Radiation-induced unrepairable DSBs: their role in the late effects of radiation and possible applications to biodosimetry

Although the vast majority of DNA damage induced by radiation exposure disappears rapidly, some lesions remain in the cell nucleus in very small quantities for days to months. These lesions may cause a considerable threat to an organism and include certain types of DNA double-strand breaks (DSBs) called ‘unrepairable DSBs’. Unrepairable DSBs are thought to cause persistent malfunctioning of cells and tissues or cause late effects of radiation, especially the induction of delayed cell death, mutation, senescence, or carcinogenesis. Moreover, the measurement of unrepairable DSBs could potentially be used for retrospective biodosimetry or for identifying individuals at greater risk for developing the adverse effects associated with radiotherapy or chemotherapy. This review summarizes the concept of unrepairable DSBs in the context of persistent repair foci formed at DSBs.