Possible role of PARP in cell death in the event of DNA damage caused by ROS or a genotoxin, PARP targets the damaged site. If high damage occurs, PARP may become overactivated resulting in ATP/NAD depletion and necrosis. Apoptosis can also occur through caspase-3 activation and PARP cleavage. If low damage occurs, PARP can recruit other repair enzymes and DNA repair can occur. Recently PARP1 dependent cell death termed as parthanatos has been reported, and is distinct from apoptosis, necrosis or autophagy. Each arrow represents one or more reaction(s).