title: Nuclear transit of human zipcode-binding protein IMP1.
abstract: The human IMPs (insulin-like growth factor II mRNA-binding proteins) belong to a vertebrate zipcode-binding protein family consisting of two RNA recognition motifs and four K homology domains and have been implicated in cytoplasmic mRNA localization, turnover and translational control. In the present study, we show that IMP1 is capable of translocating into nuclei of NIH 3T3 fibroblasts and its immunoreactivity is present in the nuclei of human spermatogenic cells. IMP1 does not contain a simple import signal, but nuclear entry was facilitated by disruption of RNA binding and cytoplasmic granule formation. IMP1 contains two NESs (nuclear export signals) within the RNA-binding K homology domains 2 and 4. The former is a leucine-rich leptomycin B-sensitive NES, whereas the latter is a leptomycin B-insensitive NES. Taken together, these results indicate that IMP1 may attach to its target mRNAs in the nucleus and thereby define the cytoplasmic fate of the transcripts.
authors.affiliation: Institute of Molecular Biology, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Jacob
authors.initials: J
authors.lastname: Nielsen
authors.forename: Sidsel K
authors.initials: SK
authors.lastname: Adolph
authors.forename: Ewa
authors.initials: E
authors.lastname: Rajpert-De Meyts
authors.forename: Jens
authors.initials: J
authors.lastname: Lykke-Andersen
authors.forename: Grete
authors.initials: G
authors.lastname: Koch
authors.forename: Jan
authors.initials: J
authors.lastname: Christiansen
authors.forename: Finn C
authors.initials: FC
authors.lastname: Nielsen
mesh_terms: D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D000818:Animals; D002467:Cell Nucleus / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D041681:NIH 3T3 Cells; D021382:Protein Sorting Signals; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: C406144:IGF2BP1 protein, human; D021382:Protein Sorting Signals; D016601:RNA-Binding Proteins