scholarly journals Kinesin-related KIP3 of Saccharomyces cerevisiae Is Required for a Distinct Step in Nuclear Migration

1997 ◽  
Vol 138 (5) ◽  
pp. 1023-1040 ◽  
Author(s):  
Todd M. DeZwaan ◽  
Eric Ellingson ◽  
David Pellman ◽  
David M. Roof
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mitotic Spindle ◽  
Nuclear Migration ◽  
Spindle Pole ◽  
Live Cells ◽  
Spindle Orientation ◽  
Chain Gene ◽  
Null Mutant ◽  
Bud Neck ◽  
Bud Site

Spindle orientation and nuclear migration are crucial events in cell growth and differentiation of many eukaryotes. Here we show that KIP3, the sixth and final kinesin-related gene in Saccharomyces cerevisiae, is required for migration of the nucleus to the bud site in preparation for mitosis. The position of the nucleus in the cell and the orientation of the mitotic spindle was examined by microscopy of fixed cells and by time-lapse microscopy of individual live cells. Mutations in KIP3 and in the dynein heavy chain gene defined two distinct phases of nuclear migration: a KIP3-dependent movement of the nucleus toward the incipient bud site and a dynein-dependent translocation of the nucleus through the bud neck during anaphase. Loss of KIP3 function disrupts the unidirectional movement of the nucleus toward the bud and mitotic spindle orientation, causing large oscillations in nuclear position. The oscillatory motions sometimes brought the nucleus in close proximity to the bud neck, possibly accounting for the viability of a kip3 null mutant. The kip3 null mutant exhibits normal translocation of the nucleus through the neck and normal spindle pole separation kinetics during anaphase. Simultaneous loss of KIP3 and kinesin-related KAR3 function, or of KIP3 and dynein function, is lethal but does not block any additional detectable movement. This suggests that the lethality is due to the combination of sequential and possibly overlapping defects. Epitope-tagged Kip3p localizes to astral and central spindle microtubules and is also present throughout the cytoplasm and nucleus.

scholarly journals Control of Mitotic Spindle Position by the Saccharomyces cerevisiae Formin Bni1p

1999 ◽  
Vol 144 (5) ◽  
pp. 947-961 ◽  
Author(s):  
Laifong Lee ◽  
Saskia K. Klee ◽  
Marie Evangelista ◽  
Charles Boone ◽  
David Pellman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mitotic Spindle ◽  
Cortical Microtubule ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Spindle Orientation ◽  
Cell Cortex ◽  
Cortical Actin ◽  
Bud Site ◽  
Spindle Position

Alignment of the mitotic spindle with the axis of cell division is an essential process in Saccharomyces cerevisiae that is mediated by interactions between cytoplasmic microtubules and the cell cortex. We found that a cortical protein, the yeast formin Bni1p, was required for spindle orientation. Two striking abnormalities were observed in bni1Δ cells. First, the initial movement of the spindle pole body (SPB) toward the emerging bud was defective. This phenotype is similar to that previously observed in cells lacking the kinesin Kip3p and, in fact, BNI1 and KIP3 were found to be in the same genetic pathway. Second, abnormal pulling interactions between microtubules and the cortex appeared to cause preanaphase spindles in bni1Δ cells to transit back and forth between the mother and the bud. We therefore propose that Bni1p may localize or alter the function of cortical microtubule-binding sites in the bud. Additionally, we present evidence that other bipolar bud site determinants together with cortical actin are also required for spindle orientation.

scholarly journals Saccharomyces cerevisiae Mob1p Is Required for Cytokinesis and Mitotic Exit

2001 ◽  
Vol 21 (20) ◽  
pp. 6972-6983 ◽  
Author(s):  
Francis C. Luca ◽  
Manali Mody ◽  
Cornelia Kurischko ◽  
David M. Roof ◽  
Thomas H. Giddings ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Mitotic Exit ◽  
Live Cells ◽  
Ring Assembly ◽  
Spindle Poles ◽  
Spindle Pole Bodies ◽  
Bud Neck ◽  
Mitotic Cyclin

