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Inanc B, Fang Q, Andrews JF, Zeng X, Clark J, Li J, Dey NB, Ibrahim M, Sykora P, Yu Z, Braganza A, Verheij M, Jonkers J, Yates NA, Vens C, Sobol RW. TRIP12 governs DNA Polymerase β involvement in DNA damage response and repair. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.08.588474. [PMID: 38645048 PMCID: PMC11030427 DOI: 10.1101/2024.04.08.588474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/23/2024]
Abstract
The multitude of DNA lesion types, and the nuclear dynamic context in which they occur, present a challenge for genome integrity maintenance as this requires the engagement of different DNA repair pathways. Specific 'repair controllers' that facilitate DNA repair pathway crosstalk between double strand break (DSB) repair and base excision repair (BER), and regulate BER protein trafficking at lesion sites, have yet to be identified. We find that DNA polymerase β (Polβ), crucial for BER, is ubiquitylated in a BER complex-dependent manner by TRIP12, an E3 ligase that partners with UBR5 and restrains DSB repair signaling. Here we find that, TRIP12, but not UBR5, controls cellular levels and chromatin loading of Polβ. Required for Polβ foci formation, TRIP12 regulates Polβ involvement after DNA damage. Notably, excessive TRIP12-mediated shuttling of Polβ affects DSB formation and radiation sensitivity, underscoring its precedence for BER. We conclude that the herein discovered trafficking function at the nexus of DNA repair signaling pathways, towards Polβ-directed BER, optimizes DNA repair pathway choice at complex lesion sites.
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Formation of clustered DNA damage in vivo upon irradiation with ionizing radiation: Visualization and analysis with atomic force microscopy. Proc Natl Acad Sci U S A 2022; 119:e2119132119. [PMID: 35324325 PMCID: PMC9060515 DOI: 10.1073/pnas.2119132119] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
DNA damage causes loss of or alterations in genetic information, resulting in cell death or mutations. Ionizing radiations produce local, multiple DNA damage sites called clustered DNA damage. In this study, a complete protocol was established to analyze the damage complexity of clustered DNA damage, wherein damage-containing genomic DNA fragments were selectively concentrated via pulldown, and clustered DNA damage was visualized by atomic force microscopy. It was found that X-rays and Fe ion beams caused clustered DNA damage. Fe ion beams also produced clustered DNA damage with high complexity. Fe ion beam–induced complex DNA double-strand breaks (DSBs) containing one or more base lesion(s) near the DSB end were refractory to repair, implying their lethal effects. Clustered DNA damage is related to the biological effects of ionizing radiation. However, its precise yield and complexity (i.e., number of lesions per damaged site) in vivo remain unknown. To better understand the consequences of clustered DNA damage, a method was established to evaluate its yield and complexity in irradiated cells by atomic force microscopy. This was achieved by isolating and concentrating damaged DNA fragments from purified genomic DNA. It was found that X-rays and Fe ion beams caused clustered DNA damage in human TK6 cells, whereas Fenton's reagents did it less efficiently, highlighting clustered DNA damage as a signature of ionizing radiation. Moreover, Fe ion beams produced clustered DNA damage with high complexity. Remarkably, Fe ion beam–induced complex DNA double-strand breaks (DSBs) containing one or more base lesion(s) near the DSB end were refractory to repair, implying the lethal effect of complex DSBs.
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Structural Insights into the Specificity of 8-Oxo-7,8-dihydro-2′-deoxyguanosine Bypass by Family X DNA Polymerases. Genes (Basel) 2021; 13:genes13010015. [PMID: 35052363 PMCID: PMC8774566 DOI: 10.3390/genes13010015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Revised: 12/13/2021] [Accepted: 12/16/2021] [Indexed: 11/23/2022] Open
Abstract
8-oxo-guanine (8OG) is a common base lesion, generated by reactive oxygen species, which has been associated with human diseases such as cancer, aging-related neurodegenerative disorders and atherosclerosis. 8OG is highly mutagenic, due to its dual-coding potential it can pair both with adenine or cytidine. Therefore, it creates a challenge for DNA polymerases striving to correctly replicate and/or repair genomic or mitochondrial DNA. Numerous structural studies provide insights into the mechanistic basis of the specificity of 8OG bypass by DNA polymerases from different families. Here, we focus on how repair polymerases from Family X (Pols β, λ and µ) engage DNA substrates containing the oxidized guanine. We review structures of binary and ternary complexes for the three polymerases, which represent distinct steps in their catalytic cycles—the binding of the DNA substrate and the incoming nucleotide, followed by its insertion and extension. At each of these steps, the polymerase may favor or exclude the correct C or incorrect A, affecting the final outcome, which varies depending on the enzyme.
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Elbakrawy EM, Mayah A, Hill MA, Kadhim M. Induction of Genomic Instability in a Primary Human Fibroblast Cell Line Following Low-Dose Alpha-Particle Exposure and the Potential Role of Exosomes. BIOLOGY 2020; 10:biology10010011. [PMID: 33379152 PMCID: PMC7824692 DOI: 10.3390/biology10010011] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Accepted: 12/18/2020] [Indexed: 02/07/2023]
Abstract
PURPOSE To study the induction of genomic instability (GI) in the progeny of cell populations irradiated with low doses of alpha-particles and the potential role of exosome-encapsulated bystander signalling. METHODS The induction of GI in HF19 normal fibroblast cells was assessed by determining the formation of micronuclei (MN) in binucleate cells along with using the alkaline comet assay to assess DNA damage. RESULTS Low dose alpha-particle exposure (0.0001-1 Gy) was observed to produce a significant induction of micronuclei and DNA damage shortly after irradiation (assays performed at 5 and 1 h post exposure, respectively). This damage was not only still evident and statistically significant in all irradiated groups after 10 population doublings, but similar trends were observed after 20 population doublings. Exosomes from irradiated cells were also observed to enhance the level of DNA damage in non-irradiated bystander cells at early times. CONCLUSION very low doses of alpha-particles are capable of inducing GI in the progeny of irradiated cells even at doses where <1% of the cells are traversed, where the level of response was similar to that observed at doses where 100% of the cells were traversed. This may have important implications with respect to the evaluation of cancer risk associated with very low-dose alpha-particle exposure and deviation from a linear dose response.
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Affiliation(s)
- Eman Mohammed Elbakrawy
- Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Oxford OX3 0BP, UK; (E.M.E.); (A.M.)
- Department of Radiation Physics, National Center for Radiation Research and Technology, Atomic Energy Authority, 3 Ahmed El-Zomor Al Manteqah Ath Thamenah, Nasr City, Cairo 11787, Egypt
| | - Ammar Mayah
- Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Oxford OX3 0BP, UK; (E.M.E.); (A.M.)
| | - Mark A. Hill
- Gray Laboratories, MRC Oxford Institute for Radiation Oncology, University of Oxford, ORCRB Roosevelt Drive, Oxford OX3 7DQ, UK;
| | - Munira Kadhim
- Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Oxford OX3 0BP, UK; (E.M.E.); (A.M.)
- Correspondence: ; Tel.: +44-0-1865-483954
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Schneider U, Vasi F, Schmidli K, Besserer J. A model of radiation action based on nanodosimetry and the application to ultra-soft X-rays. RADIATION AND ENVIRONMENTAL BIOPHYSICS 2020; 59:439-450. [PMID: 32277259 DOI: 10.1007/s00411-020-00842-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Accepted: 03/30/2020] [Indexed: 06/11/2023]
Abstract
A radiation action model based on nanodosimetry is presented. It is motivated by the finding that the biological effects of various types of ionizing radiation lack a consistent relation with absorbed dose. It is postulated that the common fundamental cause of these effects is the production of elementary sublesions (DSB), which are created at a rate that is proportional to the probability to produce more than two ionisations within a volume of 10 base pairs of the DNA. The concepts of nanodosimetry allow for a quantitative characterization of this process in terms of the cumulative probability F2. The induced sublesions can interact in two ways to produce lethal damage. First, if two or more sublesions accumulate in a locally limited spherical volume of 3-10 nm in diameter, clustered DNA damage is produced. Second, consequent interactions or rearrangements of some of the initial damage over larger distances (~ µm) can produce additional lethal damage. From the comparison of theoretical predictions deduced from this concept with experimental data on relative biological effectiveness, a cluster volume with a diameter of 7.5 nm could be determined. It is shown that, for electrons, the predictions agree well with experimental data over a wide energy range. The only free parameter needed to model cell survival is the intersection cross-section which includes all relevant cell-specific factors. Using ultra-soft X-rays it could be shown that the energy dependence of cell survival is directly governed by the nanodosimetric characteristics of the radiation track structure. The cell survival model derived in this work exhibits exponential cell survival at a high dose and a finite gradient of cell survival at vanishing dose, as well as the dependence on dose-rate.
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Affiliation(s)
- Uwe Schneider
- Department of Physics, Science Faculty, University of Zürich, Zurich, Switzerland.
- Radiotherapy Hirslanden, Witellikerstrasse 40, 8032, Zurich, Switzerland.
| | - Fabiano Vasi
- Department of Physics, Science Faculty, University of Zürich, Zurich, Switzerland
- Radiotherapy Hirslanden, Witellikerstrasse 40, 8032, Zurich, Switzerland
| | - Kevin Schmidli
- Department of Physics, Science Faculty, University of Zürich, Zurich, Switzerland
- Radiotherapy Hirslanden, Witellikerstrasse 40, 8032, Zurich, Switzerland
| | - Jürgen Besserer
- Department of Physics, Science Faculty, University of Zürich, Zurich, Switzerland
- Radiotherapy Hirslanden, Witellikerstrasse 40, 8032, Zurich, Switzerland
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Reuvers TGA, Kanaar R, Nonnekens J. DNA Damage-Inducing Anticancer Therapies: From Global to Precision Damage. Cancers (Basel) 2020; 12:E2098. [PMID: 32731592 PMCID: PMC7463878 DOI: 10.3390/cancers12082098] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 07/24/2020] [Accepted: 07/26/2020] [Indexed: 12/11/2022] Open
Abstract
DNA damage-inducing therapies are of tremendous value for cancer treatment and function by the direct or indirect formation of DNA lesions and subsequent inhibition of cellular proliferation. Of central importance in the cellular response to therapy-induced DNA damage is the DNA damage response (DDR), a protein network guiding both DNA damage repair and the induction of cancer-eradicating mechanisms such as apoptosis. A detailed understanding of DNA damage induction and the DDR has greatly improved our knowledge of the classical DNA damage-inducing therapies, radiotherapy and cytotoxic chemotherapy, and has paved the way for rational improvement of these treatments. Moreover, compounds targeting specific DDR proteins, selectively impairing DNA damage repair in cancer cells, form a promising novel therapy class that is now entering the clinic. In this review, we give an overview of the current state and ongoing developments, and discuss potential avenues for improvement for DNA damage-inducing therapies, with a central focus on the role of the DDR in therapy response, toxicity and resistance. Furthermore, we describe the relevance of using combination regimens containing DNA damage-inducing therapies and how they can be utilized to potentiate other anticancer strategies such as immunotherapy.
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Affiliation(s)
- Thom G. A. Reuvers
- Department of Molecular Genetics, Erasmus MC, Dr. Molenwaterplein 40, 3015 GD Rotterdam, The Netherlands; (T.G.A.R.); (R.K.)
