1
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Crisalli AM, Chen YT, Cai A, Li D, Cho BP. Conformation-dependent lesion bypass of bulky arylamine-dG adducts generated from 2-nitrofluorene in epigenetic sequence contexts. Nucleic Acids Res 2023; 51:12043-12053. [PMID: 37953358 PMCID: PMC10711442 DOI: 10.1093/nar/gkad1038] [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: 08/05/2023] [Revised: 09/27/2023] [Accepted: 10/24/2023] [Indexed: 11/14/2023] Open
Abstract
Sequence context influences structural characteristics and repair of DNA adducts, but there is limited information on how epigenetic modulation affects conformational heterogeneity and bypass of DNA lesions. Lesions derived from the environmental pollutant 2-nitrofluorene have been extensively studied as chemical carcinogenesis models; they adopt a sequence-dependent mix of two significant conformers: major groove binding (B) and base-displaced stacked (S). We report a conformation-dependent bypass of the N-(2'-deoxyguanosin-8-yl)-7-fluoro-2-aminofluorene (dG-FAF) lesion in epigenetic sequence contexts (d[5'-CTTCTC#G*NCCTCATTC-3'], where C# is C or 5-methylcytosine (5mC), G* is G or G-FAF, and N is A, T, C or G). FAF-modified sequences with a 3' flanking pyrimidine were better bypassed when the 5' base was 5mC, whereas sequences with a 3' purine exhibited the opposite effect. The conformational basis behind these variations differed; for -CG*C- and -CG*T-, bypass appeared to be inversely correlated with population of the duplex-destabilizing S conformer. On the other hand, the connection between conformation and a decrease in bypass for flanking purines in the 5mC sequences relative to C was more complex. It could be related to the emergence of a disruptive non-S/B conformation. The present work provides novel conformational insight into how 5mC influences the bypass efficiency of bulky DNA damage.
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Affiliation(s)
- Alicia M Crisalli
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, RI 02881, USA
| | - Yi-Tzai Chen
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, RI 02881, USA
| | - Ang Cai
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, RI 02881, USA
| | - Deyu Li
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, RI 02881, USA
| | - Bongsup P Cho
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, RI 02881, USA
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2
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Understanding the role of ancillary ligands in the interaction of Ru(II) complexes with covalent arylamine-DNA adducts. Inorganica Chim Acta 2022. [DOI: 10.1016/j.ica.2021.120681] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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3
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Dayanidhi PD, Vaidyanathan VG. Understanding the ancillary ligand effect on luminescent cyclometalated Ir(III) complex as a reporter for 2-acetylaminofluorene DNA(AAF-dG) adduct. J Biol Inorg Chem 2021; 27:189-199. [PMID: 34843001 DOI: 10.1007/s00775-021-01920-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 11/17/2021] [Indexed: 11/26/2022]
Abstract
Mutagenic agents such as aromatic amines undergo metabolic activation and produce DNA adducts at C8 position of guanine bases. N-2-acetylaminofluorene (AAF) generates different mutational outcomes when placed at G1, G2, and G3 of a NarI sequence (-G1G2CG3CC/T-). These outcomes are dictated by the conformations adopted by these adducts. Detection of such lesions is of considerable interest owing to their hazardous effects. Here, we report the synthesis of three cyclometalated [Ir(L)2dppz]+ complexes (L = 2-phenylpyridine (ppy) 1; benzo[h]quinoline (bhq) 2; 2-phenylquinoline (pq) 3; dppz = dipyrido[3,2-a:2',3'-c]phenazine) and their interaction with AAF adducted NarI DNA. Remarkably, complexes 1 and 2 displayed dominant 3LC transition characteristic of polar environment despite binding to the adducted sites. On the other hand, complex 3 binds to NarI sequences and behaves as a luminescent reporter for AAF-modified DNA. The results reported here emphasize that molecular light switching phenomenon can be stimulated by switching ancillary ligands and might act as potential probes for covalent-DNA defects.
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Affiliation(s)
- P David Dayanidhi
- Advanced Materials Laboratory, CSIR-Central Leather Research Institute, Adyar, Chennai, 600020, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India
| | - V G Vaidyanathan
- Advanced Materials Laboratory, CSIR-Central Leather Research Institute, Adyar, Chennai, 600020, India.
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India.
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4
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Manning TW, Van Riesen AJ, Manderville RA. Screening Internal Donor-Acceptor Biaryl Nucleobase Surrogates for Turn-On Fluorescence Affords an Aniline-Carboxythiophene Probe for Protein Detection by G-Quadruplex DNA. Bioconjug Chem 2021; 32:1791-1801. [PMID: 34138558 DOI: 10.1021/acs.bioconjchem.1c00270] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Donor-acceptor biaryls serve as microenvironment fluorescent sensors with highly quenched intramolecular charge transfer (ICT) emission in polar protic solvents that turns on in aprotic media. In DNA, canonical donor-acceptor fluorescent base analogs can be prepared through on-strand Suzuki-Miyaura cross-coupling reactions involving 8-bromo-2'-deoxyguanosine (8-Br-dG) with an acceptor aryboronic acid. Herein, we demonstrate that replacement of 8-Br-dG with N-methyl-4-bromoaniline (4-Br-An) containing an acyclic N-glycol group can be employed in the on-strand Suzuki-Miyaura reaction to afford new donor-acceptor biaryl nucleobase surrogates with a 40-fold increase in emission intensity for fluorescent readout within single-strand oligonucleotides. Screening the best acceptor for turn-on fluorescence upon duplex formation afforded the carboxythiophene derivative [COOTh]An with a 7.4-fold emission intensity increase upon formation of a single-bulged duplex (-1) with the surrogate occupying a pyrimidine-flanked bulge. Insertion of the [COOTh]An surrogate into the lateral TT loops produced by the antiparallel G-quadruplex (GQ) of the thrombin binding aptamer (TBA) afforded a 4.1-fold increase in probe fluorescence that was accompanied by a 20 nm wavelength shift to the blue upon thrombin binding. The modified TBA afforded a limit of detection of 129 nM for thrombin and displayed virtually no emission response to off-target proteins. The fluorescence response of [COOTh]An to thrombin binding highlights the utility of the thienyl-aniline moiety for monitoring DNA-protein interactions.
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Affiliation(s)
- Trevor W Manning
- Departments of Chemistry and Toxicology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Abigail J Van Riesen
- Departments of Chemistry and Toxicology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Richard A Manderville
- Departments of Chemistry and Toxicology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
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5
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Paul Elisa DD, Vaidyanathan Ganesan V. Switch-on effect on conformation-specific arylamine-DNA adduct by cyclometalated Ir(III) complexes. J Biol Inorg Chem 2020; 25:305-310. [PMID: 32052177 DOI: 10.1007/s00775-020-01762-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Accepted: 02/06/2020] [Indexed: 12/23/2022]
Abstract
Arylamines are known to form covalent-DNA adducts upon metabolic activation. These covalent adducts adopt different conformational attributes, viz., major groove (B), stacked (S), and minor groove (W), and lead to different types of mutations. The conformation depends on the flanking and next flanking bases at the 3' position of the adduct. Early detection of these conformations by simple probes is an ideal and challenging task. Here, we have reported two Ir(III)-based cyclometalated complexes, viz., [Ir(ppy)2(imiphen)]+ (1) (ppy: 2-phenylpyridine; imiphen: 2-(1H-imidazol-2-yl)-1H-imidazo[4,5-f][1,10]phenanthroline) and [Ir(ppy)2(furphen)]+ (2) (furphen: 2-(furan-2-yl)-1H-imidazo[4,5-f][1,10]phenanthroline) and its interaction with N-acetyl-2-aminofluorene-dG (AAF-dG). The sequences used in this work are NarI sequence (-CG1G2CG3CX-) in which Gs are modified with AAF and X is either C or T. Luminescence studies reveal that the Ir(III) complexes bind to AAF-dG adduct with high specificity toward G1 and G3 compared to G2 and unmodified control. The selectivity also depends on the next flanking base as cytosine favors G3AAF, while thymine favors G1AAF in complex 1 and vice versa for complex 2. The quenching studies confirm that Ir(III) complexes bind with AAF-dG sequences through the minor groove. The outcome of this work reveals that the switch-on effect by the complexes can be utilized for determining the conformational heterogeneity of the adduct and also for similar covalent-DNA adducts.
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Affiliation(s)
- David Dayanidhi Paul Elisa
- Advanced Materials Laboratory, CSIR-Central Leather Research Institute, Adyar, Chennai, 600 020, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India
| | - Vaidyanathan Vaidyanathan Ganesan
- Advanced Materials Laboratory, CSIR-Central Leather Research Institute, Adyar, Chennai, 600 020, India. .,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India.
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6
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Dayanidhi DPE, Thangavel N, Vaidyanathan Ganesan V. Selective Recognition of Conformation-Specific Arylamine–DNA Adduct in Frameshift Model by [Ru(phen)2(dppz)]2+. Chem Res Toxicol 2020; 33:800-805. [DOI: 10.1021/acs.chemrestox.9b00453] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- David Paul Elisa Dayanidhi
- Academy of Scientific and Innovative Research, Advanced Materials Laboratory, CSIR-Central Leather Research Institute, Adyar, Chennai 600 020, India
| | - Nandhini Thangavel
- Academy of Scientific and Innovative Research, Advanced Materials Laboratory, CSIR-Central Leather Research Institute, Adyar, Chennai 600 020, India
| | - Vaidyanathan Vaidyanathan Ganesan
- Academy of Scientific and Innovative Research, Advanced Materials Laboratory, CSIR-Central Leather Research Institute, Adyar, Chennai 600 020, India
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7
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Cai A, Bian K, Chen F, Tang Q, Carley R, Li D, Cho BP. Probing the Effect of Bulky Lesion-Induced Replication Fork Conformational Heterogeneity Using 4-Aminobiphenyl-Modified DNA. Molecules 2019; 24:molecules24081566. [PMID: 31009995 PMCID: PMC6514942 DOI: 10.3390/molecules24081566] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Revised: 04/14/2019] [Accepted: 04/17/2019] [Indexed: 11/16/2022] Open
Abstract
Bulky organic carcinogens are activated in vivo and subsequently react with nucleobases of cellular DNA to produce adducts. Some of these DNA adducts exist in multiple conformations that are slowly interconverted to one another. Different conformations have been implicated in different mutagenic and repair outcomes. However, studies on the conformation-specific inhibition of replication, which is more relevant to cell survival, are scarce, presumably due to the structural dynamics of DNA lesions at the replication fork. It is difficult to capture the exact nature of replication inhibition by existing end-point assays, which usually detect either the ensemble of consequences of all the conformers or the culmination of all cellular behaviors, such as mutagenicity or survival rate. We previously reported very unusual sequence-dependent conformational heterogeneities involving FABP-modified DNA under different sequence contexts (TG1*G2T [67%B:33%S] and TG1G2*T [100%B], G*, N-(2′-deoxyguanosin-8-yl)-4′-fluoro-4-aminobiphenyl) (Cai et al. Nucleic Acids Research, 46, 6356–6370 (2018)). In the present study, we attempted to correlate the in vitro inhibition of polymerase activity to different conformations from a single FABP-modified DNA lesion. We utilized a combination of surface plasmon resonance (SPR) and HPLC-based steady-state kinetics to reveal the differences in terms of binding affinity and inhibition with polymerase between these two conformers (67%B:33%S and 100%B).
