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Purification and molecular cloning of Plx1, a Cdc25-regulatory kinase from Xenopus egg extracts

A Kumagai1, W G Dunphy

  • 1Division of Biology, 216-76, Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA 91125, USA.

Science (New York, N.Y.)
|September 6, 1996
PubMed

Insights

A novel kinase, Plx1 (Polo-like kinase 1), activates the Cdc25 phosphatase by phosphorylation. This activation is crucial for controlling entry into mitosis, a key cell division process.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Mitosis is regulated by cyclin-dependent kinases like Cdc2.
  • Cdc2 activity is controlled by phosphorylation at specific residues (threonine-14 and tyrosine-15).
  • Cdc25 phosphatase activates Cdc2 by dephosphorylating these inhibitory sites.

Purpose of the Study:

  • To identify and characterize the kinase responsible for activating Cdc25 during mitosis.
  • To investigate the role of Plx1 in the regulation of Cdc25 activity.

Main Methods:

  • Purification of Plx1 kinase from Xenopus egg extracts.
  • Cloning of the complementary DNA for Plx1.
  • In vitro phosphorylation and activity assays using recombinant Plx1 and Cdc25.
  • Immunological detection using the MPM-2 antibody.

Main Results:

  • Plx1 was identified as a Polo family kinase that associates with and phosphorylates Cdc25.
  • Recombinant Plx1 phosphorylated Cdc25 and enhanced its phosphatase activity in vitro.
  • Cdc25 phosphorylated by Plx1 showed strong reactivity with the MPM-2 antibody, indicating mitotic phosphorylation.

Conclusions:

  • Plx1 is a key regulator of Cdc25 activity during mitosis.
  • Plx1-mediated phosphorylation of Cdc25 is important for controlling mitotic progression.
  • Plx1 represents a potential target for understanding cell cycle control.

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