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PARP-2 and PARP-3 are selectively activated by 5' phosphorylated DNA breaks through an allosteric regulatory

Marie-France Langelier1, Amanda A Riccio1, John M Pascal2

  • 1Department of Biochemistry & Molecular Biology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA 19107, USA.

Nucleic Acids Research
|June 15, 2014
PubMed

Insights

Poly(ADP-ribose) polymerases (PARP-1, PARP-2, PARP-3) are crucial for DNA repair. This study reveals PARP-2 and PARP-3 are activated by specific DNA breaks, highlighting their specialized roles in DNA damage response.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Genetics

Background:

  • Poly(ADP-ribose) polymerases (PARP-1, PARP-2, PARP-3) are key enzymes in DNA repair pathways.
  • These enzymes synthesize poly(ADP-ribose) (PAR) at DNA damage sites, recruiting repair factors.
  • PARP-1 possesses a large N-terminal region (NTR) with regulatory domains, unlike the smaller NTRs of PARP-2 and PARP-3.

Purpose of the Study:

  • To investigate the specific activation mechanisms and regulatory domains of PARP-2 and PARP-3.
  • To compare the functional roles of PARP-1, PARP-2, and PARP-3 in DNA repair.
  • To elucidate the structural and functional specialization among DNA-dependent PARPs.

Main Methods:

  • Biochemical assays to assess DNA binding and catalytic activity.
  • Site-directed mutagenesis to investigate the role of different protein domains (NTR, WGR, CAT).
  • Analysis of PARP activation in response to various DNA break structures.

Main Results:

  • PARP-2 and PARP-3 are preferentially activated by DNA breaks with a 5' phosphate group, indicating specific roles in DNA ligation intermediates.
  • The N-terminal regions of PARP-2 and PARP-3 are not essential for DNA binding or activation, unlike PARP-1.
  • The Trp-Gly-Arg (WGR) domain is identified as the central regulatory domain for PARP-2 and PARP-3.
  • All three PARPs (PARP-1, PARP-2, PARP-3) share an allosteric mechanism for DNA-dependent activation via catalytic (CAT) domain destabilization.

Conclusions:

  • PARP-2 and PARP-3 exhibit distinct activation specificities, suggesting specialized functions in DNA repair beyond PARP-1.
  • The WGR domain plays a critical regulatory role in PARP-2 and PARP-3 function.
  • Shared allosteric regulation highlights conserved mechanisms in DNA-dependent PARP activation, despite domain differences.

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