title: Xenopus nuclear factor 7 (xnf7) possesses an NLS that functions efficiently in both oocytes and embryos.
abstract: Xenopus nuclear factor 7 (xnf7) is a nuclear phosphoprotein that is encoded by a member of a novel zinc finger gene family and likely functions as a transcription factor. It possesses a nuclear localization signal (NLS) similar to the bipartite basic NLS of nucleoplasmin, but unlike nucleoplasmin, which re-enters nuclei immediately after fertilization, xnf7 remains cytoplasmic until the mid-blastula transition (MBT). We have measured the accumulation of injected labeled xnf7 protein or protein produced from synthetic xnf7 transcripts in the oocyte nuclei (GV). The data show that the NLS of xnf7 functions efficiently in oocytes. Mutations in either of the bipartite basic domains of the xnf7 NLS inhibit nuclear accumulation, while mutations in the spacer sequences have no effect. The xnf7 NLS linked to pyruvate kinase directs the efficient accumulation of this protein into nuclei of early embryos prior to the MBT. These data suggest that retention of the xnf7 protein during development is the result of a mechanism that interferes with the xnf7 NLS function.
authors.affiliation: Department of Molecular Genetics, University of Texas M. D. Anderson Cancer Center, Houston 77030.
authors.forename: X
authors.initials: X
authors.lastname: Li
authors.forename: L D
authors.initials: LD
authors.lastname: Etkin
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D002467:Cell Nucleus / Q000378:metabolism*; D004268:DNA-Binding Proteins; D004527:Egg Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000378:metabolism*; D005260:Female; D005796:Genes; D008969:Molecular Sequence Data; D005810:Multigene Family; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism*; D010750:Phosphoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017354:Point Mutation; D021382:Protein Sorting Signals / Q000235:genetics / Q000378:metabolism*; D011770:Pyruvate Kinase / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000196:embryology / Q000235:genetics / Q000378:metabolism*; D016335:Zinc Fingers / Q000235:genetics
chemical_list: D004268:DNA-Binding Proteins; D004527:Egg Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; D029867:Xenopus Proteins; C071551:XNF7 protein, Xenopus; D011770:Pyruvate Kinase