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Le Meur RA, Pecen TJ, Le Meur KV, Nagel ZD, Chazin WJ. Molecular basis and functional consequences of the interaction between the base excision repair DNA glycosylase NEIL1 and RPA. J Biol Chem 2024; 300:107579. [PMID: 39025455 DOI: 10.1016/j.jbc.2024.107579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2023] [Revised: 06/22/2024] [Accepted: 06/25/2024] [Indexed: 07/20/2024] Open
Abstract
NEIL1 is a DNA glycosylase that recognizes and initiates base excision repair of oxidized bases. The ubiquitous ssDNA binding scaffolding protein, replication protein A (RPA), modulates NEIL1 activity in a manner that depends on DNA structure. Interaction between NEIL1 and RPA has been reported, but the molecular basis of this interaction has yet to be investigated. Using a combination of NMR spectroscopy and isothermal titration calorimetry (ITC), we show that NEIL1 interacts with RPA through two contact points. An interaction with the RPA32C protein recruitment domain was mapped to a motif in the common interaction domain (CID) of NEIL1 and a dissociation constant (Kd) of 200 nM was measured. A substantially weaker secondary interaction with the tandem RPA70AB ssDNA binding domains was also mapped to the CID. Together these two contact points reveal NEIL1 has a high overall affinity (Kd ∼ 20 nM) for RPA. A homology model of the complex of RPA32C with the NEIL1 RPA binding motif in the CID was generated and used to design a set of mutations in NEIL1 to disrupt the interaction, which was confirmed by ITC. The mutant NEIL1 remains catalytically active against a thymine glycol lesion in duplex DNA in vitro. Testing the functional effect of disrupting the NEIL1-RPA interaction in vivo using a Fluorescence Multiplex-Host Cell Reactivation (FM-HCR) reporter assay revealed an unexpected role for NEIL1 in nucleotide excision repair. These findings are discussed in the context of the role of NEIL1 in replication-associated repair.
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Affiliation(s)
- Rémy A Le Meur
- Departments of Biochemistry and Chemistry, Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, USA
| | - Turner J Pecen
- Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
| | - Kateryna V Le Meur
- Departments of Biochemistry and Chemistry, Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, USA
| | - Zachary D Nagel
- Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA.
| | - Walter J Chazin
- Departments of Biochemistry and Chemistry, Center for Structural Biology, Vanderbilt University, Nashville, Tennessee, USA.
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2
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Zuckerman JT, Jackson AS, Minko IG, Kant M, Jaruga P, Stone MP, Dizdaroglu M, McCullough AK, Lloyd RS. Functional characterization of single nucleotide polymorphic variants of DNA repair enzyme NEIL1 in South Asian populations. DNA Repair (Amst) 2024; 139:103695. [PMID: 38795603 PMCID: PMC11218669 DOI: 10.1016/j.dnarep.2024.103695] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Revised: 05/07/2024] [Accepted: 05/14/2024] [Indexed: 05/28/2024]
Abstract
The base excision repair (BER) pathway is a precise and versatile mechanism of DNA repair that is initiated by DNA glycosylases. Endonuclease VIII-like 1 (NEIL1) is a bifunctional glycosylase/abasic site (AP) lyase that excises a damaged base and subsequently cleaves the phosphodiester backbone. NEIL1 is able to recognize and hydrolyze a broad range of oxidatively-induced base lesions and substituted ring-fragmented guanines, including aflatoxin-induced 8,9-dihydro-8-(2,6-diamino-4-oxo-3,4-dihydropyrimid-5-yl-formamido)-9-hydroxyaflatoxin B1 (AFB1-FapyGua). Due to NEIL1's protective role against these and other pro-mutagenic lesions, it was hypothesized that naturally occurring single nucleotide polymorphic (SNP) variants of NEIL1 could increase human risk for aflatoxin-induced hepatocellular carcinoma (HCC). Given that populations in South Asia experience high levels of dietary aflatoxin exposures and hepatitis B viral infections that induce oxidative stress, investigations on SNP