PARP Poly(ADP-ribose) polymerase. Any of a group of enzymes (five have been identified—PARP1–5) whose prototypic member (PARP1) is encoded by PARP1 on chromosome 1q41-q42. PARP1 detects and repairs single strand breaks in chromosomal DNA, and plays a key role in initiating DNA repair. High levels of PARP1 are associated with increased apoptosis in response to genotoxic stress, and it may act downstream of the Raf-MEK-ERK pathway through direct interaction with ERK2 in the nucleus, repairing DNA damage. PARP inhibitors are being explored as therapies for cancer, diabetes, stroke and cardiovascular disease.