- Department of Radiology and Nuclear Medicine, Erasmus MC, Dr. Molenwaterplein 40, 3015 GD Rotterdam, The Netherlands
| | - Roland Kanaar
- Department of Molecular Genetics, Erasmus MC, Dr. Molenwaterplein 40, 3015 GD Rotterdam, The Netherlands; (T.G.A.R.); (R.K.)
- Oncode Institute, Office Jaarbeurs Innovation Mile (JIM), Jaarbeursplein 6, 3561 AL Utrecht, The Netherlands
| | - Julie Nonnekens
- Department of Molecular Genetics, Erasmus MC, Dr. Molenwaterplein 40, 3015 GD Rotterdam, The Netherlands; (T.G.A.R.); (R.K.)
- Department of Radiology and Nuclear Medicine, Erasmus MC, Dr. Molenwaterplein 40, 3015 GD Rotterdam, The Netherlands
- Oncode Institute, Office Jaarbeurs Innovation Mile (JIM), Jaarbeursplein 6, 3561 AL Utrecht, The Netherlands
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Boguszewska K, Szewczuk M, Kaźmierczak-Barańska J, Karwowski BT. The Similarities between Human Mitochondria and Bacteria in the Context of Structure, Genome, and Base Excision Repair System. Molecules 2020; 25:E2857. [PMID: 32575813 PMCID: PMC7356350 DOI: 10.3390/molecules25122857] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 06/17/2020] [Accepted: 06/19/2020] [Indexed: 02/06/2023] Open
Abstract
Mitochondria emerged from bacterial ancestors during endosymbiosis and are crucial for cellular processes such as energy production and homeostasis, stress responses, cell survival, and more. They are the site of aerobic respiration and adenosine triphosphate (ATP) production in eukaryotes. However, oxidative phosphorylation (OXPHOS) is also the source of reactive oxygen species (ROS), which are both important and dangerous for the cell. Human mitochondria contain mitochondrial DNA (mtDNA), and its integrity may be endangered by the action of ROS. Fortunately, human mitochondria have repair mechanisms that allow protecting mtDNA and repairing lesions that may contribute to the occurrence of mutations. Mutagenesis of the mitochondrial genome may manifest in the form of pathological states such as mitochondrial, neurodegenerative, and/or cardiovascular diseases, premature aging, and cancer. The review describes the mitochondrial structure, genome, and the main mitochondrial repair mechanism (base excision repair (BER)) of oxidative lesions in the context of common features between human mitochondria and bacteria. The authors present a holistic view of the similarities of mitochondria and bacteria to show that bacteria may be an interesting experimental model for studying mitochondrial diseases, especially those where the mechanism of DNA repair is impaired.
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Affiliation(s)
| | | | | | - Bolesław T. Karwowski
- DNA Damage Laboratory of Food Science Department, Faculty of Pharmacy, Medical University of Lodz, ul. Muszynskiego 1, 90-151 Lodz, Poland; (K.B.); (M.S.); (J.K.-B.)
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Hill MA. Radiation Track Structure: How the Spatial Distribution of Energy Deposition Drives Biological Response. Clin Oncol (R Coll Radiol) 2020; 32:75-83. [PMID: 31511190 DOI: 10.1016/j.clon.2019.08.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 07/04/2019] [Accepted: 07/08/2019] [Indexed: 12/22/2022]
Abstract
Ionising radiation is incredibly effective at causing biological effects. This is due to the unique way energy is deposited along highly structured tracks of ionisation and excitation events, which results in correlation with sites of DNA damage from the nanometre to the micrometre scale. Correlation of these events along the track on the nanometre scale results in clustered damage, which not only results in the formation of DNA double-strand breaks (DSB), but also more difficult to repair complex DSB, which include additional damage within a few base pairs. The track structure varies significantly with radiation quality and the increase in relative biological effectiveness observed with increasing linear energy transfer in part corresponds to an increase in the probability and complexity of clustered DNA damage produced. Likewise, correlation over larger scales, associated with packing of DNA and associated chromosomes within the cell nucleus, can also have a major impact on the biological response. The proximity of the correlated damage along the track increases the probability of miss-repair through pairwise interactions resulting in an increase in probability and complexity of DNA fragments/deletions, mutations and chromosomal rearrangements. Understanding the mechanisms underlying the biological effectiveness of ionising radiation can provide an important insight into ways of increasing the efficacy of radiotherapy, as well as the risks associated with exposure. This requires a multi-scale approach for modelling, not only considering the physics of the track structure from the millimetre scale down to the nanometre scale, but also the structural packing of the DNA within the nucleus, the resulting chemistry in the context of the highly reactive environment of the nucleus, together with the subsequent biological response.
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Affiliation(s)
- M A Hill
- MRC Oxford Institute for Radiation Oncology, University of Oxford, Gray Laboratories, Oxford, UK.
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9
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Kaminski AM, Chiruvella KK, Ramsden DA, Kunkel TA, Bebenek K, Pedersen LC. Unexpected behavior of DNA polymerase Mu opposite template 8-oxo-7,8-dihydro-2'-guanosine. Nucleic Acids Res 2019; 47:9410-9422. [PMID: 31435651 DOI: 10.1093/nar/gkz680] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Revised: 07/19/2019] [Accepted: 08/08/2019] [Indexed: 12/17/2022] Open
Abstract
DNA double-strand breaks (DSBs) resulting from reactive oxygen species generated by exposure to UV and ionizing radiation are characterized by clusters of lesions near break sites. Such complex DSBs are repaired slowly, and their persistence can have severe consequences for human health. We have therefore probed DNA break repair containing a template 8-oxo-7,8-dihydro-2'-guanosine (8OG) by Family X Polymerase μ (Pol μ) in steady-state kinetics and cell-based assays. Pol μ tolerates 8OG-containing template DNA substrates, and the filled products can be subsequently ligated by DNA Ligase IV during Nonhomologous end-joining. Furthermore, Pol μ exhibits a strong preference for mutagenic bypass of 8OG by insertion of adenine. Crystal structures reveal that the template 8OG is accommodated in the Pol μ active site with none of the DNA substrate distortions observed for Family X siblings Pols β or λ. Kinetic characterization of template 8OG bypass indicates that Pol μ inserts adenosine nucleotides with weak sugar selectivity and, given the high cellular concentration of ATP, likely performs its role in repair of complex 8OG-containing DSBs using ribonucleotides.
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Affiliation(s)
- Andrea M Kaminski
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Kishore K Chiruvella
- Department of Biochemistry and Biophysics, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27709, USA
| | - Dale A Ramsden
- Department of Biochemistry and Biophysics, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27709, USA
| | - Thomas A Kunkel
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Katarzyna Bebenek
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
| | - Lars C Pedersen
- Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA
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10
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de Ory A, Carabaña C, de Vega M. Bacterial Ligase D preternary-precatalytic complex performs efficient abasic sites processing at double strand breaks during nonhomologous end joining. Nucleic Acids Res 2019; 47:5276-5292. [PMID: 30976810 PMCID: PMC6547435 DOI: 10.1093/nar/gkz265] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Revised: 03/19/2019] [Accepted: 04/04/2019] [Indexed: 11/13/2022] Open
Abstract
Abasic (AP) sites, the most common DNA lesions are frequently associated with double strand breaks (DSBs) and can pose a block to the final ligation. In many prokaryotes, nonhomologous end joining (NHEJ) repair of DSBs relies on a two-component machinery constituted by the ring-shaped DNA-binding Ku that recruits the multicatalytic protein Ligase D (LigD) to the ends. By using its polymerization and ligase activities, LigD fills the gaps that arise after realignment of the ends and seals the resulting nicks. Here, we show the presence of a robust AP lyase activity in the polymerization domain of Bacillus subtilis LigD (BsuLigD) that cleaves AP sites preferentially when they are proximal to recessive 5'-ends. Such a reaction depends on both, metal ions and the formation of a Watson-Crick base pair between the incoming nucleotide and the templating one opposite the AP site. Only after processing the AP site, and in the presence of the Ku protein, BsuLigD catalyzes both, the in-trans addition of the nucleotide to the 3'-end of an incoming primer and the ligation of both ends. These results imply that formation of a preternary-precatalytic complex ensures the coupling of AP sites cleavage to the end-joining reaction by the bacterial LigD.
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Affiliation(s)
- Ana de Ory
- Centro de Biología Molecular 'Severo Ochoa' (Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid), Nicolás Cabrera 1, 28049 Madrid, Spain
| | - Claudia Carabaña
- Centro de Biología Molecular 'Severo Ochoa' (Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid), Nicolás Cabrera 1, 28049 Madrid, Spain
| | - Miguel de Vega
- Centro de Biología Molecular 'Severo Ochoa' (Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid), Nicolás Cabrera 1, 28049 Madrid, Spain
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11
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Henthorn NT, Warmenhoven JW, Sotiropoulos M, Aitkenhead AH, Smith EAK, Ingram SP, Kirkby NF, Chadwick A, Burnet NG, Mackay RI, Kirkby KJ, Merchant MJ. Clinically relevant nanodosimetric simulation of DNA damage complexity from photons and protons. RSC Adv 2019; 9:6845-6858. [PMID: 35518487 PMCID: PMC9061037 DOI: 10.1039/c8ra10168j] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Accepted: 02/21/2019] [Indexed: 12/16/2022] Open
Abstract
Relative Biological Effectiveness (RBE), the ratio of doses between radiation modalities to produce the same biological endpoint, is a controversial and important topic in proton therapy. A number of phenomenological models incorporate variable RBE as a function of Linear Energy Transfer (LET), though a lack of mechanistic description limits their applicability. In this work we take a different approach, using a track structure model employing fundamental physics and chemistry to make predictions of proton and photon induced DNA damage, the first step in the mechanism of radiation-induced cell death. We apply this model to a proton therapy clinical case showing, for the first time, predictions of DNA damage on a patient treatment plan. Our model predictions are for an idealised cell and are applied to an ependymoma case, at this stage without any cell specific parameters. By comparing to similar predictions for photons, we present a voxel-wise RBE of DNA damage complexity. This RBE of damage complexity shows similar trends to the expected RBE for cell kill, implying that damage complexity is an important factor in DNA repair and therefore biological effect. Relative Biological Effectiveness (RBE) is a controversial and important topic in proton therapy. This work uses Monte Carlo simulations of DNA damage for protons and photons to probe this phenomenon, providing a plausible mechanistic understanding.![]()
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Affiliation(s)
- N. T. Henthorn
- Division of Cancer Sciences
- School of Medical Sciences
- Faculty of Biology, Medicine and Health
- The University of Manchester
- UK
| | - J. W. Warmenhoven
- Division of Cancer Sciences
- School of Medical Sciences
- Faculty of Biology, Medicine and Health
- The University of Manchester
- UK
| | - M. Sotiropoulos
- Division of Cancer Sciences
- School of Medical Sciences
- Faculty of Biology, Medicine and Health
- The University of Manchester
- UK
| | - A. H. Aitkenhead
- Division of Cancer Sciences
- School of Medical Sciences
- Faculty of Biology, Medicine and Health
- The University of Manchester
- UK
| | - E. A. K. Smith
- Division of Cancer Sciences
- School of Medical Sciences
- Faculty of Biology, Medicine and Health
- The University of Manchester
- UK
| | - S. P. Ingram
- Division of Cancer Sciences
- School of Medical Sciences
- Faculty of Biology, Medicine and Health
- The University of Manchester
- UK
| | - N. F. Kirkby
- Division of Cancer Sciences
- School of Medical Sciences
- Faculty of Biology, Medicine and Health
- The University of Manchester
- UK
| | - A. L. Chadwick
- Division of Cancer Sciences
- School of Medical Sciences
- Faculty of Biology, Medicine and Health
- The University of Manchester
- UK
| | - N. G. Burnet
- Division of Cancer Sciences
- School of Medical Sciences
- Faculty of Biology, Medicine and Health
- The University of Manchester
- UK
| | - R. I. Mackay
- Division of Cancer Sciences
- School of Medical Sciences
- Faculty of Biology, Medicine and Health
- The University of Manchester
- UK
| | - K. J. Kirkby
- Division of Cancer Sciences
- School of Medical Sciences
- Faculty of Biology, Medicine and Health
- The University of Manchester
- UK
| | - M. J. Merchant
- Division of Cancer Sciences
- School of Medical Sciences
- Faculty of Biology, Medicine and Health
- The University of Manchester
- UK
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12
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Hill MA. Track to the future: historical perspective on the importance of radiation track structure and DNA as a radiobiological target. Int J Radiat Biol 2018; 94:759-768. [PMID: 29219655 PMCID: PMC6113897 DOI: 10.1080/09553002.2017.1387304] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Revised: 09/22/2017] [Accepted: 09/27/2017] [Indexed: 12/04/2022]
Abstract
PURPOSE Understanding the mechanisms behind induced biological response following exposure to ionizing radiation is not only important in assessing the risk associated with human exposure, but potentially can help identify ways of improving the efficacy of radiotherapy. Over the decades, there has been much discussion on what is the key biological target for radiation action and its associated size. It was already known in the 1930s that microscopic features of radiation significantly influenced biological outcomes. This resulted in the development of classic target theory, leading to field of microdosimetry and subsequently nanodosimetry, studying the inhomogeneity and stochastics of interactions, along with the identification of DNA as a key target. CONCLUSIONS Ultimately, the biological response has been found to be dependent on the radiation track structure (spatial and temporal distribution of ionization and excitation events). Clustering of energy deposition on the nanometer scale has been shown to play a critical role in determining biological response, producing not just simple isolated DNA lesions but also complex clustered lesions that are more difficult to repair. The frequency and complexity of these clustered damage sites are typically found to increase with increasing LET. However in order to fully understand the consequences, it is important to look at the relative distribution of these lesions over larger dimensions along the radiation track, up to the micrometer scale. Correlation of energy deposition events and resulting sites of DNA damage can ultimately result in complex gene mutations and complex chromosome rearrangements following repair, with the frequency and spectrum of the resulting rearrangements critically dependent on the spatial and temporal distribution of these sites and therefore the radiation track. Due to limitations in the techniques used to identify these rearrangements it is likely that the full complexity of the genetic rearrangements that occur has yet to be revealed. This paper discusses these issues from a historical perspective, with many of these historical studies still having relevance today. These can not only cast light on current studies but guide future studies, especially with the increasing range of biological techniques available. So, let us build on past knowledge to effectively explore the future.
