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Dasgupta S, Gao S, Yang H, Greenberg MM, Basu AK. 8-OxodGuo and Fapy•dG Mutagenicity in Escherichia coli Increases Significantly when They Are Part of a Tandem Lesion with 5-Formyl-2'-deoxyuridine. Chem Res Toxicol 2024; 37:1445-1452. [PMID: 39041427 PMCID: PMC11333159 DOI: 10.1021/acs.chemrestox.4c00231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/24/2024]
Abstract
Tandem lesions, which are defined by two or more contiguously damaged nucleotides, are a hallmark of ionizing radiation. Recently, tandem lesions containing 5-formyl-2'-deoxyuridine (5-fdU) flanked by a 5'-8-OxodGuo or Fapy•dG were discovered, and they are more mutagenic in human cells than the isolated lesions. In the current study, we examined replication of these tandem lesions in Escherichia coli. Bypass efficiency of both tandem lesions was reduced by 30-40% compared to the isolated lesions. Mutation frequencies (MFs) of isolated 8-OxodGuo and Fapy•dG were low, and no mutants were isolated from replication of a 5-fdU construct. The types of mutations from 8-OxodGuo were targeted G → T transversion, whereas Fapy•dG predominantly gave G → T and G deletion. 5'-8-OxodGuo-5-fdU also gave exclusively G → T mutation, which was 3-fold and 11-fold greater, without and with SOS induction, respectively, compared to that of an isolated 8-OxodGuo. In mutY/mutM cells, the MF of 8-OxodGuo and 5'-8-OxodGuo-5-fdU increased 13-fold and 7-fold, respectively. The MF of 5'-8-OxodGuo-5-fdU increased 2-fold and 3-fold in Pol II- and Pol IV-deficient cells, respectively, suggesting that these polymerases carry out largely error-free bypass. The MF of 5'- Fapy•dG-5-fdU was similar without (13 ± 1%) and with (16 ± 2%) SOS induction. Unlike the complex mutation spectrum reported earlier in human cells for 5'- Fapy•dG-5-fdU, with G → T as the major type of errors, in E. coli, the mutations were predominantly from deletion of 5-fdU. We postulate that removal of adenine-incorporated opposite 8-OxodGuo by Fpg and MutY repair proteins is partially impaired in the tandem 5'-8-OxodGuo-5-fdU, resulting in an increase in the G → T mutations, whereas a slippage mechanism may be operating in the 5'- Fapy•dG-5-fdU mutagenesis. This study showed that not only are these tandem lesions more mutagenic than the isolated lesions but they may also exhibit different types of mutations in different organisms.
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Affiliation(s)
- Srijana Dasgupta
- Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269, United States
| | - Shijun Gao
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Haozhe Yang
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Marc M Greenberg
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Ashis K Basu
- Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269, United States
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2
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Gao S, Tahara Y, Kool E, Greenberg M. Promoter dependent RNA polymerase II bypass of the epimerizable DNA lesion, Fapy•dG and 8-Oxo-2'-deoxyguanosine. Nucleic Acids Res 2024; 52:7437-7446. [PMID: 38908029 PMCID: PMC11260475 DOI: 10.1093/nar/gkae529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2024] [Revised: 05/30/2024] [Accepted: 06/10/2024] [Indexed: 06/24/2024] Open
Abstract
Formamidopyrimidine (Fapy•dG) is a major lesion arising from oxidation of dG that is produced from a common chemical precursor of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-OxodGuo). In human cells, replication of single-stranded shuttle vectors containing Fapy•dG is more mutagenic than 8-OxodGuo. Here, we present the first data regarding promoter dependent RNA polymerase II bypass of Fapy•dG. 8-OxodGuo bypass was examined side-by-side. Experiments were carried out using double-stranded shuttle vectors in HeLa cell nuclear lysates and in HEK 293T cells. The lesions do not significantly block transcriptional bypass efficiency. Less than 2% adenosine incorporation occurred in cells when the lesions were base paired with dC. Inhibiting base excision repair in HEK 293T cells significantly increased adenosine incorporation, particularly from Fapy•dG:dC bypass which yielded ∼25% adenosine incorporation. No effect was detected upon transcriptional bypass of either lesion in nucleotide excision repair deficient cells. Transcriptional mutagenesis was significantly higher when shuttle vectors containing dA opposite one of the lesions were employed. For Fapy•dG:dA bypass, adenosine incorporation was greater than 85%; whereas 8-OxodGuo:dA yielded >20% point mutations. The combination of more frequent replication mistakes and greater error-prone Pol II bypass suggest that Fapy•dG is more mutagenic than 8-OxodGuo.
