Ataxia Telangiectasia Mutated (ATM) is a serine/threonine protein kinase that is the master regulator of the DNA double-strand break (DSB) repair pathway. ATM is a key part of the cell cycle machinery that activates checkpoint signaling in response to DSBs, apoptosis, and genotoxic insults. ATM normally exists in its inactive state as a dimer or tetramer - upon DNA damage, it dissociates into monomers triggered by its own autophosphorylation.