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Affiliation(s)
- Mark A. Hill
- CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Gray Laboratories, ORCRB Roosevelt Drive, Oxford, UK
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13
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Pawelczak KS, Gavande NS, VanderVere-Carozza PS, Turchi JJ. Modulating DNA Repair Pathways to Improve Precision Genome Engineering. ACS Chem Biol 2018; 13:389-396. [PMID: 29210569 DOI: 10.1021/acschembio.7b00777] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Programmable nucleases like the popular CRISPR/Cas9 system allow for precision genome engineering by inducing a site-specific DNA double strand break (DSB) within a genome. The DSB is repaired by endogenous DNA repair pathways, either nonhomologous end joining (NHEJ) or homology directed repair (HDR). The predominant and error-prone NHEJ pathway often results in small nucleotide insertions or deletions that can be used to construct knockout alleles. Alternatively, HDR activity can result in precise modification incorporating exogenous DNA fragments into the cut site. However, genetic recombination in mammalian systems through the HDR pathway is an inefficient process and requires cumbersome laboratory methods to identify the desired accurate insertion events. This is further compromised by the activity of the competing DNA repair pathway, NHEJ, which repairs the majority of nuclease induced DNA DSBs and also is responsible for mutagenic insertion and deletion events at off-target locations throughout the genome. Various methodologies have been developed to increase the efficiency of designer nuclease-based HDR mediated gene editing. Here, we review these advances toward modulating the activities of the two critical DNA repair pathways, HDR and NHEJ, to enhance precision genome engineering.
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Affiliation(s)
- Katherine S. Pawelczak
- NERx Biosciences, 212 W 10th
Street, Suite A480, Indianapolis, Indiana 46202, United States
| | | | | | - John J. Turchi
- NERx Biosciences, 212 W 10th
Street, Suite A480, Indianapolis, Indiana 46202, United States
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14
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Ramdzan ZM, Ginjala V, Pinder JB, Chung D, Donovan CM, Kaur S, Leduy L, Dellaire G, Ganesan S, Nepveu A. The DNA repair function of CUX1 contributes to radioresistance. Oncotarget 2017; 8:19021-19038. [PMID: 28147323 PMCID: PMC5386666 DOI: 10.18632/oncotarget.14875] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Accepted: 01/19/2017] [Indexed: 01/19/2023] Open
Abstract
Ionizing radiation generates a broad spectrum of oxidative DNA lesions, including oxidized base products, abasic sites, single-strand breaks and double-strand breaks. The CUX1 protein was recently shown to function as an auxiliary factor that stimulates enzymatic activities of OGG1 through its CUT domains. In the present study, we investigated the requirement for CUX1 and OGG1 in the resistance to radiation. Cancer cell survival following ionizing radiation is reduced by CUX1 knockdown and increased by higher CUX1 expression. However, CUX1 knockdown is sufficient by itself to reduce viability in many cancer cell lines that exhibit high levels of reactive oxygen species (ROS). Consequently, clonogenic results expressed relative to that of non-irradiated cells indicate that CUX1 knockdown confers no or modest radiosensitivity to cancer cells with high ROS. A recombinant protein containing only two CUT domains is sufficient for rapid recruitment to DNA damage, acceleration of DNA repair and increased survival following radiation. In agreement with these findings, OGG1 knockdown and treatment of cells with OGG1 inhibitors sensitize cancer cells to radiation. Together, these results validate CUX1 and more specifically the CUT domains as therapeutic targets.
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Affiliation(s)
- Zubaidah M Ramdzan
- Goodman Cancer Research Centre, McGill University, Montreal, Quebec, H3A 1A3, Canada
| | - Vasudeva Ginjala
- Department of Medicine, Rutgers Cancer Institute of New Jersey, Rutgers University, New Brunswick, New Jersey 08903, USA
| | - Jordan B Pinder
- Department of Pathology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Dudley Chung
- Department of Pathology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Caroline M Donovan
- Goodman Cancer Research Centre, McGill University, Montreal, Quebec, H3A 1A3, Canada.,Department of Biochemistry, McGill University, Montreal, Quebec, H3A 1A3, Canada
| | - Simran Kaur
- Goodman Cancer Research Centre, McGill University, Montreal, Quebec, H3A 1A3, Canada.,Department of Biochemistry, McGill University, Montreal, Quebec, H3A 1A3, Canada
| | - Lam Leduy
- Goodman Cancer Research Centre, McGill University, Montreal, Quebec, H3A 1A3, Canada
| | - Graham Dellaire
- Department of Pathology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Shridar Ganesan
- Department of Medicine, Rutgers Cancer Institute of New Jersey, Rutgers University, New Brunswick, New Jersey 08903, USA
| | - Alain Nepveu
- Goodman Cancer Research Centre, McGill University, Montreal, Quebec, H3A 1A3, Canada.,Department of Biochemistry, McGill University, Montreal, Quebec, H3A 1A3, Canada.,Department of Medicine, McGill University, Montreal, Quebec, H3A 1A3, Canada.,Department of Oncology, McGill University, Montreal, Quebec, H3A 1A3, Canada
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15
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Almasan A, Gurkan-Cavusoglu E. Computational analysis of androgen receptor dependent radiosensitivity in prostate cancer. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2017; 2016:1426-1429. [PMID: 28268594 DOI: 10.1109/embc.2016.7590976] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In this study, we quantitatively analyze the mechanism by which androgen deprivation therapy (ADT) is enhancing radiosensitivity in prostate cancer (PCa) patients. It has been shown in laboratory experiments, as well as in patient data in the literature, that the androgen receptor (AR) reduces the effectiveness of ionizing radiation treatment by enhancing the non-homologous end joining (NHEJ) repair of radiation damage. The suppression of AR by ADT suppresses the activity of NHEJ that leads to radiosensitivity in PCa patients. In this paper, we have studied this positive interaction between AR and NHEJ using mathematical models of the NHEJ that we have developed using both the experimental and clinical data for PCa. Our results show that the biological observation of suppression of AR by ADT leading to down-regulation of the first NHEJ protein Ku and NHEJ is a plausible biological mechanism that explains both the experimental and clinical observations in the literature. The presented analysis is the first step in quantitatively analyzing possible treatment scenarios to find the optimal treatment strategies for PCa using the combination treatment with ADT, NHEJ inhibitors, and IR.
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16
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Woods ML, Barnes CP. Mechanistic Modelling and Bayesian Inference Elucidates the Variable Dynamics of Double-Strand Break Repair. PLoS Comput Biol 2016; 12:e1005131. [PMID: 27741226 PMCID: PMC5065155 DOI: 10.1371/journal.pcbi.1005131] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Accepted: 09/05/2016] [Indexed: 12/12/2022] Open
Abstract
DNA double-strand breaks are lesions that form during metabolism, DNA replication and exposure to mutagens. When a double-strand break occurs one of a number of repair mechanisms is recruited, all of which have differing propensities for mutational events. Despite DNA repair being of crucial importance, the relative contribution of these mechanisms and their regulatory interactions remain to be fully elucidated. Understanding these mutational processes will have a profound impact on our knowledge of genomic instability, with implications across health, disease and evolution. Here we present a new method to model the combined activation of non-homologous end joining, single strand annealing and alternative end joining, following exposure to ionising radiation. We use Bayesian statistics to integrate eight biological data sets of double-strand break repair curves under varying genetic knockouts and confirm that our model is predictive by re-simulating and comparing to additional data. Analysis of the model suggests that there are at least three disjoint modes of repair, which we assign as fast, slow and intermediate. Our results show that when multiple data sets are combined, the rate for intermediate repair is variable amongst genetic knockouts. Further analysis suggests that the ratio between slow and intermediate repair depends on the presence or absence of DNA-PKcs and Ku70, which implies that non-homologous end joining and alternative end joining are not independent. Finally, we consider the proportion of double-strand breaks within each mechanism as a time series and predict activity as a function of repair rate. We outline how our insights can be directly tested using imaging and sequencing techniques and conclude that there is evidence of variable dynamics in alternative repair pathways. Our approach is an important step towards providing a unifying theoretical framework for the dynamics of DNA repair processes.
