Artículos de revistas: "Nucleoporins (Nups)"

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Xu, Songli y Maureen A. Powers. "In vivo analysis of human nucleoporin repeat domain interactions". Molecular Biology of the Cell 24, n.º 8 (15 de abril de 2013): 1222–31. http://dx.doi.org/10.1091/mbc.e12-08-0585.

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The nuclear pore complex (NPC), assembled from ∼30 proteins termed nucleoporins (Nups), mediates selective nucleocytoplasmic trafficking. A subset of nucleoporins bear a domain with multiple phenylalanine–glycine (FG) motifs. As binding sites for transport receptors, FG Nups are critical in translocation through the NPC. Certain FG Nups are believed to associate via low-affinity, cohesive interactions to form the permeability barrier of the pore, although the form and composition of this functional barrier are debated. We used green fluorescent protein–Nup98/HoxA9 constructs with various numbers of repeats and also substituted FG domains from other nucleoporins for the Nup98 domain to directly compare cohesive interactions in live cells by fluorescence recovery after photobleaching (FRAP). We find that cohesion is a function of both number and type of FG repeats. Glycine–leucine–FG (GLFG) repeat domains are the most cohesive. FG domains from several human nucleoporins showed no interactions in this assay; however, Nup214, with numerous VFG motifs, displayed measurable cohesion by FRAP. The cohesive nature of a human nucleoporin did not necessarily correlate with that of its yeast orthologue. The Nup98 GLFG domain also functions in pore targeting through binding to Nup93, positioning the GLFG domain in the center of the NPC and supporting a role for this nucleoporin in the permeability barrier.

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2

Heinß, Nike, Mikhail Sushkin, Miao Yu y Edward A. Lemke. "Multifunctionality of F-rich nucleoporins". Biochemical Society Transactions 48, n.º 6 (18 de diciembre de 2020): 2603–14. http://dx.doi.org/10.1042/bst20200357.

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Nucleoporins (Nups) represent a range of proteins most known for composing the macromolecular assembly of the nuclear pore complex (NPC). Among them, the family of intrinsically disordered proteins (IDPs) phenylalanine-glycine (FG) rich Nups, form the permeability barrier and coordinate the high-speed nucleocytoplasmic transport in a selective way. Those FG-Nups have been demonstrated to participate in various biological processes besides nucleocytoplasmic transport. The high number of accessible hydrophobic motifs of FG-Nups potentially gives rise to this multifunctionality, enabling them to form unique microenvironments. In this review, we discuss the multifunctionality of disordered and F-rich Nups and the diversity of their localizations, emphasizing the important roles of those Nups in various regulatory and metabolic processes.

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3

Makio, Tadashi, Leslie H. Stanton, Cheng-Chao Lin, David S. Goldfarb, Karsten Weis y Richard W. Wozniak. "The nucleoporins Nup170p and Nup157p are essential for nuclear pore complex assembly". Journal of Cell Biology 185, n.º 3 (4 de mayo de 2009): 459–73. http://dx.doi.org/10.1083/jcb.200810029.

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We have established that two homologous nucleoporins, Nup170p and Nup157p, play an essential role in the formation of nuclear pore complexes (NPCs) in Saccharomyces cerevisiae. By regulating their synthesis, we showed that the loss of these nucleoporins triggers a decrease in NPCs caused by a halt in new NPC assembly. Preexisting NPCs are ultimately lost by dilution as cells grow, causing the inhibition of nuclear transport and the loss of viability. Significantly, the loss of Nup170p/Nup157p had distinct effects on the assembly of different architectural components of the NPC. Nucleoporins (nups) positioned on the cytoplasmic face of the NPC rapidly accumulated in cytoplasmic foci. These nup complexes could be recruited into new NPCs after reinitiation of Nup170p synthesis, and may represent a physiological intermediate. Loss of Nup170p/Nup157p also caused core and nucleoplasmically positioned nups to accumulate in NPC-like structures adjacent to the inner nuclear membrane, which suggests that these nucleoporins are required for formation of the pore membrane and the incorporation of cytoplasmic nups into forming NPCs.

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4

Flemming, Dirk, Phillip Sarges, Philipp Stelter, Andrea Hellwig, Bettina Böttcher y Ed Hurt. "Two structurally distinct domains of the nucleoporin Nup170 cooperate to tether a subset of nucleoporins to nuclear pores". Journal of Cell Biology 185, n.º 3 (4 de mayo de 2009): 387–95. http://dx.doi.org/10.1083/jcb.200810016.

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How individual nucleoporins (Nups) perform their role in nuclear pore structure and function is largely unknown. In this study, we examined the structure of purified Nup170 to obtain clues about its function. We show that Nup170 adopts a crescent moon shape with two structurally distinct and separable domains, a β-propeller N terminus and an α-solenoid C terminus. To address the individual roles of each domain, we expressed these domains separately in yeast. Notably, overexpression of the Nup170 C domain was toxic in nup170Δ cells and caused accumulation of several Nups in cytoplasmic foci. Further experiments indicated that the C-terminal domain anchors Nup170 to nuclear pores, whereas the N-terminal domain functions to recruit or retain a subset of Nups, including Nup159, Nup188, and Pom34, at nuclear pores. We conclude that Nup170 performs its role as a structural adapter between cytoplasmically oriented Nups and the nuclear pore membrane.

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5

Huang, Kai y Igal Szleifer. "Modeling the nucleoporins that form the hairy pores". Biochemical Society Transactions 48, n.º 4 (14 de agosto de 2020): 1447–61. http://dx.doi.org/10.1042/bst20190941.

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Sitting on the nuclear envelope, nuclear pore complexes (NPCs) control the molecular transport between the nucleus and the cytoplasm. Without definite open or close states, the NPC uses a family of intrinsically disordered nucleoporins called FG-Nups to construct a selective permeability barrier whose functional structure is unclear. Experimental advances have offered high-resolution molecular knowledge of the NPC scaffold and docking of the unfolded FG-Nups, however, the ‘hairy’ barrier structure still appears as blurred lobes even under the state-of-the-art microscopy. Without accurate experimental visualization, the molecular mechanism for the NPC-mediated transport remains a matter of debate. Modeling provides an alternative way to resolve this long-standing mystery. Here, we briefly review different methods employed in modeling the FG-Nups, arranging from all-atom molecular dynamics to mean-field theories. We discuss the advantage and limit of each modeling technique, and summarize the theoretical insights that, despite certain controversy, deepened our understanding of the hairy pore.

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Colussi, Claudia y Claudio Grassi. "Epigenetic Regulation of Neural Stem Cells: The Emerging Role of Nucleoporins". Stem Cells 39, n.º 12 (25 de agosto de 2021): 1601–14. http://dx.doi.org/10.1002/stem.3444.

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Abstract Nucleoporins (Nups) are components of the nuclear pore complex that, besides regulating nucleus-cytoplasmic transport, emerged as a hub for chromatin interaction and gene expression modulation. Specifically, Nups act in a dynamic manner both at specific gene level and in the topological organization of chromatin domains. As such, they play a fundamental role during development and determination of stemness/differentiation balance in stem cells. An increasing number of reports indicate the implication of Nups in many central nervous system functions with great impact on neurogenesis, neurophysiology, and neurological disorders. Nevertheless, the role of Nup-mediated epigenetic regulation in embryonic and adult neural stem cells (NSCs) is a field largely unexplored and the comprehension of their mechanisms of action is only beginning to be unveiled. After a brief overview of epigenetic mechanisms, we will present and discuss the emerging role of Nups as new effectors of neuroepigenetics and as dynamic platform for chromatin function with specific reference to the biology of NSCs.

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7

Holden, Jennifer M., Ludek Koreny, Samson Obado, Alexander V. Ratushny, Wei-Ming Chen, Jean-Mathieu Bart, Miguel Navarro et al. "Involvement in surface antigen expression by a moonlighting FG-repeat nucleoporin in trypanosomes". Molecular Biology of the Cell 29, n.º 9 (mayo de 2018): 1100–1110. http://dx.doi.org/10.1091/mbc.e17-06-0430.

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Components of the nuclear periphery coordinate a multitude of activities, including macromolecular transport, cell-cycle progression, and chromatin organization. Nuclear pore complexes (NPCs) mediate nucleocytoplasmic transport, mRNA processing, and transcriptional regulation, and NPC components can define regions of high transcriptional activity in some organisms at the nuclear periphery and nucleoplasm. Lineage-specific features underpin several core nuclear functions and in trypanosomatids, which branched very early from other eukaryotes, unique protein components constitute the lamina, kinetochores, and parts of the NPCs. Here we describe a phenylalanine-glycine (FG)-repeat nucleoporin, TbNup53b, that has dual localizations within the nucleoplasm and NPC. In addition to association with nucleoporins, TbNup53b interacts with a known trans-splicing component, TSR1, and has a role in controlling expression of surface proteins including the nucleolar periphery-located, procyclin genes. Significantly, while several nucleoporins are implicated in intranuclear transcriptional regulation in metazoa, TbNup53b appears orthologous to components of the yeast/human Nup49/Nup58 complex, for which no transcriptional functions are known. These data suggest that FG-Nups are frequently co-opted to transcriptional functions during evolution and extend the presence of FG-repeat nucleoporin control of gene expression to trypanosomes, suggesting that this is a widespread and ancient eukaryotic feature, as well as underscoring once more flexibility within nucleoporin function.

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8

Pulupa, Joan, Manas Rachh, Michael D. Tomasini, Joshua S. Mincer y Sanford M. Simon. "A coarse-grained computational model of the nuclear pore complex predicts Phe-Gly nucleoporin dynamics". Journal of General Physiology 149, n.º 10 (8 de septiembre de 2017): 951–66. http://dx.doi.org/10.1085/jgp.201711769.

