DNA strand breaks at centromeres: Friend or foe?

RAD52-mediated repair of DNA double-stranded breaks at inactive centromeres leads to subsequent apoptotic cell death

Centromeres, where the kinetochore complex binds, are susceptible to damages including DNA double-stranded breaks (DSBs). Here, we report the functional significance and the temporally and spatially distinct regulation of centromeric DSB repair via the three pathways of non-homologous end joining (NHEJ), homologous recombination (HR) and single-strand annealing (SSA). The SSA factor RAD52 is most frequently recruited to centromeric DSB sites compared with the HR factor RAD51 and the NHEJ factor DNA ligase IV (LIG4), indicating that SSA plays predominant roles in centromeric DSB repair. Upon centromeric DSB induction, LIG4 is recruited to both active centromeres, where kinetochore complex binds, and inactive centromeres. In contrast, RAD51 and RAD52 are recruited only to inactive centromeres. These results indicate that DSBs at active centromeres are repaired through NHEJ, whereas the three pathways of NHEJ, HR and SSA are involved in DSB repair at inactive centromeres. Furthermore, siRNA-mediated depletion of either LIG4 or RAD51 promotes cell death after centromeric DSB induction, whereas RAD52 depletion inhibits it, suggesting that HR and NHEJ are required for appropriate centromeric DSB repair, whereas SSA-mediated centromeric DSB repair leads to subsequent cell death. Thus, SSA-mediated DSB repair at inactive centromeres may cause centromere dysfunction through error-prone repair.