Faculty Opinions recommendation of Spindle orientation in Saccharomyces cerevisiae depends on the transport of microtubule ends along polarized actin cables.

2003 ◽  
Author(s):  
Mark Rose
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Spindle Orientation ◽  
Actin Cables

scholarly journals The Role of Actin in Spindle Orientation Changes during the Saccharomyces cerevisiae Cell Cycle

1999 ◽  
Vol 146 (5) ◽  
pp. 1019-1032 ◽  
Author(s):  
Chandra L. Theesfeld ◽  
Javier E. Irazoqui ◽  
Kerry Bloom ◽  
Daniel J. Lew
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Spindle Orientation ◽  
Cortical Actin ◽  
Yeast Saccharomyces Cerevisiae ◽  
Daughter Cells ◽  
M Phase ◽  
Actin Cables

In the budding yeast Saccharomyces cerevisiae, the mitotic spindle must align along the mother-bud axis to accurately partition the sister chromatids into daughter cells. Previous studies showed that spindle orientation required both astral microtubules and the actin cytoskeleton. We now report that maintenance of correct spindle orientation does not depend on F-actin during G2/M phase of the cell cycle. Depolymerization of F-actin using Latrunculin-A did not perturb spindle orientation after this stage. Even an early step in spindle orientation, the migration of the spindle pole body (SPB), became actin-independent if it was delayed until late in the cell cycle. Early in the cell cycle, both SPB migration and spindle orientation were very sensitive to perturbation of F-actin. Selective disruption of actin cables using a conditional tropomyosin double-mutant also led to de- fects in spindle orientation, even though cortical actin patches were still polarized. This suggests that actin cables are important for either guiding astral microtubules into the bud or anchoring them in the bud. In addition, F-actin was required early in the cell cycle for the development of the actin-independent spindle orientation capability later in the cell cycle. Finally, neither SPB migration nor the switch from actin-dependent to actin-independent spindle behavior required B-type cyclins.

scholarly journals Differential contribution of Bud6p and Kar9p to microtubule capture and spindle orientation in S. cerevisiae

2004 ◽  
Vol 167 (2) ◽  
pp. 231-244 ◽  
Author(s):  
Stephen M. Huisman ◽  
Olivia A.M. Bales ◽  
Marie Bertrand ◽  
Monique F.M.A. Smeets ◽  
Steven I. Reed ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mother Cell ◽  
Spindle Orientation ◽  
Cell Cortex ◽  
Dependent Manner ◽  
Spindle Positioning ◽  
Microscopy Analysis ◽  
Temporal And Spatial ◽  
Actin Cables ◽  
Differential Contribution

In Saccharomyces cerevisiae, spindle orientation is controlled by a temporal and spatial program of microtubule (MT)–cortex interactions. This program requires Bud6p/Aip3p to direct the old pole to the bud and confine the new pole to the mother cell. Bud6p function has been linked to Kar9p, a protein guiding MTs along actin cables. Here, we show that Kar9p does not mediate Bud6p functions in spindle orientation. Based on live microscopy analysis, kar9Δ cells maintained Bud6p-dependent MT capture. Conversely, bud6Δ cells supported Kar9p-associated MT delivery to the bud. Moreover, additive phenotypes in bud6Δ kar9Δ or bud6Δ dyn1Δ mutants underscored the separate contributions of Bud6p, Kar9p, and dynein to spindle positioning. Finally, tub2C354S, a mutation decreasing MT dynamics, suppressed a kar9Δ mutation in a BUD6-dependent manner. Thus, Kar9p-independent capture at Bud6p sites can effect spindle orientation provided MT turnover is reduced. Together, these results demonstrate Bud6p function in MT capture at the cell cortex, independent of Kar9p-mediated MT delivery along actin cables.

scholarly journals Spindle orientation in Saccharomyces cerevisiae depends on the transport of microtubule ends along polarized actin cables