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The phenylalanine-glycine–repeat nucleoporins (FG-Nups), which occupy the lumen of the nuclear pore complex (NPC), are critical for transport between the nucleus and cytosol. Although NPCs differ in composition across species, they are largely conserved in organization and function. Transport through the pore is on the millisecond timescale. Here, to explore the dynamics of nucleoporins on this timescale, we use coarse-grained computational simulations. These simulations generate predictions that can be experimentally tested to distinguish between proposed mechanisms of transport. Our model reflects the conserved structure of the NPC, in which FG-Nup filaments extend into the lumen and anchor along the interior of the channel. The lengths of the filaments in our model are based on the known characteristics of yeast FG-Nups. The FG-repeat sites also bind to each other, and we vary this association over several orders of magnitude and run 100-ms simulations for each value. The autocorrelation functions of the orientation of the simulated FG-Nups are compared with in vivo anisotropy data. We observe that FG-Nups reptate back and forth through the NPC at timescales commensurate with experimental measurements of the speed of cargo transport through the NPC. Our results are consistent with models of transport where FG-Nup filaments are free to move across the central channel of the NPC, possibly informing how cargo might transverse the NPC.

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9

Terry, Laura J. y Susan R. Wente. "Flexible Gates: Dynamic Topologies and Functions for FG Nucleoporins in Nucleocytoplasmic Transport". Eukaryotic Cell 8, n.º 12 (2 de octubre de 2009): 1814–27. http://dx.doi.org/10.1128/ec.00225-09.

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ABSTRACT The nuclear envelope is a physical barrier between the nucleus and cytoplasm and, as such, separates the mechanisms of transcription from translation. This compartmentalization of eukaryotic cells allows spatial regulation of gene expression; however, it also necessitates a mechanism for transport between the nucleus and cytoplasm. Macromolecular trafficking of protein and RNA occurs exclusively through nuclear pore complexes (NPCs), specialized channels spanning the nuclear envelope. A novel family of NPC proteins, the FG-nucleoporins (FG-Nups), coordinates and potentially regulates NPC translocation. The extensive repeats of phenylalanine-glycine (FG) in each FG-Nup directly bind to shuttling transport receptors moving through the NPC. In addition, FG-Nups are essential components of the nuclear permeability barrier. In this review, we discuss the structural features, cellular functions, and evolutionary conservation of the FG-Nups.

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10

Sachdev, Ruchika, Cornelia Sieverding, Matthias Flötenmeyer y Wolfram Antonin. "The C-terminal domain of Nup93 is essential for assembly of the structural backbone of nuclear pore complexes". Molecular Biology of the Cell 23, n.º 4 (15 de febrero de 2012): 740–49. http://dx.doi.org/10.1091/mbc.e11-09-0761.

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Nuclear pore complexes (NPCs) are large macromolecular assemblies that control all transport across the nuclear envelope. They are formed by about 30 nucleoporins (Nups), which can be roughly categorized into those forming the structural skeleton of the pore and those creating the central channel and thus providing the transport and gating properties of the NPC. Here we show that the conserved nucleoporin Nup93 is essential for NPC assembly and connects both portions of the NPC. Although the C-terminal domain of the protein is necessary and sufficient for the assembly of a minimal structural backbone, full-length Nup93 is required for the additional recruitment of the Nup62 complex and the establishment of transport-competent NPCs.

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11

Kuhn, Terra M. y Maya Capelson. "Nuclear Pore Proteins in Regulation of Chromatin State". Cells 8, n.º 11 (9 de noviembre de 2019): 1414. http://dx.doi.org/10.3390/cells8111414.

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Nuclear pore complexes (NPCs) are canonically known to regulate nucleocytoplasmic transport. However, research efforts over the last decade have demonstrated that NPCs and their constituent nucleoporins (Nups) also interact with the genome and perform important roles in regulation of gene expression. It has become increasingly clear that many Nups execute these roles specifically through regulation of chromatin state, whether through interactions with histone modifiers and downstream changes in post-translational histone modifications, or through relationships with chromatin-remodeling proteins that can result in physical changes in nucleosome occupancy and chromatin compaction. This review focuses on these findings, highlighting the functional connection between NPCs/Nups and regulation of chromatin structure, and how this connection can manifest in regulation of transcription.

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12

Shevelyov, Yuri Y. "The Role of Nucleoporin Elys in Nuclear Pore Complex Assembly and Regulation of Genome Architecture". International Journal of Molecular Sciences 21, n.º 24 (13 de diciembre de 2020): 9475. http://dx.doi.org/10.3390/ijms21249475.

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For a long time, the nuclear lamina was thought to be the sole scaffold for the attachment of chromosomes to the nuclear envelope (NE) in metazoans. However, accumulating evidence indicates that nuclear pore complexes (NPCs) comprised of nucleoporins (Nups) participate in this process as well. One of the Nups, Elys, initiates NPC reassembly at the end of mitosis. Elys directly binds the decondensing chromatin and interacts with the Nup107–160 subcomplex of NPCs, thus serving as a seeding point for the subsequent recruitment of other NPC subcomplexes and connecting chromatin with the re-forming NE. Recent studies also uncovered the important functions of Elys during interphase where it interacts with chromatin and affects its compactness. Therefore, Elys seems to be one of the key Nups regulating chromatin organization. This review summarizes the current state of our knowledge about the participation of Elys in the post-mitotic NPC reassembly as well as the role that Elys and other Nups play in the maintenance of genome architecture.

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13

Stelter, Philipp, Ruth Kunze, Jessica Fischer y Ed Hurt. "Probing the nucleoporin FG repeat network defines structural and functional features of the nuclear pore complex". Journal of Cell Biology 195, n.º 2 (10 de octubre de 2011): 183–92. http://dx.doi.org/10.1083/jcb.201105042.

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Unraveling the organization of the FG repeat meshwork that forms the active transport channel of the nuclear pore complex (NPC) is key to understanding the mechanism of nucleocytoplasmic transport. In this paper, we develop a tool to probe the FG repeat network in living cells by modifying FG nucleoporins (Nups) with a binding motif (engineered dynein light chain–interacting domain) that can drag several copies of an interfering protein, Dyn2, into the FG network to plug the pore and stop nucleocytoplasmic transport. Our method allows us to specifically probe FG Nups in vivo, which provides insight into the organization and function of the NPC transport channel.

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14

Zeitler, Bryan y Karsten Weis. "The FG-repeat asymmetry of the nuclear pore complex is dispensable for bulk nucleocytoplasmic transport in vivo". Journal of Cell Biology 167, n.º 4 (22 de noviembre de 2004): 583–90. http://dx.doi.org/10.1083/jcb.200407156.

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Nucleocytoplasmic transport occurs through gigantic proteinaceous channels called nuclear pore complexes (NPCs). Translocation through the NPC is exquisitely selective and is mediated by interactions between soluble transport carriers and insoluble NPC proteins that contain phenylalanine-glycine (FG) repeats. Although most FG nucleoporins (Nups) are organized symmetrically about the planar axis of the nuclear envelope, very few localize exclusively to one side of the NPC. We constructed Saccharomyces cerevisiae mutants with asymmetric FG repeats either deleted or swapped to generate NPCs with inverted FG asymmetry. The mutant Nups localize properly within the NPC and exhibit exchanged binding specificity for the export factor Xpo1. Surprisingly, we were unable to detect any defects in the Kap95, Kap121, Xpo1, or mRNA transport pathways in cells expressing the mutant FG Nups. These findings suggest that the biased distribution of FG repeats is not required for major nucleocytoplasmic trafficking events across the NPC.

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Lapetina, Diego L., Christopher Ptak, Ulyss K. Roesner y Richard W. Wozniak. "Yeast silencing factor Sir4 and a subset of nucleoporins form a complex distinct from nuclear pore complexes". Journal of Cell Biology 216, n.º 10 (7 de septiembre de 2017): 3145–59. http://dx.doi.org/10.1083/jcb.201609049.

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Interactions occurring at the nuclear envelope (NE)–chromatin interface influence both NE structure and chromatin organization. Insights into the functions of NE–chromatin interactions have come from the study of yeast subtelomeric chromatin and its association with the NE, including the identification of various proteins necessary for tethering subtelomeric chromatin to the NE and the silencing of resident genes. Here we show that four of these proteins—the silencing factor Sir4, NE-associated Esc1, the SUMO E3 ligase Siz2, and the nuclear pore complex (NPC) protein Nup170—physically and functionally interact with one another and a subset of NPC components (nucleoporins or Nups). Importantly, this group of Nups is largely restricted to members of the inner and outer NPC rings, but it lacks numerous others including cytoplasmically and nucleoplasmically positioned Nups. We propose that this Sir4-associated Nup complex is distinct from holo-NPCs and that it plays a role in subtelomeric chromatin organization and NE tethering.

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Stavru, Fabrizia, Bastian B. Hülsmann, Anne Spang, Enno Hartmann, Volker C. Cordes y Dirk Görlich. "NDC1: a crucial membrane-integral nucleoporin of metazoan nuclear pore complexes". Journal of Cell Biology 173, n.º 4 (15 de mayo de 2006): 509–19. http://dx.doi.org/10.1083/jcb.200601001.

