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Replication-dependent cytotoxicity and Spartan-mediated repair of trapped PARP1-DNA complexes

Liton Kumar Saha1, Yasuhisa Murai1, Sourav Saha1

  • 1Developmental Therapeutics Branch & Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892, USA.

Nucleic Acids Research
|September 22, 2021
PubMed

Insights

Spartan (SPRTN) protein aids in repairing poly(ADP-ribose) polymerase 1 (PARP1)-DNA complexes during replication. SPRTN deficiency increases sensitivity to PARP inhibitors like talazoparib, highlighting SPRTN

Area of Science:

  • Molecular Biology
  • Genetics
  • Cancer Research

Background:

  • Poly(ADP-ribose) polymerase inhibitors (PARPis) exert antitumor effects through PARP trapping, forming DNA-protein complexes.
  • The precise mechanism of cytotoxicity for PARPis like talazoparib and olaparib is linked to DNA replication.

Purpose of the Study:

  • To investigate the role of Spartan (SPRTN) metalloprotease in repairing PARP1-DNA complexes during DNA replication.
  • To understand SPRTN's function in cellular response to PARP inhibitors.

Main Methods:

  • Utilized human TK6 and chicken DT40 lymphoblastoid cells, including SPRTN-deficient variants.
  • Analyzed cell sensitivity to PARP inhibitors (talazoparib, olaparib, veliparib).
  • Assessed PARP1-DNA complex clearance, replication fork stalling, and SPRTN localization via immunofluorescence and co-localization studies.

Main Results:

  • SPRTN-deficient cells showed hypersensitivity to talazoparib and olaparib, but not veliparib.
  • Delayed clearance of trapped PARP1 and increased replication fork stalling were observed in SPRTN-deficient cells.
  • SPRTN interacts with PARP1, forms nuclear foci colocalizing with CDC45 during S-phase, and is epistatic with translesion synthesis (TLS).

Conclusions:

  • SPRTN plays a crucial role in resolving PARP1-DNA complexes that stall replication forks.
  • SPRTN facilitates the excision and bypass of PARP1-DNA complexes during S-phase, contributing to cell survival under PARPi treatment.
  • These findings elucidate a novel DNA repair pathway involving SPRTN in response to replication-associated PARP trapping.

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