2003 ◽  
Vol 161 (3) ◽  
pp. 483-488 ◽  
Author(s):  
Eric Hwang ◽  
Justine Kusch ◽  
Yves Barral ◽  
Tim C. Huffaker
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Actin Filaments ◽  
Yeast Cells ◽  
Similar Process ◽  
Spindle Orientation ◽  
Yeast Saccharomyces Cerevisiae ◽  
Cytoplasmic Microtubules ◽  
Actin Cables ◽  
Type V

Microtubules and actin filaments interact and cooperate in many processes in eukaryotic cells, but the functional implications of such interactions are not well understood. In the yeast Saccharomyces cerevisiae, both cytoplasmic microtubules and actin filaments are needed for spindle orientation. In addition, this process requires the type V myosin protein Myo2, the microtubule end–binding protein Bim1, and Kar9. Here, we show that fusing Bim1 to the tail of the Myo2 is sufficient to orient spindles in the absence of Kar9, suggesting that the role of Kar9 is to link Myo2 to Bim1. In addition, we show that Myo2 localizes to the plus ends of cytoplasmic microtubules, and that the rate of movement of these cytoplasmic microtubules to the bud neck depends on the intrinsic velocity of Myo2 along actin filaments. These results support a model for spindle orientation in which a Myo2–Kar9–Bim1 complex transports microtubule ends along polarized actin cables. We also present data suggesting that a similar process plays a role in orienting cytoplasmic microtubules in mating yeast cells.

scholarly journals The Saccharomyces cerevisiae MYO2 gene encodes an essential myosin for vectorial transport of vesicles.

1991 ◽  
Vol 113 (3) ◽  
pp. 539-551 ◽  
Author(s):  
G C Johnston ◽  
J A Prendergast ◽  
R A Singer
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Molecular Motor ◽  
Actin Binding ◽  
Restrictive Temperature ◽  
Secretory Vesicles ◽  
Biosynthetic Activity ◽  
Yeast Saccharomyces Cerevisiae ◽  
Terminal Domain ◽  
Essential Form ◽  
Actin Cables

After the initiation of bud formation, cells of the yeast Saccharomyces cerevisiae direct new growth to the developing bud. We show here that this vectorial growth is facilitated by activity of the MYO2 gene. The wild-type MYO2 gene encodes an essential form of myosin composed of an NH2-terminal domain typical of the globular, actin-binding domain of other myosins. This NH2-terminal domain is linked by what appears to be a short alpha-helical domain to a novel COOH-terminal region. At the restrictive temperature the myo2-66 mutation does not impair DNA, RNA, or protein biosynthetic activity, but produces unbudded, enlarged cells. This phenotype suggests a defect in localization of cell growth. Measurements of cell size demonstrated that the continued development of initiated buds, as well as bud initiation itself, is inhibited. Bulk secretion continues in mutant cells, although secretory vesicles accumulate. The MYO2 myosin thus may function as the molecular motor to transport secretory vesicles along actin cables to the site of bud development.

scholarly journals Dynamic localization of yeast Fus2p to an expanding ring at the cell fusion junction during mating

2008 ◽  
Vol 181 (4) ◽  
pp. 697-709 ◽  
Author(s):  
Joanna Mathis Paterson ◽  
Casey A. Ydenberg ◽  
Mark D. Rose
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Fusion ◽  
Fluorescent Protein ◽  
Cell Junction ◽  
Dynamic Localization ◽  
Actin Organization ◽  
Pheromone Signaling ◽  
Fusion Junction ◽  
Green Fluorescent ◽  
Actin Cables

Fus2p is a pheromone-induced protein associated with the amphiphysin homologue Rvs161p, which is required for cell fusion during mating in Saccharomyces cerevisiae. We constructed a functional Fus2p–green fluorescent protein (GFP), which exhibits highly dynamic localization patterns in pheromone-responding cells (shmoos): diffuse nuclear, mobile cytoplasmic dots and stable cortical patches concentrated at the shmoo tip. In mitotic cells, Fus2p-GFP is nuclear but becomes cytoplasmic as cells form shmoos, dependent on the Fus3p protein kinase and high levels of pheromone signaling. The rapid cytoplasmic movement of Fus2p-GFP dots requires Rvs161p and polymerized actin and is aberrant in mutants with compromised actin organization, which suggests that the Fus2p dots are transported along actin cables, possibly in association with vesicles. Maintenance of Fus2p-GFP patches at the shmoo tip cortex is jointly dependent on actin and a membrane protein, Fus1p, which suggests that Fus1p is an anchor for Fus2p. In zygotes, Fus2p-GFP forms a dilating ring at the cell junction, returning to the nucleus at the completion of cell fusion.

