scholarly journals The mobile nucleoporin Nup2p and chromatin-bound Prp20p function in endogenous NPC-mediated transcriptional control

2005 ◽  
Vol 171 (6) ◽  
pp. 955-965 ◽  
Author(s):  
David J. Dilworth ◽  
Alan J. Tackett ◽  
Richard S. Rogers ◽  
Eugene C. Yi ◽  
Rowan H. Christmas ◽  
...  
Keyword(s):  
Transcriptional Activation ◽  
Transcriptional Control ◽  
Active Role ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Nucleotide Exchange ◽  
Control Of Gene Expression ◽  
Macromolecular Transport ◽  
Protein Components ◽  
Pore Complexes

Nuclear pore complexes (NPCs) govern macromolecular transport between the nucleus and cytoplasm and serve as key positional markers within the nucleus. Several protein components of yeast NPCs have been implicated in the epigenetic control of gene expression. Among these, Nup2p is unique as it transiently associates with NPCs and, when artificially tethered to DNA, can prevent the spread of transcriptional activation or repression between flanking genes, a function termed boundary activity. To understand this function of Nup2p, we investigated the interactions of Nup2p with other proteins and with DNA using immunopurifications coupled with mass spectrometry and microarray analyses. These data combined with functional assays of boundary activity and epigenetic variegation suggest that Nup2p and the Ran guanylyl-nucleotide exchange factor, Prp20p, interact at specific chromatin regions and enable the NPC to play an active role in chromatin organization by facilitating the transition of chromatin between activity states.

scholarly journals A nuclear pore sub-complex restricts the propagation of Ty retrotransposons by limiting their transcription

PLoS Genetics ◽  
2021 ◽  
Vol 17 (11) ◽  
pp. e1009889
Author(s):  
Amandine Bonnet ◽  
Carole Chaput ◽  
Noé Palmic ◽  
Benoit Palancade ◽  
Pascale Lesage
Keyword(s):  
Transcriptional Control ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Ltr Retrotransposons ◽  
Loss Of Function ◽  
Protein Coding ◽  
Multiple Copies ◽  
Ty1 Retrotransposition ◽  
Pore Complexes ◽  
The Impact

Beyond their canonical function in nucleocytoplasmic exchanges, nuclear pore complexes (NPCs) regulate the expression of protein-coding genes. Here, we have implemented transcriptomic and molecular methods to specifically address the impact of the NPC on retroelements, which are present in multiple copies in genomes. We report a novel function for the Nup84 complex, a core NPC building block, in specifically restricting the transcription of LTR-retrotransposons in yeast. Nup84 complex-dependent repression impacts both Copia and Gypsy Ty LTR-retrotransposons, all over the S. cerevisiae genome. Mechanistically, the Nup84 complex restricts the transcription of Ty1, the most active yeast retrotransposon, through the tethering of the SUMO-deconjugating enzyme Ulp1 to NPCs. Strikingly, the modest accumulation of Ty1 RNAs caused by Nup84 complex loss-of-function is sufficient to trigger an important increase of Ty1 cDNA levels, resulting in massive Ty1 retrotransposition. Altogether, our study expands our understanding of the complex interactions between retrotransposons and the NPC, and highlights the importance for the cells to keep retrotransposon under tight transcriptional control.

scholarly journals The nucleoporin Nup50 activates the Ran guanyl-nucleotide exchange factor RCC1 to promote mitotic NPC assembly

2021 ◽  
Author(s):  
Guillaume Holzer ◽  
Paola De Magistris ◽  
Cathrin Gramminger ◽  
Ruchika Sachdev ◽  
Adriana Magalska ◽  
...  
Keyword(s):  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Nucleotide Exchange ◽  
Exchange Factor ◽  
Nucleotide Exchange Factor ◽  
Egg Extracts ◽  
Importin Α ◽  
Pore Complexes ◽  
Xenopus Egg Extracts

During mitotic exit, thousands of nuclear pore complexes (NPCs) assemble concomitant with the nuclear envelope to build a transport-competent nucleus. We show here that Nup50 plays a crucial role in NPC assembly that is independent of its well-established function in nuclear transport. RNAi-mediated downregulation in cells or immunodepletion of the protein in Xenopus egg extracts interferes with NPC assembly. We define a conserved central region of 46 residues in Nup50 that is crucial for Nup153 and MEL28/ELYS binding, and NPC interaction. Surprisingly, neither NPC interaction nor binding of Nup50 to importin α, β, the GTPase Ran or chromatin is crucial for its function in the assembly process. Instead, we discovered that an N-terminal fragment of Nup50 can stimulate the Ran guanine exchange factor RCC1 and NPC assembly, indicating that Nup50 acts via the Ran system in mitotic NPC reformation. In support of this conclusion, Nup50 mutants defective in RCC1 binding and stimulation cannot replace the wild type protein in in vitro NPC assembly assays.

