scholarly journals A Mechanism for Nuclear Positioning in Fission Yeast Based on Microtubule Pushing

2001 ◽  
Vol 153 (2) ◽  
pp. 397-412 ◽  
Author(s):  
P.T. Tran ◽  
L. Marsh ◽  
V. Doye ◽  
S. Inoué ◽  
F. Chang
Keyword(s):  
Spatial Organization ◽  
Fluorescent Protein ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Protein Markers ◽  
Division Plane ◽  
Attachment Sites ◽  
Green Fluorescent ◽  
Transient Forces ◽  
Cell Division Plane

The correct positioning of the nucleus is often important in defining the spatial organization of the cell, for example, in determining the cell division plane. In interphase Schizosaccharomyces pombe cells, the nucleus is positioned in the middle of the cylindrical cell in an active microtubule (MT)-dependent process. Here, we used green fluorescent protein markers to examine the dynamics of MTs, spindle pole body, and the nuclear envelope in living cells. We find that interphase MTs are organized in three to four antiparallel MT bundles arranged along the long axis of the cell, with MT plus ends facing both the cell tips and minus ends near the middle of the cell. The MT bundles are organized from medial MT-organizing centers that may function as nuclear attachment sites. When MTs grow to the cell tips, they exert transient forces produced by plus end MT polymerization that push the nucleus. After an average of 1.5 min of growth at the cell tip, MT plus ends exhibit catastrophe and shrink back to the nuclear region before growing back to the cell tip. Computer modeling suggests that a balance of these pushing MT forces can provide a mechanism to position the nucleus at the middle of the cell.

UNC-84 localizes to the nuclear envelope and is required for nuclear migration and anchoring during C. elegans development

Development ◽  
1999 ◽  
Vol 126 (14) ◽  
pp. 3171-3181 ◽  
Author(s):  
C.J. Malone ◽  
W.D. Fixsen ◽  
H.R. Horvitz ◽  
M. Han
Keyword(s):  
Nuclear Envelope ◽  
Fluorescent Protein ◽  
Transmembrane Domain ◽  
Spindle Pole Body ◽  
Nuclear Migration ◽  
Spindle Pole ◽  
Dna Lesions ◽  
Body Protein ◽  
C Elegans ◽  
Green Fluorescent

Nuclear migrations are essential for metazoan development. Two nuclear migrations that occur during C. elegans development require the function of the unc-84 gene. unc-84 mutants are also defective in the anchoring of nuclei within the hypodermal syncytium and in the migrations of the two distal tip cells of the gonad. Complementation analyses of 17 unc-84 alleles defined two genetically separable functions. Both functions are required for nuclear and distal tip cell migrations, but only one is required for nuclear anchorage. The DNA lesions associated with these 17 mutations indicate that the two genetically defined functions correspond to two distinct regions of the UNC-84 protein. The UNC-84 protein has a predicted transmembrane domain and a C-terminal region with similarity to the S. pombe spindle pole body protein Sad1 and to two predicted mammalian proteins. Analysis of a green fluorescent protein reporter indicated that UNC-84 is widely expressed and localized to the nuclear envelope. We propose that UNC-84 functions to facilitate a nuclear-centrosomal interaction required for nuclear migration and anchorage.

scholarly journals FH3, A Domain Found in Formins, Targets the Fission Yeast Formin Fus1 to the Projection Tip During Conjugation

1998 ◽  
Vol 141 (5) ◽  
pp. 1217-1228 ◽  
Author(s):  
Janni Petersen ◽  
Olaf Nielsen ◽  
Richard Egel ◽  
Iain M. Hagan
Keyword(s):  
Fluorescent Protein ◽  
Protein Localization ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Amino Terminal ◽  
Gfp Fusion Protein ◽  
Pole Body ◽  
Body Component ◽  
Green Fluorescent ◽  
Amino Terminal Domain

