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Bcl-xL phosphorylation at Ser49 by polo kinase 3 during cell cycle progression and checkpoints

Jianfang Wang1, Myriam Beauchemin, Richard Bertrand

  • 1Centre de recherche, Centre hospitalier de l'Université de Montréal (CRCHUM), Hôpital Notre-Dame and Institut du cancer de Montréal, Montréal, Québec, Canada.

Cellular Signalling
|August 16, 2011
PubMed

Insights

Phosphorylation of Bcl-xL at Ser49 by PLK3 stabilizes the G2 DNA damage checkpoint. This phosphorylation is crucial for timely cell division and mitotic exit, impacting cytokinesis.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Bcl-xL is a key regulator of apoptosis.
  • Cell cycle progression is tightly controlled by checkpoints and regulatory proteins.
  • Phosphorylation of proteins can alter their function and localization.

Purpose of the Study:

  • To investigate the role of Bcl-xL phosphorylation at Ser49 in cell cycle regulation.
  • To identify the kinase responsible for Bcl-xL(Ser49) phosphorylation.
  • To determine the functional consequences of Bcl-xL(Ser49) phosphorylation on G2 checkpoint stability and cytokinesis.

Main Methods:

  • Analysis of Bcl-xL phosphorylation mutants.
  • Cell synchronization and treatment with DNA damaging agents or microtubule poisons.
  • Immunofluorescence microscopy to detect phospho-Bcl-xL(Ser49) localization.
  • In vitro kinase assays, small interfering RNA (siRNA) knockdown, and pharmacological inhibition.
  • Co-immunoprecipitation to study protein interactions.

Main Results:

  • Bcl-xL(Ser49Ala) mutant cells show reduced G2 checkpoint stability after DNA damage and delayed cytokinesis.
  • Phospho-Bcl-xL(Ser49) levels are cell cycle-dependent, appearing in S/G2 and disappearing during early mitosis.
  • Phospho-Bcl-xL(Ser49) accumulates in centrosomes during G2 arrest and co-localizes with dynein during telophase/cytokinesis.
  • Polo-like kinase 3 (PLK3) was identified as the kinase responsible for Bcl-xL(Ser49) phosphorylation.

Conclusions:

  • PLK3-mediated phosphorylation of Bcl-xL at Ser49 is a novel mechanism for stabilizing the G2 DNA damage checkpoint.
  • Phospho-Bcl-xL(Ser49) plays a critical role in regulating mitotic exit and cytokinesis.
  • These findings reveal a new function for Bcl-xL phosphorylation independent of its anti-apoptotic role.

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