Regulation of Smad7 promoter by direct association with Smad3 and Smad4

J Biol Chem. 1999 Nov 19;274(47):33412-8. doi: 10.1074/jbc.274.47.33412.

Abstract

Smad7 is a regulatory Smad protein that is able to antagonize signal transduction by transforming growth factor-beta (TGF-beta) and activin receptors. To characterize the regulation of Smad7 at the transcriptional level, we isolated the promoter region of the mouse Smad7 gene. When the Smad7 promoter luciferase reporter gene (-408 and +112 bp) was expressed in human hepatoma (HepG2) cells, its transcriptional activity was increased following TGF-beta or activin treatment. In addition, this region of the Smad7 promoter was stimulated by ectopic expression of Smad3 as well as constitutively active TGF-beta and activin receptors, indicating that Smad7 transcription was modulated by the signaling downstream those two receptors. A gel mobility shift assay indicated that a DNA fragment spanning -408 to -126 base pairs (bp) was able to directly bind purified Smad4. Furthermore, a consensus Smad3-Smad4 binding element (SBE) was discovered in this region of the promoter with a palindromic sequence of GTCTAGAC. A 33-bp Smad7 promoter fragment containing this SBE was able to bind Smad3 and Smad4. In human embryonic kidney 293 cells, the expression of constitutively active TGF-beta type I receptor was able to induce the formation of a Smad3- and Smad4-containing nuclear protein complex that bound the SBE. In HepG2 cells, TGF-beta1 treatment could induce the formation of an endogenous SBE-binding complex. Taken together, these data provided the first evidence that Smad7 transcription is regulated by TGF-beta and activin signaling through direct binding of Smad3 and Smad4 to the Smad7 promoter.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Activins
  • Animals
  • Base Sequence
  • Cell Line
  • DNA
  • DNA-Binding Proteins / genetics*
  • DNA-Binding Proteins / metabolism*
  • Humans
  • Inhibins / metabolism
  • Mice
  • Molecular Sequence Data
  • Promoter Regions, Genetic*
  • Protein Binding
  • Receptors, Transforming Growth Factor beta / metabolism
  • Smad3 Protein
  • Smad4 Protein
  • Smad7 Protein
  • Trans-Activators / genetics*
  • Trans-Activators / metabolism*
  • Transcription, Genetic
  • Transforming Growth Factor beta / metabolism
  • Tumor Cells, Cultured

Substances

  • DNA-Binding Proteins
  • Receptors, Transforming Growth Factor beta
  • SMAD3 protein, human
  • SMAD4 protein, human
  • SMAD7 protein, human
  • Smad3 Protein
  • Smad3 protein, mouse
  • Smad4 Protein
  • Smad4 protein, mouse
  • Smad7 Protein
  • Smad7 protein, mouse
  • Trans-Activators
  • Transforming Growth Factor beta
  • Activins
  • Inhibins
  • DNA

Associated data

  • GENBANK/AF167314