PARP1 and cancer: For example, inhibitors of PARP1, which catalyzes the addition of poly- ADP-ribose marks, have been developed for treating tumors with mutations in either BRCA1 or BRCA2 (Lord and Ashworth 2017) and inhibitors of PARG, which catalyzes the removal of α(1′′−2′) O-glycosidic linkages in PAR chains, are under investigation for a variety of cancers (Slade 2020).