The Experts below are selected from a list of 79860 Experts worldwide ranked by ideXlab platform
Pamela A Silver - One of the best experts on this subject based on the ideXlab platform.
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Nuclear Transport and cancer from mechanism to intervention
Nature Reviews Cancer, 2004Co-Authors: Tweeny R Kau, Jeffrey C Way, Pamela A SilverAbstract:Nuclear-cytoplasmic Transport, which occurs through special structures called Nuclear pores, is an important aspect of normal cell function, and defects in this process have been detected in many different types of cancer cells. These defects can occur in the signal-transduction pathways that regulate the transfer of factors such as p53 and β-catenin in and out of the nucleus, or in the general Nuclear import and export machinery itself. In some cases, Nuclear Transport factors are overproduced, whereas in others, chromosomal translocations disrupt the structural proteins that make up the Nuclear pore, leading to cell transformation. How does disruption of Nuclear-cytoplasmic Transport promote transformation, and is this process a viable therapeutic target?
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Genome-wide localization of the Nuclear Transport machinery couples transcriptional status and Nuclear organization
Cell, 2004Co-Authors: Jason M. Casolari, Suzanne Komili, Jason West, Haley Hieronymus, Christopher R Brown, Pamela A SilverAbstract:The association of genes with the Nuclear pore complex (NPC) and Nuclear Transport factors has been implicated in transcriptional regulation. We therefore examined the association of components of the Nuclear Transport machinery including karyopherins, nucleoporins, and the Ran guanine-nucleotide exchange factor (RanGEF) with the Saccharomyces cerevisiae genome. We find that most nucleoporins and karyopherins preferentially associate with a subset of highly transcribed genes and with genes that possess Rap1 binding sites whereas the RanGEF preferentially associates with transcriptionally inactive genes. Consistent with coupling of transcription to the Nuclear pore, we show that transcriptional activation of the GAL genes results in their association with Nuclear pore proteins, relocation to the Nuclear periphery, and loss of RanGEF association. Taken together, these results indicate that the organization of the genome is coupled via transcriptional state to the Nuclear Transport machinery.
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Nuclear Transport as a target for cell growth.
Drug discovery today, 2003Co-Authors: Tweeny R Kau, Pamela A SilverAbstract:The function of many key proteins and transcription factors involved in cell growth can be regulated by their cellular localization. Such proteins include the tumor suppressor p53 and the Nuclear factor κB. Although the idea of trapping such proteins in either the nucleus or cytoplasm has been introduced as a potential therapeutic target, only two Nuclear Transport inhibitors have been reported. Here, we explore the roles of small-molecule inhibitors that cause target proteins to sequester in either the nucleus or cytoplasm. Methods of artificially targeting proteins to the nucleus or cytoplasm using peptide aptamer technology are also discussed.
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hiv 1 vpr interacts with the Nuclear Transport pathway to promote macrophage infection
Genes & Development, 1998Co-Authors: Marie A Vodicka, Pamela A Silver, Deanna M Koepp, Michael EmermanAbstract:HIV-1 Vpr promotes Nuclear entry of viral nucleic acids in nondividing macrophages and also causes a G2 cell-cycle arrest. Consistent with its role in Nuclear Transport, we show Vpr localizes to the Nuclear envelope in both human and yeast cells. Like the importin-b subunit of the Nuclear import receptor, Vpr also interacts with the yeast importin-a subunit and nucleoporins. Moreover, overexpression of either Vpr or importin-b in yeast blocks Nuclear Transport of mRNAs. A mutant form of Vpr (Vpr F34I) that does not localize at the Nuclear envelope, or bind to importin-a and nucleoporins, renders HIV-1 incapable of infecting macrophages efficiently. Vpr F34I, however, still causes a G2 arrest, demonstrating that the dual functions of Vpr are genetically separable. Our data suggest Vpr functionally resembles importin-b in Nuclear import of the HIV-1 pre-integration complex and this function is essential for the role of Vpr in macrophage infection, but not G2 arrest.
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Interaction between the small GTPase Ran/Gsp1p and Ntf2p is required for Nuclear Transport.