variants of NEIL1 that occur in this region may have clinical implications. In this study, the most common South Asian variants of NEIL1 were expressed, purified, and functionally characterized. All tested variants exhibited activities and substrate specificities similar to wild type (wt)-NEIL1 on high-molecular weight DNA containing an array of oxidatively-induced base lesions. On short oligodeoxynucleotides (17-mers) containing either a site-specific apurinic/apyrimidinic (AP) site, thymine glycol (ThyGly), or AFB1-FapyGua, P206L-NEIL1 was catalytically comparable to wt-NEIL1, while the activities of NEIL1 variants Q67K and T278I on these substrates were ≈2-fold reduced. Variant T103A had a greatly diminished ability to bind to 17-mer DNAs, limiting the subsequent glycosylase and lyase reactions. Consistent with this observation, the rate of excision by T103A on 17-mer oligodeoxynucleotides containing ThyGly or AFB1-FapyGua could not be measured. However, the ability of T103A to excise ThyGly was improved on longer oligodeoxynucleotides (51-mers), with ≈7-fold reduced activity compared to wt-NEIL1. Our studies suggest that NEIL1 variant T103A may present a pathogenic phenotype that is limited in damage recognition, potentially increasing human risk for HCC.
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Affiliation(s)
- Jamie T Zuckerman
- Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR 97239, United States
| | - Asia Sage Jackson
- Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR 97239, United States; Department of Math & Sciences, Corban University, Salem, OR 97317, United States
| | - Irina G Minko
- Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR 97239, United States
| | - Melis Kant
- Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, United States
| | - Pawel Jaruga
- Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, United States
| | - Michael P Stone
- Department of Chemistry, Vanderbilt University, Nashville, TN 37240, United States
| | - Miral Dizdaroglu
- Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, United States
| | - Amanda K McCullough
- Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR 97239, United States; Department of Molecular and Medical Genetics, Oregon Health & Science University, Portland, OR, 97239, United States
| | - R Stephen Lloyd
- Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR 97239, United States; Department of Molecular and Medical Genetics, Oregon Health & Science University, Portland, OR, 97239, United States.
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Minko IG, Kellum AH, Stone MP, Lloyd RS. The aflatoxin B 1-induced imidazole ring-opened guanine adduct: High mutagenic potential that is minimally affected by sequence context. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2024; 65 Suppl 1:9-13. [PMID: 37303259 PMCID: PMC10711146 DOI: 10.1002/em.22556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Revised: 04/25/2023] [Accepted: 06/08/2023] [Indexed: 06/13/2023]
Abstract
Dietary exposure to aflatoxin B1 (AFB1) is a recognized risk factor for developing hepatocellular carcinoma. The mutational signature of AFB1 is characterized by high-frequency base substitutions, predominantly G>T transversions, in a limited subset of trinucleotide sequences. The 8,9-dihydro-8-(2,6-diamino-4-oxo-3,4-dihydropyrimid-5-yl-formamido)-9-hydroxyaflatoxin B1 (AFB1-FapyGua) has been implicated as the primary DNA lesion responsible for AFB1-induced mutations. This study evaluated the mutagenic potential of AFB1-FapyGua in four sequence contexts, including hot- and cold-spot sequences as apparent in the mutational signature. Vectors containing site-specific AFB1-FapyGua lesions were replicated in primate cells and the products of replication were isolated and sequenced. Consistent with the role of AFB1-FapyGua in AFB1-induced mutagenesis, AFB1-FapyGua was highly mutagenic in all four sequence contexts, causing G>T transversions and other base substitutions at frequencies of ~80%-90%. These data suggest that the unique mutational signature of AFB1 is not explained by sequence-dependent fidelity of replication past AFB1-FapyGua lesions.