ABSTRACT The Saccharomyces cerevisiae mitotic exit network (MEN) is a conserved set of genes that mediate the transition from mitosis to G1 by regulating mitotic cyclin degradation and the inactivation of cyclin-dependent kinase (CDK). Here, we demonstrate that, in addition to mitotic exit, S. cerevisiae MEN gene MOB1 is required for cytokinesis and cell separation. The cytokinesis defect was evident in mob1mutants under conditions in which there was no mitotic-exit defect. Observation of live cells showed that yeast myosin II, Myo1p, was present in the contractile ring at the bud neck but that the ring failed to contract and disassemble. The cytokinesis defect persisted for several mitotic cycles, resulting in chains of cells with correctly segregated nuclei but with uncontracted actomyosin rings. The cytokinesis proteins Cdc3p (a septin), actin, and Iqg1p/ Cyk1p (an IQGAP-like protein) appeared to correctly localize inmob1 mutants, suggesting that MOB1functions subsequent to actomyosin ring assembly. We also examined the subcellular distribution of Mob1p during the cell cycle and found that Mob1p first localized to the spindle pole bodies during mid-anaphase and then localized to a ring at the bud neck just before and during cytokinesis. Localization of Mob1p to the bud neck requiredCDC3, MEN genes CDC5,CDC14, CDC15, and DBF2, and spindle pole body gene NUD1 but was independent ofMYO1. The localization of Mob1p to both spindle poles was abolished in cdc15 and nud1 mutants and was perturbed in cdc5 and cdc14mutants. These results suggest that the MEN functions during the mitosis-to-G1 transition to control cyclin-CDK inactivation and cytokinesis.

scholarly journals Cell shape impacts on the positioning of the mitotic spindle with respect to the substratum

2015 ◽  
Vol 26 (7) ◽  
pp. 1286-1295 ◽  
Author(s):  
Francisco Lázaro-Diéguez ◽  
Iaroslav Ispolatov ◽  
Anne Müsch
Keyword(s):  
Mitotic Spindle ◽  
Cell Shape ◽  
Spindle Assembly Checkpoint ◽  
Mdck Cells ◽  
Spindle Pole ◽  
Spindle Orientation ◽  
Cell Cortex ◽  
Spindle Positioning ◽  
Spindle Poles ◽  
Spindle Position

All known mechanisms of mitotic spindle orientation rely on astral microtubules. We report that even in the absence of astral microtubules, metaphase spindles in MDCK and HeLa cells are not randomly positioned along their x-z dimension, but preferentially adopt shallow β angles between spindle pole axis and substratum. The nonrandom spindle positioning is due to constraints imposed by the cell cortex in flat cells that drive spindles that are longer and/or wider than the cell's height into a tilted, quasidiagonal x-z position. In rounder cells, which are taller, fewer cortical constraints make the x-z spindle position more random. Reestablishment of astral microtubule–mediated forces align the spindle poles with cortical cues parallel to the substratum in all cells. However, in flat cells, they frequently cause spindle deformations. Similar deformations are apparent when confined spindles rotate from tilted to parallel positions while MDCK cells progress from prometaphase to metaphase. The spindle disruptions cause the engagement of the spindle assembly checkpoint. We propose that cell rounding serves to maintain spindle integrity during its positioning.

scholarly journals The JNM1 gene in the yeast Saccharomyces cerevisiae is required for nuclear migration and spindle orientation during the mitotic cell cycle.

1994 ◽  
Vol 125 (1) ◽  
pp. 143-158 ◽  
Author(s):  
J N McMillan ◽  
K Tatchell
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Low Temperature ◽  
Mother Cell ◽  
Significant Proportion ◽  
Nuclear Migration ◽  
Cold Sensitivity ◽  
Chain Gene ◽  
Chromosome Loss ◽  
Lacz Gene ◽  
Yeast Saccharomyces Cerevisiae

