title: Ubiquitination of mammalian AP endonuclease (APE1) regulated by the p53-MDM2 signaling pathway.
abstract: 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.
authors.affiliation: Department of Otolaryngology, Stanley S Scott Cancer Center, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA.
authors.forename: C S
authors.initials: CS
authors.lastname: Busso
authors.forename: T
authors.initials: T
authors.lastname: Iwakuma
authors.forename: T
authors.initials: T
authors.lastname: Izumi
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004260:DNA Repair / Q000502:physiology; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000378:metabolism*; D045325:HCT116 Cells; D006801:Humans; D008322:Mammals / Q000378:metabolism; D051379:Mice; D041681:NIH 3T3 Cells; D051736:Proto-Oncogene Proteins c-mdm2 / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism / Q000502:physiology*; D054875:Ubiquitination / Q000235:genetics
chemical_list: D016159:Tumor Suppressor Protein p53; D051736:Proto-Oncogene Proteins c-mdm2; C085108:APEX1 protein, human; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase