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JNK-mediated phosphorylation of Cdc25C regulates cell cycle entry and G(2)/M DNA damage checkpoint

Gustavo J Gutierrez1, Toshiya Tsuji, Janet V Cross

  • 1Signal Transduction Program, Cancer Center, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037, USA.

The Journal of Biological Chemistry
|March 12, 2010
PubMed

Insights

c-Jun NH(2)-terminal Kinases (JNKs) regulate the cell cycle by phosphorylating Cdc25C, controlling mitosis onset. JNK-mediated Cdc25C phosphorylation is crucial for the UV-induced G(2)/M checkpoint and stress signaling.

Area of Science:

  • Cellular Biology
  • Molecular Biology
  • Biochemistry

Background:

  • c-Jun NH(2)-terminal Kinases (JNKs) are key mediators of cellular stress responses, influencing proliferation, migration, survival, and differentiation.
  • The role of JNKs in cell cycle control is increasingly recognized but remains incompletely understood.
  • Specific mechanisms linking JNK signaling to cell cycle regulation require further elucidation.

Purpose of the Study:

  • To investigate the direct role and mechanism of JNK in regulating cell cycle progression.
  • To identify specific JNK substrates involved in cell cycle control.
  • To determine the involvement of JNK-mediated phosphorylation in checkpoint activation.

Main Methods:

  • Cell-based assays to study JNK activity and substrate phosphorylation.
  • Site-directed mutagenesis to identify phosphorylation sites on Cdc25C.
  • Analysis of cell cycle progression following JNK activation or inhibition.
  • Investigation of UV-induced G(2)/M checkpoint activation.

Main Results:

  • JNK directly phosphorylates Cdc25C at serine 168 during the G(2) phase of the cell cycle.
  • JNK-mediated phosphorylation of Cdc25C inhibits its phosphatase activity, delaying Cdk1 activation and controlling mitosis.
  • Aberrant JNK activity or Cdc25C phosphorylation leads to cell cycle progression defects and is observed in some human tumors.
  • JNK phosphorylation of Cdc25C is essential for the UV irradiation-induced G(2)/M checkpoint.

Conclusions:

  • JNK directly phosphorylates Cdc25C, establishing a novel regulatory link between stress signaling and cell cycle control.
  • This phosphorylation event is critical for timely mitosis and checkpoint activation.
  • Dysregulation of JNK-Cdc25C interaction contributes to aberrant cell cycle progression and may be implicated in tumorigenesis.

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