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Sumoylation is involved in beta-catenin-dependent activation of Tcf-4

Hideki Yamamoto1, Motomasa Ihara, Yoshiharu Matsuura

  • 1Department of Biochemistry, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan.

The EMBO Journal
|May 3, 2003
PubMed

Insights

Sumoylation of Tcf-4, a Wnt signaling molecule, occurs naturally and impacts gene expression. This post-translational modification, regulated by PIASy and Axam, is crucial for beta-catenin-dependent Wnt signaling.

Area of Science:

  • Molecular Biology
  • Cellular Biology
  • Biochemistry

Background:

  • Sumoylation is a post-translational modification regulating protein functions.
  • The Wnt signaling pathway is critical for development and disease.
  • Tcf-4 is a key transcription factor in the Wnt pathway.

Purpose of the Study:

  • To investigate the role of sumoylation in Tcf-4 function within the Wnt signaling pathway.
  • To identify sumoylation sites on Tcf-4 and their regulators.
  • To determine the impact of Tcf-4 sumoylation on its transcriptional activity.

Main Methods:

  • Western blotting to detect sumoylation.
  • Co-immunoprecipitation to assess protein interactions.
  • Immunofluorescence microscopy for subcellular localization.
  • RNA interference to modulate protein levels.
  • Site-directed mutagenesis to alter sumoylation sites.

Main Results:

  • Tcf-4 undergoes endogenous sumoylation at Lys297.
  • PIASy (a SUMO E3 enzyme) enhances Tcf-4 sumoylation, while Axam (a desumoylation enzyme) inhibits it.
  • Sumoylated Tcf-4, SUMO-1, and PIASy co-localize in the nucleus and PML bodies.
  • PIASy enhances beta-catenin-dependent Tcf-4 transcriptional activity, whereas Axam inhibits it.
  • Mutating Lys297 to arginine reduces Tcf-4 activation by beta-catenin and PIASy.

Conclusions:

  • Sumoylation of Tcf-4 is a critical regulatory mechanism in the Wnt signaling pathway.
  • The sumoylation status of Tcf-4 influences its interaction with beta-catenin and its transcriptional activity.
  • Tcf-4 sumoylation plays a significant role in beta-catenin-dependent gene expression.

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