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Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay
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The oncogenic serine/threonine kinase Pim-1 directly phosphorylates and activates the G2/M specific phosphatase

Malte Bachmann1, Christian Kosan, Pei Xiang Xing

  • 1Institut für Zellbiologie (Tumorforschung), IFZ, Universitätsklinikum Essen, Virchowstrasse 173, D-45122 Essen, Germany.

The International Journal of Biochemistry & Cell Biology
|December 17, 2005
PubMed

Insights

The proto-oncogene Pim-1 kinase directly phosphorylates and activates Cdc25C phosphatase. This interaction promotes cell cycle progression at the G2/M transition, highlighting Pim-1

Area of Science:

  • Molecular Biology
  • Cell Cycle Regulation
  • Oncogenesis

Background:

  • The proto-oncogene Pim-1 is a serine-threonine kinase involved in cytokine signaling and cell cycle progression.
  • Pim-1 influences cell cycle regulators including p21(Waf), Cdc25A, and C-TAK1.
  • Cdc25C phosphatase regulates the G2/M cell cycle transition and can be inactivated by C-TAK1.

Purpose of the Study:

  • To investigate the interaction between Pim-1 and Cdc25C.
  • To determine if Pim-1 directly phosphorylates Cdc25C.
  • To elucidate the functional consequence of Pim-1 phosphorylation on Cdc25C activity and cell cycle progression.

Main Methods:

  • Biochemical assays to assess protein-protein interactions and phosphorylation.
  • Immuno-fluorescence microscopy to determine subcellular localization of Pim-1 and Cdc25C.
  • Cell transfection and G2/M cell cycle arrest using bleomycin to evaluate cell cycle progression.

Main Results:

  • Pim-1 directly interacts with and phosphorylates the N-terminal region of Cdc25C.
  • Pim-1 and Cdc25C co-localize in the cytoplasm of epithelial and myeloid cells.
  • Phosphorylation by Pim-1 enhances Cdc25C phosphatase activity, promoting G2/M to G1 progression in bleomycin-arrested cells.

Conclusions:

  • Pim-1 directly activates Cdc25C phosphatase through phosphorylation.
  • Pim-1 functions as a positive regulator of the cell cycle at the G2/M transition.
  • This mechanism provides a novel insight into Pim-1's role in cell cycle control and oncogenesis.

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