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Affiliation(s)
- Irina G. Minko
- Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd., Portland, OR 97239
| | | | | | - R. Stephen Lloyd
- Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd., Portland, OR 97239
- Department of Molecular and Medical Genetics, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd., Portland, OR 97239
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Minko I, Luzadder M, Vartanian V, Rice SM, Nguyen M, Sanchez-Contreras M, Van P, Kennedy S, McCullough A, Lloyd R. Frequencies and spectra of aflatoxin B 1-induced mutations in liver genomes of NEIL1-deficient mice as revealed by duplex sequencing. NAR MOLECULAR MEDICINE 2024; 1:ugae006. [PMID: 38779538 PMCID: PMC11105970 DOI: 10.1093/narmme/ugae006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Revised: 04/18/2024] [Accepted: 05/16/2024] [Indexed: 05/25/2024]
Abstract
Increased risk for the development of hepatocellular carcinoma (HCC) is driven by a number of etiological factors including hepatitis viral infection and dietary exposures to foods contaminated with aflatoxin-producing molds. Intracellular metabolic activation of aflatoxin B1 (AFB1) to a reactive epoxide generates highly mutagenic AFB1-Fapy-dG adducts. Previously, we demonstrated that repair of AFB1-Fapy-dG adducts can be initiated by the DNA glycosylase NEIL1 and that male Neil1-/- mice were significantly more susceptible to AFB1-induced HCC relative to wild-type mice. To investigate the mechanisms underlying this enhanced carcinogenesis, WT and Neil1-/- mice were challenged with a single, 4 mg/kg dose of AFB1 and frequencies and spectra of mutations were analyzed in liver DNAs 2.5 months post-injection using duplex sequencing. The analyses of DNAs from AFB1-challenged mice revealed highly elevated mutation frequencies in the nuclear genomes of both males and females, but not the mitochondrial genomes. In both WT and Neil1-/- mice, mutation spectra were highly similar to the AFB1-specific COSMIC signature SBS24. Relative to wild-type, the NEIL1 deficiency increased AFB1-induced mutagenesis with concomitant elevated HCCs in male Neil1-/- mice. Our data establish a critical role of NEIL1 in limiting AFB1-induced mutagenesis and ultimately carcinogenesis.
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Affiliation(s)
- Irina G Minko
- Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR, USA
| | - Michael M Luzadder
- Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR, USA
| | - Vladimir L Vartanian
- Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR, USA
| | - Sean P M Rice
- Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR, USA
- School of Public Health, Oregon Health & Science University - Portland State University, Portland, OR, USA
| | - Megan M Nguyen
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, USA
| | | | - Phu Van
- TwinStrand Biosciences, Inc., Seattle, WA, USA
| | - Scott R Kennedy
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, USA
| | - Amanda K McCullough
- Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR, USA
- Department of Molecular and Medical Genetics, Oregon Health & Science University, Portland, OR, USA
| | - R Stephen Lloyd
- Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR, USA
- Department of Molecular and Medical Genetics, Oregon Health & Science University, Portland, OR, USA
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Wu Y, Adeel MM, Sancar A, Li W. Nucleotide Excision Repair of Aflatoxin-induced DNA Damage within the 3D Human Genome Organization. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.27.559858. [PMID: 37808841 PMCID: PMC10557652 DOI: 10.1101/2023.09.27.559858] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/10/2023]
Abstract
Aflatoxin B1 (AFB1), a potent mycotoxin, is one of the two primary risk factors that cause liver cancer. In the liver, the bioactivated AFB1 intercalates into the DNA double helix to form a bulky DNA adduct which will lead to mutation if left unrepaired. We have adapted the tXR-seq method to measure the nucleotide excision repair of AFB1-induced DNA adducts. We have found that transcription-coupled repair plays a major role in the damage removal process and the released excision products have a distinctive length distribution pattern. We further analyzed the impact of 3D genome organization on the repair of AFB1-induced DNA adducts. We have revealed that chromosomes close to the nuclear center and A compartments undergo expedited repair processes. Notably, we observed an accelerated repair around both TAD boundaries and loop anchors. These findings provide insights into the complex interplay between repair, transcription, and 3D genome organization, shedding light on the mechanisms underlying AFB1-induced liver cancer.
