Push it over the limit: Elevating DNA double-strand break toxicity

Abstract

The integrity of our genome is constantly threatened by a variety of endogenous and exogenous sources. Repair of the lesions that arise in our DNA because of these insults to the genome is of utmost importance, as failure to repair them can lead to mutagenesis, cancer formation or cell death. Of the different types of DNA damage, the DNA double-strand break (DSB) is one of the most toxic lesions. Considering that the repair of DSBs is a crucial event during cellular homeostasis, studying the molecular details of the repair process provides many novel insights that could potentially help prevent cancer formation. We studied the response to DSBs from different angles to uncover ways to enhance their toxicity, which will hopefully allow better understanding of the cellular response to DNA damage, as well as more effective treatments for cancer patients. In this thesis, different aspects of the DNA damage response were investigated with the goal to enhance the toxicity of DSBs. This toxicity was first probed in the context of chromatin environment. We then performed a genetic screen to identify novel sensitizers to ionizing radiation (IR). In the course of this work, we confirmed two hits from our screen, showing that depletion of these proteins results in increased sensitivity to IR. Lastly, we used a microscopy-based drug screening approach to identify compounds that lead to increased cellular toxicity of IR. This approach allowed us to identify multiple drugs that have the potential to enhance IR-induced sensitivity.