Molecular and cellular biology, 1997Co-Authors: D. H. Wong, Murray Stewart, Anita H. Corbett, H M Kent, Pamela A SilverAbstract:Bidirectional movement of proteins and RNAs across the Nuclear envelope requires Ran, a Ras-like GTPase. A genetic screen of the yeast Saccharomyces cerevisiae was performed to isolate conditional alleles of GSP1, a gene that encodes a homolog of Ran. Two temperature-sensitive alleles, gsp1-1 and gsp1-2, were isolated. The mutations in these two alleles map to regions that are structurally conserved between different members of the Ras family. Each mutant strain exhibits various Nuclear Transport defects. Both biochemical and genetic experiments indicate a decreased interaction between Ntf2p, a factor which is required for protein import, and the mutant GSP1 gene products. Overexpression of NTF2 can suppress the temperature sensitive phenotype of gsp1-1 and gsp1-2 and partially rescue Nuclear Transport defects. However, overexpression of a mutant allele of NTF2 with decreased binding to Gsp1p cannot rescue the temperature sensitivity of gsp1-1 and gsp1-2. Taken together, these data demonstrate that the interaction between Gsp1p and Ntf2p is critical for Nuclear Transport.
Yoshio Umezawa - One of the best experts on this subject based on the ideXlab platform.
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Quantitative determination of protein Nuclear Transport induced by phosphorylation or by proteolysis.
Analytical Chemistry, 2005Co-Authors: Ryohei Takao, Takeaki Ozawa, Yoshio UmezawaAbstract:Nucleocytoplasmic Transport of proteins in eukaryotic cells is a fundamental process for gene expression. The Transport is regulated by posttranslational modifications of the proteins, such as ligand-binding, phosphorylation, and proteolysis. For monitoring the Nuclear Transport of proteins induced by a ligand binding, we have recently developed a genetically encoded bioluminescent indicator based on reconstitution of split fragments of Renilla reniformis (RLuc) by protein splicing with DnaE inteins. We herein describe that the technique is used for detecting phosphorylation- or proteolysis-induced Nuclear Transports of a target protein. Two model proteins, signal transducer and activator of transcription 3 (STAT3) and sterol-regulatory element binding protein-2 (SREBP-2), were exemplified as phosphorylation- and proteolysis-induced Nuclear Transport, respectively. Each STAT3 or SREBP-2 is connected with C-terminal halves of RLuc and DnaE. If the protein translocates into the nucleus, the C-terminal fragm...
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Quantitative determination of protein Nuclear Transport induced by phosphorylation or by proteolysis.
Analytical chemistry, 2005Co-Authors: Sung Bae Kim, Ryohei Takao, Takeaki Ozawa, Yoshio UmezawaAbstract:Nucleocytoplasmic Transport of proteins in eukaryotic cells is a fundamental process for gene expression. The Transport is regulated by posttranslational modifications of the proteins, such as ligand-binding, phosphorylation, and proteolysis. For monitoring the Nuclear Transport of proteins induced by a ligand binding, we have recently developed a genetically encoded bioluminescent indicator based on reconstitution of split fragments of Renilla reniformis (RLuc) by protein splicing with DnaE inteins. We herein describe that the technique is used for detecting phosphorylation- or proteolysis-induced Nuclear Transports of a target protein. Two model proteins, signal transducer and activator of transcription 3 (STAT3) and sterol-regulatory element binding protein-2 (SREBP-2), were exemplified as phosphorylation- and proteolysis-induced Nuclear Transport, respectively. Each STAT3 or SREBP-2 is connected with C-terminal halves of RLuc and DnaE. If the protein translocates into the nucleus, the C-terminal fragment of RLuc meets the N-terminal fragment of RLuc, and full-length RLuc is reconstituted by protein splicing in the nucleus. The indicator with SREBP-2 enabled us to quantify the intracellular concentrations of cholesterol. The indicator with STAT3 quantified the extent of the Nuclear Transport induced by representative cytokines. This simple assay based on protein Nuclear Transports allows the selection of suitable drugs among candidates and has significant potential for risk assessments, such as carcinogenic chemical screening in vitro and in vivo.
Mary Dasso - One of the best experts on this subject based on the ideXlab platform.
