Fission Yeast Mutants Affecting Telomere Clustering and Meiosis-Specific Spindle Pole Body Integrity

Abstract In meiotic prophase of many eukaryotic organisms, telomeres attach to the nuclear envelope and form a polarized configuration called the bouquet. Bouquet formation is hypothesized to facilitate homologous chromosome pairing. In fission yeast, bouquet formation and telomere clustering occurs in karyogamy and persists throughout the horsetail stage. Here we report the isolation and characterization of six mutants from our screen for meiotic mutants. These mutants show defective telomere clustering as demonstrated by mislocalization of Swi6::GFP, a heterochromatin-binding protein, and Taz1p::GFP, a telomere-specific protein. These mutants define four complementation groups and are named dot1 to dot4—defective organization of telomeres. dot3 and dot4 are allelic to mat1-Mm and mei4, respectively. Immunolocalization of Sad1, a protein associated with the spindle pole body (SPB), in dot mutants showed an elevated frequency of multiple Sad1-nuclei signals relative to wild type. Many of these Sad1 foci were colocalized with Taz1::GFP. Impaired SPB structure and function were further demonstrated by failure of spore wall formation in dot1, by multiple Pcp1::GFP signals (an SPB component) in dot2, and by abnormal microtubule organizations during meiosis in dot mutants. The coincidence of impaired SPB functions with defective telomere clustering suggests a link between the SPB and the telomere cluster.

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HIV-1 Vpr Induces Defects in Mitosis, Cytokinesis, Nuclear Structure, and Centrosomes

Molecular Biology of the Cell ◽

10.1091/mbc.e03-09-0691 ◽

2004 ◽

Vol 15 (4) ◽

pp. 1793-1801 ◽

Cited By ~ 36

Author(s):

Fred Chang ◽

Fabio Re ◽

Sarah Sebastian ◽

Shelley Sazer ◽

Jeremy Luban

Keyword(s):

Fission Yeast ◽

Cell Cycle Progression ◽

Spindle Pole Body ◽

Spindle Pole ◽

Human Cells ◽

Yeast Cells ◽

M Cell ◽

Pole Body ◽

And Function ◽

Hiv 1

Human immunodeficiency virus type 1 (HIV-1) Vpr is a 15-kDa accessory protein that contributes to several steps in the viral replication cycle and promotes virus-associated pathology. Previous studies demonstrated that Vpr inhibits G2/M cell cycle progression in both human cells and in the fission yeast Schizosaccharomyces pombe. Here, we report that, upon induction of vpr expression, fission yeast exhibited numerous defects in the assembly and function of the mitotic spindle. In particular, two spindle pole body proteins, sad1p and the polo kinase plo1p, were delocalized in vpr-expressing yeast cells, suggesting that spindle pole body integrity was perturbed. In addition, nuclear envelope structure, contractile actin ring formation, and cytokinesis were also disrupted. Similar Vpr-induced defects in mitosis and cytokinesis were observed in human cells, including aberrant mitotic spindles, multiple centrosomes, and multinucleate cells. These defects in cell division and centrosomes might account for some of the pathological effects associated with HIV-1 infection.

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

The Journal of Cell Biology ◽

10.1083/jcb.200602152 ◽

2006 ◽

Vol 173 (6) ◽

pp. 845-851 ◽

Cited By ~ 23

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.

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The product of the spindle formation gene sad1+ associates with the fission yeast spindle pole body and is essential for viability.

The Journal of Cell Biology ◽

10.1083/jcb.129.4.1033 ◽

1995 ◽

Vol 129 (4) ◽

pp. 1033-1047 ◽

Cited By ~ 265

Author(s):

I Hagan ◽

M Yanagida

Keyword(s):

