c-fos transcriptional activation and repression correlate temporally with the phosphorylation status of TCF

EMBO J. 1993 Jun;12(6):2377-87.


EGF-induction of human astrocytoma and A431 cells leads to c-fos transcriptional activation and then repression. This could be correlated with changes in the DNA binding characteristics of the c-fos regulatory protein ternary complex factor (TCF) present in nuclear extracts from these cells. Band shifts showed the appearance of induction-related slowly migrating protein-DNA complexes, detected as ternary complexes on the c-fos SRE using a truncated SRF molecule and by direct binding to the Drosophila E74 Ets-protein recognition sequence. By several criteria both types of complexes represented TCF. The appearance of the slow ternary and direct complexes correlated with c-fos transcriptional activation, and their disappearance coincided with the ensuing c-fos shut-off. Blocking c-fos transcriptional repression with the phosphatase inhibitor okadaic acid led to their continued presence. They were sensitive to protein phosphatase 2A but not 1 alpha, and similar slow complexes were formed by partially purified p62TCF phosphorylated by a copurifying kinase activity. Thus the phosphorylation state of TCF correlated strongly with c-fos promoter activity. Since ternary complex formation mediated by full-sized SRF was only slightly affected under comparable conditions, we propose a model for c-fos regulation involving modification of constitutively bound TCF.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Division / genetics
  • DNA, Neoplasm / metabolism
  • DNA-Binding Proteins / metabolism*
  • Ethers, Cyclic / pharmacology
  • Genes, fos*
  • HeLa Cells
  • Humans
  • Okadaic Acid
  • Phosphoprotein Phosphatases / metabolism
  • Phosphorylation
  • Promoter Regions, Genetic
  • Protein Phosphatase 2
  • Transcription Factors / metabolism*
  • Transcriptional Activation*
  • Tumor Cells, Cultured


  • DNA, Neoplasm
  • DNA-Binding Proteins
  • Ethers, Cyclic
  • Transcription Factors
  • p62TCF protein, human
  • Okadaic Acid
  • Phosphoprotein Phosphatases
  • Protein Phosphatase 2