamal Ahmed
- The University of Texas, M.D. Anderson Cancer Center, Houston, TX, United States
| | - Susan P Lees-Miller
- Robson DNA Science Centre, Arnie Charbonneau Cancer Institute, University of Calgary, Calgary, AB, Canada.
| | - John A Tainer
- The University of Texas, M.D. Anderson Cancer Center, Houston, TX, United States; Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA, United States.
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13
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Exell JC, Thompson MJ, Finger LD, Shaw SJ, Debreczeni J, Ward TA, McWhirter C, Siöberg CLB, Martinez Molina D, Abbott WM, Jones CD, Nissink JWM, Durant ST, Grasby JA. Cellularly active N-hydroxyurea FEN1 inhibitors block substrate entry to the active site. Nat Chem Biol 2016; 12:815-21. [PMID: 27526030 PMCID: PMC5348030 DOI: 10.1038/nchembio.2148] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Accepted: 05/19/2016] [Indexed: 02/07/2023]
Abstract
The structure-specific nuclease human flap endonuclease-1 (hFEN1) plays a key role in DNA replication and repair and may be of interest as an oncology target. We present the crystal structure of inhibitor-bound hFEN1, which shows a cyclic N-hydroxyurea bound in the active site coordinated to two magnesium ions. Three such compounds had similar IC50 values but differed subtly in mode of action. One had comparable affinity for protein and protein-substrate complex and prevented reaction by binding to active site catalytic metal ions, blocking the necessary unpairing of substrate DNA. Other compounds were more competitive with substrate. Cellular thermal shift data showed that both inhibitor types engaged with hFEN1 in cells, and activation of the DNA damage response was evident upon treatment with inhibitors. However, cellular EC50 values were significantly higher than in vitro inhibition constants, and the implications of this for exploitation of hFEN1 as a drug target are discussed.
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Affiliation(s)
- Jack C Exell
- Centre for Chemical Biology, Department of Chemistry, Krebs Institute, University of Sheffield, Sheffield, UK
| | - Mark J Thompson
- Centre for Chemical Biology, Department of Chemistry, Krebs Institute, University of Sheffield, Sheffield, UK
| | - L David Finger
- Centre for Chemical Biology, Department of Chemistry, Krebs Institute, University of Sheffield, Sheffield, UK
| | - Steven J Shaw
- Centre for Chemical Biology, Department of Chemistry, Krebs Institute, University of Sheffield, Sheffield, UK
| | - Judit Debreczeni
- Discovery Sciences, Innovative Medicines and Early Development Biotech Unit, AstraZeneca, Cambridge, UK
| | - Thomas A Ward
- Bioscience, Oncology Innovative Medicines and Early Development Biotech Unit, AstraZeneca, Alderley Park, Cheshire, UK
| | - Claire McWhirter
- Discovery Sciences, Innovative Medicines and Early Development Biotech Unit, AstraZeneca, Cambridge, UK
| | | | | | - W Mark Abbott
- Discovery Sciences, Innovative Medicines and Early Development Biotech Unit, AstraZeneca, Cambridge, UK
| | - Clifford D Jones
- Chemistry, Oncology Innovative Medicines and Early Development Biotech Unit, AstraZeneca, Alderley Park, UK
| | - J Willem M Nissink
- Chemistry, Oncology Innovative Medicines and Early Development Biotech Unit, AstraZeneca, Cambridge, UK
| | - Stephen T Durant
- Bioscience, Oncology Innovative Medicines and Early Development Biotech Unit, Cambridge, UK
| | - Jane A Grasby
- Centre for Chemical Biology, Department of Chemistry, Krebs Institute, University of Sheffield, Sheffield, UK.,Bioscience, Oncology Innovative Medicines and Early Development Biotech Unit, Cambridge, UK
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14
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Woods RD, O'Shea VL, Chu A, Cao S, Richards JL, Horvath MP, David SS. Structure and stereochemistry of the base excision repair glycosylase MutY reveal a mechanism similar to retaining glycosidases. Nucleic Acids Res 2015; 44:801-10. [PMID: 26673696 PMCID: PMC4737165 DOI: 10.1093/nar/gkv1469] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 12/02/2015] [Indexed: 12/13/2022] Open
Abstract
MutY adenine glycosylases prevent DNA mutations by excising adenine from promutagenic 8-oxo-7,8-dihydroguanine (OG):A mismatches. Here, we describe structural features of the MutY active site bound to an azaribose transition state analog which indicate a catalytic role for Tyr126 and approach of the water nucleophile on the same side as the departing adenine base. The idea that Tyr126 participates in catalysis, recently predicted by modeling calculations, is strongly supported by mutagenesis and by seeing close contact between the hydroxyl group of this residue and the azaribose moiety of the transition state analog. NMR analysis of MutY methanolysis products corroborates a mechanism for adenine removal with retention of stereochemistry. Based on these results, we propose a revised mechanism for MutY that involves two nucleophilic displacement steps akin to the mechanisms accepted for 'retaining' O-glycosidases. This new-for-MutY yet familiar mechanism may also be operative in related base excision repair glycosylases and provides a critical framework for analysis of human MutY (MUTYH) variants associated with inherited colorectal cancer.
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Affiliation(s)
- Ryan D Woods
- Department of Chemistry, University of California, Davis, CA 95616, USA
| | - Valerie L O'Shea
- Department of Chemistry, University of California, Davis, CA 95616, USA Department of Chemistry, University of Utah, Salt Lake City, UT 84112, USA
| | - Aurea Chu
- Department of Chemistry, University of California, Davis, CA 95616, USA
| | - Sheng Cao
- Department of Chemistry, University of California, Davis, CA 95616, USA
| | - Jody L Richards
- Department of Chemistry, University of California, Davis, CA 95616, USA
| | - Martin P Horvath
- Department of Biology, University of Utah, Salt Lake City, UT 84112, USA
| | - Sheila S David
- Department of Chemistry, University of California, Davis, CA 95616, USA
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15
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Balliano AJ, Hayes JJ. Base excision repair in chromatin: Insights from reconstituted systems. DNA Repair (Amst) 2015; 36:77-85. [PMID: 26411876 DOI: 10.1016/j.dnarep.2015.09.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The process of base excision repair has been completely reconstituted in vitro and structural and biochemical properties of the component enzymes thoroughly studied on naked DNA templates. More recent work in this field aims to understand how BER operates on the natural substrate, chromatin [1,2]. Toward this end, a number of researchers, including the Smerdon group, have focused attention to understand how individual enzymes and reconstituted BER operate on nucleosome substrates. While nucleosomes were once thought to completely restrict access of DNA-dependent factors, the surprising finding from these studies suggests that at least some BER components can utilize target DNA bound within nucleosomes as substrates for their enzymatic processes. This data correlates well with both structural studies of these enzymes and our developing understanding of nucleosome conformation and dynamics. While more needs to be learned, these studies highlight the utility of reconstituted BER and chromatin systems to inform our understanding of in vivo biological processes.
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Affiliation(s)
- Angela J Balliano
- University of Rochester Medical Center, 601 Elmwood Ave., Box 712, Rochester, NY 14642, United States
| | - Jeffrey J Hayes
- University of Rochester Medical Center, 601 Elmwood Ave., Box 712, Rochester, NY 14642, United States.
