Figure 1.
Diagram representing the activity of ADP-ribosylation and consequences.
DNA-damaging stimuli (oxido-nitrosative stress) cause poly(ADP-ribose) polymerase (PARP) activation. Activated PARP cleaves nicotinamide adenine dinucleo tide (NAD) into nicotinamide and ADP-ribose and polymerizes the latter on nuclear-acceptor proteins. Poly(ADP-ribosylation) facilitates DNA repair and thus permits cell survival. Severe DNA damage, however, leads to overactivation of PARP, resulting in NAD and ATP depletion and necrotic cell death.