scholarly journals Dissociation of the Nuf2-Ndc80 Complex Releases Centromeres from the Spindle-Pole Body during Meiotic Prophase in Fission Yeast

2005 ◽  
Vol 16 (5) ◽  
pp. 2325-2338 ◽  
Author(s):  
Haruhiko Asakawa ◽  
Aki Hayashi ◽  
Tokuko Haraguchi ◽  
Yasushi Hiraoka
Keyword(s):  
Fission Yeast ◽  
Chromosome Segregation ◽  
Meiotic Prophase ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Mating Pheromone ◽  
Pole Body ◽  
Pheromone Signaling ◽  
Ndc80 Complex ◽  
Mutant Cells

In the fission yeast Schizosaccharomyces pombe, centromeres remain clustered at the spindle-pole body (SPB) during mitotic interphase. In contrast, during meiotic prophase centromeres dissociate from the SPB. Here we examined the behavior of centromere proteins in living meiotic cells of S. pombe. We show that the Nuf2-Ndc80 complex proteins (Nuf2, Ndc80, Spc24, and Spc25) disappear from the centromere in meiotic prophase when the centromeres are separated from the SPB. The centromere protein Mis12 also dissociates during meiotic prophase; however, Mis6 remains throughout meiosis. When cells are induced to meiosis by inactivation of Pat1 kinase (a key negative regulator of meiosis), centromeres remain associated with the SPB during meiotic prophase. However, inactivation of Nuf2 by a mutation causes the release of centromeres from the SPB in pat1 mutant cells, suggesting that the Nuf2-Ndc80 complex connects centromeres to the SPB. We further found that removal of the Nuf2-Ndc80 complex from the centromere and centromere-SPB dissociation are caused by mating pheromone signaling. Because pat1 mutant cells also show aberrant chromosome segregation in the first meiotic division and this aberration is compensated by mating pheromone signaling, dissociation of the Nuf2-Ndc80 complex may be associated with remodeling of the kinetochore for meiotic chromosome segregation.

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 Inactivation of Mitotic Kinase Triggers Translocation of MEN Components to Mother-Daughter Neck in Yeast

2003 ◽  
Vol 14 (11) ◽  
pp. 4734-4743 ◽  
Author(s):  
Hong Hwa Lim ◽  
Foong May Yeong ◽  
Uttam Surana
Keyword(s):  
Chromosome Segregation ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Mitotic Exit ◽  
Mitotic Kinase ◽  
Division Site ◽  
Pole Body ◽  
Spindle Pole Bodies ◽  
Mitotic Exit Network ◽  
Mutant Cells

Chromosome segregation, mitotic exit, and cytokinesis are executed in this order during mitosis. Although a scheme coordinating sister chromatid separation and initiation of mitotic exit has been proposed, the mechanism that temporally links the onset of cytokinesis to mitotic exit is not known. Exit from mitosis is regulated by the mitotic exit network (MEN), which includes a GTPase (Tem1) and various kinases (Cdc15, Cdc5, Dbf2, and Dbf20). Here, we show that Dbf2 and Dbf20 functions are necessary for the execution of cytokinesis. Relocalization of these proteins from spindle pole bodies to mother daughter neck seems to be necessary for this role because cdc15-2 mutant cells, though capable of exiting mitosis at semipermissive temperature, are unable to localize Dbf2 (and Dbf20) to the “neck” and fail to undergo cytokinesis. These cells can assemble and constrict the actomyosin ring normally but are incapable of forming a septum, suggesting that MEN components are critical for the initiation of septum formation. Interestingly, the spindle pole body to neck translocation of Dbf2 and Dbf20 is triggered by the inactivation of mitotic kinase. The requirement of kinase inactivation for translocation of MEN components to the division site thus provides a mechanism that renders mitotic exit a prerequisite for cytokinesis.

scholarly journals Spindle pole body components are reorganized during fission yeast meiosis

2012 ◽  
Vol 23 (10) ◽  
pp. 1799-1811 ◽  
Author(s):  
Midori Ohta ◽  
Masamitsu Sato ◽  
Masayuki Yamamoto
Keyword(s):  
Fission Yeast ◽  
Meiotic Prophase ◽  
Spindle Pole Body ◽  
Mitotic Cell ◽  
Spindle Pole ◽  
Nuclear Movement ◽  
Pole Body ◽  
Proper Number ◽  
Body Components ◽  
Yeast Meiosis

