When HDAC8 inhibitor, PCI-34051 was administrated in A549, HepG2, U87 cancer cells, the radiation-induced changes of Kcr of Ku80 decreased and the corresponding SUMOylation increased were blocked, further indicating that HDAC8-mediated decrotonylation is necessary for the radiation-induced SUMOylation of Ku80 (Supplementary Fig 8a–f). The gene discussed is XRCC5; the disease is cancer.