scholarly journals The role of karyopherins in the regulated sumoylation of septins

2007 ◽  
Vol 177 (1) ◽  
pp. 39-49 ◽  
Author(s):  
Taras Makhnevych ◽  
Christopher Ptak ◽  
C. Patrick Lusk ◽  
John D. Aitchison ◽  
Richard W. Wozniak
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Nuclear Pore Complex ◽  
Nuclear Transport ◽  
E3 Ligase ◽  
Nuclear Pore ◽  
Yeast Saccharomyces Cerevisiae ◽  
Septin Ring ◽  
M Phase

In the yeast Saccharomyces cerevisiae, several components of the septin ring are sumoylated during anaphase and then abruptly desumoylated at cytokinesis. We show that septin sumoylation is controlled by the interactions of two enzymes of the sumoylation pathway, Siz1p and Ulp1p, with the nuclear transport machinery. The E3 ligase Siz1p is imported into the nucleus by the karyopherin Kap95p during interphase. In M phase, Siz1p is exported from the nucleus by the karyopherin Kap142p/Msn5p and subsequently targeted to the septin ring, where it participates in septin sumoylation. We also show that the accumulation of sumoylated septins during mitosis is dependent on the interactions of the SUMO isopeptidase Ulp1p with Kap121p and Kap95p–Kap60p and the nuclear pore complex (NPC). In addition to sequestering Ulp1 at the NPC, Kap121p is required for targeting Ulp1p to the septin ring during mitosis. We present a model in which Ulp1p is maintained at the NPC during interphase and transiently interacts with the septin ring during mitosis.

scholarly journals GLE2, a Saccharomyces cerevisiae homologue of the Schizosaccharomyces pombe export factor RAE1, is required for nuclear pore complex structure and function.

1996 ◽  
Vol 7 (12) ◽  
pp. 1921-1937 ◽  
Author(s):  
R Murphy ◽  
J L Watkins ◽  
S R Wente
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Schizosaccharomyces Pombe ◽  
Nuclear Pore Complex ◽  
Nuclear Export ◽  
Protein Import ◽  
Nuclear Transport ◽  
Complex Structure ◽  
Striking Similarity ◽  
Nuclear Pore ◽  
Pore Complexes

To identify and characterize novel factors required for nuclear transport, a genetic screen was conducted in the yeast Saccharomyces cerevisiae. Mutations that were lethal in combination with a null allele of the gene encoding the nucleoporin Nup100p were isolated using a colony-sectoring assay. Three complementation groups of gle (for GLFG lethal) mutants were identified. In this report, the characterization of GLE2 is detailed. GLE2 encodes a 40.5-kDa polypeptide with striking similarity to that of Schizosaccharomyces pombe RAE1. In indirect immunofluorescence and nuclear pore complex fractionation experiments, Gle2p was associated with nuclear pore complexes. Mutated alleles of GLE2 displayed blockage of polyadenylated RNA export; however, nuclear protein import was not apparently diminished. Immunofluorescence and thin-section electron microscopic analysis revealed that the nuclear pore complex and nuclear envelope structure was grossly perturbed in gle2 mutants. Because the clusters of herniated pore complexes appeared subsequent to the export block, the structural perturbations were likely indirect consequences of the export phenotype. Interestingly, a two-hybrid interaction was detected between Gle2p and Srp1p, the nuclear localization signal receptor, as well as Rip1p, a nuclear export signal-interacting protein. We propose that Gle2p has a novel role in mediating nuclear transport.

scholarly journals Nuclear envelope-vacuole contacts mitigate nuclear pore complex assembly stress

2020 ◽  
Author(s):  
Christopher L. Lord ◽  
Susan R. Wente
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Nuclear Envelope ◽  
Nuclear Pore Complex ◽  
Lipid Droplets ◽  
Budding Yeast ◽  
Nuclear Transport ◽  
Nuclear Pore ◽  
Cellular Mechanisms ◽  
Complex Assembly ◽  
Cellular Effects

