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The transcriptional co-activator P/CAF potentiates TGF-beta/Smad signaling

S Itoh1, J Ericsson, J Nishikawa

  • 1The Netherlands Cancer Institute, Division of Cellular Biochemistry, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands. sitoh@nki.nl

Nucleic Acids Research
|November 1, 2000
PubMed

Insights

P300/CBP-associated factor (P/CAF) acts as a co-activator in transforming growth factor-beta (TGF-beta) signaling. P/CAF enhances the transcriptional activity of Smad proteins, which are key mediators of TGF-beta responses.

Area of Science:

  • Molecular Biology
  • Cell Signaling
  • Gene Regulation

Background:

  • Smad proteins are crucial intracellular mediators of transforming growth factor-beta (TGF-beta) signaling.
  • TGF-beta signaling regulates critical cellular processes including proliferation, differentiation, and apoptosis.
  • Understanding the regulation of Smad activity is essential for deciphering cellular responses to TGF-beta.

Purpose of the Study:

  • To investigate the potential co-activator role of P/CAF (P300/CBP-associated factor) in TGF-beta/Smad signaling.
  • To elucidate the physical and functional interactions between P/CAF and Smad proteins.

Main Methods:

  • In vitro interaction assays to test direct binding between P/CAF and Smad3.
  • Mammalian cell culture and TGF-beta stimulation to study endogenous protein interactions.
  • Co-immunoprecipitation to confirm interactions between Smad2/Smad3 and P/CAF.
  • Reporter gene assays using Gal4-Smad fusion proteins to assess transcriptional activity.
  • TGF-beta/Smad3-induced transcriptional response assays with and without P/CAF, p300, and Smad4.

Main Results:

  • P/CAF directly interacts with Smad3 in vitro.
  • Smad2 and Smad3 interact with P/CAF in mammalian cells upon TGF-beta type I receptor activation.
  • The interaction occurs between the MH2 domain of Smad3 and the N-terminal region of P/CAF.
  • P/CAF potentiates the transcriptional activity of Smad2 and Smad3.
  • P/CAF enhances TGF-beta/Smad3-induced transcription, with further potentiation by p300 and Smad4.

Conclusions:

  • P/CAF functions as a co-activator in TGF-beta/Smad signaling, enhancing Smad-mediated transcription.
  • P/CAF may act independently or in conjunction with p300/CBP to activate Smad-dependent transcription.
  • A direct physical and functional interplay exists between Smad3 and P/CAF, both negative regulators of cell proliferation.

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