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Affiliation(s)
- Shijun Gao
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Yuki Tahara
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
| | - Eric T Kool
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
| | - Marc M Greenberg
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, USA
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3
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Yudkina AV, Kim DV, Zharkov TD, Zharkov DO, Endutkin AV. Probing the Conformational Restraints of DNA Damage Recognition with β-L-Nucleotides. Int J Mol Sci 2024; 25:6006. [PMID: 38892193 PMCID: PMC11172447 DOI: 10.3390/ijms25116006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2024] [Revised: 05/28/2024] [Accepted: 05/28/2024] [Indexed: 06/21/2024] Open
Abstract
The DNA building blocks 2'-deoxynucleotides are enantiomeric, with their natural β-D-configuration dictated by the sugar moiety. Their synthetic β-L-enantiomers (βLdNs) can be used to obtain L-DNA, which, when fully substituted, is resistant to nucleases and is finding use in many biosensing and nanotechnology applications. However, much less is known about the enzymatic recognition and processing of individual βLdNs embedded in D-DNA. Here, we address the template properties of βLdNs for several DNA polymerases and the ability of base excision repair enzymes to remove these modifications from DNA. The Klenow fragment was fully blocked by βLdNs, whereas DNA polymerase κ bypassed them in an error-free manner. Phage RB69 DNA polymerase and DNA polymerase β treated βLdNs as non-instructive but the latter enzyme shifted towards error-free incorporation on a gapped DNA substrate. DNA glycosylases and AP endonucleases did not process βLdNs. DNA glycosylases sensitive to the base opposite their cognate lesions also did not recognize βLdNs as a correct pairing partner. Nevertheless, when placed in a reporter plasmid, pyrimidine βLdNs were resistant to repair in human cells, whereas purine βLdNs appear to be partly repaired. Overall, βLdNs are unique modifications that are mostly non-instructive but have dual non-instructive/instructive properties in special cases.
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Affiliation(s)
- Anna V. Yudkina
- Siberian Branch of the Russian Academy of Sciences Institute of Chemical Biology and Fundamental Medicine, 8 Lavrentieva Ave., 630090 Novosibirsk, Russia; (A.V.Y.); (D.V.K.); (T.D.Z.)
- Department of Natural Sciences, Novosibirsk State University, 2 Pirogova St., 630090 Novosibirsk, Russia
| | - Daria V. Kim
- Siberian Branch of the Russian Academy of Sciences Institute of Chemical Biology and Fundamental Medicine, 8 Lavrentieva Ave., 630090 Novosibirsk, Russia; (A.V.Y.); (D.V.K.); (T.D.Z.)
| | - Timofey D. Zharkov
- Siberian Branch of the Russian Academy of Sciences Institute of Chemical Biology and Fundamental Medicine, 8 Lavrentieva Ave., 630090 Novosibirsk, Russia; (A.V.Y.); (D.V.K.); (T.D.Z.)
| | - Dmitry O. Zharkov
- Siberian Branch of the Russian Academy of Sciences Institute of Chemical Biology and Fundamental Medicine, 8 Lavrentieva Ave., 630090 Novosibirsk, Russia; (A.V.Y.); (D.V.K.); (T.D.Z.)
