scholarly journals Nuf2, a spindle pole body-associated protein required for nuclear division in yeast.

1994 ◽  
Vol 125 (4) ◽  
pp. 853-866 ◽  
Author(s):  
M A Osborne ◽  
G Schlenstedt ◽  
T Jinks ◽  
P A Silver
Keyword(s):  
Nuclear Division ◽  
Spindle Pole Body ◽  
Coiled Coil ◽  
Temperature Shift ◽  
Spindle Pole ◽  
Temperature Sensitive ◽  
Yeast Saccharomyces Cerevisiae ◽  
Culture Cells ◽  
Pole Body ◽  
Associated Proteins

The NUF2 gene of the yeast Saccharomyces cerevisiae encodes an essential 53-kd protein with a high content of potential coiled-coil structure similar to myosin. Nuf2 is associated with the spindle pole body (SPB) as determined by coimmunofluorescence with known SPB proteins. Nuf2 appears to be localized to the intranuclear region and is a candidate for a protein involved in SPB separation. The nuclear association of Nuf2 can be disrupted, in part, by 1 M salt but not by the detergent Triton X-100. All Nuf2 can be removed from nuclei by 8 M urea extraction. In this regard, Nuf2 is similar to other SPB-associated proteins including Nufl/SPC110, also a coiled-coil protein. Temperature-sensitive alleles of NUF2 were generated within the coiled-coil region of Nuf2 and such NUF2 mutant cells rapidly arrest after temperature shift with a single undivided or partially divided nucleus in the bud neck, a shortened mitotic spindle and their DNA fully replicated. In sum, Nuf2 is a protein associated with the SPB that is critical for nuclear division. Anti-Nuf2 antibodies also recognize a mammalian 73-kd protein and display centrosome staining of mammalian tissue culture cells suggesting the presence of a protein with similar function.

scholarly journals The Cyclin-dependent Kinase Cdc28p Regulates Multiple Aspects of Kar9p Function in Yeast

2007 ◽  
Vol 18 (4) ◽  
pp. 1187-1202 ◽  
Author(s):  
Jeffrey K. Moore ◽  
Rita K. Miller
Keyword(s):  
Spindle Pole Body ◽  
Spindle Pole ◽  
Cyclin Dependent Kinase ◽  
Hybrid Analysis ◽  
Yeast Saccharomyces Cerevisiae ◽  
Microtubule Associated Proteins ◽  
Pole Body ◽  
Associated Proteins ◽  
Cytoplasmic Microtubules ◽  
Two Hybrid

During mitosis in the yeast Saccharomyces cerevisiae, Kar9p directs one spindle pole body (SPB) toward the incipient daughter cell by linking the associated set of cytoplasmic microtubules (cMTs) to the polarized actin network on the bud cortex. The asymmetric localization of Kar9p to one SPB and attached cMTs is dependent on its interactions with microtubule-associated proteins and is regulated by the yeast Cdk1 Cdc28p. Two phosphorylation sites in Kar9p were previously identified. Here, we propose that the two sites are likely to govern Kar9p function through separate mechanisms, each involving a distinct cyclin. In the first mechanism, phosphorylation at serine 496 recruits Kar9p to one SPB. A phosphomimetic mutation at serine 496 bypasses the requirement of BIK1 and CLB5 in generating Kar9p asymmetry. In the second mechanism, Clb4p may target serine 197 of Kar9p for phosphorylation. This modification is required for Kar9p to direct cMTs to the bud. Two-hybrid analysis suggests that this phosphorylation may attenuate the interaction between Kar9p and the XMAP215-homologue Stu2p. We propose that phosphorylation at serine 197 regulates the release of Kar9p from Stu2p at the SPB, either to clear it from the mother-SPB or to allow it to travel to the plus end.

scholarly journals Saccharomyces cerevisiae MPS2Encodes a Membrane Protein Localized at the Spindle Pole Body and the Nuclear Envelope