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16
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Fuss JO, Tsai CL, Ishida JP, Tainer JA. Emerging critical roles of Fe-S clusters in DNA replication and repair. BIOCHIMICA ET BIOPHYSICA ACTA 2015; 1853:1253-71. [PMID: 25655665 PMCID: PMC4576882 DOI: 10.1016/j.bbamcr.2015.01.018] [Citation(s) in RCA: 130] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Revised: 01/13/2015] [Accepted: 01/26/2015] [Indexed: 10/24/2022]
Abstract
Fe-S clusters are partners in the origin of life that predate cells, acetyl-CoA metabolism, DNA, and the RNA world. The double helix solved the mystery of DNA replication by base pairing for accurate copying. Yet, for genome stability necessary to life, the double helix has equally important implications for damage repair. Here we examine striking advances that uncover Fe-S cluster roles both in copying the genetic sequence by DNA polymerases and in crucial repair processes for genome maintenance, as mutational defects cause cancer and degenerative disease. Moreover, we examine an exciting, controversial role for Fe-S clusters in a third element required for life - the long-range coordination and regulation of replication and repair events. By their ability to delocalize electrons over both Fe and S centers, Fe-S clusters have unbeatable features for protein conformational control and charge transfer via double-stranded DNA that may fundamentally transform our understanding of life, replication, and repair. This article is part of a Special Issue entitled: Fe/S proteins: Analysis, structure, function, biogenesis and diseases.
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Affiliation(s)
- Jill O Fuss
- Life Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA.
| | - Chi-Lin Tsai
- Life Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA
| | - Justin P Ishida
- Life Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA
| | - John A Tainer
- Life Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA; Department of Molecular and Cellular Oncology, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030, USA.
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17
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Beaver JM, Lai Y, Xu M, Casin AH, Laverde EE, Liu Y. AP endonuclease 1 prevents trinucleotide repeat expansion via a novel mechanism during base excision repair. Nucleic Acids Res 2015; 43:5948-60. [PMID: 25990721 PMCID: PMC4499148 DOI: 10.1093/nar/gkv530] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 05/10/2015] [Indexed: 01/28/2023] Open
Abstract
Base excision repair (BER) of an oxidized base within a trinucleotide repeat (TNR) tract can lead to TNR expansions that are associated with over 40 human neurodegenerative diseases. This occurs as a result of DNA secondary structures such as hairpins formed during repair. We have previously shown that BER in a TNR hairpin loop can lead to removal of the hairpin, attenuating or preventing TNR expansions. Here, we further provide the first evidence that AP endonuclease 1 (APE1) prevented TNR expansions via its 3′-5′ exonuclease activity and stimulatory effect on DNA ligation during BER in a hairpin loop. Coordinating with flap endonuclease 1, the APE1 3′-5′ exonuclease activity cleaves the annealed upstream 3′-flap of a double-flap intermediate resulting from 5′-incision of an abasic site in the hairpin loop. Furthermore, APE1 stimulated DNA ligase I to resolve a long double-flap intermediate, thereby promoting hairpin removal and preventing TNR expansions.
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Affiliation(s)
- Jill M Beaver
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA Biochemistry Ph.D. Program, Florida International University, Miami, FL 33199, USA
| | - Yanhao Lai
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA
| | - Meng Xu
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA
| | - Astrid H Casin
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA
| | - Eduardo E Laverde
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA
| | - Yuan Liu
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA Biochemistry Ph.D. Program, Florida International University, Miami, FL 33199, USA Biomolecular Sciences Institute, School of Integrated Sciences and Humanities, Florida International University, Miami, FL 33199, USA
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18
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Szulik M, Pallan PS, Nocek B, Voehler M, Banerjee S, Brooks S, Joachimiak A, Egli M, Eichman BF, Stone MP. Differential stabilities and sequence-dependent base pair opening dynamics of Watson-Crick base pairs with 5-hydroxymethylcytosine, 5-formylcytosine, or 5-carboxylcytosine. Biochemistry 2015; 54:1294-305. [PMID: 25632825 PMCID: PMC4325598 DOI: 10.1021/bi501534x] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
5-Hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC) form during active demethylation of 5-methylcytosine (5mC) and are implicated in epigenetic regulation of the genome. They are differentially processed by thymine DNA glycosylase (TDG), an enzyme involved in active demethylation of 5mC. Three modified Dickerson-Drew dodecamer (DDD) sequences, amenable to crystallographic and spectroscopic analyses and containing the 5'-CG-3' sequence associated with genomic cytosine methylation, containing 5hmC, 5fC, or 5caC placed site-specifically into the 5'-T(8)X(9)G(10)-3' sequence of the DDD, were compared. The presence of 5caC at the X(9) base increased the stability of the DDD, whereas 5hmC or 5fC did not. Both 5hmC and 5fC increased imino proton exchange rates and calculated rate constants for base pair opening at the neighboring base pair A(5):T(8), whereas 5caC did not. At the oxidized base pair G(4):X(9), 5fC exhibited an increase in the imino proton exchange rate and the calculated kop. In all cases, minimal effects to imino proton exchange rates occurred at the neighboring base pair C(3):G(10). No evidence was observed for imino tautomerization, accompanied by wobble base pairing, for 5hmC, 5fC, or 5caC when positioned at base pair G(4):X(9); each favored Watson-Crick base pairing. However, both 5fC and 5caC exhibited intranucleobase hydrogen bonding between their formyl or carboxyl oxygens, respectively, and the adjacent cytosine N(4) exocyclic amines. The lesion-specific differences observed in the DDD may be implicated in recognition of 5hmC, 5fC, or 5caC in DNA by TDG. However, they do not correlate with differential excision of 5hmC, 5fC, or 5caC by TDG, which may be mediated by differences in transition states of the enzyme-bound complexes.
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Affiliation(s)
- Marta
W. Szulik
- Department
of Chemistry, Vanderbilt Institute of Chemical Biology, Vanderbilt
Ingram Cancer Center, and Center for Structural Biology, Vanderbilt University, Nashville, Tennessee 37235, United States
| | - Pradeep S. Pallan
- Department
of Biochemistry, Vanderbilt Institute of Chemical Biology, Vanderbilt
Ingram Cancer Center, and Center for Structural Biology, School of
Medicine, Vanderbilt University, Nashville, Tennessee 37232, United States
| | - Boguslaw Nocek
- Bioscience
Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Markus Voehler
- Department
of Chemistry, Vanderbilt Institute of Chemical Biology, Vanderbilt
Ingram Cancer Center, and Center for Structural Biology, Vanderbilt University, Nashville, Tennessee 37235, United States
| | - Surajit Banerjee
- Northeastern
Collaborative Access Team and Department of Chemistry and Chemical
Biology, Cornell University, Argonne National
Laboratory, Argonne, Illinois 60439, United
States
| | - Sonja Brooks
- Department
of Biological Sciences, Vanderbilt Institute of Chemical Biology,
and Center for Structural Biology, Vanderbilt
University, Nashville, Tennessee 37235, United States
| | - Andrzej Joachimiak
- Bioscience
Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Martin Egli
- Department
of Biochemistry, Vanderbilt Institute of Chemical Biology, Vanderbilt
Ingram Cancer Center, and Center for Structural Biology, School of
Medicine, Vanderbilt University, Nashville, Tennessee 37232, United States
| | - Brandt F. Eichman
- Department
of Biological Sciences, Vanderbilt Institute of Chemical Biology,
and Center for Structural Biology, Vanderbilt
University, Nashville, Tennessee 37235, United States
| | - Michael P. Stone
- Department
of Chemistry, Vanderbilt Institute of Chemical Biology, Vanderbilt
Ingram Cancer Center, and Center for Structural Biology, Vanderbilt University, Nashville, Tennessee 37235, United States,(M.P.S.) Tel.: 615-322-2589; E-mail:
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19
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The cutting edges in DNA repair, licensing, and fidelity: DNA and RNA repair nucleases sculpt DNA to measure twice, cut once. DNA Repair (Amst) 2014; 19:95-107. [PMID: 24754999 DOI: 10.1016/j.dnarep.2014.03.022] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
To avoid genome instability, DNA repair nucleases must precisely target the correct damaged substrate before they are licensed to incise. Damage identification is a challenge for all DNA damage response proteins, but especially for nucleases that cut the DNA and necessarily create a cleaved DNA repair intermediate, likely more toxic than the initial damage. How do these enzymes achieve exquisite specificity without specific sequence recognition or, in some cases, without a non-canonical DNA nucleotide? Combined structural, biochemical, and biological analyses of repair nucleases are revealing their molecular tools for damage verification and safeguarding against inadvertent incision. Surprisingly, these enzymes also often act on RNA, which deserves more attention. Here, we review protein-DNA structures for nucleases involved in replication, base excision repair, mismatch repair, double strand break repair (DSBR), and telomere maintenance: apurinic/apyrimidinic endonuclease 1 (APE1), Endonuclease IV (Nfo), tyrosyl DNA phosphodiesterase (TDP2), UV Damage endonuclease (UVDE), very short patch repair endonuclease (Vsr), Endonuclease V (Nfi), Flap endonuclease 1 (FEN1), exonuclease 1 (Exo1), RNase T and Meiotic recombination 11 (Mre11). DNA and RNA structure-sensing nucleases are essential to life with roles in DNA replication, repair, and transcription. Increasingly these enzymes are employed as advanced tools for synthetic biology and as targets for cancer prognosis and interventions. Currently their structural biology is most fully illuminated for DNA repair, which is also essential to life. How DNA repair enzymes maintain genome fidelity is one of the DNA double helix secrets missed by James Watson and Francis Crick, that is only now being illuminated though structural biology and mutational analyses. Structures reveal motifs for repair nucleases and mechanisms whereby these enzymes follow the old carpenter adage: measure twice, cut once. Furthermore, to measure twice these nucleases act as molecular level transformers that typically reshape the DNA and sometimes themselves to achieve extraordinary specificity and efficiency.
