Regulation of DNA binding activity and nuclear transport of B-Myb in Xenopus oocytes.
DNA binding activity and nuclear transport of B-Myb in Xenopus oocytes are negatively regulated. Two distinct sequence elements in the C-terminal portion of the protein are responsible for these different inhibitory activities. A C-terminal Xenopus B-Myb protein fragment inhibits the DNA binding activity of the N-terminal repeats in trans, indicating that intramolecular folding may result in masking of the DNA binding function. Xenopus B-Myb contains two separate nuclear localization signals (NLSs), which, in Xenopus oocytes, function only outside the context of the full-length protein. Fusion of an additional NLS to the full-length protein overcomes the inhibition of nuclear import, suggesting that masking of the NLS function rather than cytoplasmic anchoring is responsible for the negative regulation of Xenopus B-Myb nuclear transfer. During Xenopus embryogenesis, when inhibition of nuclear import is relieved, Xenopus B-myb is preferentially expressed in the developing nervous system and neural crest cells. Within the developing neural tube, Xenopus B-myb gene transcription occurs preferentially in proliferating, non-differentiated cells.
Humbert-Lan
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Institut für Biochemie und Molekulare Zellbiologie der Universität Göttingen, Humboldtallee 23, 37073 Göttingen, Germany.
Pieler
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D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D018797:Cell Cycle Proteins; D002467:Cell Nucleus / Q000378:metabolism*; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005260:Female; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D013329:Structure-Activity Relationship; D015534:Trans-Activators / Q000378:metabolism*; D014982:Xenopus laevis
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D010446:Peptide Fragments; D015534:Trans-Activators; D004247:DNA