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Affiliation(s)
- Ang Cai
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, 7 Greenhouse Road, Kingston, RI 02881, USA.
| | - Ke Bian
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, 7 Greenhouse Road, Kingston, RI 02881, USA.
| | - Fangyi Chen
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, 7 Greenhouse Road, Kingston, RI 02881, USA.
| | - Qi Tang
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, 7 Greenhouse Road, Kingston, RI 02881, USA.
| | - Rachel Carley
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, 7 Greenhouse Road, Kingston, RI 02881, USA.
| | - Deyu Li
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, 7 Greenhouse Road, Kingston, RI 02881, USA.
| | - Bongsup P Cho
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, 7 Greenhouse Road, Kingston, RI 02881, USA.
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8
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Thangavel N, Ganesan VV, Nair BU. Conformation Specific Binding of [Ru(phen)2
(dppz)]2+
with Mono- and Cluster Arylamine-DNA Adducts. ChemistrySelect 2018. [DOI: 10.1002/slct.201802172] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Nandhini Thangavel
- Inorganic and Physical Chemistry Laboratory; CSIR-Central Leather Research Institute, Adyar; Chennai 600 020 India
- Academy of Scientific and Innovative Research (AcSIR); CSIR-Central Leather Research Institute, Adyar; Chennai 600 020 India
| | - Vaidyanathan V. Ganesan
- Advanced Materials Laboratory; CSIR-Central Leather Research Institute, Adyar; Chennai 600 020 India
- Academy of Scientific and Innovative Research (AcSIR); CSIR-Central Leather Research Institute, Adyar; Chennai 600 020 India
| | - Balachandran U. Nair
- Inorganic and Physical Chemistry Laboratory; CSIR-Central Leather Research Institute, Adyar; Chennai 600 020 India
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9
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Berger FD, Sturla SJ, Kung RW, Montina T, Wetmore SD, Manderville RA. Conformational Preference and Fluorescence Response of a C-Linked C8-Biphenyl-Guanine Lesion in the NarI Mutational Hotspot: Evidence for Enhanced Syn Adduct Formation. Chem Res Toxicol 2017; 31:37-47. [DOI: 10.1021/acs.chemrestox.7b00266] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Florence D. Berger
- Department
of Health Sciences and Technology, Institute of Food, Nutrition, and
Health, ETH Zürich, 8092 Zürich, Switzerland
| | - Shana J. Sturla
- Department
of Health Sciences and Technology, Institute of Food, Nutrition, and
Health, ETH Zürich, 8092 Zürich, Switzerland
| | - Ryan W. Kung
- Department
of Chemistry and Biochemistry, and the Canadian Centre for Research
in Advanced Fluorine Technologies, University of Lethbridge, Lethbridge, Alberta T1K 3M4, Canada
| | - Tony Montina
- Department
of Chemistry and Biochemistry, and the Canadian Centre for Research
in Advanced Fluorine Technologies, University of Lethbridge, Lethbridge, Alberta T1K 3M4, Canada
| | - Stacey D. Wetmore
- Department
of Chemistry and Biochemistry, and the Canadian Centre for Research
in Advanced Fluorine Technologies, University of Lethbridge, Lethbridge, Alberta T1K 3M4, Canada
| | - Richard A. Manderville
- Departments
of Chemistry and Toxicology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
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10
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Kathuria P, Sharma P, Manderville RA, Wetmore SD. Molecular Modeling of the Major DNA Adduct Formed from Food Mutagen Ochratoxin A in NarI Two-Base Deletion Duplexes: Impact of Sequence Context and Adduct Ionization on Conformational Preference and Mutagenicity. Chem Res Toxicol 2017; 30:1582-1591. [PMID: 28719194 DOI: 10.1021/acs.chemrestox.7b00103] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Exposure to ochratoxin A (OTA), a possible human carcinogen, leads to many different DNA mutations. As a first step toward understanding the structural basis of OTA-induced mutagenicity, the present work uses a robust computational approach and a slipped mutagenic intermediate model previously studied for C8-dG aromatic amine adducts to analyze the conformational features of postreplication two-base deletion DNA duplexes containing OT-dG, the major OTA lesion at the C8 position of guanine. Specifically, a total of 960 ns of molecular dynamics simulations (excluding trial simulations) were carried out on four OT-dG ionization states in three sequence contexts within oligomers containing the NarI recognition sequence, a known hotspot for deletion mutations induced by related adducts formed from known carcinogens. Our results indicate that the structural properties and relative stability of the competing "major groove" and "stacked" conformations of OTA adducted two-base deletion duplexes depend on both the OTA ionization state and the sequence context, mainly due to conformation-dependent deviations in discrete local (hydrogen-bonding and stacking) interactions at the lesion site, as well as DNA bending. When the structural characteristics of the OT-dG adducted two-base deletion duplexes are compared to those associated with previously studied C8-dG adducts, a greater understanding of the effects of the nucleobase-carcinogen linkage, and size of the carcinogenic moiety on the conformational preferences of damaged DNA is obtained. Most importantly, our work predicts key structural features for OT-dG-adducted deletion DNA duplexes, which in turn allow us to develop hypotheses regarding OT-dG replication outcomes. Thus, our computational results are valuable for the design and interpretation of future biochemical studies on the potentially carcinogenic OT-dG lesion.
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Affiliation(s)
- Preetleen Kathuria
- Department of Chemistry and Centre for Advanced Studies in Chemistry, Panjab University , Chandigarh 160014, India
| | - Purshotam Sharma
- Department of Chemistry and Centre for Advanced Studies in Chemistry, Panjab University , Chandigarh 160014, India
| | - Richard A Manderville
- Departments of Chemistry and Toxicology, University of Guelph , Guelph, Ontario N1G 2W1, Canada
| | - Stacey D Wetmore
- Department of Chemistry and Biochemistry, University of Lethbridge , Lethbridge, Alberta T1K 3M4, Canada
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11
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Nandhini T, Vaidyanathan V, Nair B. Effect of conformation of the arylamine-DNA adduct on the sensitivity of [Ru(phen)2(dppz)]2+ complex. INORG CHEM COMMUN 2016. [DOI: 10.1016/j.inoche.2016.09.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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12
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Wang X, Yang P, Li J, Ihsan A, Liu Q, Cheng G, Tao Y, Liu Z, Yuan Z. Genotoxic risk of quinocetone and its possible mechanism in in vitro studies. Toxicol Res (Camb) 2016; 5:446-460. [PMID: 30090359 PMCID: PMC6062406 DOI: 10.1039/c5tx00341e] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Accepted: 11/18/2015] [Indexed: 12/14/2022] Open
Abstract
Quinoxalines possessing the quinoxaline-1,4-dioxide (QdNOs) basic structure are used for their antibacterial action, although their mechanism of genotoxicity is not clear. After comparing the sensitivity of V79 cells and HepG2 cells to quinocetone (QCT) and other QdNOs, it was found that HepG2 cells are more sensitive. The results show that QCT induces the generation of O2˙- and OH˙ during metabolism. Free radicals could then attack guanine and induce 8-hydroxy-deoxyguanine (8-OHdG) generation, causing DNA strand breakage, the inhibition of topoisomerase II (topo II) activity, and alter PCNA, Gadd45 and topo II gene expression. QCT also caused mutations in the mtDNA genes COX1, COX3 and ATP6, which might affect the function of the mitochondrial respiratory chain and increase the production of reactive oxygen species (ROS). Nuclear extracts from HepG2 cells treated with QCT had markedly reduced topo II activity, as judged by the inability to convert pBR322 DNA from the catenated to the decatenated form by producing stable DNA-topo II complexes. This study suggests that QCT electrostatically bound to DNA in a groove, affecting the dissociation of topo II from DNA and impacting DNA replication. Taken together, these data reveal that DNA damage induced by QCT resulted from O2˙- and OH˙ generated in the metabolism process. This data throws new light onto the genotoxicity of quinoxalines.
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Affiliation(s)
- Xu Wang
- National Reference Laboratory of Veterinary Drug Residues (HZAU) and MOA Key Laboratory for Detection of Veterinary Drug Residues , Wuhan , Hubei 430070 , China . ; ; Tel: +86-27-87287186
| | - Panpan Yang
- MOA Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products , Huazhong Agricultural University , Wuhan , Hubei 430070 , China
| | - Juan Li
- MOA Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products , Huazhong Agricultural University , Wuhan , Hubei 430070 , China
| | - Awais Ihsan
- Department of Biosciences , COMSATS Institute of Information Technology , Sahiwal , Pakistan
| | - Qianying Liu
- MOA Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products , Huazhong Agricultural University , Wuhan , Hubei 430070 , China
| | - Guyue Cheng
- MOA Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products , Huazhong Agricultural University , Wuhan , Hubei 430070 , China
| | - Yanfei Tao
- Hubei Collaborative Innovation Center for Animal Nutrition and Feed Safety , Wuhan , Hubei , China
| | - Zhengli Liu
- Hubei Collaborative Innovation Center for Animal Nutrition and Feed Safety , Wuhan , Hubei , China
| | - Zonghui Yuan
- National Reference Laboratory of Veterinary Drug Residues (HZAU) and MOA Key Laboratory for Detection of Veterinary Drug Residues , Wuhan , Hubei 430070 , China . ; ; Tel: +86-27-87287186
- MOA Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products , Huazhong Agricultural University , Wuhan , Hubei 430070 , China
- Hubei Collaborative Innovation Center for Animal Nutrition and Feed Safety , Wuhan , Hubei , China
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13
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Toxicology of DNA Adducts Formed Upon Human Exposure to Carcinogens. ADVANCES IN MOLECULAR TOXICOLOGY 2016. [DOI: 10.1016/b978-0-12-804700-2.00007-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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14
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Sproviero M, Verwey AMR, Witham AA, Manderville RA, Sharma P, Wetmore SD. Enhancing Bulge Stabilization through Linear Extension of C8-Aryl-Guanine Adducts to Promote Polymerase Blockage or Strand Realignment to Produce a C:C Mismatch. Chem Res Toxicol 2015. [PMID: 26225720 DOI: 10.1021/acs.chemrestox.5b00233] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Aryl radicals can react at the C8-site of 2'-deoxyguanosine (dG) to produce DNA adducts with a C8-C linkage (denoted C-linked). Such adducts are structurally distinct from those possessing a flexible amine (N-linked) or ether (O-linked) linkage, which separates the C8-aryl moiety from the guanine nucleobase. In the current study, two model C-linked C8-dG adducts, namely, C8-benzo[b]thienyl-dG ([BTh]G) and C8-(pyren-1-yl)-dG ([Py]G), were incorporated into the NarI (12mer, NarI(12) and 22mer, NarI(22)) hotspot sequence for frameshift mutations in bacteria. For the first time, C-linked C8-dG adducts are shown to stabilize the -2 deletion duplex within the NarI sequence. Primer-elongation assays employing Sulfolobus solfataricus P2 DNA polymerase IV (Dpo4) demonstrates the influence of C8-aryl ring size and shape in promoting Dpo4 blockage or strand realignment to produce a C:C mismatch downstream of the adduct site. Molecular dynamics simulations of the -2 deletion duplex suggest that both anti and syn adduct structures are energetically accessible. These findings provide a rationale for describing the biochemical outcome induced by C-linked C8-dG adducts when processed by Dpo4.
