scholarly journals The phosphatase inhibitor Sds23 regulates cell division symmetry in fission yeast

2019 ◽  
Vol 30 (23) ◽  
pp. 2880-2889 ◽  
Author(s):  
Katherine L. Schutt ◽  
James B. Moseley
Keyword(s):  
Cell Division ◽  
Fission Yeast ◽  
Cell Polarity ◽  
Protein Phosphatase ◽  
Yeast Cells ◽  
Spatial Control ◽  
Anchoring Proteins ◽  
Family Protein ◽  
Mutant Cells ◽  
Assembly Site

Animal and fungal cells divide through the assembly, anchoring, and constriction of a contractile actomyosin ring (CAR) during cytokinesis. The timing and position of the CAR must be tightly controlled to prevent defects in cell division, but many of the underlying signaling events remain unknown. The conserved heterotrimeric protein phosphatase PP2A controls the timing of events in mitosis, and upstream pathways including Greatwall–Ensa regulate PP2A activity. A role for PP2A in CAR regulation has been less clear, although loss of PP2A in yeast causes defects in cytokinesis. Here, we report that Sds23, an inhibitor of PP2A family protein phosphatases, promotes the symmetric division of fission yeast cells through spatial control of cytokinesis. We found that sds23∆ cells divide asymmetrically due to misplaced CAR assembly, followed by sliding of the CAR away from its assembly site. These mutant cells exhibit delayed recruitment of putative CAR anchoring proteins including the glucan synthase Bgs1. Our observations likely reflect a broader role for regulation of PP2A in cell polarity and cytokinesis because sds23∆ phenotypes were exacerbated when combined with mutations in the fission yeast Ensa homologue, Igo1. These results identify the PP2A regulatory network as a critical component in the signaling pathways coordinating cytokinesis.

scholarly journals The phosphatase inhibitor Sds23 regulates cell division symmetry in fission yeast

2019 ◽  
Author(s):  
Katherine L. Schutt ◽  
James B. Moseley
Keyword(s):  
Cell Division ◽  
Fission Yeast ◽  
Cell Polarity ◽  
Protein Phosphatase ◽  
Yeast Cells ◽  
Spatial Control ◽  
Anchoring Proteins ◽  
Family Protein ◽  
Mutant Cells ◽  
Assembly Site

AbstractAnimal and fungal cells divide through the assembly, anchoring, and constriction of a contractile actomyosin ring (CAR) during cytokinesis. The timing and position of the CAR must be tightly controlled to prevent defects in cell division, but many of the underlying signaling events remain unknown. The conserved heterotrimeric protein phosphatase PP2A controls the timing of events in mitosis, and upstream pathways including Greatwall-Ensa regulate PP2A activity. A role for PP2A in CAR regulation has been less clear, although loss of PP2A in yeast causes defects in cytokinesis. Here, we report that Sds23, an inhibitor of PP2A family protein phosphatases, promotes the symmetric division of fission yeast cells through spatial control of cytokinesis. We found that sds23Δ cells divide asymmetrically due to misplaced CAR assembly, followed by sliding of the CAR away from its assembly site. These mutant cells exhibit delayed recruitment of putative CAR anchoring proteins including the glucan synthase Bgs1. Our observations likely reflect a broader role for regulation of PP2A in cell polarity and cytokinesis because sds23Δ phenotypes were exacerbated when combined with mutations in the fission yeast Ensa homolog, Igo1. These results identify the PP2A regulatory network as a critical component in the signaling pathways coordinating cytokinesis.

scholarly journals Fission yeast Pak1 phosphorylates anillin-like Mid1 for spatial control of cytokinesis

2019 ◽  
Author(s):  
Joseph O. Magliozzi ◽  
Jack Sears ◽  
Lauren Cressey ◽  
Marielle Brady ◽  
Hannah E. Opalko ◽  
...  
Keyword(s):  
Cell Division ◽  
Fission Yeast ◽  
Cell Polarity ◽  
Genetic Interactions ◽  
Polarized Growth ◽  
Signaling Mechanism ◽  
Spatial Control ◽  
Division Site ◽  
N Terminus ◽  
A Cell

