Cell proliferation and cell cycle progression are not impaired in fibroblasts and ES cells lacking c-Fos

Oncogene. 1995 Jan 5;10(1):79-86.


The transcription factor AP-1 is thought to play an important role in the control of cell proliferation, but the function of individual Fos and Jun family members is a largely unresolved issue. To directly analyse the function of c-Fos in the control of cell proliferation we have used embryonic stem (ES) cells and fibroblasts lacking c-Fos due to a disruption of the c-fos gene by homologous recombination. Our results demonstrate that proliferation of normally cycling cells and reentry of quiescent cells into the cell cycle following serum stimulation are not c-Fos-dependent and occur with similar efficiency in c-fos-/- and control cells. We also show that there is no compensatory overexpression or activation of other known Fos or Jun family members. On the contrary, the c-fos-/- cells showed a reduced induction of fra-1 after serum stimulation which is in agreement with the previous identification of fra-1 as a c-Fos target gene. Comparison of the AP-1 binding and transactivation activities in c-fos-/- and +/+ fibroblasts by electrophoretic mobility antibody supershift and CAT assays suggests that c-Fos is not a major component of AP-1 complexes in these cells. It is therefore conceivable that the lack of any detectable effect on cell proliferation in c-fos-/- cells might be due to a functional redundancy among the different AP-1 family members.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3T3 Cells
  • Animals
  • Cell Cycle / genetics*
  • Cell Division / genetics*
  • Cells, Cultured
  • Embryo, Mammalian / cytology
  • Fibroblasts / cytology
  • Genes, fos*
  • Genes, jun
  • Mice
  • Stem Cells / cytology
  • Transcription Factor AP-1 / metabolism


  • Transcription Factor AP-1