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Phosphorylation of Rad9 at serine 328 by cyclin A-Cdk2 triggers apoptosis via interfering Bcl-xL

Zhuo Zhan1, Kan He, Dan Zhu

  • 1Key Laboratory for Molecular Enzymology and Engineering of the Ministry of Education, College of Life Science, Jilin University, Changchun, China.

Plos One
|October 3, 2012
PubMed

Insights

Cyclin A-Cdk2 phosphorylates the apoptosis regulator Rad9, promoting its interaction with Bcl-xL and initiating cell death. This mechanism clarifies how cyclin A-Cdk2 controls apoptosis via Rad9 phosphorylation.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Cyclin A-Cdk2 is a key cell cycle kinase involved in apoptosis.
  • The precise mechanism of cyclin A-Cdk2-mediated apoptosis is not fully understood.

Purpose of the Study:

  • To elucidate the role of cyclin A-Cdk2 in regulating apoptosis.
  • To investigate the interaction between cyclin A-Cdk2 and the Bcl-2 family protein Rad9.

Main Methods:

  • In vitro and in vivo phosphorylation assays of Rad9 by cyclin A-Cdk2.
  • Etoposide-induced apoptosis in HeLa cells.
  • Analysis of Rad9 translocation and interaction with Bcl-xL.
  • Overexpression studies of cyclin A and Rad9 mutants (Rad9S328A).

Main Results:

  • Cyclin A-Cdk2 phosphorylates Rad9 at serine 328 during etoposide-induced apoptosis.
  • Phosphorylated Rad9 translocates from the nucleus to mitochondria and interacts with Bcl-xL.
  • Forced activation of cyclin A-Cdk2 enhances Rad9-Bcl-xL interaction and apoptosis.
  • A Rad9 mutant resistant to phosphorylation (Rad9S328A) reduces these pro-apoptotic effects.

Conclusions:

  • Cyclin A-Cdk2 regulates apoptosis by phosphorylating Rad9 at serine 328.
  • Rad9 phosphorylation by cyclin A-Cdk2 is a critical step for its mitochondrial translocation and interaction with Bcl-xL, initiating the apoptotic cascade.

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