AbstractProtein kinases direct polarized growth by regulating the cytoskeleton in time and space, and could play similar roles in cell division. We found that the Cdc42-activated polarity kinase Pak1 colocalizes with the assembling contractile actomyosin ring (CAR) and remains at the division site during septation. Mutations in pak1 led to defects in CAR assembly and genetic interactions with cytokinesis mutants. Through a phosphoproteomic screen, we identified novel Pak1 substrates that function in polarized growth and cytokinesis. For cytokinesis, we found that Pak1 regulates the localization of its substrates Mid1 and Cdc15 to the CAR. Mechanistically, Pak1 phosphorylates the Mid1 N-terminus to promote its association with cortical nodes that act as CAR precursors. Defects in Pak1-Mid1 signaling lead to misplaced and defective division planes, but these phenotypes can be rescued by synthetic tethering of Mid1 to cortical nodes. Our work defines a new signaling mechanism driven by a cell polarity kinase that promotes CAR assembly in the correct time and place.SummaryMagliozzi et al. show that fission yeast cell polarity kinase Pak1 regulates cytokinesis. Through a phosphoproteomic screen and subsequent mutant analysis, their work uncovers direct targets and mechanisms for Pak1 activity during cell division.

scholarly journals Compartmentalized nodes control mitotic entry signaling in fission yeast

2013 ◽  
Vol 24 (12) ◽  
pp. 1872-1881 ◽  
Author(s):  
Lin Deng ◽  
James B. Moseley
Keyword(s):  
Cell Cycle ◽  
Cell Growth ◽  
Fission Yeast ◽  
Cell Polarity ◽  
Cell Cycle Progression ◽  
Interaction Network ◽  
Yeast Cells ◽  
Cell Cortex ◽  
Cycle Progression ◽  
Mitotic Entry

Cell cycle progression is coupled to cell growth, but the mechanisms that generate growth-dependent cell cycle progression remain unclear. Fission yeast cells enter into mitosis at a defined size due to the conserved cell cycle kinases Cdr1 and Cdr2, which localize to a set of cortical nodes in the cell middle. Cdr2 is regulated by the cell polarity kinase Pom1, suggesting that interactions between cell polarity proteins and the Cdr1-Cdr2 module might underlie the coordination of cell growth and division. To identify the molecular connections between Cdr1/2 and cell polarity, we performed a comprehensive pairwise yeast two-hybrid screen. From the resulting interaction network, we found that the protein Skb1 interacted with both Cdr1 and the Cdr1 inhibitory target Wee1. Skb1 inhibited mitotic entry through negative regulation of Cdr1 and localized to both the cytoplasm and a novel set of cortical nodes. Skb1 nodes were distinct structures from Cdr1/2 nodes, and artificial targeting of Skb1 to Cdr1/2 nodes delayed entry into mitosis. We propose that the formation of distinct node structures in the cell cortex controls signaling pathways to link cell growth and division.

scholarly journals The number of cytokinesis nodes in mitotic fission yeast scales with cell volume

2021 ◽  
Author(s):  
Wasim A Sayyad ◽  
Thomas D Pollard
Keyword(s):  
Plasma Membrane ◽  
Fission Yeast ◽  
Large Population ◽  
Yeast Cells ◽  
Wild Type ◽  
Contractile Ring ◽  
Node Number ◽  
Nmt1 Promoter ◽  
Wide Range ◽  
Mutant Cells

Cytokinesis nodes are assemblies of stoichiometric ratios of proteins associated with the plasma membrane, which serve as precursors for the contractile ring during cytokinesis by fission yeast. The total number of nodes is uncertain, because of the limitations of the methods used previously. Here we used the ~140 nm resolution of Airyscan confocal microscopy to resolve a large population of dim, unitary cytokinesis nodes in 3D reconstructions of whole fission yeast cells. Wild-type fission yeast cells make about 200 unitary cytokinesis nodes. Most, but not all of these nodes condense into a contractile ring. The number of cytokinesis nodes scales with cell size in four strains tested, although wide rga4Δ mutant cells form somewhat fewer cytokinesis nodes than expected from the overall trend. The surface density of Pom1 kinase on the plasma membrane around the equators of cells is similar with a wide range of node numbers, so Pom1 does not control cytokinesis node number. However, varying protein concentrations with the nmt1 promoter showed that the numbers of nodes increase above a baseline of about 200 with the total cellular concentration of either Pom1 or the kinase Cdr2.

scholarly journals Schizosaccharomyces pombe Noc3 Is Essential for Ribosome Biogenesis and Cell Division but Not DNA Replication

2008 ◽  
Vol 7 (9) ◽  
pp. 1433-1440 ◽  
Author(s):  
Christopher R. Houchens ◽  
Audrey Perreault ◽  
François Bachand ◽  
Thomas J. Kelly
Keyword(s):  
Cell Division ◽  
Dna Replication ◽  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Ribosome Biogenesis ◽  
Budding Yeast ◽  
Ribosomal Subunit ◽  
Dna Helicase ◽  
Yeast Cells ◽  
Direct Role

