“…Only a few of the PARPs (PARP1, 2, 5A, 5B) are capable of true polymerization (PARylation) while the majority, transfer only a single ADPr (Barkauskaite et al, 2015; Leung, 2014; Vyas & Chang, 2014) (MARylation) onto target molecules. For many years it was thought that ADPr transfer (MARylation and PARylation) occurred only on proteins via ester linkage at 7 amino acid residues (asparagine, aspartic acid, glutamic acid, arginine, lysine, serine, and cysteine) (Bonfiglio, Colby, & Matic, 2017; Daniels, Ong, & Leung, 2017; Palazzo et al, 2018; Vyas & Chang, 2014). However, recent studies now show MARylation and PARylation occurring on DNA (Munnur, Bartlett, et al, 2019; Munnur, Somers, et al, 2019; Talhaoui et al, 2016), RNA (Munnur, Bartlett, et al, 2019), antibiotics (reviewed in Palazzo, Mikoc, and Ahel (2017)), and other small molecules (Kirby & Cohen, 2019).…”