Transforming growth factor β facilitates β-TrCP-mediated degradation of Cdc25A in a Smad3-dependent manner

Dipankar Ray, Yasuhisa Terao, Dipali Nimbalkar, Li Hao Chu, Maddalena Donzelli, Tateki Tsutsui, Xianghong Zou, Asish K. Ghosh, John Varga, Giulio F. Draetta, Hiroaki Kiyokawa*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

47 Scopus citations


Ubiquitin-dependent degradation of Cdc25A is a major mechanism for damage-induced S-phase checkpoint. Two ubiquitin ligases, the Skp1-cullin-β-TrCP (SCFβ-TrCP) complex and the anaphase-promoting complex (APCCdh1), are involved in Cdc25A degradation. Here we demonstrate that the transforming growth factor β (TGF-β)-Smad3 pathway promotes SCFβ-TrCP-mediated Cdc25A ubiquitination. Cells treated with TGF-β, as well as cells transfected with Smad3 or a constitutively active type I TGF-β receptor, exhibit increased ubiquitination and markedly shortened half-lives of Cdc25A. Furthermore, Cdc25A is stabilized in cells transfected with Smad3 small interfering RNA (siRNA) and cells from Smad3-null mice. TGF-β-induced ubiquitination is associated with Cdc25A phosphorylation at the β-TrCP docking site (DS82G motif) and physical association of Cdc25A with Smad3 and β-TrCP. Cdc25A mutant proteins deficient in DS82G phosphorylation are resistant to TGF-β-Smad3-induced degradation, whereas a Cdc25A mutant protein defective in APCCdh1 recognition undergoes efficient degradation. Smad3 siRNA inhibits β-TrCP-Cdc25A interaction and Cdc25A degradation in response to TGF-β. β-TrCP2 siRNA also inhibits Smad3-induced Cdc25A degradation. In contrast, Cdh1 siRNA had no effect on Cdc25A down-regulation by Smad3. These data suggest that Smad3 plays a key role in the regulation of Cdc25A ubiquitination by SCFβ-TrCP and that Cdc25A stabilization observed in various cancers could be associated with defects in the TGF-β-Smad3 pathway.

Original languageEnglish (US)
Pages (from-to)3338-3347
Number of pages10
JournalMolecular and cellular biology
Issue number8
StatePublished - Apr 2005

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology


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