Formins are involved in diverse aspects of morphogenesis, and share two regions of homology: FH1 and FH2. We describe a new formin homology region, FH3. FH3 is an amino-terminal domain that differs from the Rho binding site identified in Bni1p and p140mDia. The Schizosaccharomyces pombe formin Fus1 is required for conjugation, and is localized to the projection tip in cells of mating pairs. We replaced genomic fus1+ with green fluorescent protein (GFP)- tagged versions that lacked either the FH1, FH2, or FH3 domain. Deletion of any FH domain essentially abolished mating. FH3, but neither FH1 nor FH2, was required for Fus1 localization. An FH3 domain–GFP fusion protein localized to the projection tips of mating pairs. Thus, the FH3 domain alone can direct protein localization. The FH3 domains of both Fus1 and the S. pombe cytokinesis formin Cdc12 were able to localize GFP to the spindle pole body in half of the late G2 cells in a vegetatively growing population. Expression of both FH3-GFP fusions also affected cytokinesis. Overexpression of the spindle pole body component Sad1 altered the distribution of both Sad1 and the FH3-GFP domain. Together these data suggest that proteins at multiple sites can interact with FH3 domains.

scholarly journals The 14-kDa Dynein Light Chain-Family Protein Dlc1 Is Required for Regular Oscillatory Nuclear Movement and Efficient Recombination during Meiotic Prophase in Fission Yeast

2002 ◽  
Vol 13 (3) ◽  
pp. 930-946 ◽  
Author(s):  
Futaba Miki ◽  
Koei Okazaki ◽  
Mizuki Shimanuki ◽  
Ayumu Yamamoto ◽  
Yasushi Hiraoka ◽  
...  
Keyword(s):  
Light Chain ◽  
Meiotic Prophase ◽  
Fluorescent Protein ◽  
Spindle Pole Body ◽  
Cytoplasmic Dynein ◽  
Spindle Pole ◽  
Cell Cortex ◽  
Dynein Light Chain ◽  
Nuclear Movement ◽  
Green Fluorescent

A Schizosaccharomyces pombe spindle pole body (SPB) protein interacts in a two-hybrid system with Dlc1, which belongs to the 14-kDa Tctex-1 dynein light chain family. Green fluorescent protein-tagged Dlc1 accumulated at the SPB throughout the life cycle. During meiotic prophase, Dlc1 was present along astral microtubules and microtubule-anchoring sites on the cell cortex, reminiscent of the cytoplasmic dynein heavy chain Dhc1. In a dlc1-null mutant, Dhc1-dependent nuclear movement in meiotic prophase became irregular in its duration and direction. Dhc1 protein was displaced from the cortex anchors and the formation of microtubule bundle(s) that guide nuclear movement was impaired in the mutant. Meiotic recombination in the dlc1 mutant was reduced to levels similar to that in the dhc1 mutant. Dlc1 and Dhc1 also have roles in karyogamy and rDNA relocation during the sexual phase. Strains mutated in both the dlc1 and dhc1loci displayed more severe defects in recombination, karyogamy, and sporulation than in either single mutant alone, suggesting that Dlc1 is involved in nuclear events that are independent of Dhc1. S. pombe contains a homolog of the 8-kDa dynein light chain, Dlc2. This class of dynein light chain, however, is not essential in either the vegetative or sexual phases.

scholarly journals Time-Lapse Video Microscopy Analysis Reveals Astral Microtubule Detachment in the Yeast Spindle Pole Mutantcnm67

2000 ◽  
Vol 11 (4) ◽  
pp. 1197-1211 ◽  
Author(s):  
Dominic Hoepfner ◽  
Arndt Brachat ◽  
Peter Philippsen
Keyword(s):  
Fluorescent Protein ◽  
Spindle Pole Body ◽  
Attachment Site ◽  
Time Lapse ◽  
Spindle Pole ◽  
Cell Cycles ◽  
Astral Microtubule ◽  
Normal Behavior ◽  
Green Fluorescent ◽  
Diploid Cells