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POM121 and gp210 were, until this point, the only known membrane-integral nucleoporins (Nups) of vertebrates and, thus, the only candidate anchors for nuclear pore complexes (NPCs) within the nuclear membrane. In an accompanying study (see Stavru et al. on p. 477 of this issue), we provided evidence that NPCs can exist independently of POM121 and gp210, and we predicted that vertebrate NPCs contain additional membrane-integral constituents. We identify such an additional membrane protein in the NPCs of mammals, frogs, insects, and nematodes as the orthologue to yeast Ndc1p/Cut11p. Human NDC1 (hNDC1) likely possesses six transmembrane segments, and it is located at the nuclear pore wall. Depletion of hNDC1 from human HeLa cells interferes with the assembly of phenylalanine-glycine repeat Nups into NPCs. The loss of NDC1 function in Caenorhabditis elegans also causes severe NPC defects and very high larval and embryonic mortality. However, it is not ultimately lethal. Instead, homozygous NDC1-deficient worms can be propagated. This indicates that none of the membrane-integral Nups is universally essential for NPC assembly, and suggests that NPC biogenesis is an extremely fault-tolerant process.

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17

Kuhn, Terra M., Pau Pascual-Garcia, Alejandro Gozalo, Shawn C. Little y Maya Capelson. "Chromatin targeting of nuclear pore proteins induces chromatin decondensation". Journal of Cell Biology 218, n.º 9 (31 de julio de 2019): 2945–61. http://dx.doi.org/10.1083/jcb.201807139.

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Nuclear pore complexes have emerged in recent years as chromatin-binding nuclear scaffolds, able to influence target gene expression. However, how nucleoporins (Nups) exert this control remains poorly understood. Here we show that ectopically tethering Drosophila Nups, especially Sec13, to chromatin is sufficient to induce chromatin decondensation. This decondensation is mediated through chromatin-remodeling complex PBAP, as PBAP is both robustly recruited by Sec13 and required for Sec13-induced decondensation. This phenomenon is not correlated with localization of the target locus to the nuclear periphery, but is correlated with robust recruitment of Nup Elys. Furthermore, we identified a biochemical interaction between endogenous Sec13 and Elys with PBAP, and a role for endogenous Elys in global as well as gene-specific chromatin decompaction. Together, these findings reveal a functional role and mechanism for specific nuclear pore components in promoting an open chromatin state.

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18

VanGompel, Michael J. W., Ken C. Q. Nguyen, David H. Hall, William T. Dauer y Lesilee S. Rose. "A novel function for the Caenorhabditis elegans torsin OOC-5 in nucleoporin localization and nuclear import". Molecular Biology of the Cell 26, n.º 9 (mayo de 2015): 1752–63. http://dx.doi.org/10.1091/mbc.e14-07-1239.

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Torsin proteins are AAA+ ATPases that localize to the endoplasmic reticular/nuclear envelope (ER/NE) lumen. A mutation that markedly impairs torsinA function causes the CNS disorder DYT1 dystonia. Abnormalities of NE membranes have been linked to torsinA loss of function and the pathogenesis of DYT1 dystonia, leading us to investigate the role of the Caenorhabditis elegans torsinA homologue OOC-5 at the NE. We report a novel role for torsin in nuclear pore biology. In ooc-5–mutant germ cell nuclei, nucleoporins (Nups) were mislocalized in large plaques beginning at meiotic entry and persisted throughout meiosis. Moreover, the KASH protein ZYG-12 was mislocalized in ooc-5 gonads. Nups were mislocalized in adult intestinal nuclei and in embryos from mutant mothers. EM analysis revealed vesicle-like structures in the perinuclear space of intestinal and germ cell nuclei, similar to defects reported in torsin-mutant flies and mice. Consistent with a functional disruption of Nups, ooc-5–mutant embryos displayed impaired nuclear import kinetics, although the nuclear pore-size exclusion barrier was maintained. Our data are the first to demonstrate a requirement for a torsin for normal Nup localization and function and suggest that these functions are likely conserved.

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Porter, Frederick W. y Ann C. Palmenberg. "Leader-Induced Phosphorylation of Nucleoporins Correlates with Nuclear Trafficking Inhibition by Cardioviruses". Journal of Virology 83, n.º 4 (10 de diciembre de 2008): 1941–51. http://dx.doi.org/10.1128/jvi.01752-08.

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ABSTRACT Picornaviruses disrupt nucleocytoplasmic trafficking pathways during infection. Poliovirus and rhinovirus inhibit nuclear protein import/export through a series of 2A protease-dependent cleavages within nuclear pore proteins (nucleoporins [Nups]), including Nup62, Nup98, and Nup153. Cardioviruses lack the same protease and instead affect trafficking inhibition through an activity mapped to their leader (L) protein, a 67- to 76-amino acid (aa) polypeptide with no known enzymatic activity. We have shown that L from encephalomyocarditis virus (EMCV) binds and inhibits the activity of Ran-GTPase, a key regulator of nucleocytoplasmic transport. We now report that recombinant EMCV L triggers the unregulated efflux of protein cargo from preloaded HeLa cell nuclei in cell-free reactions dependent upon Xenopus egg cytosol or HeLa cell-derived cytosol. Recombinant L was the only viral protein necessary for this activity or for nuclear protein import inhibition. Mutational disruption of the L protein zinc finger domain (C19A) abrogated the inhibitory activity for both import and efflux in cell extracts, but mutations in the C-terminal acidic domain of L (aa 37 to 61) did not. Notably, HeLa cell nuclei treated with L, or those from EMCV-infected cells, showed reproducibly altered patterns of nucleoporin phosphorylation. Nup62, Nup153, and Nup214 each became hyperphosphorylated in an L-dependent manner. Staurosporine, a broad-spectrum kinase inhibitor, blocked this phosphorylation and rescued nuclear import/export activity from L-dependent inhibition. Therefore, cardioviruses target the same group of nucleoporins as enteroviruses, but the effector mechanism triggered by L (or L-Ran complexes) involves a unique cytosol-dependent phosphorylation cascade rather than proteolysis.

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Lord, Christopher L., Benjamin L. Timney, Michael P. Rout y Susan R. Wente. "Altering nuclear pore complex function impacts longevity and mitochondrial function in S. cerevisiae". Journal of Cell Biology 208, n.º 6 (16 de marzo de 2015): 729–44. http://dx.doi.org/10.1083/jcb.201412024.

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The eukaryotic nuclear permeability barrier and selective nucleocytoplasmic transport are maintained by nuclear pore complexes (NPCs), large structures composed of ∼30 proteins (nucleoporins [Nups]). NPC structure and function are disrupted in aged nondividing metazoan cells, although it is unclear whether these changes are a cause or consequence of aging. Using the replicative life span (RLS) of Saccharomyces cerevisiae as a model, we find that specific Nups and transport events regulate longevity independent of changes in NPC permeability. Mutants lacking the GLFG domain of Nup116 displayed decreased RLSs, whereas longevity was increased in nup100-null mutants. We show that Nup116 mediates nuclear import of the karyopherin Kap121, and each protein is required for mitochondrial function. Both Kap121-dependent transport and Nup116 levels decrease in replicatively aged yeast. Overexpression of GSP1, the small GTPase that powers karyopherin-mediated transport, rescued mitochondrial and RLS defects in nup116 mutants and increased longevity in wild-type cells. Together, these studies reveal that specific NPC nuclear transport events directly influence aging.

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Scarcelli, John J., Christine A. Hodge y Charles N. Cole. "The yeast integral membrane protein Apq12 potentially links membrane dynamics to assembly of nuclear pore complexes". Journal of Cell Biology 178, n.º 5 (27 de agosto de 2007): 799–812. http://dx.doi.org/10.1083/jcb.200702120.

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Although the structure and function of components of the nuclear pore complex (NPC) have been the focus of many studies, relatively little is known about NPC biogenesis. In this study, we report that Apq12 is required for efficient NPC biogenesis in Saccharomyces cerevisiae. Apq12 is an integral membrane protein of the nuclear envelope (NE) and endoplasmic reticulum. Cells lacking Apq12 are cold sensitive for growth, and a subset of their nucleoporins (Nups), those that are primarily components of the cytoplasmic fibrils of the NPC, mislocalize to the cytoplasm. APQ12 deletion also causes defects in NE morphology. In the absence of Apq12, most NPCs appear to be associated with the inner but not the outer nuclear membrane. Low levels of benzyl alcohol, which increases membrane fluidity, prevented Nup mislocalization and restored the proper localization of Nups that had accumulated in cytoplasmic foci upon a shift to lower temperature. Thus, Apq12p connects nuclear pore biogenesis to the dynamics of the NE.

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Beliakova-Bethell, Nadejda, Laura J. Terry, Virginia Bilanchone, Rhonda DaSilva, Kunio Nagashima, Susan R. Wente y Suzanne Sandmeyer. "Ty3 Nuclear Entry Is Initiated by Viruslike Particle Docking on GLFG Nucleoporins". Journal of Virology 83, n.º 22 (16 de septiembre de 2009): 11914–25. http://dx.doi.org/10.1128/jvi.01192-09.

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ABSTRACT Yeast retrotransposons form intracellular particles within which replication occurs. Because fungal nuclear membranes do not break down during mitosis, similar to retroviruses infecting nondividing cells, the cDNA produced must be translocated through nuclear pore complexes. The Saccharomyces cerevisiae long terminal repeat retrotransposon Ty3 assembles its Gag3 and Gag3-Pol3 precursor polyproteins into viruslike particles in association with perinuclear P-body foci. These perinuclear clusters of Ty3 viruslike particles localized to sites of clustered nuclear pore complexes (NPCs) in a nup120Δ mutant, indicating that Ty3 particles and NPCs interact physically. The NPC channels are lined with nucleoporins (Nups) with extended FG (Phe-Gly) motif repeat domains, further classified as FG, FxFG, or GLFG repeat types. These domains mediate partitioning of proteins between the cytoplasm and the nucleus. Here we have systematically examined the requirements for FG repeat domains in Ty3 nuclear transport. The GLFG domains interacted in vitro with virus-like particle Gag3, and this interaction was disrupted by mutations in the amino-terminal domain of Gag3, which is predicted to lie on the external surface of the particles. Accordingly, Ty3 transposition was decreased in strains with the GLFG repeats deleted. The spacer-nucleocapsid domain of Gag3, which is predicted to be internal to the particle, interacted with GLFG repeats and nucleocapsid localized to the nucleus. We conclude that Ty3 particle docking on nuclear pores is facilitated by interactions between Gag3 and GLFG Nups and that nuclear entry of the preintegration complex is further promoted by nuclear localization signals within the nucleocapsid and integrase.

