A causative role has been established between compromised DNA repair and the development of human cancers. DNA bases are subject to oxidative stress undergoing chemical modification of guanine and other bases as a result of endogenous oxidants, inflammatory responses to infection and injury, and exposure to redox-active environmental toxins. While much attention has been focused on G to T mutations as a result of the oxidized guanine lesion 8-oxoguanine (OG), this project investigates the hyperoxidized guanine lesions resulting from further oxidation of OG. These lesions constitute a family of highly mutagenic hydantoin structures including spiroiminodihydantoin (Sp) and guanidinohydantoin (Gh) that appear to cause G to C in addition to G to T mutations. In the present work, related members of this class of compounds will be studied to further explore the relationship between oxidation pathway, product structure, and activity with DNA processing enzymes including base excision repair and nucleotide excision repair mechanisms. The new structures to be studied include amine adducts of oxidized guanosine. Novel pathways are proposed that might explain additional observations in the mutagenic spectrum of oxidative stress, including the formation of double-stranded tandem lesions.
The specific aims of this work are to: (1) resolve structural questions surrounding the formation of hydantoin lesions in duplex DNA through the use of synthetic lesion-containing oligodeoxynucleotides, mass spectrometry, and x-ray crystallography, (2) understand the roles of base excision repair vs. nucleotide excision repair for hydantoin lesions via in vitro and in vivo biochemical assays with a particular focus on the role of the Nei-like (hNEIL1) and Fpg glycosylases, and (3) develop innovative assays to detect hydantoin products in cell lysates by generating aptamers to DNA lesions coupled to fluorescent readouts.

Public Health Relevance

Oxidative stress plays a significant role in the damaging DNA creating lesions that underlie cancer, aging, neurological and cardiac disorders. This project will help define how specific oxidized DNA bases and base adducts lead to mutations related to cancer. In addition, methods will be developed to monitor the formation and excision of these damaged bases from DNA, revealing new information about the relationship between DNA damage and cancer.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
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Cancer Etiology Study Section (CE)
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Okano, Paul
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University of Utah
Schools of Arts and Sciences
Salt Lake City
United States
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An, Na; Fleming, Aaron M; Burrows, Cynthia J (2016) Human Telomere G-Quadruplexes with Five Repeats Accommodate 8-Oxo-7,8-dihydroguanine by Looping out the DNA Damage. ACS Chem Biol 11:500-7
Fleming, Aaron M; Ding, Yun; Alenko, Anton et al. (2016) Zika Virus Genomic RNA Possesses Conserved G-Quadruplexes Characteristic of the Flaviviridae Family. ACS Infect Dis 2:674-681
Fleming, Aaron M; Burrows, Cynthia J (2016) Formation and processing of DNA damage substrates for the hNEIL enzymes. Free Radic Biol Med :
Zhu, Judy; Fleming, Aaron M; Orendt, Anita M et al. (2016) pH-Dependent Equilibrium between 5-Guanidinohydantoin and Iminoallantoin Affects Nucleotide Insertion Opposite the DNA Lesion. J Org Chem 81:351-9
Fleming, Aaron M; Armentrout, Erin I; Zhu, Judy et al. (2015) Spirodi(iminohydantoin) products from oxidation of 2'-deoxyguanosine in the presence of NH4Cl in nucleoside and oligodeoxynucleotide contexts. J Org Chem 80:711-21
Fleming, Aaron M; Zhou, Jia; Wallace, Susan S et al. (2015) A Role for the Fifth G-Track in G-Quadruplex Forming Oncogene Promoter Sequences during Oxidative Stress: Do These ""Spare Tires"" Have an Evolved Function? ACS Cent Sci 1:226-233
Zhou, Jia; Fleming, Aaron M; Averill, April M et al. (2015) The NEIL glycosylases remove oxidized guanine lesions from telomeric and promoter quadruplex DNA structures. Nucleic Acids Res 43:7171
Alshykhly, Omar R; Fleming, Aaron M; Burrows, Cynthia J (2015) 5-Carboxamido-5-formamido-2-iminohydantoin, in Addition to 8-oxo-7,8-Dihydroguanine, Is the Major Product of the Iron-Fenton or X-ray Radiation-Induced Oxidation of Guanine under Aerobic Reducing Conditions in Nucleoside and DNA Contexts. J Org Chem 80:6996-7007
Zhou, Jia; Fleming, Aaron M; Averill, April M et al. (2015) The NEIL glycosylases remove oxidized guanine lesions from telomeric and promoter quadruplex DNA structures. Nucleic Acids Res 43:4039-54
Alshykhly, Omar R; Fleming, Aaron M; Burrows, Cynthia J (2015) Guanine oxidation product 5-carboxamido-5-formamido-2-iminohydantoin induces mutations when bypassed by DNA polymerases and is a substrate for base excision repair. Chem Res Toxicol 28:1861-71

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