During meiosis, the centrosome/spindle pole body (SPB) must be regulated in a manner distinct from that of mitosis to achieve a specialized cell division that will produce gametes. In this paper, we demonstrate that several SPB components are localized to SPBs in a meiosis-specific manner in the fission yeast Schizosaccharomyces pombe. SPB components, such as Cut12, Pcp1, and Spo15, which stay on the SPB during the mitotic cell cycle, disassociate from the SPB during meiotic prophase and then return to the SPB immediately before the onset of meiosis I. Interestingly, the polo kinase Plo1, which normally localizes to the SPB during mitosis, is excluded from them in meiotic prophase, when meiosis-specific, horse-tail nuclear movement occurs. We found that exclusion of Plo1 during this period was essential to properly remodel SPBs, because artificial targeting of Plo1 to SPBs resulted in an overduplication of SPBs. We also found that the centrin Cdc31 was required for meiotic SPB remodeling. Thus Plo1 and a centrin play central roles in the meiotic SPB remodeling, which is essential for generating the proper number of meiotic SPBs and, thereby provide unique characteristics to meiotic divisions.

scholarly journals Membrane proteins Bqt3 and -4 anchor telomeres to the nuclear envelope to ensure chromosomal bouquet formation

2009 ◽  
Vol 187 (3) ◽  
pp. 413-427 ◽  
Author(s):  
Yuji Chikashige ◽  
Miho Yamane ◽  
Kasumi Okamasa ◽  
Chihiro Tsutsumi ◽  
Tomoko Kojidani ◽  
...  
Keyword(s):  
Nuclear Envelope ◽  
Fission Yeast ◽  
Nuclear Membrane ◽  
Meiotic Prophase ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Null Mutant ◽  
Vegetative Cells ◽  
Nuclear Membranes ◽  
Pole Body

In many organisms, telomeres cluster to form a bouquet arrangement of chromosomes during meiotic prophase. Previously, we reported that two meiotic proteins, Bqt1 and -2, are required for tethering telomeres to the spindle pole body (SPB) during meiotic prophase in fission yeast. This study has further identified two novel, ubiquitously expressed inner nuclear membrane (INM) proteins, Bqt3 and -4, which are required for bouquet formation. We found that in the absence of Bqt4, telomeres failed to associate with the nuclear membranes in vegetative cells and consequently failed to cluster to the SPB in meiotic prophase. In the absence of Bqt3, Bqt4 protein was degraded during meiosis, leading to a phenotype similar to that of the bqt4-null mutant. Collectively, these results show that Bqt4 anchors telomeres to the INM and that Bqt3 protects Bqt4 from protein degradation. Interestingly, the functional integrity of telomeres is maintained even when they are separated from the nuclear envelope in vegetative cells.

Calmodulin localizes to the spindle pole body of Schizosaccharomyces pombe and performs an essential function in chromosome segregation

1997 ◽  
Vol 110 (15) ◽  
pp. 1805-1812 ◽  
Author(s):  
M.J. Moser ◽  
M.R. Flory ◽  
T.N. Davis
Keyword(s):  
Cell Growth ◽  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Chromosome Segregation ◽  
Fluorescent Protein ◽  
Budding Yeast ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Temperature Sensitive ◽  
Pole Body

The essential calmodulin genes in both Saccharomyces cerevisiae and Schizosaccharomyces pombe were precisely replaced with genes encoding fusions between calmodulin and the green fluorescent protein (GFP). In living budding yeast the GFP-calmodulin fusion protein (GFP-Cmd1p) localized simultaneously to sites of cell growth and to the spindle pole body (SPB), the yeast analog of the centrosome. Having demonstrated proper localization of GFP-calmodulin in budding yeast, we examined the localization of a fusion between GFP and calmodulin (GFP-Camlp) in fission yeast, where calmodulin had not been localized by any method. We find GFP-Camlp also localizes both to sites of polarized cell growth and to the fission yeast SPB. The localization of calmodulin to the SPB by GFP fusion was confirmed by indirect immunofluorescence. Antiserum to S. pombe calmodulin labeled the ends of the mitotic spindle stained with anti-tubulin antiserum. This pattern was identical to that seen using antiserum to Sad1p, a known SPB component. We then characterized the defects in a temperature-sensitive S. pombe calmodulin mutant. Mutant cam1-E14 cells synchronized in S phase completed DNA synthesis, but lost viability during transit of mitosis. Severe defects in chromosome segregation, including hypercondensation, fragmentation, and unequal allocation of chromosomal material were observed. Immunofluorescence analysis of tubulin revealed a population of cells containing either broken or mislocalized mitotic spindles, which were never observed in wild-type cells. Taken together with the subcellular localization of calmodulin, the observed spindle and chromosome segregation defects suggest that calmodulin performs an essential role during mitosis at the fission yeast SPB.

scholarly journals Bqt2p is essential for initiating telomere clustering upon pheromone sensing in fission yeast