scholarly journals Involvement in surface antigen expression by a moonlighting FG-repeat nucleoporin in trypanosomes

2018 ◽  
Vol 29 (9) ◽  
pp. 1100-1110
Author(s):  
Jennifer M. Holden ◽  
Ludek Koreny ◽  
Samson Obado ◽  
Alexander V. Ratushny ◽  
Wei-Ming Chen ◽  
...  
Keyword(s):  
Transcriptional Regulation ◽  
Cell Cycle Progression ◽  
Nuclear Periphery ◽  
Antigen Expression ◽  
Nucleocytoplasmic Transport ◽  
Surface Proteins ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Control Of Gene Expression ◽  
Macromolecular Transport

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.

scholarly journals Ran-binding protein 5 (RanBP5) is related to the nuclear transport factor importin-beta but interacts differently with RanBP1.

1997 ◽  
Vol 17 (9) ◽  
pp. 5087-5096 ◽  
Author(s):  
R Deane ◽  
W Schäfer ◽  
H P Zimmermann ◽  
L Mueller ◽  
D Görlich ◽  
...  
Keyword(s):  
Nuclear Transport ◽  
Binding Protein ◽  
Nucleocytoplasmic Transport ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Nucleotide Exchange ◽  
Transport Pathway ◽  
Importin Beta ◽  
Pore Complexes

We report the identification and characterization of a novel 124-kDa Ran binding protein, RanBP5. This protein is related to importin-beta, the key mediator of nuclear localization signal (NLS)-dependent nuclear transport. RanBP5 was identified by two independent methods: it was isolated from HeLa cells by using its interaction with RanGTP in an overlay assay to monitor enrichment, and it was also found by the yeast two-hybrid selection method with RanBP1 as bait. RanBP5 binds to RanBP1 as part of a trimeric RanBP1-Ran-RanBP5 complex. Like importin-beta, RanBP5 strongly binds the GTP-bound form of Ran, stabilizing it against both intrinsic and RanGAP1-induced GTP hydrolysis and also against nucleotide exchange. The GAP resistance of the RanBP5-RanGTP complex can be relieved by RanBP1, which might reflect an in vivo role for RanBP1. RanBP5 is a predominantly cytoplasmic protein that can bind to nuclear pore complexes. We propose that RanBP5 is a mediator of a nucleocytoplasmic transport pathway that is distinct from the importin-alpha-dependent import of proteins with a classical NLS.

Structure and Assembly of the Nuclear Pore Complex

2019 ◽  
Vol 48 (1) ◽  
pp. 515-536 ◽  
Author(s):  
Bernhard Hampoelz ◽  
Amparo Andres-Pons ◽  
Panagiotis Kastritis ◽  
Martin Beck
Keyword(s):  
Posttranslational Modifications ◽  
Current Knowledge ◽  
Protein Complexes ◽  
Hierarchical Organization ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Multiple Copies ◽  
Architectural Principles ◽  
Protein Components ◽  
Pore Complexes

Nuclear pore complexes (NPCs) mediate nucleocytoplasmic exchange. They are exceptionally large protein complexes that fuse the inner and outer nuclear membranes to form channels across the nuclear envelope. About 30 different protein components, termed nucleoporins, assemble in multiple copies into an intricate cylindrical architecture. Here, we review our current knowledge of the structure of nucleoporins and how those come together in situ. We delineate architectural principles on several hierarchical organization levels, including isoforms, posttranslational modifications, nucleoporins, and higher-order oligomerization of nucleoporin subcomplexes. We discuss how cells exploit this modularity to faithfully assemble NPCs.

scholarly journals O-GlcNAc modification of nuclear pore complexes accelerates bidirectional transport

2021 ◽  
Vol 220 (7) ◽  
Author(s):  
Tae Yeon Yoo ◽  
Timothy J. Mitchison
Keyword(s):  
Nucleocytoplasmic Transport ◽  
Nuclear Pore ◽  
Permeability Barrier ◽  
Nuclear Pore Complexes ◽  
Facilitated Diffusion ◽  
Macromolecular Transport ◽  
Superresolution Imaging ◽  
Bidirectional Transport ◽  
Import And Export ◽  
Pore Complexes

