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TGF-beta inhibits p70 S6 kinase via protein phosphatase 2A to induce G(1) arrest

C Petritsch1, H Beug, A Balmain

  • 1IMP, Research Institute for Molecular Pathology, A-1030 Vienna, Austria.

Genes & Development
|December 22, 2000
PubMed

Insights

Transforming growth factor-beta (TGF-beta) triggers cell cycle arrest through two pathways: Smad activation and p70 S6 kinase (p70(s6k)) inhibition. Both pathways are necessary to release epithelial cells from TGF-beta-induced arrest.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Signal Transduction

Background:

  • Transforming growth factor-beta (TGF-beta) is a key regulator of cell proliferation and differentiation.
  • TGF-beta signaling pathways are complex and involve multiple downstream effectors.
  • Understanding these pathways is crucial for comprehending cell cycle control and cancer development.

Purpose of the Study:

  • To elucidate the mechanisms by which TGF-beta induces G(1) cell cycle arrest.
  • To identify parallel TGF-beta-dependent pathways regulating cell cycle progression.
  • To investigate the roles of Smad proteins and p70 S6 kinase (p70(s6k)) in TGF-beta-mediated cell cycle control.

Main Methods:

  • Investigated TGF-beta receptor interactions with downstream signaling molecules.
  • Utilized biochemical assays to assess protein phosphorylation and dephosphorylation.
  • Examined the association of protein phosphatase-2A (PP2A) subunits with p70(s6k).
  • Analyzed the requirement of Smad proteins and p70(s6k) inhibition for cell cycle release.

Main Results:

  • TGF-beta receptor activation leads to Smad2/3 phosphorylation and G(1) arrest.
  • A parallel pathway involves TGF-beta receptor association with PP2A-Balpha, leading to p70(s6k) dephosphorylation and inactivation.
  • Both Smad-dependent and p70(s6k) inhibition pathways are required for epithelial cells to exit TGF-beta-induced G(1) arrest.
  • TGF-beta modulates both translational and posttranscriptional control of cell cycle progression.

Conclusions:

  • TGF-beta utilizes two distinct but cooperative pathways to enforce G(1) cell cycle arrest.
  • The interplay between Smad signaling and PP2A/p70(s6k) pathway is critical for cell cycle regulation by TGF-beta.
  • These findings reveal a comprehensive model of TGF-beta's role in cell cycle control, impacting translational and posttranscriptional mechanisms.

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