Role of p38 in stress activation of Sp1

Gene. 2006 Sep 1:379:51-61. doi: 10.1016/j.gene.2006.04.012. Epub 2006 May 4.

Abstract

Cell stressors such as physical forces can activate Sp1-dependent genes but the regulatory mechanisms are not defined. We determined if the stress-induced MAP kinase, p38, can phosphorylate Sp1 and thereby regulate the Sp1 target gene FLNA. We used Rat-2 cells and human gingival fibroblasts to examine stress-induced activation of an Sp1-dependent gene and SL2 cells, an Sp1-deficient model system, to facilitate interaction studies of transfected Sp1 with regulatory factors. Mechanical stress applied to Rat-2 cells increased promoter activity of the Sp1 target gene filamin A by >5-fold; activation was blocked by mutations to Sp1 binding sites in the filamin A promoter. Transfection experiments in SL2 cells with Sp1 expression vectors showed that when co-transfected with constitutively active p38, wild-type Sp1 but not an Sp1 binding mutant, increased promoter activity of the Sp1 target gene, filamin A, and enhanced binding of nuclear extracts to a filamin A promoter oligonucleotide. Filamin A promoter activity was blocked by dominant negative p38. Sp1 that was phosphorylated at Thr453 and Thr739 by constitutively active p38 bound to the filamin A promoter more effectively than un-phosphorylated Sp1. Recombinant active p38 phosphorylated wild-type Sp1 in vitro while the Sp1 Thr453Thr739 double mutant protein showed >3-fold reduction of phosphorylation. We conclude that stress activation of p38 phosphorylates Sp1 at specific threonine residues, modifications which in turn enhance the expression of Sp1-dependent genes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Binding Sites
  • Cells, Cultured
  • Contractile Proteins / genetics
  • Contractile Proteins / metabolism
  • Drosophila melanogaster / genetics
  • Drosophila melanogaster / metabolism
  • Fibroblasts / cytology
  • Fibroblasts / metabolism
  • Filamins
  • Gene Expression Regulation
  • Humans
  • Microfilament Proteins / genetics
  • Microfilament Proteins / metabolism
  • Phosphorylation
  • Promoter Regions, Genetic
  • Rats
  • Signal Transduction
  • Sp1 Transcription Factor / genetics
  • Sp1 Transcription Factor / metabolism*
  • Stress, Mechanical
  • Threonine / genetics
  • Threonine / metabolism
  • Transfection
  • p38 Mitogen-Activated Protein Kinases / metabolism
  • p38 Mitogen-Activated Protein Kinases / physiology*

Substances

  • Contractile Proteins
  • Filamins
  • Microfilament Proteins
  • Sp1 Transcription Factor
  • Threonine
  • p38 Mitogen-Activated Protein Kinases