PARP1 and cancer: Similar to other PTMs, ADP-ribosylation has gained attention for its vital importance in cell homeostasis: The discovery of the role of PARP1 dependent poly-ADP-ribosylation (PARylation) in DNA single-strand break repair [2,3], and the following application of PARP inhibitors in the treatment of BRCA1/2 deficient cancers [4], have catalyzed a growing interest in PARylation research.