title: Biochemical and structural characterization of β-catenin interactions with nonphosphorylated and CK2-phosphorylated Lef-1.
abstract: In the Wnt/β-catenin signaling pathway, β-catenin activates target genes through its interactions with the T-cell factor/lymphoid enhancer-binding factor (TCF/Lef) family of transcription factors. The crystal structures of complexes between the β-catenin armadillo domain and the Lef-1 N-terminal domain show that the overall conformation and many of the interactions are similar to other published structures of TCFs bound to β-catenin. However, a second salt bridge in other TCF-β-catenin structures is absent in the structure of β-catenin-Lef-1 complex, indicating that this feature is not obligatory for β-catenin binding. Casein kinase II (CK2) has been shown to act as a positive regulator of Wnt signaling, and Lef-1 is a substrate of CK2. In vitro phosphorylation of purified Lef-1 was used to examine the effect of CK2 on the interaction of Lef-1 with β-catenin. Mass spectrometry data show that CK2 phosphorylation of Lef-1 N-terminal domain results in a single phosphorylation site at Ser40. Isothermal titration calorimetry revealed that β-catenin binds to nonphosphorylated or CK2-phosphorylated Lef-1 with the same affinity, which is consistent with the absence of phospho-Ser40 interactions in the crystal structure of phosphorylated Lef-1 N-terminal domain bound to β-catenin. These data indicate that the effect of CK2 on the Wnt/β-catenin pathway does not appear to be at the level of the Lef-1-β-catenin interaction.
authors.affiliation: Department of Structural Biology, Stanford University School of Medicine,Stanford, CA 94305-5126, USA.
authors.forename: Jinglucy
authors.initials: J
authors.lastname: Sun
authors.forename: William I
authors.initials: WI
authors.lastname: Weis
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D047390:Casein Kinase II / Q000737:chemistry* / Q000378:metabolism*; D002478:Cells, Cultured; D006801:Humans; D051821:Lymphoid Enhancer-Binding Factor 1 / Q000737:chemistry* / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011485:Protein Binding; D011487:Protein Conformation; D025941:Protein Interaction Mapping; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D051820:TCF Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D051176:beta Catenin / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D051821:Lymphoid Enhancer-Binding Factor 1; D051820:TCF Transcription Factors; D051176:beta Catenin; D047390:Casein Kinase II