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Inhibition of Tcf3 binding by I-mfa domain proteins

L Snider1, H Thirlwell, J R Miller

  • 1Fred Hutchinson Cancer Research Center, University of Washington Medical Center, Seattle, Washington 98109.

Molecular and Cellular Biology
|March 10, 2001
PubMed

Insights

I-mfa and XIC inhibit the HMG box transcription factor XTcf3, impacting dorsal axis specification and gene expression in Xenopus embryos. These proteins may coordinate Wnt signaling and basic helix-loop-helix (bHLH) protein activities.

Area of Science:

  • Developmental Biology
  • Molecular Biology
  • Genetics

Background:

  • Basic helix-loop-helix (bHLH) proteins and HMG box transcription factors are crucial for embryonic development.
  • The Wnt signaling pathway plays a vital role in early embryonic patterning.
  • XTcf3 is an HMG box transcription factor involved in embryonic development.

Purpose of the Study:

  • To investigate the inhibitory effects of I-mfa and XIC on XTcf3 activity and DNA binding.
  • To determine the role of I-mfa and XIC in Xenopus embryonic development and Wnt signaling.

Main Methods:

  • Inhibition assays to assess XTcf3 activity and DNA binding.
  • Ectopic expression of I-mfa and XIC in early Xenopus embryos.
  • Analysis of dorsal axis specification and gene expression (siamois, Xnr3).
  • Reporter gene assays to evaluate beta-catenin activity.

Main Results:

  • I-mfa and XIC were found to inhibit the activity and DNA binding of XTcf3.
  • Ectopic expression of I-mfa or XIC disrupted dorsal axis formation in Xenopus embryos.
  • The expression of Tcf3/beta-catenin-regulated genes (siamois, Xnr3) was inhibited.
  • Beta-catenin's ability to activate Lef/Tcf-driven reporter constructs was reduced.

Conclusions:

  • I-mfa and XIC proteins can inhibit the HMG box transcription factor XTcf3.
  • These proteins play a role in regulating dorsal axis specification and gene expression in Xenopus.
  • I-mfa domain proteins may coordinate the Wnt signaling pathway and bHLH protein activities during development.

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