scholarly journals The Yeast CDC37 Gene Interacts with MPS1 and Is Required for Proper Execution of Spindle Pole Body Duplication

1997 ◽  
Vol 136 (5) ◽  
pp. 969-982 ◽  
Author(s):  
Amy R. Schutz ◽  
Thomas H. Giddings ◽  
Estelle Steiner ◽  
Mark Winey
Keyword(s):  
Spindle Assembly Checkpoint ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Temperature Sensitive ◽  
G1 Arrest ◽  
Multicopy Suppressor ◽  
Protein Levels ◽  
Pole Body ◽  
Synthetic Lethal Interactions ◽  
Sensitive Allele

The MPS1 gene from Saccharomyces cerevisiae encodes an essential protein kinase required for spindle pole body (SPB) duplication and for the mitotic spindle assembly checkpoint. Cells with the mps1-1 mutation fail early in SPB duplication and proceed through monopolar mitosis with lethal consequences. We identified CDC37 as a multicopy suppressor of mps1-1 temperature-sensitive growth. Suppression is allele specific, and synthetic lethal interactions occur between mps1 and cdc37 alleles. We examined the cdc37-1 phenotype for defects related to the SPB cycle. The cdc37-1 temperature-sensitive allele causes unbudded, G1 arrest at Start (Reed, S.I. 1980. Genetics. 95: 561–577). Reciprocal shifts demonstrate that cdc37-1 arrest is interdependent with α-factor arrest but is not a normal Start arrest. Although the cells are responsive to α-factor at the arrest, SPB duplication is uncoupled from other aspects of G1 progression and proceeds past the satellite-bearing SPB stage normally seen at Start. Electron microscopy reveals side-by-side SPBs at cdc37-1 arrest. The outer plaque of one SPB is missing or reduced, while the other is normal. Using the mps2-1 mutation to distinguish between the SPBs, we find that the outer plaque defect is specific to the new SPB. This phenotype may arise in part from reduced Mps1p function: although Mps1p protein levels are unaffected by the cdc37-1 mutation, kinase activity is markedly reduced. These data demonstrate a requirement for CDC37 in SPB duplication and suggest a role for this gene in G1 control. CDC37 may provide a chaperone function that promotes the activity of protein kinases.

scholarly journals New Alleles of the YeastMPS1Gene Reveal Multiple Requirements in Spindle Pole Body Duplication

1998 ◽  
Vol 9 (4) ◽  
pp. 759-774 ◽  
Author(s):  
Amy R. Schutz ◽  
Mark Winey
Keyword(s):  
Protein Kinase ◽  
Spindle Assembly Checkpoint ◽  
Single Point ◽  
Spindle Pole Body ◽  
Spindle Assembly ◽  
Spindle Pole ◽  
Single Point Mutation ◽  
Temperature Sensitive ◽  
Pole Body

In Saccharomyces cerevisiae, the Mps1p protein kinase is critical for both spindle pole body (SPB) duplication and the mitotic spindle assembly checkpoint. The mps1–1mutation causes failure early in SPB duplication, and because the spindle assembly checkpoint is also compromised, mps1–1cells proceed with a monopolar mitosis and rapidly lose viability. Here we report the genetic and molecular characterization ofmps1–1 and five new temperature-sensitive alleles ofMPS1. Each of the six alleles contains a single point mutation in the region of the gene encoding the protein kinase domain. The mutations affect several residues conserved among protein kinases, most notably the invariant glutamate in subdomain III. In vivo and in vitro kinase activity of the six epitope-tagged mutant proteins varies widely. Only two display appreciable in vitro activity, and interestingly, this activity is not thermolabile under the assay conditions used. While five of the six alleles cause SPB duplication to fail early, yielding cells with a single SPB, mps1–737cells proceed into SPB duplication and assemble a second SPB that is structurally defective. This phenotype, together with the observation of intragenic complementation between this unique allele and two others, suggests that Mps1p is required for multiple events in SPB duplication.

