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Functional domains of axin. Importance of the C terminus as an oligomerization domain.

To understand the mechanism of how Axin acts as an inhibitory molecule in the Wnt pathway, we generated a series of mutated forms of Axin. From the binding experiments, we defined the domains of Axin that bind glycogen synthase kinase-3beta (GSK-3beta) and beta-catenin. We also examined the ability of each Axin mutant to inhibit lymphoid enhancer factor-1 (Lef-1) reporter activity in a cell line expressing high levels of beta-catenin. Axin mutants that did not bind GSK-3beta or beta-catenin were ineffective in suppressing Lef-1 reporter activity. Binding GSK-3beta and beta-catenin was not sufficient for this inhibitory effect of Axin. Axin mutants with C-terminal truncations lacked the ability to inhibit Lef-1 reporter activity, even though they bound GSK-3beta and beta-catenin. The C-terminal region was required for binding to Axin itself. Substitution of the C-terminal region with an unrelated dimerizing molecule, the retinoid X receptor restored its inhibitory effect on Lef-1-dependent transcription. The oligomerization of Axin through its C terminus is important for its function in regulation of beta-catenin-mediated response.

Pubmed ID: 10318824


  • Sakanaka C
  • Williams LT


The Journal of biological chemistry

Publication Data

May 14, 1999

Associated Grants


Mesh Terms

  • Animals
  • Axin Protein
  • Binding Sites
  • COS Cells
  • Calcium-Calmodulin-Dependent Protein Kinases
  • Colonic Neoplasms
  • Cytoskeletal Proteins
  • DNA-Binding Proteins
  • Glycogen Synthase Kinase 3
  • Glycogen Synthase Kinases
  • Humans
  • Lymphoid Enhancer-Binding Factor 1
  • Mice
  • Mutagenesis, Site-Directed
  • Protein Conformation
  • Proteins
  • Repressor Proteins
  • Structure-Activity Relationship
  • Trans-Activators
  • Transcription Factors
  • Transcription, Genetic
  • Tumor Cells, Cultured
  • beta Catenin