Regulation of DNA damage-induced ATM activation by histone modifications

Ataxia-telangiectasia mutated (ATM) is an apical kinase involved in the cellular response to DNA damage in eukaryotes, especially DNA double-strand breaks (DSBs). Upon DSB, ATM is activated through a hierarchy of well-organized cellular processes and machineries, including post-translational modifications (PTMs), the MRE11-RAD50-NBS1 (MRN) complex and chromatin perturbations. ATM activation initiates a cascade of chromatin modifications and nucleosome remodeling that permits the assembly of repair factors that ensure a highly orchestrated response to repair damaged DNA. Numerous studies have tried to elucidate the mechanisms of ATM activation, but how it is activated by DNA damage signals is still unclear. Histone modifications are considered essential for regulating ATM activation: a histone octamer constitutes the nucleosome core and histone tails protrude into the DNA strands to alter the chromatin landscape and DNA accessibility. Here, we summarize how histone modifications regulate ATM activation, with an emphasis on the functional relevance in DNA damage response and repair.