Control of cell cycle-dependent degradation of c-Ski proto-oncoprotein by Cdc34

Mara Macdonald, Yong Wan, Wei Wang, Elisabeth Roberts, Hiu Cheung Tom, Richard Erickson, Matthew T. Knuesel, Xuedong Liu*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


It is known that excess amounts of Ski, or any member of its proto-oncoprotein family, causes disruption of the transforming growth factor beta signal transduction pathway, thus causing oncogenic transformation of cells. Previous studies indicate that Ski is a relatively unstable protein whose expression levels can be regulated by ubiquitin-mediated proteolysis. Here, we investigate the mechanism by which the stability of Ski is regulated. We show that the steady-state levels of Ski protein are controlled post-translationally by cell cycle-dependent proteolysis, wherein Ski is degraded during the interphase of the cell cycle but is relatively stable during mitosis. Furthermore, we demonstrate that the ubiquitin-conjugating enzyme Cdc34 mediates cell cycle-dependent Ski degradation both in vitro and in vivo. Overexpression of dominant-negative Cdc34 stabilizes Ski and enhances its abilty to antagonize TGF-β signaling. Our data suggest that regulated proteolysis of Ski is one of the key mechanisms that control the threshold levels of this proto-oncoprotein, and thus prevents epithelial cells from becoming TGF-β resistant.

Original languageEnglish (US)
Pages (from-to)5643-5653
Number of pages11
Issue number33
StatePublished - Jul 22 2004


  • Cdc34
  • Cell cycle
  • Protein degradation
  • Ski
  • SnoN
  • Ubiquitin

ASJC Scopus subject areas

  • Genetics
  • Molecular Biology
  • Cancer Research


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