Abstract 2546: A novel DNA damage detection assay reveals a critical role of XPF in the repair of endogenous damage
Authors: Mills Wilbur K. , Reis Antonio M.C. , Queimado Lurdes 
Published: August 2012

Abstract
Introduction: DNA damage, notably that resulting from defective nucleotide excision repair (NER), can lead to a number of diseases including those associated with neurodegeneration and cancer. XPF, a gene essential for effective NER, is typically associated with the repair of chemically and UV induced bulky DNA lesions as well as crosslinks. Recently, we developed a novel DNA damage detection assay (PADDA) capable of detecting at the nucleotide level, on a high-throughput scale, endogenous and induced DNA damage. We have previously validated this assay using multiple in vitro and in vivo approaches. By applying this assay to the study of wild-type (WT) and base excision repair (BER) defective cells, we have also reported the first direct evidence for preferential strand repair of endogenous DNA damage and documented the major role of BER in this process. In this study, we used PADDA to determine the role of XPF in the repair of endogenous DNA damage. Methods: Endogenous DNA damage was detected in the CAN1 gene by PADDA in wild-type and XPF defective S. cerevisiae cells in stationary phases of growth. Levels and locations of lesions were compared between strains. Locations of DNA damage were then compared to sites of previously reported mutations in the CAN1 gene using statistical approaches based on Chi-square goodness of fit and exact nonparametric tests. Results: PADDA revealed higher levels of endogenous DNA damage in XPF defective yeast cells compared to WT. Furthermore, a significantly higher rate of polymerase by-passable DNA damage was observed in XPF defective yeast cells compared to WT. There was a high association between the sites of by-passable endogenous DNA damage found in XPF defective cells to sites of previously reported mutations in the CAN1 gene. Conclusions: Our results establish yet another novel role for XPF protein: a major function in the repair of endogenous DNA damage. Furthermore, our results suggest a key XPF role in the repair of highly mutagenic by-passable DNA damage and therefore in the prevention of mutations caused by endogenous DNA damage. Given this important role, XPF may become a biomarker of cancer risk or even a suitable target for strategies aimed at preventing cancer and other diseases associated with DNA damage. Additionally, the ability of PADDA to map and quantify many different types of DNA damage suggests it may become a very important clinical tool to assess cancer risk and response to chemotherapy. Funding: This work was supported by the National Institute of Health [R03 CA117316-01] (AR) and the OUHSC Vice President for Research Fund (LQ). L.Q. holds a Presbyterian Health Foundation Endowed Chair in Otorhinolaryngology.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2546. doi:1538-7445.AM2012-2546