Schematic Representation of the regulatory network. Three modules are represented in corresponding dotted Box. I: ATM module. This module delineates ATM activation through both MRN mediated process and autophosphorylation. II: p53-MDM2 module. The tumor suppressor p53 participates in DNA breaks repair process in multiple ways and also induces PUMA expression which functions as 'input signals' to the downstream Bax activation switch. III: Bax activation switch module. Pro-apoptotic members of Bcl2 family termed 'BH3-only' proteins either dissociates Bax/Bak from the sequestration of anti-death members (enabler) or directly activates Bax/Bak (activator). PUMA serves as 'enabler' and is p53 inducible. PUMA functions as 'input' to the downstream Bax activation module. Dotted lines donate regulatory control and solid lines represent mass flow. Arrow means activation, horizontal bar means inhibition. 'Φ' donates degradation.