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Affiliation(s)
- Michael Sproviero
- †Department of Chemistry and Toxicology, University of Guelph, Guelph, ON Canada N1G 2W1
| | - Anne M R Verwey
- †Department of Chemistry and Toxicology, University of Guelph, Guelph, ON Canada N1G 2W1
| | - Aaron A Witham
- †Department of Chemistry and Toxicology, University of Guelph, Guelph, ON Canada N1G 2W1
| | - Richard A Manderville
- †Department of Chemistry and Toxicology, University of Guelph, Guelph, ON Canada N1G 2W1
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15
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Witham AA, Verwey AMR, Sproviero M, Manderville RA, Sharma P, Wetmore SD. Chlorine functionalization of a model phenolic C8-guanine adduct increases conformational rigidity and blocks extension by a Y-family DNA polymerase. Chem Res Toxicol 2015; 28:1346-56. [PMID: 26004422 DOI: 10.1021/acs.chemrestox.5b00143] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Certain phenoxyl radicals can attach covalently to the C8-site of 2'-deoxyguanosine (dG) to afford oxygen-linked C8-dG adducts. Such O-linked adducts can be chemically synthesized through a nucleophilic displacement reaction between a phenolate and a suitably protected 8-Br-dG derivative. This permits the generation of model O-linked C8-dG adducts on scales suitable for insertion into oligonucleotide substrates using solid-phase DNA synthesis. Variation of the C8-aryl moiety provides an opportunity to derive structure-activity relationships on adduct conformation in duplex DNA and replication bypass by DNA polymerases. In the current study, the influence of chlorine C8-dG functionalization on in vitro DNA replication by Klenow fragment exo(-) (Kf(-)) and the Y-family polymerase (Sulfolobus solfataricus P2 DNA polymerase IV (Dpo4)) has been determined. Model O-linked C8-dG adducts derived from the pentachlorophenoxyl radical ([PCP]G) and 2,4,6-trichlorophenoxyl radical ([TCP]G) were inserted into the reiterated G3-position of the NarI sequence (12-mer, NarI(12); and 22-mer, NarI(22)), which is a known hotspot for frameshift mutations mediated by N-linked polycyclic C8-dG adducts in bacterial mutagenesis. Within the NarI(12) duplex, the unsubstituted C8-phenoxy-dG ([PhO]G) adduct adopts a minimally perturbed B-form helix. Chlorination of [PhO]G to afford [PCP]G does not significantly change the adduct conformation within the NarI(12) duplex, as predicted by molecular dynamics simulations. However, when using NarI(22) for DNA synthesis in vitro, the chlorinated [PCP]G and [TCP]G lesions significantly block DNA replication by Kf(-) and Dpo4, whereas [PhO]G is readily bypassed. These findings highlight the impact that chlorine substituents impart to bulky C8-dG lesions.
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Affiliation(s)
- Aaron A Witham
- †Departments of Chemistry and Toxicology, University of Guelph, Guelph, ON, Canada N1G 2W1
| | - Anne M R Verwey
- †Departments of Chemistry and Toxicology, University of Guelph, Guelph, ON, Canada N1G 2W1
| | - Michael Sproviero
- †Departments of Chemistry and Toxicology, University of Guelph, Guelph, ON, Canada N1G 2W1
| | - Richard A Manderville
- †Departments of Chemistry and Toxicology, University of Guelph, Guelph, ON, Canada N1G 2W1
| | - Purshotam Sharma
- ‡Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, Canada T1K 3M4
| | - Stacey D Wetmore
- ‡Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, Canada T1K 3M4
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16
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Sharma P, Majdi Yazdi M, Merriman A, Manderville RA, Wetmore SD. Influence of the Linkage Type and Functional Groups in the Carcinogenic Moiety on the Conformational Preferences of Damaged DNA: Structural and Energetic Characterization of Carbon- and Oxygen-Linked C8-Phenolic-Guanine Adducts. Chem Res Toxicol 2015; 28:782-96. [DOI: 10.1021/tx500527p] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- Purshotam Sharma
- Department
of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, Canada T1K 3M4
| | - Mohadeseh Majdi Yazdi
- Department
of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, Canada T1K 3M4
| | - Ashlyn Merriman
- Department
of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, Canada T1K 3M4
| | - Richard A. Manderville
- Departments
of Chemistry and Toxicology, University of Guelph, Guelph, Ontario, Canada N1G2W1
| | - Stacey D. Wetmore
- Department
of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, Canada T1K 3M4
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17
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Sproviero M, Verwey AMR, Rankin KM, Witham AA, Soldatov DV, Manderville RA, Fekry MI, Sturla SJ, Sharma P, Wetmore SD. Structural and biochemical impact of C8-aryl-guanine adducts within the NarI recognition DNA sequence: influence of aryl ring size on targeted and semi-targeted mutagenicity. Nucleic Acids Res 2014; 42:13405-21. [PMID: 25361967 PMCID: PMC4245952 DOI: 10.1093/nar/gku1093] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Chemical mutagens with an aromatic ring system may be enzymatically transformed to afford aryl radical species that preferentially react at the C8-site of 2′-deoxyguanosine (dG). The resulting carbon-linked C8-aryl-dG adduct possesses altered biophysical and genetic coding properties compared to the precursor nucleoside. Described herein are structural and in vitro mutagenicity studies of a series of fluorescent C8-aryl-dG analogues that differ in aryl ring size and are representative of authentic DNA adducts. These structural mimics have been inserted into a hotspot sequence for frameshift mutations, namely, the reiterated G3-position of the NarI sequence within 12mer (NarI(12)) and 22mer (NarI(22)) oligonucleotides. In the NarI(12) duplexes, the C8-aryl-dG adducts display a preference for adopting an anti-conformation opposite C, despite the strong syn preference of the free nucleoside. Using the NarI(22) sequence as a template for DNA synthesis in vitro, mutagenicity of the C8-aryl-dG adducts was assayed with representative high-fidelity replicative versus lesion bypass Y-family DNA polymerases, namely, Escherichia coli pol I Klenow fragment exo− (Kf−) and Sulfolobus solfataricus P2 DNA polymerase IV (Dpo4). Our experiments provide a basis for a model involving a two-base slippage and subsequent realignment process to relate the miscoding properties of C-linked C8-aryl-dG adducts with their chemical structures.
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Affiliation(s)
- Michael Sproviero
- Department of Chemistry and Toxicology, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
| | - Anne M R Verwey
- Department of Chemistry and Toxicology, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
| | - Katherine M Rankin
- Department of Chemistry and Toxicology, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
| | - Aaron A Witham
- Department of Chemistry and Toxicology, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
| | - Dmitriy V Soldatov
- Department of Chemistry and Toxicology, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
| | - Richard A Manderville
- Department of Chemistry and Toxicology, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
| | - Mostafa I Fekry
- Department of Health Sciences and Technology, Institute of Food, Nutrition and Health, ETH Zürich, 8032 Zürich, Switzerland Pharmacognosy Department, Faculty of Pharmacy, Cairo University, Kasr El-Aini, Cairo 11562, Egypt
| | - Shana J Sturla
- Department of Health Sciences and Technology, Institute of Food, Nutrition and Health, ETH Zürich, 8032 Zürich, Switzerland
| | - Purshotam Sharma
- Department of Chemistry & Biochemistry, University of Lethbridge, Lethbridge, AB, Canada, T1K 3M4
| | - Stacey D Wetmore
- Department of Chemistry and Toxicology, University of Guelph, Guelph, Ontario, Canada, N1G 2W1 Department of Health Sciences and Technology, Institute of Food, Nutrition and Health, ETH Zürich, 8032 Zürich, Switzerland Pharmacognosy Department, Faculty of Pharmacy, Cairo University, Kasr El-Aini, Cairo 11562, Egypt Department of Chemistry & Biochemistry, University of Lethbridge, Lethbridge, AB, Canada, T1K 3M4
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18
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Xu L, Vaidyanathan VG, Cho BP. Real-time surface plasmon resonance study of biomolecular interactions between polymerase and bulky mutagenic DNA lesions. Chem Res Toxicol 2014; 27:1796-807. [PMID: 25195494 PMCID: PMC4203393 DOI: 10.1021/tx500252z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
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Surface plasmon resonance (SPR) was
used to measure polymerase-binding
interactions of the bulky mutagenic DNA lesions N-(2′-deoxyguanosin-8-yl)-4′-fluoro-4-aminobiphenyl
(FABP) or N-(2′-deoxyguanosin-8-yl)-7-fluoro-2-acetylaminofluorene
(FAAF) in the context of two unique 5′-flanking bases (CG*A and TG*A). The enzymes used
were exo-nuclease-deficient Klenow fragment (Kf-exo–) or polymerase β (pol β). Specific binary and ternary
DNA binding affinities of the enzymes were characterized at subnanomolar
concentrations. The SPR results showed that Kf-exo– binds strongly to a double strand/single strand template/primer
junction, whereas pol β binds preferentially to double-stranded
DNA having a one-nucleotide gap. Both enzymes exhibited tight binding
to native DNA, with high nucleotide selectivity, where the KD values for each base pair increased in the
order dCTP ≪ dTTP ∼ dATP ≪ dGTP. In contrast
to that for pol β, Kf-exo– binds tightly to
lesion-modified templates; however, both polymerases exhibited minimal
nucleotide selectivity toward adducted DNA. Primer steady-state kinetics
and 19F NMR results support the SPR data. The relative
insertion efficiency fins of dCTP opposite
FABP was significantly higher in the TG*A sequence
compared to that in CG*A. Although Kf-exo– was not sensitive to the presence of a DNA lesion,
FAAF-induced conformational heterogeneity perturbed the active site
of pol β, weakening the enzyme’s ability to bind to FAAF
adducts compared to FABP adducts. The present study demonstrates the
effectiveness of SPR for elucidating how lesion-induced conformational
heterogeneity affects the binding capability of polymerases and ultimately
the nucleotide insertion efficiency.
