scholarly journals The half-bridge component Kar1 promotes centrosome separation and duplication during budding yeast meiosis

2018 ◽  
Vol 29 (15) ◽  
pp. 1798-1810
Author(s):  
Meenakshi Agarwal ◽  
Hui Jin ◽  
Melainia McClain ◽  
Jinbo Fan ◽  
Bailey A. Koch ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Budding Yeast ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Pole Body ◽  
Centrosome Separation ◽  
Chromatid Segregation ◽  
Yeast Meiosis ◽  
Unique Mechanism

The budding yeast centrosome, often called the spindle pole body (SPB), nucleates microtubules for chromosome segregation during cell division. An appendage, called the half bridge, attaches to one side of the SPB and regulates SPB duplication and separation. Like DNA, the SPB is duplicated only once per cell cycle. During meiosis, however, after one round of DNA replication, two rounds of SPB duplication and separation are coupled with homologue segregation in meiosis I and sister-chromatid segregation in meiosis II. How SPB duplication and separation are regulated during meiosis remains to be elucidated, and whether regulation in meiosis differs from that in mitosis is unclear. Here we show that overproduction of the half-bridge component Kar1 leads to premature SPB separation during meiosis. Furthermore, excessive Kar1 induces SPB overduplication to form supernumerary SPBs, leading to chromosome missegregation and erroneous ascospore formation. Kar1-­mediated SPB duplication bypasses the requirement of dephosphorylation of Sfi1, another half-bridge component previously identified as a licensing factor. Our results therefore reveal an unexpected role of Kar1 in licensing meiotic SPB duplication and suggest a unique mechanism of SPB regulation during budding yeast meiosis.

scholarly journals Meiotic telomere clustering requires actin for its formation and cohesin for its resolution

2005 ◽  
Vol 170 (2) ◽  
pp. 213-223 ◽  
Author(s):  
Edgar Trelles-Sticken ◽  
Caroline Adelfalk ◽  
Josef Loidl ◽  
Harry Scherthan
Keyword(s):  
Chromosome Segregation ◽  
Actin Polymerization ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Pole Body ◽  
Telomere Cluster ◽  
Cohesin Subunit ◽  
Yeast Meiosis ◽  
Bouquet Stage ◽  
Meiosis I

In diploid organisms, meiosis reduces the chromosome number by half during the formation of haploid gametes. During meiotic prophase, telomeres transiently cluster at a limited sector of the nuclear envelope (bouquet stage) near the spindle pole body (SPB). Cohesin is a multisubunit complex that contributes to chromosome segregation in meiosis I and II divisions. In yeast meiosis, deficiency for Rec8 cohesin subunit induces telomere clustering to persist, whereas telomere cluster–SPB colocalization is defective. These defects are rescued by expressing the mitotic cohesin Scc1 in rec8Δ meiosis, whereas bouquet-stage exit is independent of Cdc5 pololike kinase. An analysis of living Saccharomyces cerevisiae meiocytes revealed highly mobile telomeres from leptotene up to pachytene, with telomeres experiencing an actin- but not microtubule-dependent constraint of mobility during the bouquet stage. Our results suggest that cohesin is required for exit from actin polymerization–dependent telomere clustering and for linking the SPB to the telomere cluster in synaptic meiosis.

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 The Aurora kinase Ipl1 is necessary for spindle pole body cohesion during budding yeast meiosis

2011 ◽  
Vol 124 (17) ◽  
pp. 2891-2896 ◽  
Author(s):  
Katelan Shirk ◽  
Hui Jin ◽  
Thomas H. Giddings ◽  
Mark Winey ◽  
Hong-Guo Yu
Keyword(s):  
Budding Yeast ◽  
Spindle Pole Body ◽  
Aurora Kinase ◽  
Spindle Pole ◽  
Pole Body ◽  
Yeast Meiosis

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 N-terminal regions of Mps1 kinase determine functional bifurcation

2010 ◽  
Vol 189 (1) ◽  
pp. 41-56 ◽  
Author(s):  
Yasuhiro Araki ◽  
Linda Gombos ◽  
Suellen P.S. Migueleti ◽  
Lavanya Sivashanmugam ◽  
Claude Antony ◽  
...  
Keyword(s):  
Nuclear Envelope ◽  
Chemical Biology ◽  
Molecular Level ◽  
Budding Yeast ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Deletion Analysis ◽  
Checkpoint Activation ◽  
Pole Body ◽  
N Terminus

