Abstract
The Wnt/beta-catenin signaling pathway regulates many developmental processes by modulating gene expression. Wnt signaling induces the stabilization of cytosolic beta-catenin, which then associates with lymphoid enhancer factor and T-cell factor (LEF-1/TCF) to form a transcription complex that activates Wnt target genes. Previously, we have shown that a specific mitogen-activated protein (MAP) kinase pathway involving the MAP kinase kinase kinase TAK1 and MAP kinase-related Nemo-like kinase (NLK) suppresses Wnt signaling. In this study, we investigated the relationships among NLK, beta-catenin, and LEF-1/TCF. We found that NLK interacts directly with LEF-1/TCF and indirectly with beta-catenin via LEF-1/TCF to form a complex. NLK phosphorylates LEF-1/TCF on two serine/threonine residues located in its central region. Mutation of both residues to alanine enhanced LEF-1 transcriptional activity and rendered it resistant to inhibition by NLK. Phosphorylation of TCF-4 by NLK inhibited DNA binding by the beta-catenin-TCF-4 complex. However, this inhibition was abrogated when a mutant form of TCF-4 was used in which both threonines were replaced with valines. These results suggest that NLK phosphorylation on these sites contributes to the down-regulation of LEF-1/TCF transcriptional activity.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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Amino Acid Substitution
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Cells, Cultured
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Cytoskeletal Proteins / genetics
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Cytoskeletal Proteins / metabolism*
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism*
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Down-Regulation
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Humans
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Intracellular Signaling Peptides and Proteins
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Lymphoid Enhancer-Binding Factor 1
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MAP Kinase Kinase Kinases / genetics
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MAP Kinase Kinase Kinases / metabolism
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Mitogen-Activated Protein Kinases / genetics
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Mitogen-Activated Protein Kinases / metabolism*
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Molecular Sequence Data
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Mutation
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Phosphorylation
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Protein Serine-Threonine Kinases
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Proto-Oncogene Proteins / metabolism
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Sequence Homology, Amino Acid
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Serine / metabolism
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Signal Transduction
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TCF Transcription Factors
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Threonine / metabolism
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Trans-Activators / genetics
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Trans-Activators / metabolism*
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Transcription Factor 7-Like 2 Protein
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Transcription Factors / genetics
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Transcription Factors / metabolism*
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Two-Hybrid System Techniques
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Valine
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Wnt Proteins
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Zebrafish Proteins*
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beta Catenin
Substances
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CTNNB1 protein, human
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Cytoskeletal Proteins
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DNA-Binding Proteins
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Intracellular Signaling Peptides and Proteins
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LEF1 protein, human
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Lymphoid Enhancer-Binding Factor 1
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Proto-Oncogene Proteins
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TCF Transcription Factors
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TCF7L2 protein, human
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Trans-Activators
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Transcription Factor 7-Like 2 Protein
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Transcription Factors
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Wnt Proteins
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Zebrafish Proteins
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beta Catenin
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Threonine
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Serine
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NLK protein, human
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Protein Serine-Threonine Kinases
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Mitogen-Activated Protein Kinases
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MAP Kinase Kinase Kinases
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MAP kinase kinase kinase 7
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Valine