Our DNA is constantly exposed to damaging factors that can lead to aging and age-related diseases such as cancer. PARP1 is an important enzyme that facilitates the response to DNA damage by attaching chemical groups called ADP-ribose to proteins. Published in Molecular Cell, a new study by the Matic group at the Max Planck Institute for the Biology of Ageing has discovered a second, slower wave of PARP1 activity that regulates DNA repair in a more gradual way.