The steroid receptor co-activator-1 (SRC-1) potentiates TGF-beta/Smad signaling: role of p300/CBP.
The three related 160-kDa proteins, SRC-1, TIF-2 and RAC-3, were initially identified as factors interacting with nuclear receptors. They have also been reported to potentiate the activity of other transcription factors such as AP-1 or NF-kappaB. The aim of this work was to identify whether SRC-1 interferes with the TGF-beta/Smad signaling pathway, and if so, to identify its underlying mechanisms of action. Using transient cell transfection experiments performed in human dermal fibroblasts with the Smad3/4-specific (SBE)4-lux reporter construct, as well as the human PAI-1 promoter, we determined that SRC-1 enhances TGF-beta-induced, Smad-mediated, transcription. Likewise, SRC-1 overexpression potentiated TGF-beta-induced upregulation of PAI-1 steady-state mRNA levels. Using a mammalian two-hybrid system, we demonstrated that SRC-1 interacts with the transcriptional co-activators p300/CBP, but not with Smad3. Overexpression of the adenovirus E1A oncoprotein, an inhibitor of CBP/p300 activity, prevented the enhancing effect of SRC-1 on Smad3/4-mediated transcription, indicating that p300/CBP may be required for SRC-1 effect. Such hypothesis was validated, as expression of a mutant form of SRC-1 lacking the CBP/p300-binding site failed to upregulate Smad3/4-dependent transcription, while full-length SRC-1 potentiated p300.Smad3 interactions. These results identify SRC-1 as a novel Smad3/4 transcriptional partner, facilitating the functional link between Smad3 and p300/CBP.
Dennler
Sylviane
S
INSERM U697, Institut de recherche sur la peau, Hôpital Saint-Louis, Paris, France.
Pendaries
Valérie
V
Tacheau
Charlotte
C
Costas
Monica A
MA
Mauviel
Alain
A
Verrecchia
Franck
F
D002460:Cell Line; D004268:DNA-Binding Proteins / Q000502:physiology*; D005347:Fibroblasts; D017930:Genes, Reporter; D051548:Histone Acetyltransferases; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D009687:Nuclear Proteins / Q000502:physiology*; D056920:Nuclear Receptor Coactivator 1; D010957:Plasmids; D015398:Signal Transduction / Q000502:physiology*; D012867:Skin; D051785:Smad Proteins; D015534:Trans-Activators / Q000502:physiology*; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000502:physiology*
D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D051785:Smad Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D051548:Histone Acetyltransferases; C538859:NCOA1 protein, human; D056920:Nuclear Receptor Coactivator 1