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Affiliation(s)
- Yiran Wu
- Department of Environmental Health Science, College of Public Health, University of Georgia, Athens, GA 30602
| | - Muhammad Muzammal Adeel
- Department of Environmental Health Science, College of Public Health, University of Georgia, Athens, GA 30602
| | - Aziz Sancar
- Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599
| | - Wentao Li
- Department of Environmental Health Science, College of Public Health, University of Georgia, Athens, GA 30602
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Zuckerman JT, Minko IG, Kant M, Jaruga P, Stone MP, Dizdaroglu M, McCullough AK, Lloyd RS. Functional analyses of single nucleotide polymorphic variants of the DNA glycosylase NEIL1 in sub-Saharan African populations. DNA Repair (Amst) 2023; 129:103544. [PMID: 37517321 PMCID: PMC10546947 DOI: 10.1016/j.dnarep.2023.103544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 07/07/2023] [Accepted: 07/18/2023] [Indexed: 08/01/2023]
Abstract
Nei-like glycosylase 1 (NEIL1) is a DNA repair enzyme that initiates the base excision repair (BER) pathway to cleanse the human genome of damage. The substrate specificity of NEIL1 includes several common base modifications formed under oxidative stress conditions, as well as the imidazole ring open adducts that are induced by alkylating agents following initial modification at N7 guanine. An example of the latter is the persistent and mutagenic 8,9-dihydro-8-(2,6-diamino-4-oxo-3,4-dihydropyrimid-5-yl-formamido)-9-hydroxyaflatoxin B1 (AFB1-FapyGua) adduct, resulting from the alkylating agent aflatoxin B1 (AFB1) exo-8-9-epoxide. Naturally occurring single nucleotide polymorphic (SNP) variants of NEIL1 are hypothesized to be associated with an increased risk for development of early-onset hepatocellular carcinoma (HCC), especially in environments with high exposures to aflatoxins and chronic inflammation from viral infections and alcohol consumption. Given that AFB1 exposures and hepatitis B viral (HBV) infections represent a major problem in the developing countries of sub-Saharan Africa, it is pertinent to study SNP NEIL1 variants that are present in this geographic region. In this investigation, we characterized the three most common NEIL1 variants found in this region: P321A, R323G, and I182M. Biochemical analyses were conducted to determine the proficiencies of these variants in initiating the repair of DNA lesions. Our data show that damage recognition and excision activities of P321A and R323G were near that of wild-type (WT) NEIL1 for both thymine glycol (ThyGly) and AFB1-FapyGua. The substrate specificities of these variants with respect to various oxidatively-induced base lesions were also similar to that of WT. In contrast, the I182M variant was unstable, such that it precipitated under a variety of conditions and underwent rapid inactivation at a biologically relevant temperature, with partial stabilization being observed in the presence of undamaged DNA. This study provides insight regarding the potential increased risk for early-onset HCC in human populations carrying the NEIL1 I182M variant.
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Affiliation(s)
- Jamie T Zuckerman
- Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR 97239, United States
| | - Irina G Minko
- Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR 97239, United States
| | - Melis Kant
- Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, United States
| | - Pawel Jaruga
- Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, United States
| | - Michael P Stone
- Department of Chemistry, Vanderbilt University, Nashville, TN 37240, United States
| | - Miral Dizdaroglu
- Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, United States
| | - Amanda K McCullough
- Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR 97239, United States; Department of Molecular and Medical Genetics, Oregon Health & Science University, Portland, OR 97239, United States
| | - R Stephen Lloyd
- Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR 97239, United States; Department of Molecular and Medical Genetics, Oregon Health & Science University, Portland, OR 97239, United States.