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Affiliation(s)
- Lifang Xu
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island , Kingston, Rhode Island 02881, United States
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19
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Sharma P, Manderville RA, Wetmore SD. Structural and energetic characterization of the major DNA adduct formed from the food mutagen ochratoxin A in the NarI hotspot sequence: influence of adduct ionization on the conformational preferences and implications for the NER propensity. Nucleic Acids Res 2014; 42:11831-45. [PMID: 25217592 PMCID: PMC4191402 DOI: 10.1093/nar/gku821] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The nephrotoxic food mutagen ochratoxin A (OTA) produces DNA adducts in rat kidneys, the major lesion being the C8-linked-2′-deoxyguanosine adduct (OTB-dG). Although research on other adducts stresses the importance of understanding the structure of the associated adducted DNA, site-specific incorporation of OTB-dG into DNA has yet to be attempted. The present work uses a robust computational approach to determine the conformational preferences of OTB-dG in three ionization states at three guanine positions in the NarI recognition sequence opposite cytosine. Representative adducted DNA helices were derived from over 2160 ns of simulation and ranked via free energies. For the first time, a close energetic separation between three distinct conformations is highlighted, which indicates OTA-adducted DNA likely adopts a mixture of conformations regardless of the sequence context. Nevertheless, the preferred conformation depends on the flanking bases and ionization state due to deviations in discrete local interactions at the lesion site. The structural characteristics of the lesion thus discerned have profound implications regarding its repair propensity and mutagenic outcomes, and support recent experiments suggesting the induction of double-strand breaks and deletion mutations upon OTA exposure. This combined structural and energetic characterization of the OTB-dG lesion in DNA will encourage future biochemical experiments on this potentially genotoxic lesion.
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Affiliation(s)
- Purshotam Sharma
- Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, T1K 3M4, Canada
| | - Richard A Manderville
- Department of Chemistry and Toxicology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
| | - Stacey D Wetmore
- Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, T1K 3M4, Canada
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20
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Wilson KA, Wetmore SD. Complex Conformational Heterogeneity of the Highly Flexible O6-Benzyl-guanine DNA Adduct. Chem Res Toxicol 2014; 27:1310-25. [PMID: 24941023 DOI: 10.1021/tx500178x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Katie A. Wilson
- Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive West, Lethbridge, Alberta, Canada T1K 3M4
| | - Stacey D. Wetmore
- Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive West, Lethbridge, Alberta, Canada T1K 3M4
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21
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Jain V, Vaidyanathan VG, Patnaik S, Gopal S, Cho BP. Conformational insights into the lesion and sequence effects for arylamine-induced translesion DNA synthesis: 19F NMR, surface plasmon resonance, and primer kinetic studies. Biochemistry 2014; 53:4059-71. [PMID: 24915610 PMCID: PMC4075988 DOI: 10.1021/bi5003212] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
![]()
Adduct-induced DNA damage can affect
transcription efficiency and
DNA replication and repair. We previously investigated the effects
of the 3′-next flanking base (G*CT vs G*CA; G*, FABP, N-(2′-deoxyguanosin-8-yl)-4′-fluoro-4-aminobiphenyl;
FAF, N-(2′-deoxyguanosin-8-yl)-7-fluoro-2-aminofluorene)
on the conformation of arylamine-DNA lesions in relation to E. coli nucleotide excision repair (JainV., HiltonB., LinB., PatnaikS., LiangF., DarianE., ZouY., MackerellA. D.Jr., and ChoB. P. (2013) Nucleic Acids Res., 41, 869−88023180767). Here,
we report the differential effects of the same pair of sequences on
DNA replication in vitro by the polymerases exofree
Klenow fragment (Kf-exo–) and Dpo4. We obtained
dynamic 19F NMR spectra for two 19-mer modified templates
during primer elongation: G*CA [d(5′-CTTACCATCG*CAACCATTC-3′)]
and G*CT [d(5′-CTTACCATCG*CTACCATTC-3′)].
We found that lesion stacking is favored in the G*CT sequence compared to the G*CA counterpart. Surface
plasmon resonance binding results showed consistently weaker affinities
for the modified DNA with the binding strength in the order of FABP
> FAF and G*CA > G*CT. Primer extension was stalled at
(n) and near (n – 1 and n + 1) the lesion site, and the extent of blockage and the extension
rates across the lesion were influenced by not only the DNA sequences
but also the nature of the adduct’s chemical structure (FAF
vs FABP) and the polymerase employed (Kf-exo– vs
Dpo4). Steady-state kinetics analysis with Kf-exo– revealed the most dramatic sequence and lesion effects at the lesion
(n) and postinsertion (n + 1) sites,
respectively. Taken together, these results provide insights into
the important role of lesion-induced conformational heterogeneity
in modulating translesion DNA synthesis.
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Affiliation(s)
- Vipin Jain
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island , Kingston, Rhode Island 02881, United States
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22
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Jain V, Hilton B, Lin B, Jain A, MacKerell AD, Zou Y, Cho BP. Structural and thermodynamic insight into Escherichia coli UvrABC-mediated incision of cluster diacetylaminofluorene adducts on the NarI sequence. Chem Res Toxicol 2013; 26:1251-62. [PMID: 23841451 DOI: 10.1021/tx400186v] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Cluster DNA damage refers to two or more lesions in a single turn of the DNA helix. Such clustering may occur with bulky DNA lesions, which may be responsible for their sequence-dependent repair and mutational outcomes. Here we prepared three 16-mer cluster duplexes in which two fluoroacetylaminofluorene adducts (dG-FAAF) are separated by zero, one, and two nucleotides in the Escherichia coli NarI mutational hot spot (5'-CTCTCG1G2CG3CCATCAC-3'): 5'-CG1*G2*CG3CC-3', 5'-CG1G2*CG3*CC-3', and 5'-CG1*G2CG3*CC-3' (G* = dG-FAAF), respectively. We conducted spectroscopic, thermodynamic, and molecular dynamics studies of these di-FAAF duplexes, and the results were compared with those of the corresponding mono-FAAF adducts in the same NarI sequence [Jain, V., et al. (2012) Nucleic Acids Res. 40, 3939-3951]. Our nucleotide excision repair results showed the diadducts were more reparable than the corresponding monoadducts. Moreover, we observed dramatic flanking base sequence effects on their repair efficiency in the following order: NarI-G2G3 > NarI-G1G3 > NarI-G1G2. The nuclear magnetic resonance, circular dichroism, ultraviolet melting, and molecular dynamics simulation results revealed that in contrast to the monoadducts, diadducts produced a synergistic effect on duplex destabilization. In addition, dG-FAAF at G2G3 and G1G3 destacks the neighboring bases, with greater destabilization occurring with the former. Overall, the results indicate the importance of base stacking and related thermal and thermodynamic destabilization in the repair of bulky cluster arylamine DNA adducts.
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Affiliation(s)
- Vipin Jain
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, Rhode Island 02881, USA
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23
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Cai Y, Zheng H, Ding S, Kropachev K, Schwaid AG, Tang Y, Mu H, Wang S, Geacintov NE, Zhang Y, Broyde S. Free energy profiles of base flipping in intercalative polycyclic aromatic hydrocarbon-damaged DNA duplexes: energetic and structural relationships to nucleotide excision repair susceptibility. Chem Res Toxicol 2013; 26:1115-25. [PMID: 23758590 DOI: 10.1021/tx400156a] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The crystal structure of Rad4/Rad23, the yeast homolog of the human nucleotide excision repair (NER) lesion recognition factor XPC-RAD23B ( Min , J. H. and Pavletich , N. P. ( 2007 ) Nature 449 , 570 - 575 ) reveals that the lesion-partner base is flipped out of the helix and binds to amino acids of the protein. This suggests the hypothesis that the flipping of this partner base must overcome a free energy barrier, which constitutes one element contributing to changes in the thermodynamic properties induced by the DNA damage and sensed by the recognition protein. We explored this hypothesis by computing complete flipping free energy profiles for two lesions derived from the procarcinogenic polycyclic aromatic hydrocarbons (PAHs), dibenzo[a,l]pyrene (DB[a,l]P) and benzo[a]pyrene (B[a]P), R-trans-anti-DB[a,l]P-N(6)-dA (R-DB[a,l]P-dA) and R-trans-anti-B[a]P-N(6)-dA (R-B[a]P-dA), and the corresponding unmodified duplex. The DB[a,l]P and B[a]P adducts differ in number and organization of their aromatic rings. We integrate these results with prior profiles for the R-trans-anti-DB[a,l]P-dG adduct ( Zheng , H. et al. ( 2010 ) Chem. Res. Toxicol. 23 , 1868 - 1870 ). All adopt conformational themes involving intercalation of the PAH aromatic ring system into the DNA duplex; however, R-DB[a,l]P-dA and R-B[a]P-dA intercalate from the major groove, while R-DB[a,l]P-dG intercalates from the minor groove. These structural differences produce different computed van der Waals stacking interaction energies between the flipping partner base with the lesion aromatic ring system and adjacent bases; we find that the better the stacking, the higher the relative flipping free energy barrier and hence lower flipping probability. The better relative NER susceptibilities correlate with greater ease of flipping in these three differently intercalated lesions. In addition to partner base flipping, the Rad4/Rad23 crystal structure shows that a protein-β-hairpin, BHD3, intrudes from the major groove side between the DNA strands at the lesion site. We present a molecular modeling study for the R-DB[a,l]P-dG lesion in Rad4/Rad23 showing BHD3 β-hairpin intrusion with lesion eviction, and we hypothesize that lesion steric effects play a role in the recognition of intercalated adducts.