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23

Song, Jinsue, Shingo Kose, Ai Watanabe, Se-Young Son, Saehae Choi, Hyerim Hong, Eiki Yamashita, Il Yeong Park, Naoko Imamoto y Soo Jae Lee. "Structural and functional analysis of Hikeshi, a new nuclear transport receptor of Hsp70s". Acta Crystallographica Section D Biological Crystallography 71, n.º 3 (26 de febrero de 2015): 473–83. http://dx.doi.org/10.1107/s1399004714026881.

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Hikeshi is a nuclear transport receptor required for cell survival after stress. It mediates heat-shock-induced nuclear import of 70 kDa heat-shock proteins (Hsp70s) through interactions with FG-nucleoporins (FG-Nups), which are proteins in nuclear pore complexes (NPCs). Here, the crystal structure of human Hikeshi is presented at 1.8 Å resolution. Hikeshi forms an asymmetric homodimer that is responsible for the interaction with Hsp70s. The asymmetry of Hikeshi arises from the distinct conformation of the C-terminal domain (CTD) and the flexibility of the linker regions of each monomer. Structure-guided mutational analyses showed that both the flexible linker region and the CTD are important for nuclear import of Hsp70. Pull-down assays revealed that only full-length Hsp70s can interact with Hikeshi. The N-terminal domain (NTD) consists of a jelly-roll/β-sandwich fold structure which contains hydrophobic pockets involved in FG-Nup recognition. A unique extended loop (E-loop) in the NTD is likely to regulate the interactions of Hikeshi with FG-Nups. The crystal structure of Hikeshi explains how Hikeshi participates in the regulation of nuclear import through the recognition of FG-Nups and which part of Hikeshi affects its binding to Hsp70. This study is the first to yield structural insight into this highly unique import receptor.

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24

Wong, Richard W. "New Activities of the Nuclear Pore Complexes". Cells 10, n.º 8 (18 de agosto de 2021): 2123. http://dx.doi.org/10.3390/cells10082123.

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Nuclear pore complexes (NPCs) at the surface of nuclear membranes play a critical role in regulating the transport of both small molecules and macromolecules between the cell nucleus and cytoplasm via their multilayered spiderweb-like central channel. During mitosis, nuclear envelope breakdown leads to the rapid disintegration of NPCs, allowing some NPC proteins to play crucial roles in the kinetochore structure, spindle bipolarity, and centrosome homeostasis. The aberrant functioning of nucleoporins (Nups) and NPCs has been associated with autoimmune diseases, viral infections, neurological diseases, cardiomyopathies, and cancers, especially leukemia. This Special Issue highlights several new contributions to the understanding of NPC proteostasis.

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Kapinos, Larisa E., Binlu Huang, Chantal Rencurel y Roderick Y. H. Lim. "Karyopherins regulate nuclear pore complex barrier and transport function". Journal of Cell Biology 216, n.º 11 (1 de septiembre de 2017): 3609–24. http://dx.doi.org/10.1083/jcb.201702092.

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Nucleocytoplasmic transport is sustained by karyopherins (Kaps) and a Ran guanosine triphosphate (RanGTP) gradient that imports nuclear localization signal (NLS)–specific cargoes (NLS-cargoes) into the nucleus. However, how nuclear pore complex (NPC) barrier selectivity, Kap traffic, and NLS-cargo release are systematically linked and simultaneously regulated remains incoherent. In this study, we show that Kapα facilitates Kapβ1 turnover and occupancy at the NPC in a RanGTP-dependent manner that is directly coupled to NLS-cargo release and NPC barrier function. This is underpinned by the binding affinity of Kapβ1 to phenylalanine–glycine nucleoporins (FG Nups), which is comparable with RanGTP·Kapβ1, but stronger for Kapα·Kapβ1. On this basis, RanGTP is ineffective at releasing standalone Kapβ1 from NPCs. Depleting Kapα·Kapβ1 by RanGTP further abrogates NPC barrier function, whereas adding back Kapβ1 rescues it while Kapβ1 turnover softens it. Therefore, the FG Nups are necessary but insufficient for NPC barrier function. We conclude that Kaps constitute integral constituents of the NPC whose barrier, transport, and cargo release functionalities establish a continuum under a mechanism of Kap-centric control.

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26

Prophet, Sarah M., Brigitte S. Naughton y Christian Schlieker. "p97/UBXD1 Generate Ubiquitylated Proteins That Are Sequestered into Nuclear Envelope Herniations in Torsin-Deficient Cells". International Journal of Molecular Sciences 23, n.º 9 (21 de abril de 2022): 4627. http://dx.doi.org/10.3390/ijms23094627.

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DYT1 dystonia is a debilitating neurological movement disorder that arises upon Torsin ATPase deficiency. Nuclear envelope (NE) blebs that contain FG-nucleoporins (FG-Nups) and K48-linked ubiquitin are the hallmark phenotype of Torsin manipulation across disease models of DYT1 dystonia. While the aberrant deposition of FG-Nups is caused by defective nuclear pore complex assembly, the source of K48-ubiquitylated proteins inside NE blebs is not known. Here, we demonstrate that the characteristic K48-ubiquitin accumulation inside blebs requires p97 activity. This activity is highly dependent on the p97 adaptor UBXD1. We show that p97 does not significantly depend on the Ufd1/Npl4 heterodimer to generate the K48-ubiquitylated proteins inside blebs, nor does inhibiting translation affect the ubiquitin sequestration in blebs. However, stimulating global ubiquitylation by heat shock greatly increases the amount of K48-ubiquitin sequestered inside blebs. These results suggest that blebs have an extraordinarily high capacity for sequestering ubiquitylated protein generated in a p97-dependent manner. The p97/UBXD1 axis is thus a major factor contributing to cellular DYT1 dystonia pathology and its modulation represents an unexplored potential for therapeutic development.

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27

De Jesús-González, Luis Adrián, Margot Cervantes-Salazar, José Manuel Reyes-Ruiz, Juan Fidel Osuna-Ramos, Carlos Noe Farfán-Morales, Selvin Noé Palacios-Rápalo, José Humberto Pérez-Olais et al. "The Nuclear Pore Complex: A Target for NS3 Protease of Dengue and Zika Viruses". Viruses 12, n.º 6 (26 de mayo de 2020): 583. http://dx.doi.org/10.3390/v12060583.

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During flavivirus infection, some viral proteins move to the nucleus and cellular components are relocated from the nucleus to the cytoplasm. Thus, the integrity of the main regulator of the nuclear-cytoplasmic transport, the nuclear pore complex (NPC), was evaluated during infection with dengue virus (DENV) and Zika virus (ZIKV). We found that while during DENV infection the integrity and distribution of at least three nucleoporins (Nup), Nup153, Nup98, and Nup62 were altered, during ZIKV infection, the integrity of TPR, Nup153, and Nup98 were modified. In this work, several lines of evidence indicate that the viral serine protease NS2B3 is involved in Nups cleavage. First, the serine protease inhibitors, TLCK and Leupeptin, prevented Nup98 and Nup62 cleavage. Second, the transfection of DENV and ZIKV NS2B3 protease was sufficient to inhibit the nuclear ring recognition detected in mock-infected cells with the Mab414 antibody. Third, the mutant but not the active (WT) protease was unable to cleave Nups in transfected cells. Thus, here we describe for the first time that the NS3 protein from flavivirus plays novel functions hijacking the nuclear pore complex, the main controller of the nuclear-cytoplasmic transport.

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Ryan, Kathryn J., J. Michael McCaffery y Susan R. Wente. "The Ran GTPase cycle is required for yeast nuclear pore complex assembly". Journal of Cell Biology 160, n.º 7 (24 de marzo de 2003): 1041–53. http://dx.doi.org/10.1083/jcb.200209116.

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Here, we report the first evidence that the Ran GTPase cycle is required for nuclear pore complex (NPC) assembly. Using a genetic approach, factors required for NPC assembly were identified in Saccharomyces cerevisiae. Four mutant complementation groups were characterized that correspond to respective mutations in genes encoding Ran (gsp1), and essential Ran regulatory factors Ran GTPase–activating protein (rna1), Ran guanine nucleotide exchange factor (prp20), and the RanGDP import factor (ntf2). All the mutants showed temperature-dependent mislocalization of green fluorescence protein (GFP)-tagged nucleoporins (nups) and the pore-membrane protein Pom152. A decrease in GFP fluorescence associated with the nuclear envelope was observed along with an increase in the diffuse, cytoplasmic signal with GFP foci. The defects did not affect the stability of existing NPCs, and nup mislocalization was dependent on de novo protein synthesis and continued cell growth. Electron microscopy analysis revealed striking membrane perturbations and the accumulation of vesicles in arrested mutants. Using both biochemical fractionation and immunoelectron microscopy methods, these vesicles were shown to contain nups. We propose a model wherein a Ran-mediated vesicular fusion step is required for NPC assembly into intact nuclear envelopes.

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Larizza, Lidia y Elisa Adele Colombo. "Interdependence between Nuclear Pore Gatekeepers and Genome Caretakers: Cues from Genome Instability Syndromes". International Journal of Molecular Sciences 25, n.º 17 (29 de agosto de 2024): 9387. http://dx.doi.org/10.3390/ijms25179387.

