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.
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.
|Rogers, R Aaron; Fleming, Aaron M; Burrows, Cynthia J (2018) Unusual Isothermal Hysteresis in DNA i-Motif pH Transitions: A Study of the RAD17 Promoter Sequence. Biophys J 114:1804-1815|
|Fleming, Aaron M; Zhu, Judy; Ding, Yun et al. (2018) Human DNA Repair Genes Possess Potential G-Quadruplex Sequences in Their Promoters and 5'-Untranslated Regions. Biochemistry 57:991-1002|
|Omaga, Carla A; Fleming, Aaron M; Burrows, Cynthia J (2018) The Fifth Domain in the G-Quadruplex-Forming Sequence of the Human NEIL3 Promoter Locks DNA Folding in Response to Oxidative Damage. Biochemistry 57:2958-2970|
|Zhu, Judy; Fleming, Aaron M; Burrows, Cynthia J (2018) The RAD17 Promoter Sequence Contains a Potential Tail-Dependent G-Quadruplex That Downregulates Gene Expression upon Oxidative Modification. ACS Chem Biol 13:2577-2584|
|Fleming, Aaron M; Burrows, Cynthia J (2017) 8-Oxo-7,8-dihydroguanine, friend and foe: Epigenetic-like regulator versus initiator of mutagenesis. DNA Repair (Amst) 56:75-83|
|Fleming, Aaron M; Burrows, Cynthia J (2017) Formation and processing of DNA damage substrates for the hNEIL enzymes. Free Radic Biol Med 107:35-52|
|Fleming, Aaron M; Ding, Yun; Burrows, Cynthia J (2017) Sequencing DNA for the Oxidatively Modified Base 8-Oxo-7,8-Dihydroguanine. Methods Enzymol 591:187-210|
|Fleming, Aaron M; Zhu, Judy; Ding, Yun et al. (2017) 8-Oxo-7,8-dihydroguanine in the Context of a Gene Promoter G-Quadruplex Is an On-Off Switch for Transcription. ACS Chem Biol 12:2417-2426|
|Fleming, Aaron M; Ding, Yun; Burrows, Cynthia J (2017) Oxidative DNA damage is epigenetic by regulating gene transcription via base excision repair. Proc Natl Acad Sci U S A 114:2604-2609|
|Ding, Yun; Fleming, Aaron M; Burrows, Cynthia J (2017) Sequencing the Mouse Genome for the Oxidatively Modified Base 8-Oxo-7,8-dihydroguanine by OG-Seq. J Am Chem Soc 139:2569-2572|
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