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Parp1 activation in mouse embryonic fibroblasts promotes Pol beta-dependent cellular hypersensitivity to alkylation

Elena Jelezcova1, Ram N Trivedi, Xiao-Hong Wang

  • 1Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine & University of Pittsburgh Cancer Institute, Hillman Cancer Center, Pittsburgh, PA 15213, USA.

Mutation Research
|January 26, 2010
PubMed

Insights

DNA polymerase beta (Pol beta) deficiency increases sensitivity to DNA damaging agents. Poly (ADP-ribose) polymerase 1 (Parp1) activation mediates this sensitivity, suggesting Parp1’s role in DNA repair and tumor suppression.

Area of Science:

  • DNA repair mechanisms
  • Cellular response to DNA damage
  • Cancer genomics

Background:

  • Alkylating agents cause cell death via apoptosis, autophagy, and necrosis.
  • DNA polymerase beta (Pol beta) knockout (KO) mouse embryonic fibroblasts (MEFs) show increased sensitivity to alkylating agents compared to wild-type (WT) MEFs.

Purpose of the Study:

  • To investigate the hypothesis that Parp1 is preferentially activated by methyl methanesulfonate (MMS) in Pol beta KO MEFs.
  • To examine the relationship between Pol beta expression, Parp1 activation, and cell survival following MMS exposure.

Main Methods:

  • Comparison of WT and Pol beta deficient MEF cell lines.
  • Assessment of Parp1 activation and cytotoxicity following MMS exposure.
  • Utilized Parp1/Parp2 inhibitor PJ34 and Pol beta knockdown (KD).
  • Generated Pol beta/Parp1 double KO MEFs.

Main Results:

  • Pol beta KO MEFs exhibited elevated Parp1 activation compared to WT MEFs.
  • Parp1 inhibition (PJ34) attenuated MMS-induced Parp1 activation and cytotoxicity in Pol beta KO MEFs.
  • Pol beta KD MEFs showed hypersensitivity to MMS, which was prevented by PJ34.
  • MMS-induced sensitivity in Pol beta KO MEFs was reversed in Pol beta/Parp1 double KO MEFs.

Conclusions:

  • Parp1 activation is significantly elevated in Pol beta deficient cells upon MMS exposure.
  • Parp1 inhibition or deletion mitigates the hypersensitivity to MMS in Pol beta deficient cells.
  • Parp1 may act as a sensor for base excision repair (BER) pathway failures, initiating cell death to prevent chromosomal damage and acting as a tumor suppressor.

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