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The BRCT domain of PARP1 binds intact DNA and mediates intrastrand transfer

Johannes Rudolph1, Uma M Muthurajan1, Megan Palacio1

  • 1Department of Biochemistry, University of Colorado Boulder, Boulder, CO 80309, USA.

Molecular Cell
|December 17, 2021
PubMed

Insights

Poly(ADP-ribose) polymerase 1 (PARP1) binds intact DNA via its BRCT domain, a previously unrecognized interaction. This binding does not activate its catalytic function, revealing new insights into PARP1 regulation.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Structural Biology

Background:

  • Poly(ADP-ribose) polymerase 1 (PARP1) is crucial for DNA damage response and a cancer treatment target.
  • PARP1 activation by damaged DNA involves NAD+ and poly(ADP-ribose) chain synthesis.
  • PARP1 also binds intact DNA and chromatin but remains inactive.

Purpose of the Study:

  • To investigate the unrecognized DNA-binding role of the PARP1 BRCT domain.
  • To elucidate the structural basis of PARP1 interaction with intact DNA.
  • To understand how BRCT domain binding influences PARP1 activity and DNA transfer.

Main Methods:

  • Cryogenic electron microscopy (cryo-EM) to visualize BRCT domain-DNA complexes.
  • Biochemical assays to study protein-DNA interactions.
  • Sequence analysis to identify conserved functional motifs.

Main Results:

  • Intact DNA directly contacts the PARP1 BRCT domain, distinct from its catalytic function.
  • Cryo-EM reveals the BRCT domain bound to nucleosomal DNA.
  • A conserved motif in the BRCT domain mediates binding to DNA phosphates and phospho-peptides.
  • BRCT domain DNA binding contributes to the PARP1 'monkey-bar mechanism' for DNA transfer.

Conclusions:

  • The PARP1 BRCT domain is a novel DNA-binding module that interacts with intact DNA without activating catalysis.
  • Structural and biochemical data illuminate a new mode of PARP1-DNA interaction.
  • Understanding BRCT domain function offers new avenues for targeting PARP1 in cancer therapy.
Keywords:
BRCTDNA repairPARP1cryoEMintrastrand transfernucleosome

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