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Affiliation(s)
- Yuqin Cai
- Department of Biology, New York University , New York, New York 10003, United States
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24
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Vaidyanathan VG, Liang F, Beard WA, Shock DD, Wilson SH, Cho BP. Insights into the conformation of aminofluorene-deoxyguanine adduct in a DNA polymerase active site. J Biol Chem 2013; 288:23573-85. [PMID: 23798703 DOI: 10.1074/jbc.m113.476150] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The active site conformation of the mutagenic fluoroaminofluorene-deoxyguanine adduct (dG-FAF, N-(2'-deoxyguanosin-8-yl)-7-fluoro-2-aminofluorene) has been investigated in the presence of Klenow fragment of Escherichia coli DNA polymerase I (Kfexo(-)) and DNA polymerase β (pol β) using (19)F NMR, insertion assay, and surface plasmon resonance. In a single nucleotide gap, the dG-FAF adduct adopts both a major-groove- oriented and base-displaced stacked conformation, and this heterogeneity is retained upon binding pol β. The addition of a non-hydrolysable 2'-deoxycytosine-5'-[(α,β)-methyleno]triphosphate (dCMPcPP) nucleotide analog to the binary complex results in an increase of the major groove conformation of the adduct at the expense of the stacked conformation. Similar results were obtained with the addition of an incorrect dAMPcPP analog but with formation of the minor groove binding conformer. In contrast, dG-FAF adduct at the replication fork for the Kfexo(-) complex adopts a mix of the major and minor groove conformers with minimal effect upon the addition of non-hydrolysable nucleotides. For pol β, the insertion of dCTP was preferred opposite the dG-FAF adduct in a single nucleotide gap assay consistent with (19)F NMR data. Surface plasmon resonance binding kinetics revealed that pol β binds tightly with DNA in the presence of correct dCTP, but the adduct weakens binding with no nucleotide specificity. These results provide molecular insights into the DNA binding characteristics of FAF in the active site of DNA polymerases and the role of DNA structure and sequence on its coding potential.
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Affiliation(s)
- Vaidyanathan G Vaidyanathan
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, Rhode Island 02881, USA
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25
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Sandineni A, Lin B, MacKerell AD, Cho BP. Structure and thermodynamic insights on acetylaminofluorene-modified deletion DNA duplexes as models for frameshift mutagenesis. Chem Res Toxicol 2013; 26:937-51. [PMID: 23688347 DOI: 10.1021/tx400116n] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
2-Acetylaminofluorene (AAF) is a prototype arylamine carcinogen that forms C8-substituted dG-AAF and dG-AF as the major DNA lesions. The bulky N-acetylated dG-AAF lesion can induce various frameshift mutations depending on the base sequence around the lesion. We hypothesized that the thermodynamic stability of bulged-out slipped mutagenic intermediates (SMIs) is directly related to deletion mutations. The objective of the present study was to probe the structural/conformational basis of various dG-AAF-induced SMIs formed during translesion synthesis. We performed spectroscopic, thermodynamic, and molecular dynamics studies of several AAF-modified 16-mer model DNA duplexes, including fully paired and -1, -2, and -3 deletion duplexes of the 5'-CTCTCGATG[FAAF]CCATCAC-3' sequence and an additional -1 deletion duplex of the 5'-CTCTCGGCG[FAAF]CCATCAC-3' NarI sequence. Modified deletion duplexes existed in a mixture of external B and stacked S conformers, with the population of the S conformer being 'GC'-1 (73%) > 'AT'-1 (72%) > full (60%) > -2 (55%) > -3 (37%). Thermodynamic stability was in the order of -1 deletion > -2 deletion > fully paired > -3 deletion duplexes. These results indicate that the stacked S-type conformer of SMIs is thermodynamically more stable than the conformationally flexible external B conformer. Results from the molecular dynamics simulations indicate that perturbation of base stacking dominates the relative stability along with contributions from bending, duplex dynamics, and solvation effects that are important in specific cases. Taken together, these results support a hypothesis that the conformational and thermodynamic stabilities of the SMIs are critical determinants for the induction of frameshift mutations.
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Affiliation(s)
- Anusha Sandineni
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, Rhode Island 02881, USA
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26
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Tang Y, Liu Z, Ding S, Lin CH, Cai Y, Rodriguez FA, Sayer JM, Jerina DM, Amin S, Broyde S, Geacintov NE. Nuclear magnetic resonance solution structure of an N(2)-guanine DNA adduct derived from the potent tumorigen dibenzo[a,l]pyrene: intercalation from the minor groove with ruptured Watson-Crick base pairing. Biochemistry 2012; 51:9751-62. [PMID: 23121427 DOI: 10.1021/bi3013577] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The most potent tumorigen identified among the polycyclic aromatic hydrocarbons (PAH) is the nonplanar fjord region dibenzo[a,l]pyrene (DB[a,l]P). It is metabolically activated in vivo through the widely studied diol epoxide (DE) pathway to form covalent adducts with DNA bases, predominantly guanine and adenine. The (+)-11S,12R,13R,14S DE enantiomer forms adducts via its C14 position with the exocyclic amino group of guanine. Here, we present the first nuclear magnetic resonance solution structure of a DB[a,l]P-derived adduct, the 14R-(+)-trans-anti-DB[a,l]P-N(2)-dG (DB[a,l]P-dG) lesion in double-stranded DNA. In contrast to the stereochemically identical benzo[a]pyrene-derived N(2)-dG adduct (B[a]P-dG) in which the B[a]P rings reside in the B-DNA minor groove on the 3'-side of the modifed deoxyguanosine, in the DB[a,l]P-derived adduct the DB[a,l]P rings intercalate into the duplex on the 3'-side of the modified base from the sterically crowded minor groove. Watson-Crick base pairing of the modified guanine with the partner cytosine is broken, but these bases retain some stacking with the bulky DB[a,l]P ring system. This new theme in PAH DE-DNA adduct conformation differs from (1) the classical intercalation motif in which Watson-Crick base pairing is intact at the lesion site and (2) the base-displaced intercalation motif in which the damaged base and its partner are extruded from the helix. The structural considerations that lead to the intercalated conformation of the DB[a,l]P-dG lesion in contrast to the minor groove alignment of the B[a]P-dG adduct, and the implications of the DB[a,l]P-dG conformational motif for the recognition of such DNA lesions by the human nucleotide excision repair apparatus, are discussed.
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Affiliation(s)
- Yijin Tang
- Department of Chemistry, New York University, New York, NY 10003, USA
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C8-linked bulky guanosine DNA adducts: experimental and computational insights into adduct conformational preferences and resulting mutagenicity. Future Med Chem 2012; 4:1981-2007. [PMID: 23088278 DOI: 10.4155/fmc.12.138] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Bulky DNA adducts are formed through the covalent attachment of aryl groups to the DNA nucleobases. Many of these adducts are known to possess conformational heterogeneity, which is responsible for the variety of mutagenic outcomes associated with these lesions. The present contribution reviews several conformational and mutagenic themes that are prevalent among the DNA adducts formed at the C8-site of the guanine nucleobase. The most important conclusions obtained (to date) from experiments are summarized including the anti/syn conformational preference of the adducts, their potential to inflict DNA mutations and mismatch stabilization, and their interactions with DNA polymerases and repair enzymes. Additionally, the unique role that computer calculations can play in understanding the structural properties of these adducts are highlighted.
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28
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Lior-Hoffmann L, Wang L, Wang S, Geacintov NE, Broyde S, Zhang Y. Preferred WMSA catalytic mechanism of the nucleotidyl transfer reaction in human DNA polymerase κ elucidates error-free bypass of a bulky DNA lesion. Nucleic Acids Res 2012; 40:9193-205. [PMID: 22772988 PMCID: PMC3467051 DOI: 10.1093/nar/gks653] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Revised: 06/07/2012] [Accepted: 06/12/2012] [Indexed: 01/13/2023] Open
Abstract
Human DNA Pol κ is a polymerase enzyme, specialized for near error-free bypass of certain bulky chemical lesions to DNA that are derived from environmental carcinogens present in tobacco smoke, automobile exhaust and cooked food. By employing ab initio QM/MM-MD (Quantum Mechanics/Molecular Mechanics-Molecular Dynamics) simulations with umbrella sampling, we have determined the entire free energy profile of the nucleotidyl transfer reaction catalyzed by Pol κ and provided detailed mechanistic insights. Our results show that a variant of the Water Mediated and Substrate Assisted (WMSA) mechanism that we previously deduced for Dpo4 and T7 DNA polymerases is preferred for Pol κ as well, suggesting its broad applicability. The hydrogen on the 3'-OH primer terminus is transferred through crystal and solvent waters to the γ-phosphate of the dNTP, followed by the associative nucleotidyl transfer reaction; this is facilitated by a proton transfer from the γ-phosphate to the α,β-bridging oxygen as pyrophosphate leaves, to neutralize the evolving negative charge. MD simulations show that the near error-free incorporation of dCTP opposite the major benzo[a]pyrene-derived dG lesion is compatible with the WMSA mechanism, allowing for an essentially undisturbed pentacovalent phosphorane transition state, and explaining the bypass of this lesion with little mutation by Pol κ.
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Affiliation(s)
- Lee Lior-Hoffmann
- Department of Chemistry and Department of Biology, New York University, NY 10003, USA
| | - Lihua Wang
- Department of Chemistry and Department of Biology, New York University, NY 10003, USA
| | - Shenglong Wang
- Department of Chemistry and Department of Biology, New York University, NY 10003, USA
| | - Nicholas E. Geacintov
- Department of Chemistry and Department of Biology, New York University, NY 10003, USA
| | - Suse Broyde
- Department of Chemistry and Department of Biology, New York University, NY 10003, USA
| | - Yingkai Zhang
- Department of Chemistry and Department of Biology, New York University, NY 10003, USA
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29
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Mu H, Kropachev K, Wang L, Zhang L, Kolbanovskiy A, Kolbanovskiy M, Geacintov NE, Broyde S. Nucleotide excision repair of 2-acetylaminofluorene- and 2-aminofluorene-(C8)-guanine adducts: molecular dynamics simulations elucidate how lesion structure and base sequence context impact repair efficiencies. Nucleic Acids Res 2012; 40:9675-90. [PMID: 22904073 PMCID: PMC3479214 DOI: 10.1093/nar/gks788] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Nucleotide excision repair (NER) efficiencies of DNA lesions can vary by orders of magnitude, for reasons that remain unclear. An example is the pair of N-(2′-deoxyguanosin-8-yl)-2-aminofluorene (dG-C8-AF) and N-(2′-deoxyguanosin-8-yl)-2-acetylaminofluorene (dG-C8-AAF) adducts that differ by a single acetyl group. The NER efficiencies in human HeLa cell extracts of these lesions are significantly different when placed at G1, G2 or G3 in the duplex sequence (5′-CTCG1G2CG3CCATC-3′) containing the NarI mutational hot spot. Furthermore, the dG-C8-AAF adduct is a better substrate of NER than dG-C8-AF in all three NarI sequence contexts. The conformations of each of these adducts were investigated by Molecular dynamics (MD) simulation methods. In the base-displaced conformational family, the greater repair susceptibility of dG-C8-AAF in all sequences stems from steric hindrance effects of the acetyl group which significantly diminish the adduct-base stabilizing van der Waals stacking interactions relative to the dG-C8-AF case. Base sequence context effects for each adduct are caused by differences in helix untwisting and minor groove opening that are derived from the differences in stacking patterns. Overall, the greater NER efficiencies are correlated with greater extents of base sequence-dependent local untwisting and minor groove opening together with weaker stacking interactions.