1999 ◽  
Vol 10 (7) ◽  
pp. 2393-2406 ◽  
Author(s):  
Marı́a de la Cruz Muñoz-Centeno ◽  
Susan McBratney ◽  
Antonio Monterrosa ◽  
Breck Byers ◽  
Carl Mann ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Membrane Protein ◽  
Nuclear Envelope ◽  
Fluorescent Protein ◽  
Spindle Pole Body ◽  
Coiled Coil ◽  
Spindle Pole ◽  
Yeast Saccharomyces Cerevisiae ◽  
Pole Body ◽  
Monopolar Spindle

The MPS2 (monopolar spindle two) gene is one of several genes required for the proper execution of spindle pole body (SPB) duplication in the budding yeast Saccharomyces cerevisiae ( Winey et al., 1991 ). We report here that the MPS2 gene encodes an essential 44-kDa protein with two putative coiled-coil regions and a hydrophobic sequence. Although MPS2 is required for normal mitotic growth, some null strains can survive; these survivors exhibit slow growth and abnormal ploidy. The MPS2 protein was tagged with nine copies of the myc epitope, and biochemical fractionation experiments show that it is an integral membrane protein. Visualization of a green fluorescent protein (GFP) Mps2p fusion protein in living cells and indirect immunofluorescence microscopy of 9xmyc-Mps2p revealed a perinuclear localization with one or two brighter foci of staining corresponding to the SPB. Additionally, immunoelectron microscopy shows that GFP-Mps2p localizes to the SPB. Our analysis suggests that Mps2p is required as a component of the SPB for insertion of the nascent SPB into the nuclear envelope.

scholarly journals Spc42p: a phosphorylated component of the S. cerevisiae spindle pole body (SPD) with an essential function during SPB duplication.

1996 ◽  
Vol 132 (5) ◽  
pp. 887-901 ◽  
Author(s):  
A D Donaldson ◽  
J V Kilmartin
Keyword(s):  
Nuclear Membrane ◽  
Spindle Pole Body ◽  
Coiled Coil ◽  
Spindle Pole ◽  
Normal Function ◽  
Temperature Sensitive ◽  
Pole Body ◽  
Polymeric Layer ◽  
Essential Function ◽  
Mutant Cells

The 42-kD component of the S. cerevisiae spindle pole body (SPB) localizes to the electron-dense central plaque of the SPB. We have cloned the corresponding gene SPC42 (spindle pole component) and show that it is essential. Seven temperature-sensitive (ts) mutants in SPC42 were prepared by error-prone PCR. We found that a change to a proline residue in a potential coiled-coil region of Spc42p was responsible for the ts phenotype in at least three alleles, suggesting that formation of the coiled-coil is essential in normal function. The mutant cells showed a phenotype of predominantly single or bilobed SPBs often with an accumulation of unstructured electron-dense material associated with the bridge structure adjacent to the SPB. This phenotype suggests a defect in SPB duplication. This was confirmed by examining synchronized mutant cells that lose viability when SPB duplication is attempted. Spc42p is a phosphoprotein which shows some cell cycle-regulated phosphorylation. Overexpression of Spc42p causes the formation of a disc- or dome-shaped polymer composed of phosphorylated Spc42p, which is attached to the central plaque and associated with the outer nuclear membrane. Taken together, these data suggest that Spc42p forms a polymeric layer at the periphery of the SPB central plaque which has an essential function during SPB duplication and may facilitate attachment of the SPB to the nuclear membrane.

scholarly journals SPC72: a spindle pole component required for spindle orientation in the yeast Saccharomyces cerevisiae

1998 ◽  
Vol 111 (18) ◽  
pp. 2809-2818 ◽  
Author(s):  
S. Soues ◽  
I.R. Adams
Keyword(s):  
Cell Cycle ◽  
Spindle Pole Body ◽  
Coiled Coil ◽  
Spindle Pole ◽  
Spindle Orientation ◽  
Yeast Saccharomyces Cerevisiae ◽  
Spindle Positioning ◽  
Pole Body ◽  
Per Se ◽  
Pole Component