ABSTRACT The initiation of eukaryotic DNA replication is preceded by the assembly of prereplication complexes (pre-RCs) at chromosomal origins of DNA replication. Pre-RC assembly requires the essential DNA replication proteins ORC, Cdc6, and Cdt1 to load the MCM DNA helicase onto chromatin. Saccharomyces cerevisiae Noc3 (ScNoc3), an evolutionarily conserved protein originally implicated in 60S ribosomal subunit trafficking, has been proposed to be an essential regulator of DNA replication that plays a direct role during pre-RC formation in budding yeast. We have cloned Schizosaccharomyces pombe noc3 + (Spnoc3 +), the S. pombe homolog of the budding yeast ScNOC3 gene, and functionally characterized the requirement for the SpNoc3 protein during ribosome biogenesis, cell cycle progression, and DNA replication in fission yeast. We showed that fission yeast SpNoc3 is a functional homolog of budding yeast ScNoc3 that is essential for cell viability and ribosome biogenesis. We also showed that SpNoc3 is required for the normal completion of cell division in fission yeast. However, in contrast to the proposal that ScNoc3 plays an essential role during DNA replication in budding yeast, we demonstrated that fission yeast cells do enter and complete S phase in the absence of SpNoc3, suggesting that SpNoc3 is not essential for DNA replication in fission yeast.

scholarly journals Mitochondrial mutagenesis in Saccharomyces cerevisiae: the origin of mit− mutants

1981 ◽  
Vol 38 (3) ◽  
pp. 267-279 ◽  
Author(s):  
Aleksandra Putrament ◽  
Anna Ejchart
Keyword(s):  
Cell Division ◽  
Mutant Allele ◽  
Yeast Cells ◽  
Mitochondrial Genomes ◽  
Mutagenic Treatment ◽  
The Third ◽  
A Cell ◽  
Selection For ◽  
A Minor ◽  
Mutant Cells

SUMMARYYeast cells contain many copies of mitochondrial (mit) genomes. The question we tried to answer was how mit− mutations occurring in one genome as a result of mutagenic treatment might yield homoplasmic mutant cells. Three processes were considered. First, that these cells originate by segregation of mutant and standard alleles during cell division. Secondly, that they originate through intracellular selection, for which cell division is not required. Thirdly, that recombination involving the mutant and standard alleles is non-reciprocal and unidirectional mit+ → mit− so that the mutant allele is spread into the entire population of mitochondrial genomes within a cell, thus making it homoplasmic mit−. The results indicate that the first process, although efficiently producing homoplasmic cells from heteroplasmic zygotes (for review see Birky, 1978), seems to play only a minor, if any, role in producing homoplasmic mutant progenies from mutagenized cells. The most important is the second process, that is, intracellular selection occurring in cells which have one or a few genomes carrying mit− mutations, while the remaining genomes are irreversibly damaged. The third process, unidirectional mit+ → mit− conversion, does not seem to play any part.

scholarly journals Regulation of Cell Polarity through Phosphorylation of Bni4 by Pho85 G1 Cyclin-dependent Kinases in Saccharomyces cerevisiae

2009 ◽  
Vol 20 (14) ◽  
pp. 3239-3250 ◽  
Author(s):  
Jian Zou ◽  
Helena Friesen ◽  
Jennifer Larson ◽  
Dongqing Huang ◽  
Mike Cox ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Polarity ◽  
Adaptor Protein ◽  
Yeast Cells ◽  
Genetic Screens ◽  
Yeast Saccharomyces Cerevisiae ◽  
Cyclin Dependent Kinases ◽  
Growth Defects ◽  
Bud Neck ◽  
Mutant Cells

In the budding yeast Saccharomyces cerevisiae, the G1-specific cyclin-dependent kinases (Cdks) Cln1,2-Cdc28 and Pcl1,2-Pho85 are essential for ensuring that DNA replication and cell division are properly linked to cell polarity and bud morphogenesis. However, the redundancy of Cdks and cyclins means that identification of relevant Cdk substrates remains a significant challenge. We used array-based genetic screens (synthetic genetic array or SGA analysis) to dissect redundant pathways associated with G1 cyclins and identified Bni4 as a substrate of the Pcl1- and Pcl2-Pho85 kinases. BNI4 encodes an adaptor protein that targets several proteins to the bud neck. Deletion of BNI4 results in severe growth defects in the absence of the Cdc28 cyclins Cln1 and Cln2, and overexpression of BNI4 is toxic in yeast cells lacking the Pho85 cyclins Pcl1 and Pcl2. Phosphorylation of Bni4 by Pcl-Pho85 is necessary for its localization to the bud neck, and the bud neck structure can be disrupted by overexpressing BNI4 in pcl1Δpcl2Δ mutant cells. Our data suggest that misregulated Bni4 may bind in an uncontrolled manner to an essential component that resides at the bud neck, causing catastrophic morphogenesis defects.

