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M-phase MELK activity is regulated by MPF and MAPK

Caroline Badouel1, Roman Körner, Marie Frank-Vaillant

  • 1CNRS UMR 6061 Génétique et Développement, Université de Rennes, Rennes, France.

Cell Cycle (Georgetown, Tex.)
|April 22, 2006
PubMed

Insights

The study identifies key phosphorylation sites on Xenopus MELK (xMELK) during M-phase. Phosphorylation by MPF and MAPK enhances MELK activity, crucial for cell division regulation.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • The protein kinase MELK regulates cell proliferation, cell cycle progression, and mRNA splicing.
  • MELK activity is linked to its phosphorylation status and is maximal during mitosis.

Purpose of the Study:

  • To identify specific residues phosphorylated in Xenopus MELK (xMELK) during M-phase.
  • To investigate the role of MPF and MAPK pathways in xMELK phosphorylation and activity.

Main Methods:

  • Identification of phosphorylated residues in xMELK using M-phase egg extract.
  • In vivo and in vitro assays to study xMELK phosphorylation by MPF and MAPK.
  • Enzyme activity assays to assess the effect of phosphorylation on MELK function.

Main Results:

  • T414, T449, T451, T481, and S498 were identified as phosphorylated residues in xMELK.
  • Phosphorylations of T449, T451, and T481 are specific to mitosis.
  • MPF and MAPK pathways are involved in xMELK phosphorylation, with direct phosphorylation observed in vitro.
  • MPF directly phosphorylates xMELK at T481.
  • Phosphorylation by MPF and MAPK enhances xMELK activity.

Conclusions:

  • MELK phosphorylation by MPF and MAPK is a key regulatory mechanism.
  • This phosphorylation enhances MELK activity specifically during M-phase, impacting cell division.

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