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20
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Wyatt MD. Advances in understanding the coupling of DNA base modifying enzymes to processes involving base excision repair. Adv Cancer Res 2014; 119:63-106. [PMID: 23870509 DOI: 10.1016/b978-0-12-407190-2.00002-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
This chapter describes some of the recent, exciting developments that have characterized and connected processes that modify DNA bases with DNA repair pathways. It begins with AID/APOBEC or TET family members that covalently modify bases within DNA. The modified bases, such as uracil or 5-formylcytosine, are then excised by DNA glycosylases including UNG or TDG to initiate base excision repair (BER). BER is known to preserve genome integrity by removing damaged bases. The newer studies underscore the necessity of BER following enzymes that deliberately damage DNA. This includes the role of BER in antibody diversification and more recently, its requirement for demethylation of 5-methylcytosine in mammalian cells. The recent advances have shed light on mechanisms of DNA demethylation, and have raised many more questions. The potential hazards of these processes have also been revealed. Dysregulation of the activity of base modifying enzymes, and resolution by unfaithful or corrupt means can be a driver of genome instability and tumorigenesis. The understanding of both DNA and histone methylation and demethylation is now revealing the true extent to which epigenetics influence normal development and cancer, an abnormal development.
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Affiliation(s)
- Michael D Wyatt
- Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, South Carolina, USA.
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21
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Craggs TD, Hutton RD, Brenlla A, White MF, Penedo JC. Single-molecule characterization of Fen1 and Fen1/PCNA complexes acting on flap substrates. Nucleic Acids Res 2014; 42:1857-72. [PMID: 24234453 PMCID: PMC3919604 DOI: 10.1093/nar/gkt1116] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2013] [Revised: 10/21/2013] [Accepted: 10/22/2013] [Indexed: 11/21/2022] Open
Abstract
Flap endonuclease 1 (Fen1) is a highly conserved structure-specific nuclease that catalyses a specific incision to remove 5' flaps in double-stranded DNA substrates. Fen1 plays an essential role in key cellular processes, such as DNA replication and repair, and mutations that compromise Fen1 expression levels or activity have severe health implications in humans. The nuclease activity of Fen1 and other FEN family members can be stimulated by processivity clamps such as proliferating cell nuclear antigen (PCNA); however, the exact mechanism of PCNA activation is currently unknown. Here, we have used a combination of ensemble and single-molecule Förster resonance energy transfer together with protein-induced fluorescence enhancement to uncouple and investigate the substrate recognition and catalytic steps of Fen1 and Fen1/PCNA complexes. We propose a model in which upon Fen1 binding, a highly dynamic substrate is bent and locked into an open flap conformation where specific Fen1/DNA interactions can be established. PCNA enhances Fen1 recognition of the DNA substrate by further promoting the open flap conformation in a step that may involve facilitated threading of the 5' ssDNA flap. Merging our data with existing crystallographic and molecular dynamics simulations we provide a solution-based model for the Fen1/PCNA/DNA ternary complex.
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Affiliation(s)
- Timothy D. Craggs
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife, KY16 9SS, UK and Biomedical Sciences Research Complex, University of St Andrews, St Andrews, Fife KY16 9SS, UK
| | - Richard D. Hutton
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife, KY16 9SS, UK and Biomedical Sciences Research Complex, University of St Andrews, St Andrews, Fife KY16 9SS, UK
| | - Alfonso Brenlla
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife, KY16 9SS, UK and Biomedical Sciences Research Complex, University of St Andrews, St Andrews, Fife KY16 9SS, UK
| | - Malcolm F. White
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife, KY16 9SS, UK and Biomedical Sciences Research Complex, University of St Andrews, St Andrews, Fife KY16 9SS, UK
| | - J. Carlos Penedo
- SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, Fife, KY16 9SS, UK and Biomedical Sciences Research Complex, University of St Andrews, St Andrews, Fife KY16 9SS, UK
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22
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Prindle MJ, Loeb LA. DNA polymerase delta in DNA replication and genome maintenance. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2012; 53:666-82. [PMID: 23065663 PMCID: PMC3694620 DOI: 10.1002/em.21745] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2012] [Revised: 09/09/2012] [Accepted: 09/12/2012] [Indexed: 05/12/2023]
Abstract
The eukaryotic genome is in a constant state of modification and repair. Faithful transmission of the genomic information from parent to daughter cells depends upon an extensive system of surveillance, signaling, and DNA repair, as well as accurate synthesis of DNA during replication. Often, replicative synthesis occurs over regions of DNA that have not yet been repaired, presenting further challenges to genomic stability. DNA polymerase δ (pol δ) occupies a central role in all of these processes: catalyzing the accurate replication of a majority of the genome, participating in several DNA repair synthetic pathways, and contributing structurally to the accurate bypass of problematic lesions during translesion synthesis. The concerted actions of pol δ on the lagging strand, pol ϵ on the leading strand, associated replicative factors, and the mismatch repair (MMR) proteins results in a mutation rate of less than one misincorporation per genome per replication cycle. This low mutation rate provides a high level of protection against genetic defects during development and may prevent the initiation of malignancies in somatic cells. This review explores the role of pol δ in replication fidelity and genome maintenance.
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Affiliation(s)
- Marc J Prindle
- Department of Pathology, The Joseph Gottstien Memorial Cancer Research Laboratory, University of Washington, Seattle, WA 98195-7705, USA
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23
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Kleppa L, Mari PO, Larsen E, Lien GF, Godon C, Theil AF, Nesse GJ, Wiksen H, Vermeulen W, Giglia-Mari G, Klungland A. Kinetics of endogenous mouse FEN1 in base excision repair. Nucleic Acids Res 2012; 40:9044-59. [PMID: 22810208 PMCID: PMC3467068 DOI: 10.1093/nar/gks673] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The structure specific flap endonuclease 1 (FEN1) plays an essential role in long-patch base excision repair (BER) and in DNA replication. We have generated a fluorescently tagged FEN1 expressing mouse which allows monitoring the localization and kinetics of FEN1 in response to DNA damage in living cells and tissues. The expression of FEN1, which is tagged at its C-terminal end with enhanced yellow fluorescent protein (FEN1-YFP), is under control of the endogenous Fen1 transcriptional regulatory elements. In line with its role in processing of Okazaki fragments during DNA replication, we found that FEN1-YFP expression is mainly observed in highly proliferating tissue. Moreover, the FEN1-YFP fusion protein allowed us to investigate repair kinetics in cells challenged with local and global DNA damage. In vivo multi-photon fluorescence microscopy demonstrates rapid localization of FEN1 to local laser-induced DNA damage sites in nuclei, providing evidence of a highly mobile protein that accumulates fast at DNA lesion sites with high turnover rate. Inhibition of poly (ADP-ribose) polymerase 1 (PARP1) disrupts FEN1 accumulation at sites of DNA damage, indicating that PARP1 is required for FEN1 recruitment to DNA repair intermediates in BER.
