Poly(ADP-ribose)polymerase 2 is zinc-dependent enzyme and nucleosome reorganizer

Poly(ADP-ribose)polymerase 2 (PARP2) is a nuclear protein, DNA damage sensor and an emerging target for development of anti-cancer drugs. Previously it was discovered that PARP2 binds to nucleosomes; however, critical factors involved in this process remain unknown. We demonstrated that in the presence of Mg²⁺ or Ca²⁺ ions PARP2 forms complexes with a nucleosome containing different number of PARP2 molecules without altering conformation of nucleosomal DNA. In contrast, Zn²⁺ ions directly interact with PARP2 inducing a local alteration of the secondary structure of the protein and PARP2-mediated, reversible structural reorganization of nucleosomes. WGR domain of PARP2 is the target for Zn²⁺ ions since this domain contains two putative Zn^2+-binding sites, binds Zn²⁺ ions and alone drives Zn²⁺-mediated reorganization of nucleosomes. Auto(poly-ADP-ribosylation) activity of PARP2 is enhanced by Mg²⁺ ions and modulated by Zn²⁺ ions: suppressed or enhanced depending on the occupancy of two functionally different zinc binding sites. The data suggest that transient changes in concentration of cations can differentially modulate PARP2 activity, local chromatin structure and the DNA damage response.