- Department of Natural Sciences, Novosibirsk State University, 2 Pirogova St., 630090 Novosibirsk, Russia
| | - Anton V. Endutkin
- Siberian Branch of the Russian Academy of Sciences Institute of Chemical Biology and Fundamental Medicine, 8 Lavrentieva Ave., 630090 Novosibirsk, Russia; (A.V.Y.); (D.V.K.); (T.D.Z.)
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4
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Gao S, Oden P, Ryan B, Yang H, Freudenthal B, Greenberg M. Biochemical and structural characterization of Fapy•dG replication by Human DNA polymerase β. Nucleic Acids Res 2024; 52:5392-5405. [PMID: 38634780 PMCID: PMC11109955 DOI: 10.1093/nar/gkae277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Revised: 03/28/2024] [Accepted: 04/08/2024] [Indexed: 04/19/2024] Open
Abstract
N6-(2-deoxy-α,β-d-erythro-pentofuranosyl)-2,6-diamino-4-hydroxy-5-formamido-pyrimidine (Fapy•dG) is formed from a common intermediate and in comparable amounts to the well-studied mutagenic DNA lesion 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-OxodGuo). Fapy•dG preferentially gives rise to G → T transversions and G → A transitions. However, the molecular basis by which Fapy•dG is processed by DNA polymerases during this mutagenic process remains poorly understood. To address this we investigated how DNA polymerase β (Pol β), a model mammalian polymerase, bypasses a templating Fapy•dG, inserts Fapy•dGTP, and extends from Fapy•dG at the primer terminus. When Fapy•dG is present in the template, Pol β incorporates TMP less efficiently than either dCMP or dAMP. Kinetic analysis revealed that Fapy•dGTP is a poor substrate but is incorporated ∼3-times more efficiently opposite dA than dC. Extension from Fapy•dG at the 3'-terminus of a nascent primer is inefficient due to the primer terminus being poorly positioned for catalysis. Together these data indicate that mutagenic bypass of Fapy•dG is likely to be the source of the mutagenic effects of the lesion and not Fapy•dGTP. These experiments increase our understanding of the promutagenic effects of Fapy•dG.
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Affiliation(s)
- Shijun Gao
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218, USA
| | - Peyton N Oden
- Department of Biochemistry and Molecular Biology, and Department of Cancer Biology, University of Kansas Medical Center, KS City, KS 66160, USA
| | - Benjamin J Ryan
- Department of Biochemistry and Molecular Biology, and Department of Cancer Biology, University of Kansas Medical Center, KS City, KS 66160, USA
| | - Haozhe Yang
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218, USA
| | - Bret D Freudenthal
- Department of Biochemistry and Molecular Biology, and Department of Cancer Biology, University of Kansas Medical Center, KS City, KS 66160, USA
| | - Marc M Greenberg
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218, USA
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5
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Gao S, Hou P, Oh J, Wang D, Greenberg MM. Molecular Mechanism of RNA Polymerase II Transcriptional Mutagenesis by the Epimerizable DNA Lesion, Fapy·dG. J Am Chem Soc 2024; 146:6274-6282. [PMID: 38393762 PMCID: PMC10932878 DOI: 10.1021/jacs.3c14476] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/25/2024]
Abstract
Oxidative DNA lesions cause significant detrimental effects on a living species. Two major DNA lesions resulting from dG oxidation, 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-OxodGuo) and formamidopyrimidine (Fapy·dG), are produced from a common chemical intermediate. Fapy·dG is formed in comparable yields under oxygen-deficient conditions. Replicative bypass of Fapy·dG in human cells is more mutagenic than that of 8-OxodGuo. Despite the biological importance of transcriptional mutagenesis, there are no reports of the effects of Fapy·dG on RNA polymerase II (Pol II) activity. Here we perform comprehensive kinetic studies to investigate the impact of Fapy·dG on three key transcriptional fidelity checkpoint steps by Pol II: insertion, extension, and proofreading steps. The ratios of error-free versus error-prone incorporation opposite Fapy·dG are significantly reduced in comparison with undamaged dG. Similarly, Fapy·dG:A mispair is extended with comparable efficiency as that of the error-free, Fapy·dG:C base pair. The α- and β-configurational isomers of Fapy·dG have distinct effects on Pol II insertion and extension. Pol II can preferentially cleave error-prone products by proofreading. To further understand the structural basis of transcription processing of Fapy·dG, five different structures were solved, including Fapy·dG template-loading state (apo), error-free cytidine triphosphate (CTP) binding state (prechemistry), error-prone ATP binding state (prechemistry), error-free Fapy·dG:C product state (postchemistry), and error-prone Fapy·dG:A product state (postchemistry), revealing distinctive nucleotide binding and product states. Taken together, our study provides a comprehensive mechanistic framework for better understanding how Fapy·dG lesions impact transcription and subsequent pathological consequences.
