PROJECT SUMMARY Exposure to environmental and endogenous agents, which can induce DNA damage to both the nuclear and mitochondrial genomes, represents 80-90% of the human risk of developing major diseases such as cancer, and degenerative diseases. While much of the research to date has been on nuclear DNA, it is becoming increasingly clear that damage to the mitochondrial genome, specifically, plays a critical role in the pathogenesis of a number of major human diseases, in particular, neurodegenerative diseases, together with aging. The emerging technique of DNA adductomics offers the potential to comprehensively assess the totality of adducts in the genome. We are the first to perform urinary DNA adductomics, which represents an important route to simply, and non-invasively, evaluate the totality of adducts in human populations. The presence of DNA adducts in urine is a consequence of repair of the nuclear and mitochondrial genomes, which results in the generation of modified nucleobases and 2’-deoxyribonucleosides. However, the relative contributions from the nuclear and mitochondrial genomes to urinary adduct levels is not clear, and cellular DNA adductomics has yet to be applied to discriminate between nuclear and mitochondrial DNA damage. We propose to use DNA adductomics to study the formation and repair of the spectra of adducts formed in the nuclear and mitochondrial genomes following exposure to key environmental agents of concern. This will determine their relative sensitivities to damage formation, whether there is preferential targeting of one genome, the likelihood of damage persistence, and potential contributions to urinary adduct levels. Such findings are integral to, and will enhance the results of, the parent R01. Advancing our knowledge in these areas will present pivotal opportunities for the diversity candidate to receive world-class mentoring, and training in a cutting-edge field, acquiring, as a result, expertise in both performing DNA adductomics, and the subsequent data analysis. The mentoring, training, and expertise acquired during the project will provide the candidate with the necessary career development experiences in preparation for an independent career in health-related research. Our hypothesis is that exogenous and endogenous cancer risk factors act, in part, through the formation of DNA adducts. Evaluation of these adducts informs on the nature and size of exposure, and, consequently, the disease risk. Application of DNA adductomics will facilitate testing this hypothesis, and ultimately, may highlight the nature of those environmental agents which target mitochondrial specifically, and are therefore, likely to have a preferential role in mitochondrial dysfunction and disease.