scholarly journals Ppc89 Links Multiple Proteins, Including the Septation Initiation Network, to the Core of the Fission Yeast Spindle-Pole Body

2006 ◽  
Vol 17 (9) ◽  
pp. 3793-3805 ◽  
Author(s):  
Joshua A. Rosenberg ◽  
Gregory C. Tomlin ◽  
W. Hayes McDonald ◽  
Brian E. Snydsman ◽  
Eric G. Muller ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Uncharacterized Protein ◽  
Central Function ◽  
Pole Body ◽  
Organizing Center ◽  
Septation Initiation Network ◽  
Ring Constriction ◽  
Essential Function

The spindle-pole body (SPB), the yeast analog of the centrosome, serves as the major microtubule (MT) organizing center in the yeast cell. In addition to this central function, the SPB organizes and concentrates proteins required for proper coordination between the nuclear-division cycle and cytokinesis. For example, the Schizosaccharomyces pombe septation-initiation network (SIN), which is responsible for initiating actomyosin ring constriction and septation, is assembled at the SPB through its two scaffolding components, Sid4 and Cdc11. In an effort to identify novel SIN interactors, we purified Cdc11 and identified by mass spectrometry a previously uncharacterized protein associated with it, Ppc89. Ppc89 localizes constitutively to the SPB and interacts directly with Sid4. A fusion between the N-terminal 300 amino acids of Sid4 and a SPB targeting domain of Ppc89 supplies the essential function of Sid4 in anchoring the SIN. ppc89Δ cells are inviable and exhibit defects in SPB integrity, and hence in spindle formation, chromosome segregation, and SIN localization. Ppc89 overproduction is lethal, resulting primarily in a G2 arrest accompanied by massive enlargement of the SPB and increased SPB MT nucleation. These results suggest a fundamental role for Ppc89 in organization of the S. pombe SPB.

scholarly journals Relief of the Dma1-mediated checkpoint requires Dma1 autoubiquitination and dynamic localization

2018 ◽  
Vol 29 (18) ◽  
pp. 2176-2189 ◽  
Author(s):  
Christine M. Jones ◽  
Jun-Song Chen ◽  
Alyssa E. Johnson ◽  
Zachary C. Elmore ◽  
Sierra N. Cullati ◽  
...  
Keyword(s):  
Cell Division ◽  
Chromosome Segregation ◽  
Ubiquitin Ligase ◽  
Spindle Pole Body ◽  
Mitotic Checkpoint ◽  
Spindle Pole ◽  
Checkpoint Activation ◽  
Pole Body ◽  
Septation Initiation Network ◽  
Anaphase B

Chromosome segregation and cell division are coupled to prevent aneuploidy and cell death. In the fission yeast Schizosaccharomyces pombe, the septation initiation network (SIN) promotes cytokinesis, but upon mitotic checkpoint activation, the SIN is actively inhibited to prevent cytokinesis from occurring before chromosomes have safely segregated. SIN inhibition during the mitotic checkpoint is mediated by the E3 ubiquitin ligase Dma1. Dma1 binds to the CK1-phosphorylated SIN scaffold protein Sid4 at the spindle pole body (SPB), and ubiquitinates it. Sid4 ubiquitination antagonizes the SPB localization of the Pololike kinase Plo1, the major SIN activator, so that SIN signaling is delayed. How this checkpoint is silenced once spindle defects are resolved has not been clear. Here we establish that Dma1 transiently leaves SPBs during anaphase B due to extensive autoubiquitination. The SIN is required for Dma1 to return to SPBs later in anaphase. Blocking Dma1 removal from SPBs by permanently tethering it to Sid4 prevents SIN activation and cytokinesis. Therefore, controlling Dma1’s SPB dynamics in anaphase is an essential step in S. pombe cell division and the silencing of the Dma1-dependent mitotic checkpoint.

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 Cdk1 promotes cytokinesis in fission yeast through activation of the septation initiation network

2014 ◽  
Vol 25 (15) ◽  
pp. 2250-2259 ◽  
Author(s):  
Nicole Rachfall ◽  
Alyssa E. Johnson ◽  
Sapna Mehta ◽  
Jun-Song Chen ◽  
Kathleen L. Gould
Keyword(s):  
Cell Cycle ◽  
Spindle Pole Body ◽  
Complete Removal ◽  
Spindle Pole ◽  
Cyclin Dependent Kinase ◽  
Gtpase Activating Protein ◽  
Pole Body ◽  
Kinase Cascade ◽  
Septation Initiation Network ◽  
Cycle Dependent

In Schizosaccharomyces pombe, late mitotic events are coordinated with cytokinesis by the septation initiation network (SIN), an essential spindle pole body (SPB)–associated kinase cascade, which controls the formation, maintenance, and constriction of the cytokinetic ring. It is not fully understood how SIN initiation is temporally regulated, but it depends on the activation of the GTPase Spg1, which is inhibited during interphase by the essential bipartite GTPase-activating protein Byr4-Cdc16. Cells are particularly sensitive to the modulation of Byr4, which undergoes cell cycle–dependent phosphorylation presumed to regulate its function. Polo-like kinase, which promotes SIN activation, is partially responsible for Byr4 phosphorylation. Here we show that Byr4 is also controlled by cyclin-dependent kinase (Cdk1)–mediated phosphorylation. A Cdk1 nonphosphorylatable Byr4 phosphomutant displays severe cell division defects, including the formation of elongated, multinucleate cells, failure to maintain the cytokinetic ring, and compromised SPB association of the SIN kinase Cdc7. Our analyses show that Cdk1-mediated phosphoregulation of Byr4 facilitates complete removal of Byr4 from metaphase SPBs in concert with Plo1, revealing an unexpected role for Cdk1 in promoting cytokinesis through activation of the SIN pathway.

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 S. pombe cdc11p, together with sid4p, provides an anchor for septation initiation network proteins on the spindle pole body

2001 ◽  
Vol 11 (20) ◽  
pp. 1559-1568 ◽  
Author(s):  
Andrea Krapp ◽  
Susanne Schmidt ◽  
Elena Cano ◽  
Viesturs Simanis
Keyword(s):  
Spindle Pole Body ◽  
Spindle Pole ◽  
Pole Body ◽  
Septation Initiation Network

scholarly journals Spc24 interacts with Mps2 and is required for chromosome segregation, but is not implicated in spindle pole body duplication

2002 ◽  
Vol 43 (6) ◽  
pp. 1431-1443 ◽  
Author(s):  
Ivan Le Masson ◽  
Cosmin Saveanu ◽  
Anne Chevalier ◽  
Abdelkader Namane ◽  
Renee Gobin ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Pole Body

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.

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