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Affiliation(s)
- Shijun Gao
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, United States
| | - Peini Hou
- Division of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, California 92093, United States
| | - Juntaek Oh
- Division of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, California 92093, United States
- Department of Regulatory Science, Graduate School, Kyung Hee University, Seoul 02447, Republic of Korea
| | - Dong Wang
- Division of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, California 92093, United States
- Department of Cellular and Molecular Medicine, School of Medicine, University of California, San Diego, La Jolla, California 92093, United States
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, United States
| | - Marc M Greenberg
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, United States
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6
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Gao S, Oden PN, Ryan BJ, Yang H, Freudenthal BD, Greenberg MM. Biochemical and Structural Characterization of Fapy•dG Replication by Human DNA Polymerase β. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.15.575758. [PMID: 38293220 PMCID: PMC10827042 DOI: 10.1101/2024.01.15.575758] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2024]
Abstract
N6-(2-deoxy-α,β-D-erythro-pentofuranosyl)-2,6-diamino-4-hydroxy-5-formamido-pyrimidine (Fapy•dG) is formed from a common intermediate and in comparable amounts to the well-studied mutagenic DNA lesion 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-OxodGuo). Fapy•dG preferentially gives rise to G → T transversions and G → A transitions. However, the molecular basis by which Fapy•dG is processed by DNA polymerases during this mutagenic process remains poorly understood. To address this we investigated how DNA polymerase β (Pol β), a model mammalian polymerase, bypasses a templating Fapy•dG, inserts Fapy•dGTP, and extends from Fapy•dG at the primer terminus. When Fapy•dG is present in the template, Pol β incorporates TMP less efficiently than either dCMP or dAMP. Kinetic analysis revealed that Fapy•dGTP is a poor substrate but is incorporated ∼3-times more efficiently opposite dA than dC. Extension from Fapy•dG at the 3'-terminus of a nascent primer is inefficient due to the primer terminus being poorly positioned for catalysis. Together these data indicate that mutagenic bypass of Fapy•dG is likely to be the source of the mutagenic effects of the lesion and not Fapy•dGTP. These experiments increase our understanding of the promutagenic effects of Fapy•dG.
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7
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Masi A, Capobianco A, Bobrowski K, Peluso A, Chatgilialoglu C. Hydroxyl Radical vs. One-Electron Oxidation Reactivities in an Alternating GC Double-Stranded Oligonucleotide: A New Type Electron Hole Stabilization. Biomolecules 2023; 13:1493. [PMID: 37892175 PMCID: PMC10605094 DOI: 10.3390/biom13101493] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Revised: 09/30/2023] [Accepted: 10/04/2023] [Indexed: 10/29/2023] Open
Abstract
We examined the reaction of hydroxyl radicals (HO•) and sulfate radical anions (SO4•-), which is generated by ionizing radiation in aqueous solutions under anoxic conditions, with an alternating GC doubled-stranded oligodeoxynucleotide (ds-ODN), i.e., the palindromic 5'-d(GCGCGC)-3'. In particular, the optical spectra of the intermediate species and associated kinetic data in the range of ns to ms were obtained via pulse radiolysis. Computational studies by means of density functional theory (DFT) for structural and time-dependent DFT for spectroscopic features were performed on 5'-d(GCGC)-3'. Comprehensively, our results suggest the addition of HO• to the G:C pair moiety, affording the [8-HO-G:C]• detectable adduct. The previous reported spectra of one-electron oxidation of a variety of ds-ODN were assigned to [G(-H+):C]• after deprotonation. Regarding 5'-d(GCGCGC)-3' ds-ODN, the spectrum at 800 ns has a completely different spectral shape and kinetic behavior. By means of calculations, we assigned the species to [G:C/C:G]•+, in which the electron hole is predicted to be delocalized on the two stacked base pairs. This transient species was further hydrated to afford the [8-HO-G:C]• detectable adduct. These remarkable findings suggest that the double-stranded alternating GC sequences allow for a new type of electron hole stabilization via delocalization over the whole sequence or part of it.
