Functional aspects of B-Myb in early Xenopus development.
The gene encoding Xenopus B-Myb (XB-Myb), a protein structurally related to the nuclear protooncogene product c-Myb, is expressed in early Xenopus embryogenesis. We report on developmental alterations in the nucleocytoplasmic distribution and phosphorylation of XB-Myb in Xenopus oocytes and embryos, as well as on a negative regulatory role of the carboxyl terminus in sequence specific DNA binding. In growing oocytes and early embryonic stages the protein is primarily located in the nucleus; in the full-grown oocyte, however, it remains sequestered in the cytoplasmic compartment. Upon meiotic maturation of the oocyte, XB-Myb becomes hyperphosphorylated. Oocyte/egg isolates of XB-Myb are inhibited in their specific DNA binding activity; truncation of the carboxyl terminal region relieves this block in nucleic acid recognition. Furthermore, we have used overexpression of XB-Myb in Xenopus embryos by means of mRNA injection as an assay for gene function in vivo. Overexpression of full-length XB-Myb, not of the carboxyl terminal deletion mutant, results in an altered morphology of lateral plate mesoderm.
Bouwmeester
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T
Otto-Warburg-Laboratorium Max-Planck-Institut für Molekulare Genetik, Berlin, Germany.
van Wijk
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I
Wedlich
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D
Pieler
T
T
D000818:Animals; D015153:Blotting, Western; D018797:Cell Cycle Proteins; D002467:Cell Nucleus / Q000378:metabolism; D016384:Consensus Sequence; D003593:Cytoplasm / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000378:metabolism; D016259:Genes, myc; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008540:Meiosis; D009865:Oocytes / Q000378:metabolism; D010766:Phosphorylation; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional; D015534:Trans-Activators; D014157:Transcription Factors / Q000378:metabolism*; D014981:Xenopus / Q000196:embryology* / Q000235:genetics
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D016271:Proto-Oncogene Proteins c-myc; D015534:Trans-Activators; D014157:Transcription Factors; D004247:DNA