Saccharomyces cerevisiae cnm67Δ cells lack the spindle pole body (SPB) outer plaque, the main attachment site for astral (cytoplasmic) microtubules, leading to frequent nuclear segregation failure. We monitored dynamics of green fluorescent protein–labeled nuclei and microtubules over several cell cycles. Early nuclear migration steps such as nuclear positioning and spindle orientation were slightly affected, but late phases such as rapid oscillations and insertion of the anaphase nucleus into the bud neck were mostly absent. Analyzes of microtubule dynamics revealed normal behavior of the nuclear spindle but frequent detachment of astral microtubules after SPB separation. Concomitantly, Spc72 protein, the cytoplasmic anchor for the γ-tubulin complex, was partially lost from the SPB region with dynamics similar to those observed for microtubules. We postulate that in cnm67Δ cells Spc72–γ-tubulin complex-capped astral microtubules are released from the half-bridge upon SPB separation but fail to be anchored to the cytoplasmic side of the SPB because of the absence of an outer plaque. However, successful nuclear segregation in cnm67Δ cells can still be achieved by elongation forces of spindles that were correctly oriented before astral microtubule detachment by action of Kip3/Kar3 motors. Interestingly, the first nuclear segregation in newborn diploid cells never fails, even though astral microtubule detachment occurs.

scholarly journals Coordinated Spindle Assembly and Orientation Requires Clb5p-Dependent Kinase in Budding Yeast

2000 ◽  
Vol 148 (3) ◽  
pp. 441-452 ◽  
Author(s):  
Marisa Segal ◽  
Duncan J. Clarke ◽  
Paul Maddox ◽  
E.D. Salmon ◽  
Kerry Bloom ◽  
...  
Keyword(s):  
Fluorescent Protein ◽  
Budding Yeast ◽  
Spindle Pole Body ◽  
Spindle Assembly ◽  
Time Lapse ◽  
Spindle Pole ◽  
Cell Cortex ◽  
Dynamic Interactions ◽  
Yeast Saccharomyces Cerevisiae ◽  
Green Fluorescent

The orientation of the mitotic spindle along a polarity axis is critical in asymmetric cell divisions. In the budding yeast, Saccharomyces cerevisiae, loss of the S-phase B-type cyclin Clb5p under conditions of limited cyclin-dependent kinase activity (cdc28-4 clb5Δ cells) causes a spindle positioning defect that results in an undivided nucleus entering the bud. Based on time-lapse digital imaging microscopy of microtubules labeled with green fluorescent protein fusions to either tubulin or dynein, we observed that the asymmetric behavior of the spindle pole bodies during spindle assembly was lost in the cdc28-4 clb5Δ cells. As soon as a spindle formed, both poles were equally likely to interact with the bud cell cortex. Persistent dynamic interactions with the bud ultimately led to spindle translocation across the bud neck. Thus, the mutant failed to assign one spindle pole body the task of organizing astral microtubules towards the mother cell. Our data suggest that Clb5p-associated kinase is required to confer mother-bound behavior to one pole in order to establish correct spindle polarity. In contrast, B-type cyclins, Clb3p and Clb4p, though partially redundant with Clb5p for an early role in spindle morphogenesis, preferentially promote spindle assembly.

scholarly journals Microtubule Organization Requires Cell Cycle-dependent Nucleation at Dispersed Cytoplasmic Sites: Polar and Perinuclear Microtubule Organizing Centers in the Plant Pathogen Ustilago maydis

2003 ◽  
Vol 14 (2) ◽  
pp. 642-657 ◽  
Author(s):  
Anne Straube ◽  
Marianne Brill ◽  
Berl R. Oakley ◽  
Tetsuya Horio ◽  
Gero Steinberg
Keyword(s):  
Cell Cycle ◽  
Fluorescent Protein ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Microtubule Organization ◽  
Microtubule Organizing Centers ◽  
Nucleation Sites ◽  
Cycle Dependent ◽  
Green Fluorescent

