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A-Raf and Raf-1 work together to influence transient ERK phosphorylation and Gl/S cell cycle progression

Kathryn Mercer1, Susan Giblett, Anthony Oakden

  • 1Department of Biochemistry, University of Leicester, Adrian Building, University Road, Leicester LEI 7RH, UK.

Oncogene
|April 28, 2005
PubMed

Insights

The Raf/MEK/ERK pathway is crucial for cell signaling. Combined knockout of A-Raf and Raf-1 in mice severely impacts embryonic development by reducing cell proliferation and delaying cell cycle progression.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Genetics

Background:

  • The Raf/MEK/ERK signaling pathway regulates critical cellular processes including proliferation, apoptosis, migration, and differentiation.
  • A-Raf and Raf-1 are key isotypes within this pathway, but their combined roles in vivo are not fully understood.

Purpose of the Study:

  • To investigate the combined functional contribution of A-Raf and Raf-1 to the Raf/MEK/ERK signaling pathway.
  • To elucidate the impact of simultaneous genetic ablation of A-raf and raf-1 on embryonic development and cellular functions.

Main Methods:

  • Generation of double knockout (DKO) mice lacking both A-raf and raf-1 genes.
  • Phenotypic analysis of DKO embryos, including assessment of apoptosis and proliferation (Ki67 staining).
  • Characterization of DKO mouse embryonic fibroblasts (MEFs) for cell cycle progression (S phase entry) and signaling molecule activation (MEK, ERK, c-Fos, cyclin D1).

Main Results:

  • DKO mice exhibit a more severe phenotype than single knockouts, with embryonic lethality around E10.5.
  • DKO embryos show no significant changes in apoptosis but a generalized reduction in proliferation.
  • DKO MEFs display delayed S phase entry, reduced transient MEK/ERK phosphorylation, and decreased c-Fos and cyclin D1 expression, while sustained ERK phosphorylation remains unaffected.

Conclusions:

  • Raf-1 and A-Raf play a combined, essential role in regulating transient ERK activation.
  • The coordinated function of Raf-1 and A-Raf is critical for maintaining normal cell cycle progression rates and embryonic development.

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