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This review starts off with the first germline homozygous variants of the Nucleoporin 98 gene (NUP98) in siblings whose clinical presentation recalls Rothmund–Thomson (RTS) and Werner (WS) syndromes. The progeroid phenotype caused by a gene associated with haematological malignancies and neurodegenerative disorders primed the search for interplay between caretakers involved in genome instability syndromes and Nuclear Pore Complex (NPC) components. In the context of basic information on NPC architecture and functions, we discuss the studies on the interdependence of caretakers and gatekeepers in WS and Hereditary Fibrosing Poikiloderma (POIKTMP), both entering in differential diagnosis with RTS. In WS, the WRN/WRNIP complex interacts with nucleoporins of the Y-complex and NDC1 altering NPC architecture. In POIKTMP, the mutated FAM111B, recruited by the Y-complex’s SEC13 and NUP96, interacts with several Nups safeguarding NPC structure. The linkage of both defective caretakers to the NPC highlights the attempt to activate a repair hub at the nuclear periphery to restore the DNA damage. The two separate WS and POIKTMP syndromes are drawn close by the interaction of their damage sensors with the NPC and by the shared hallmark of short fragile telomeres disclosing a major role of both caretakers in telomere maintenance.

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30

Huang, Cheng, Jia-Yin Jiang, Shin C. Chang, Yeou-Guang Tsay, Mei-Ru Chen y Ming-Fu Chang. "Nuclear Export Signal-Interacting Protein Forms Complexes with Lamin A/C-Nups To Mediate the CRM1-Independent Nuclear Export of Large Hepatitis Delta Antigen". Journal of Virology 87, n.º 3 (21 de noviembre de 2012): 1596–604. http://dx.doi.org/10.1128/jvi.02357-12.

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ABSTRACTNuclear export is an important process that not only regulates the functions of cellular factors but also facilitates the assembly of viral nucleoprotein complexes. Chromosome region maintenance 1 (CRM1) that mediates the transport of proteins bearing the classical leucine-rich nuclear export signal (NES) is the best-characterized nuclear export receptor. Recently, several CRM1-independent nuclear export pathways were also identified. The nuclear export of the large form of hepatitis delta antigen (HDAg-L), a nucleocapsid protein of hepatitis delta virus (HDV), which contains a CRM1-independent proline-rich NES, is mediated by the host NES-interacting protein (NESI). The mechanism of the NESI protein in mediating nuclear export is still unknown. In this study, NESI was characterized as a highly glycosylated membrane protein. It interacted and colocalized well in the nuclear envelope with lamin A/C and nucleoporins. Importantly, HDAg-L could be coimmunoprecipitated with lamin A/C and nucleoporins. In addition, binding of the cargo HDAg-L to the C terminus of NESI was detected for the wild-type protein but not for the nuclear export-defective HDAg-L carrying a P205A mutation [HDAg-L(P205A)]. Knockdown of lamin A/C effectively reduced the nuclear export of HDAg-L and the assembly of HDV. These data indicate that by forming complexes with lamin A/C and nucleoporins, NESI facilitates the CRM1-independent nuclear export of HDAg-L.

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Porter, Frederick W., Bradley Brown y Ann C. Palmenberg. "Nucleoporin Phosphorylation Triggered by the Encephalomyocarditis Virus Leader Protein Is Mediated by Mitogen-Activated Protein Kinases". Journal of Virology 84, n.º 24 (29 de septiembre de 2010): 12538–48. http://dx.doi.org/10.1128/jvi.01484-09.

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ABSTRACT Cardioviruses disrupt nucleocytoplasmic transport through the activity of their leader (L) protein. We have shown that hyperphosphorylation of nuclear pore proteins (nucleoporins or Nups), including Nup62, Nup153, and Nup214, is central to this L protein function and requires one or more cytosolic kinases. In this study, potential cellular enzymes involved in encephalomyocarditis virus (EMCV) L-directed Nup phosphorylation were screened with a panel of specific, cell-permeating kinase inhibitors. Extracellular signal-regulated receptor kinase (ERK) and p38 mitogen-activated protein kinase inhibitors (U0126 and SB203580) were sufficient to block Nup hyperphosphorylation in EMCV-infected or L-expressing cells. Recombinant L alone, in the absence of infection, triggered activation of ERK and p38, independent of their upstream signaling cascades. Conserved residues within the L zinc finger (Cys19) and acidic domain (Asp48,51,52,55) were essential for this activation and for the phosphorylation of Nups, suggesting that the phenomena are linked. Analysis of the hyperphosphorylated Nup species revealed only phosphoserine and phosphothreonine residues. The sizes of the tryptic phosphopeptides derived from Nup62 were compatible with sites in the Phe/Gly repeat domain which display common consensus sequences for ERK and p38 substrates. The results provide strong evidence that ERK and p38 are the probable effector kinases required for L-dependent inhibition of nuclear trafficking.

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Lizcano-Perret, Belén, Cécile Lardinois, Fanny Wavreil, Philippe Hauchamps, Gaëtan Herinckx, Frédéric Sorgeloos, Didier Vertommen, Laurent Gatto y Thomas Michiels. "Cardiovirus leader proteins retarget RSK kinases toward alternative substrates to perturb nucleocytoplasmic traffic". PLOS Pathogens 18, n.º 12 (12 de diciembre de 2022): e1011042. http://dx.doi.org/10.1371/journal.ppat.1011042.

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Proteins from some unrelated pathogens, including small RNA viruses of the family Picornaviridae, large DNA viruses such as Kaposi sarcoma-associated herpesvirus and even bacteria of the genus Yersinia can recruit cellular p90-ribosomal protein S6 kinases (RSKs) through a common linear motif and maintain the kinases in an active state. On the one hand, pathogens’ proteins might hijack RSKs to promote their own phosphorylation (direct target model). On the other hand, some data suggested that pathogens’ proteins might dock the hijacked RSKs toward a third interacting partner, thus redirecting the kinase toward a specific substrate. We explored the second hypothesis using the Cardiovirus leader protein (L) as a paradigm. The L protein is known to trigger nucleocytoplasmic trafficking perturbation, which correlates with hyperphosphorylation of phenylalanine-glycine (FG)-nucleoporins (FG-NUPs) such as NUP98. Using a biotin ligase fused to either RSK or L, we identified FG-NUPs as primary partners of the L-RSK complex in infected cells. An L protein mutated in the central RSK-interaction motif was readily targeted to the nuclear envelope whereas an L protein mutated in the C-terminal domain still interacted with RSK but failed to interact with the nuclear envelope. Thus, L uses distinct motifs to recruit RSK and to dock the L-RSK complex toward the FG-NUPs. Using an analog-sensitive RSK2 mutant kinase, we show that, in infected cells, L can trigger RSK to use NUP98 and NUP214 as direct substrates. Our data therefore illustrate a novel virulence mechanism where pathogens’ proteins hijack and retarget cellular protein kinases toward specific substrates, to promote their replication or to escape immunity.

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Dünn-Kittenplon, Daniela, Asaf Ashkenazy-Titelman, Inna Kalt, Jean-Paul Lellouche, Yaron Shav-Tal y Ronit Sarid. "The Portal Vertex of KSHV Promotes Docking of Capsids at the Nuclear Pores". Viruses 13, n.º 4 (31 de marzo de 2021): 597. http://dx.doi.org/10.3390/v13040597.

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Kaposi’s sarcoma-associated herpesvirus (KSHV) is a cancer-related herpesvirus. Like other herpesviruses, the KSHV icosahedral capsid includes a portal vertex, composed of 12 protein subunits encoded by open reading frame (ORF) 43, which enables packaging and release of the viral genome into the nucleus through the nuclear pore complex (NPC). Capsid vertex-specific component (CVSC) tegument proteins, which directly mediate docking at the NPCs, are organized on the capsid vertices and are enriched on the portal vertex. Whether and how the portal vertex is selected for docking at the NPC is unknown. Here, we investigated the docking of incoming ORF43-null KSHV capsids at the NPCs, and describe a significantly lower fraction of capsids attached to the nuclear envelope compared to wild-type (WT) capsids. Like WT capsids, nuclear envelope-associated ORF43-null capsids co-localized with different nucleoporins (Nups) and did not detach upon salt treatment. Inhibition of nuclear export did not alter WT capsid docking. As ORF43-null capsids exhibit lower extent of association with the NPCs, we conclude that although not essential, the portal has a role in mediating the interaction of the CVSC proteins with Nups, and suggest a model whereby WT capsids can dock at the nuclear envelope through a non-portal penton vertex, resulting in an infection ‘dead end’.

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Theerthagiri, Gandhi, Nathalie Eisenhardt, Heinz Schwarz y Wolfram Antonin. "The nucleoporin Nup188 controls passage of membrane proteins across the nuclear pore complex". Journal of Cell Biology 189, n.º 7 (21 de junio de 2010): 1129–42. http://dx.doi.org/10.1083/jcb.200912045.

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All transport across the nuclear envelope (NE) is mediated by nuclear pore complexes (NPCs). Despite their enormous size, ∼60 MD in vertebrates, they are comprised of only ∼30 distinct proteins (nucleoporins or Nups), many of which form subcomplexes that act as building blocks for NPC assembly. One of these evolutionarily conserved subcomplexes, the Nup93 complex, is a major structural component linking the NPC to the membranes of the NE. Using in vitro nuclear assembly assays, we show that two components of the Nup93 complex, Nup188 and Nup205, are dispensable for NPC formation. However, nuclei lacking Nup188 increase in size by several fold compared with wild type. We demonstrate that this phenotype is caused by an accelerated translocation of integral membrane proteins through NPCs, suggesting that Nup188 confines the passage of membrane proteins and is thus crucial for the homeostasis of the different nuclear membranes.