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Affiliation(s)
- Liv Kleppa
- Centre for Molecular Biology and Neuroscience and Institute of Clinical Medicine, Oslo University Hospital, Rikshospitalet, Norway
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24
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Miller AS, Balakrishnan L, Buncher NA, Opresko PL, Bambara RA. Telomere proteins POT1, TRF1 and TRF2 augment long-patch base excision repair in vitro. Cell Cycle 2012; 11:998-1007. [PMID: 22336916 PMCID: PMC3323798 DOI: 10.4161/cc.11.5.19483] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Revised: 01/24/2012] [Accepted: 01/25/2012] [Indexed: 12/13/2022] Open
Abstract
Human telomeres consist of multiple tandem hexameric repeats, each containing a guanine triplet. Guanosine-rich clusters are highly susceptible to oxidative base damage, necessitating base excision repair (BER). Previous demonstration of enhanced strand displacement synthesis by the BER component DNA polymerase β in the presence of telomere protein TRF2 suggests that telomeres employ long-patch (LP) BER. Earlier analyses in vitro showed that efficiency of BER reactions is reduced in the DNA-histone environment of chromatin. Evidence presented here indicates that BER is promoted at telomeres. We found that the three proteins that contact telomere DNA, POT1, TRF1 and TRF2, enhance the rate of individual steps of LP-BER and stimulate the complete reconstituted LP-BER pathway. Thought to protect telomere DNA from degradation, these proteins still apparently evolved to allow selective access of repair proteins.
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Affiliation(s)
- Adam S Miller
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
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25
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Tsutakawa SE, Tainer JA. Double strand binding-single strand incision mechanism for human flap endonuclease: implications for the superfamily. Mech Ageing Dev 2012; 133:195-202. [PMID: 22244820 DOI: 10.1016/j.mad.2011.11.009] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Revised: 10/31/2011] [Accepted: 11/29/2011] [Indexed: 11/17/2022]
Abstract
Detailed structural, mutational, and biochemical analyses of human FEN1/DNA complexes have revealed the mechanism for recognition of 5' flaps formed during lagging strand replication and DNA repair. FEN1 processes 5' flaps through a previously unknown, but structurally elegant double-stranded (ds) recognition/single stranded (ss) incision mechanism that both selects for 5' flaps and selects against ss DNA or RNA, intact dsDNA, and 3' flaps. Two major DNA binding interfaces, including a K(+) bridge between the DNA and the H2TH motif, are spaced one helical turn apart and together select for substrates with dsDNA. A conserved helical gateway and a helical cap protects the two-metal active site and selects for ss flaps with free termini. Structures of substrate and product reveal an unusual step between binding substrate and incision that involves a double base unpairing with incision occurring in the resulting unpaired DNA or RNA. Ordering of the active site requires a disorder-to-order transition induced by binding of an unpaired 3' flap, which ensures that the product is ligatable. Comparison with FEN superfamily members, including XPG, EXO1, and GEN1, identifies superfamily motifs such as the helical gateway that select for ss-dsDNA junctions and provides key biological insights into nuclease specificity and regulation.
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Affiliation(s)
- Susan E Tsutakawa
- Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
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26
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Finger LD, Atack JM, Tsutakawa S, Classen S, Tainer J, Grasby J, Shen B. The wonders of flap endonucleases: structure, function, mechanism and regulation. Subcell Biochem 2012; 62:301-26. [PMID: 22918592 PMCID: PMC3728657 DOI: 10.1007/978-94-007-4572-8_16] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Processing of Okazaki fragments to complete lagging strand DNA synthesis requires coordination among several proteins. RNA primers and DNA synthesised by DNA polymerase α are displaced by DNA polymerase δ to create bifurcated nucleic acid structures known as 5'-flaps. These 5'-flaps are removed by Flap Endonuclease 1 (FEN), a structure-specific nuclease whose divalent metal ion-dependent phosphodiesterase activity cleaves 5'-flaps with exquisite specificity. FENs are paradigms for the 5' nuclease superfamily, whose members perform a wide variety of roles in nucleic acid metabolism using a similar nuclease core domain that displays common biochemical properties and structural features. A detailed review of FEN structure is undertaken to show how DNA substrate recognition occurs and how FEN achieves cleavage at a single phosphate diester. A proposed double nucleotide unpairing trap (DoNUT) is discussed with regards to FEN and has relevance to the wider 5' nuclease superfamily. The homotrimeric proliferating cell nuclear antigen protein (PCNA) coordinates the actions of DNA polymerase, FEN and DNA ligase by facilitating the hand-off intermediates between each protein during Okazaki fragment maturation to maximise through-put and minimise consequences of intermediates being released into the wider cellular environment. FEN has numerous partner proteins that modulate and control its action during DNA replication and is also controlled by several post-translational modification events, all acting in concert to maintain precise and appropriate cleavage of Okazaki fragment intermediates during DNA replication.
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Affiliation(s)
- L. David Finger
- Department of Chemistry, Centre for Chemical Biology, Krebs Institute, University of Sheffield, Sheffield S3 7HF, UK
| | - John M. Atack
- Department of Chemistry, Centre for Chemical Biology, Krebs Institute, University of Sheffield, Sheffield S3 7HF, UK
| | - Susan Tsutakawa
- Life Sciences Division, Lawrence Berkeley National, Laboratory, Berkeley, CA 94720, USA
| | - Scott Classen
- Physical Biosciences Division, The Scripps Research, Institute, La Jolla, CA 92037, USA
| | - John Tainer
- Life Sciences Division, Lawrence Berkeley, National Laboratory, Berkeley, CA 94720, USA, Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037, USA, Skaggs Institute for Chemical Biology, La Jolla, CA 92037, USA
| | - Jane Grasby
- Department of Chemistry, Centre for Chemical Biology, Krebs Institute, University of Sheffield, Sheffield S3 7HF, UK
| | - Binghui Shen
- Division of Radiation Biology, City of Hope National Medical Center and Beckman Research Institute, Duarte, CA 91010, USA, College of Life Sciences, Zhejiang University, Hangzhou 310058, China
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27
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Silhan J, Nagorska K, Zhao Q, Jensen K, Freemont PS, Tang CM, Baldwin GS. Specialization of an Exonuclease III family enzyme in the repair of 3' DNA lesions during base excision repair in the human pathogen Neisseria meningitidis. Nucleic Acids Res 2011; 40:2065-75. [PMID: 22067446 PMCID: PMC3300015 DOI: 10.1093/nar/gkr905] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
We have previously demonstrated that the two Exonuclease III (Xth) family members present within the obligate human pathogen Neisseria meningitidis, NApe and NExo, are important for survival under conditions of oxidative stress. Of these, only NApe possesses AP endonuclease activity, while the primary function of NExo remained unclear. We now reveal further functional specialization at the level of 3′-PO4 processing for NExo. We demonstrate that the bi-functional meningococcal glycosylases Nth and MutM can perform strand incisions at abasic sites in addition to NApe. However, no such functional redundancy exists for the 3′-phosphatase activity of NExo, and the cytotoxicity of 3′-blocking lesions is reflected in the marked sensitivity of a mutant lacking NExo to oxidative stress, compared to strains deficient in other base excision repair enzymes. A histidine residue within NExo that is responsible for its lack of AP endonuclease activity is also important for its 3′-phosphatase activity, demonstrating an evolutionary trade off in enzyme function at the single amino acid level. This specialization of two Xth enzymes for the 3′-end processing and strand-incision reactions has not previously been observed and provides a new paradigm within the prokaryotic world for separation of these critical functions during base excision repair.