scholarly journals TheSaccharomyces cerevisiaeSpindle Pole Body (SPB) Component Nbp1p Is Required for SPB Membrane Insertion and Interacts with the Integral Membrane Proteins Ndc1p and Mps2p

2006 ◽  
Vol 17 (4) ◽  
pp. 1959-1970 ◽  
Author(s):  
Yasuhiro Araki ◽  
Corine K. Lau ◽  
Hiromi Maekawa ◽  
Sue L. Jaspersen ◽  
Thomas H. Giddings ◽  
...  
Keyword(s):  
Nuclear Envelope ◽  
Spindle Pole Body ◽  
Integral Membrane Protein ◽  
Spindle Pole ◽  
Membrane Insertion ◽  
Temperature Sensitive ◽  
Pole Body ◽  
Spindle Microtubules ◽  
Sensitive Allele ◽  
Two Hybrid

The spindle pole body (SPB) in Saccharomyces cerevisiae functions to nucleate and organize spindle microtubules, and it is embedded in the nuclear envelope throughout the yeast life cycle. However, the mechanism of membrane insertion of the SPB has not been elucidated. Ndc1p is an integral membrane protein that localizes to SPBs, and it is required for insertion of the SPB into the nuclear envelope during SPB duplication. To better understand the function of Ndc1p, we performed a dosage suppressor screen using the ndc1-39 temperature-sensitive allele. We identified an essential SPB component, Nbp1p. NBP1 shows genetic interactions with several SPB genes in addition to NDC1, and two-hybrid analysis revealed that Nbp1p binds to Ndc1p. Furthermore, Nbp1p is in the Mps2p-Bbp1p complex in the SPB. Immunoelectron microscopy confirmed that Nbp1p localizes to the SPB, suggesting a function at this location. Consistent with this hypothesis, nbp1-td (a degron allele) cells fail in SPB duplication upon depletion of Nbp1p. Importantly, these cells exhibit a “dead” SPB phenotype, similar to cells mutant in MPS2, NDC1, or BBP1. These results demonstrate that Nbp1p is a SPB component that acts in SPB duplication at the point of SPB insertion into the nuclear envelope.

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 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 Spindle Pole Body Duplication in Fission Yeast Occurs at the G1/S Boundary but Maturation Is Blocked until Exit from S by an Event Downstream of Cdc10+

2004 ◽  
Vol 15 (12) ◽  
pp. 5219-5230 ◽  
Author(s):  
Satoru Uzawa ◽  
Fei Li ◽  
Ye Jin ◽  
Kent L. McDonald ◽  
Michael B. Braunfeld ◽  
...  
Keyword(s):  
Fission Yeast ◽  
Spindle Pole Body ◽  
Specific Inhibitor ◽  
Spindle Pole ◽  
Feedback Mechanism ◽  
G1 Arrest ◽  
Restrictive Temperature ◽  
Permissive Temperature ◽  
Pole Body ◽  
In Cells

The regulation and timing of spindle pole body (SPB) duplication and maturation in fission yeast was examined by transmission electron microscopy. When cells are arrested at G1 by nitrogen starvation, the SPB is unduplicated. On release from G1, the SPBs were duplicated after 1–2 h. In cells arrested at S by hydroxyurea, SPBs are duplicated but not mature. In G1 arrest/release experiments with cdc2.33 cells at the restrictive temperature, SPBs remained single, whereas in cells at the permissive temperature, SPBs were duplicated. In cdc10 mutant cells, the SPBs seem not only to be duplicated but also to undergo partial maturation, including invagination of the nuclear envelope underneath the SPB. There may be an S-phase–specific inhibitor of SPB maturation whose expression is under control of cdc10+. This model was examined by induction of overreplication of the genome by overexpression of rum1p or cdc18p. In cdc18p-overexpressing cells, the SPBs are duplicated but not mature, suggesting that cdc18p is one component of this feedback mechanism. In contrast, cells overexpressing rum1p have large, deformed SPBs accompanied by other features of maturation and duplication. We propose a feedback mechanism for maturation of the SPB that is coupled with exit from S to trigger morphological changes.

