Abstract
We describe a novel basic leucine zipper transcription factor, XXBP-1, which interacts with BMP-4 in a positive feedback loop. It is a maternal factor and is zygotically expressed in the dorsal blastopore lip and ventral ectoderm with the exception of the prospective neural plate during gastrulation. Overexpression of XXBP-1 leads to ventralization of early embryos as described for BMP-4, and inhibits neuralization of dissociated ectoderm. Consistent with mediating BMP signaling, we show that the ectopic expression of XXBP-1 recovers the expression of epidermal keratin and reverses the dorsalization imposed by truncated BMP receptor type I, indicating that it may act downstream of the BMP receptor. Its effects can be partially mimicked by a fusion construct containing the VP16 activator domain and the XXBP-1 DNA-binding domain. In contrast, fusing the DNA-binding domain to the even-skipped repressor domain leads to upregulation of the neural markers NCAM and nrp-1 in animal cap assay. Taken together, the results suggest a role for XXBP-1 in the control of neural differentiation, possibly as an activator.
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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Animals
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Bone Morphogenetic Protein 4
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Bone Morphogenetic Protein Receptors, Type I
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Bone Morphogenetic Proteins / genetics
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Bone Morphogenetic Proteins / metabolism*
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Cell Differentiation / physiology
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism*
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Ectoderm / physiology
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Embryo, Nonmammalian / cytology
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Embryo, Nonmammalian / radiation effects
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Embryonic Induction / physiology
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Epidermis / embryology
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Epidermis / metabolism
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Female
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Gene Expression Regulation, Developmental
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Genes, Dominant
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Genetic Markers
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Homeodomain Proteins / genetics
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Homeodomain Proteins / metabolism
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Keratins / genetics
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Keratins / metabolism
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Leucine Zippers
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MSX1 Transcription Factor
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Mesoderm / physiology
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Molecular Sequence Data
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Neurons / metabolism
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism
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Receptors, Growth Factor / genetics
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Receptors, Growth Factor / metabolism
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Regulatory Factor X Transcription Factors
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Sequence Homology, Amino Acid
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Signal Transduction
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Trans-Activators / genetics
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Trans-Activators / metabolism
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Transcription Factors / genetics
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Transcription Factors / metabolism*
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Ultraviolet Rays / adverse effects
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Xenopus / embryology
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Xenopus / metabolism*
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Xenopus Proteins / genetics
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Xenopus Proteins / metabolism*
Substances
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Bone Morphogenetic Protein 4
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Bone Morphogenetic Proteins
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DNA-Binding Proteins
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Genetic Markers
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Homeodomain Proteins
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MSX1 Transcription Factor
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MSX1 protein, Xenopus
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Receptors, Growth Factor
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Regulatory Factor X Transcription Factors
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Trans-Activators
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Transcription Factors
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Xenopus Proteins
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bmp4 protein, Xenopus
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Keratins
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Protein Serine-Threonine Kinases
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Bone Morphogenetic Protein Receptors, Type I