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Affiliation(s)
- Hong Mu
- Department of Biology, New York University, 100 Washington Square East, New York, NY 10003, USA
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30
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Vaidyanathan VG, Cho BP. Sequence Effects on Translesion Synthesis of an Aminofluorene–DNA Adduct: Conformational, Thermodynamic, and Primer Extension Kinetic Studies. Biochemistry 2012; 51:1983-95. [DOI: 10.1021/bi2017443] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- V. G. Vaidyanathan
- Department of Biomedical and Pharmaceutical
Sciences, College of Pharmacy, University of Rhode Island, Kingston, Rhode Island 02881, United States
| | - Bongsup P. Cho
- Department of Biomedical and Pharmaceutical
Sciences, College of Pharmacy, University of Rhode Island, Kingston, Rhode Island 02881, United States
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31
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Jain V, Hilton B, Patnaik S, Zou Y, Chiarelli MP, Cho BP. Conformational and thermodynamic properties modulate the nucleotide excision repair of 2-aminofluorene and 2-acetylaminofluorene dG adducts in the NarI sequence. Nucleic Acids Res 2012; 40:3939-51. [PMID: 22241773 PMCID: PMC3351159 DOI: 10.1093/nar/gkr1307] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Nucleotide excision repair (NER) is a major repair pathway that recognizes and corrects various lesions in cellular DNA. We hypothesize that damage recognition is an initial step in NER that senses conformational anomalies in the DNA caused by lesions. We prepared three DNA duplexes containing the carcinogen adduct N-(2'-deoxyguanosin-8-yl)-7-fluoro-2-acetylaminofluorene (FAAF) at G(1), G(2) or G(3) of NarI sequence (5'-CCG(1)G(2)CG(3)CC-3'). Our (19)F-NMR/ICD results showed that FAAF at G(1) and G(3) prefer syn S- and W-conformers, whereas anti B-conformer was predominant for G(2). We found that the repair of FAAF occurs in a conformation-specific manner, i.e. the highly S/W-conformeric G(3) and -G(1) duplexes incised more efficiently than the B-type G(2) duplex (G(3)∼G(1)> G(2)). The melting and thermodynamic data indicate that the S- and W-conformers produce greater DNA distortion and thermodynamic destabilization. The N-deacetylated N-(2'-deoxyguanosin-8-yl)-7-fluoro-2-aminofluorene (FAF) adducts in the same NarI sequence are repaired 2- to 3-fold less than FAAF: however, the incision efficiency was in order of G(2)∼G(1)> G(3), a reverse trend of the FAAF case. We have envisioned the so-called N-acetyl factor as it could raise conformational barriers of FAAF versus FAF. The present results provide valuable conformational insight into the sequence-dependent UvrABC incisions of the bulky aminofluorene DNA adducts.
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Affiliation(s)
- Vipin Jain
- Department of Biomedical and Pharmaceutical Sciences, University of Rhode Island, Kingston, RI 02881, USA
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32
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33
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Millen AL, Kamenz BL, Leavens FMV, Manderville RA, Wetmore SD. Conformational flexibility of C8-phenoxylguanine adducts in deoxydinucleoside monophosphates. J Phys Chem B 2011; 115:12993-3002. [PMID: 21942470 DOI: 10.1021/jp2057332] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
M06-2X/6-31G(d,p) is used to calculate the structure of all natural deoxydinucleoside monophosphates with G in the 5' or 3' position, the anti or syn conformation, and each natural (A, C, G, T) base in the corresponding flanking position. When the ortho or para C8-phenoxyl-2'-deoxyguanosine (C8-phenoxyl-dG) adduct replaces G in each model, there is little change in the relative base-base orientation or backbone conformation. However, the orientation of the C8-phenoxyl group can be characterized according to the position (5' versus 3'), conformation (anti versus syn), and isomer (ortho versus para) of damage. Although the degree of coplanarity between the phenoxyl ring and G base in the ortho adduct is highly affected by the sequence since the hydroxyl group can interact with neighboring bases, the para adduct generally does not exhibit discrete interactions with flanking bases. For both adducts, steric clashes between the phenoxyl group and the backbone or flanking base destabilize the anti conformation preferred by the natural nucleotide and thereby result in a clear preference for the syn conformation regardless of the sequence or position. This contrasts the conclusions drawn from smaller (nucleoside, nucleotide) models previously used in the literature, which stresses the importance of using models that address the steric constraints present due to the surrounding environment. Since replication errors for other C8-dG bulky adducts have been linked to a preference for the syn conformation, our findings provide insight into the possible mutagenicity of phenolic adducts.
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Affiliation(s)
- Andrea L Millen
- Department of Chemistry, University of Lethbridge, Lethbridge, Alberta, Canada
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34
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Stone MP, Huang H, Brown KL, Shanmugam G. Chemistry and structural biology of DNA damage and biological consequences. Chem Biodivers 2011; 8:1571-615. [PMID: 21922653 PMCID: PMC3714022 DOI: 10.1002/cbdv.201100033] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The formation of adducts by the reaction of chemicals with DNA is a critical step for the initiation of carcinogenesis. The structural analysis of various DNA adducts reveals that conformational and chemical rearrangements and interconversions are a common theme. Conformational changes are modulated both by the nature of adduct and the base sequences neighboring the lesion sites. Equilibria between conformational states may modulate both DNA repair and error-prone replication past these adducts. Likewise, chemical rearrangements of initially formed DNA adducts are also modulated both by the nature of adducts and the base sequences neighboring the lesion sites. In this review, we focus on DNA damage caused by a number of environmental and endogenous agents, and biological consequences.
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Affiliation(s)
- Michael P Stone
- Department of Chemistry, Center in Molecular Toxicology, Vanderbilt-Ingram Cancer Center, Vanderbilt University, Nashville, TN 37235, USA.
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35
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Turesky RJ, Le Marchand L. Metabolism and biomarkers of heterocyclic aromatic amines in molecular epidemiology studies: lessons learned from aromatic amines. Chem Res Toxicol 2011; 24:1169-214. [PMID: 21688801 PMCID: PMC3156293 DOI: 10.1021/tx200135s] [Citation(s) in RCA: 217] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Aromatic amines and heterocyclic aromatic amines (HAAs) are structurally related classes of carcinogens that are formed during the combustion of tobacco or during the high-temperature cooking of meats. Both classes of procarcinogens undergo metabolic activation by N-hydroxylation of the exocyclic amine group to produce a common proposed intermediate, the arylnitrenium ion, which is the critical metabolite implicated in toxicity and DNA damage. However, the biochemistry and chemical properties of these compounds are distinct, and different biomarkers of aromatic amines and HAAs have been developed for human biomonitoring studies. Hemoglobin adducts have been extensively used as biomarkers to monitor occupational and environmental exposures to a number of aromatic amines; however, HAAs do not form hemoglobin adducts at appreciable levels, and other biomarkers have been sought. A number of epidemiologic studies that have investigated dietary consumption of well-done meat in relation to various tumor sites reported a positive association between cancer risk and well-done meat consumption, although some studies have shown no associations between well-done meat and cancer risk. A major limiting factor in most epidemiological studies is the uncertainty in quantitative estimates of chronic exposure to HAAs, and thus, the association of HAAs formed in cooked meat and cancer risk has been difficult to establish. There is a critical need to establish long-term biomarkers of HAAs that can be implemented in molecular epidemioIogy studies. In this review, we highlight and contrast the biochemistry of several prototypical carcinogenic aromatic amines and HAAs to which humans are chronically exposed. The biochemical properties and the impact of polymorphisms of the major xenobiotic-metabolizing enzymes on the biological effects of these chemicals are examined. Lastly, the analytical approaches that have been successfully employed to biomonitor aromatic amines and HAAs, and emerging biomarkers of HAAs that may be implemented in molecular epidemiology studies are discussed.
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Affiliation(s)
- Robert J Turesky
- Division of Environmental Health Sciences, Wadsworth Center , Albany, New York 12201, United States.
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36
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Liang F, Cho BP. Conformational and thermodynamic impact of bulky aminofluorene adduction on simulated translesion DNA synthesis. Chem Res Toxicol 2011; 24:597-605. [PMID: 21410284 DOI: 10.1021/tx2000587] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We report a systematic spectroscopic investigation on the conformational evolution during primer extension of a bulky fluoroaminofluorene-modified dG adduct (FAF-dG) in chemically simulated translesion synthesis. FAF-dG was paired either with dC or dA (dC-match and dA-mismatch series, respectively). Dynamic (19)F NMR/CD results showed that the FAF-adduct exists in a syn/anti equilibrium and that its conformational characteristics are modulated by the identity of an inserted nucleotide at the lesion site and the extent of primer elongation. At the pre-insertion site, the adduct adopted preferentially a syn conformation where FAF stacked with preceding bases. Insertion of the correct nucleotide dC at the lesion site and subsequent elongation resulted in a gradual transition to the anti conformation. By contrast, the syn conformer was persistent along with primer extension in the dA-mismatch series. In the dC-match series, FAF-induced thermal (T(m)) and thermodynamic (-ΔG°(37 °C)) stabilities were significantly reduced relative to those of the controls. However, the corresponding T(m) and -ΔG°(37 °C) values were increased in the FAF-modified mismatched dA series. The lesion impact persisted up to three 5'-nucleotides from the lesion. Occupation of the minor groove of the W-conformer with the bulky carcinogenic fluorene moiety not only would limit the DNA mobility but also would impose a serious difficulty for the active site of a polymerase throughout the replication process. Our spectroscopic results are consistent with reported data on AF, which showed dramatic (~10(4)-fold) differences in the nucleotide insertion rates between the dC-match and dA-mismatch series. The results emphasize the importance of adduct-induced steric constraints for determining the replication fidelity of a polymerase.