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Makio, Tadashi, Diego L. Lapetina y Richard W. Wozniak. "Inheritance of yeast nuclear pore complexes requires the Nsp1p subcomplex". Journal of Cell Biology 203, n.º 2 (28 de octubre de 2013): 187–96. http://dx.doi.org/10.1083/jcb.201304047.

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In the yeast Saccharomyces cerevisiae, organelles and macromolecular complexes are delivered from the mother to the emerging daughter during cell division, thereby ensuring progeny viability. Here, we have shown that during mitosis nuclear pore complexes (NPCs) in the mother nucleus are actively delivered through the bud neck and into the daughter cell concomitantly with the nuclear envelope. Furthermore, we show that NPC movement into the daughter cell requires members of an NPC subcomplex containing Nsp1p and its interacting partners. NPCs lacking these nucleoporins (Nups) were blocked from entry into the daughter by a putative barrier at the bud neck. This selection process could be observed within individual cells such that NPCs containing Nup82p (an Nsp1p-interacting Nup) were transferred to the daughter cells while functionally compromised NPCs lacking Nup82p were retained in the mother. This mechanism is proposed to facilitate the inheritance of functional NPCs by daughter cells.

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Stewart, Murray. "Function of the Nuclear Transport Machinery in Maintaining the Distinctive Compositions of the Nucleus and Cytoplasm". International Journal of Molecular Sciences 23, n.º 5 (25 de febrero de 2022): 2578. http://dx.doi.org/10.3390/ijms23052578.

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Although the separation of transcription and translation, mediated by the nuclear envelope, is the defining characteristic of Eukaryotes, the barrier between the nuclear and cytoplasmic compartments needs to be semipermeable to enable material to be moved between them. Moreover, each compartment needs to have a distinctive complement of macromolecules to mediate specific functions and so movement between them needs to be controlled. This is achieved through the selective active transport of macromolecules through the nuclear pores that stud the nuclear envelope, and which serve as a conduit between these compartments. Nuclear pores are huge cylindrical macromolecular assemblies and are constructed from the order of 30 different proteins called nucleoporins. Nuclear pores have a central transport channel that is filled with a dense network of natively unfolded portions of many different nuclear pore proteins (nucleoporins or nups). This network generates a barrier that impedes, but does not entirely prevent, the diffusion of many macromolecules through the pores. The rapid movement of a range of proteins and RNAs through the pores is mediated by a range of transport factors that bind their cargo in one compartment and release it in the other. However, although as their size increases the diffusion of macromolecules through nuclear pores is progressively impaired, additional mechanisms, including the binding of some macromolecules to immobile components of each compartment and also the active removal of macromolecules from the inappropriate compartment, are needed to fully maintain the distinctive compositions of each compartment.

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Chen, Zhe, Feng Wu, Lei Li y Yu Hou. "Targeting NUP214 Eradicates Leukemia Stem Cells By Inducing Ferroptosis". Blood 142, Supplement 1 (28 de noviembre de 2023): 4115. http://dx.doi.org/10.1182/blood-2023-184323.

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Acute myeloid leukemia (AML) arises from and are maintained by leukemia stem cell (LSCs), which are also critical causes for drug resistance and relapse of AML. The critical genes involved in LSC maintenance remain largely unknown. Here, we performed a pooled negative-selection screen with a customized small hairpin RNA (shRNA) library against 1191 known pan-essential genes of AML blast cells. We found that several Nucleoporins (NUPs) genes were essential for LSC survival, and NUP214 was highly expressed in LSCs. Knock-out of NUP214 completely eradicated LSCs in MLL-AF9 and HOXA9-MEIS1 AML mouse models, but also comprised HSC maintenance and function. Haploinsufficiency of NUP214 resulted in the increased death of LSCs (~4% to ~33%), reduced LSC numbers, and extended survival of AML mice. In contrast, the haploinsufficiency of NUP214 had a negligible effect on normal hematopoietic stem cells (HSCs) and hematopoiesis. Haploinsufficiency of NUP214 substantially induced lipid peroxidation and resulted in ferroptosis of LSCs, attributed to the remarkably increased transcription of lipoxygenase-15 (ALOX15) and heme oxygenase-1 (HMOX1), evidenced by the results of RNA-seq, proteome, and functional experiments. Immunofluorescence revealed that NUP214 was a mobile nucleoporin and largely located inside the nucleoplasm in LSCs, while NUP214 was mainly located in the nuclear periphery. Co-immunoprecipitation and Cleavage Under Targets and Tagmentation (CUT&Tag) showed that NUP214 directly interacted with transcriptional coactivator Sub1 in LSCs, binding the gene locus of HMOX1 and ALOX15, eventually inhibiting their transcription. Collectively, our findings reveal the essential roles of NUP214 in LSC maintenance and provide a valuable target for AML therapy.

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Martínez-Rojas, Vladimir A., Francesca Pischedda, Isabel Romero-Maldonado, Bouchra Khalaf, Giovanni Piccoli, Paolo Macchi y Carlo Musio. "Nucleoporin Nup358 Downregulation Tunes the Neuronal Excitability in Mouse Cortical Neurons". Life 13, n.º 9 (22 de agosto de 2023): 1791. http://dx.doi.org/10.3390/life13091791.

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Nucleoporins (NUPs) are proteins that comprise the nuclear pore complexes (NPCs). The NPC spans the nuclear envelope of a cell and provides a channel through which RNA and proteins move between the nucleus and the cytoplasm and vice versa. NUP and NPC disruptions have a great impact on the pathophysiology of neurodegenerative diseases (NDDs). Although the downregulation of Nup358 leads to a reduction in the scaffold protein ankyrin-G at the axon initial segment (AIS) of mature neurons, the function of Nup358 in the cytoplasm of neurons remains elusive. To investigate whether Nup358 plays any role in neuronal activity, we downregulated Nup358 in non-pathological mouse cortical neurons and measured their active and passive bioelectrical properties. We identified that Nup358 downregulation is able to produce significant modifications of cell-membrane excitability via voltage-gated sodium channel kinetics. Our findings suggest that Nup358 contributes to neuronal excitability through a functional stabilization of the electrical properties of the neuronal membrane. Hypotheses will be discussed regarding the alteration of this active regulation as putatively occurring in the pathophysiology of NDDs.

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Stang, Todd E., Hannah E. Salapa, Joseph-Patrick W. E. Clarke, Bogdan F. Popescu y Michael C. Levin. "Heterogeneous Nuclear Ribonucleoprotein A1 Knockdown Alters Constituents of Nucleocytoplasmic Transport". Brain Sciences 14, n.º 10 (19 de octubre de 2024): 1039. http://dx.doi.org/10.3390/brainsci14101039.

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Background/Objectives: Changes in nuclear morphology, alterations to the nuclear pore complex (NPC), including loss, aggregation, and dysfunction of nucleoporins (Nups), and nucleocytoplasmic transport (NCT) abnormalities have become hallmarks of neurodegenerative diseases. Previous RNA sequencing data utilizing knockdown of heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) identified enrichment for pathways and changes in RNAs related to nuclear morphology and showed differential expression of key nuclear targets. This suggests that dysfunction of hnRNP A1, which is observed in neurodegenerative diseases, may contribute to abnormalities in nuclear morphology, NPC, and NCT. Methods: We performed knockdown of hnRNP A1 in Neuro-2A cells, a neuronal cell line, to examine nuclear morphology, NPC, and NCT. Results: First, we examined nuclear morphology using Lamin B, wherein we observed increased nuclear envelope abnormalities in cells with hnRNP A1 knockdown as compared to control. To quantify changes in Lamin B, we designed and validated an automated computer-based model, which quantitatively confirmed our observations. Next, we investigated the impact of hnRNP A1 knockdown on components of the NPC and NCT. In line with the previous literature, we found changes in Nups, including altered distribution and reduced protein expression, as well as disrupted NCT. Finally, we validated our findings in multiple sclerosis (MS) brains, a disease with a significant neurodegenerative component caused by hnRNP A1 dysfunction, where neuronal nuclear envelope alterations were significantly increased as compared to controls. Conclusions: Together, these data implicate hnRNP A1 as an important contributor to nuclear morphology, Nup expression and distribution, and NCT and suggest that hnRNP A1 dysfunction may lead to defects in these processes in neurodegenerative diseases.

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40

Loeb, J. D., L. I. Davis y G. R. Fink. "NUP2, a novel yeast nucleoporin, has functional overlap with other proteins of the nuclear pore complex." Molecular Biology of the Cell 4, n.º 2 (febrero de 1993): 209–22. http://dx.doi.org/10.1091/mbc.4.2.209.

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We have isolated a new gene, NUP2, that encodes a constituent of the yeast-nuclear pore complex (NPC). The NUP2 protein sequence shares a central repetitive domain with NSP1 and NUP1, the two previously characterized yeast nucleoporins. Like NUP1 and NSP1, NUP2 localizes to discrete spots in the nuclear envelope, as determined by indirect immunofluorescence. Although the sequence similarity among these three nucleoporins suggests that they have a similar role in the nuclear pore complex, NUP2, in contrast to NSP1 and NUP1, is not required for growth. Some combinations of mutant alleles of NUP1, NSP1, and NUP2 display "synthetic lethal" relationships that provide evidence for functional interaction between these NPC components. This genetic evidence of overlapping function suggests that the nucleoporins act in concert, perhaps participating in the same step of the recognition or transit of macromolecules through the NPC.

