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Activation of MPF in fission yeast

J B Millar1, G Lenaers, C McGowan

  • 1Department of Molecular, Scripps Research Institute, La Jolla, CA 92037.

Ciba Foundation Symposium
|January 1, 1992
PubMed

Insights

Two protein phosphatases, including the major cdc25 enzyme and a newly identified phosphatase, activate fission yeast cell division by dephosphorylating p34cdc2 at the G2/M transition.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Cell cycle progression is regulated by cyclin-dependent kinases.
  • In fission yeast, p34cdc2/cyclin activity is critical for entry into mitosis.
  • Activation of p34cdc2/cyclin at the G2/M boundary involves dephosphorylation of the Tyr15 residue on p34cdc2.

Purpose of the Study:

  • To identify and characterize the protein phosphatases responsible for Tyr15 dephosphorylation of p34cdc2 in fission yeast.
  • To elucidate the roles of different phosphatases in regulating the G2/M transition.

Main Methods:

  • Biochemical assays to measure protein phosphatase activity.
  • Genetic analysis of fission yeast mutants.
  • Identification of novel phosphatase genes.

Main Results:

  • Two distinct protein phosphatase activities were found to dephosphorylate Tyr15 of p34cdc2.
  • The major activity is attributed to the cdc25 gene product, a protein tyrosine phosphatase.
  • A novel fission yeast protein tyrosine phosphatase contributes a minor dephosphorylation activity.

Conclusions:

  • Fission yeast utilizes at least two protein tyrosine phosphatases for the regulation of p34cdc2/cyclin activation at the G2/M boundary.
  • Cdc25 is the primary phosphatase, with a newly identified phosphatase playing a secondary role in this critical cell cycle event.

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