scholarly journals The Stationary-Phase Cells of Saccharomyces cerevisiae Display Dynamic Actin Filaments Required for Processes Extending Chronological Life Span

2015 ◽  
Vol 35 (22) ◽  
pp. 3892-3908 ◽  
Author(s):  
Pavla Vasicova ◽  
Renata Lejskova ◽  
Ivana Malcova ◽  
Jiri Hasek
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Stationary Phase ◽  
Actin Filaments ◽  
Phase Cell ◽  
Content Type ◽  
Chronological Aging ◽  
Yeast Cultures ◽  
Actin Cables ◽  
Mitochondrial Networks

Stationary-growth-phaseSaccharomyces cerevisiaeyeast cultures consist of nondividing cells that undergo chronological aging. For their successful survival, the turnover of proteins and organelles, ensured by autophagy and the activation of mitochondria, is performed. Some of these processes are engaged in by the actin cytoskeleton. InS. cerevisiaestationary-phase cells, F actin has been shown to form static aggregates named actin bodies, subsequently cited to be markers of quiescence. Ourin vivoanalyses revealed that stationary-phase cultures contain cells with dynamic actin filaments, besides the cells with static actin bodies. The cells with dynamic actin displayed active endocytosis and autophagy and well-developed mitochondrial networks. Even more, stationary-phase cell cultures grown under calorie restriction predominantly contained cells with actin cables, confirming that the presence of actin cables is linked to successful adaptation to stationary phase. Cells with actin bodies were inactive in endocytosis and autophagy and displayed aberrations in mitochondrial networks. Notably, cells of the respiratory activity-deficientcox4Δ strain displayed the same mitochondrial aberrations and actin bodies only. Additionally, our results indicate that mitochondrial dysfunction precedes the formation of actin bodies and the appearance of actin bodies corresponds to decreased cell fitness. We conclude that the F-actin status reflects the extent of damage that arises from exponential growth.

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 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 Yeast formin Bni1p has multiple localization regions that function in polarized growth and spindle orientation

2012 ◽  
Vol 23 (3) ◽  
pp. 412-422 ◽  
Author(s):  
Wenyu Liu ◽  
Felipe H. Santiago-Tirado ◽  
Anthony Bretscher
Keyword(s):  
Coiled Coil ◽  
Binding Domain ◽  
Dominant Negative ◽  
Dominant Negative Effect ◽  
Spindle Orientation ◽  
Bud Neck ◽  
Negative Effect ◽  
The Right ◽  
Actin Cables ◽  
And Function

Formins are conserved proteins that assemble unbranched actin filaments in a regulated, localized manner. Budding yeast's two formins, Bni1p and Bnr1p, assemble actin cables necessary for polarized cell growth and organelle segregation. Here we define four regions in Bni1p that contribute to its localization to the bud and at the bud neck. The first (residues 1–333) requires dimerization for its localization and encompasses the Rho-binding domain. The second (residues 334–821) covers the Diaphanous inhibitory–dimerization–coiled coil domains, and the third is the Spa2p-binding domain. The fourth region encompasses the formin homology 1–formin homology 2–COOH region of the protein. These four regions can each localize to the bud cortex and bud neck at the right stage of the cell cycle independent of both F-actin and endogenous Bni1p. The first three regions contribute cumulatively to the proper localization of Bni1p, as revealed by the effects of progressive loss of these regions on the actin cytoskeleton and fidelity of spindle orientation. The fourth region contributes to the localization of Bni1p in tiny budded cells. Expression of mislocalized Bni1p constructs has a dominant-negative effect on both growth and nuclear segregation due to mislocalized actin assembly. These results define an unexpected complexity in the mechanism of formin localization and function.

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