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SCF(Fbxw7/hCdc4) targets cyclin E2 for ubiquitin-dependent proteolysis

Kathleen Klotz1, Diana Cepeda, Yingmeei Tan

  • 1Sidney Kimmel Cancer Center, 10905 Road to the Cure, San Diego, CA 92121, USA.

Experimental Cell Research
|December 17, 2008
PubMed

Insights

Cyclin E2 is degraded by the SCF(Fbxw7/hCdc4) ubiquitin ligase, a process crucial for cell cycle regulation. This pathway

Area of Science:

  • Cell Biology
  • Molecular Oncology
  • Protein Degradation

Background:

  • E-type cyclins (E1 and E2) are key regulators of the S phase in the cell division cycle.
  • Deregulation of cyclin E1 and E2 expression is common in various cancers, indicating an oncogenic role.
  • While cyclin E1 deregulation mechanisms are understood, those for cyclin E2 remain largely unknown.

Purpose of the Study:

  • To elucidate the molecular mechanisms governing cyclin E2 regulation and degradation.
  • To investigate the role of ubiquitin-dependent proteolysis in controlling cyclin E2 levels.
  • To explore potential cross-talk between cyclin E1 and cyclin E2 regulation.

Main Methods:

  • Investigated the targeting of cyclin E2 by the ubiquitin ligase SCF(Fbxw7/hCdc4).
  • Analyzed the role of specific phosphorylation sites (Thr392, Ser396, Thr74) in triggering ubiquitylation.
  • Examined the effect of ectopic cyclin E1 expression on cyclin E2 proteolysis in vivo.

Main Results:

  • Cyclin E2 is specifically targeted for ubiquitin-dependent proteolysis by the SCF(Fbxw7/hCdc4) complex.
  • Phosphorylation of cyclin E2 at Thr392 and Ser396 sites initiates its ubiquitylation and degradation.
  • Ectopic expression of cyclin E1 enhances cyclin E2 proteolysis, suggesting regulatory cross-talk.

Conclusions:

  • The SCF(Fbxw7/hCdc4) ligase controls cyclin E2 stability through phosphorylation-dependent degradation.
  • This pathway represents a novel mechanism for regulating E-type cyclin activity.
  • Functional inactivation of SCF(Fbxw7/hCdc4) in cancers may contribute to cyclin E2 deregulation and tumorigenesis.

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