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Mos mediates the mitotic activation of p42 MAPK in Xenopus egg extracts

Jianbo Yue1, James E Ferrell

  • 1Department of Molecular Pharmacology, Stanford University, Stanford, CA 94305-5174, USA. jyue@stanford.edu

Current Biology : CB
|September 3, 2004
PubMed

Insights

Mos protein activates the ERK1/ERK2 MAPK pathway during mitosis in Xenopus egg extracts. This finding identifies Mos as the key kinase responsible for mitotic p42 MAPK activation, impacting cell division timing.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Mitotic activation of ERK1/ERK2 MAP kinases (MAPKs) is crucial for cell division.
  • MEK1 activates p42 MAPK during mitosis, but the upstream kinase remains unidentified.
  • Mos, a MAP kinase kinase kinase, is present in various cell types.

Purpose of the Study:

  • To identify the MEK1-activating kinase responsible for mitotic p42 MAPK activation in Xenopus egg extracts.
  • To investigate the role of Mos in the activation of the p42 MAPK pathway during mitosis.

Main Methods:

  • Partial purification of a MEK-activating protein kinase from mitotic Xenopus egg extracts.
  • Identification of the purified kinase as the Mos protooncoprotein.
  • Immunodepletion experiments to assess the role of Mos, Raf-1, and B-Raf in p42 MAPK activation.

Main Results:

  • Mos was identified as the Cdc2-cyclin B-induced MEK-activating protein kinase.
  • Immunodepletion of Mos abolished Delta90 cyclin B-Cdc2-stimulated p42 MAPK activation.
  • Mos depletion also abolished the transient activation of p42 MAPK in cycling egg extracts, unlike Raf-1 and B-Raf.

Conclusions:

  • Mos is the primary kinase responsible for the mitotic activation of the p42 MAPK pathway in Xenopus egg extracts.
  • Mos plays a critical role in regulating the timing and execution of mitosis through MAPK activation.

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