The transcriptional co-activator P/CAF potentiates TGF-beta/Smad signaling.
Smads perform pivotal functions in the intracellular signaling of transforming growth factor-beta (TGF-beta). TGF-beta-mediated activation of TGF-beta type I receptor stimulates the phosphorylation of Smad2 and Smad3 and subsequent heteromeric complex formation with Smad4. The heteromeric Smad complexes translocate into the nucleus where they, in co-operation with co-activators and co-repressors, regulate transcriptional responses. Here we investigated the possible co-activator function of P/CAF in TGF-beta/Smad signaling. P/CAF was found to interact directly with Smad3 in vitro. Moreover, Smad2 and Smad3 interacted with P/CAF upon TGF-beta type I receptor activation in cultured mammalian cells. The interaction involves the MH2 domain of Smad3 and the N-terminal region of P/CAF. P/CAF potentiated the transcriptional activity of heterologous Gal4-Smad2 and Gal4-Smad3 fusion proteins. In addition, P/CAF potentiated the TGF-beta/Smad3-induced transcriptional responses, which could be further enhanced by co-activators p300 and Smad4. P/CAF may, therefore, activate Smad-mediated transcriptional responses independently or in co-operation with p300/CBP. Our results indicate a direct physical and functional interplay between two negative regulators of cell proliferation, Smad3 and P/CAF.
Itoh
S
S
The Netherlands Cancer Institute, Division of Cellular Biochemistry, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands. sitoh@nki.nl
Ericsson
J
J
Nishikawa
J
J
Heldin
C H
CH
ten Dijke
P
P
D000123:Acetyltransferases / Q000737:chemistry / Q000378:metabolism*; D030201:Activin Receptors, Type I; D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D019556:COS Cells; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D017930:Genes, Reporter / Q000235:genetics; D051548:Histone Acetyltransferases; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D017434:Protein Structure, Tertiary; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D051899:Smad2 Protein; D051900:Smad3 Protein; D015534:Trans-Activators / Q000737:chemistry / Q000378:metabolism*; D014157:Transcription Factors; D015533:Transcriptional Activation; D016212:Transforming Growth Factor beta / Q000378:metabolism / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D050880:p300-CBP Transcription Factors; D000099224:p300-CBP-Associated Factor
D000123:Acetyltransferases; D030201:Activin Receptors, Type I; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D051548:Histone Acetyltransferases; D009687:Nuclear Proteins; D017346:Protein Serine-Threonine Kinases; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta; D011993:Recombinant Fusion Proteins; D051899:Smad2 Protein; D051900:Smad3 Protein; D015534:Trans-Activators; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D050880:p300-CBP Transcription Factors; D000099224:p300-CBP-Associated Factor; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human