Growth of most eukaryotic cells requires directed transport along microtubules (MTs) that are nucleated at nuclear-associated microtubule organizing centers (MTOCs), such as the centrosome and the fungal spindle pole body (SPB). Herein, we show that the pathogenic fungusUstilago maydis uses different MT nucleation sites to rearrange MTs during the cell cycle. In vivo observation of green fluorescent protein-MTs and MT plus-ends, tagged by a fluorescent EB1 homologue, provided evidence for antipolar MT orientation and dispersed cytoplasmic MT nucleating centers in unbudded cells. On budding γ-tubulin containing MTOCs formed at the bud neck, and MTs reorganized with >85% of all minus-ends being focused toward the growth region. Experimentally induced lateral budding resulted in MTs that curved out of the bud, again supporting the notion that polar growth requires polar MT nucleation. Depletion or overexpression of Tub2, the γ-tubulin from U. maydis, affected MT number in interphase cells. The SPB was inactive in G2 phase but continuously recruited γ-tubulin until it started to nucleate mitotic MTs. Taken together, our data suggest that MT reorganization in U. maydis depends on cell cycle-specific nucleation at dispersed cytoplasmic sites, at a polar MTOC and the SPB.

scholarly journals Characterization of a Fission Yeast SUMO-1 Homologue, Pmt3p, Required for Multiple Nuclear Events, Including the Control of Telomere Length and Chromosome Segregation

1999 ◽  
Vol 19 (12) ◽  
pp. 8660-8672 ◽  
Author(s):  
Katsunori Tanaka ◽  
Junko Nishide ◽  
Koei Okazaki ◽  
Hiroaki Kato ◽  
Osami Niwa ◽  
...  
Keyword(s):  
Fission Yeast ◽  
Telomere Length ◽  
Chromosome Segregation ◽  
Protein Modification ◽  
Fluorescent Protein ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Nuclear Events ◽  
Posttranslational Protein Modification ◽  
Green Fluorescent

ABSTRACT Unlike ubiquitin, the ubiquitin-like protein modifier SUMO-1 and its budding yeast homologue Smt3p have been shown to be more important for posttranslational protein modification than for protein degradation. Here we describe the identification of the SUMO-1 homologue of fission yeast, which we show to be required for a number of nuclear events including the control of telomere length and chromosome segregation. A disruption of thepmt3 + gene, the Schizosaccharomyces pombe homologue of SMT3, was not lethal, but mutant cells carrying the disrupted gene grew more slowly. Thepmt3Δ cells showed various phenotypes such as aberrant mitosis, sensitivity to various reagents, and high-frequency loss of minichromosomes. Interestingly, we found thatpmt3 + is required for telomere length maintenance. Loss of Pmt3p function caused a striking increase in telomere length. When Pmt3p synthesis was restored, the telomeres became gradually shorter. This is the first demonstration of involvement of one of the Smt3p/SUMO-1 family proteins in telomere length maintenance. Fusion of Pmt3p to green fluorescent protein (GFP) showed that Pmt3p was predominantly localized as intense spots in the nucleus. One of the spots was shown to correspond to the spindle pole body (SPB). During prometaphase- and metaphase, the bright GFP signals at the SPB disappeared. These observations suggest that Pmt3p is required for kinetochore and/or SPB functions involved in chromosome segregation. The multiple functions of Pmt3p described here suggest that several nuclear proteins are regulated by Pmt3p conjugation.

scholarly journals Slk19p Is a Centromere Protein That Functions to Stabilize Mitotic Spindles

1999 ◽  
Vol 146 (2) ◽  
pp. 415-425 ◽  
Author(s):  
Xuemei Zeng ◽  
Jason A. Kahana ◽  
Pamela A. Silver ◽  
Mary K. Morphew ◽  
J. Richard McIntosh ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Fluorescent Protein ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Mitotic Spindles ◽  
Synthetic Lethal ◽  
Pole Body ◽  
Spindle Midzone ◽  
Green Fluorescent ◽  
Spindle Structure

We have identified a novel centromere-associated gene product from Saccharomyces cerevisiae that plays a role in spindle assembly and stability. Strains with a deletion of SLK19 (synthetic lethal Kar3p gene) exhibit abnormally short mitotic spindles, increased numbers of astral microtubules, and require the presence of the kinesin motor Kar3p for viability. When cells are deprived of both Slk19p and Kar3p, rapid spindle breakdown and mitotic arrest is observed. A functional fusion of Slk19p to green fluorescent protein (GFP) localizes to kinetochores and, during anaphase, to the spindle midzone, whereas Kar3p-GFP was found at the nuclear side of the spindle pole body. Thus, these proteins seem to play overlapping roles in stabilizing spindle structure while acting from opposite ends of the microtubules.

