The Mos/MAP kinase pathway stabilizes c-Fos by phosphorylation and augments its transforming activity in NIH 3T3 cells

EMBO J. 1995 Oct 16;14(20):5048-59.


The c-mos proto-oncogene product, Mos, is a serine/threonine kinase that can activate ERK1 and 2 mitogen-activated protein (MAP) kinases by direct phosphorylation of MAPK/ERK kinase (MEK). ERK activation is essential for oncogenic transformation of NIH 3T3 cells by Mos. In this study, we examined how mitogenic and oncogenic signalling from the Mos/MEK/ERK pathway reaches the nucleus to activate downstream target genes. We show that c-Fos (the c-fos protooncogene product), which is an intrinsically unstable nuclear protein, is metabolically highly stabilized, and greatly enhances the transforming efficiency of NIH 3T3 cells, by Mos. This stabilization of c-Fos required Mos-induced phosphorylation of its C-terminal region on Ser362 and Ser374, and double replacements of these serines with acidic (Asp) residues markedly increased the stability and transforming efficiency of c-Fos even in the absence of Mos. Moreover, activation of the ERK pathway was necessary and sufficient for the c-Fos phosphorylation and stabilization by Mos. These results indicate that c-Fos undergoes stabilization, and mediates at least partly the oncogenic signalling, by the Mos/MEK/ERK pathway. The present findings also suggest that, in general, the ERK pathway may regulate the cell fate and function by affecting the metabolic stability of c-Fos.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3T3 Cells
  • Amino Acid Sequence
  • Animals
  • Calcium-Calmodulin-Dependent Protein Kinases / metabolism*
  • Cell Nucleus / metabolism
  • Cell Transformation, Neoplastic*
  • Cloning, Molecular
  • Immunoblotting
  • Mice
  • Mitogen-Activated Protein Kinases / metabolism
  • Molecular Sequence Data
  • Mutation
  • Nerve Tissue Proteins / metabolism
  • Phosphorylation
  • Precipitin Tests
  • Proto-Oncogene Proteins c-fos / genetics
  • Proto-Oncogene Proteins c-fos / metabolism*
  • Proto-Oncogene Proteins c-mos / metabolism*
  • Recombinant Proteins / metabolism
  • Serine / metabolism
  • Signal Transduction*
  • Transfection


  • Nerve Tissue Proteins
  • Proto-Oncogene Proteins c-fos
  • Recombinant Proteins
  • Serine
  • Proto-Oncogene Proteins c-mos
  • Calcium-Calmodulin-Dependent Protein Kinases
  • Mitogen-Activated Protein Kinases