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The oncoprotein gankyrin binds to MDM2/HDM2, enhancing ubiquitylation and degradation of p53.


Gankyrin is an ankyrin repeat oncoprotein commonly overexpressed in hepatocellular carcinomas. Gankyrin interacts with the S6 proteasomal ATPase and accelerates the degradation of the tumor suppressor Rb. We show here that gankyrin has an antiapoptotic activity in cells exposed to DNA damaging agents. Downregulation of gankyrin induces apoptosis in cells with wild-type p53. In vitro and in vivo experiments revealed that gankyrin binds to Mdm2, facilitating p53-Mdm2 binding, and increases ubiquitylation and degradation of p53. Gankyrin also enhances Mdm2 autoubiquitylation in the absence of p53. Downregulation of gankyrin reduced amounts of Mdm2 and p53 associated with the 26S proteasome. Thus, gankyrin is a cofactor that increases the activities of Mdm2 on p53 and probably targets polyubiquitylated p53 into the 26S proteasome.

Pubmed ID: 16023600


  • Higashitsuji H
  • Higashitsuji H
  • Itoh K
  • Sakurai T
  • Nagao T
  • Sumitomo Y
  • Sumitomo H
  • Masuda T
  • Dawson S
  • Shimada Y
  • Mayer RJ
  • Fujita J


Cancer cell

Publication Data

July 18, 2005

Associated Grants


Mesh Terms

  • Animals
  • Ankyrins
  • Apoptosis
  • Cells, Cultured
  • Gene Expression Regulation
  • Humans
  • Immunoprecipitation
  • Mice
  • Molecular Sequence Data
  • Neoplasms
  • Nuclear Proteins
  • Proteasome Endopeptidase Complex
  • Proteasome Inhibitors
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-mdm2
  • RNA, Small Interfering
  • Retinoblastoma Protein
  • Tumor Suppressor Protein p53
  • Zinc Fingers