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Affiliation(s)
- Mae L. Woods
- Department of Cell and Developmental Biology, University College London, London, England
| | - Chris P. Barnes
- Department of Cell and Developmental Biology, University College London, London, England
- Department of Genetics, Evolution and Environment, University College London, London, England
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17
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Almohaini M, Chalasani SL, Bafail D, Akopiants K, Zhou T, Yannone SM, Ramsden DA, Hartman MCT, Povirk LF. Nonhomologous end joining of complex DNA double-strand breaks with proximal thymine glycol and interplay with base excision repair. DNA Repair (Amst) 2016; 41:16-26. [PMID: 27049455 DOI: 10.1016/j.dnarep.2016.03.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Revised: 03/04/2016] [Accepted: 03/14/2016] [Indexed: 01/08/2023]
Abstract
DNA double-strand breaks induced by ionizing radiation are often accompanied by ancillary oxidative base damage that may prevent or delay their repair. In order to better define the features that make some DSBs repair-resistant, XLF-dependent nonhomologous end joining of blunt-ended DSB substrates having the oxidatively modified nonplanar base thymine glycol at the first (Tg1), second (Tg2), third (Tg3) or fifth (Tg5) positions from one 3' terminus, was examined in human whole-cell extracts. Tg at the third position had little effect on end-joining even when present on both ends of the break. However, Tg as the terminal or penultimate base was a major barrier to end joining (>10-fold reduction in ligated products) and an absolute barrier when present at both ends. Dideoxy trapping of base excision repair intermediates indicated that Tg was excised from Tg1, Tg2 and Tg3 largely if not exclusively after DSB ligation. However, Tg was rapidly excised from the Tg5 substrate, resulting in a reduced level of DSB ligation, as well as slow concomitant resection of the opposite strand. Ligase reactions containing only purified Ku, XRCC4, ligase IV and XLF showed that ligation of Tg3 and Tg5 was efficient and only partially XLF-dependent, whereas ligation of Tg1 and Tg2 was inefficient and only detectable in the presence of XLF. Overall, the results suggest that promoting ligation of DSBs with proximal base damage may be an important function of XLF, but that Tg can still be a major impediment to repair, being relatively resistant to both trimming and ligation. Moreover, it appears that base excision repair of Tg can sometimes interfere with repair of DSBs that would otherwise be readily rejoined.
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Affiliation(s)
- Mohammed Almohaini
- Department of Pharmacology and Toxicology, Massey Cancer Center, Virginia Commonwealth University, Richmond, VA 23298, United States
| | - Sri Lakshmi Chalasani
- Department of Pharmacology and Toxicology, Massey Cancer Center, Virginia Commonwealth University, Richmond, VA 23298, United States
| | - Duaa Bafail
- Department of Pharmacology and Toxicology, Massey Cancer Center, Virginia Commonwealth University, Richmond, VA 23298, United States
| | - Konstantin Akopiants
- Department of Pharmacology and Toxicology, Massey Cancer Center, Virginia Commonwealth University, Richmond, VA 23298, United States
| | - Tong Zhou
- Department of Pharmacology and Toxicology, Massey Cancer Center, Virginia Commonwealth University, Richmond, VA 23298, United States
| | - Steven M Yannone
- Life Sciences Division, Lawrence Berkeley Laboratory, Berkeley, CA 94720, United States
| | - Dale A Ramsden
- Lineberger Comprehensive Cancer Center, Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599, United States
| | - Matthew C T Hartman
- Department of Chemistry, Massey Cancer Center, Virginia Commonwealth University, Richmond, VA 23298, United States
| | - Lawrence F Povirk
- Department of Pharmacology and Toxicology, Massey Cancer Center, Virginia Commonwealth University, Richmond, VA 23298, United States.
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18
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Shuryak I. Mechanistic Modeling of Dose and Dose Rate Dependences of Radiation-Induced DNA Double Strand Break Rejoining Kinetics in Saccharomyces cerevisiae. PLoS One 2016; 11:e0146407. [PMID: 26741137 PMCID: PMC4711806 DOI: 10.1371/journal.pone.0146407] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Accepted: 12/16/2015] [Indexed: 11/19/2022] Open
Abstract
Mechanistic modeling of DNA double strand break (DSB) rejoining is important for quantifying and medically exploiting radiation-induced cytotoxicity (e.g. in cancer radiotherapy). Most radiation-induced DSBs are quickly-rejoinable and are rejoined within the first 1–2 hours after irradiation. Others are slowly-rejoinable (persist for several hours), and yet others are essentially unrejoinable (persist for >24 hours). The dependences of DSB rejoining kinetics on radiation dose and dose rate remain incompletely understood. We hypothesize that the fraction of slowly-rejoinable and/or unrejoinable DSBs increases with increasing dose/dose rate. This radiation-dependent (RD) model was implemented using differential equations for three DSB classes: quickly-rejoinable, slowly-rejoinable and unrejoinable. Radiation converts quickly-rejoinable to slowly-rejoinable, and slowly-rejoinable to unrejoinable DSBs. We used large published data sets on DSB rejoining in yeast exposed to sparsely-ionizing (electrons and γ-rays, single or split-doses, high or low dose rates) and densely-ionizing (α-particles) radiation to compare the performances of the proposed RD formalism and the established two-lesion kinetic (TLK) model. These yeast DSB rejoining data were measured within the radiation dose range relevant for clonogenic cell survival, whereas in mammalian cells DSB rejoining is usually measured only at supra-lethal doses for technical reasons. The RD model described both sparsely-ionizing and densely-ionizing radiation data much better than the TLK model: by 217 and 14 sample-size-adjusted Akaike information criterion units, respectively. This occurred because: the RD (but not the TLK) model reproduced the observed upwardly-curving dose responses for slowly-rejoinable/unrejoinable DSBs at long times after irradiation; the RD model adequately described DSB yields at both high and low dose rates using one parameter set, whereas the TLK model overestimated low dose rate data. These results support the hypothesis that DSB rejoining is progressively impeded at increasing radiation doses/dose rates.
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Affiliation(s)
- Igor Shuryak
- Center for Radiological Research, Columbia University, New York, NY, United States of America
- * E-mail:
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19
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Bauer NC, Corbett AH, Doetsch PW. The current state of eukaryotic DNA base damage and repair. Nucleic Acids Res 2015; 43:10083-101. [PMID: 26519467 PMCID: PMC4666366 DOI: 10.1093/nar/gkv1136] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Accepted: 10/16/2015] [Indexed: 12/15/2022] Open
Abstract
DNA damage is a natural hazard of life. The most common DNA lesions are base, sugar, and single-strand break damage resulting from oxidation, alkylation, deamination, and spontaneous hydrolysis. If left unrepaired, such lesions can become fixed in the genome as permanent mutations. Thus, evolution has led to the creation of several highly conserved, partially redundant pathways to repair or mitigate the effects of DNA base damage. The biochemical mechanisms of these pathways have been well characterized and the impact of this work was recently highlighted by the selection of Tomas Lindahl, Aziz Sancar and Paul Modrich as the recipients of the 2015 Nobel Prize in Chemistry for their seminal work in defining DNA repair pathways. However, how these repair pathways are regulated and interconnected is still being elucidated. This review focuses on the classical base excision repair and strand incision pathways in eukaryotes, considering both Saccharomyces cerevisiae and humans, and extends to some important questions and challenges facing the field of DNA base damage repair.
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Affiliation(s)
- Nicholas C Bauer
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322, USA Graduate Program in Biochemistry, Cell, and Developmental Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Anita H Corbett
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322, USA Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Paul W Doetsch
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322, USA Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA 30322, USA Department of Radiation Oncology, Emory University School of Medicine, Atlanta, GA 30322, USA Department of Hematology and Medical Oncology, Emory University School of Medicine, Atlanta, GA 30322, USA
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20
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Goodhead DT. Classical approaches to microdosimetry, with example of use in radiation protection, medicine and mechanistic understanding. RADIATION PROTECTION DOSIMETRY 2015; 166:276-281. [PMID: 25897134 DOI: 10.1093/rpd/ncv194] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Microdosimetry is the study and application of the microscopic features and stochastics of ionising radiations that cannot be described by the average macroscopic quantity absorbed dose. Microdosimetry is intimately related to radiation quality, but it also encompasses the inhomogeneities of interactions and energy depositions within a single radiation type. A variety of past and current approaches will be summarised and some examples given of implications to radiation protection and medicine, as well as to basic mechanistic studies of radiation effects.
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Affiliation(s)
- D T Goodhead
- Medical Research Council, Harwell, Didcot OX11 0RD, UK
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21
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Watanabe R, Rahmanian S, Nikjoo H. Spectrum of Radiation-Induced Clustered Non-DSB Damage - A Monte Carlo Track Structure Modeling and Calculations. Radiat Res 2015; 183:525-40. [PMID: 25909147 DOI: 10.1667/rr13902.1] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The aim of this report is to present the spectrum of initial radiation-induced cellular DNA damage [with particular focus on non-double-strand break (DSB) damage] generated by computer simulations. The radiation types modeled in this study were monoenergetic electrons (100 eV-1.5 keV), ultrasoft X-ray photons Ck, AlK and TiK, as well as some selected ions including 3.2 MeV/u proton; 0.74 and 2.4 MeV/u helium ions; 29 MeV/u nitrogen ions and 950 MeV/u iron ions. Monte Carlo track structure methods were used to simulate damage induction by these radiation types in a cell-mimetic condition from a single-track action. The simulations took into account the action of direct energy deposition events and the reaction of hydroxyl radicals on atomistic linear B-DNA segments of a few helical turns including the water of hydration. Our results permitted the following conclusions: a. The absolute levels of different types of damage [base damage, simple and complex single-strand breaks (SSBs) and DSBs] vary depending on the radiation type; b. Within each damage class, the relative proportions of simple and complex damage vary with radiation type, the latter being higher with high-LET radiations; c. Overall, for both low- and high-LET radiations, the ratios of the yields of base damage to SSBs are similar, being about 3.0 ± 0.2; d. Base damage contributes more to the complexity of both SSBs and DSBs, than additional SSB damage and this is true for both low- and high-LET radiations; and e. The average SSB/DSB ratio for low-LET radiations is about 18, which is about 5 times higher than that for high-LET radiations. The hypothesis that clustered DNA damage is more difficult for cells to repair has gained currency among radiobiologists. However, as yet, there is no direct in vivo experimental method to validate the dependence of kinetics of DNA repair on DNA damage complexity (both DSB and non-DSB types). The data on the detailed spectrum of DNA damage presented here, in particular the non-DSB type, provide a good basis for testing mechanistic models of DNA repair kinetics such as base excision repair.
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Affiliation(s)
- Ritsuko Watanabe
- a Research Group for Radiation Effect Analysis, Japan Atomic Energy Agency, Tokai, Ibaraki, 319-1195, Japan
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22
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Strande NT, Carvajal-Garcia J, Hallett RA, Waters CA, Roberts SA, Strom C, Kuhlman B, Ramsden DA. Requirements for 5'dRP/AP lyase activity in Ku. Nucleic Acids Res 2014; 42:11136-43. [PMID: 25200085 PMCID: PMC4176175 DOI: 10.1093/nar/gku796] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The non-homologous end joining (NHEJ) pathway is used in diverse species to repair chromosome breaks, and is defined in part by a requirement for Ku. We previously demonstrated mammalian Ku has intrinsic 5′ deoxyribosephosphate (5′dRP) and apurinic/apyrimidinic (AP) lyase activity, and showed this activity is important for excising abasic site damage from ends. Here we employ systematic mutagenesis to clarify the protein requirements for this activity. We identify lysine 31 in the 70 kD subunit (Ku70 K31) as the primary candidate nucleophile required for catalysis, but additional mutation of Ku70 K160 and six other lysines within Ku80 were required to eliminate all activity. Ku from Saccharomyces cerevisiae also possesses 5′dRP/AP lyase activity, and robust activity was also reliant on lysines in Ku70 analogous to K31 and K160. By comparison, these lysines are not conserved in Xenopus laevis Ku, and Ku from this species has negligible activity. A role for residues flanking Ku70 K31 in expanding the range of abasic site contexts that can be used as substrate was also identified. Our results suggest an active site well located to provide the substrate specificity required for its biological role.