Mps1 is a conserved kinase that in budding yeast functions in duplication of the spindle pole body (SPB), spindle checkpoint activation, and kinetochore biorientation. The identity of Mps1 targets and the subdomains that convey specificity remain largely unexplored. Using a novel combination of systematic deletion analysis and chemical biology, we identified two regions within the N terminus of Mps1 that are essential for either SPB duplication or kinetochore biorientation. Suppression analysis of the MPS1 mutants defective in SPB duplication and biochemical enrichment of Mps1 identified the essential SPB components Spc29 and the yeast centrin Cdc31 as Mps1 targets in SPB duplication. Our data suggest that phosphorylation of Spc29 by Mps1 in G1/S recruits the Mps2–Bbp1 complex to the newly formed SPB to facilitate its insertion into the nuclear envelope. Mps1 phosphorylation of Cdc31 at the conserved T110 residue controls substrate binding to Kar1 protein. These findings explain the multiple SPB duplication defects of mps1 mutants on a molecular level.

scholarly journals Budding Yeast Bub2 Is Localized at Spindle Pole Bodies and Activates the Mitotic Checkpoint via a Different Pathway from Mad2

1999 ◽  
Vol 145 (5) ◽  
pp. 979-991 ◽  
Author(s):  
Roberta Fraschini ◽  
Elisa Formenti ◽  
Giovanna Lucchini ◽  
Simonetta Piatti
Keyword(s):  
Cell Cycle ◽  
Mitotic Spindle ◽  
Cell Cycle Progression ◽  
Budding Yeast ◽  
Spindle Pole Body ◽  
Mitotic Checkpoint ◽  
Spindle Pole ◽  
Cycle Progression ◽  
Spindle Pole Bodies

The mitotic checkpoint blocks cell cycle progression before anaphase in case of mistakes in the alignment of chromosomes on the mitotic spindle. In budding yeast, the Mad1, 2, 3, and Bub1, 2, 3 proteins mediate this arrest. Vertebrate homologues of Mad1, 2, 3, and Bub1, 3 bind to unattached kinetochores and prevent progression through mitosis by inhibiting Cdc20/APC-mediated proteolysis of anaphase inhibitors, like Pds1 and B-type cyclins. We investigated the role of Bub2 in budding yeast mitotic checkpoint. The following observations indicate that Bub2 and Mad1, 2 probably activate the checkpoint via different pathways: (a) unlike the other Mad and Bub proteins, Bub2 localizes at the spindle pole body (SPB) throughout the cell cycle; (b) the effect of concomitant lack of Mad1 or Mad2 and Bub2 is additive, since nocodazole-treated mad1 bub2 and mad2 bub2 double mutants rereplicate DNA more rapidly and efficiently than either single mutant; (c) cell cycle progression of bub2 cells in the presence of nocodazole requires the Cdc26 APC subunit, which, conversely, is not required for mad2 cells in the same conditions. Altogether, our data suggest that activation of the mitotic checkpoint blocks progression through mitosis by independent and partially redundant mechanisms.

scholarly journals γ-Tubulin plays a key role in inactivating APC/CCdh1 at the G1–S boundary

2012 ◽  
Vol 198 (5) ◽  
pp. 785-791 ◽  
Author(s):  
Heather Edgerton-Morgan ◽  
Berl R. Oakley
Keyword(s):  
Cell Cycle ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Cyclin B ◽  
Anaphase Promoting Complex ◽  
Gene Encoding ◽  
Localization Pattern ◽  
Pole Body ◽  
Dependent Inactivation

A γ-tubulin mutation in Aspergillus nidulans, mipA-D159, causes failure of inactivation of the anaphase-promoting complex/cyclosome (APC/C) in interphase, resulting in failure of cyclin B (CB) accumulation and removal of nuclei from the cell cycle. We have investigated the role of CdhA, the A. nidulans homologue of the APC/C activator protein Cdh1, in γ-tubulin–dependent inactivation of the APC/C. CdhA was not essential, but it targeted CB for destruction in G1, and APC/CCdhA had to be inactivated for the G1–S transition. mipA-D159 altered the localization pattern of CdhA, and deletion of the gene encoding CdhA allowed CB to accumulate in all nuclei in strains carrying mipA-D159. These data indicate that mipA-D159 causes a failure of inactivation of APC/CCdhA at G1–S, perhaps by altering its localization to the spindle pole body, and, thus, that γ-tubulin plays an important role in inactivating APC/CCdhA at this point in the cell cycle.

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