(Top, left) Irreversible mono-ADP-ribosylation of guanosine bases by pierisins, ScARP, Scabin and CARP-1. (Bottom, left) Mono-ADP-ribosylation of thymidine bases in ssDNA by the toxin DarT which is reversible by its antitoxin partner, DarG. (Top, right) Mono- and poly-ADP-ribosylation of the DNA backbone via terminal phosphate-linkage catalysed by PARP1–3. The modifications are reversible by macrodomain-containing proteins (PARG, TARG1, MacroD2) and ARH3. (Bottom, right) Mono-ADP-ribosylation of the RNA backbone via phosphate-linkage catalysed by PARP family members and TRPT1/TPT1/KptA. (ADPR: ADP-ribose; ADPr: ADP-ribosylated; Ⓟ: phosphate; TA: Toxin-Antitoxin system).