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Affiliation(s)
- Natasha T Strande
- Lineberger Comprehensive Cancer Center, Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27514, USA
| | - Juan Carvajal-Garcia
- Lineberger Comprehensive Cancer Center, Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27514, USA
| | - Ryan A Hallett
- Lineberger Comprehensive Cancer Center, Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27514, USA
| | - Crystal A Waters
- Lineberger Comprehensive Cancer Center, Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27514, USA Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Steven A Roberts
- Lineberger Comprehensive Cancer Center, Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27514, USA
| | - Christina Strom
- Lineberger Comprehensive Cancer Center, Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27514, USA
| | - Brian Kuhlman
- Lineberger Comprehensive Cancer Center, Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27514, USA
| | - Dale A Ramsden
- Lineberger Comprehensive Cancer Center, Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27514, USA Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC 27599, USA
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23
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Patel A, Burton DGA, Halvorsen K, Balkan W, Reiner T, Perez-Stable C, Cohen A, Munoz A, Giribaldi MG, Singh S, Robbins DJ, Nguyen DM, Rai P. MutT Homolog 1 (MTH1) maintains multiple KRAS-driven pro-malignant pathways. Oncogene 2014; 34:2586-96. [PMID: 25023700 PMCID: PMC4294948 DOI: 10.1038/onc.2014.195] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Revised: 05/16/2014] [Accepted: 05/28/2014] [Indexed: 12/19/2022]
Abstract
Oncogenic RAS promotes production of reactive oxygen species (ROS), which mediate pro-malignant signaling but can also trigger DNA damage-induced tumor suppression. Thus RAS-driven tumor cells require redox-protective mechanisms to mitigate the damaging aspects of ROS. Here, we show that MutT Homolog 1 (MTH1), the mammalian 8-oxodGTPase that sanitizes oxidative damage in the nucleotide pool, is important for maintaining several KRAS-driven pro-malignant traits in a nonsmall cell lung carcinoma (NSCLC) model. MTH1 suppression in KRAS-mutant NSCLC cells impairs proliferation and xenograft tumor formation. Furthermore, MTH1 levels modulate KRAS-induced transformation of immortalized lung epithelial cells. MTH1 expression is upregulated by oncogenic KRAS and correlates positively with high KRAS levels in NSCLC human tumors. At a molecular level, in p53-competent KRAS-mutant cells, MTH1 loss provokes DNA damage and induction of oncogene-induced senescence. In p53-nonfunctional KRAS-mutant cells, MTH1 suppression does not produce DNA damage but reduces proliferation and leads to an adaptive decrease in KRAS expression levels. Thus, MTH1 not only enables evasion of oxidative DNA damage and its consequences, but can also function as a molecular rheostat for maintaining oncogene expression at optimal levels. Accordingly, our results indicate MTH1 is a novel and critical component of oncogenic KRAS-associated malignancy and its inhibition is likely to yield significant tumor-suppressive outcomes in KRAS-driven tumors.
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Affiliation(s)
- A Patel
- Department of Medicine, University of Miami Leonard M. Miller School of Medicine, Miami, FL, USA
| | - D G A Burton
- Department of Medicine, University of Miami Leonard M. Miller School of Medicine, Miami, FL, USA
| | - K Halvorsen
- Department of Medicine, University of Miami Leonard M. Miller School of Medicine, Miami, FL, USA
| | - W Balkan
- Department of Medicine, University of Miami Leonard M. Miller School of Medicine, Miami, FL, USA
| | - T Reiner
- Geriatric Research, Education and Clinical Center, Bruce W. Carter Veterans Affairs Medical Center, Miami, FL, USA
| | - C Perez-Stable
- 1] Department of Medicine, University of Miami Leonard M. Miller School of Medicine, Miami, FL, USA [2] Geriatric Research, Education and Clinical Center, Bruce W. Carter Veterans Affairs Medical Center, Miami, FL, USA [3] Sylvester Comprehensive Cancer Center, University of Miami Leonard M. Miller School of Medicine, FL, USA
| | - A Cohen
- 1] Department of Medicine, University of Miami Leonard M. Miller School of Medicine, Miami, FL, USA [2] David and Sheila Fuente Graduate Program in Cancer Biology, University of Miami Leonard M. Miller School of Medicine, Miami, FL, USA
| | - A Munoz
- Department of Medicine, University of Miami Leonard M. Miller School of Medicine, Miami, FL, USA
| | - M G Giribaldi
- Department of Medicine, University of Miami Leonard M. Miller School of Medicine, Miami, FL, USA
| | - S Singh
- Department of Surgery, University of Miami Leonard M. Miller School of Medicine, Miami, FL, USA
| | - D J Robbins
- 1] Sylvester Comprehensive Cancer Center, University of Miami Leonard M. Miller School of Medicine, FL, USA [2] Department of Surgery, University of Miami Leonard M. Miller School of Medicine, Miami, FL, USA
| | - D M Nguyen
- 1] Sylvester Comprehensive Cancer Center, University of Miami Leonard M. Miller School of Medicine, FL, USA [2] Department of Surgery, University of Miami Leonard M. Miller School of Medicine, Miami, FL, USA
| | - P Rai
- 1] Department of Medicine, University of Miami Leonard M. Miller School of Medicine, Miami, FL, USA [2] Sylvester Comprehensive Cancer Center, University of Miami Leonard M. Miller School of Medicine, FL, USA
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24
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The fidelity of the ligation step determines how ends are resolved during nonhomologous end joining. Nat Commun 2014; 5:4286. [PMID: 24989324 PMCID: PMC4107315 DOI: 10.1038/ncomms5286] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Accepted: 06/03/2014] [Indexed: 12/21/2022] Open
Abstract
Nonhomologous end joining (NHEJ) can effectively resolve chromosome breaks despite diverse end structures, but it is unclear how the steps employed for resolution are determined. We sought to address this question by analyzing cellular NHEJ of ends with systematically mispaired and damaged termini. We show NHEJ is uniquely proficient at bypassing subtle terminal mispairs and radiomimetic damage by direct ligation. Nevertheless, bypass ability varies widely, with increases in mispair severity gradually reducing bypass products from 85% to 6%. End-processing by nucleases and polymerases is increased to compensate, though paths with the fewest number of steps to generate a substrate suitable for ligation are favored. Thus, both the frequency and nature of end processing are tailored to meet the needs of the ligation step. We propose a model where the ligase organizes all steps during NHEJ within the stable paired-end complex to limit end processing and associated errors.
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25
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Waters CA, Strande NT, Wyatt DW, Pryor JM, Ramsden DA. Nonhomologous end joining: a good solution for bad ends. DNA Repair (Amst) 2014; 17:39-51. [PMID: 24630899 DOI: 10.1016/j.dnarep.2014.02.008] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2013] [Revised: 01/27/2014] [Accepted: 02/10/2014] [Indexed: 12/27/2022]
Abstract
Double strand breaks pose unique problems for DNA repair, especially when broken ends possess complex structures that interfere with standard DNA transactions. Nonhomologous end joining can use multiple strategies to solve these problems. It further uses sophisticated means to ensure the strategy chosen provides the ideal balance of flexibility and accuracy.
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Affiliation(s)
- Crystal A Waters
- Department of Biochemistry and Biophysics and Curriculum in Genetics and Molecular Biology, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA.
| | - Natasha T Strande
- Department of Biochemistry and Biophysics and Curriculum in Genetics and Molecular Biology, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA.
| | - David W Wyatt
- Department of Biochemistry and Biophysics and Curriculum in Genetics and Molecular Biology, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA.
| | - John M Pryor
- Department of Biochemistry and Biophysics and Curriculum in Genetics and Molecular Biology, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA.
| | - Dale A Ramsden
- Department of Biochemistry and Biophysics and Curriculum in Genetics and Molecular Biology, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA.
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26
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Modeling damage complexity-dependent non-homologous end-joining repair pathway. PLoS One 2014; 9:e85816. [PMID: 24520318 PMCID: PMC3919704 DOI: 10.1371/journal.pone.0085816] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Accepted: 12/02/2013] [Indexed: 11/19/2022] Open
Abstract
Non-homologous end joining (NHEJ) is the dominant DNA double strand break (DSB) repair pathway and involves several repair proteins such as Ku, DNA-PKcs, and XRCC4. It has been experimentally shown that the choice of NHEJ proteins is determined by the complexity of DSB. In this paper, we built a mathematical model, based on published data, to study how NHEJ depends on the damage complexity. Under an appropriate set of parameters obtained by minimization technique, we can simulate the kinetics of foci track formation in fluorescently tagged mammalian cells, Ku80-EGFP and DNA-PKcs-YFP for simple and complex DSB repair, respectively, in good agreement with the published experimental data, supporting the notion that simple DSB undergo fast repair in a Ku-dependent, DNA-PKcs-independent manner, while complex DSB repair requires additional DNA-PKcs for end processing, resulting in its slow repair, additionally resulting in slower release rate of Ku and the joining rate of complex DNA ends. Based on the numerous experimental descriptions, we investigated several models to describe the kinetics for complex DSB repair. An important prediction of our model is that the rejoining of complex DSBs is through a process of synapsis formation, similar to a second order reaction between ends, rather than first order break filling/joining. The synapsis formation (SF) model allows for diffusion of ends before the synapsis formation, which is precluded in the first order model by the rapid coupling of ends. Therefore, the SF model also predicts the higher number of chromosomal aberrations observed with high linear energy transfer (LET) radiation due to the higher proportion of complex DSBs compared to low LET radiation, and an increased probability of misrejoin following diffusion before the synapsis is formed, while the first order model does not provide a mechanism for the increased effectiveness in chromosomal aberrations observed.
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27
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Biological consequences of radiation-induced DNA damage: relevance to radiotherapy. Clin Oncol (R Coll Radiol) 2013; 25:578-85. [PMID: 23849504 DOI: 10.1016/j.clon.2013.06.007] [Citation(s) in RCA: 416] [Impact Index Per Article: 37.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Accepted: 06/12/2013] [Indexed: 12/21/2022]
Abstract
DNA damage of exposed tumour tissue leading to cell death is one of the detrimental effects of ionising radiation that is exploited, with beneficial consequences, for radiotherapy. The pattern of the discrete energy depositions during passage of the ionising track of radiation defines the spatial distribution of lesions induced in DNA with a fraction of the DNA damage sites containing clusters of lesions, formed over a few nanometres, against a background of endogenously induced individual lesions. These clustered DNA damage sites, which may be considered as a signature of ionising radiation, underlie the deleterious biological consequences of ionising radiation. The concepts developed rely in part on the fact that ionising radiation creates significant levels of clustered DNA damage, including complex double-strand breaks (DSB), to kill tumour cells as clustered damage sites are difficult to repair. This reduced repairability of clustered DNA damage using specific repair pathways is exploitable in radiotherapy for the treatment of cancer. We discuss some potential strategies to enhance radiosensitivity by targeting the repair pathways of radiation-induced clustered damage and complex DNA DSB, through inhibition of specific proteins that are not required in the repair pathways for endogenous damage. The variety and severity of DNA damage from ionising radiation is also influenced by the tumour microenvironment, being especially sensitive to the oxygen status of the cells. For instance, nitric oxide is known to influence the types of damage induced by radiation under hypoxic conditions. A potential strategy based on bioreductive activation of pro-drugs to release nitric oxide is discussed as an approach to deliver nitric oxide to hypoxic tumours during radiotherapy. The ultimate aim of this review is to stimulate thinking on how knowledge of the complexity of radiation-induced DNA damage may contribute to the development of adjuncts to radiotherapy.
