Cell Cycle-Dependent Phosphorylation of Nucleoporins and Nuclear Pore Membrane Protein Gp210

Favreau, Catherine; Worman, Howard J.; Wozniak, Richard W.; Frappier, Thierry; Courvalin, Jean-Claude

doi:10.1021/bi9600660

Cited by 148 publications

(105 citation statements)

References 60 publications

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“…Gp210, a pore membrane protein known to be a major constituent of the lumenal ring, is apparently recruited later in NPC assembly (11). Gp210 is also hyperphosphorylated at the early stages of mitosis, and this modification may be important to initiate the mitotic disassembly of the NPC and nuclear envelope (12). Although Gp210 is a major protein in metazoan NPCs, the lack of an orthologue in yeast further suggests a possible role for Gp210 in NPC disassembly, as there is no NE disassembly step during yeast mitosis.…”

Section: The Pore Membrane Domain and Formationmentioning

confidence: 99%

The Nuclear Pore Complex as a Transport Machine

Rout

Aitchison

2001

Journal of Biological Chemistry

255

191

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Nucleocytoplasmic Transport and the NuclearPore Complex Unlike their prokaryotic counterparts, eukaryotic cells separate the nuclear synthesis of DNA and RNA from cytoplasmic protein synthesis with a barrier termed the nuclear envelope (NE).1 The NE is perforated by large proteinaceous assemblies, called nuclear pore complexes (NPCs), which act as the sole gatekeepers controlling the exchange of material between the two locales (reviewed in Ref. 1). NPCs are freely permeable to small molecules (such as water and ions), but they restrict the movement of larger molecules (such as proteins and RNAs) across the NE. To overcome this barrier, macromolecules carry specific signals that allow them to access the nucleocytoplasmic transport machinery of the cell. In this way the cell ensures that only selected macromolecules can travel between the nucleus and cytoplasm (reviewed in Ref. 2).Operationally, NPCs are composed of proteins called nucleoporins (or Nups) forming the stationary phase for nucleocytoplasmic exchange, whereas the mobile phase consists of soluble transport factors and their cargoes. As nucleocytoplasmic transport is driven by a series of specific interactions between components of both phases, it is frequently difficult to determine which proteins are permanent constituents of the NPC. Nevertheless, to understand how transport occurs, we must characterize the players in both phases and understand how their interplay leads to the coordinated vectorial exchange of macromolecules across the NE. In this review we focus on recent results that shed light on how some of these proteins interact to contribute to the elaborate NPC architecture and its function as a transport machine. Architecture of the NPCNPCs from different organisms share a common fundamental architecture (3). These similarities likely provide clues as to the key features common to a functioning transport machine. The NPC is a large octagonally symmetric cylindrical structure. In yeast it estimated to be ϳ50 MDa, whereas in metazoans it is over twice this mass (3,4). Given that a ribosome at 4 MDa contains ϳ80 proteins, it might be expected that the NPC would contain hundreds of different nucleoporins. However, it has recently been shown that the yeast NPC contains only ϳ30 different proteins and the vertebrate NPC contains perhaps a few more (5). This raises the question of how such a large complex can be constructed from so few component parts. The answer appears to lie in the symmetry of the structure (Figs. 1-3). The NPC is comprised of a cylindrical core from which numerous peripheral filaments project toward the nucleus and cytoplasm (reviewed in Ref. 6) (Figs. 1 and 2). The remarkable symmetry of the NPC is most apparent in the central core. Not only is it composed of eight identical spokes, but each spoke is also seemingly mirror symmetrical both in a plane parallel to the NE and in a perpendicular plane running through the cylindrical axis. As predicted from this symmetry, all nucleoporins examined thus far are present in multiple...

