This subfamily includes four of the he best characterised enzymes (the PARylating PARPs) that catalyse the addition of poly-ADP-ribose chains as post-translational protein modifications: the nuclear enzymes PARP1, PARP2 and the tankyrases (TNKSs). PARPs 1 and 2 appear to function by binding to single strand breaks in DNA, allowing the recruitment of repair enzymes by the synthesis of NAD-derived ADP-ribose polymers, that are subsequently degraded by the glycohydrolase PARG. The most well defined function of the tankyrases (TNKSs) is their regulatory action on Wnt/β-catenin signalling [9]. PARPs 1 and 2 are targets of PARP inhibitor class anti-cancer drugs which are designed to disrupt the DNA damage response pathways to induce cancer cell death.
The catabolic enzyme poly(ADP-ribose) glycohydrolase (PARG) is also included in this section, as an important regulator of PARylation, and oncology drug target.

* Key recommended reading is highlighted with an asterisk

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