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PARG dysfunction enhances DNA double strand break formation in S-phase after alkylation DNA damage and augments

H Shirai1, A R Poetsch, A Gunji

  • 1Division of Genome Stability Research, National Cancer Center Research Institute, Tokyo, Japan.

Cell Death & Disease
|June 8, 2013
PubMed

Insights

Poly(ADP-ribose) glycohydrolase (PARG) deficiency enhances DNA damage and cell death in response to alkylating agents. PARG inhibition sensitizes cancer cells to DNA damage, suggesting a therapeutic strategy.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Cancer Research

Background:

  • Poly(ADP-ribose) glycohydrolase (PARG) degrades poly(ADP-ribose) (PAR).
  • PARG dysfunction is linked to increased sensitivity to DNA-damaging agents and cell death, but mechanisms are unclear.

Purpose of the Study:

  • To investigate how PARG deficiency causes cell death in response to alkylating agents.
  • To explore the role of p53 status and cell type in PARG-deficient cells treated with methylmethanesulfonate (MMS).

Main Methods:

  • Utilized Parg(-/-) mouse embryonic stem (ES) cells and human cancer cell lines (MIAPaCa2).
  • Treated cells with methylmethanesulfonate (MMS), a DNA alkylating agent.
  • Assessed DNA double-strand breaks (γ-H2AX), poly(ADP-ribose) accumulation, cell cycle arrest (S-phase), and cell death pathways (apoptosis, necrosis).
  • Performed PARG knockdown in a p53-defective cell line.

Main Results:

  • Parg(-/-) mouse ES cells exhibited increased DNA double-strand breaks (DSBs), PAR accumulation, p53 activation, S-phase arrest, and enhanced apoptosis.
  • PARG knockdown in p53-defective MIAPaCa2 cells sensitized them to MMS, inducing necrotic cell death with elevated γ-H2AX and S-phase arrest.
  • Cell death pathway (apoptosis vs. necrosis) was cell-type dependent.

Conclusions:

  • PARG deficiency-induced sensitization to alkylating agents is mediated by DSB repair defects and S-phase arrest, independent of p53 status.
  • The specific cell death pathway is determined by the cell type.
  • Inhibiting PARG may sensitize certain cancer cells to alkylating agents, offering a potential therapeutic approach.

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