Article

Molecular Architecture of the Transport Channel of the Nuclear Pore Complex

Laboratory of Cell Biology, Howard Hughes Medical Institute, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
Cell (Impact Factor: 32.24). 10/2011; 147(3):590-602. DOI: 10.1016/j.cell.2011.09.034
Source: PubMed

ABSTRACT

The nuclear pore complex encloses a central channel for nucleocytoplasmic transport, which is thought to consist of three nucleoporins, Nup54, Nup58, and Nup62. However, the structure and composition of the channel are elusive. We determined the crystal structures of the interacting domains between these nucleoporins and pieced together the molecular architecture of the mammalian transport channel. Located in the channel midplane is a flexible Nup54⋅Nup58 ring that can undergo large rearrangements yielding diameter changes from ∼20 to ∼40 nm. Nup62⋅Nup54 triple helices project alternately up and down from either side of the midplane ring and form nucleoplasmic and cytoplasmic entries. The channel consists of as many as 224 copies of the three nucleoporins, amounting to a molar mass of 12.3 MDa and contributing 256 phenylalanine-glycine repeat regions. We propose that the occupancy of these repeat regions with transport receptors modulates ring diameter and transport activity.

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    • "Indeed, we note that O-GlcNAc is found on over 18 Nups but is most abundant on peripheral Nups (Supplementary Figure S8 and Table S1). O-GlcNAc on Nups is predominantly observed in regions that are not structurally defined except for Nup62, where residue T376 is in an a-helical domain (Solmaz et al., 2011), and Nup98, where residue T184 has been noted in a b-sheet structure (Ren et al., 2010). Accordingly, lower "
    [Show abstract] [Hide abstract] ABSTRACT: O-glycosylation of the nuclear pore complex (NPC) by O-linked N-acetylglucosamine (O-GlcNAc) is conserved within metazoans. Many nucleoporins (Nups) comprising the NPC are constitutively O-GlcNAcylated, but the functional role of this modification remains enigmatic. We show that loss of O-GlcNAc, induced by either inhibition of O-GlcNAc transferase (OGT) or deletion of the gene encoding OGT, leads to decreased cellular levels of a number of natively O-GlcNAcylated Nups. Loss of O-GlcNAc enables increased ubiquitination of these Nups and their increased proteasomal degradation. The decreased half-life of these deglycosylated Nups manifests in their gradual loss from the NPC and a downstream malfunction of the nuclear pore selective permeability barrier in both dividing and post-mitotic cells. These findings define a critical role of O-GlcNAc modification of the NPC in maintaining its composition and the function of the selectivity filter. The results implicate NPC glycosylation as a regulator of NPC function and reveal the role of conserved glycosylation of the NPC among metazoans. © The Author (2015). Published by Oxford University Press on behalf of Journal of Molecular Cell Biology, IBCB, SIBS, CAS. All rights reserved.
    Full-text · Article · Jun 2015 · Journal of Molecular Cell Biology
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    • "This subcomplex sits within the central channel of the NPC yet its role in nuclear transport remains somewhat controversial. One set of largely structural experiments shows that the complex acts as a variable ring allowing transit of molecules through the pore (Solmaz et al., 2011), while a set of transport assays in Xenopus oocytes reveals that the complex makes a minimal contribution to passive and active transport (Hulsmann et al., 2012). Currently, this depth of information for the role of the complex in Arabidopsis is not available, but it is clear from the lethality of certain nup62 alleles and the growth phenotypes of mutants in other members that it plays a major functional role. "
    [Show abstract] [Hide abstract] ABSTRACT: The nuclear pore complex (NPC) is a multisubunit protein conglomerate that facilitates movement of RNA and protein between the nucleus and cytoplasm. Relatively little is known regarding the influence of the Arabidopsis NPC on growth and development. Seedling development, flowering time, nuclear morphology, mRNA accumulation, and gene expression changes in Arabidopsis nucleoporin mutants were investigated. Nuclear export of mRNA is differentially affected in plants with defects in nucleoporins that lie in different NPC subcomplexes. This study reveals differences in the manner by which nucleoporins alter molecular and plant growth phenotypes, suggesting that nuclear pore subcomplexes play distinct roles in nuclear transport and reveal a possible feedback relationship between the expression of genes involved in nuclear transport.
    Full-text · Article · Aug 2014 · Journal of Experimental Botany
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    • "Nup93 is a known candidate, but there might be others yet to be identified. In a series of recent publications, the rat Nup62 complex was analyzed using a crystallographic approach (Melcák et al., 2007; Solmaz et al., 2011 Solmaz et al., , 2013 ). Using rather small, ∼4-to 10-kDa coiledcoil fragments of dimeric subassemblies, the authors hypothesized that the in vivo composition of the Nup58-Nup54-Nup62 complex would be 1:2:4, inconsistent with our data. "
    [Show abstract] [Hide abstract] ABSTRACT: The nuclear pore complex (NPC) regulates transport between nucleus and cytoplasm. Soluble cargo-protein complexes navigate through the pore by binding to phenylalanine-glycine (FG)-repeat proteins attached to the channel walls. The Nup62 complex contains the FG-repeat proteins Nup62, Nup54 and Nup58 and is located in the center of the NPC. The three proteins bind each other via conserved coiled-coil segments. To determine the stoichiometry of the Nup62 complex we undertook an in vitro study using gelfiltration and analytical ultracentrifugation. Our results reveal a 1:1:1 stoichiometry of the Nup62 complex, where Nup54 is central with direct binding to Nup62 and Nup58. At high protein concentration the complex forms larger assemblies while maintaining the Nup62:Nup54:Nup58 ratio. For the homologous Nsp1 complex from S. cerevisiae, we determine the same stoichiometry, indicating evolutionary conservation. Furthermore, we observe that eliminating one binding partner can result in the formation of complexes with non-canonical stoichiometry, presumably because unpaired coiled-coil elements tend to find a promiscuous binding partner. We suggest that these non-canonical stoichiometries observed in vitro are unlikely to be physiologically relevant.
    Full-text · Article · Feb 2014 · Molecular biology of the cell
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