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Diez, Lisa, Larisa E. Kapinos, Janine Hochmair, Sabrina Huebschmann, Alvaro Dominguez-Baquero, Amelie Vogt, Marija Rankovic, Markus Zweckstetter, Roderick Y. H. Lim y Susanne Wegmann. "Phosphorylation but Not Oligomerization Drives the Accumulation of Tau with Nucleoporin Nup98". International Journal of Molecular Sciences 23, n.º 7 (23 de marzo de 2022): 3495. http://dx.doi.org/10.3390/ijms23073495.

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Tau is a neuronal protein that stabilizes axonal microtubules (MTs) in the central nervous system. In Alzheimer’s disease (AD) and other tauopathies, phosphorylated Tau accumulates in intracellular aggregates, a pathological hallmark of these diseases. However, the chronological order of pathological changes in Tau prior to its cytosolic aggregation remains unresolved. These include its phosphorylation and detachment from MTs, mislocalization into the somatodendritic compartment, and oligomerization in the cytosol. Recently, we showed that Tau can interact with phenylalanine-glycine (FG)-rich nucleoporins (Nups), including Nup98, that form a diffusion barrier inside nuclear pore complexes (NPCs), leading to defects in nucleocytoplasmic transport. Here, we used surface plasmon resonance (SPR) and bio-layer interferometry (BLI) to investigate the molecular details of Tau:Nup98 interactions and determined how Tau phosphorylation and oligomerization impact the interactions. Importantly, phosphorylation, but not acetylation, strongly facilitates the accumulation of Tau with Nup98. Oligomerization, however, seems to inhibit Tau:Nup98 interactions, suggesting that Tau-FG Nup interactions occur prior to oligomerization. Overall, these results provide fundamental insights into the molecular mechanisms of Tau-FG Nup interactions within NPCs, which might explain how stress-and disease-associated posttranslational modifications (PTMs) may lead to Tau-induced nucleocytoplasmic transport (NCT) failure. Intervention strategies that could rescue Tau-induced NCT failure in AD and tauopathies will be further discussed.

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Coyne, Alyssa N., Victoria Baskerville, Benjamin L. Zaepfel, Dennis W. Dickson, Frank Rigo, Frank Bennett, C. Patrick Lusk y Jeffrey D. Rothstein. "Nuclear accumulation of CHMP7 initiates nuclear pore complex injury and subsequent TDP-43 dysfunction in sporadic and familial ALS". Science Translational Medicine 13, n.º 604 (28 de julio de 2021): eabe1923. http://dx.doi.org/10.1126/scitranslmed.abe1923.

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Alterations in the components [nucleoporins (Nups)] and function of the nuclear pore complex (NPC) have been implicated as contributors to the pathogenesis of genetic forms of neurodegeneration including C9orf72 amyotrophic lateral sclerosis/frontotemporal dementia (ALS/FTD). We hypothesized that Nup alterations and the consequential loss of NPC function may lie upstream of TDP-43 dysfunction and mislocalization widely observed in ALS, FTD, and related neurodegenerative diseases. Here, we provide evidence that CHMP7, a critical mediator of NPC quality control, is increased in nuclei of C9orf72 and sporadic ALS induced pluripotent stem cell (iPSC)–derived spinal neurons (iPSNs) and postmortem human motor cortex before the emergence of Nup alterations. Inhibiting the nuclear export of CHMP7 triggered Nup reduction and TDP-43 dysfunction and pathology in human neurons. Knockdown of CHMP7 alleviated disease-associated Nup alterations, deficits in Ran GTPase localization, defects in TDP-43–associated mRNA expression, and downstream glutamate-induced neuronal death. Thus, our data support a role for altered CHMP7-mediated Nup homeostasis as a prominent initiating pathological mechanism for familial and sporadic ALS and highlight the potential for CHMP7 as therapeutic target.

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Buchwalter, Abigail L., Yun Liang y Martin W. Hetzer. "Nup50 is required for cell differentiation and exhibits transcription-dependent dynamics". Molecular Biology of the Cell 25, n.º 16 (15 de agosto de 2014): 2472–84. http://dx.doi.org/10.1091/mbc.e14-04-0865.

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The nuclear pore complex (NPC) plays a critical role in gene expression by mediating import of transcription regulators into the nucleus and export of RNA transcripts to the cytoplasm. Emerging evidence suggests that in addition to mediating transport, a subset of nucleoporins (Nups) engage in transcriptional activation and elongation at genomic loci that are not associated with NPCs. The underlying mechanism and regulation of Nup mobility on and off nuclear pores remain unclear. Here we show that Nup50 is a mobile Nup with a pronounced presence both at the NPC and in the nucleoplasm that can move between these different localizations. Strikingly, the dynamic behavior of Nup50 in both locations is dependent on active transcription by RNA polymerase II and requires the N-terminal half of the protein, which contains importin α– and Nup153-binding domains. However, Nup50 dynamics are independent of importin α, Nup153, and Nup98, even though the latter two proteins also exhibit transcription-dependent mobility. Of interest, depletion of Nup50 from C2C12 myoblasts does not affect cell proliferation but inhibits differentiation into myotubes. Taken together, our results suggest a transport-independent role for Nup50 in chromatin biology that occurs away from the NPC.

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44

Mitic, Kristina, Marianne Grafe, Petros Batsios y Irene Meyer. "Partial Disassembly of the Nuclear Pore Complex Proteins during Semi-Closed Mitosis in Dictyostelium discoideum". Cells 11, n.º 3 (25 de enero de 2022): 407. http://dx.doi.org/10.3390/cells11030407.

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Dictyostelium cells undergo a semi-closed mitosis, during which the nuclear envelope (NE) persists; however, free diffusion between the cytoplasm and the nucleus takes place. To permit the formation of the mitotic spindle, the nuclear envelope must be permeabilized in order to allow diffusion of tubulin dimers and spindle assembly factors into the nucleus. In Aspergillus, free diffusion of proteins between the cytoplasm and the nucleus is achieved by a partial disassembly of the nuclear pore complexes (NPCs) prior to spindle assembly. In order to determine whether this is also the case in Dictyostelium, we analysed components of the NPC by immunofluorescence microscopy and live cell imaging and studied their behaviour during interphase and mitosis. We observed that the NPCs are absent from the contact area of the nucleoli and that some nucleoporins also localize to the centrosome and the spindle poles. In addition, we could show that, during mitosis, the central FG protein NUP62, two inner ring components and Gle1 depart from the NPCs, while all other tested NUPs remained at the NE. This leads to the conclusion that indeed a partial disassembly of the NPCs takes place, which contributes to permeabilisation of the NE during semi-closed mitosis.

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45

Chang, Chou-Wei, Chung-Pei Lee, Mei-Tzu Su, Ching-Hwa Tsai y Mei-Ru Chen. "BGLF4 Kinase Modulates the Structure and Transport Preference of the Nuclear Pore Complex To Facilitate Nuclear Import of Epstein-Barr Virus Lytic Proteins". Journal of Virology 89, n.º 3 (19 de noviembre de 2014): 1703–18. http://dx.doi.org/10.1128/jvi.02880-14.

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ABSTRACTBGLF4 kinase, the only Ser/Thr protein kinase encoded by the Epstein-Barr virus (EBV) genome, phosphorylates multiple viral and cellular substrates to optimize the cellular environment for viral DNA replication and the nuclear egress of nucleocapsids. Previously, we found that nuclear targeting of BGLF4 is through direct interaction with the FG repeat-containing nucleoporins (FG-Nups) Nup62 and Nup153 independently of cytosolic transport factors. Here, we investigated the regulatory effects of BGLF4 on the structure and biological functions of the nuclear pore complex (NPC). In EBV-positive NA cells, the distribution of FG-Nups was modified during EBV reactivation. In transfected cells, BGLF4 changed the staining pattern of Nup62 and Nup153 in a kinase activity-dependent manner. Detection with anti-phospho-Ser/Thr-Pro MPM-2 antibody demonstrated that BGLF4 induced the phosphorylation of Nup62 and Nup153. The nuclear targeting of importin β was attenuated in the presence of BGLF4, leading to inhibition of canonical nuclear localization signal (NLS)-mediated nuclear import. Anin vitronuclear import assay revealed that BGLF4 induced the nuclear import of larger molecules. Notably, we found that BGLF4 promoted the nuclear import of several non-NLS-containing EBV proteins, including the viral DNA-replicating enzymes BSLF1, BBLF2/3, and BBLF4 and the major capsid protein (VCA), in cotransfected cells. The data presented here suggest that BGLF4 interferes with the normal functions of Nup62 and Nup153 and preferentially helps the nuclear import of viral proteins for viral DNA replication and assembly. In addition, the nuclear import-promoting activity was found in cells expressing the BGLF4 homologs of another two gammaherpesviruses but not those from alpha- and betaherpesviruses.IMPORTANCEDuring lytic replication, many EBV genome-encoded proteins need to be transported into the nucleus, not only for viral DNA replication but also for the assembly of nucleocapsids. Because nuclear pore complexes are effective gateways that control nucleocytoplasmic traffic, most EBV proteins without canonical NLSs are retained in the cytoplasm until they form complexes with their NLS-containing partners for nuclear targeting. In this study, we found that EBV BGLF4 protein kinase interacts with the Nup62 and Nup153 and induces the redistribution of FG-Nups. BGLF4 modulates the function of the NPC to inhibit the nuclear import of host NLS-containing proteins. Simultaneously, the nuclear import of non-NLS-containing EBV lytic proteins was enhanced, possibly through phosphorylation of Nup62 and Nup153, nuclear pore dilation, or microtubule reorganization. Overall, our data suggest that BGLF4-induced modification of nuclear pore transport may block nuclear targeting of cellular proteins and increase the import of viral proteins to promote viral lytic replication.

