Promotion of DNA repair by nuclear IKKβ phosphorylation of ATM in response to genotoxic stimuli

Ataxia-telangiectasia mutated (ATM) is one of the key molecules involved in the cellular response to DNA damage. A portion of activated ATM is exported from the nucleus into the cytoplasm, where it activates the I kappa B kinase/nuclear factor kappa B (IKK/NF-kappa B) signaling pathway. It has been thought that activated IKK beta, which is a critical kinase for NF-kappa B activation, generally resides in the cytoplasm and phosphorylates cytoplasmic downstream molecules, such as IkB alpha. Here, we identified a new role for IKK beta during the response to DNA damage. ATM phosphorylation in response to alkylating agents consisted of two phases: the early phase (up to 3 h) and late phase (after 6 h). A portion of the activated IKK beta generated during the DNA damage response was found to translocate into the nucleus and directly phosphorylate ATM in the late phase. Furthermore, the phosphorylation of ATM by nuclear IKK beta was suggested to promote DNA repair. In parallel, activated IKK beta induced classical NF-kappa B activation and was involved in anti-apoptosis. Our findings define the function of IKK beta during the response to DNA damage, which promotes cell survival and DNA repair, and maintains cellular homeostasis. Oncogene (2013) 32, 1854-1862; doi: 10.1038/onc.2012.192; published online 21 May 2012