Differential regulation of TGF-beta signaling through Smad2, Smad3 and Smad4.
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.
Kretschmer
Anny
A
atugen AG, Robert-Roessle-Strasse 10, Otto Warburg Hause (No 80), Berlin 13125, Germany.
Moepert
Kristin
K
Dames
Sibylle
S
Sternberger
Maria
M
Kaufmann
Joerg
J
Klippel
Anke
A
D015153:Blotting, Western; D002453:Cell Cycle; D002460:Cell Line; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000502:physiology*; D015536:Down-Regulation; D004591:Electrophoresis, Polyacrylamide Gel; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D006801:Humans; D015151:Immunoblotting; D020411:Oligonucleotide Array Sequence Analysis; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction; D051899:Smad2 Protein; D051900:Smad3 Protein; D051901:Smad4 Protein; D015534:Trans-Activators / Q000502:physiology*; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism
D004268:DNA-Binding Proteins; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; C497796:SMAD4 protein, human; D051899:Smad2 Protein; D051900:Smad3 Protein; D051901:Smad4 Protein; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D012313:RNA