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Affiliation(s)
- Annalisa Masi
- Istituto per la Sintesi Organica e la Fotoreattività, Consiglio Nazionale delle Ricerche, 40129 Bologna, Italy;
| | - Amedeo Capobianco
- Dipartimento di Chimica e Biologia “A. Zambelli”, Università di Salerno, 84084 Fisciano, Italy; (A.C.); (A.P.)
| | - Krzysztof Bobrowski
- Centre of Radiation Research and Technology, Institute of Nuclear Chemistry and Technology, 03-195 Warsaw, Poland;
| | - Andrea Peluso
- Dipartimento di Chimica e Biologia “A. Zambelli”, Università di Salerno, 84084 Fisciano, Italy; (A.C.); (A.P.)
| | - Chryssostomos Chatgilialoglu
- Istituto per la Sintesi Organica e la Fotoreattività, Consiglio Nazionale delle Ricerche, 40129 Bologna, Italy;
- Center for Advanced Technologies, Adam Mickiewicz University, 61-614 Poznań, Poland
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8
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Bacurio JHT, Gao S, Yang H, Basu AK, Greenberg MM. Synergistic effects on mutagenicity of tandem lesions containing 8-oxo-7,8-dihydro-2'-deoxyguanosine or Fapy•dG flanked by a 3' 5-formyl-2'-deoxyuridine in human cells. DNA Repair (Amst) 2023; 129:103527. [PMID: 37467631 PMCID: PMC10528826 DOI: 10.1016/j.dnarep.2023.103527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 05/10/2023] [Accepted: 06/18/2023] [Indexed: 07/21/2023]
Abstract
Modified nucleotides often hinder and/or decrease the fidelity of DNA polymerases. Tandem lesions, which are comprised of DNA modifications at two contiguous nucleotide positions, can be even more detrimental to genome stability. Recently, tandem lesions containing 5-formyl-2'-deoxyuridine (5fdU) flanked at the 5'-position by 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-OxodGuo) or N-(2-deoxy-α,β-D-erythropentofuranosyl)-N-(2,6-diamino-4-hydroxy-5-formamidopyrimidine (Fapy•dG) were discovered. We examined the replication of 5'- 8-OxodGuo-5fdU and 5'-Fapy•dG-5fdU tandem lesions in HEK 293T cells and several polymerase deficient variants by transfecting single-stranded vectors containing them. The local sequence of the tandem lesions encompasses the 273 codon of the p53 gene, a mutational hot-spot. The bypass efficiency and mutation spectra of the tandem lesions were compared to those of the isolated lesions. Replication of weakly mutagenic 5-fdU is little changed when part of the 5'- 8-OxodGuo-5fdU tandem lesion. G → T transversions attributable to 8-OxodGuo increase > 10-fold when the tandem lesion is bypassed. 5'-Fapy•dG-5fdU has a synergistic effect on the error-prone bypass of both lesions. The mutation frequency (MF) of 5'-Fapy•dG-5fdU increases 3-fold compared to isolated Fapy•dG. In addition, a 5'-adjacent Fapy•dG significantly increases the MF of 5fdU. The major mutation, G → T transversions, decrease by almost a third in hPol κ- cells, which is the opposite effect when isolated Fapy•dG in the same sequence context is replicated in HEK 293T cells in the same sequence. Steady-state kinetics indicate that hPol κ contributes to greater G → T transversions by decreasing the specificity constant for dCTP compared to an isolated Fapy•dG. The greater conformational freedom of Fapy•dG compared to 8-OxodGuo and its unusual ability to epimerize at the anomeric center is believed to be the source of the complex effects of 5'-Fapy•dG-5fdU on replication.