scholarly journals Formation of Spindle Poles by Dynein/Dynactin-Dependent Transport of Numa

2000 ◽  
Vol 149 (4) ◽  
pp. 851-862 ◽  
Author(s):  
Andreas Merdes ◽  
Rebecca Heald ◽  
Kumiko Samejima ◽  
William C. Earnshaw ◽  
Don W. Cleveland
Keyword(s):  
Fluorescent Protein ◽  
Gel Filtration ◽  
Cytoplasmic Dynein ◽  
Spindle Pole ◽  
Nuclear Envelope Breakdown ◽  
Spindle Poles ◽  
Mitotic Spindle Assembly ◽  
Green Fluorescent ◽  
Dependent Transport ◽  
Dynactin Complex

NuMA is a large nuclear protein whose relocation to the spindle poles is required for bipolar mitotic spindle assembly. We show here that this process depends on directed NuMA transport toward microtubule minus ends powered by cytoplasmic dynein and its activator dynactin. Upon nuclear envelope breakdown, large cytoplasmic aggregates of green fluorescent protein (GFP)-tagged NuMA stream poleward along spindle fibers in association with the actin-related protein 1 (Arp1) protein of the dynactin complex and cytoplasmic dynein. Immunoprecipitations and gel filtration demonstrate the assembly of a reversible, mitosis-spe-cific complex of NuMA with dynein and dynactin. NuMA transport is required for spindle pole assembly and maintenance, since disruption of the dynactin complex (by increasing the amount of the dynamitin subunit) or dynein function (with an antibody) strongly inhibits NuMA translocation and accumulation and disrupts spindle pole assembly.

scholarly journals Microtubule-Mediated and Microtubule-Independent Transport of Adenovirus Type 5 in HEK293 Cells

2007 ◽  
Vol 81 (13) ◽  
pp. 6899-6908 ◽  
Author(s):  
Carmen Yea ◽  
Joanna Dembowy ◽  
Laura Pacione ◽  
Martha Brown
Keyword(s):  
Viral Genome ◽  
Fluorescent Protein ◽  
Cluster Formation ◽  
Adenovirus Type ◽  
Spindle Pole ◽  
Hek293 Cells ◽  
Productive Infection ◽  
Microtubule Organizing Center ◽  
293 Cells ◽  
Green Fluorescent

ABSTRACT Adenovirus serotypes 2 and 5 are taken into cells by receptor-mediated endocytosis, and following release from endosomes, destabilized virions travel along microtubules to accumulate around the nucleus. The entry process culminates in delivery of the viral genome through nuclear pores. This model is based on studies with conventional cell lines, such as HeLa and HEp-2, but in HEK293 cells, which are routinely used in this laboratory because they are permissive for replication of multiple adenovirus serotypes, a different trafficking pattern has been observed. Nuclei of 293 cells have an irregular shape, with an indented region, and virions directly labeled with carboxyfluorescein accumulate in a cluster within that indented region. The clusters, which form in close proximity to the microtubule organizing center (MTOC) and to the Golgi apparatus, are remarkably stable; a fluorescent signal can be seen in the MTOC region up to 16 h postinfection. Furthermore, if cells are infected and then undergo mitosis after the cluster is formed, the signal is found at each spindle pole. Despite the sequestration of virions near the MTOC, 293 cells are no less sensitive than other cells to productive infection with adenovirus. Even though cluster formation depends on intact microtubules, infectivity is not compromised by disruption of microtubules with either nocodazole or colchicine, as determined by expression of an enhanced green fluorescent protein reporter gene inserted in the viral genome. These results indicate that virion clusters do not represent the infectious pathway and suggest an alternative route to the nucleus that does not depend on nocodazole-sensitive microtubules.

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