c-Ski inhibits the TGF-beta signaling pathway through stabilization of inactive Smad complexes on Smad-binding elements.
c-Ski inhibits transforming growth factor-beta (TGF-beta) signaling through interaction with Smad proteins. c-Ski represses Smad-mediated transcriptional activation, probably through its action as a transcriptional co-repressor. c-Ski also inhibits TGF-beta-induced downregulation of genes such as c-myc. However, mechanisms for transcriptional regulation of target genes by c-Ski have not been fully determined. In this study, we examined how c-Ski inhibits both TGF-beta-induced transcriptional activation and repression. DNA-affinity precipitation analysis revealed that c-Ski enhances the binding of Smad2 and 4, and to a lesser extent Smad3, to both CAGA and TGF-beta1 inhibitory element probes. A c-Ski mutant, which is unable to interact with Smad4, failed to enhance the binding of Smad complex on these probes and to inhibit the Smad-responsive promoter. These results suggest that stabilization of inactive Smad complexes on DNA is a critical event in c-Ski-mediated inhibition of TGF-beta signaling.
Suzuki
Hiroyuki
H
Department of Molecular Pathology, Graduate School of Medicine, University of Tokyo, Tokyo 113-0033, Japan.
Yagi
Ken
K
Kondo
Miki
M
Kato
Mitsuyasu
M
Miyazono
Kohei
K
Miyazawa
Keiji
K
D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D009154:Mutation; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D015398:Signal Transduction; D051785:Smad Proteins; D015534:Trans-Activators / Q000378:metabolism*; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000378:metabolism*
D004268:DNA-Binding Proteins; D011518:Proto-Oncogene Proteins; D051785:Smad Proteins; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; C060614:SKI protein, human