title: Localization of Pom121 to the inner nuclear membrane is required for an early step of interphase nuclear pore complex assembly.
abstract: The nuclear pore complex (NPC) is a large protein assembly that mediates molecular trafficking between the cytoplasm and the nucleus. NPCs assemble twice during the cell cycle in metazoans: postmitosis and during interphase. In this study, using small interfering RNA (siRNA) in conjunction with a cell fusion-based NPC assembly assay, we demonstrated that pore membrane protein (Pom)121, a vertebrate-specific integral membrane nucleoporin, is indispensable for an early step in interphase NPC assembly. Functional domain analysis of Pom121 showed that its nuclear localization signals, which bind to importin β via importin α and likely function with RanGTP, play an essential role in targeting Pom121 to the interphase NPC. Furthermore, a region of Pom121 that interacts with the inner nuclear membrane (INM) and lamin B receptor was found to be crucial for its NPC targeting. Based on these findings and on evidence that Pom121 localizes at the INM in the absence of a complete NPC structure, we propose that the nuclear migration of Pom121 and its subsequent interaction with INM proteins are required to initiate interphase NPC assembly. Our data also suggest, for the first time, the importance of the INM as a seeding site for "prepores" during interphase NPC assembly.
authors.affiliation: Cellular Dynamics Laboratory, Riken Advanced Science Institute, Saitama 351-0198, Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Funakoshi
authors.forename: Michaela
authors.initials: M
authors.lastname: Clever
authors.forename: Ai
authors.initials: A
authors.lastname: Watanabe
authors.forename: Naoko
authors.initials: N
authors.lastname: Imamoto
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000595:Amino Acid Sequence; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007399:Interphase / Q000502:physiology*; D028884:Karyopherins / Q000378:metabolism; D008561:Membrane Fusion / Q000502:physiology; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009685:Nuclear Envelope / Q000378:metabolism*; D022022:Nuclear Pore / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D020931:ran GTP-Binding Protein / Q000378:metabolism
chemical_list: D028884:Karyopherins; D008562:Membrane Glycoproteins; C094157:POM121 protein, human; D011993:Recombinant Fusion Proteins; D020931:ran GTP-Binding Protein