AbstractThe intricacy of nuclear pore complex (NPC) biogenesis imposes risks of failure that can cause defects in nuclear transport and nuclear envelope morphology, however, cellular mechanisms utilized to alleviate NPC assembly stress are not well-defined. In the budding yeast Saccharomyces cerevisiae, we demonstrate that NVJ1- and MDM1-enriched nuclear envelope (NE)-vacuole contacts increase when NPC assembly is compromised in several nup mutants, including nup116ΔGLFG cells. These interorganelle nucleus-vacuole junctions (NVJs) cooperate with lipid droplets to maintain viability and enhance NPC formation in assembly mutants. Additionally, NVJs function with ATG1 to promote vacuole-dependent remodeling in nup116ΔGLFG cells, which also correlates with proper NPC formation. Importantly, NVJs significantly improve the physiology of NPC assembly mutants, despite having only negligible effects when NPC biogenesis is unperturbed. Collectively, these results define how NE-vacuole interorganelle contacts coordinate responses to mitigate deleterious cellular effects caused by disrupted NPC assembly.SummaryHow cells respond to deleterious effects imposed by disrupted nuclear pore complex (NPC) assembly are not well-defined. The authors demonstrate nuclear envelope-vacuole interactions expand in response to perturbed NPC assembly to promote viability, nuclear envelope remodeling, and proper NPC biogenesis.

scholarly journals The role of the integral membrane nucleoporins Ndc1p and Pom152p in nuclear pore complex assembly and function

2006 ◽  
Vol 173 (3) ◽  
pp. 361-371 ◽  
Author(s):  
Alexis S. Madrid ◽  
Joel Mancuso ◽  
W. Zacheus Cande ◽  
Karsten Weis
Keyword(s):  
Electron Microscopy ◽  
Saccharomyces Cerevisiae ◽  
Nuclear Envelope ◽  
Lipid Bilayers ◽  
Nuclear Pore Complex ◽  
Transmembrane Proteins ◽  
Nuclear Pore ◽  
Large Channel ◽  
And Function

The nuclear pore complex (NPC) is a large channel that spans the two lipid bilayers of the nuclear envelope and mediates transport events between the cytoplasm and the nucleus. Only a few NPC components are transmembrane proteins, and the role of these proteins in NPC function and assembly remains poorly understood. We investigate the function of the three integral membrane nucleoporins, which are Ndc1p, Pom152p, and Pom34p, in NPC assembly and transport in Saccharomyces cerevisiae. We find that Ndc1p is important for the correct localization of nuclear transport cargoes and of components of the NPC. However, the role of Ndc1p in NPC assembly is partially redundant with Pom152p, as cells lacking both of these proteins show enhanced NPC disruption. Electron microscopy studies reveal that the absence of Ndc1p and Pom152p results in aberrant pores that have enlarged diameters and lack proteinaceous material, leading to an increased diffusion between the cytoplasm and the nucleus.

scholarly journals The yeast nuclear pore complex functionally interacts with components of the spindle assembly checkpoint

2002 ◽  
Vol 159 (5) ◽  
pp. 807-819 ◽  
Author(s):  
Tatiana Iouk ◽  
Oliver Kerscher ◽  
Robert J. Scott ◽  
Munira A. Basrai ◽  
Richard W. Wozniak
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Genetic Analysis ◽  
Nuclear Pore Complex ◽  
Spindle Assembly Checkpoint ◽  
Spindle Checkpoint ◽  
Spindle Assembly ◽  
Nuclear Pore ◽  
Yeast Saccharomyces Cerevisiae ◽  
Functional Link

Aphysical and functional link between the nuclear pore complex (NPC) and the spindle checkpoint machinery has been established in the yeast Saccharomyces cerevisiae. We show that two proteins required for the execution of the spindle checkpoint, Mad1p and Mad2p, reside predominantly at the NPC throughout the cell cycle. There they are associated with a subcomplex of nucleoporins containing Nup53p, Nup170p, and Nup157p. The association of the Mad1p–Mad2p complex with the NPC requires Mad1p and is mediated in part by Nup53p. On activation of the spindle checkpoint, we detect changes in the interactions between these proteins, including the release of Mad2p (but not Mad1p) from the NPC and the accumulation of Mad2p at kinetochores. Accompanying these events is the Nup53p-dependent hyperphosphorylation of Mad1p. On the basis of these results and genetic analysis of double mutants, we propose a model in which Mad1p bound to a Nup53p-containing complex sequesters Mad2p at the NPC until its release by activation of the spindle checkpoint. Furthermore, we show that the association of Mad1p with the NPC is not passive and that it plays a role in nuclear transport.

