O-GlcNAc modification affects the ATM-mediated DNA damage response

► O-GlcNAcylation was involved in the DNA damage responses to X-irradiation. ► Activation and recovery of ATM were affected by dynamic O-GlcNAc modifications. ► ATM was subject to O-GlcNAcylation and interacted with O-GlcNAc transferase. ► O-GlcNAcylation may regulate the dissociation of PP2A, a process for ATM activation.