The Xenopus Wnt effector XTcf-3 interacts with Groucho-related transcriptional repressors.
Roose, Jeroen; Molenaar, Miranda; Peterson, Josi; Hurenkamp, Jolanda; Brantjes, Helen; Moerer, Petra; van de Wetering, Marc; Destree, Olivier; Clevers, Hans
[Letter]
Nature.
395(6702):608-612, October 8, 1998.
(Format: HTML)
Tcf/Lef transcription factors mediate signalling from Wingless/Wnt proteins by recruiting Armadillo/beta-catenin as a transcriptional co-activator [1-7]. However, studies of Drosophila, Xenopus and Caenorhabditis elegans have indicated that Tcf factors may also be transcriptional repressors [6,8-13]. Here we show that Tcf factors physically interact with members of the Groucho family of transcriptional repressors. In transient transfection assays, the Xenopus Groucho homologue XGrg-4 inhibited activation of transcription of synthetic Tcf reporter genes. In contrast, the naturally truncated Groucho-family member XGrg-5 enhanced transcriptional activation. Injection of XGrg-4 into Xenopus embryos repressed transcriptional of Siamois and Xnr-3, endogenous targets of beta-catenin-Tcf. Dorsal injection of XGrg-4 had a ventralizing effect on Xenopus embryos. Secondary-axis formation induced by a dominant-positive Armadillo-Tcf fusion protein was inhibited by XGrg-4 and enhanced by XGrg-5. These data indicate that expression of Tcf target genes is regulated by a balance between Armadillo and Groucho.
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