ATR and Telangiectasia: Principal amongst these is DNA damage signalling via the phosphatidylinositol 3-kinase-like kinases (PI3KK), ATM (ataxia telangiectasia mutated) and ATR (ataxia telangiectasia and Rad3 related), which elicits a variety of cellular responses, including activation of DNA repair mechanisms, cell cycle arrest or apoptosis [4].