Signaling Mechanisms in Genome Maintenance

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PROJECT SUMMARY/ABSTRACT The stability of eukaryotic genomes relies on the tight coordination of DNA metabolic processes with DNA repair and the cell cycle. Central to this coordination are elaborate signaling networks mediated by DNA damage signaling kinases. Mutations in these kinases are associated with a range of human genetic disorders linked to cancer predisposition, neurological defects, and immunodeficiency. Selective inhibitors of DNA damage signaling kinases are now being used in over a hundred clinical trials for cancer therapy. However, fundamental questions related to how these kinases maintain genome integrity remain unanswered. The Smolka Laboratory investigates DNA damage signaling, with a major focus on the phosphatidylinositol 3′ kinase (PI3K)‐related kinases (PIKKs) and PIKK‐regulated downstream checkpoint kinases. In addition to pioneering the use of proteomic approaches for the unbiased mapping PIKK substrates, our work uncovered new mechanisms of DNA repair regulation and DNA damage signaling deactivation. Over the next five years, our research program will explore novel non-canonical roles for PIKKs in genome maintenance and DNA replication that have remained obscured for decades. We will address fundamental questions regarding the identity of key effector proteins by which PIKKs control DNA synthesis and DNA repair transactions, establishing the underlying mechanisms of phospho-regulation and implications for manipulating cellular viability, fitness and drug susceptibilities. We will employ extensive phosphoproteomics and genetic approaches, and incorporate single molecule super resolution microscopy, CRISPR screens and genomic technologies. The proposed work will reveal crucial, yet undefined, layers of PIKK-dependent regulation governing genome maintenance and DNA replication in yeast and mammals. Generated knowledge will also have implications for understanding how cells with unstable genomes, such as cancer cells undergoing oncogene-induced replication stress, co-opt PIKK signaling for unrestrained proliferation and resistance to genotoxic insults. Moreover, our findings will illuminate how inhibitors of PIKKs, already in clinical trials, affect cell viability and genomic integrity, thus informing the design of more effective therapeutic strategies.