Genomically incorporated 5-fluorouracil that escapes ung-initiated base excision repair blocks dna replication and activates homologous recombination

Amelia M. Huehls, Catherine J. Huntoon, Poorval M. Joshi, Carly A. Baehr, Jill M. Wagner, Xiaoxiao Wang, Marietta Y. Lee, Larry M. Karnitz

Research output: Contribution to journalArticle

18 Scopus citations

Abstract

5-Fluorouracil (5-FU) and its metabolite 5-fluorodeoxyuridine (FdUrd, floxuridine) are chemotherapy agents that are converted to 5-fluorodeoxyuridine monophosphate (FdUMP) and 5-fluorodeoxyuridine triphosphate (FdUTP). FdUMP inhibits thymidylate synthase and causes the accumulation of uracil in the genome, whereas FdUTP is incorporated by DNA polymerases as 5-FU in the genome; however, it remains unclear how either genomically incorporated U or 5-FU contributes to killing. We show that depletion of the uracil DNA glycosylase (UNG) sensitizes tumor cells to FdUrd. Furthermore, we show that UNG depletion does not sensitize cells to the thymidylate synthase inhibitor (raltitrexed), which induces uracil but not 5-FU accumulation, thus indicating that genomically incorporated 5-FU plays a major role in the antineoplastic effects of FdUrd. We also show that 5-FU metabolites do not block the first round of DNA synthesis but instead arrest cells at the G1/S border when cells again attempt replication and activate homologous recombination (HR). This arrest is not due to 5-FU lesions blocking DNA polymerase d but instead depends, in part, on the thymine DNA glycosylase. Consistent with the activation of HR repair, disruption of HR sensitized cells to FdUrd, especially when UNG was disabled. These results show that 5-FU lesions that escape UNG repair activate HR, which promotes cell survival.

Original languageEnglish (US)
Pages (from-to)53-62
Number of pages10
JournalMolecular pharmacology
Volume89
Issue number1
DOIs
StatePublished - Jan 1 2016

ASJC Scopus subject areas

  • Molecular Medicine
  • Pharmacology

Fingerprint Dive into the research topics of 'Genomically incorporated 5-fluorouracil that escapes ung-initiated base excision repair blocks dna replication and activates homologous recombination'. Together they form a unique fingerprint.

  • Cite this