JNM1, a novel gene on chromosome XIII in the yeast Saccharomyces cerevisiae, is required for proper nuclear migration. jnm1 null mutants have a temperature-dependent defect in nuclear migration and an accompanying alteration in astral microtubules. At 30 degrees C, a significant proportion of the mitotic spindles is not properly located at the neck between the mother cell and the bud. This defect is more severe at low temperature. At 11 degrees C, 60% of the cells accumulate with large buds, most of which have two DAPI staining regions in the mother cell. Although mitosis is delayed and nuclear migration is defective in jnm1 mutant, we rarely observe more than two nuclei in a cell, nor do we frequently observe anuclear cells. No loss of viability is observed at 11 degrees C and cells continue to grow exponentially with increased doubling time. At low temperature the large budded cells of jnm1 mutants exhibit extremely long astral microtubules that often wind around the periphery of the cell. jnm1 mutants are not defective in chromosome segregation during mitosis, as assayed by the rate of chromosome loss, or nuclear migration during conjugation, as assayed by the rate of mating and cytoduction. The phenotype of a jnm1 mutant is strikingly similar to that for mutants in the dynein heavy chain gene (Eshel, D., L. A. Urrestarazu, S. Vissers, J.-C. Jauniaux, J. C. van Vliet-Reedijk, R. J. Plants, and I. R. Gibbons. 1993. Proc. Natl. Acad. Sci. USA. 90:11172-11176; Li, Y. Y., E. Yeh, T. Hays, and K. Bloom. 1993. Proc. Natl. Acad. Sci. USA. 90:10096-10100). The JNM1 gene product is predicted to encode a 44-kD protein containing three coiled coil domains. A JNM1:lacZ gene fusion is able to complement the cold sensitivity and microtubule phenotype of a jnm1 deletion strain. This hybrid protein localizes to a single spot in the cell, most often near the spindle pole body in unbudded cells and in the bud in large budded cells. Together these results point to a specific role for Jnm1p in spindle migration, possibly as a subunit or accessory protein for yeast dynein.

scholarly journals Role of astral microtubules and actin in spindle orientation and migration in the budding yeast, Saccharomyces cerevisiae.

1992 ◽  
Vol 119 (3) ◽  
pp. 583-593 ◽  
Author(s):  
R E Palmer ◽  
D S Sullivan ◽  
T Huffaker ◽  
D Koshland
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Chromosome Segregation ◽  
Mother Cell ◽  
Fold Increase ◽  
Spindle Pole ◽  
Spindle Orientation ◽  
Temperature Sensitive ◽  
Chromosome Movement ◽  
Yeast Saccharomyces Cerevisiae ◽  
Cytoskeletal Elements

In the yeast Saccharomyces cerevisiae, before the onset of anaphase, the spindle apparatus is always positioned with one spindle pole at, or through, the neck between the mother cell and the growing bud. This spindle orientation enables proper chromosome segregation to occur during anaphase, allowing one replicated genome to be segregated into the bud and the other to remain in the mother cell. In this study, we synchronized a population of cells before the onset of anaphase such that > 90% of the cells in the population had spindles with the correct orientation, and then disrupted specific cytoskeletal elements using temperature-sensitive mutations. Disruption of either the astral microtubules or actin function resulted in improper spindle orientation in approximately 40-50% of the cells. When cells with disrupted astral microtubules or actin function entered into anaphase, there was a 100-200-fold increase in the frequency of binucleated cell bodies. Thus, the maintenance of proper spindle orientation by these cytoskeletal elements was essential for proper chromosome segregation. These data are consistent with the model that proper spindle orientation is maintained by directly or indirectly tethering the astral microtubules to the actin cytoskeleton. After nuclear migration, but before anaphase, bulk chromosome movement occurs within the nucleus apparently because the chromosomes are attached to a mobile spindle. The frequency and magnitude of bulk chromosome movement is greatly diminished by disruption of the astral microtubules but not by disruption of the nonkinetochore spindle microtubules. These results suggest that astral microtubules are not only important for spindle orientation before anaphase, but they also mediate force on the spindle, generating spindle displacement and in turn chromosome movement. Potential roles for this force in spindle assembly and orientation are discussed.

scholarly journals Plk1 regulates spindle orientation by phosphorylating NuMA in human cells