The monoclonal antibody 78H6 recognises an 85 kDa component of the yeast spindle pole body. Here we identify and characterise this component as Spc72p, the product of YAL047C. The sequence of SPC72 contains potential coiled-coil domains; its overexpression induced formation of large polymers that were strictly localised at the outer plaque and at the bridge of the spindle pole body. Immunoelectron microscopy confirmed that Spc72p was a component of these polymers. SPC72 was found to be non-essential for cell growth, but its deletion resulted in abnormal spindle positioning, aberrant nuclear migration and defective mating capability. Precisely, deletion of SPC72 resulted in a decreased number of astral microtubules: early in the cell cycle only few were detectable, and these were unattached to the spindle pole body in small-budded cells. Later in the cell cycle few, if any, remained, and they were unable to align the spindle properly. We conclude that Spc72p is not absolutely required for nucleation per se, but is needed for normal abundance and stability of astral microtubules.

scholarly journals Sfi1p has conserved centrin-binding sites and an essential function in budding yeast spindle pole body duplication

2003 ◽  
Vol 162 (7) ◽  
pp. 1211-1221 ◽  
Author(s):  
John V. Kilmartin
Keyword(s):  
Single Molecule ◽  
Protein A ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Binding Motif ◽  
Temperature Sensitive ◽  
Pole Body ◽  
Human Proteins ◽  
Z Domain ◽  
Essential Function

Centrins are calmodulin-like proteins present in microtubule-organizing centers. The Saccharomyces cerevisiae centrin, Cdc31p, was functionally tagged with a single Z domain of protein A, and used in pull-down experiments to isolate Cdc31p-binding proteins. One of these, Sfi1p, localizes to the half-bridge of the spindle pole body (SPB), where Cdc31p is also localized. Temperature-sensitive mutants in SFI1 show a defect in SPB duplication and genetic interactions with cdc31-1. Sfi1p contains multiple internal repeats that are also present in a Schizosaccharomyces pombe protein, which also localizes to the SPB, and in several human proteins, one of which localizes close to the centriole region. Cdc31p binds directly to individual Sfi1 repeats in a 1:1 ratio, so a single molecule of Sfi1p binds multiple molecules of Cdc31p. The centrosomal human protein containing Sfi1 repeats also binds centrin in the repeat region, showing that this centrin-binding motif is conserved.

scholarly journals A microtubule polymerase cooperates with the kinesin-6 motor and a microtubule cross-linker to promote bipolar spindle assembly in the absence of kinesin-5 and kinesin-14 in fission yeast

2017 ◽  
Vol 28 (25) ◽  
pp. 3647-3659 ◽  
Author(s):  
Masashi Yukawa ◽  
Tomoki Kawakami ◽  
Masaki Okazaki ◽  
Kazunori Kume ◽  
Ngang Heok Tang ◽  
...  
Keyword(s):  
Fission Yeast ◽  
Chromosome Segregation ◽  
Spindle Pole Body ◽  
Spindle Assembly ◽  
Spindle Pole ◽  
Temperature Sensitive ◽  
Bipolar Spindle ◽  
Pole Body ◽  
Cross Linker ◽  
Spindle Elongation

Accurate chromosome segregation relies on the bipolar mitotic spindle. In many eukaryotes, spindle formation is driven by the plus-end–directed motor kinesin-5 that generates outward force to establish spindle bipolarity. Its inhibition leads to the emergence of monopolar spindles with mitotic arrest. Intriguingly, simultaneous inactivation of the minus-end–directed motor kinesin-14 restores spindle bipolarity in many systems. Here we show that in fission yeast, three independent pathways contribute to spindle bipolarity in the absence of kinesin-5/Cut7 and kinesin-14/Pkl1. One is kinesin-6/Klp9 that engages with spindle elongation once short bipolar spindles assemble. Klp9 also ensures the medial positioning of anaphase spindles to prevent unequal chromosome segregation. Another is the Alp7/TACC-Alp14/TOG microtubule polymerase complex. Temperature-sensitive alp7cut7pkl1 mutants are arrested with either monopolar or very short spindles. Forced targeting of Alp14 to the spindle pole body is sufficient to render alp7cut7pkl1 triply deleted cells viable and promote spindle assembly, indicating that Alp14-mediated microtubule polymerization from the nuclear face of the spindle pole body could generate outward force in place of Cut7 during early mitosis. The third pathway involves the Ase1/PRC1 microtubule cross-linker that stabilizes antiparallel microtubules. Our study, therefore, unveils multifaceted interplay among kinesin-dependent and -independent pathways leading to mitotic bipolar spindle assembly.

