Abstract SY11-03: Mechanisms of ATM activation

Abstract

Abstract The Ataxia-Telangiectasia Mutated (ATM) kinase initiates a rapid cascade of protein phosphorylation in response to double-strand breaks in chromosomal DNA. The critical targets of ATM during this response include many tumor suppressors involved in cell cycle progression and apoptosis. The DNA damage response is thus defective in cells lacking ATM; however, there are also many indications that cells lacking ATM are defective in responses to other forms of stress, particularly oxidative stress. Mammalian cells lacking ATM exhibit high levels of reactive oxygen species and indications of chronic oxidative stress. In addition, the shortened lifespan, haematopoietic stem cell loss, and increased lymphomagenesis seen in A-T mouse models can be suppressed by antioxidants, suggesting that oxidative stress constitutes an important part of the A-T phenotype and is important for cancer progression. We have observed robust ATM activation in human cell lines in response to oxidative stress, in the absence of apparent DNA damage. In addition, oxidation of purified recombinant ATM in vitro induces ATM activation in the absence of DNA DSBs and the MRN complex. The oxidized form of ATM is a disulfide-crosslinked dimer containing several disulfide bonds. Mutation of a critical cysteine residue involved in disulfide bond formation specifically blocks activation via the oxidation pathway, both in vitro with purified components and in human cells. Identification of this pathway explains many observations of ATM activation under conditions of oxidative stress, and shows that ATM is an important sensor of reactive oxygen species (ROS) in vivo. Here we investigate how the oxidation pathway of ATM activation is affected by small molecules, specifically by resveratrol and related compounds, and how this affects cell cycle checkpoint responses in human cells. We also show in vitro that ATM is a direct target of these compounds and investigate the mechanism underlying the effects on ATM function. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr SY11-03. doi:1538-7445.AM2012-SY11-03