2018 ◽  
Vol 1 (6) ◽  
pp. e201800223 ◽  
Author(s):  
Shrividya Sana ◽  
Riya Keshri ◽  
Ashwathi Rajeevan ◽  
Sukriti Kapoor ◽  
Sachin Kotak
Keyword(s):  
Cell Division ◽  
Mitotic Spindle ◽  
Molecular Mechanisms ◽  
Spindle Pole ◽  
Spindle Orientation ◽  
Cell Cortex ◽  
Division Plane ◽  
Evolutionarily Conserved ◽  
Cortical Localization ◽  
Proper Orientation

Proper orientation of the mitotic spindle defines the correct division plane and is essential for accurate cell division and development. In metazoans, an evolutionarily conserved complex comprising of NuMA/LGN/Gαi regulates proper orientation of the mitotic spindle by orchestrating cortical dynein levels during metaphase. However, the molecular mechanisms that modulate the spatiotemporal dynamics of this complex during mitosis remain elusive. Here, we report that acute inactivation of Polo-like kinase 1 (Plk1) during metaphase enriches cortical levels of dynein/NuMA/LGN and thus influences spindle orientation. We establish that this impact of Plk1 on cortical levels of dynein/NuMA/LGN is through NuMA, but not via dynein/LGN. Moreover, we reveal that Plk1 inhibition alters the dynamic behavior of NuMA at the cell cortex. We further show that Plk1 directly interacts and phosphorylates NuMA. Notably, NuMA-phosphorylation by Plk1 impacts its cortical localization, and this is needed for precise spindle orientation during metaphase. Overall, our finding connects spindle-pole pool of Plk1 with cortical NuMA and answers a long-standing puzzle about how spindle-pole Plk1 gradient dictates proper spindle orientation for error-free mitosis.

scholarly journals A lysine deacetylase Hos3 is targeted to the bud neck and involved in the spindle position checkpoint

2014 ◽  
Vol 25 (18) ◽  
pp. 2720-2734 ◽  
Author(s):  
Mengqiao Wang ◽  
Ruth N. Collins
Keyword(s):  
Spindle Pole Body ◽  
Neck Region ◽  
Spindle Pole ◽  
Mitotic Exit ◽  
Spindle Orientation ◽  
Lysine Deacetylase ◽  
Bud Neck ◽  
Morphogenesis Checkpoint ◽  
Spindle Position

An increasing number of cellular activities can be regulated by reversible lysine acetylation. Targeting the enzymes responsible for such posttranslational modifications is instrumental in defining their substrates and functions in vivo. Here we show that a Saccharomyces cerevisiae lysine deacetylase, Hos3, is asymmetrically targeted to the daughter side of the bud neck and to the daughter spindle pole body (SPB). The morphogenesis checkpoint member Hsl7 recruits Hos3 to the neck region. Cells with a defect in spindle orientation trigger Hos3 to load onto both SPBs. When associated symmetrically with both SPBs, Hos3 functions as a spindle position checkpoint (SPOC) component to inhibit mitotic exit. Neck localization of Hos3 is essential for its symmetric association with SPBs in cells with misaligned spindles. Our data suggest that Hos3 facilitates cross-talk between the morphogenesis checkpoint and the SPOC as a component of the intricate monitoring of spindle orientation after mitotic entry and before commitment to mitotic exit.

scholarly journals The distribution of cytoplasmic microtubules throughout the cell cycle of the centric diatom Stephanopyxis turris: their role in nuclear migration and positioning the mitotic spindle during cytokinesis.

1986 ◽  
Vol 102 (5) ◽  
pp. 1688-1698 ◽  
Author(s):  
L Wordeman ◽  
K L McDonald ◽  
W Z Cande
Keyword(s):  
Cell Cycle ◽  
Mitotic Spindle ◽  
Nuclear Migration ◽  
Spindle Pole ◽  
Centric Diatom ◽  
Mitotic Spindles ◽  
Animal Cells ◽  
Microtubule Organizing Center ◽  
Cytoplasmic Microtubule ◽  
Cytoplasmic Microtubules

