Separation of v-Src-induced mitogenesis and morphological transformation by inhibition of AP-1

M C Frame, K Simpson, V J Fincham, D H Crouch

Research output: Contribution to journalArticlepeer-review

Abstract

v-Src activity results in both morphological transformation and reentry of quiescent chick embryo fibroblasts (CEF) into cell cycle. We have previously used temperature-sensitive v-Src mutants to show that enhanced activity of cellular AP-1 in the first few hours after activation of v-Src invariably precedes the biological consequences. Here we have investigated whether the early activation of AP-1 is essential for any or all of the v-Src responses by using a mutant c-Fos that comprises the leucine zipper and a disrupted basic region. Expression of the c-Fos mutant partially reduced cellular AP-1 activity in exponentially growing cells. However, in CEF that had been made quiescent by serum deprivation, v-Src-induced stimulation of AP-1 DNA binding activity was substantially reduced. In addition, quiescent CEF stably transfected with this mutant show an impaired mitogenic response to v-Src, indicating that the AP-1 stimulation is a necessary prerequisite for cell-cycle reentry. The ability of v-Src to morphologically transform quiescent CEF was not impaired by the inhibition of AP-1 stimulation, indicating that the mitogenic and morphological consequences of v-Src have distinguishable biochemical mediators. Focal adhesion kinase, a recently identified determinant of cell morphology, undergoes a gel mobility shift, characteristic of its hyperphosphorylated state, in response to v-Src activation in cells expressing the inhibitory AP-1 protein. This provides further evidence that the pathways that regulate morphological transformation are independent of AP-1.
Original languageEnglish
Pages (from-to)1177-84
Number of pages8
JournalMolecular Biology of the Cell
Volume5
Issue number11
Publication statusPublished - Nov 1994

Keywords

  • Animals
  • Cell Cycle
  • Cell Size
  • Cell Transformation, Neoplastic
  • Cells, Cultured
  • Chick Embryo
  • DNA-Binding Proteins
  • Gene Expression Regulation
  • Genes, fos
  • Genes, src
  • Proto-Oncogene Proteins c-fos
  • Transcription Factor AP-1
  • Transfection

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