Abstract
XTcf-3 is an HMG box transcription factor that mediates Xenopus dorsal-ventral axis formation. As a Wnt pathway effector, XTcf-3 interacts with beta-catenin and activates the expression of the dorsal organizing gene siamois, while in the absence of beta-catenin, XTcf-3 functions as a transcriptional repressor. We show that XTcf-3 contains amino- and carboxy-terminal repressor domains and have identified a Xenopus member of the C-terminal Binding Protein family of transcriptional co-repressors (XCtBP) as the C-terminal co-repressor. We show that two XCtBP binding sites near the XTcf-3 carboxy-terminus are required for the interaction of XTcf-3 and XCtBP and for the transcriptional repression mediated by the XTcf-3 carboxy-terminal domain. By fusing the GAL4 activation domain to XCtBP we have generated an antimorphic protein, XCtBP/G4A, that activates siamois transcription through an interaction with endogenous XTcf-3. Ectopic expression of XCtBP/G4A demonstrates that XCtBP functions in the regulation of head and notochord development. Our data support a role for XCtBP as a co-repressor throughout Xenopus development and indicate that XCtBP/G4A will be a useful tool in determining how XCtBP functions in various developmental processes.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Sequence
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Animals
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Binding Sites
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Carrier Proteins / genetics*
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Carrier Proteins / metabolism*
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Conserved Sequence
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Embryo, Nonmammalian
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Gene Expression Regulation, Developmental*
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HMGB Proteins*
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High Mobility Group Proteins / genetics
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High Mobility Group Proteins / metabolism
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Homeodomain Proteins / genetics
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Homeodomain Proteins / metabolism
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Hybrid Cells
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Lymphoid Enhancer-Binding Factor 1
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Membrane Proteins / genetics*
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Membrane Proteins / metabolism*
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Molecular Sequence Data
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Recombinant Proteins / genetics
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Recombinant Proteins / metabolism
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Repressor Proteins / genetics
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Repressor Proteins / metabolism
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Sequence Homology, Amino Acid
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TCF Transcription Factors
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Thyroid Hormone-Binding Proteins
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Thyroid Hormones*
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Transcription Factor 3
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Transcription Factor 7-Like 1 Protein
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Transcription Factors / genetics*
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Transcription Factors / metabolism
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Transcription, Genetic
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Xenopus / embryology*
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Xenopus / genetics
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Xenopus Proteins*
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Yeasts / genetics
Substances
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Carrier Proteins
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HMGB Proteins
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High Mobility Group Proteins
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Homeodomain Proteins
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Lef1 protein, Xenopus
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Lymphoid Enhancer-Binding Factor 1
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Membrane Proteins
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Recombinant Proteins
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Repressor Proteins
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SIA1 protein, Xenopus
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TCF Transcription Factors
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Tcf3 protein, Xenopus
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Thyroid Hormones
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Transcription Factor 3
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Transcription Factor 7-Like 1 Protein
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Transcription Factors
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Xenopus Proteins