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Transcription-replication conflicts underlie sensitivity to PARP inhibitors

Michalis Petropoulos1, Angeliki Karamichali1, Giacomo G Rossetti2

  • 1Department of Molecular and Cellular Biology, University of Geneva, Geneva, Switzerland.

Nature
|March 21, 2024
PubMed

Insights

Poly(ADP-ribose) polymerase (PARP) inhibitors combat homologous recombination (HR)-deficient cancers by protecting the replisome. Their efficacy stems from repairing DNA damage during transcription-replication conflicts, not solely from trapping PARPs.

Area of Science:

  • Molecular Biology
  • Cancer Therapeutics
  • Genetics

Background:

  • Poly(ADP-ribose) polymerase (PARP) inhibitors are crucial for treating homologous recombination (HR)-deficient cancers.
  • PARP inhibitors are believed to trap PARPs on DNA, blocking replication and causing DNA double-strand breaks that necessitate HR for repair.

Purpose of the Study:

  • To investigate the precise mechanism underlying the synthetic lethality of PARP inhibitors in HR-deficient cancers.
  • To elucidate the role of PARP1, TIMELESS, and TIPIN in protecting the replication machinery.

Main Methods:

  • Investigated the interaction of PARP1 with TIMELESS and TIPIN in early S phase.
  • Analyzed the impact of inhibiting transcription elongation on PARP inhibitor sensitivity in HR-deficient cells.
  • Utilized small-interfering RNA to deplete PARP1 and assess its effect on HR-deficient cells.

Main Results:

  • PARP1, TIMELESS, and TIPIN collaborate to shield the replisome from transcription-replication conflicts in early S phase.
  • The synthetic lethality observed with PARP inhibitors in HR-deficient cells is attributed to unrepaired DNA damage from transcription-replication conflicts.
  • Inhibiting transcription elongation rendered HR-deficient cells resistant to PARP inhibitors, and PARP1 depletion showed synthetic lethality with HR deficiency.

Conclusions:

  • The therapeutic effect of PARP inhibitors in HR-deficient cancers may be achieved by targeting PARP1's enzymatic activity alone.
  • Understanding the role of PARP1 in DNA repair during replication stress is critical for optimizing cancer therapy.

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