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

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Poly(ADP-ribose)polymerase 2 (PARP2) is a nuclear protein involved in DNA damage sensing.
• PARP2's interaction with nucleosomes is crucial but not fully understood.
• Identifying factors that regulate PARP2-nucleosome binding is key for anti-cancer drug development.

Purpose of the Study:

• To investigate the role of divalent metal ions (Mg2+, Ca2+, Zn2+) in modulating PARP2 binding to nucleosomes.
• To elucidate the structural mechanisms underlying ion-mediated PARP2-nucleosome interactions.
• To determine how metal ions affect PARP2's auto(poly-ADP-ribosylation) activity.

Main Methods:

• Biochemical assays to study PARP2-nucleosome complex formation in the presence of different cations.
• Spectroscopic techniques (e.g., circular dichroism) to assess conformational changes in PARP2 and nucleosomal DNA.
• Site-directed mutagenesis to identify key residues and domains involved in metal ion binding and structural reorganization.

Main Results:

• Mg2+ and Ca2+ ions facilitate PARP2 binding to nucleosomes without altering DNA conformation.
• Zn2+ ions induce local structural changes in PARP2, specifically within the WGR domain, leading to nucleosome reorganization.
• Zn2+ binding to the WGR domain's putative sites modulates PARP2 auto(poly-ADP-ribosylation) activity, with effects dependent on site occupancy.
• PARP2-nucleosome interactions and structural reorganization are reversible upon changes in Zn2+ concentration.

Conclusions:

• Divalent metal ions, particularly Zn2+, play a critical role in regulating PARP2-nucleosome interactions and structural dynamics.
• The WGR domain of PARP2 is a key mediator of Zn2+-induced structural changes.
• Transient changes in cation concentrations can finely tune PARP2 activity and chromatin structure, impacting DNA damage response pathways.