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Affiliation(s)
- Jan Silhan
- Division of Molecular Biosciences, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK
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28
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DNA glycosylases: in DNA repair and beyond. Chromosoma 2011; 121:1-20. [PMID: 22048164 PMCID: PMC3260424 DOI: 10.1007/s00412-011-0347-4] [Citation(s) in RCA: 251] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2011] [Revised: 10/10/2011] [Accepted: 10/11/2011] [Indexed: 12/20/2022]
Abstract
The base excision repair machinery protects DNA in cells from the damaging effects of oxidation, alkylation, and deamination; it is specialized to fix single-base damage in the form of small chemical modifications. Base modifications can be mutagenic and/or cytotoxic, depending on how they interfere with the template function of the DNA during replication and transcription. DNA glycosylases play a key role in the elimination of such DNA lesions; they recognize and excise damaged bases, thereby initiating a repair process that restores the regular DNA structure with high accuracy. All glycosylases share a common mode of action for damage recognition; they flip bases out of the DNA helix into a selective active site pocket, the architecture of which permits a sensitive detection of even minor base irregularities. Within the past few years, it has become clear that nature has exploited this ability to read the chemical structure of DNA bases for purposes other than canonical DNA repair. DNA glycosylases have been brought into context with molecular processes relating to innate and adaptive immunity as well as to the control of DNA methylation and epigenetic stability. Here, we summarize the key structural and mechanistic features of DNA glycosylases with a special focus on the mammalian enzymes, and then review the evidence for the newly emerging biological functions beyond the protection of genome integrity.
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29
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Nucleosome disruption by DNA ligase III-XRCC1 promotes efficient base excision repair. Mol Cell Biol 2011; 31:4623-32. [PMID: 21930793 DOI: 10.1128/mcb.05715-11] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Each day, approximately 20,000 oxidative lesions form in the DNA of every nucleated human cell. The base excision repair (BER) enzymes that repair these lesions must function in a chromatin milieu. We have determined that the DNA glycosylase hNTH1, apurinic endonuclease (APE), and DNA polymerase β (Pol β), which catalyze the first three steps in BER, are able to process their substrates in both 601- and 5S ribosomal DNA (rDNA)-based nucleosomes. hNTH1 formed a discrete ternary complex that was displaced by the addition of APE, suggesting an orderly handoff of substrates from one enzyme to the next. In contrast, DNA ligase IIIα-XRCC1, which completes BER, was appreciably active only at concentrations that led to nucleosome disruption. Ligase IIIα-XRCC1 was also able to bind and disrupt nucleosomes containing a single base gap and, because of this property, enhanced both its own activity and that of Pol β on nucleosome substrates. Collectively, these findings provide insights into rate-limiting steps that govern BER in chromatin and reveal a unique role for ligase IIIα-XRCC1 in enhancing the efficiency of the final two steps in the BER of lesions in nucleosomes.
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30
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Prasad R, Beard WA, Batra VK, Liu Y, Shock DD, Wilson SH. A review of recent experiments on step-to-step “hand-off” of the DNA intermediates in mammalian base excision repair pathways. Mol Biol 2011. [DOI: 10.1134/s0026893311040091] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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31
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Tubbs JL, Tainer JA. P53 conformational switching for selectivity may reveal a general solution for specific DNA binding. EMBO J 2011; 30:2099-100. [PMID: 21629273 DOI: 10.1038/emboj.2011.133] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Affiliation(s)
- Julie L Tubbs
- Department of Molecular Biology, Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA, USA
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32
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Abstract
In this issue, Orans et al. (2011) and Tsutakawa et al. (2011) report exciting insights into the molecular principles governing diverse endo- and exonucleolytic cleavage specificities of members of the RAD2/FEN superfamily of nucleases, which have critical roles in DNA replication and maintenance.
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Affiliation(s)
- R Scott Williams
- Laboratory of Structural Biology, National Institute of Environmental Health Sciences, National Institutes of Health, DHHS, Research Triangle Park, NC 27709, USA.
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33
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Prasad R, Shock DD, Beard WA, Wilson SH. Substrate channeling in mammalian base excision repair pathways: passing the baton. J Biol Chem 2010; 285:40479-88. [PMID: 20952393 DOI: 10.1074/jbc.m110.155267] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The current model for base excision repair (BER) involves two general sub-pathways termed single-nucleotide BER and long patch BER that are distinguished by their repair patch sizes and the enzymes/co-factors involved. Both sub-pathways involve a series of sequential steps from initiation to completion of repair. The BER sub-pathways are designed to sequester the various intermediates, passing them along from one step to the next without allowing these toxic molecules to trigger cell cycle arrest, necrotic cell death, or apoptosis. Although a variety of DNA-protein and protein-protein interactions are known for the BER intermediates and enzymes/co-factors, the molecular mechanisms accounting for step-to-step coordination are not well understood. In the present study we designed an in vitro assay to explore the question of whether there is a channeling or "hand-off" of the repair intermediates during BER in vitro. The results show that when BER enzymes are pre-bound to the initial single-nucleotide BER intermediate, the DNA is channeled from apurinic/apyrimidinic endonuclease 1 to DNA polymerase β and then to DNA ligase. In the long patch BER subpathway, where the 5'-end of the incised strand is blocked, the intermediate after DNA polymerase β gap filling is not channeled to the subsequent enzyme, flap endonuclease 1. Instead, flap endonuclease 1 must recognize and bind to the intermediate in competition with other molecules.
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Affiliation(s)
- Rajendra Prasad
- Laboratory of Structural Biology, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA
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34
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Hegde ML, Hazra TK, Mitra S. Functions of disordered regions in mammalian early base excision repair proteins. Cell Mol Life Sci 2010; 67:3573-87. [PMID: 20714778 DOI: 10.1007/s00018-010-0485-5] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Accepted: 07/28/2010] [Indexed: 11/30/2022]
Abstract
Reactive oxygen species, generated endogenously and induced as a toxic response, produce several dozen oxidized or modified bases and/or single-strand breaks in mammalian and other genomes. These lesions are predominantly repaired via the conserved base excision repair (BER) pathway. BER is initiated with excision of oxidized or modified bases by DNA glycosylases leading to formation of abasic (AP) site or strand break at the lesion site. Structural analysis by experimental and modeling approaches shows the presence of a disordered segment commonly localized at the N- or C-terminus as a characteristic signature of mammalian DNA glycosylases which is absent in their bacterial prototypes. Recent studies on unstructured regions in DNA metabolizing proteins have indicated their essential role in interaction with other proteins and target DNA recognition. In this review, we have discussed the unique presence of disordered segments in human DNA glycosylases, and AP endonuclease involved in the processing of glycosylase products, and their critical role in regulating repair functions. These disordered segments also include sites for posttranslational modifications and nuclear localization signal. The teleological basis for their structural flexibility is discussed.
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Affiliation(s)
- Muralidhar L Hegde
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, 301 University Blvd, Galveston, TX 77555-1079, USA
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35
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Raeder ILU, Moe E, Willassen NP, Smalås AO, Leiros I. Structure of uracil-DNA N-glycosylase (UNG) from Vibrio cholerae: mapping temperature adaptation through structural and mutational analysis. Acta Crystallogr Sect F Struct Biol Cryst Commun 2010; 66:130-6. [PMID: 20124707 PMCID: PMC2815677 DOI: 10.1107/s1744309109052063] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2009] [Accepted: 12/03/2009] [Indexed: 11/10/2022]
Abstract
The crystal structure of Vibrio cholerae uracil-DNA N-glycosylase (vcUNG) has been determined to 1.5 A resolution. Based on this structure, a homology model of Aliivibrio salmonicida uracil-DNA N-glycosylase (asUNG) was built. A previous study demonstrated that asUNG possesses typical cold-adapted features compared with vcUNG, such as a higher catalytic efficiency owing to increased substrate affinity. Specific amino-acid substitutions in asUNG were suggested to be responsible for the increased substrate affinity and the elevated catalytic efficiency by increasing the positive surface charge in the DNA-binding region. The temperature adaptation of these enzymes has been investigated using structural and mutational analyses, in which mutations of vcUNG demonstrated an increased substrate affinity that more resembled that of asUNG. Visualization of surface potentials revealed a more positive potential for asUNG compared with vcUNG; a modelled double mutant of vcUNG had a potential around the substrate-binding region that was more like that of asUNG, thus rationalizing the results obtained from the kinetic studies.
