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Efficient activity of uracil DNA glycosylase (UNG2) in proliferating cells requires binding to proliferating cell

Rashmi S Kulkarni1, Brian P Weiser1

  • 1Department of Cell & Molecular Biology, Rowan-Virtua School of Osteopathic Medicine, Rowan University, Stratford, NJ 08084, United States; Department of Cell & Molecular Biology, Rowan-Virtua School of Translational Biomedical Engineering & Sciences, Rowan University, Stratford, NJ 08084, United States.

DNA Repair
|December 30, 2025
PubMed

Insights

Cancer drugs pemetrexed and 5-fluorodeoxyuridine (FdU) effectiveness increases when uracil DNA glycosylase (UNG2) interaction with PCNA and RPA is blocked. This impairs DNA repair, sensitizing cancer cells to these therapies.

Area of Science:

  • Molecular Biology
  • Cancer Research
  • DNA Repair Mechanisms

Background:

  • Pemetrexed and 5-fluorodeoxyuridine (FdU) are chemotherapy agents that induce DNA damage and replication stress.
  • These drugs disrupt pyrimidine metabolism, leading to uracil accumulation in genomic DNA.
  • Uracil DNA glycosylase (UNG2) repairs uracil in DNA and interacts with Proliferating Cell Nuclear Antigen (PCNA) and Replication Protein A (RPA) at replication forks.

Purpose of the Study:

  • To investigate whether UNG2 requires interaction with PCNA and RPA for DNA repair during pemetrexed or FdU treatment in colorectal cancer cells.
  • To determine if disrupting UNG2's interaction with PCNA or RPA affects its function and cellular response to these drugs.

Main Methods:

  • Genetically knocked out UNG2 in HT29 colorectal cancer cells.
  • Engineered cells to express UNG2 variants unable to bind PCNA or RPA.
  • Assessed cellular sensitivity to pemetrexed and FdU.
  • Examined UNG2 localization to stalled replication forks.

Main Results:

  • Eliminating UNG2 activity or disrupting its interaction with PCNA/RPA sensitized cells to pemetrexed and FdU.
  • UNG2's localization to stalled replication forks was impaired when PCNA/RPA binding was disrupted.
  • Disrupting UNG2-PCNA or UNG2-RPA interactions increased cellular sensitivity to the drugs' cytotoxic effects.

Conclusions:

  • UNG2's interaction with PCNA and RPA is crucial for its function in repairing DNA damage induced by pemetrexed and FdU.
  • Cancer cells can be sensitized to pemetrexed and FdU by inhibiting UNG2 activity, depleting its levels, or blocking its protein-protein interactions.
Keywords:
5-fluorodeoxyuridineBase excision repairPCNAPemetrexedReplication protein AUracil DNA glycosylase

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