scholarly journals Role of the Septin Ring in the Asymmetric Localization of Proteins at the Mother-Bud Neck in Saccharomyces cerevisiae

2005 ◽  
Vol 16 (8) ◽  
pp. 3455-3466 ◽  
Author(s):  
Lukasz Kozubowski ◽  
Jennifer R. Larson ◽  
Kelly Tatchell
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Protein Kinase ◽  
Yeast Saccharomyces Cerevisiae ◽  
Septin Ring ◽  
Gtpase Activating Proteins ◽  
Latrunculin A ◽  
Bud Neck ◽  
Genes Encoding ◽  
Associated Proteins

In the yeast Saccharomyces cerevisiae, septins form a scaffold in the shape of a ring at the future budding site that rearranges into a collar at the mother-bud neck. Many proteins bind asymmetrically to the septin collar. We found that the protein Bni4-CFP was located on the exterior of the septin ring before budding and on the mother side of the collar after budding, whereas the protein kinase Kcc4-YFP was located on the interior of the septin ring before budding and moved into the bud during the formation of the septin collar. Unbudded cells treated with the actin inhibitor latrunculin-A assembled cortical caps of septins on which Bni4-CFP and Kcc4-YFP colocalized. Bni4-CFP and Kcc4-YFP also colocalized on cortical caps of septins found in strains deleted for the genes encoding the GTPase activating proteins of Cdc42 (RGA1, RGA2, and BEM3). However, Bni4-CFP and Kcc4-YFP were still partially separated in mutants (gin4, elm1, cla4, and cdc3-1) in which septin morphology was severely disrupted in other ways. These observations provide clues to the mechanisms for the asymmetric localization of septin-associated proteins.

scholarly journals In vivo nuclear transport kinetics in Saccharomyces cerevisiae: a role for heat shock protein 70 during targeting and translocation.

1996 ◽  
Vol 135 (2) ◽  
pp. 329-339 ◽  
Author(s):  
N Shulga ◽  
P Roberts ◽  
Z Gu ◽  
L Spitz ◽  
M M Tabb ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Heat Shock ◽  
Heat Shock Protein ◽  
Nuclear Pore Complex ◽  
Heat Shock Protein 70 ◽  
Nuclear Transport ◽  
T Antigen ◽  
Nuclear Pore ◽  
Wild Type

The transport of proteins into the nucleus is a receptor-mediated process that is likely to involve between 50-100 gene products, including many that comprise the nuclear pore complex. We have developed an assay in Saccharomyces cerevisiae for the nuclear transport of green fluorescent protein fused to the SV-40 large T antigen nuclear localization signal (NLS-GFP). This assay allows the measurement of relative NLS-GFP nuclear import rates in wild-type and mutant cells under various physiological conditions. Probably the best understood component of the nuclear transport apparatus is Srp1p, the NLS receptor, which binds NLS-cargo in the cytoplasm and accompanies it into the nucleus. When compared to SRP1+ cells, NLS-GFP import rates in temperature-sensitive srp1-31 cells were slower and showed a lower temperature optimum. The in vivo transport defect of the srp1-31 cells was correlated with the purified protein's thermal sensitivity, as assayed by in vitro NLS peptide binding. We show that the kinetics of NLS-directed nuclear transport in wild-type cells is stimulated by the elevated expression of SSA1, which encodes a cytoplasmic heat shock protein 70 (Hsp70). Elevated Hsp70 levels are sufficient to suppress the NLS-GFP import defects in srp1-31 and nup82-3 cells. NUP82 encodes a protein that functions within the nuclear pore complex subsequent to docking. These results provide genetic evidence that Hsp70 acts during both targeting and translocation phases of nuclear transport, possibly as a molecular chaperone to promote the formation and stability of the Srp1p-NLS-cargo complex.

scholarly journals Nuclear envelope–vacuole contacts mitigate nuclear pore complex assembly stress

