| Description |
DNA damage is ubiquitous in nature and cellular response to it is as diverse. Mutations in DNA repair pathways are often associated with disease phenotypes like cancer and neurodegeneration. A lot of our knowledge of DNA damage responses (DDR) comes from important bulk biochemistry experiments. But beyond such mean responses, single-cell level imaging techniques can potentially measure the heterogeneity of cellular responses, and also identify subcellular localization and cell-by-cell correlations of gene products. The Ribonucleotide reductase (RNR) enzyme catalyzes the production of deoxyribonucleotide triphosphates (dNTPs) required for DNA repair. I will first describe experiments where we have simultaneously measured RNR proteins and single molecules of the corresponding transcripts in single budding yeast cells to reveal an unexpected cell-cycle dependent induction of RNR gene products upon genotoxic stress. However, to orchestrate an effective response to DNA damage, cells need to modulate not only the canonical damage-responsive genes like RNR, but the whole gamut of cellular homeostasis. Hence I will describe a genome-wide imaging-based screen in budding yeast to identify the proteins that change levels or localization in response to alkylation damage. Our results revealed a number of cellular processes modulated by such damage that are distinct from canonical DNA repair pathways, including chromatin remodeling, mRNA processing, transcription, proteolysis, ribosome biogenesis, metabolism, lipid synthesis, and others. Finally I will describe some currently ongoing experiments where we investigate DDR in primary tissue from mice with such imaging methods to reveal an intriguing heterogeneity of poly-ADP-ribosylation and HMGB1 translocation upon oxidative stress. Though speculative, I will also attempt to discuss the potential significance of such heterogeneity and my future research plans investigating the connections between global genome organization and tissue-specific emergence of cancer, and the roles of DDR in processes of differentiation and development.
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