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Affiliation(s)
| | - Shijun Gao
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Haozhe Yang
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, USA; Department of Respiratory and Critical Care Medicine Targeted Tracer Research and Development Laboratory West China Hospital, Sichuan University, Chengdu, Sichuan 610041, PR China
| | - Ashis K Basu
- Department of Chemistry, University of Connecticut, Storrs, CT 06269, USA.
| | - Marc M Greenberg
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, USA.
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9
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Abstract
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Oxidation of a guanine nucleotide in DNA yields an 8-oxoguanine
nucleotide (oxoG) and is a mutagenic event in the genome.
Due to different arrangements of hydrogen-bond donors and acceptors, oxoG can affect the secondary structure of nucleic acids. We
have investigated base pairing preferences of oxoG in the
core of a tetrahelical G-quadruplex structure, adopted by analogues
of d(TG4T). Using spectroscopic methods, we have shown
that G-quartets can be fully substituted with oxoG nucleobases
to form an oxoG-quartet with a revamped hydrogen-bonding
scheme. While an oxoG-quartet can be incorporated into
the G-quadruplex core without distorting the phosphodiester backbone,
larger dimensions of the central cavity change the cation localization
and exchange properties.
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Affiliation(s)
- Simon Aleksič
- Slovenian NMR Centre, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia.,Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, 1000 Ljubljana, Slovenia
| | - Peter Podbevšek
- Slovenian NMR Centre, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia
| | - Janez Plavec
- Slovenian NMR Centre, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia.,Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, 1000 Ljubljana, Slovenia.,EN-FIST Centre of Excellence, Trg OF 13, 1000 Ljubljana, Slovenia
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10
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Polymorphic variant Asp239Tyr of human DNA glycosylase NTHL1 is inactive for removal of a variety of oxidatively-induced DNA base lesions from genomic DNA. DNA Repair (Amst) 2022; 117:103372. [PMID: 35870279 DOI: 10.1016/j.dnarep.2022.103372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 07/08/2022] [Accepted: 07/14/2022] [Indexed: 11/23/2022]
Abstract
Base excision repair is the major pathway for the repair of oxidatively-induced DNA damage, with DNA glycosylases removing modified bases in the first step. Human NTHL1 is specific for excision of several pyrimidine- and purine-derived lesions from DNA, with loss of function NTHL1 showing a predisposition to carcinogenesis. A rare single nucleotide polymorphism of the Nthl1 gene leading to the substitution of Asp239 with Tyr within the active site, occurs within global populations. In this work, we overexpressed and purified the variant NTHL1-Asp239Tyr (NTHL1-D239Y) and determined the substrate specificity of this variant relative to wild-type NTHL1 using gas chromatography-tandem mass spectrometry with isotope-dilution, and oxidatively-damaged genomic DNA containing multiple pyrimidine- and purine-derived lesions. Wild-type NTHL1 excised seven DNA base lesions with different efficiencies, whereas NTHL1-D239Y exhibited no glycosylase activity for any of these lesions. We also measured the activities of human glycosylases OGG1 and NEIL1, and E. coli glycosylases Nth and Fpg under identical experimental conditions. Different substrate specificities among these DNA glycosylases were observed. When mixed with NTHL1-D239Y, the activity of NTHL1 was not reduced, indicating no substrate binding competition. These results and the inactivity of the variant D239Y toward the major oxidatively-induced DNA lesions points to the importance of the understanding of this variant's role in carcinogenesis and the potential of individual susceptibility to cancer in individuals carrying this variant.
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