2006 ◽  
Vol 173 (6) ◽  
pp. 845-851 ◽  
Author(s):  
Xie Tang ◽  
Ye Jin ◽  
W. Zacheus Cande
Keyword(s):  
Fission Yeast ◽  
Chromosome Pairing ◽  
Meiotic Prophase ◽  
Homologous Chromosome ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Meiotic Spindle ◽  
Meiotic Progression ◽  
Pole Body ◽  
Homologous Chromosome Pairing

The telomere bouquet, i.e., telomere clustering on the nuclear envelope (NE) during meiotic prophase, is thought to promote homologous chromosome pairing. Using a visual screen, we identified bqt2/im295, a mutant that disrupts telomere clustering in fission yeast. Bqt2p is required for linking telomeres to the meiotic spindle pole body (SPB) but not for attachment of telomeres or the SPB to the NE. Bqt2p is expressed upon pheromone sensing and colocalizes thereafter to Sad1p, an SPB protein. This localization only depends on Bqt1p, not on other identified proteins required for telomere clustering. Upon pheromone sensing, generation of Sad1p foci next to telomeres depends on Bqt2p. However, depletion of Bqt2p from the SPB is dispensable for dissolving the telomere bouquet at the end of meiotic prophase. Therefore, telomere bouquet formation requires Bqt2p as a linking component and is finely regulated during meiotic progression.

Oscillatory nuclear movement in fission yeast meiotic prophase is driven by astral microtubules, as revealed by continuous observation of chromosomes and microtubules in living cells

1998 ◽  
Vol 111 (6) ◽  
pp. 701-712 ◽  
Author(s):  
D.Q. Ding ◽  
Y. Chikashige ◽  
T. Haraguchi ◽  
Y. Hiraoka
Keyword(s):  
Fission Yeast ◽  
Meiotic Prophase ◽  
Fluorescent Protein ◽  
Dynamic Instability ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Living Cells ◽  
Continuous Observation ◽  
Nuclear Movement ◽  
Pole Body

Using a computerized fluorescence microscope system to observe fluorescently stained cellular structures in vivo, we have examined the dynamics of chromosomes and microtubules during the process of meiosis in the fission yeast Schizosaccharomyces pombe. Fission yeast meiotic prophase is characterized by a distinctive type of nuclear movement that is led by telomeres clustered at the spindle-pole body (the centrosome-equivalent structure in fungi): the nucleus oscillates back and forth along the cell axis, moving continuously between the two ends of the cell for some hours prior to the meiotic divisions. To obtain a dynamic view of this oscillatory nuclear movement in meiotic prophase, we visualized microtubules and chromosomes in living cells using jellyfish green fluorescent protein fused with alpha-tubulin and a DNA-specific fluorescent dye, Hoechst 33342, respectively. Continuous observation of chromosomes and microtubules in these cells demonstrated that the oscillatory nuclear movement is mediated by dynamic reorganization of astral microtubules originating from the spindle-pole body. During each half-oscillatory period, the microtubules extending rearward from the leading edge of the nucleus elongate to drive the nucleus to one end of the cell. When the nucleus reversed direction, its motion during the second half of the oscillation was not driven by the same microtubules that drove its motion during the first half, but rather by newly assembled microtubules. Reversible inhibition of nuclear movement by an inhibitor of microtubule polymerization, thiabendazole, confirmed the involvement of astral microtubules in oscillatory nuclear movement. The speed of the movement fluctuated within a range 0 to 15 micron/minute, with an average of about 5 microm/minute. We propose a model in which the oscillatory nuclear movement is mediated by dynamic instability and selective stabilization of astral microtubules.

Distinct nuclear and spindle pole body populations of cyclin–cdc2 in fission yeast

Nature ◽  
1990 ◽  
Vol 347 (6294) ◽  
pp. 680-682 ◽  
Author(s):  
Caroline E. Alfa ◽  
Bernard Ducommun ◽  
David Beach ◽  
Jeremy S. Hyams
Keyword(s):  
Fission Yeast ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Pole Body

scholarly journals The Fission Yeast Homolog of the Human Transcription Factor EAP30 Blocks Meiotic Spindle Pole Body Amplification

2005 ◽  
Vol 9 (1) ◽  
pp. 63-73 ◽  
Author(s):  
Ye Jin ◽  
Joel J. Mancuso ◽  
Satoru Uzawa ◽  
Daniela Cronembold ◽  
W. Zacheus Cande
Keyword(s):  
Transcription Factor ◽  
Fission Yeast ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Meiotic Spindle ◽  
Pole Body ◽  
Yeast Homolog ◽  
Human Transcription Factor
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