Ubiquitination of mammalian AP endonuclease (APE1) regulated by the p53-MDM2 signaling pathway

C. S. Busso, T. Iwakuma, T. Izumi

Research output: Contribution to journalArticlepeer-review

86 Scopus citations


APE1/Ref-1 is an essential DNA repair/gene regulatory protein in mammals of which intracellular level significantly affects cellular sensitivity to genotoxicants. The apurinic/apyrimidinic endonuclease 1 (APE1) functions are altered by phosphorylation and acetylation. We here report that APE1 is also modified by ubiquitination. APE1 ubiquitination occurred specifically at Lys residues near the N-terminus, and was markedly enhanced by mouse double minute 2 (MDM2), the major intracellular p53 inhibitor. Moreover, DNA-damaging reagents and nutlin-3, an inhibitor of MDM2-p53 interaction, increased APE1 ubiquitination in the presence of p53. Downmodulation of MDM2 increased APE1 level, suggesting that MDM2-mediated ubiquitination can be a signal for APE1 degradation. In addition, unlike the wild-type APE1, ubiquitin-APE1 fusion proteins were predominantly present in the cytoplasm. Therefore, monoubiquitination not only is a prerequisite for degradation, but may also alter the APE1 activities in cells. These results reveal a novel regulation of APE1 through ubiquitination.

Original languageEnglish
Pages (from-to)1616-1625
Number of pages10
Issue number13
StatePublished - Apr 2 2009

Bibliographical note

Funding Information:
We thank KA Kerlec, KM Lane, MW Lake, MK Rogoszewicz and C Bulkin for their technical assistance, and Mr Lake for editorial help. We also thank Dr S Desai and Dr A Haas at LSUHSC, New Orleans for their critical discussion and experimental guidance. Dr Davis’s excellent editorial help is much appreciated. This research was supported by NCI grant CA98664 (TI) and Louisiana Cancer Research Consortium funding.


  • APE1
  • DNA damage
  • DNA repair
  • MDM2
  • P53
  • Ubiquitination

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Cancer Research


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