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Affiliation(s)
- Fengting Liang
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, RI 02881, United States
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37
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Millen AL, Churchill CDM, Manderville RA, Wetmore SD. Effect of Watson−Crick and Hoogsteen Base Pairing on the Conformational Stability of C8-Phenoxyl-2′-deoxyguanosine Adducts. J Phys Chem B 2010; 114:12995-3004. [DOI: 10.1021/jp105817p] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Andrea L. Millen
- Department of Chemistry, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta, Canada, T1K 3M4, and Department of Chemistry, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
| | - Cassandra D. M. Churchill
- Department of Chemistry, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta, Canada, T1K 3M4, and Department of Chemistry, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
| | - Richard A. Manderville
- Department of Chemistry, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta, Canada, T1K 3M4, and Department of Chemistry, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
| | - Stacey D. Wetmore
- Department of Chemistry, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta, Canada, T1K 3M4, and Department of Chemistry, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
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38
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Liang F, Cho BP. Enthalpy-entropy contribution to carcinogen-induced DNA conformational heterogeneity. Biochemistry 2010; 49:259-66. [PMID: 19961237 DOI: 10.1021/bi901629p] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
DNA damage by adduct formation is a critical step for the initiation of carcinogenesis. Aromatic amines are strong inducers of environmental carcinogenesis. Their DNA adducts are known to exist in an equilibrium between the major groove (B) and base-displaced stacked (S) conformations. However, the factors governing such heterogeneity remain unclear. Here we conducted extensive calorimetry/NMR/CD studies on the model DNA lesions caused by fluorinated 2-aminfluorene (FAF) and 4-aminobiphenyl (FABP) in order to gain thermodynamic and kinetic insights into the S/B conformational equilibrium. We demonstrate that there are large differences in enthalpy-entropy compensations for FABP and FAF. The small and flexible FABP exclusively adopts the less perturbed B conformer with small enthalpy (DeltaDeltaH-2.7 kcal/mol)/entropy (DeltaDeltaS-0.7 eu) change. In contrast, FAF stacks better and exists as a mixture of B and S conformers with large enthalpy (DeltaDeltaH-13.4 kcal/mol)/entropy (DeltaDeltaS-34.2 eu) compensation. van't Hoff analysis of dynamic (19)F NMR data indicated DeltaH(B<-->S) = 4.1 kcal/mol in favor of the B conformer and DeltaS(B<-->S) = 15.6 cal mol(-1) K(-1) in favor of the intercalated S conformer. These findings demonstrate that the favorable entropy of the S conformer over B conformer determines the S/B population ratios at physiological temperatures.
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Affiliation(s)
- Fengting Liang
- Department of Biomedical and Pharmaceutical Sciences, University of Rhode Island, Kingston, Rhode Island 02881, USA
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39
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Donny-Clark K, Shapiro R, Broyde S. Accommodation of an N-(deoxyguanosin-8-yl)-2-acetylaminofluorene adduct in the active site of human DNA polymerase iota: Hoogsteen or Watson-Crick base pairing? Biochemistry 2009; 48:7-18. [PMID: 19072536 DOI: 10.1021/bi801283d] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Bypass across DNA lesions by specialized polymerases is essential for maintenance of genomic stability. Human DNA polymerase iota (poliota) is a bypass polymerase of the Y family. Crystal structures of poliota suggest that Hoogsteen base pairing is employed to bypass minor groove DNA lesions, placing them on the spacious major groove side of the enzyme. Primer extension studies have shown that poliota is also capable of error-free nucleotide incorporation opposite the bulky major groove adduct N-(deoxyguanosin-8-yl)-2-acetylaminofluorene (dG-AAF). We present molecular dynamics simulations and free energy calculations suggesting that Watson-Crick base pairing could be employed in poliota for bypass of dG-AAF. In poliota with Hoogsteen-paired dG-AAF the bulky AAF moiety would reside on the cramped minor groove side of the template. The Hoogsteen-capable conformation distorts the active site, disrupting interactions necessary for error-free incorporation of dC opposite the lesion. Watson-Crick pairing places the AAF rings on the spacious major groove side, similar to the position of minor groove adducts observed with Hoogsteen pairing. Watson-Crick-paired structures show a well-ordered active site, with a near reaction-ready ternary complex. Thus our results suggest that poliota would utilize the same spacious region for lesion bypass of both major and minor groove adducts. Therefore, purine adducts with bulk on the minor groove side would use Hoogsteen pairing, while adducts with the bulky lesion on the major groove side would utilize Watson-Crick base pairing as indicated by our MD simulations for dG-AAF. This suggests the possibility of an expanded role for poliota in lesion bypass.
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Affiliation(s)
- Kerry Donny-Clark
- Department of Biology and Chemistry, New York University, New York, New York 10003, USA
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40
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Jain N, Meneni S, Jain V, Cho BP. Influence of flanking sequence context on the conformational flexibility of aminofluorene-modified dG adduct in dA mismatch DNA duplexes. Nucleic Acids Res 2009; 37:1628-37. [PMID: 19151371 PMCID: PMC2655675 DOI: 10.1093/nar/gkn1063] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
When positioned opposite to a dA in a DNA duplex, the prototype arylamine-DNA adduct [N-(2'-deoxyguanosin-yl)-7-fluoro-2-aminofluorene (FAF)] adopts the so-called 'wedge' (W) conformation, in which the carcinogen resides in the minor groove of the duplex. All 16 FAF-modified 12-mer NG*N/NAN dA mismatch duplexes (G* = FAF, N = G, A, C, T) exhibited strongly positive induced circular dichroism in the 290-360 nm range (ICD(290-360 nm)), which supports the W conformation. The ICD(290-360 nm) intensities were the greatest for duplexes with a 3'-flanking T. The AG*N duplex series showed little adduct-induced destabilization. An exception was the AG*T duplex, which displayed two well-resolved signals in the (19)F NMR spectra. This was presumably due to a strong lesion-destabilizing effect of the 3'-T. The flanking T effect was substantiated further by findings with the TG*T duplex, which exhibited greater lesion flexibility and nucleotide excision repair recognition. Adduct conformational heterogeneity decreased in order of TG*T > AG*T > CG*T > AG*A > AG*G > AG*C. The dramatic flanking T effect on W-conformeric duplexes is consistent with the strong dependence of the ICD(290-360) on both temperature and salt concentration and could be extended to the arylamine food mutagens that are biologically relevant in humans.
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Affiliation(s)
- Nidhi Jain
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, RI 02881, USA
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41
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Jain N, Reshetnyak YK, Gao L, Chiarelli MP, Cho BP. Fluorescence probing of aminofluorene-induced conformational heterogeneity in DNA duplexes. Chem Res Toxicol 2008; 21:445-52. [PMID: 18193841 DOI: 10.1021/tx7003536] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Fluorescence spectroscopy was used to study carcinogen-induced conformational heterogeneity in DNA duplexes. The fluorophore 2-aminopurine (AP) was incorporated adjacent (5') to the lesion (G*) in eight different DNA duplexes [d(5'-CTTCT PG* NCCTC-3'):d(5'-GAGGN XTAGAAG-3'), G* = FAF adduct, P = AP, N = G, A, C, T, and X = C, A] modified by FAF [ N-(2'-deoxyguanosin-8-yl)-7-fluoro-2-aminofluorene], a fluorine-tagged model DNA adduct derived from the potent carcinogen 2-aminofluorene. Steady-state measurements showed that fluorescence intensity and Stern-Volmer constants ( Ksv) derived from acrylamide quenching experiments decreased for all carcinogen-modified duplexes relative to the controls, which suggests greater AP stacking in the duplex upon adduct formation. Conformation-specific stacking of AP with the neighboring adduct was evidenced by a sequence-dependent variation in fluorescence intensity, position of emission maximum, degree of emission quenching by acrylamide, and temperature-dependent spectral changes. The magnitude of stacking was in the order of FAF residue in base-displaced stacked (S) > minor groove wedged (W) > major groove B type (B). This work represents a novel utility of AP in probing adduct-induced conformational heterogeneities in DNA duplexes.
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Affiliation(s)
- Nidhi Jain
- Department of Biomedical and Pharmaceutical Sciences and Physics, University of Rhode Island, Kingston, RI 02881, USA
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42
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Broyde S, Wang L, Zhang L, Rechkoblit O, Geacintov NE, Patel DJ. DNA adduct structure-function relationships: comparing solution with polymerase structures. Chem Res Toxicol 2007; 21:45-52. [PMID: 18052109 DOI: 10.1021/tx700193x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
It has now been nearly two decades since the first solution structures of DNA duplexes covalently damaged by metabolically activated polycyclic aromatic hydrocarbons and amines were determined by NMR. Dozens of such high-resolution structures are now available, and some broad structural themes have been uncovered. It has been hypothesized that the solution structures are relevant to the biochemical processing of the adducts. The structural features of the adducts are considered to determine their mutational properties in DNA polymerases and their repair susceptibilities. In recent years, a number of crystal structures of DNA adducts of interest to our work have been determined in DNA polymerases. Accordingly, it is now timely to consider how NMR solution structures relate to structures within DNA polymerases. The NMR solution structural themes for polycyclic aromatic adducts are often observed in polymerase crystal structures. While the polymerase interactions can on occasion override the solution preferences, intrinsic adduct conformations favored in solution are often manifested within polymerases and likely play a significant role in lesion processing.
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Affiliation(s)
- Suse Broyde
- Department of Biology, New York University, New York NY 10003, USA.
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43
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Jain N, Li Y, Zhang L, Meneni SR, Cho BP. Probing the sequence effects on NarI-induced -2 frameshift mutagenesis by dynamic 19F NMR, UV, and CD spectroscopy. Biochemistry 2007; 46:13310-21. [PMID: 17960913 DOI: 10.1021/bi701386f] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The NarI recognition sequence (5'-G1G2CG3CN-3') is the most vulnerable hot spot for frameshift mutagenesis induced by the carcinogen 2-aminofluorene and its analogues in Escherichia coli. Lesioning of the guanine in the G3 position induces an especially high frequency of -2 deletion mutations; vulnerability to these mutations is modulated by the nature of the nucleotide in the N position (C approximately A > G > T). The objective of the present study was to probe the structural basis of this N-mediated influence on the propensity of the G3 lesion to form a slipped mutagenic intermediate (SMI) during translesion synthesis. We studied NarI-based fully paired [(5'-CTCG1G2CG3*CNATC-3')(5'-GATNCGGCCGAG-3'), N = dC or dT] and -2 deletion [(5'-CTCG1G2CG3*CNATC-3')(5'-GATNGCCGAG-3'), N = dC or dT] duplexes, in which G* was either AF [N-(2'-deoxyguanosin-8-yl)-2-aminofluorene] or the 19F probe FAF [N-(2'-deoxyguanosin-8-yl)-7-fluoro-2-aminofluorene]. The latter sequences mimic the bulged SMI for -2 deletion mutations. Dynamic 19F NMR, circular dichroism, and UV melting results indicated that the NarI-dC/-2 deletion duplex adopts exclusively an intercalated conformer, whereas the NarI-dT/-2 deletion duplex exists as multiple conformers. The data support the presence of a putative equilibrium between a carcinogen-intercalated and a carcinogen-exposed SMI for the dT/-2 duplex. A similar dT-induced conformational heterogeneity was observed for the fully paired duplexes in which all three guanines were individually modified by AF or FAF. The frequency of the carcinogen stacked S-conformation was found to be highest (69-75%) at the G3 hot spot in NarI-dC duplexes. Taken together, our results support the hypothesis that the conformational stability of the SMI is a critical determinant for the efficacy of -2 frameshift mutagenesis in the NarI sequence. We also provide evidence for AF/FAF conformational compatibility in the NarI sequences.
