Chromosome copy number analysis (WGS) of repair-proficient and repair-deficient yeast strains (S. cerevisiae) after genotoxic treatment with camptothecin or X-ray irradiation

We investigated how yeast cells deficient in performing homologous recombination-mediated DNA repair due to a deletion of the critical RAD52 gene respond to irreparable DNA damage inflicted by genotoxic treatment commonly applied in cancer therapy (camptothecin and irradiation). We found that upon persistence of irreparable DNA damage, yeast rad52 mutants readily undergo checkpoint adaptation accompanied by the acquisition of resistance to further genotoxic insults as well as the development of aneuploidy. Together, our findings can be used to elucidate how repair-defective cancer cells can become treatment-resistant thereby providing a way to target these resistant cell clones by tackling their aneuploidy-associated phenotypes. To investigate these characteristics commonly present in aneuploid cells in our experimental set-up, we treated yeast cells with genotoxic agents and performed whole genome sequencing. We could identify frequent whole chromosome loss events manifesting in a sensitivity of cells to aneuploidy-targeting agents.