scholarly journals Spc98p Directs the Yeast γ-Tubulin Complex into the Nucleus and Is Subject to Cell Cycle-dependent Phosphorylation on the Nuclear Side of the Spindle Pole Body

1998 ◽  
Vol 9 (4) ◽  
pp. 775-793 ◽  
Author(s):  
Gislene Pereira ◽  
Michael Knop ◽  
Elmar Schiebel
Keyword(s):  
Cell Cycle ◽  
Spindle Pole Body ◽  
Mitotic Checkpoint ◽  
Spindle Pole ◽  
Nuclear Localization Sequence ◽  
Checkpoint Control ◽  
Yeast Saccharomyces Cerevisiae ◽  
Pole Body ◽  
Cycle Dependent ◽  
Cytoplasmic Side

In the yeast Saccharomyces cerevisiae, microtubules are organized by the spindle pole body (SPB), which is embedded in the nuclear envelope. Microtubule organization requires the γ-tubulin complex containing the γ-tubulin Tub4p, Spc98p, and Spc97p. The Tub4p complex is associated with cytoplasmic and nuclear substructures of the SPB, which organize the cytoplasmic and nuclear microtubules. Here we present evidence that the Tub4p complex assembles in the cytoplasm and then either binds to the cytoplasmic side of the SPB or is imported into the nucleus followed by binding to the nuclear side of the SPB. Nuclear import of the Tub4p complex is mediated by the essential nuclear localization sequence of Spc98p. Our studies also indicate that Spc98p in the Tub4p complex is phosphorylated at the nuclear, but not at the cytoplasmic, side of the SPB. This phosphorylation is cell cycle dependent and occurs after SPB duplication and nucleation of microtubules by the new SPB and therefore may have a role in mitotic spindle function. In addition, activation of the mitotic checkpoint stimulates Spc98p phosphorylation. The kinase Mps1p, which functions in SPB duplication and mitotic checkpoint control, seems to be involved in Spc98p phosphorylation. Our results also suggest that the nuclear and cytoplasmic Tub4p complexes are regulated differently.

scholarly journals Role of calmodulin and Spc110p interaction in the proper assembly of spindle pole body compenents.

1996 ◽  
Vol 133 (1) ◽  
pp. 111-124 ◽  
Author(s):  
H A Sundberg ◽  
L Goetsch ◽  
B Byers ◽  
T N Davis
Keyword(s):  
Spindle Pole Body ◽  
Spindle Pole ◽  
Immunofluorescent Staining ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
Nonpermissive Temperature ◽  
Carboxy Terminus ◽  
Calmodulin Binding ◽  
Pole Body ◽  
Mutant Cells

Previously we demonstrated that calmodulin binds to the carboxy terminus of Spc110p, an essential component of the Saccharomyces cerevisiae spindle pole body (SPB), and that this interaction is required for chromosome segregation. Immunoelectron microscopy presented here shows that calmodulin and thus the carboxy terminus of Spc110p localize to the central plaque. We created temperature-sensitive SPC110 mutations by combining PCR mutagenesis with a plasmid shuffle strategy. The temperature-sensitive allele spc110-220 differs from wild type at two sites. The cysteine 911 to arginine mutation resides in the calmodulin-binding site and alone confers a temperature-sensitive phenotype. Calmodulin overproduction suppresses the temperature sensitivity of spc110-220. Furthermore, calmodulin levels at the SPB decrease in the mutant cells at the restrictive temperature. Thus, calmodulin binding to Spc110-220p is defective at the nonpermissive temperature. Synchronized mutant cells incubated at the nonpermissive temperature arrest as large budded cells with a G2 content of DNA and suffer considerable lethality. Immunofluorescent staining demonstrates failure of nuclear DNA segregation and breakage of many spindles. Electron microscopy reveals an aberrant nuclear structure, the intranuclear microtubule organizer (IMO), that differs from a SPB but serves as a center of microtubule organization. The IMO appears during nascent SPB formation and disappears after SPB separation. The IMO contains both the 90-kD and the mutant 110-kD SPB components. Our results suggest that disruption of the calmodulin Spc110p interaction leads to the aberrant assembly of SPB components into the IMO, which in turn perturbs spindle formation.