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Affiliation(s)
- Inger Lin Uttakleiv Raeder
- Department of Chemistry, Faculty of Science, University of Tromsø, N-9037 Tromsø, Norway
- The Norwegian Structural Biology Centre, University of Tromsø, N-9037 Tromsø, Norway
| | - Elin Moe
- Department of Chemistry, Faculty of Science, University of Tromsø, N-9037 Tromsø, Norway
- The Norwegian Structural Biology Centre, University of Tromsø, N-9037 Tromsø, Norway
| | - Nils Peder Willassen
- The Norwegian Structural Biology Centre, University of Tromsø, N-9037 Tromsø, Norway
- Department of Molecular Biotechnology, Institute of Medical Biology, University of Tromsø, N-9037 Tromsø, Norway
| | - Arne O. Smalås
- Department of Chemistry, Faculty of Science, University of Tromsø, N-9037 Tromsø, Norway
- The Norwegian Structural Biology Centre, University of Tromsø, N-9037 Tromsø, Norway
| | - Ingar Leiros
- Department of Chemistry, Faculty of Science, University of Tromsø, N-9037 Tromsø, Norway
- The Norwegian Structural Biology Centre, University of Tromsø, N-9037 Tromsø, Norway
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36
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Khairnar NP, Misra HS. DNA polymerase X from Deinococcus radiodurans implicated in bacterial tolerance to DNA damage is characterized as a short patch base excision repair polymerase. Microbiology (Reading) 2009; 155:3005-3014. [DOI: 10.1099/mic.0.029223-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Deinococcus radiodurans R1 genome encodes an X-family DNA repair polymerase homologous to eukaryotic DNA polymerase β. The recombinant deinococcal polymerase X (PolX) purified from transgenic Escherichia coli showed deoxynucleotidyltransferase activity. Unlike the Klenow fragment of E. coli, this enzyme showed short patch DNA synthesis activity on heteropolymeric DNA substrate. The recombinant enzyme showed 5′-deoxyribose phosphate (5′-dRP) lyase activity and base excision repair function in vitro, with the help of externally supplied glycosylase and AP endonuclease functions. A polX disruption mutant of D. radiodurans expressing 5′-dRP lyase and a truncated polymerase domain was comparatively less sensitive to γ-radiation than a polX deletion mutant. Both mutants showed higher sensitivity to hydrogen peroxide. Excision repair mutants of E. coli expressing this polymerase showed functional complementation of UV sensitivity. These results suggest the involvement of deinococcal polymerase X in DNA-damage tolerance of D. radiodurans, possibly by contributing to DNA double-strand break repair and base excision repair.
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Affiliation(s)
- Nivedita P. Khairnar
- Molecular Biology Division, Bhabha Atomic Research Centre, Mumbai-400 085, India
| | - Hari S. Misra
- Molecular Biology Division, Bhabha Atomic Research Centre, Mumbai-400 085, India
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37
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Bischerour J, Chalmers R. Base flipping in tn10 transposition: an active flip and capture mechanism. PLoS One 2009; 4:e6201. [PMID: 19593448 PMCID: PMC2705183 DOI: 10.1371/journal.pone.0006201] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2009] [Accepted: 05/25/2009] [Indexed: 11/19/2022] Open
Abstract
The bacterial Tn5 and Tn10 transposases have a single active site that cuts both strands of DNA at their respective transposon ends. This is achieved using a hairpin intermediate that requires the DNA to change conformation during the reaction. In Tn5 these changes are controlled in part by a flipped nucleoside that is stacked on a tryptophan residue in a hydrophobic pocket of the transposase. Here we have investigated the base flipping mechanism in Tn10 transposition. As in Tn5 transposition, we find that base flipping takes place after the first nick and is required for efficient hairpin formation and resolution. Experiments with an abasic substrate show that the role of base flipping in hairpin formation is to remove the base from the DNA helix. Specific interactions between the flipped base and the stacking tryptophan residue are required for hairpin resolution later in the reaction. We show that base flipping in Tn10 transposition is not a passive reaction in which a spontaneously flipped base is captured and retained by the protein. Rather, it is driven in part by a methionine probe residue that helps to force the flipped base from the base stack. Overall, it appears that base flipping in Tn10 transposition is similar to that in Tn5 transposition.
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Affiliation(s)
- Julien Bischerour
- University of Nottingham, School of Biomedical Sciences, The Medical School, Queens Medical Centre (QMC), Nottingham, United Kingdom
| | - Ronald Chalmers
- University of Nottingham, School of Biomedical Sciences, The Medical School, Queens Medical Centre (QMC), Nottingham, United Kingdom
- * E-mail:
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38
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Dalhus B, Laerdahl JK, Backe PH, Bjørås M. DNA base repair--recognition and initiation of catalysis. FEMS Microbiol Rev 2009; 33:1044-78. [PMID: 19659577 DOI: 10.1111/j.1574-6976.2009.00188.x] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Endogenous DNA damage induced by hydrolysis, reactive oxygen species and alkylation modifies DNA bases and the structure of the DNA duplex. Numerous mechanisms have evolved to protect cells from these deleterious effects. Base excision repair is the major pathway for removing base lesions. However, several mechanisms of direct base damage reversal, involving enzymes such as transferases, photolyases and oxidative demethylases, are specialized to remove certain types of photoproducts and alkylated bases. Mismatch excision repair corrects for misincorporation of bases by replicative DNA polymerases. The determination of the 3D structure and visualization of DNA repair proteins and their interactions with damaged DNA have considerably aided our understanding of the molecular basis for DNA base lesion repair and genome stability. Here, we review the structural biochemistry of base lesion recognition and initiation of one-step direct reversal (DR) of damage as well as the multistep pathways of base excision repair (BER), nucleotide incision repair (NIR) and mismatch repair (MMR).
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Affiliation(s)
- Bjørn Dalhus
- Centre for Molecular Biology and Neuroscience (CMBN), Rikshospitalet University Hospital, Oslo, Norway
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39
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Unnikrishnan A, Raffoul JJ, Patel HV, Prychitko TM, Anyangwe N, Meira LB, Friedberg EC, Cabelof DC, Heydari AR. Oxidative stress alters base excision repair pathway and increases apoptotic response in apurinic/apyrimidinic endonuclease 1/redox factor-1 haploinsufficient mice. Free Radic Biol Med 2009; 46:1488-99. [PMID: 19268524 PMCID: PMC2677124 DOI: 10.1016/j.freeradbiomed.2009.02.021] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2008] [Revised: 02/04/2009] [Accepted: 02/23/2009] [Indexed: 12/21/2022]
Abstract
Apurinic/apyrimidinic endonuclease 1/redox factor-1 (APE1/Ref-1) is the redox regulator of multiple stress-inducible transcription factors, such as NF-kappaB, and the major 5'-endonuclease in base excision repair (BER). We utilized mice containing a heterozygous gene-targeted deletion of APE1/Ref-1 (Apex(+/-)) to determine the impact of APE1/Ref-1 haploinsufficiency on the processing of oxidative DNA damage induced by 2-nitropropane (2-NP) in the liver tissue of mice. APE1/Ref-1 haploinsufficiency results in a significant decline in NF-kappaB DNA-binding activity in response to oxidative stress in liver. In addition, loss of APE1/Ref-1 increases the apoptotic response to oxidative stress, in which significant increases in GADD45g expression, p53 protein stability, and caspase activity are observed. Oxidative stress displays a differential impact on monofunctional (UNG) and bifunctional (OGG1) DNA glycosylase-initiated BER in the liver of Apex(+/-) mice. APE1/Ref-1 haploinsufficiency results in a significant decline in the repair of oxidized bases (e.g., 8-OHdG), whereas removal of uracil is increased in liver nuclear extracts of mice using an in vitro BER assay. Apex(+/-) mice exposed to 2-NP displayed a significant decline in 3'-OH-containing single-strand breaks and an increase in aldehydic lesions in their liver DNA, suggesting an accumulation of repair intermediates of failed bifunctional DNA glycosylase-initiated BER.