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Section: The Pore Membrane Domain and Formationmentioning

confidence: 99%

The Nuclear Pore Complex as a Transport Machine

Rout

Aitchison

2001

Journal of Biological Chemistry

255

191

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“…Several nuclear pore components have been shown to become either phosphorylated or hyperphosphorylated during mitosis (Macaulay et al, 1995;Favreau et al, 1996). The lag between the entry of Cdc2-cyclin B and the first signs of increased passive permeability seems relatively lengthy.…”

Section: Accumulation In the Nucleusmentioning

confidence: 99%

Localization and Dynamics of Cdc2-Cyclin B during Meiotic Reinitiation in Starfish Oocytes

Terasaki

Okumura

Hinkle

et al. 2003

MBoC

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The Cdc2-cyclin B kinase has a central role in regulating the onset of M phase. In starfish oocytes, Cdc2-cyclin B begins to be activated ϳ10 min after application of maturation hormone, followed by accumulation in the nucleus then nuclear envelope breakdown. By immunofluorescence and by expressing a green fluorescent (GFP) chimera of cyclin B, we find that cyclin B is present in aggregates in the cytoplasm of immature oocytes. The aggregates disperse at ϳ10 min, suggesting that the dispersal is closely related to the activation of the kinase. Using cyclin B-GFP, the dispersion begins from the region containing the centrosomes. Extractability of Cdc2-cyclin B changes with similar kinetics during maturation. Active Cdc25 phosphatase released Cdc2-cyclin B from the detergent-insoluble fraction independently of its phosphatase activity. Live cell imaging also showed that Cdc2-cyclin B begins to accumulate in the nucleus before changes in nuclear pore permeability, consistent with Cdc2-cyclin B-induced disassembly of the pores. INTRODUCTIONThe Cdc2/cdk1 kinase triggers the onset of M phase (Nurse, 1990). Activation of Cdc2 requires association with cyclin B and dephosphorylation of Thr 14 and Tyr 15 on Cdc2; the phosphorylation state is governed by the relative activities of Wee1 family kinases and Cdc25 phosphatase (reviewed in Lew and Kornbluth, 1996). Inactive Cdc2-cyclin B is present in the cytoplasm during interphase and after it is activated, accumulates in the nucleus where it phosphorylates multiple targets to cause nuclear envelope breakdown (Pines and Hunter, 1991;Ookata et al., 1992).There are still many aspects of this system that are not well understood. The pathway leading to activation is different in different organisms and has not been established except in starfish (Okumura et al., 2002). Phosphorylation of cyclin is probably involved in the regulation of nuclear entry (Li et al., 1997;Hagting et al., 1998;Toyoshima et al., 1998;Yang et al., 1998) but may have other roles as well (Peter et al., 2002).Another subject of uncertainty regards Cdc2-cyclin B localization in the cytoplasm and its possible associations with other molecules in the cytoplasm. There are several indications that inactive Cdc2-cyclin B is not free to diffuse in the cytosol but instead, is associated with other molecules or intracellular structures and undergoes changes in associations when it becomes activated. Among various reports, Picard and Peaucellier (1998) observed cyclin B in vesiclelike structures in starfish oocytes, Westendorf et al. (1989) found evidence for cyclin B aggregates in immature clam oocytes, and Lee and Kirschner (1996) found evidence for a binding inhibitor of Cdc2-cyclin B that is associated with membranes. More recently, inactive Cdc2-cyclin B was found to be associated with annulate lamellae in immature Xenopus oocytes (Beckhelling et al., 2003).Current techniques for localization are subject to limitations of various kinds. The use of green fluorescent protein (GFP) chimeras is promising because loc...

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“…Both processes seem to require phosphorylation events carried out by a cyclin-dependent kinase (CDK) and its regulatory protein, cyclin B (CYCB). The CDK/CYCB complex promotes PPB disassembly in plants (Hush et al, 1996), the depolymerization of nuclear lamins in vertebrates, Caenorhabditis elegans, and yeast (Nigg, 1992;Daigle et al, 2001;Galy et al, 2008), and the disassembly of nucleoporins in animal cells (Macaulay et al, 1995;Favreau et al, 1996). This mitotic phosphorylation releases lamins and some nuclear membrane and nuclear pore proteins, enabling progression through the NE breakdown.…”

Section: Preprophase/prophasementioning

confidence: 99%