scholarly journals Vesicle Docking to the Spindle Pole Body Is Necessary to Recruit the Exocyst During Membrane Formation inSaccharomyces cerevisiae

2010 ◽  
Vol 21 (21) ◽  
pp. 3693-3707 ◽  
Author(s):  
Erin M. Mathieson ◽  
Yasuyuki Suda ◽  
Mark Nickas ◽  
Brian Snydsman ◽  
Trisha N. Davis ◽  
...  
Keyword(s):  
De Novo ◽  
Spindle Pole Body ◽  
Coiled Coil ◽  
Resonance Energy ◽  
Initiation Site ◽  
Spindle Pole ◽  
Rab Gtpase ◽  
Membrane Formation ◽  
Vesicle Docking ◽  
Pole Body

During meiosis II in Saccharomyces cerevisiae, the cytoplasmic face of the spindle pole body, referred to as the meiosis II outer plaque (MOP), is modified in both composition and structure to become the initiation site for de novo formation of a membrane called the prospore membrane. The MOP serves as a docking complex for precursor vesicles that are targeted to its surface. Using fluorescence resonance energy transfer analysis, the orientation of coiled-coil proteins within the MOP has been determined. The N-termini of two proteins, Mpc54p and Spo21p, were oriented toward the outer surface of the structure. Mutations in the N-terminus of Mpc54p resulted in a unique phenotype: precursor vesicles loosely tethered to the MOP but did not contact its surface. Thus, these mpc54 mutants separate the steps of vesicle association and docking. Using these mpc54 mutants, we determined that recruitment of the Rab GTPase Sec4p, as well as the exocyst components Sec3p and Sec8p, to the precursor vesicles requires vesicle docking to the MOP. This suggests that the MOP promotes membrane formation both by localization of precursor vesicles to a particular site and by recruitment of a second tethering complex, the exocyst, that stimulates downstream events of fusion.

Somatic nuclear division in the sporidia of Ustilago violacea. II. Observations on living cells with phase-contrast and fluorescence microscopy

1974 ◽  
Vol 20 (5) ◽  
pp. 739-746 ◽  
Author(s):  
N. H. Poon ◽  
A. W. Day
Keyword(s):  
Fluorescence Microscopy ◽  
Acridine Orange ◽  
Phase Contrast ◽  
Nuclear Division ◽  
Spindle Pole Body ◽  
Time Lapse ◽  
Spindle Pole ◽  
Living Cells ◽  
Pole Body ◽  
Orange Fluorescence

Somatic nuclear division in living cells is described under both phase-contrast and acridine orange fluorescence microscopy. The observations confirm a previous description of the division in fixed cells stained with acetic orcein. Acridine orange at the optimum concentration of 75–250 mg/liter complete medium clearly differentiated the nucleolus, chromatinic granules, nucleoplasm, and spindle pole body, as well as indicating changes in RNA content in the cytoplasm during budding. Acridine orange fluorescence was identical in both living and fixed cells. The fluorescence of the spindle pole body indicated that it contains DNA, which may initiate RNA synthesis. Time-lapse phase-contrast observations confirmed that neither the fixation technique nor acridine orange or acetic orcein staining caused noticeable artefacts during division, and provided indisputable evidence for the sequencing of stages. Estimates from the time-lapse observations indicated that the division is quite slow (about 45 min) and that 'prophase' takes about 12 min, 'metaphase' 5 min, and 'anaphase–telophase' about 28 min.

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