The cell cycle of the marine centric diatom Stephanopyxis turris consists of a series of spatially and temporally well-ordered events. We have used immunofluorescence microscopy to examine the role of cytoplasmic microtubules in these events. At interphase, microtubules radiate out from the microtubule-organizing center, forming a network around the nucleus and extending much of the length and breadth of the cell. As the cell enters mitosis, this network breaks down and a highly ordered mitotic spindle is formed. Peripheral microtubule bundles radiate out from each spindle pole and swing out and away from the central spindle during anaphase. Treatment of synchronized cells with 2.5 X 10(-8) M Nocodazole reversibly inhibited nuclear migration concurrent with the disappearance of the extensive cytoplasmic microtubule arrays associated with migrating nuclei. Microtubule arrays and mitotic spindles that reformed after the drug was washed out appeared normal. In contrast, cells treated with 5.0 X 10(-8) M Nocodazole were not able to complete nuclear migration after the drug was washed out and the mitotic spindles that formed were multipolar. Normal and multipolar spindles that were displaced toward one end of the cell by the drug treatment had no effect on the plane of division during cytokinesis. The cleavage furrow always bisected the cell regardless of the position of the mitotic spindle, resulting in binucleate/anucleate daughter cells. This suggests that in S. turris, unlike animal cells, the location of the plane of division is cortically determined before mitosis.

scholarly journals Cytoplasmic dynein is required for normal nuclear segregation in yeast

1993 ◽  
Vol 90 (23) ◽  
pp. 11172-11176 ◽  
Author(s):  
D Eshel ◽  
L A Urrestarazu ◽  
S Vissers ◽  
J C Jauniaux ◽  
J C van Vliet-Reedijk ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Division ◽  
Heavy Chain ◽  
Mitotic Spindle ◽  
Cytoplasmic Dynein ◽  
Predicted Amino Acid Sequence ◽  
Yeast Saccharomyces Cerevisiae ◽  
Abnormal Distribution ◽  
Bud Neck ◽  
Cytoplasmic Microtubules

We have identified the gene DYN1, which encodes the heavy chain of cytoplasmic dynein in the yeast Saccharomyces cerevisiae. The predicted amino acid sequence (M(r) 471,305) reveals the presence of four P-loop motifs, as in all dyneins known so far, and has 28% overall identity to the dynein heavy chain of Dictyostelium [Koonce, M. P., Grissom, P. M. & McIntosh, J. R. (1992) J. Cell Biol. 119, 1597-1604] with 40% identity in the putative motor domain. Disruption of DYN1 causes misalignment of the spindle relative to the bud neck during cell division and results in abnormal distribution of the dividing nuclei between the mother cell and the bud. Cytoplasmic dynein, by generating force along cytoplasmic microtubules, may play an important role in the proper alignment of the mitotic spindle in yeast.

scholarly journals Sensing a bud in the yeast morphogenesis checkpoint: a role for Elm1

2016 ◽  
Vol 27 (11) ◽  
pp. 1764-1775 ◽  
Author(s):  
Hui Kang ◽  
Denis Tsygankov ◽  
Daniel J. Lew
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Nuclear Division ◽  
Environmental Stresses ◽  
Bud Formation ◽  
Septin Ring ◽  
Bud Emergence ◽  
Bud Neck ◽  
Morphogenesis Checkpoint ◽  
Bud Site ◽  
Mitotic Inhibitor

Bud formation by Saccharomyces cerevisiae must be coordinated with the nuclear cycle to enable successful proliferation. Many environmental stresses temporarily disrupt bud formation, and in such circumstances, the morphogenesis checkpoint halts nuclear division until bud formation can resume. Bud emergence is essential for degradation of the mitotic inhibitor, Swe1. Swe1 is localized to the septin cytoskeleton at the bud neck by the Swe1-binding protein Hsl7. Neck localization of Swe1 is required for Swe1 degradation. Although septins form a ring at the presumptive bud site before bud emergence, Hsl7 is not recruited to the septins until after bud emergence, suggesting that septins and/or Hsl7 respond to a “bud sensor.” Here we show that recruitment of Hsl7 to the septin ring depends on a combination of two septin-binding kinases: Hsl1 and Elm1. We elucidate which domains of these kinases are needed and show that artificial targeting of those domains suffices to recruit Hsl7 to septin rings even in unbudded cells. Moreover, recruitment of Elm1 is responsive to bud emergence. Our findings suggest that Elm1 plays a key role in sensing bud emergence.

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