Distinct beta-catenins mediate adhesion and signalling functions in C. elegans.
In flies and vertebrates, Armadillo/beta-catenin forms a complex with Tcf/Lef-1 transcription factors, serving as an essential co-activator to mediate Wnt signalling. It also associates with cadherins to mediate adhesion. In Caenorhabditis elegans, three putative beta-catenin homologues have been identified: WRM-1, BAR-1 and HMP-2. WRM-1 and the Tcf homologue POP-1 mediate Wnt signalling by a mechanism that has challenged current views of the Wnt pathway. Here we show that BAR-1 is the only beta-catenin homologue that interacts directly with POP-1. BAR-1 mediates Wnt signalling by forming a BAR-1/POP-1 bipartite transcription factor that activates expression of Wnt target genes such as the Hox gene mab-5. HMP-2 is the only beta-catenin homologue that interacts with the single cadherin of C. elegans, HMR-1. We conclude that a canonical Wnt pathway exists in C. elegans. Furthermore, our analysis shows that the functions of C. elegans beta-catenins in adhesion and in signalling are performed by separate proteins.
Korswagen
H C
HC
Department of Immunology, University Medical Center Utrecht, The Netherlands. R.Korswagen@lab.azu.nl
Herman
M A
MA
Clevers
H C
HC
D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins; D002448:Cell Adhesion; D002460:Cell Line; D003001:Cloning, Molecular; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D017238:Genes, Helminth; D017930:Genes, Reporter; D015801:Helminth Proteins / Q000378:metabolism; D006609:High Mobility Group Proteins / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D015398:Signal Transduction; D015534:Trans-Activators; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D020798:Two-Hybrid System Techniques; D051153:Wnt Proteins; D029961:Zebrafish Proteins; D051176:beta Catenin
C495267:CTNNB1 protein, mouse; D029742:Caenorhabditis elegans Proteins; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D015801:Helminth Proteins; D006609:High Mobility Group Proteins; D018398:Homeodomain Proteins; C081538:Mab-5 protein, C elegans; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D051153:Wnt Proteins; D029961:Zebrafish Proteins; C115014:bar-1 protein, C elegans; D051176:beta Catenin; C096787:pop-1 protein, C elegans