Macromolecular transport across the nuclear envelope depends on facilitated diffusion through nuclear pore complexes (NPCs). The interior of NPCs contains a permeability barrier made of phenylalanine-glycine (FG) repeat domains that selectively facilitates the permeation of cargoes bound to nuclear transport receptors (NTRs). FG-repeat domains in NPCs are a major site of O-linked N-acetylglucosamine (O-GlcNAc) modification, but the functional role of this modification in nucleocytoplasmic transport is unclear. We developed high-throughput assays based on optogenetic probes to quantify the kinetics of nuclear import and export in living human cells. We found that increasing O-GlcNAc modification of the NPC accelerated NTR-facilitated transport of proteins in both directions, and decreasing modification slowed transport. Superresolution imaging revealed strong enrichment of O-GlcNAc at the FG-repeat barrier. O-GlcNAc modification also accelerated passive permeation of a small, inert protein through NPCs. We conclude that O-GlcNAc modification accelerates nucleocytoplasmic transport by enhancing the nonspecific permeability of the FG-repeat barrier, perhaps by steric inhibition of interactions between FG repeats.

scholarly journals The intranuclear mobility of messenger RNA binding proteins is ATP dependent and temperature sensitive

2002 ◽  
Vol 159 (5) ◽  
pp. 795-805 ◽  
Author(s):  
Alexandre Calapez ◽  
Henrique M. Pereira ◽  
Angelo Calado ◽  
José Braga ◽  
José Rino ◽  
...  
Keyword(s):  
Molecular Motors ◽  
Messenger Rna ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Nuclear Pore ◽  
Temperature Sensitive ◽  
Nuclear Pore Complexes ◽  
Messenger Ribonucleoprotein ◽  
Protein Components ◽  
Pore Complexes

fAter being released from transcription sites, messenger ribonucleoprotein particles (mRNPs) must reach the nuclear pore complexes in order to be translocated to the cytoplasm. Whether the intranuclear movement of mRNPs results largely from Brownian motion or involves molecular motors remains unknown. Here we have used quantitative photobleaching techniques to monitor the intranuclear mobility of protein components of mRNPs tagged with GFP. The results show that the diffusion coefficients of the poly(A)-binding protein II (PABP2) and the export factor TAP are significantly reduced when these proteins are bound to mRNP complexes, as compared with nonbound proteins. The data further show that the mobility of wild-type PABP2 and TAP, but not of a point mutant variant of PABP2 that fails to bind to RNA, is significantly reduced when cells are ATP depleted or incubated at 22°C. Energy depletion has only minor effects on the intranuclear mobility of a 2,000-kD dextran (which corresponds approximately in size to 40S mRNP particles), suggesting that the reduced mobility of PABP2 and TAP is not caused by a general alteration of the nuclear environment. Taken together, the data suggest that the mobility of mRNPs in the living cell nucleus involves a combination of passive diffusion and ATP-dependent processes.

scholarly journals A nuclear pore sub-complex restricts the propagation of Ty retrotransposons by limiting their transcription

2021 ◽  
Author(s):  
Amandine Bonnet ◽  
Carole Chaput ◽  
Benoit Palancade ◽  
Pascale Lesage
Keyword(s):  
Transcriptional Control ◽  
Genetic Material ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Ltr Retrotransposons ◽  
Loss Of Function ◽  
Canonical Function ◽  
Ty1 Retrotransposition ◽  
Pore Complexes ◽  
The Impact

