Activation of transcription factor SAF involves its phosphorylation by protein kinase C

J Biol Chem. 2000 Dec 15;275(50):39727-33. doi: 10.1074/jbc.M007907200.

Abstract

The transcription factor serum amyloid A (SAA)-activating factor (SAF), a family of zinc finger proteins, plays a significant role in the induced expression of the SAA gene. Activity of SAF is regulated by a phosphorylation event involving serine/threonine protein kinase (Ray, A., Schatten, H., and Ray, B. K. (1999) J. Biol. Chem. 274, 4300-4308; Ray, A., and Ray, B. K. (1998) Mol. Cell. Biol. 18, 7327-7335). However, the identity of the protein kinase has so far remained unknown. Induction of SAA by phorbol 12-myristate 13-acetate, a known agonist of protein kinase C (PKC), suggested a potential role of the PKC signaling pathway in the activation process. The DNA binding activity of endogenous SAF was increased by agonists of PKC. In vitro phosphorylation of SAF-1 by PKC-beta markedly increased its DNA binding ability. Consistent with these findings, treatment of cells with activators of PKC or overexpression of PKC-betaII in transfected cells increased expression of an SAF-regulated promoter. Further analysis with a GAL4 reporter system indicated that PKC-mediated phosphorylation mostly increases the DNA binding activity of SAF-1. Together these data indicated that the PKC signaling pathway plays a major role in controlling expression of SAF-regulated genes by increasing the interaction between promoter DNA and phosphorylated SAF.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Cell Line
  • Cell Nucleus / metabolism
  • Chloramphenicol O-Acetyltransferase / metabolism
  • DNA-Binding Proteins / chemistry*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Genes, Reporter
  • Isoenzymes / metabolism
  • Phosphorylation
  • Plasmids / metabolism
  • Promoter Regions, Genetic
  • Protein Binding
  • Protein Kinase C / metabolism*
  • Protein Kinase C beta
  • Rabbits
  • Signal Transduction
  • Tetradecanoylphorbol Acetate / pharmacology
  • Transcription Factors
  • Transfection
  • Zinc Fingers

Substances

  • DNA-Binding Proteins
  • Isoenzymes
  • Transcription Factors
  • c-MYC-associated zinc finger protein
  • Chloramphenicol O-Acetyltransferase
  • Protein Kinase C
  • Protein Kinase C beta
  • Tetradecanoylphorbol Acetate