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Nuclear Transport erupts on the slopes of Mount Etna
Nature Cell Biology, 2004Co-Authors: Maureen A. Powers, Mary DassoAbstract:Nuclear pore complexes (NPCs) mediate the active Transport of large substrates and allow the passive diffusion of small molecules into the nucleus of eukaryotic cells. The EMBO Workshop on the Mechanisms of Nuclear Transport focused on NPCs and on the soluble nucleocytoplasmic Transport machinery. This meeting, organized by Valérie Doye (Institut Curie, Paris) and Ed Hurt (University of Heidelberg), was held within view of Mount Etna at Taormina, Sicily (November 1–5, 2003). Presentations emphasized the dynamic properties of the Nuclear trafficking machinery, and demonstrated the continuity of Nuclear Transport with processes in the nucleus and cytoplasm.
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Nuclear Transport erupts on the slopes of Mount Etna
Nature cell biology, 2004Co-Authors: Maureen A. Powers, Mary DassoAbstract:Nuclear pore complexes (NPCs) mediate the active Transport of large substrates and allow the passive diffusion of small molecules into the nucleus of eukaryotic cells. The EMBO Workshop on the Mechanisms of Nuclear Transport focused on NPCs and on the soluble nucleocytoplasmic Transport machinery. This meeting, organized by Valerie Doye (Institut Curie, Paris) and Ed Hurt (University of Heidelberg), was held within view of Mount Etna at Taormina, Sicily (November 1–5, 2003). Presentations emphasized the dynamic properties of the Nuclear trafficking machinery, and demonstrated the continuity of Nuclear Transport with processes in the nucleus and cytoplasm.
Murray Stewart - One of the best experts on this subject based on the ideXlab platform.
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a physical model describing the interaction of Nuclear Transport receptors with fg nucleoporin domain assemblies
eLife, 2016Co-Authors: Raphael Zahn, Dino Osmanovic, Severin Ehret, Carolina Araya Callis, Steffen Frey, Murray Stewart, Dirk Gorlich, Bart W Hoogenboom, R RichterAbstract:The cells of animals, plants and other eukaryotic organisms contain a compartment called the nucleus that contains most of the cell's genetic material. Proteins and other molecules – collectively known as cargos – can enter and exit the nucleus via tiny channels in the membrane that surrounds and protects it. Receptor proteins – called Nuclear Transport receptors – bind to potential cargos and shuttle them through the channels. This selective Transport process relies on the Nuclear Transport receptors being attracted to flexible, spaghetti-like proteins that are anchored to the walls on the inside of each channel. However, because of their flexible and disordered nature, these so-called FG domains are difficult to study, and the details of the Transport process are poorly understood. Zahn, Osmanovic et al. decided to study how the FG domains behave and what happens when they interact with Nuclear Transport receptors by using ultrathin films made of just the FG domains. This is a good model system because the films are easier to study than the whole channels, but are likely to retain the essential properties of the real barrier formed in the Nuclear envelope. Zahn, Osmanovic et al. compared the binding of two Nuclear Transport receptors of different sizes, taken from humans and yeast, to FG domain films made from one of three different FG domains. The experiments showed that the different Nuclear Transport receptors bind to the different FG domains in very similar ways. Zahn, Osmanovic et al. then used a computational model that essentially represented the FG domains as sticky spaghetti and the Nuclear Transport receptors as perfectly round meatballs. This sticky-spaghetti-with-meatballs model reproduced the experimental data, implying that the exact chemical make-up and structure of the molecules may not be critical for controlling the Transport of cargo across the Nuclear envelope. Future studies will test whether the generic physical features of Nuclear Transport receptors and FG domains can indeed explain how the cargo molecules pass through the Nuclear envelope.
