Functional Roles of Homologous Recombination and Non-Homologous End Joining in DNA Damage Response and Microevolution in .

DNA double-strand breaks (DSBs) are the most deleterious type of DNA lesions because they cause loss of genetic information if not properly repaired. In eukaryotes, homologous recombination (HR) and non-homologous end joining (NHEJ) are required for DSB repair. However, the relationship of HR and NHEJ in DNA damage stress is unknown in the radiation-resistant fungus . In this study, we found that the expression levels of HR- and NHEJ-related genes were highly induced in a Rad53-Bdr1 pathway-dependent manner under genotoxic stress. Deletion of , which is one of the main components in the HR, resulted in growth under diverse types of DNA damage stress, whereas perturbations of and , which belong to the NHEJ system, did not affect the genotoxic stresses except when bleomycin was used for treatment. Furthermore, deletion of both and / renders cells susceptible to oxidative stress. Notably, we found that deletion of induced a hypermutator phenotype in the fluctuation assay. In contrast to the fluctuation assay, perturbation of or induced rapid microevolution similar to that induced by the deletion of . Collectively, Rad51-mediated HR and Ku70/Ku80-mediated NHEJ regulate the DNA damage response and maintain genome stability.