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Affiliation(s)
- Archana Unnikrishnan
- Department of Nutrition & Food Science, Wayne State University, Detroit, MI, 48202, USA
| | - Julian J. Raffoul
- Department of Nutrition & Food Science, Wayne State University, Detroit, MI, 48202, USA
| | - Hiral V. Patel
- Department of Nutrition & Food Science, Wayne State University, Detroit, MI, 48202, USA
| | - Thomas M. Prychitko
- Department of Nutrition & Food Science, Wayne State University, Detroit, MI, 48202, USA
| | - Njwen Anyangwe
- Department of Nutrition & Food Science, Wayne State University, Detroit, MI, 48202, USA
| | - Lisiane B. Meira
- Biological Engineering Division, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Errol C. Friedberg
- Laboratory of Molecular Pathology, Department of Pathology, The University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Diane C. Cabelof
- Department of Nutrition & Food Science, Wayne State University, Detroit, MI, 48202, USA
- Barbara Ann Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, MI, 48201, USA
| | - Ahmad R. Heydari
- Department of Nutrition & Food Science, Wayne State University, Detroit, MI, 48202, USA
- Barbara Ann Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, MI, 48201, USA
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40
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Baños B, Lázaro JM, Villar L, Salas M, de Vega M. Editing of misaligned 3'-termini by an intrinsic 3'-5' exonuclease activity residing in the PHP domain of a family X DNA polymerase. Nucleic Acids Res 2008; 36:5736-49. [PMID: 18776221 PMCID: PMC2566882 DOI: 10.1093/nar/gkn526] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Bacillus subtilis gene yshC encodes a family X DNA polymerase (PolXBs), whose biochemical features suggest that it plays a role during DNA repair processes. Here, we show that, in addition to the polymerization activity, PolXBs possesses an intrinsic 3′–5′ exonuclease activity specialized in resecting unannealed 3′-termini in a gapped DNA substrate. Biochemical analysis of a PolXBs deletion mutant lacking the C-terminal polymerase histidinol phosphatase (PHP) domain, present in most of the bacterial/archaeal PolXs, as well as of this separately expressed protein region, allow us to state that the 3′–5′ exonuclease activity of PolXBs resides in its PHP domain. Furthermore, site-directed mutagenesis of PolXBs His339 and His341 residues, evolutionary conserved in the PHP superfamily members, demonstrated that the predicted metal binding site is directly involved in catalysis of the exonucleolytic reaction. The implications of the unannealed 3′-termini resection by the 3′–5′ exonuclease activity of PolXBs in the DNA repair context are discussed.
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Affiliation(s)
- Benito Baños
- Instituto de Biología Molecular Eladio Viñuela (CSIC), Centro de Biología Molecular Severo Ochoa (CSIC-UAM), C/Nicolás Cabrera 1, Cantoblanco, 28049 Madrid, Spain
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41
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Xu G, Herzig M, Rotrekl V, Walter CA. Base excision repair, aging and health span. Mech Ageing Dev 2008; 129:366-82. [PMID: 18423806 PMCID: PMC2526234 DOI: 10.1016/j.mad.2008.03.001] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2007] [Revised: 02/28/2008] [Accepted: 03/05/2008] [Indexed: 12/18/2022]
Abstract
DNA damage and mutagenesis are suggested to contribute to aging through their ability to mediate cellular dysfunction. The base excision repair (BER) pathway ameliorates a large number of DNA lesions that arise spontaneously. Many of these lesions are reported to increase with age. Oxidized guanine, repaired largely via base excision repair, is particularly well studied and shown to increase with age. Spontaneous mutant frequencies also increase with age which suggests that mutagenesis may contribute to aging. It is widely accepted that genetic instability contributes to age-related occurrences of cancer and potentially other age-related pathologies. BER activity decreases with age in multiple tissues. The specific BER protein that appears to limit activity varies among tissues. DNA polymerase-beta is reduced in brain from aged mice and rats while AP endonuclease is reduced in spermatogenic cells obtained from old mice. The differences in proteins that appear to limit BER activity among tissues may represent true tissue-specific differences in activity or may be due to differences in techniques, environmental conditions or other unidentified differences among the experimental approaches. Much remains to be addressed concerning the potential role of BER in aging and age-related health span.
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Affiliation(s)
- Guogang Xu
- Department of Cellular & Structural Biology, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900
| | - Maryanne Herzig
- Department of Cellular & Structural Biology, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900
| | - Vladimir Rotrekl
- Institute of Experimental Medicine, Department of Molecular Embryology, Masaryk University, Faculty of Medicine, Department of Biology, Kamenice 5, Building A6, 62500 Brno, Czech Republic
| | - Christi A. Walter
- Department of Cellular & Structural Biology, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900
- South Texas Veteran’s Health Care System, 7400 Merton Minter Blvd, San Antonio, TX 78229
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42
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Rutledge LR, Campbell-Verduyn LS, Hunter KC, Wetmore SD. Characterization of nucleobase-amino acid stacking interactions utilized by a DNA repair enzyme. J Phys Chem B 2007; 110:19652-63. [PMID: 17004834 DOI: 10.1021/jp061939v] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The present work characterizes the gas-phase stacking interactions between four aromatic amino acid residues (histidine, phenylalanine, tyrosine, and tryptophan) and adenine or 3-methyladenine due to the proposed utilization of these interactions by enzymes that repair DNA alkylation damage. The MP2 potential energy surfaces of the stacked dimers are considered as a function of four variables (vertical displacement, angle of rotation, horizontal displacement, and tilt angle) using a variety of basis sets. It is found that the maximum stacking interaction energy decreases with the amino acid according to TRP > TYR approximately HIS > PHE for both nucleobases. However, the magnitude of the stacking interaction significantly increases upon alkylation (by 50-115%). Comparison of the stacking energies calculated using our surface scans to those estimated from experimental crystal structures indicates that the stacking interactions within the active site of 3-methyladenine DNA glycosylase can account for 65-75% of the maximum possible stacking interaction between the relevant molecules. The decrease in stacking in the crystal structure arises due to significant differences in the relative orientations of the nucleobase and amino acid. Nevertheless, alkylation is found to significantly increase the stacking energy when the crystal structure geometries are considered. Our calculations provide computational support for suggestions that alkylation enhances the stacking interactions within the active site of DNA repair enzymes, and they give a measure of the magnitude of this enhancement. Our results suggest that alkylation likely plays a more important role in substrate identification and removal than the nature of the aromatic amino acid that interacts with the substrate via stacking interactions.