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Structures of Nuclear Transport components
Trends in cell biology, 1999Co-Authors: Yuh Min Chook, Murray Stewart, Gino Cingolani, Elena Conti, Ingrid R. Vetter, Alfred WittinghoferAbstract:The past three years have seen the solution of several Nuclear Transport component structures and recently of the structure of a regulator bound to part of a Nuclear pore complex (NPC) protein. These structures have provided a wealth of valuable information about the proteins involved and suggested strategies for further investigation of their properties. We do not have space here to go into detail about this information, so instead we are illustrating the structures and providing primary references enabling interested readers to find further information. On this page, we are concentrating on the GTPase Ran and proteins that modulate its activity, and on the facing page are the other Transport factors, some of which also interact directly with Ran. Notably absent at the moment are the Nuclear pore complex component s, apart from one domain of RanBP2. Only when theses are characterized fully will we really be able to understand how Transport substrates move across the Nuclear envelope.
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Interaction between the small GTPase Ran/Gsp1p and Ntf2p is required for Nuclear Transport.
Molecular and cellular biology, 1997Co-Authors: D. H. Wong, Murray Stewart, Anita H. Corbett, H M Kent, Pamela A SilverAbstract:Bidirectional movement of proteins and RNAs across the Nuclear envelope requires Ran, a Ras-like GTPase. A genetic screen of the yeast Saccharomyces cerevisiae was performed to isolate conditional alleles of GSP1, a gene that encodes a homolog of Ran. Two temperature-sensitive alleles, gsp1-1 and gsp1-2, were isolated. The mutations in these two alleles map to regions that are structurally conserved between different members of the Ras family. Each mutant strain exhibits various Nuclear Transport defects. Both biochemical and genetic experiments indicate a decreased interaction between Ntf2p, a factor which is required for protein import, and the mutant GSP1 gene products. Overexpression of NTF2 can suppress the temperature sensitive phenotype of gsp1-1 and gsp1-2 and partially rescue Nuclear Transport defects. However, overexpression of a mutant allele of NTF2 with decreased binding to Gsp1p cannot rescue the temperature sensitivity of gsp1-1 and gsp1-2. Taken together, these data demonstrate that the interaction between Gsp1p and Ntf2p is critical for Nuclear Transport.
Ralph H. Kehlenbach - One of the best experts on this subject based on the ideXlab platform.
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The cargo spectrum of Nuclear Transport receptors
Current opinion in cell biology, 2018Co-Authors: Imke Baade, Ralph H. KehlenbachAbstract:The molecular mechanisms of Nuclear Transport have been described in great detail and we are beginning to understand the structures of Transport complexes and even of subcomplexes of the Nuclear pore at an atomic or near-atomic resolution. The complexity of the clients that use the Transport machinery, by contrast, is less well understood, although some Transport receptors are reported to have hundreds of different cargoes and others only a few. Here, we review the recent attempts to define the cargo spectrum of individual Nuclear Transport receptors using bioinformatic, biochemical and cell biological approaches and compare the results obtained by these complementary methods. Remarkably, a large fraction of the soluble proteome can be subject to nucleocytoplasmic Transport.
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Phosphorylation of the Nuclear Transport machinery down-regulates Nuclear protein import in vitro.
The Journal of biological chemistry, 2000Co-Authors: Ralph H. Kehlenbach, Larry GeraceAbstract:Abstract We have examined whether signal-mediated nucleocytoplasmic Transport can be regulated by phosphorylation of the Nuclear Transport machinery. Using digitonin-permeabilized cell assays to measure Nuclear import and export, we found that the phosphatase inhibitors okadaic acid and microcystin inhibit Transport mediated by the import receptors importin β and Transportin, but not by the export receptor CRM1. Several lines of evidence, including the finding that Transport inhibition is partially reversed by the broad specificity protein kinase inhibitor staurosporine, indicate that Transport inhibition is due to elevated phosphorylation of a component of the Nuclear Transport machinery. The kinases and phosphatases involved in this regulation are present in the permeabilized cells. A phosphorylation-sensitive component of the Nuclear Transport machinery also is present in permeabilized cells and is most likely a component of the Nuclear pore complex. Substrate binding by the importin α·β complex and the association of the complex with the nucleoporins Nup358/RanBP2 and Nup153 are not affected by phosphatase inhibitors, suggesting that Transport inhibition by protein phosphorylation does not involve these steps. These results suggest that cells have mechanisms to negatively regulate entire Nuclear Transport pathways, thus providing a means to globally control cellular activity through effects on nucleocytoplasmic trafficking.
