phosphorylated DNA breaks through an allosteric regulatory mechanism shared with PARP-1

PARP-1, PARP-2 and PARP-3 are DNA-dependent PARPs that localize to DNA damage, synthesize poly(ADP-ribose) (PAR) covalently attached to target proteins including themselves, and thereby recruit repair factors to DNA breaks to increase repair effi-ciency. PARP-1, PARP-2 and PARP-3 have in com-mon two C-terminal domains––Trp-Gly-Arg (WGR) and catalytic (CAT). In contrast, the N-terminal re-gion (NTR) of PARP-1 is over 500 residues and in-cludes four regulatory domains, whereas PARP-2 and PARP-3 have smaller NTRs (70 and 40 residues, re-spectively) of unknown structural composition and function. Here, we show that PARP-2 and PARP-3 are preferentially activated by DNA breaks harbor-ing a 5 ′ phosphate (5′P), suggesting selective acti-vation in response to specific DNA repair interme-diates, in particular structures that are competent for DNA ligation. In contrast to PARP-1, the NTRs of PARP-2 and PARP-3 are not strictly required for DNA binding or for DNA-dependent activation. Rather, the WGR domain is the central regulatory domain of PARP-2 and PARP-3. Finally, PARP-1, PARP-2 and PARP-3 share an allosteric regulatory mechanism of DNA-dependent catalytic activation through a local destabilization of the CAT. Collectively, our study pro-vides new insights into the specialization of the DNA-dependent PARPs and their specific roles in DNA re-pair pathways