Antitoxin component of a hybrid type II/IV toxin-antitoxin (TA) system. De-ADP-ribosylates DNA (probably) modified on thymidine by its cognate toxin DarT, which neutralizes the activity of cognate toxin DarT. an N-(ADP-alpha-D-ribosyl)-thymidine in DNA + H2O = a thymidine in DNA + ADP-D-ribose Forms a complex with cognate toxin DarT; this complex neutralizes the toxic effect of DarT. By DNA damage (mitomycin C) as well as by darT overexpression. Knock-down of darG expression leads to increased ADP-ribosylation of genomic DNA by DarT and induction of the DNA damage response including recA, dnaB and dnaE2; darT and darG are also induced. Belongs to the DarG ADP-ribosyl glycohydrolase family.