NIH COMMON FUND HIGH-RISK HIGH-REWARD RESEARCH SYMPOSIUM DECEMBER 15 – 17, 2014 SPEAKER ABSTRACTS Multiplexed DNA repair assays for multiple lesions and multiple doses via transcription inhibition and transcriptional mutagenesis. Awardee: Leona D. Samson Award: Pioneer Award Awardee Institution: Massachusetts Institute of Technology The capacity to repair different types of DNA damage varies widely among individuals, making them more or less susceptible to the detrimental health consequences of environmental exposures. Current methods for measuring DNA repair capacity (DRC) are relatively labor intensive, often indirect, and one is usually limited to measuring a single DNA repair pathway. We have developed a fluorescence-based, multiplexed, flow-cytometric host cell reactivation assay (FM-HCR) that simultaneously measures the ability of human cells to repair plasmid reporters, each bearing a different type of DNA damage or different doses of the same type of DNA damage. FM-HCR can simultaneously measure DNA repair capacity for four of different repair pathways, and the pathways that can be measured include the following: nucleotide excision repair, mismatch repair, base excision repair, nonhomologous end joining, homologous recombination, and direct reversal by MGMT. We have shown that FM-HCR can measure interindividual DRC differences in a panel of 24 cell lines derived from genetically diverse, apparently healthy individuals, and that FM-HCR can be used to identify inhibitors or enhancers of DRC. We further developed a next-generation sequencing-based HCR assay (HCR-Seq) that detects rare transcriptional mutagenesis events due to lesion bypass by RNA polymerase II, providing an added dimension to DRC measurements. FM-HCR and HCR-Seq provide powerful tools for exploring relationships among global DRC, disease susceptibility, and optimal cancer therapy.