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46

Lee, Jihoon, Zhao Zhang, Juyeong Hong y Kexin Xu. "Abstract 5593: METTL3-NUP93 axis as a novel therapeutic target in castration-resistant prostate cancer (CRPC)". Cancer Research 84, n.º 6_Supplement (22 de marzo de 2024): 5593. http://dx.doi.org/10.1158/1538-7445.am2024-5593.

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Abstract Androgens and androgen receptor (AR) are the key factors driving the development and progression of prostate cancer. Extensive studies confirm both androgens and AR are required for normal growth and development of the prostate gland, and also in prostate cancer pathogenesis and androgen-independent cancer progression. Therefore, androgen deprivation therapies or targeting AR function have always been the mainstay of therapeutic strategy against advanced prostate cancers. However, the current therapeutic strategies are temporally effective in suppressing prostate tumors, and eventually develop metastatic disease. Nuclear pore complex (NPC) is a large complex composed of approximately 30 different proteins termed nucleoporins (NUPs), which serve as the structural and functional units for macromolecules shuttling including proteins and messenger RNAs (mRNAs) between nucleus and cytoplasm. Abnormal expression or genetic alterations of NUP genes has been indicated to involve in the progression of prostate cancer, but the underlying molecular mechanisms are poorly understood. We recently found that the m6A methyltransferase METTL3 directly interacts with nucleoporin 93 (NUP93), one of the NPC components in multiple prostate cancer cells, which seems to be more robust in the castration-resistant prostate cancer (CRPC) cell lines. Disruption of METTL3-NUP93 axis abrogated proliferation and oncogenic phenotypes of CRPC cells, suggesting that the METTL3-NUP93 axis may play an important role in prostate cancer progression to castration resistance. Most importantly, a subgroup of mRNAs regulated through METTL3-NUP93 axis encode cholesterol biosynthesis enzymes that trigger the activation of persistent AR signaling in CRPC. Therefore, Our current findings suggest that inhibition of METTL3-NUP93 axis may represent a promising therapeutic strategy for CRPC, the lethal form of the disease. Citation Format: Jihoon Lee, Zhao Zhang, Juyeong Hong, Kexin Xu. METTL3-NUP93 axis as a novel therapeutic target in castration-resistant prostate cancer (CRPC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5593.

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47

Villanueva-Valencia, José Ramon, Efthymios Tsimtsirakis y Alex Evilevitch. "Role of HSV-1 Capsid Vertex-Specific Component (CVSC) and Viral Terminal DNA in Capsid Docking at the Nuclear Pore". Viruses 13, n.º 12 (15 de diciembre de 2021): 2515. http://dx.doi.org/10.3390/v13122515.

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Penetration of the viral genome into a host cell nucleus is critical for initiation of viral replication for most DNA viruses and a few RNA viruses. For herpesviruses, viral DNA ejection into a nucleus occurs when the capsid docks at the nuclear pore complex (NPC) basket with the correct orientation of the unique capsid portal vertex. It has been shown that capsid vertex-specific component (CVSC) proteins, which are located at the twelve vertices of the human herpes simplex virus type 1 (HSV-1) capsid, interact with nucleoporins (Nups) of NPCs. However, it remained unclear whether CVSC proteins determine capsid-to-NPC binding. Furthermore, it has been speculated that terminal DNA adjacent to the portal complex of DNA-filled C-capsids forms a structural motif with the portal cap (which retains DNA in the capsid), which mediates capsid-NPC binding. We demonstrate that terminal viral DNA adjacent to the portal proteins does not present a structural element required for capsid-NPC binding. Our data also show that level of CVSC proteins on the HSV-1 capsid affects level of NPC binding. To elucidate the capsid-binding process, we use an isolated, reconstituted cell nucleus system that recapitulates capsid-nucleus binding in vivo without interference from trafficking kinetics of capsids moving toward the nucleus. This allows binding of non-infectious capsid maturation intermediates with varying levels of vertex-specific components. This experimental system provides a platform for investigating virus–host interaction at the nuclear membrane.

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48

Park, Nogi, Pavan Katikaneni, Tim Skern y Kurt E. Gustin. "Differential Targeting of Nuclear Pore Complex Proteins in Poliovirus-Infected Cells". Journal of Virology 82, n.º 4 (28 de noviembre de 2007): 1647–55. http://dx.doi.org/10.1128/jvi.01670-07.

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ABSTRACT Poliovirus disrupts nucleocytoplasmic trafficking and results in the cleavage of two nuclear pore complex (NPC) proteins, Nup153 and Nup62. The NPC is a 125-MDa complex composed of multiple copies of 30 different proteins. Here we have extended the analysis of the NPC in infected cells by examining the status of Nup98, an interferon-induced NPC protein with a major role in mRNA export. Our results indicate that Nup98 is targeted for cleavage after infection but that this occurs much more rapidly than it does for Nup153 and Nup62. In addition, we find that cleavage of these NPC proteins displays differential sensitivity to the viral RNA synthesis inhibitor guanidine hydrochloride. Inhibition of nuclear import and relocalization of host nuclear proteins to the cytoplasm were only apparent at later times after infection when all three nucleoporins (Nups) were cleaved. Surprisingly, analysis of the distribution of mRNA in infected cells revealed that proteolysis of Nup98 did not result in an inhibition of mRNA export. Cleavage of Nup98 could be reconstituted by the addition of purified rhinovirus type 2 2Apro to whole-cell lysates prepared from uninfected cells, suggesting that the 2A protease has a role in this process in vivo. These results indicate that poliovirus differentially targets subsets of NPC proteins at early and late times postinfection. In addition, targeting of interferon-inducible NPC proteins, such as Nup98, may be an additional weapon in the arsenal of poliovirus and perhaps other picornaviruses to overcome host defense mechanisms.

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49

Kenna, M. A., J. G. Petranka, J. L. Reilly y L. I. Davis. "Yeast N1e3p/Nup170p is required for normal stoichiometry of FG nucleoporins within the nuclear pore complex." Molecular and Cellular Biology 16, n.º 5 (mayo de 1996): 2025–36. http://dx.doi.org/10.1128/mcb.16.5.2025.

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The FG nucleoporins are a conserved family of proteins, some of which bind to the nuclear localization sequence receptor, karyopherin. Distinct members of this family are found in each region of the nuclear pore complex (NPC), spanning from the cytoplasmically disposed filaments to the distal end of the nuclear basket. Movement of karyopherin from one FG nucleoporin to the next may be required for translocation of substrates across the NPC. So far, nothing is known about how the FG nucleoporins are localized within the NPC. To identify proteins that interact functionally with one member of this family, the Saccharomyces cerevisiae protein Nup1p, we previously identified 16 complementation groups containing mutants that are lethal in the absence of NUP1 These mutants were referred to as nle (Nup-lethal) mutants. Mutants in the nle3/nlel7 complementation group are lethal in combination with amino-terminal nup1 truncation mutants, which we have previously shown to be defective for localization to the NPC. Here we show that NLE3 (which is allelic to NUP170) encodes a protein with similarity to the mammalian nucleoporin Nup155. We show that Nle3p coprecipitates with glutathione S-transferase fusions containing the amino-terminal domain of Nup1p. Furthermore, a deletion of Nle3p leads to changes in the stoichiometry of several of the XFXFG nucleoporins, including the loss of Nup1p and Nup2p. These results suggest that Nle3p plays a role in localizing specific FG nucleoporins within the NPC. The broad spectrum of synthetic phenotypes observed with the nle3delta mutant provides support for this model. We also identify a redundant yeast homolog that can partially substitute for Nle3p and show that together these proteins are required for viability.

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50

Layish, Bailey, Ram Goli, Haley Flick, Szu-Wei Huang, Robert Z. Zhang, Mamuka Kvaratskhelia y Melissa Kane. "Virus specificity and nucleoporin requirements for MX2 activity are affected by GTPase function and capsid-CypA interactions". PLOS Pathogens 20, n.º 3 (21 de marzo de 2024): e1011830. http://dx.doi.org/10.1371/journal.ppat.1011830.

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Human myxovirus resistance 2 (MX2/MXB) is an interferon-induced GTPase that inhibits human immunodeficiency virus-1 (HIV-1) infection by preventing nuclear import of the viral preintegration complex. The HIV-1 capsid (CA) is the major viral determinant for sensitivity to MX2, and complex interactions between MX2, CA, nucleoporins (Nups), cyclophilin A (CypA), and other cellular proteins influence the outcome of viral infection. To explore the interactions between MX2, the viral CA, and CypA, we utilized a CRISPR-Cas9/AAV approach to generate CypA knock-out cell lines as well as cells that express CypA from its endogenous locus, but with specific point mutations that would abrogate CA binding but should not affect enzymatic activity or cellular function. We found that infection of CypA knock-out and point mutant cell lines with wild-type HIV-1 and CA mutants recapitulated the phenotypes observed upon cyclosporine A (CsA) addition, indicating that effects of CsA treatment are the direct result of blocking CA-CypA interactions and are therefore independent from potential interactions between CypA and MX2 or other cellular proteins. Notably, abrogation of GTP hydrolysis by MX2 conferred enhanced antiviral activity when CA-CypA interactions were abolished, and this effect was not mediated by the CA-binding residues in the GTPase domain, or by phosphorylation of MX2 at position T151. We additionally found that elimination of GTPase activity also altered the Nup requirements for MX2 activity. Our data demonstrate that the antiviral activity of MX2 is affected by CypA-CA interactions in a virus-specific and GTPase activity-dependent manner. These findings further highlight the importance of the GTPase domain of MX2 in regulation of substrate specificity and interaction with nucleocytoplasmic trafficking pathways.

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