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Jaruga P, Tomar R, Kant M, Vartanian V, Sexton B, Rizzo CJ, Turesky RJ, Stone MP, Lloyd RS, Dizdaroglu M. Synthesis and Characterization of 15N 5-Labeled Aflatoxin B 1-Formamidopyrimidines and Aflatoxin B 1-N7-Guanine from a Partial Double-Stranded Oligodeoxynucleotide as Internal Standards for Mass Spectrometric Measurements. ACS OMEGA 2023; 8:14841-14854. [PMID: 37125130 PMCID: PMC10134230 DOI: 10.1021/acsomega.3c01328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 03/20/2023] [Indexed: 05/03/2023]
Abstract
Aflatoxin B1 (AFB1) exposure through contaminated food is a primary contributor to hepatocellular carcinogenesis worldwide. Hepatitis B viral infections in livers dramatically increase the carcinogenic potency of AFB1 exposures. Liver cytochrome P450 oxidizes AFB1 to the epoxide, which in turn reacts with N7-guanine in DNA, producing the cationic trans-8,9-dihydro-8-(N7-guanyl)-9-hydroxyaflatoxin B1 adduct (AFB1-N7-Gua). The opening of the imidazole ring of AFB1-N7-Gua under physiological conditions causes the formation of the cis- and trans-diastereomers of 8,9-dihydro-8-(2,6-diamino-4-oxo-3,4-dihydropyrimid-5-yl-formamido)-9-hydroxyaflatoxin B1 (AFB1-FapyGua). These adducts primarily lead to G → T mutations, with AFB1-FapyGua being significantly more mutagenic than AFB1-N7-Gua. The unequivocal identification and accurate quantification of these AFB1-Gua adducts as biomarkers are essential for a fundamental understanding and prevention of AFB1-induced hepatocellular carcinogenesis. Among a variety of analytical techniques used for this purpose, liquid chromatography-tandem mass spectrometry, with the use of the stable isotope-labeled analogues of AFB1-FapyGua and AFB1-N7-Gua as internal standards, provides the greatest accuracy and sensitivity. cis-AFB1-FapyGua-15N5, trans-AFB1-FapyGua-15N5, and AFB1-N7-Gua-15N5 have been synthesized and used successfully as internal standards. However, the availability of these standards from either academic institutions or commercial sources ceased to exist. Thus, quantitative genomic data regarding AFB1-induced DNA damage in animal models and humans remain challenging to obtain. Previously, AFB1-N7-Gua-15N5 was prepared by reacting AFB1-exo-8,9-epoxide with the uniformly 15N5-labeled DNA isolated from algae grown in a pure 15N-environment, followed by alkali treatment, resulting in the conversion of AFB1-N7-Gua-15N5 to AFB1-FapyGua-15N5. In the present work, we used a different and simpler approach to synthesize cis-AFB1-FapyGua-15N5, trans-AFB1-FapyGua-15N5, and AFB1-N7-Gua-15N5 from a partial double-stranded 11-mer Gua-15N5-labeled oligodeoxynucleotide, followed by isolation and purification. We also show the validation of these 15N5-labeled standards for the measurement of cis-AFB1-FapyGua, trans-AFB1-FapyGua, and AFB1-N7-Gua in DNA of livers of AFB1-treated mice.
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Affiliation(s)
- Pawel Jaruga
- Biomolecular
Measurement Division, National Institute
of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Rachana Tomar
- Department
of Chemistry, Vanderbilt Ingram Cancer Center, Vanderbilt University, Nashville, Tennessee 37235, United States
| | - Melis Kant
- Biomolecular
Measurement Division, National Institute
of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Vladimir Vartanian
- Oregon
Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, Oregon 97239, United States
| | - Benjamin Sexton
- Department
of Chemistry, Vanderbilt Ingram Cancer Center, Vanderbilt University, Nashville, Tennessee 37235, United States
| | - Carmelo J. Rizzo
- Department
of Chemistry, Vanderbilt Ingram Cancer Center, Vanderbilt University, Nashville, Tennessee 37235, United States
| | - Robert J. Turesky
- Masonic
Cancer Center, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Michael P. Stone
- Department
of Chemistry, Vanderbilt Ingram Cancer Center, Vanderbilt University, Nashville, Tennessee 37235, United States
| | - R. Stephen Lloyd
- Oregon
Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, Oregon 97239, United States
| | - Miral Dizdaroglu
- Biomolecular
Measurement Division, National Institute
of Standards and Technology, Gaithersburg, Maryland 20899, United States
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