To live, aerobic organisms metabolize oxygen to generate energy. During this process, cells create reactive oxygen species (ROS). ROS react with all cellular constituents, including lipids, proteins, and DNA. Such oxidative damage has been associated with the aging process and human disease, namely cancer and neurodegeneration. We have worked to define the biochemical and cellular processes for repairing oxidative DNA damage. In particular, we have delineated the structure-function mechanisms and biological contributions of specific proteins that participate in the base excision repair (BER) pathway. This process involves the recognition and excision of DNA damage, and restoration of the native genetic material. Defects in DNA repair give rise to mutations or cell death, leading to the development of disease.? ? Much of our effort has involved defining the biochemical functions of Ape1, the major human protein for repairing abasic (AP) sites in DNA, a frequent genetic damage. We have demonstrated that Ape1 contributes to the repair of 3?-modifications in DNA as well, including mismatches, phosphate groups, phosphogycolates, and tyrosyl residues. Our more recent work has found that Ape1 cleaves at AP sites in single-stranded regions of complex, biologically-relevant DNA structures, such as bubble and fork intermediates. These findings expand the known repertoire of substrates processed by this enzyme, and suggest novel functions for Ape1 likely coupled to transcription and/or replication. Our recent work has focused on potential mechanisms of regulating Ape1 repair activities. For instance, we have demonstrated that the single-stranded DNA binding protein RPA inhibits promiscuous AP site incision by Ape1. In addition, CSB, a transcription-related repair protein defective in the human premature aging disorder Cockayne Syndrome, was found to activate Ape1 cleavage at AP sites in transcription bubble intermediates. Finally, our studies have discovered that the environmental metal, lead, is a potent inhibitor of Ape1 activity, suggesting a means by which this heavy metal may elicit its co-carcinogenic effects. We are currently designing methods to strategically regulate Ape1 repair activity in cells in the hopes of developing more effective anti-cancer treatment paradigms.? ? In addition to the investigations above, we have initiated studies to determine the biochemical and cellular contributions of XRCC1, a major single-strand break repair (SSBR) factor. This protein functions primarily as a scaffold component, orchestrating specific protein-protein interactions required for efficient DNA repair. Recent work has identified associations of XRCC1 with proteins defective in human neurodegenerative disorders AOA1 (Aprataxin) and SCAN1 (TDP1). Our studies suggest a link of XRCC1 to replication via an interaction with PCNA, argue against a role for XRCC1 in the early steps of BER, and indicate a biologically-relevant role for its interaction with DNA polymerase beta and in the subsequent steps of SSBR, specifically DNA nick ligation. Ongoing studies using animal models (and derived cells) are determining the relationship of XRCC1 and oxidative DNA damage repair to aging and age-related disease, namely neurodegeneration. Additionally, we are determining the contribution, if any, of human XRCC1 and associated protein variants to impaired cellular responses that are related to disease manifestation.

National Institute of Health (NIH)
National Institute on Aging (NIA)
Intramural Research (Z01)
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Wyatt, M D; Wilson 3rd, D M (2009) Participation of DNA repair in the response to 5-fluorouracil. Cell Mol Life Sci 66:788-99
Wilson 3rd, David M; Bohr, Vilhelm A; McKinnon, Peter J (2008) DNA damage, DNA repair, ageing and age-related disease. Mech Ageing Dev 129:349-52
Wilson 3rd, David M (2007) Processing of nonconventional DNA strand break ends. Environ Mol Mutagen 48:772-82
McNeill, Daniel R; Wilson 3rd, David M (2007) A dominant-negative form of the major human abasic endonuclease enhances cellular sensitivity to laboratory and clinical DNA-damaging agents. Mol Cancer Res 5:61-70
Wilson 3rd, David M; Thompson, Larry H (2007) Molecular mechanisms of sister-chromatid exchange. Mutat Res 616:11-23
Fan, Jinshui; Wilson, Paul F; Wong, Heng-Kuan et al. (2007) XRCC1 down-regulation in human cells leads to DNA-damaging agent hypersensitivity, elevated sister chromatid exchange, and reduced survival of BRCA2 mutant cells. Environ Mol Mutagen 48:491-500
Wilson 3rd, D M; McNeill, D R (2007) Base excision repair and the central nervous system. Neuroscience 145:1187-200
Wilson 3rd, David M; Bohr, Vilhelm A (2007) The mechanics of base excision repair, and its relationship to aging and disease. DNA Repair (Amst) 6:544-59
Harrigan, Jeanine A; Fan, Jinshui; Momand, Jamil et al. (2007) WRN exonuclease activity is blocked by DNA termini harboring 3'obstructive groups. Mech Ageing Dev 128:259-66
McNeill, Daniel R; Wong, Heng-Kuan; Narayana, Avinash et al. (2007) Lead promotes abasic site accumulation and co-mutagenesis in mammalian cells by inhibiting the major abasic endonuclease Ape1. Mol Carcinog 46:91-9

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