Oxidative DNA lesions destabilize centromeres and drive chromosome instability.

Centromeres are essential regions of the genome that ensure chromosome segregation during mitosis. Yet, they are also hotspots for chromosome breaks and rearrangements in cancer. The mechanisms underlying this fragility is not fully elucidated. Here we show that oxidative DNA damage destabilizes centromeres and promotes chromosome instability. Using a chemoptogenetic system to generate singlet oxygen locally at centromeres, we uncouple centromeric oxidative damage from global oxidative stress. We find that oxidative base lesions activate base excision repair at centromeres but slow DNA synthesis, destabilize CENP-A chromatin, and are converted into DNA breaks that can persist into subsequent cell cycles. Single cell time lapse imaging reveals that the cellular fate of centromeric DNA damage depends on the cell cycle phase during which the oxidative lesions occur. Lesions induced before and during replication primarily induce cell cycle delays and often drive the cells into a state of quiescence, whereas lesions arising after replication allow mitotic progression but compromise the proliferative capacity of daughter cells. Finally, in pre-tumorigenic cells, centromeric oxidative lesions lead to mitotic defects, aneuploidy, and whole-arm chromosome translocations. Collectively, we identify centromeres as cell cycle-sensitive DNA damage sensors and oxidative stress as a direct driver of centromere fragility and chromosome instability.