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Affiliation(s)
- Lesley R Rutledge
- Department of Chemistry, Mount Allison University, 63C York Street, Sackville, New Brunswick, Canada E4L 1G8
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Gill S, O'Neill R, Lewis RJ, Connolly BA. Interaction of the family-B DNA polymerase from the archaeon Pyrococcus furiosus with deaminated bases. J Mol Biol 2007; 372:855-863. [PMID: 17692870 DOI: 10.1016/j.jmb.2007.07.015] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2007] [Revised: 06/29/2007] [Accepted: 07/09/2007] [Indexed: 11/20/2022]
Abstract
The interaction of archaeal family B DNA polymerases with deaminated bases has been examined. As determined previously by our group, the polymerase binds tightly to uracil (the deamination product of cytosine), in single-stranded DNA, and stalls replication on encountering this base. DNA polymerisation was also inhibited by the presence of hypoxanthine, the deamination product of adenine. Quantitative binding assays showed that the polymerase bound DNA containing uracil 1.5-4.5-fold more strongly than hypoxanthine and site-directed mutagenesis suggested that the same pocket was used for interaction with both deaminated bases. In contrast the polymerase was insensitive to xanthine, the deamination product of guanine. Traces of uracil and hypoxanthine in DNA can lead to inhibition of the PCR by archaeal DNA polymerases, an important consideration for biotechnology applications. Dual recognition of uracil and hypoxanthine may be facilitated by binding the bases with the glycosidic bond in the anti and syn conformation, respectively.
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Affiliation(s)
- Sukhvinder Gill
- The Institute for Cell and Molecular Biosciences (ICaMB), University of Newcastle, Newcastle upon Tyne NE2 4HH, UK
| | - Rory O'Neill
- The Institute for Cell and Molecular Biosciences (ICaMB), University of Newcastle, Newcastle upon Tyne NE2 4HH, UK
| | - Richard J Lewis
- The Institute for Cell and Molecular Biosciences (ICaMB), University of Newcastle, Newcastle upon Tyne NE2 4HH, UK
| | - Bernard A Connolly
- The Institute for Cell and Molecular Biosciences (ICaMB), University of Newcastle, Newcastle upon Tyne NE2 4HH, UK.
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Crystal structure of vaccinia virus uracil-DNA glycosylase reveals dimeric assembly. BMC STRUCTURAL BIOLOGY 2007; 7:45. [PMID: 17605817 PMCID: PMC1936997 DOI: 10.1186/1472-6807-7-45] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/03/2007] [Accepted: 07/02/2007] [Indexed: 11/13/2022]
Abstract
Background Uracil-DNA glycosylases (UDGs) catalyze excision of uracil from DNA. Vaccinia virus, which is the prototype of poxviruses, encodes a UDG (vvUDG) that is significantly different from the UDGs of other organisms in primary, secondary and tertiary structure and characteristic motifs. It adopted a novel catalysis-independent role in DNA replication that involves interaction with a viral protein, A20, to form the processivity factor. UDG:A20 association is essential for assembling of the processive DNA polymerase complex. The structure of the protein must have provisions for such interactions with A20. This paper provides the first glimpse into the structure of a poxvirus UDG. Results Results of dynamic light scattering experiments and native size exclusion chromatography showed that vvUDG is a dimer in solution. The dimeric assembly is also maintained in two crystal forms. The core of vvUDG is reasonably well conserved but the structure contains one additional β-sheet at each terminus. A glycerol molecule is found in the active site of the enzyme in both crystal forms. Interaction of this glycerol molecule with the protein possibly mimics the enzyme-substrate (uracil) interactions. Conclusion The crystal structures reveal several distinctive features of vvUDG. The new structural features may have evolved for adopting novel functions in the replication machinery of poxviruses. The mode of interaction between the subunits in the dimers suggests a possible model for binding to its partner and the nature of the processivity factor in the polymerase complex.
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Greenberg MM. Elucidating DNA damage and repair processes by independently generating reactive and metastable intermediates. Org Biomol Chem 2006; 5:18-30. [PMID: 17164902 DOI: 10.1039/b612729k] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
DNA damage is a double-edged sword. The modifications produced in the biopolymer are associated with aging, and give rise to a variety of diseases, including cancer. DNA is also the target of anti-tumor agents and the most generally used nonsurgical treatment of cancer, ionizing radiation. Agents that damage DNA produce a variety of radicals. Elucidating the chemistry of individual DNA radicals is challenging due to the availability of multiple reactive pathways and complexities inherent with carrying out mechanistic studies on a heterogeneous polymer. The ability to independently generate radicals and their metastable products at defined sites in DNA has greatly facilitated understanding this biologically important chemistry.
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Affiliation(s)
- Marc M Greenberg
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218, USA.
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Wagenknecht HA. Die Suche nach einzelnen DNA-Schäden unter Millionen von Basenpaaren: DNA-Glycosylasen bei der Arbeit. Angew Chem Int Ed Engl 2006. [DOI: 10.1002/ange.200602387] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Wagenknecht HA. The Search for Single DNA Damage among Millions of Base Pairs: DNA Glycosylases Trapped at Work. Angew Chem Int Ed Engl 2006; 45:5583-5. [PMID: 16888824 DOI: 10.1002/anie.200602387] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Bal HP, Cheng J, Murakami A, Tallarico ASC, Wang W, Zhou D, Vasicek TJ, Marasco WA. GITR overexpression on CD4+CD25+ HTLV-1 transformed cells: detection by massively parallel signature sequencing. Biochem Biophys Res Commun 2005; 332:569-84. [PMID: 15896717 DOI: 10.1016/j.bbrc.2005.04.162] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2005] [Accepted: 04/26/2005] [Indexed: 10/25/2022]
Abstract
HTLV-I is the etiologic agent of adult T-cell leukemia (ATL), a fatal T-cell malignancy that is associated with profound immunosuppression. In this study, comprehensive gene expression profiling was performed using massively parallel signature sequencing (MPSS) to investigate virus-host interactions in acutely HTLV-1 transformed cells. The analysis revealed the modulation of numerous genes across different functional classes, many of which have not been previously implicated in HTLV-1 transformation or ATL. Differences in the transcriptomes of transformed cell lines were observed that have provided clues on how different clonal populations of cells respond to virus transformation. Quantitation of HTLV-1 transcription was possible, thus making MPSS a useful tool to study emerging pathogens and unknown microbial causes of human diseases. Importantly, overexpression of GITR, an activation marker that has not been previously reported to be upregulated by HTLV-1-infection or in transformed/leukemic cells and that is associated with the suppressor phenotype of CD4+CD25+ regulatory T-cells (Tregs), was also observed. The deep and quantitative gene expression profile generated by MPSS should provide additional leads for discovery research that can be applied to better understand the pathobiology of HTLV-1 transformation and ATL as well as to developing new therapies.
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Affiliation(s)
- Harshawardhan P Bal
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Harvard Medical School, 44 Binney St., Boston, MA 02115, USA
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Tumey LN, Bom D, Huck B, Gleason E, Wang J, Silver D, Brunden K, Boozer S, Rundlett S, Sherf B, Murphy S, Dent T, Leventhal C, Bailey A, Harrington J, Bennani YL. The identification and optimization of a N-hydroxy urea series of flap endonuclease 1 inhibitors. Bioorg Med Chem Lett 2005; 15:277-81. [PMID: 15603939 DOI: 10.1016/j.bmcl.2004.10.086] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2004] [Revised: 10/28/2004] [Accepted: 10/30/2004] [Indexed: 10/26/2022]
Abstract
Flap endonuclease-1 (FEN1) is a key enzyme involved in base excision repair (BER), a primary pathway utilized by mammalian cells to repair DNA damage. Sensitization to DNA damaging agents is a potential method for the improvement of the therapeutic window of traditional chemotherapeutics. In this paper, we describe the identification and SAR of a series of low nanomolar FEN1 inhibitors. Over 1000-fold specificity was achieved against a related endonuclease, xeroderma pigmentosum G (XPG). Two compounds from this series significantly potentiate the action of methyl methanesulfonate (MMS) and temozolamide in a bladder cancer cell line (T24). To our knowledge, these are the most potent endonuclease inhibitors reported to date.
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Affiliation(s)
- L Nathan Tumey
- Athersys, Inc., 3201 Carnegie Ave., Cleveland, OH 44115, USA.
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