2020 ◽  
Vol 219 (12) ◽  
Author(s):  
Christopher L. Lord ◽  
Susan R. Wente
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Nuclear Envelope ◽  
Nuclear Pore Complex ◽  
Lipid Droplets ◽  
Budding Yeast ◽  
Nuclear Pore ◽  
Cellular Mechanisms ◽  
Yeast Saccharomyces Cerevisiae ◽  
Complex Assembly ◽  
Cellular Effects

The intricacy of nuclear pore complex (NPC) biogenesis imposes risks of failure that can cause defects in nuclear transport and nuclear envelope (NE) morphology; however, cellular mechanisms used to alleviate NPC assembly stress are not well defined. In the budding yeast Saccharomyces cerevisiae, we demonstrate that NVJ1- and MDM1-enriched NE–vacuole contacts increase when NPC assembly is compromised in several nup mutants, including nup116ΔGLFG cells. These interorganelle nucleus–vacuole junctions (NVJs) cooperate with lipid droplets to maintain viability and enhance NPC formation in assembly mutants. Additionally, NVJs function with ATG1 to remodel the NE and promote vacuole-dependent degradation of specific nucleoporins in nup116ΔGLFG cells. Importantly, NVJs significantly improve the physiology of NPC assembly mutants, despite having only negligible effects when NPC biogenesis is unperturbed. These results therefore define how NE–vacuole interorganelle contacts coordinate responses to mitigate deleterious cellular effects caused by disrupted NPC assembly.

scholarly journals The nucleoporins Nup170p and Nup157p are essential for nuclear pore complex assembly

2009 ◽  
Vol 185 (3) ◽  
pp. 459-473 ◽  
Author(s):  
Tadashi Makio ◽  
Leslie H. Stanton ◽  
Cheng-Chao Lin ◽  
David S. Goldfarb ◽  
Karsten Weis ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Nuclear Pore Complex ◽  
Nuclear Membrane ◽  
Essential Role ◽  
Nuclear Transport ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Complex Assembly ◽  
Cytoplasmic Face ◽  
Pore Complexes

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.

Mechanisms of Nuclear Transport in the cell: RNA exosome in Saccharomyces cerevisiae

Bionatura ◽  
2020 ◽  
Vol 5 (4) ◽  
pp. 1423-1426
Author(s):  
Bruna Rech ◽  
Fernando A. Gonzales-Zubiate
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Catalytic Activity ◽  
Rna Processing ◽  
Cellular Localization ◽  
Nuclear Transport ◽  
Single Units ◽  
Yeast Saccharomyces Cerevisiae ◽  
Rna Transcripts ◽  
Non Coding Rnas ◽  
Rna Exosome

Ribonucleases (RNases) functions in the cell include precise maturation of non- coding RNAs and degradation of specific RNA transcripts that are no longer necessary. RNAses are present in the cell as single units or assembled as multimeric complexes; one of these complexes is the RNA exosome, a highly conserved complex essential for RNA processing and degradation. In the yeast Saccharomyces cerevisiae, the RNA exosome comprises eleven subunits, two with catalytic activity: Rrp6 and Rrp44, where the Rrp6 subunit is exclusively nuclear. Despite the RNA exosome has been intensively investigated since its discovery in 1997, only a few studies were accomplished concerning its nuclear transport. This review describes recent research about cellular localization and transport of this essential complex.

scholarly journals The Highly Conserved tRNAHis Guanylyltransferase Thg1p Interacts with the Origin Recognition Complex and Is Required for the G2/M Phase Transition in the Yeast Saccharomyces cerevisiae

2005 ◽  
Vol 4 (4) ◽  
pp. 832-835 ◽  
Author(s):  
Terri S. Rice ◽  
Min Ding ◽  
David S. Pederson ◽  
Nicholas H. Heintz
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Origin Recognition Complex ◽  
Nuclear Division ◽  
Permissive Temperature ◽  
Yeast Saccharomyces Cerevisiae ◽  
M Phase ◽  
And Migration ◽  
Origin Recognition

ABSTRACT Here we show that the Saccharomyces cerevisiae tRNAHis guanylyltransferase Thg1p interacts with the origin recognition complex in vivo and in vitro and that overexpression of hemagglutinin-Thg1p selectively impedes growth of orc2-1(Ts) cells at the permissive temperature. Studies with conditional mutants indicate that Thg1p couples nuclear division and migration to cell budding and cytokinesis in yeast.

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