title: Nuclear transport of Wilms' tumour protein Wt1 involves importins α and β.
abstract: OBJECTIVE
  Wilms' tumour protein, Wt1, is a zinc finger molecule, which is required for normal embryonic development. Mutations of the WT1 gene can give rise to childhood cancer of the kidneys. Different Wt1 isoforms exist, which function either as transcription factors or have a presumed role in mRNA processing. Previous studies suggested that Wt1 undergoes nucleocytoplasmic shuttling, and cytoplasmic Wt1 was higher in malignant than in normal cells. The aim of this study was to analyse the molecular pathways along which Wt1 shuttles between the cytoplasm and nucleus.
  
  
  METHODS
  Interaction of Wt1 protein with various importin α subtypes and importin β was assessed in pull-down assays and co-immunoprecipitation experiments. Nuclear localisation signals (NLS) were identified by combining site-directed mutagenesis with subcellular immunodetection of the transfected Wt1 variants.
  
  
  RESULTS
  Wt1(+/-KTS) proteins were found to interact with importin α1 and importin β in vitro and in living cells in vivo. A NLS that was necessary and sufficient for nuclear import could be mapped to the third Wt1 zinc finger. Mutation of this NLS strongly weakened binding of Wt1 to importins.
  
  
  CONCLUSIONS
  Nuclear translocation of Wilms' tumour protein involves importins α and β, and a NLS in the third zinc finger.
authors.affiliation: Institut für Physiologie, Zentrum für Medizinische Struktur- und Zellbiologie, Universität zu Lübeck, Lübeck, Germany.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Depping
authors.forename: Susann G
authors.initials: SG
authors.lastname: Schindler
authors.forename: Charlotte
authors.initials: C
authors.lastname: Jacobi
authors.forename: Karin M
authors.initials: KM
authors.lastname: Kirschner
authors.forename: Holger
authors.initials: H
authors.lastname: Scholz
mesh_terms: D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D002467:Cell Nucleus / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D047468:Immunoprecipitation; D008969:Molecular Sequence Data; D015398:Signal Transduction; D025721:WT1 Proteins / Q000378:metabolism*; D016335:Zinc Fingers; D028901:alpha Karyopherins / Q000378:metabolism*; D028961:beta Karyopherins / Q000378:metabolism*
chemical_list: D025721:WT1 Proteins; D028901:alpha Karyopherins; D028961:beta Karyopherins