Environmental Regulation of Cellular Responses to DNA Damage

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SUMMARY The overarching goal of this project is to understand how the DNA Damage Response (DDR) activates apoptotic cell death. The DDR is a kinase driven signaling pathway that coordinates multiple cellular functions, including: surveillance for DNA damage, recruitment of DNA repair enzymes, and activation of cell cycle checkpoint arrest. Collectively, these events promote survival following genotoxic stress. Alternatively, in some cases the DDR activates apoptosis. Although much is known about these each of these functions, it still remains unclear why activation of the DDR leads to survival in some cases and death in others. The current model suggests that p53 controls the decision to arrest and repair, or alternatively, to activate cell death. This model does not explain the common observation that cancer cells – which often lack p53 – can robustly activate apoptosis when exposed to DNA damage. Thus, other unidentified mechanisms must also exist to facilitate DDR-induced cell death. Our strategy for identifying mechanisms by which the DDR activates apoptosis was to perform functional genetic screens in cells that lack p53 but retain high levels of DNA damage sensitivity. Our screen has identified that activation of caspase-1 and caspase-1 associated inflammatory cytokine signaling is required for robust DNA damage induced cell death. This was unexpected because unlike other members of the caspase family, caspase-1 is not thought to contribute to apoptotic cell death. In this proposal, we will use live cell microscopy experiments to determine the fate of cells that have activated caspase-1. Additionally, we will use biochemical and genetic experiments to determine mechanisms by which caspase-1 is activated by DNA damage. Finally, we will use high-throughput targeted proteomic and genomic analyses, together with data driven statistical modeling, to determine mechanisms by which caspase- 1 signaling is integrated with the DDR to promote apoptotic cell death. A major outcome from this study will be an understanding of how intra-cellular and inter-cellular crosstalk between inflammatory and DDR signaling helps to facilitate activation of apoptosis. This information may help to understand the variable sensitivity to DNA damage that is observed across tissues and across people, and may ultimately improve our ability to reliably control life-death decisions following DNA damage.