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Affiliation(s)
- Nidhi Jain
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, Rhode Island 02881, USA
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Cai Y, Patel DJ, Geacintov NE, Broyde S. Dynamics of a benzo[a]pyrene-derived guanine DNA lesion in TGT and CGC sequence contexts: enhanced mobility in TGT explains conformational heterogeneity, flexible bending, and greater susceptibility to nucleotide excision repair. J Mol Biol 2007; 374:292-305. [PMID: 17942115 DOI: 10.1016/j.jmb.2007.09.034] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2007] [Revised: 08/07/2007] [Accepted: 09/04/2007] [Indexed: 11/19/2022]
Abstract
The nucleotide excision repair (NER) machinery excises a variety of bulky DNA lesions, but with varying efficiencies. The structural features of the DNA lesions that govern these differences are not well understood. An intriguing model system for studying structure-function relationships in NER is the major adduct derived from the reaction of the highly tumorigenic metabolite of benzo[a]pyrene, (+)-anti-benzo[a]pyrene diol epoxide, with the exocyclic amino group of guanine ((+)-trans-anti-[BP]-N(2)-dG, or G*). The rates of incision of the stereochemically identical lesions catalyzed by the prokaryotic UvrABC system was shown to be greater by a factor of 2.3+/-0.3 in the TG*T than in the CG*C sequence context [Biochemistry 46 (2007) 7006-7015]. Here we employ molecular dynamics simulations to elucidate the origin of the greater excision efficiency in the TG*T case and, more broadly, to delineate structural parameters that enhance NER. Our results show that the BP aromatic ring system is 5'-directed along the modified strand in the B-DNA minor groove in both sequence contexts. However, the TG*T modified duplex is much more dynamically flexible, featuring more perturbed and mobile Watson-Crick hydrogen bonding adjacent to the lesion, a greater impairment in stacking interactions, more dynamic local roll/bending, and more minor groove flexibility. These characteristics explain a number of experimental observations concerning the (+)-trans-anti-[BP]-N(2)-dG adduct in double-stranded DNA with the TG*T sequence context: its conformational heterogeneity in NMR solution studies, its highly flexible bend, and its lower thermal stability. By contrast, the CG*C modified duplex is characterized by a single BP conformation and a rigid bend. While current recognition models of bulky lesions by NER factors have stressed the importance of impaired Watson-Crick pairing/stacking and bending, our results highlight the likelihood of an important role for the local dynamics in the vicinity of the lesion.
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Affiliation(s)
- Yuqin Cai
- Department of Chemistry, New York University, New York, NY 10003, USA
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45
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Meneni S, Liang F, Cho BP. Examination of the long-range effects of aminofluorene-induced conformational heterogeneity and its relevance to the mechanism of translesional DNA synthesis. J Mol Biol 2006; 366:1387-400. [PMID: 17217958 PMCID: PMC1850230 DOI: 10.1016/j.jmb.2006.12.023] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2006] [Revised: 12/06/2006] [Accepted: 12/12/2006] [Indexed: 10/23/2022]
Abstract
Adduct-induced conformational heterogeneity complicates the understanding of how DNA adducts exert mutation. A case in point is the N-deacetylated AF lesion [N-(2'-deoxyguanosin-8-yl)-2-aminofluorene], the major adduct derived from the strong liver carcinogen N-acetyl-2-aminofluorene. Three conformational families have been previously characterized and are dependent on the positioning of the aminofluorene rings: B is in the "B-DNA" major groove, S is "stacked" into the helix with base-displacement, and W is "wedged" into the minor groove. Here, we conducted (19)F NMR, CD, T(m), and modeling experiments at various primer positions with respect to a template modified by a fluorine tagged AF-adduct (FAF). In the first set, the FAF-G was paired with C and in the second set it was paired with A. The FAF-G:C oligonucleotides were found to preferentially adopt the B or S-conformers while the FAF-G:A mismatch ones preferred the B and W-conformers. The conformational preferences of both series were dependent on temperature and complementary strand length; the largest differences in conformation were displayed at lower temperatures. The CD and T(m) results are in general agreement with the NMR data. Molecular modeling indicated that the aminofluorene moiety in the minor groove of the W-conformer would impose a steric clash with the tight-packing amino acid residues on the DNA binding area of the Bacillus fragment (BF), a replicative DNA polymerase. In the case of the B-type conformer, the carcinogenic moiety resides in the solvent-exposed major groove throughout the replication/translocation process. The present dynamic NMR results, combined with previous primer extension kinetic data by Miller & Grollman, support a model in which adduct-induced conformational heterogeneities at positions remote from the replication fork affect polymerase function through a long-range DNA-protein interaction.
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Affiliation(s)
| | | | - Bongsup P. Cho
- *Address correspondence to: Bongsup P. Cho, Dept. of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, 41 Lower College Road, Kingston, Rhode Island 02881, Tel. 401-874-5024; Fax. 401-874-5766;
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Wang L, Broyde S. A new anti conformation for N-(deoxyguanosin-8-yl)-2-acetylaminofluorene (AAF-dG) allows Watson-Crick pairing in the Sulfolobus solfataricus P2 DNA polymerase IV (Dpo4). Nucleic Acids Res 2006; 34:785-95. [PMID: 16452300 PMCID: PMC1360743 DOI: 10.1093/nar/gkj479] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Primer extension studies have shown that the Y-family DNA polymerase IV (Dpo4) from Sulfolobus solfataricus P2 can preferentially insert C opposite N-(deoxyguanosin-8-yl)-2-acetylaminofluorene (AAF-dG) [F. Boudsocq, S. Iwai, F. Hanaoka and R. Woodgate (2001) Nucleic Acids Res., 29, 4607–4616]. Our goal is to elucidate on a structural level how AAF-dG can be harbored in the Dpo4 active site opposite an incoming dCTP, using molecular modeling and molecular dynamics simulations, since AAF-dG prefers the syn glycosidic torsion. Both anti and syn conformations of the templating AAF-dG in a Dpo4 ternary complex were investigated. All four dNTPs were studied. We found that an anti glycosidic torsion with C1′-exo deoxyribose conformation allows AAF-dG to be Watson–Crick hydrogen-bonded with dCTP with modest polymerase perturbation, but other nucleotides are more distorting. The AAF is situated in the Dpo4 major groove open pocket with fluorenyl rings 3′- and acetyl 5′-directed along the modified strand, irrespective of dNTP. With AAF-dG syn, the fluorenyl rings are in the small minor groove pocket and the active site region is highly distorted. The anti-AAF-dG conformation with C1′-exo sugar pucker can explain the preferential incorporation of dC by Dpo4. Possible relevance of our new major groove structure for AAF-dG to other polymerases, lesion repair and solution conformations are discussed.
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Affiliation(s)
| | - Suse Broyde
- To whom all correspondence should be addressed. Tel: +1 212 998 8231; Fax: +1 212 995 4015;
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Meneni SR, D'Mello R, Norigian G, Baker G, Gao L, Chiarelli MP, Cho BP. Sequence effects of aminofluorene-modified DNA duplexes: thermodynamic and circular dichroism properties. Nucleic Acids Res 2006; 34:755-63. [PMID: 16449208 PMCID: PMC1356535 DOI: 10.1093/nar/gkj480] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2005] [Revised: 01/14/2005] [Accepted: 01/14/2005] [Indexed: 11/12/2022] Open
Abstract
Circular dichroism (CD) and UV-melting experiments were conducted with 16 oligodeoxynucleotides modified by the carcinogen 2-aminofluorene, whose sequence around the lesion was varied systematically [d(CTTCTNG[AF]NCCTC), N = G, A, C, T], to gain insight into the factors that determine the equilibrium between base-displaced stacked (S) and external B-type (B) duplex conformers. Differing stabilities among the duplexes can be attributed to different populations of S and B conformers. The AF modification always resulted in sequence-dependent thermal (T(m)) and thermodynamic (-DeltaG degrees ) destabilization. The population of B-type conformers derived from eight selected duplexes (i.e. -AG*N- and -CG*N-) was inversely proportional to the -DeltaG degrees and T(m) values, which highlights the importance of carcinogen/base stacking in duplex stabilization even in the face of disrupted Watson-Crick base pairing in S-conformation. CD studies showed that the extent of the adduct-induced negative ellipticities in the 290-350 nm range is correlated linearly with -DeltaG degrees and T(m), but inversely with the population of B-type conformations. Taken together, these results revealed a unique interplay between the extent of carcinogenic interaction with neighboring base pairs and the thermodynamic properties of the AF-modified duplexes. The sequence-dependent S/B heterogeneities have important implications in understanding how arylamine-DNA adducts are recognized in nucleotide excision repair.
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Affiliation(s)
- Srinivasa Rao Meneni
- Department of Biomedical and Pharmaceutical Sciences, University of Rhode IslandKingston, RI 02881, USA
- Department of Chemistry, Loyola UniversityChicago, IL 60626, USA
| | - Rhijuta D'Mello
- Department of Biomedical and Pharmaceutical Sciences, University of Rhode IslandKingston, RI 02881, USA
- Department of Chemistry, Loyola UniversityChicago, IL 60626, USA
| | - Gregory Norigian
- Department of Biomedical and Pharmaceutical Sciences, University of Rhode IslandKingston, RI 02881, USA
- Department of Chemistry, Loyola UniversityChicago, IL 60626, USA
| | - Gregory Baker
- Department of Biomedical and Pharmaceutical Sciences, University of Rhode IslandKingston, RI 02881, USA
- Department of Chemistry, Loyola UniversityChicago, IL 60626, USA
| | - Lan Gao
- Department of Chemistry, Loyola UniversityChicago, IL 60626, USA
| | | | - Bongsup P. Cho
- To whom correspondence should be addressed at Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, 41 Lower College Road, Kingston, RI 02881, USA. Tel: +1 401 874 5024; Fax: +1 401 874 5766;
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