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Activation of AP-1 by okadaic acid in mouse keratinocytes associated with hyperphosphorylation of c-jun

J Peng1, G T Bowden, F E Domann

  • 1Division of Radiation Oncology, University of Iowa, Iowa City 52242, USA.

Molecular Carcinogenesis
|January 1, 1997
PubMed

Insights

Okadaic acid (OA) promotes skin tumors by increasing activator protein-1 (AP-1) DNA binding and transcriptional activation. This effect is mediated by OA-induced hyperphosphorylation of c-jun protein in mouse keratinocytes.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Dermatology

Background:

  • Okadaic acid (OA) is a specific inhibitor of protein phosphatases 1 and 2A.
  • OA is recognized as a potent promoter of mouse skin tumors.

Purpose of the Study:

  • To investigate the effects of OA on the regulation of c-jun/activator protein-1 (AP-1) transcriptional activation in mouse keratinocytes.
  • To elucidate the molecular mechanisms underlying OA-induced skin tumor promotion.

Main Methods:

  • Gel shift analysis to assess AP-1 DNA binding.
  • Western blot analysis to detect c-jun protein levels and phosphorylation.
  • Reporter gene assays to measure AP-1 transactivation.
  • Quantitative real-time PCR to determine c-jun mRNA levels.

Main Results:

  • OA treatment significantly induced AP-1 DNA binding and transactivation in mouse keratinocytes.
  • OA treatment led to a dramatic increase in c-jun mRNA and protein levels.
  • OA induced significant accumulation of Ser 73-phosphorylated c-jun protein.

Conclusions:

  • OA-induced skin tumor promotion is, at least in part, attributed to enhanced AP-1 DNA binding and transactivation.
  • The observed effects are mediated by OA-induced hyperphosphorylation of c-jun.

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