scholarly journals A Fourth Component of the Fission Yeast γ-Tubulin Complex, Alp16, Is Required for Cytoplasmic Microtubule Integrity and Becomes Indispensable When γ-Tubulin Function Is Compromised

2002 ◽  
Vol 13 (7) ◽  
pp. 2360-2373 ◽  
Author(s):  
Akiko Fujita ◽  
Leah Vardy ◽  
Miguel Angel Garcia ◽  
Takashi Toda
Keyword(s):  
Fission Yeast ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Temperature Sensitive ◽  
Microtubule Organizing Center ◽  
Cytoplasmic Microtubule ◽  
Multicopy Suppressor ◽  
Large Complex ◽  
Synthetically Lethal ◽  
And Function

γ-Tubulin functions as a multiprotein complex, called the γ-tubulin complex (γ-TuC), and composes the microtubule organizing center (MTOC). Fission yeast Alp4 and Alp6 are homologues of two conserved γ-TuC proteins, hGCP2 and hGCP3, respectively. We isolated a novel gene, alp16 + , as a multicopy suppressor of temperature-sensitive alp6-719mutants. alp16 + encodes a 759-amino-acid protein with two conserved regions found in all other members of γ-TuC components. In addition, Alp16 contains an additional motif, which shows homology to hGCP6/Xgrip210. Gene disruption shows that alp16 + is not essential for cell viability. However, alp16 deletion displays abnormally long cytoplasmic microtubules, which curve around the cell tip. Furthermore, alp16-deleted mutants are hypersensitive to microtubule-depolymerizing drugs and synthetically lethal with either temperature-sensitive alp4-225,alp4-1891, or alp6-719 mutants. Overproduction of Alp16 is lethal, with defective phenotypes very similar to loss of Alp4 or Alp6. Alp16 localizes to the spindle pole body throughout the cell cycle and to the equatorial MTOC at postanaphase. Alp16 coimmunoprecipitates with γ-tubulin and cosediments with the γ-TuC in a large complex (>20 S). Alp16 is, however, not required for the formation of this large complex. We discuss evolutional conservation and divergence of structure and function of the γ-TuC between yeast and higher eukaryotes.

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 Localization of Core Spindle Pole Body (SPB) Components during SPB Duplication in Saccharomyces cerevisiae

1999 ◽  
Vol 145 (4) ◽  
pp. 809-823 ◽  
Author(s):  
Ian R. Adams ◽  
John V. Kilmartin
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Temperature Sensitive ◽  
Large Plaque ◽  
Temperature Sensitive Mutants ◽  
Pole Body ◽  
Cytoplasmic Face ◽  
Preceding Cell

We have examined the process of spindle pole body (SPB) duplication in Saccharomyces cerevisiae by electron microscopy and found several stages. These include the assembly, probably from the satellite, of a large plaque-like structure, the duplication plaque, on the cytoplasmic face of the half-bridge and its insertion into the nuclear envelope. We analyzed the role of the main SPB components in the formation of these structures by identifying them from an SPB core fraction by mass spectrometry. Temperature-sensitive mutants for two of the components, Spc29p and Nud1p, were prepared to partly define their function. The composition of two of the intermediates in SPB duplication, the satellite and the duplication plaque, was examined by immunoelectron microscopy. Both contain cytoplasmic SPB components showing that duplication has already been partly achieved by the end of the preceding cell cycle when the satellite is formed. We show that by overexpression of SPB components the structure of the satellite can be changed and SPB duplication inhibited by disrupting the attachment of the plaque-like intermediate to the half-bridge. We present a model for SPB duplication where binding of SPB components to either end of the bridge structure ensures two separate SPBs.

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