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Multisite M-phase phosphorylation of Xenopus Wee1A

Sun Young Kim1, Eun Joo Song, Kong-Joo Lee

  • 1Department of Molecular Pharmacology, Stanford University School of Medicine, Stanford, CA 94305-5174, USA.

Molecular and Cellular Biology
|November 17, 2005
PubMed

Insights

Wee1A phosphorylation inactivates the Cdk1 inhibitor Wee1, promoting mitotic entry. Multisite phosphorylation cooperatively inactivates Wee1A and promotes its proteolysis, crucial for cell cycle progression.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Wee1 is a Cdk1 inhibitor crucial for regulating mitotic entry.
  • Wee1 inactivation occurs via proteolysis, translation, transcription, and posttranslational modifications.
  • Understanding Wee1 regulation is key to comprehending cell cycle control.

Purpose of the Study:

  • To identify and characterize phosphorylation sites on embryonic Xenopus Wee1A.
  • To elucidate the role of these phosphorylation sites in Wee1A inactivation and proteolysis.
  • To establish the significance of phosphorylation-dependent Wee1A inactivation in promoting M-phase entry.

Main Methods:

  • Site-directed mutagenesis studies to identify phosphorylation sites.
  • Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) for phosphoprotein analysis.
  • Analysis of mitotic gel shifts and proteolysis in Xenopus egg extracts.

Main Results:

  • Five N-terminal phosphorylation sites on Xenopus Wee1A were identified.
  • Ser 38, Thr 53, and Ser 62 are required for the mitotic gel shift.
  • Ser 38 and Thr 53 regulate interphase proteolysis, while Thr 104 and Thr 150 drive mitotic inactivation.
  • Mutants lacking Thr 150 or Thr 104 exhibited enhanced inhibition of mitotic entry.

Conclusions:

  • Phosphorylation-dependent inactivation of Wee1A is a critical mechanism for M-phase entry.
  • Multisite phosphorylation cooperatively inactivates Wee1A and promotes its proteolysis.
  • These findings provide new insights into the intricate regulation of cell cycle progression.

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