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Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay
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Identification of beta-catenin as a novel substrate of Polo-like kinase 1

Tsuyoshi Arai1, Kyosuke Haze, Yuko Iimura-Morita

  • 1Tsukuba Research Institute, Banyu Pharmaceutical Co., Ltd., Tsukuba, Ibaraki, Japan.

Cell Cycle (Georgetown, Tex.)
|November 13, 2008
PubMed

Insights

Researchers found that beta-catenin is a novel substrate of Polo-like kinase 1 (Plk1). Plk1 directly phosphorylates beta-catenin at Ser-718, impacting its role in M phase progression.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Polo-like kinase 1 (Plk1) is crucial for M phase progression.
  • Plk1 regulates numerous downstream substrates through phosphorylation.

Purpose of the Study:

  • To identify novel substrates of Plk1.
  • To investigate the interaction between Plk1 and beta-catenin.

Main Methods:

  • Phospho-specific antibody generation and usage.
  • In vitro kinase assays with recombinant Plk1.
  • Small interfering RNA (siRNA) for Plk1 depletion.
  • Coimmunoprecipitation and GST pull-down assays.

Main Results:

  • Beta-catenin was identified as a novel substrate of Plk1.
  • Serine 718 (Ser-718) of beta-catenin is a direct phosphorylation site by Plk1.
  • Plk1-mediated phosphorylation of Ser-718 increases with Plk1 overexpression and decreases upon Plk1 depletion.
  • Phosphorylation at Ser-718 correlates with Plk1's cell cycle-dependent expression, peaking in M phase.
  • A physical interaction between beta-catenin and Plk1 was confirmed.

Conclusions:

  • Beta-catenin is a physiological substrate of Plk1.
  • This finding offers new insights into beta-catenin's function during M phase.

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