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28
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Schipler A, Iliakis G. DNA double-strand-break complexity levels and their possible contributions to the probability for error-prone processing and repair pathway choice. Nucleic Acids Res 2013; 41:7589-605. [PMID: 23804754 PMCID: PMC3763544 DOI: 10.1093/nar/gkt556] [Citation(s) in RCA: 196] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Although the DNA double-strand break (DSB) is defined as a rupture in the double-stranded DNA molecule that can occur without chemical modification in any of the constituent building blocks, it is recognized that this form is restricted to enzyme-induced DSBs. DSBs generated by physical or chemical agents can include at the break site a spectrum of base alterations (lesions). The nature and number of such chemical alterations define the complexity of the DSB and are considered putative determinants for repair pathway choice and the probability that errors will occur during this processing. As the pathways engaged in DSB processing show distinct and frequently inherent propensities for errors, pathway choice also defines the error-levels cells opt to accept. Here, we present a classification of DSBs on the basis of increasing complexity and discuss how complexity may affect processing, as well as how it may cause lethal or carcinogenic processing errors. By critically analyzing the characteristics of DSB repair pathways, we suggest that all repair pathways can in principle remove lesions clustering at the DSB but are likely to fail when they encounter clusters of DSBs that cause a local form of chromothripsis. In the same framework, we also analyze the rational of DSB repair pathway choice.
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Affiliation(s)
- Agnes Schipler
- Institute of Medical Radiation Biology, University of Duisburg-Essen Medical School, 45122 Essen, Germany
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29
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Reynolds P, Botchway SW, Parker AW, O'Neill P. Spatiotemporal dynamics of DNA repair proteins following laser microbeam induced DNA damage - when is a DSB not a DSB? Mutat Res 2013; 756:14-20. [PMID: 23688615 PMCID: PMC4028083 DOI: 10.1016/j.mrgentox.2013.05.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Accepted: 05/02/2013] [Indexed: 12/19/2022]
Abstract
The formation of DNA lesions poses a constant threat to cellular stability. Repair of endogenously and exogenously produced lesions has therefore been extensively studied, although the spatiotemporal dynamics of the repair processes has yet to be fully understood. One of the most recent advances to study the kinetics of DNA repair has been the development of laser microbeams to induce and visualize recruitment and loss of repair proteins to base damage in live mammalian cells. However, a number of studies have produced contradictory results that are likely caused by the different laser systems used reflecting in part the wavelength dependence of the damage induced. Additionally, the repair kinetics of laser microbeam induced DNA lesions have generally lacked consideration of the structural and chemical complexity of the DNA damage sites, which are known to greatly influence their reparability. In this review, we highlight the key considerations when embarking on laser microbeam experiments and interpreting the real time data from laser microbeam irradiations. We compare the repair kinetics from live cell imaging with biochemical and direct quantitative cellular measurements for DNA repair.
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Affiliation(s)
- Pamela Reynolds
- Gray Institute for Radiation Oncology and Biology, Department of Oncology, University of Oxford, Oxford OX3 7DQ, UK
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30
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Woods D, Turchi JJ. Chemotherapy induced DNA damage response: convergence of drugs and pathways. Cancer Biol Ther 2013. [PMID: 23380594 DOI: 10.4161/cbt23761] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/24/2023] Open
Abstract
Chemotherapeutics target rapidly dividing cancer cells by directly or indirectly inducing DNA damage. Upon recognizing DNA damage, cells initiate a variety of signaling pathways collectively referred to as the DNA damage response (DDR). Interestingly, the pathways used to elicit this response are as varied as the types of DNA damage induced. However, the activation of these various pathways has similar results including DNA repair, suppression of global general translation, cell cycle arrest and, ultimately, either cell survival or cell death. This review will focus on a series of chemotherapy-induced DNA lesions and highlight recent advances in our understanding of the DDR, the DNA repair pathways it activates and the cellular consequences of these converging pathways.
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Affiliation(s)
- Derek Woods
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, USA
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31
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Loucas BD, Cornforth MN. The LET dependence of unrepaired chromosome damage in human cells: a break too far? Radiat Res 2013; 179:393-405. [PMID: 23578187 PMCID: PMC6058738 DOI: 10.1667/rr3159.2] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cytogenetic damage is among the few radiobiological end points that allow a precise distinction to be made between misrepaired damage, represented by exchange-type aberrations such as dicentrics and translocations, and unrepaired damage that leads to "open breaks". This latter category includes both terminal deletions and incomplete exchanges, whose different mechanisms of formation can be recognized by multicolor fluorescence in situ hybridization (mFISH). mFISH was used to examine the yields of chromosome aberrations at the first postirradiation mitosis in human fibroblasts and lymphocytes irradiated with ¹³⁷Cs γ rays, a radiation of low-linear energy transfer (LET), and two sources of high-LET radiation: α particles from ²³⁸Pu and 1 GeV/amu ⁵⁶Fe ions. In agreement with previous studies, our results show that irrespective of radiation quality, the overall level of misrepaired damage exceeds that of unrepaired damage by a large margin. The unrepaired component of damage produced by γ rays and α particles was remarkably similar, about 5%. On that basis it is difficult to justify the popular notion that the strong LET-dependence for aberration formation is due to unrepaired DNA double-strand breaks (DSBs) that, by virtue of their complexity at the nanometer scale, are qualitatively different in nature. In marked contrast, this unrejoined component rose to about 14% after exposure to Fe ions. A closer look at the unrepaired component revealed that most of this roughly threefold difference was derived from incomplete exchanges. Despite vast differences in LET, unrejoined breaks from incomplete exchanges were far more likely to occur among exchanges that involved more than two breakpoints. We attempted to reconcile these observations in the form of a hypothesis that predicts that exchanges, irrespective of LET, should exhibit an increasing tendency for incompleteness as the number of initial breaks destined to take part in the exchange increases. This effect, we argue is not caused by the number of initial breaks per se, but instead reflects the maximum distance over which proximate breaks can interact. This adds a spatial aspect to multi-break interactions that we call "A Break Too Far".
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Affiliation(s)
- Bradford D Loucas
- Department of Radiation Oncology, The University of Texas Medical Branch, Galveston, Texas 77555, USA.
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32
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Malyarchuk S, Castore R, Shi R, Harrison L. Artemis is required to improve the accuracy of repair of double-strand breaks with 5'-blocked termini generated from non-DSB-clustered lesions. Mutagenesis 2013; 28:357-66. [PMID: 23448902 DOI: 10.1093/mutage/get009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Clustered DNA lesions are defined as ≥2 damage events within 20 bp. Oxidised bases, abasic (AP) sites, single-strand breaks and double-strand breaks (DSBs) exist in radiation-induced clusters, and these lesions are more difficult to repair and can be more mutagenic than single lesions. Understanding clustered lesion repair is therefore important for the design of complementary treatments to enhance radiotherapy. Non-DSB-clustered lesions consisting of opposing AP sites can be converted to DSBs by base excision repair, and non-homologous end-joining (NHEJ) plays a role in repairing these DSBs. Artemis is an endonuclease that removes blocking groups from DSB termini during NHEJ. Hence, we hypothesised that Artemis plays a role in the processing of DSBs or complex DSBs generated from non-DSB-clustered lesions. We examined the repair of clusters containing two or three lesions in wild-type (WT) or Artemis-deficient (ART(-/-)) mouse fibroblasts using a reporter plasmid. Each cluster contained two opposing tetrahydrofurans (an AP site analogue), which AP endonuclease can convert to a DSB with blocked 5' termini. Loss of Artemis did not decrease plasmid survival, but did result in more mutagenic repair with plasmids containing larger deletions. This increase in deletions did not occur with ClaI-linearised plasmid. Since Mre11 has been implicated in deletional NHEJ, we used small interfering RNA to reduce Mre11 in WT and ART(-/-) cells, but decreasing Mre11 did not change the size of deletions in the repair products. This work implicates Artemis in limiting the deletions introduced during repair of 5'-blocked termini DSBs generated from non-DSB-clustered lesions. Decreasing repair accuracy without decreasing repair capacity could result in mutated cells surviving irradiation. Inhibiting Artemis in normal cells could promote carcinogenesis, while in tumour cells enhanced mutagenic repair following irradiation could promote tumour recurrence.
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Affiliation(s)
- Svitlana Malyarchuk
- Department of Molecular and Cellular Physiology, Louisiana Health Sciences Center, 1501 Kings Highway, Shreveport, LA 71130, USA
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33
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Woods D, Turchi JJ. Chemotherapy induced DNA damage response: convergence of drugs and pathways. Cancer Biol Ther 2013; 14:379-89. [PMID: 23380594 PMCID: PMC3672181 DOI: 10.4161/cbt.23761] [Citation(s) in RCA: 182] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Chemotherapeutics target rapidly dividing cancer cells by directly or indirectly inducing DNA damage. Upon recognizing DNA damage, cells initiate a variety of signaling pathways collectively referred to as the DNA damage response (DDR). Interestingly, the pathways used to elicit this response are as varied as the types of DNA damage induced. However, the activation of these various pathways has similar results including DNA repair, suppression of global general translation, cell cycle arrest and, ultimately, either cell survival or cell death. This review will focus on a series of chemotherapy-induced DNA lesions and highlight recent advances in our understanding of the DDR, the DNA repair pathways it activates and the cellular consequences of these converging pathways.
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Affiliation(s)
- Derek Woods
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, USA
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34
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Strande NT, Waters CA, Ramsden DA. Resolution of complex ends by Nonhomologous end joining - better to be lucky than good? Genome Integr 2012; 3:10. [PMID: 23276302 PMCID: PMC3547747 DOI: 10.1186/2041-9414-3-10] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Accepted: 12/16/2012] [Indexed: 12/03/2022] Open
Abstract
The Nonhomologous end joining pathway is essential for efficient repair of chromosome double strand breaks. This pathway consequently plays a key role in cellular resistance to break-inducing exogenous agents, as well as in the developmentally-programmed recombinations that are required for adaptive immunity. Chromosome breaks often have complex or “dirty” end structures that can interfere with the critical ligation step in this pathway; we review here how Nonhomologous end joining resolves such breaks.