Fission Yeast ◽

Nuclear Membrane ◽

Essential Gene ◽

Nuclear Periphery ◽

Spindle Pole Body ◽

Spindle Pole ◽

Temperature Sensitive ◽

Spindle Formation ◽

Isolation And Characterization ◽

Pole Body

Spindle formation in fission yeast occurs by the interdigitation of two microtubule arrays extending from duplicated spindle pole bodies which span the nuclear membrane. By screening a bank of temperature-sensitive mutants by anti-tubulin immunofluorescence microscopy, we previously identified the sad1.1 mutation (Hagan, I., and M. Yanagida. 1990. Nature (Lond.). 347:563-566). Here we describe the isolation and characterization of the sad1+ gene. We show that the sad1.1 mutation affected both spindle formation and function. The sad1+ gene is a novel essential gene that encodes a protein with a predicted molecular mass of 58 kD. Deletion of the gene was lethal resulting in identical phenotypes to the sad1.1 mutation. Sequence analysis predicted a potential membrane-spanning domain and an acidic amino terminus. Sad1 protein migrated as two bands of 82 and 84 kD on SDS-PAGE, considerably slower than its predicted mobility, and was exclusively associated with the spindle pole body (SPB) throughout the mitotic and meiotic cycles. Microtubule integrity was not required for Sad1 association with the SPB. Upon the differentiation of the SPB in metaphase of meiosis II, Sad1-staining patterns similarly changed from a dot to a crescent supporting an integral role in SPB function. Moderate overexpression of Sad1 led to association with the nuclear periphery. As Sad1 was not detected in the cytoplasmic microtubule-organizing centers activated at the end of anaphase or kinetochores, we suggest that Sad1 is not a general component of microtubule-interacting structures per se, but is an essential mitotic component that associates with the SPB but is not required for microtubule nucleation. Sad1 may play a role in SPB structure, such as maintaining a functional interface with the nuclear membrane or in providing an anchor for the attachment of microtubule motor proteins.

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Faculty Opinions recommendation of Fission yeast Myo51 is a meiotic spindle pole body component with discrete roles during cell fusion and spore formation.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.2137023.1737135 ◽

2010 ◽

Author(s):

Christopher McInerny

Keyword(s):

Fission Yeast ◽

Cell Fusion ◽

Spindle Pole Body ◽

Spindle Pole ◽

Spore Formation ◽

Meiotic Spindle ◽

Pole Body ◽

Body Component

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Ady3p Links Spindle Pole Body Function to Spore Wall Synthesis in Saccharomyces cerevisiae

Genetics ◽

10.1093/genetics/160.4.1439 ◽

2002 ◽

Vol 160 (4) ◽

pp. 1439-1450

Author(s):

Mark E Nickas ◽

Aaron M Neiman

Keyword(s):

Saccharomyces Cerevisiae ◽

De Novo ◽

Spindle Pole Body ◽

Leading Edge ◽

Spindle Pole ◽

Spore Wall ◽

Pole Body ◽

Prospore Membrane ◽

Sporulation Efficiency ◽

Spore Walls

Abstract Spore formation in Saccharomyces cerevisiae requires the de novo synthesis of prospore membranes and spore walls. Ady3p has been identified as an interaction partner for Mpc70p/Spo21p, a meiosis-specific component of the outer plaque of the spindle pole body (SPB) that is required for prospore membrane formation, and for Don1p, which forms a ring-like structure at the leading edge of the prospore membrane during meiosis II. ADY3 expression has been shown to be induced in midsporulation. We report here that Ady3p interacts with additional components of the outer and central plaques of the SPB in the two-hybrid assay. Cells that lack ADY3 display a decrease in sporulation efficiency, and most ady3Δ/ady3Δ asci that do form contain fewer than four spores. The sporulation defect in ady3Δ/ady3Δ cells is due to a failure to synthesize spore wall polymers. Ady3p forms ring-like structures around meiosis II spindles that colocalize with those formed by Don1p, and Don1p rings are absent during meiosis II in ady3Δ/ady3Δ cells. In mpc70Δ/mpc70Δ cells, Ady3p remains associated with SPBs during meiosis II. Our results suggest that Ady3p mediates assembly of the Don1p-containing structure at the leading edge of the prospore membrane via interaction with components of the SPB and that this structure is involved in spore wall formation.

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

Nature ◽

10.1038/347680a0 ◽

1990 ◽

Vol 347 (6294) ◽

pp. 680-682 ◽

Cited By ~ 110

Author(s):

Caroline E. Alfa ◽

Bernard Ducommun ◽

David Beach ◽

Jeremy S. Hyams

Keyword(s):

Fission Yeast ◽

Spindle Pole Body ◽

Spindle Pole ◽

Pole Body

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

Developmental Cell ◽

10.1016/j.devcel.2005.04.016 ◽

2005 ◽

Vol 9 (1) ◽

pp. 63-73 ◽

Cited By ~ 20

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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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

Molecular Biology of the Cell ◽

10.1091/mbc.e17-08-0497 ◽

2017 ◽

Vol 28 (25) ◽

pp. 3647-3659 ◽

Cited By ~ 23

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.

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