ABSTRACTBeyond their canonical function in nucleocytoplasmic exchanges, nuclear pore complexes (NPCs) regulate the expression of protein-coding genes. Here, we have implemented transcriptomic and molecular methods to specifically address the impact of the NPC on retroelements, which are present in multiple copies in genomes. We report a novel function for the Nup84 complex, a core NPC building block, in specifically restricting the transcription of LTR-retrotransposons in yeast. Nup84 complex-dependent repression impacts both Copia and Gypsy Ty LTR-retrotransposons, all over the S. cerevisiae genome. Mechanistically, the Nup84 complex restricts the transcription of Ty1, the most active yeast retrotransposon, through the tethering of the SUMO-deconjugating enzyme Ulp1 to NPCs. Strikingly, the modest accumulation of Ty1 RNAs caused by Nup84 complex loss-of-function is sufficient to trigger an important increase of Ty1 cDNA levels, resulting in massive Ty1 retrotransposition. Altogether, our studies expand our understanding of the complex interactions between retrotransposons and the NPC, and highlight the importance for the cells to keep retrotransposon under tight transcriptional control.AUTHOR SUMMARYRetroelements, which replicate by reverse transcription of their RNA into a cDNA that is integrated into the host genetic material, play an important role in the plasticity of eukaryotic genomes. The study of yeast retrotransposons has led to the identification of host factors that limit retroelement mobility, including components of the nuclear pore complex (NPC), most of them still awaiting mechanistic characterization. Here, we investigated the contribution of the Nup84 complex, a core NPC scaffold, to retrotransposon biology in budding yeast. Our findings uncover that the Nup84 complex restricts the transcription of phylogenetically-distinct Ty retroelements. By focusing on Ty1 retrotransposons, we provide evidence that repression by the Nup84 complex depends on the maintenance at the NPC of the SUMO-protease Ulp1, an essential enzyme of the SUMO pathway with multiple targets in the transcription machinery. We finally show that this transcriptional control is critical for genome dynamics, since a small increase in the accumulation of Ty1 RNAs leads to massive retrotransposition. Our data reveal that although relatively abundant, Ty transcripts are limiting for retrotransposition, underscoring the importance of a tight control of their expression. They also characterize a new non-canonical function of NPCs, confirming their connection with genome expression and stability.

scholarly journals The Nuclear Pore Complex consists of two independent scaffolds

2020 ◽  
Author(s):  
Saroj G. Regmi ◽  
Hangnoh Lee ◽  
Ross Kaufhold ◽  
Boris Fichtman ◽  
Shane Chen ◽  
...  
Keyword(s):  
Dynamic Assessment ◽  
Outer Ring ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Unique Role ◽  
Macromolecular Transport ◽  
Ring Complex ◽  
Multiple Copies ◽  
Ring Complexes ◽  
Pore Complexes

Macromolecular transport between the nucleus and cytoplasm is mediated through Nuclear Pore Complexes (NPCs), which are built from multiple copies of roughly 34 distinct proteins, called nucleoporins1–3. Models of the NPC depict it as a composite of several sub-domains that have been named the outer rings, inner ring, cytoplasmic fibrils and nuclear basket. While the NPC has been extensively studied, the roles of individual nucleoporins within NPCs and their functional interactions remain poorly understood. Here, we applied a rapid degron system to systematically investigate how individual nucleoporins contribute toward NPC architecture. We find that acute depletion of outer ring components (NUP96 or NUP107) disperses the outer ring and cytoplasmic fibrils without disassembly of inner ring members. Conversely, rapid degradation of the inner ring complex component NUP188 disrupts the inner ring without dislodging outer ring members. We also found that depletion of NUP93 destabilized all NPC domains, indicating that it has a unique role as a lynchpin of NPC structure. Our data highlight the modular nature of NPC organization, suggesting that the outer and inner ring complexes do not extensively rely on each other for structural stability after NPC assembly is complete. This dynamic assessment provides new insights regarding the remarkable structural independence of domains within the NPC.

Nuclear Envelope Dynamics During Mitosis

1988 ◽  
Vol 46 ◽  
pp. 224-225
Author(s):  
Brian Burke
Keyword(s):  
Nuclear Envelope ◽  
Membrane Vesicles ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Animal Cells ◽  
Interphase Chromosome ◽  
Lamin B ◽  
Chromosome Architecture ◽  
Complex Membrane ◽  
Pore Complexes

The nuclear envelope is a complex membrane structure that forms the boundary of the nuclear compartment in eukaryotes. It regulates the passage of macromolecules between the two compartments and may be important for organizing interphase chromosome architecture. In interphase animal cells it forms a remarkably stable structure consisting of a double membrane ouerlying a protein meshwork or lamina and penetrated by nuclear pore complexes. The latter form the channels for nucleocytoplasmic exchange of macromolecules, At the onset of mitosis, however, it rapidly disassembles, the membranes fragment to yield small vesicles and the lamina, which is composed of predominantly three polypeptides, lamins R, B and C (MW approx. 74, 68 and 65 kDa respectiuely), breaks down. Lamins B and C are dispersed as monomers throughout the mitotic cytoplasm, while lamin B remains associated with the nuclear membrane vesicles.

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