title: The divergent Caenorhabditis elegans beta-catenin proteins BAR-1, WRM-1 and HMP-2 make distinct protein interactions but retain functional redundancy in vivo.
abstract: beta-Catenins function both in cell adhesion as part of the cadherin/catenin complex and in Wnt signal transduction as transcription factors. Vertebrates express two related proteins, beta-catenin and plakoglobin, while Drosophila has a single family member, Armadillo. Caenorhabditis elegans expresses three beta-catenin-related proteins, BAR-1, HMP-2, and WRM-1, which are quite diverged in sequence from each other and other beta-catenins. While BAR-1 and WRM-1 are known to act in Wnt-mediated processes, and HMP-2 acts in a complex with cadherin/alpha-catenin homologs, it is unclear whether all three proteins retain the other functions of beta-catenin. Here we show that BAR-1, like vertebrate beta-catenin, has redundant transcription activation domains in its amino- and carboxyl-terminal regions but that HMP-2 and WRM-1 also possess the ability to activate transcription. We show via yeast two-hybrid analysis that these three proteins display distinct patterns of protein interactions. Surprisingly, we find that both WRM-1 and HMP-2 can substitute for BAR-1 in C. elegans when expressed from the bar-1 promoter. Therefore, although their mutant phenotypes and protein interaction patterns strongly suggest that the functions of beta-catenin in other species have been segregated among three diverged proteins in C. elegans, these proteins still retain sufficient similarity to display functional redundancy in vivo.
authors.affiliation: Department of Biological Sciences, University of Maryland, Baltimore County, Baltimore, Maryland 21250.
authors.forename: L
authors.initials: L
authors.lastname: Natarajan
authors.forename: N E
authors.initials: NE
authors.lastname: Witwer
authors.forename: D M
authors.initials: DM
authors.lastname: Eisenmann
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000737:chemistry*; D029742:Caenorhabditis elegans Proteins; D002448:Cell Adhesion; D003598:Cytoskeletal Proteins / Q000737:chemistry* / Q000235:genetics*; D019992:Databases as Topic; D004305:Dose-Response Relationship, Drug; D008957:Models, Genetic; D009841:Oligonucleotides / Q000378:metabolism; D010641:Phenotype; D010802:Phylogeny; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D015534:Trans-Activators; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D020798:Two-Hybrid System Techniques; D051176:beta Catenin
chemical_list: D029742:Caenorhabditis elegans Proteins; D003598:Cytoskeletal Proteins; C442473:HMP-2 protein, C elegans; D009841:Oligonucleotides; D015534:Trans-Activators; D014157:Transcription Factors; C120104:WRM-1 protein, C elegans; C115014:bar-1 protein, C elegans; D051176:beta Catenin