Differential regulation of TGF-beta signaling through Smad2, Smad3 and Smad4

Oncogene. 2003 Oct 2;22(43):6748-63. doi: 10.1038/sj.onc.1206791.


Smad transcription factors mediate the growth inhibitory effect of transforming growth factor-beta (TGF-beta) in many cell types. Mutational inactivation of Smads has been correlated with loss of responsiveness to TGF-beta-mediated signal transduction. In this study, we compare the contribution of individual Smads to TGF-beta-induced growth inhibition and endogenous gene expression in isogenic cellular backgrounds. Smad2, Smad3 and Smad4 expression were selectively inhibited in differentiation-competent cells by using improved antisense molecules. We found that TGF-beta mediates its inhibitory effect on HaCaT keratinocyte cell growth predominantly through Smad3. Inhibition of Smad3 expression was sufficient to interfere with TGF-beta-induced cell cycle arrest and to induce or suppress endogenous cell cycle regulators. Inhibition of Smad4 expression exhibited a partial effect, whereas inhibition of Smad2 expression had no effect. By gene expression profiling, we identified TGF-beta-dependent genes that are differentially regulated by Smad2 and Smad3 under regular growth conditions on a genome-wide scale. We show that Smad2, Smad3 and Smad4 contribute to the regulation of TGF-beta responses to varying extents, and demonstrate, in addition, that these Smads exhibit distinct roles in different cell types.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blotting, Western
  • Cell Cycle
  • Cell Line
  • DNA Mutational Analysis
  • DNA-Binding Proteins / physiology*
  • Down-Regulation
  • Electrophoresis, Polyacrylamide Gel
  • Flow Cytometry
  • Gene Expression Regulation*
  • Humans
  • Immunoblotting
  • Oligonucleotide Array Sequence Analysis
  • Oligonucleotides, Antisense / pharmacology
  • RNA / metabolism
  • RNA, Messenger / metabolism
  • Signal Transduction*
  • Smad2 Protein
  • Smad3 Protein
  • Smad4 Protein
  • Trans-Activators / physiology*
  • Transfection
  • Transforming Growth Factor beta / biosynthesis*
  • Transforming Growth Factor beta / genetics*
  • Transforming Growth Factor beta / metabolism


  • DNA-Binding Proteins
  • Oligonucleotides, Antisense
  • RNA, Messenger
  • SMAD2 protein, human
  • SMAD3 protein, human
  • SMAD4 protein, human
  • Smad2 Protein
  • Smad3 Protein
  • Smad4 Protein
  • Trans-Activators
  • Transforming Growth Factor beta
  • RNA