Abstract
Double strand breaks (DSBs) occur in mammalian chromosomal DNA as a result of exposure of cells to ionizing radiation (IR). DSBs induce cellular responses that lead to cell cycle checkpoint, DNA repair, and apoptosis. Ataxia telangiectasia mutated (ATM) is a central kinase in these responses. Upon indction of DSBs, ATM phosphorylates various proteins involved in cell cycle checkpoint, DNA repair, and apoptosis, such as Nbs1, 53BP1, p53 and ATM itself. To identify a new ATM target protein, we performed 2D electorophoresis analysis. Cell lysates from IR-exposed or control cells were resolved by 2D electorophoresis. Proteins were transfered to a nylon membran, and subjected to immunobloting analyses with antibody specific to the phosphorylated form of Nbs1, 53BP1, or ATM. We identified a protein that is cross-reactive to anti-phospho ATM specific antibody. The phosphorylation of this protein was completely dependent on exposure of cells to IR, suggesting that this protein is a participant of cellular responses to IR. We also used antibody specific to mono-, or poly-ubiqutinated proteins in our 2D electorophoresis analysis. We will present recent results of the 2D electorophoresis analysis.