scholarly journals Fission yeast Pak1 phosphorylates anillin-like Mid1 for spatial control of cytokinesis

2020 ◽  
Vol 219 (8) ◽  
Author(s):  
Joseph O. Magliozzi ◽  
Jack Sears ◽  
Lauren Cressey ◽  
Marielle Brady ◽  
Hannah E. Opalko ◽  
...  
Keyword(s):  
Cell Division ◽  
Protein Kinases ◽  
Cell Polarity ◽  
Genetic Interactions ◽  
Polarized Growth ◽  
Signaling Mechanism ◽  
Spatial Control ◽  
Division Site ◽  
N Terminus ◽  
A Cell

Protein kinases direct polarized growth by regulating the cytoskeleton in time and space and could play similar roles in cell division. We found that the Cdc42-activated polarity kinase Pak1 colocalizes with the assembling contractile actomyosin ring (CAR) and remains at the division site during septation. Mutations in pak1 led to defects in CAR assembly and genetic interactions with cytokinesis mutants. Through a phosphoproteomic screen, we identified novel Pak1 substrates that function in polarized growth and cytokinesis. For cytokinesis, we found that Pak1 regulates the localization of its substrates Mid1 and Cdc15 to the CAR. Mechanistically, Pak1 phosphorylates the Mid1 N-terminus to promote its association with cortical nodes that act as CAR precursors. Defects in Pak1-Mid1 signaling lead to misplaced and defective division planes, but these phenotypes can be rescued by synthetic tethering of Mid1 to cortical nodes. Our work defines a new signaling mechanism driven by a cell polarity kinase that promotes CAR assembly in the correct time and place.

scholarly journals Mps1 expression is critical for chromosome orientation and segregation in yeast with high ploidy

2020 ◽  
Author(s):  
Ashlea Sartin ◽  
Madeline Gish ◽  
Jillian Harsha ◽  
Dawson Haworth ◽  
Rebecca LaVictoire ◽  
...  
Keyword(s):  
Cell Division ◽  
Chromosome Number ◽  
Cancer Cells ◽  
Chromosome Segregation ◽  
Daughter Cell ◽  
Yeast Cells ◽  
Loss Of Function ◽  
Master Regulator ◽  
High Ploidy ◽  
Mutant Cells

AbstractIn aneuploid cancer cells, the chromosome segregation apparatus is sensitive to increased chromosome number. The conserved protein kinase, Mps1, is a critical actor of this machinery, orienting the chromosomes properly on the spindle. Abnormally high levels of this kinase have been found in tumors with elevated chromosome number. However, it remains unclear, mechanistically, if and how cells with higher ploidy become dependent upon increased Mps1 levels. To answer these questions, we explored Mps1 dependence in yeast cells with increased sets of chromosomes. We discovered that having more chromosomes affects the ability of cells to orient chromosomes properly. The cells with increased numbers of chromosomes are particularly sensitive to the reduction of Mps1 activity. In mps1 loss of function mutants, cells display an extended prometaphase with a longer spindle and a delay in orienting properly the chromosomes. Altogether, our results suggest that increased numbers of chromosomes render cells more dependent on Mps1 for orienting chromosomes on the spindle. The phenomenon described here may be relevant in understanding why hyperdiploid cancer cells become excessively reliant on high Mps1 expression for successful chromosome segregation.Author summaryMost cells in solid tumors usually carry far more chromosomes than normal cells. Losing or gaining chromosomes during cell division can lead to aneuploidy (an abnormal number of chromosomes), cancer, and other diseases. Mps1 is a master regulator of cell division that is critical to keep the correct number chromosomes in each daughter cell. This master regulator has been shown to target and affect the function of various actors involved in cell division. Abnormally high levels of this master regulator are found in tumors with elevated chromosome numbers. The high levels of this regulator appear to be protecting these tumor cells. To answer if and how cells with higher ploidy become so dependent of Mps1, we generated yeast cells with increased set of chromosomes. Here, we report that cells with elevated chromosome number are particularly sensitive to the reduction of Mps1 level. In cells with higher ploidy and reduced level of Mps1, the progression during cell division is delayed. In the mutant cells, their ability to properly orient and segregate their chromosomes on the spindle is greatly reduced.

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