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Affiliation(s)
- Natasha Tiffany Strande
- Lineberger Comprehensive Cancer Center, Department of Biochemistry and Biophysics and Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
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35
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Reynolds P, Anderson JA, Harper JV, Hill MA, Botchway SW, Parker AW, O'Neill P. The dynamics of Ku70/80 and DNA-PKcs at DSBs induced by ionizing radiation is dependent on the complexity of damage. Nucleic Acids Res 2012; 40:10821-31. [PMID: 23012265 PMCID: PMC3510491 DOI: 10.1093/nar/gks879] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
DNA double-strand breaks (DSBs) are biologically one of the most important cellular lesions and possess varying degrees of chemical complexity. The notion that the repairability of more chemically complex DSBs is inefficient led to the concept that the extent of DSB complexity underlies the severity of the biological consequences. The repair of DSBs by non-homologous end joining (NHEJ) has been extensively studied but it remains unknown whether more complex DSBs require a different sub-set of NHEJ protein for their repair compared with simple DSBs. To address this, we have induced DSBs in fluorescently tagged mammalian cells (Ku80-EGFP, DNA-PKcs-YFP or XRCC4-GFP, key proteins in NHEJ) using ultra-soft X-rays (USX) or multi-photon near infrared (NIR) laser irradiation. We have shown in real-time that simple DSBs, induced by USX or NIR microbeam irradiation, are repaired rapidly involving Ku70/80 and XRCC4/Ligase IV/XLF. In contrast, DSBs with greater chemical complexity are repaired slowly involving not only Ku70/80 and XRCC4/Ligase IV/XLF but also DNA-PKcs. Ataxia telangiectasia-mutated inhibition only retards repair of the more chemically complex DSBs which require DNA-PKcs. In summary, the repair of DSBs by NHEJ is highly regulated with pathway choice and kinetics of repair dependent on the chemical complexity of the DSB.
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Affiliation(s)
- Pamela Reynolds
- Department of Oncology, Gray Institute for Radiation Oncology & Biology, University of Oxford, Oxford OX3 7DQ, UK
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36
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Møllersen L, Rowe AD, Illuzzi JL, Hildrestrand GA, Gerhold KJ, Tveterås L, Bjølgerud A, Wilson DM, Bjørås M, Klungland A. Neil1 is a genetic modifier of somatic and germline CAG trinucleotide repeat instability in R6/1 mice. Hum Mol Genet 2012; 21:4939-47. [PMID: 22914735 PMCID: PMC3607484 DOI: 10.1093/hmg/dds337] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Huntington's disease (HD) is a progressive neurodegenerative disorder caused by trinucleotide repeat (TNR) expansions. We show here that somatic TNR expansions are significantly reduced in several organs of R6/1 mice lacking exon 2 of Nei-like 1 (Neil1) (R6/1/Neil1−/−), when compared with R6/1/Neil1+/+ mice. Somatic TNR expansion is measured by two different methods, namely mean repeat change and instability index. Reduced somatic expansions are more pronounced in male R6/1/Neil1−/− mice, although expansions are also significantly reduced in brain regions of female R6/1/Neil1−/− mice. In addition, we show that the lack of functional Neil1 significantly reduces germline expansion in R6/1 male mice. In vitro, purified human NEIL1 protein binds and excises 5-hydroxycytosine in duplex DNA more efficiently than in hairpin substrates. NEIL1 excision of cytosine-derived oxidative lesions could therefore be involved in initiating the process of TNR expansion, although other DNA modifications might also contribute. Altogether, these results imply that Neil1 contributes to germline and somatic HD CAG repeat expansion.
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Affiliation(s)
- Linda Møllersen
- Institute of Medical Microbiology, Oslo University Hospital, Rikshospitalet, Sognsvannsveien 20, Oslo, Norway
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37
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Strande N, Roberts SA, Oh S, Hendrickson EA, Ramsden DA. Specificity of the dRP/AP lyase of Ku promotes nonhomologous end joining (NHEJ) fidelity at damaged ends. J Biol Chem 2012; 287:13686-93. [PMID: 22362780 DOI: 10.1074/jbc.m111.329730] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nonhomologous end joining (NHEJ) is essential for efficient repair of chromosome breaks. However, the NHEJ ligation step is often obstructed by break-associated nucleotide damage, including base loss (abasic site or 5'-dRP/AP sites). Ku, a 5'-dRP/AP lyase, can excise such damage at ends in preparation for the ligation step. We show here that this activity is greatest if the abasic site is within a short 5' overhang, when this activity is necessary and sufficient to prepare such termini for ligation. In contrast, Ku is less active near 3' strand termini, where excision would leave a ligation-blocking α,β-unsaturated aldehyde. The Ku AP lyase activity is also strongly suppressed by as little as two paired bases 5' of the abasic site. Importantly, in vitro end joining experiments show that abasic sites significantly embedded in double-stranded DNA do not block the NHEJ ligation step. Suppression of the excision activity of Ku in this context therefore is not essential for ligation and further helps NHEJ retain terminal sequence in junctions. We show that the DNA between the 5' terminus and the abasic site can also be retained in junctions formed by cellular NHEJ, indicating that these sites are at least partly resistant to other abasic site-cleaving activities as well. High levels of the 5'-dRP/AP lyase activity of Ku are thus restricted to substrates where excision of an abasic site is required for ligation, a degree of specificity that promotes more accurate joining.
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Affiliation(s)
- Natasha Strande
- Lineberger Comprehensive Cancer Center, Department of Biochemistry and Biophysics and Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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38
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Magnander K, Elmroth K. Biological consequences of formation and repair of complex DNA damage. Cancer Lett 2012; 327:90-6. [PMID: 22353687 DOI: 10.1016/j.canlet.2012.02.013] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2011] [Revised: 02/11/2012] [Accepted: 02/13/2012] [Indexed: 12/29/2022]
Abstract
Endogenous processes or genotoxic agents can induce many types of single DNA damage (single-strand breaks, oxidized bases and abasic sites). In addition, ionizing radiation induces complex lesions such as double-strand breaks and clustered damage. To preserve the genomic stability and prevent carcinogenesis, distinct repair pathways have evolved. Despite this, complex DNA damage can cause severe problems and is believed to contribute to the biological consequences observed in cells exposed to genotoxic stress. In this review, the current knowledge of formation and repair of complex DNA damage is summarized and the risks and biological consequences associated with their repair are discussed.
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Affiliation(s)
- Karin Magnander
- Department of Oncology, Institute of Clinical Sciences, Sahlgrenska Academy at University of Gothenburg, Sahlgrenska University Hospital, Göteborg, Sweden.
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39
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40
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Ramsden DA. Polymerases in nonhomologous end joining: building a bridge over broken chromosomes. Antioxid Redox Signal 2011; 14:2509-19. [PMID: 20649463 PMCID: PMC3113452 DOI: 10.1089/ars.2010.3429] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Repair of double-strand breaks in chromosomal DNA is essential. Unfortunately, a paradigm central to most DNA repair pathways--damaged DNA is replaced by polymerases, by using an intact, undamaged complementary strand as a template--no longer works. The nonhomologous end joining (NHEJ) pathway nevertheless still uses DNA polymerases to help repair double-strand breaks. Bacteria use a member of the archaeo-eukaryal primase superfamily, whereas eukaryotes use multiple members of the polymerase X family. These polymerases can, depending on the biologic context, accurately replace break-associated damage, mitigate loss of flanking DNA, or diversify products of repair. Polymerases specifically implicated in NHEJ are uniquely effective in these roles: relative to canonic polymerases, NHEJ polymerases have been engineered to do more with less.
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Affiliation(s)
- Dale A Ramsden
- Department of Biochemistry and Biophysics, Lineberger Comprehensive Cancer Center, and Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, NC 27599, USA.
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41
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Sage E, Harrison L. Clustered DNA lesion repair in eukaryotes: relevance to mutagenesis and cell survival. Mutat Res 2011; 711:123-33. [PMID: 21185841 PMCID: PMC3101299 DOI: 10.1016/j.mrfmmm.2010.12.010] [Citation(s) in RCA: 167] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2010] [Revised: 12/10/2010] [Accepted: 12/17/2010] [Indexed: 12/28/2022]
Abstract
A clustered DNA lesion, also known as a multiply damaged site, is defined as ≥ 2 damages in the DNA within 1-2 helical turns. Only ionizing radiation and certain chemicals introduce DNA damage in the genome in this non-random way. What is now clear is that the lethality of a damaging agent is not just related to the types of DNA lesions introduced, but also to how the damage is distributed in the DNA. Clustered DNA lesions were first hypothesized to exist in the 1990s, and work has progressed where these complex lesions have been characterized and measured in irradiated as well as in non-irradiated cells. A clustered lesion can consist of single as well as double strand breaks, base damage and abasic sites, and the damages can be situated on the same strand or opposing strands. They include tandem lesions, double strand break (DSB) clusters and non-DSB clusters, and base excision repair as well as the DSB repair pathways can be required to remove these complex lesions. Due to the plethora of oxidative damage induced by ionizing radiation, and the repair proteins involved in their removal from the DNA, it has been necessary to study how repair systems handle these lesions using synthetic DNA damage. This review focuses on the repair process and mutagenic consequences of clustered lesions in yeast and mammalian cells. By examining the studies on synthetic clustered lesions, and the effects of low vs high LET radiation on mammalian cells or tissues, it is possible to extrapolate the potential biological relevance of these clustered lesions to the killing of tumor cells by radiotherapy and chemotherapy, and to the risk of cancer in non-tumor cells, and this will be discussed.
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Affiliation(s)
- Evelyne Sage
- Institut Curie, Bât. 110, Centre Universitaire, 91405 Orsay, France
- CNRS UMR3348, Bât. 110, Centre Universitaire, 91405 Orsay, France
| | - Lynn Harrison
- Department of Molecular and Cellular Physiology, LSUHSC-S, Shreveport, LA
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Abstract
Recent advances in radiotherapy have enabled the use of different types of particles, such as protons and heavy ions, as well as refinements to the treatment of tumours with standard sources (photons). However, the risk of second cancers arising in long-term survivors continues to be a problem. The long-term risks from treatments such as particle therapy have not yet been determined and are unlikely to become apparent for many years. Therefore, there is a need to develop risk assessments based on our current knowledge of radiation-induced carcinogenesis.
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Affiliation(s)
- Wayne D Newhauser
- MD Anderson Cancer Center Radiation Oncology, 1515 Holcombe Boulevard Houston, Texas 77030-4009, USA.
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43
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Datta K, Purkayastha S, Neumann RD, Pastwa E, Winters TA. Base damage immediately upstream from double-strand break ends is a more severe impediment to nonhomologous end joining than blocked 3'-termini. Radiat Res 2011; 175:97-112. [PMID: 21175352 PMCID: PMC3518376 DOI: 10.1667/rr2332.1] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Radiation-induced DNA double-strand breaks (DSBs) are critical cytotoxic lesions that are typically repaired by nonhomologous end joining (NHEJ) in human cells. Our previous work indicated that the highly cytotoxic DSBs formed by (125)I decay possess base damage clustered within 8 to 10 bases of the break and 3'-phosphate (P) and 3'-OH ends. This study examined the effect of such structures on NHEJ in in vitro assays employing either (125)I decay-induced DSB linearized plasmid DNA or structurally defined duplex oligonucleotides. Duplex oligonucleotides that possess either a 3'-P or 3'-phosphoglycolate (PG) or a ligatable 3'-OH end with either an AP site or an 8-oxo-dG 1 nucleotide upstream (-1n) from the 3'-terminus have been examined for reparability. Moderate to severe end-joining inhibition was observed for modified DSB ends or 8-oxo-dG upstream from a 3'-OH end. In contrast, abolition of end joining was observed with duplexes possessing an AP site upstream from a ligatable 3'-OH end or for a lesion combination involving 3'-P plus an upstream 8-oxo-dG. In addition, base mismatches at the -1n position were also strong inhibitors of NHEJ in this system, suggesting that destabilization of the DSB terminus as a result of base loss or improper base pairing may play a role in the inhibitory effects of these structures. Furthermore, we provide data indicating that DSB end joining is likely to occur prior to removal or repair of base lesions proximal to the DSB terminus. Our results show that base damage or base loss near a DSB end may be a severe block to NHEJ and that complex combinations of lesions presented in the context of a DSB may be more inhibitory than the individual lesions alone. In contrast, blocked DSB 3'-ends alone are only modestly inhibitory to NHEJ. Finally, DNA ligase activity is implicated as being responsible for these effects.
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Affiliation(s)
- Kamal Datta
- Nuclear Medicine Department, Warren Grant Magnuson Clinical Center, National Institutes of Health, Bethesda, MD 20892
| | - Shubhadeep Purkayastha
- Nuclear Medicine Department, Warren Grant Magnuson Clinical Center, National Institutes of Health, Bethesda, MD 20892
| | - Ronald D. Neumann
- Nuclear Medicine Department, Warren Grant Magnuson Clinical Center, National Institutes of Health, Bethesda, MD 20892
| | - Elzbieta Pastwa
- Department of Medicinal Chemistry, Medical University of Lodz, Lodz, Poland 92-215
| | - Thomas A. Winters
- Nuclear Medicine Department, Warren Grant Magnuson Clinical Center, National Institutes of Health, Bethesda, MD 20892
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Arczewska KD, Baumeier C, Kassahun H, Sengupta T, Bjørås M, Kuśmierek JT, Nilsen H. Caenorhabditis elegans NDX-4 is a MutT-type enzyme that contributes to genomic stability. DNA Repair (Amst) 2010; 10:176-87. [PMID: 21111690 DOI: 10.1016/j.dnarep.2010.10.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Revised: 10/04/2010] [Accepted: 10/22/2010] [Indexed: 12/11/2022]
Abstract
MutT enzymes prevent DNA damage by hydrolysis of 8-oxodGTP, an oxidized substrate for DNA synthesis and antimutagenic, anticarcinogenic, and antineurodegenerative functions of MutT enzymes are well established. MutT has been found in almost all kingdoms of life, including many bacterial species, yeasts, plants and mammals. However, a Caenorhabditis elegans MutT homologue was not previously identified. Here, we demonstrate that NDX-4 exhibits both hallmarks of a MutT-type enzyme with an ability to hydrolyze 8-oxodGTP and suppress the Escherichia coli mutT mutator phenotype. Moreover, we show that NDX-4 contributes to genomic stability in vivo in C. elegans. Phenotypic analyses of an ndx-4 mutant reveal that loss of NDX-4 leads to upregulation of key stress responsive genes that likely compensate for the in vivo role of NDX-4 in protection against deleterious consequences of oxidative stress. This discovery will enable us to use this extremely robust genetic model for further research into the contribution of oxidative DNA damage to phenotypes associated with oxidative stress.
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Eccles LJ, O'Neill P, Lomax ME. Delayed repair of radiation induced clustered DNA damage: friend or foe? Mutat Res 2010; 711:134-41. [PMID: 21130102 PMCID: PMC3112496 DOI: 10.1016/j.mrfmmm.2010.11.003] [Citation(s) in RCA: 178] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2010] [Revised: 11/18/2010] [Accepted: 11/25/2010] [Indexed: 12/27/2022]
Abstract
A signature of ionizing radiation exposure is the induction of DNA clustered damaged sites, defined as two or more lesions within one to two helical turns of DNA by passage of a single radiation track. Clustered damage is made up of double strand breaks (DSB) with associated base lesions or abasic (AP) sites, and non-DSB clusters comprised of base lesions, AP sites and single strand breaks. This review will concentrate on the experimental findings of the processing of non-DSB clustered damaged sites. It has been shown that non-DSB clustered damaged sites compromise the base excision repair pathway leading to the lifetime extension of the lesions within the cluster, compared to isolated lesions, thus the likelihood that the lesions persist to replication and induce mutation is increased. In addition certain non-DSB clustered damaged sites are processed within the cell to form additional DSB. The use of E. coli to demonstrate that clustering of DNA lesions is the major cause of the detrimental consequences of ionizing radiation is also discussed. The delayed repair of non-DSB clustered damaged sites in humans can be seen as a “friend”, leading to cell killing in tumour cells or as a “foe”, resulting in the formation of mutations and genetic instability in normal tissue.
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Affiliation(s)
- Laura J Eccles
- DNA Damage Group, Gray Institute for Radiation Oncology and Biology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK.
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Anderson JA, Harper JV, Cucinotta FA, O'Neill P. Participation of DNA-PKcs in DSB repair after exposure to high- and low-LET radiation. Radiat Res 2010; 174:195-205. [PMID: 20681786 DOI: 10.1667/rr2071.1] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Cellular lesions (e.g. DSBs) are induced into DNA upon exposure to radiation, with DSB complexity increasing with radiation ionization density. Using M059K and M059J human glioblastoma cells (proficient and deficient in DNA-PKcs activity, respectively), we investigated the repair of DNA damage, including DSBs, induced by high- and low-LET radiation [gamma rays, alpha particles and high-charge and energy (HZE) ions]. In the absence of DNA-PKcs activity, less DSB repair and increased recruitment of RAD51 was seen at 24 h. After exposure to (56)Fe heavy ions, the number of cells with RAD51 tracks was less than the number of cells with gamma-H2AX at 24 h with both cell lines. Using alpha particles, comparable numbers of cells with visible gamma-H2AX and RAD51 were seen at 24 h in both cell lines. M059J cells irradiated with alpha particles accumulated in S phase, with a greater number of cyclin A and RAD51 co-stained cells seen at 24 h compared with M059K cells, where an S-phase block is absent. It is proposed that DNA-PKcs plays a role in the repair of some frank DSBs, which are longer-lived in NHEJ-deficient cells, and some non-DSB clustered damage sites that are converted into DSBs at replication as the cell cycles through to S phase.
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Affiliation(s)
- Jennifer A Anderson
- DNA Damage Group, Gray Institute for Radiation Oncology and Biology, University of Oxford, Oxford, OX3 7DQ, United Kingdom
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Rai P. Oxidation in the nucleotide pool, the DNA damage response and cellular senescence: Defective bricks build a defective house. Mutat Res 2010; 703:71-81. [PMID: 20673809 DOI: 10.1016/j.mrgentox.2010.07.010] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2010] [Accepted: 07/19/2010] [Indexed: 12/20/2022]
Abstract
Activation of persistent DNA damage response (DDR) signaling is associated with the induction of a permanent proliferative arrest known as cellular senescence, a phenomenon intrinsically linked to both tissue aging as well as tumor suppression. The DNA damage observed in senescent cells has been attributed to elevated levels of reactive oxygen species (ROS), failing DNA damage repair processes, and/or oncogenic activation. It is not clear how labile molecules such as ROS are able to damage chromatin-bound DNA to a sufficient extent to invoke persistent DNA damage and DDR signaling. Recent evidence suggests that the nucleotide pool is a significant target for oxidants and that oxidized nucleotides, once incorporated into genomic DNA, can lead to the induction of a DNA strand break-associated DDR that triggers senescence in normal cells and in cells sustaining oncogene activation. Evasion of this DDR and resulting senescence is a key step in tumor progression. This review will explore the role of oxidation in the nucleotide pool as a major effector of oxidative stress-induced genotoxic damage and DDR in the context of cellular senescence and tumorigenic transformation.
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Affiliation(s)
- Priyamvada Rai
- Division of Gerontology and Geriatric Medicine, Department of Medicine, Rosenstiel Medical Sciences Building, Rm#7094/Locator Code: D-503, 1600 NW 10th Ave, Miller School of Medicine, University of Miami, Miami, FL 33136, United States.
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Malyarchuk S, Castore R, Harrison L. Apex1 can cleave complex clustered DNA lesions in cells. DNA Repair (Amst) 2009; 8:1343-54. [PMID: 19800300 DOI: 10.1016/j.dnarep.2009.08.008] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2009] [Revised: 08/28/2009] [Accepted: 08/31/2009] [Indexed: 01/10/2023]
Abstract
Current data indicate that clustered DNA damage generated by ionizing radiation contains 2-5 damages within 20 bps. The complexity of clustered damage is also believed to increase as the linear energy transfer of the radiation increases. Complex lesions are therefore biologically relevant especially with the use of carbon ion beam therapy to treat cancer. Since two closely opposed AP site analogs (furans) are converted to a double strand break (DSB) in cells, we hypothesized that breakage could be compromised by increasing the complexity of the cluster. We have examined the repair of clusters containing three and four lesions in mouse fibroblasts using a luciferase reporter plasmid. The addition of a third furan did reduce but not eliminate cleavage, while a tandem 8-oxo-7,8-dihydroguanine (8oxoG) immediately 5' to one furan in a two or three furan cluster decreased DSB formation by a small amount. In vitro studies using nuclear extracts demonstrated that the tandem 8oxoG was not removed under conditions where the furan was cleaved, but the presence of the 8oxoG reduced cleavage at the furan. Interestingly, a cluster of an 8oxoG opposite a furan did not form a DSB in cells. We have shown that Apex1 can cleave these complex clustered lesions in cells. This therefore indicates that Apex1 can generate complex DSBs from clustered lesions consisting of base damage and AP sites. Repair of these complex DSBs may be compromised by the nearby oxidative damage resulting in potentially lethal and biologically relevant damage.
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Affiliation(s)
- Svitlana Malyarchuk
- Department of Molecular and Cellular Physiology, Louisiana Health Sciences Center, 1501 Kings Highway, Shreveport, LA 71130, USA
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Silva JP, Gomes AC, Proença F, Coutinho OP. Novel nitrogen compounds enhance protection and repair of oxidative DNA damage in a neuronal cell model: Comparison with quercetin. Chem Biol Interact 2009; 181:328-37. [DOI: 10.1016/j.cbi.2009.07.024] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2009] [Revised: 07/29/2009] [Accepted: 07/29/2009] [Indexed: 11/24/2022]
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Abstract
PURPOSE This article seeks to illustrate some contributions of radiation chemistry to radiobiology and related science, and to draw attention to examples where radiation chemistry is central to our knowledge of specific aspects. Radiation chemistry is a mature branch of radiation science which is continually evolving and finding wider applications. This is particularly apparent in the study of the roles of free radicals in biology generally, and radiation biology specifically. The chemical viewpoint helps unite the spatial and temporal insight coming from radiation physics with the diversity of biological responses. While historically, the main application of radiation chemistry of relevance to radiation biology has been investigations of the free-radical processes leading to radiation-induced DNA damage and its chemical characterization, two features of radiation chemistry point to its wider importance. First, its emphasis on quantification and characterization at the molecular level helps provide links between DNA damage, biochemical repair processes, and mutagenicity and radiosensitivity. Second, its central pillar of chemical kinetics aids understanding of the roles of 'reactive oxygen species' in cell signalling and diverse biological effects more generally, and application of radiation chemistry in the development of drugs to enhance radiotherapy and as hypoxia-specific cytotoxins or diagnostic agents. The illustrations of the broader applications of radiation chemistry in this article focus on their relevance to radiation biology and demonstrate the importance of synergy in the radiation sciences. CONCLUSIONS The past contributions of radiation chemistry to radiation biology are evident, but there remains considerable potential to help advance future biological understanding using the knowledge and techniques of radiation chemistry.
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Affiliation(s)
- Peter O'Neill
- University of Oxford, Gray Institute for Radiation Oncology and Biology, Oxford, UK.
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