Microtubule Architectural Dynamics Determine Cell Shape and Cell Division Site in Fission Yeast

AbstractThe fission yeast cell is shaped as a very regular cylinder ending by hemi-spheres at both cell ends. Its conserved phenotypes are often used as read-outs for classifying interacting genes and protein networks. Using Pascal and Young-Laplace laws, we proposed a framework where scaling arguments predicted shapes. Here we probed quantitatively one of these relations which predicts that the division site would be located closer to the cell end with the larger radius of curvature. By combining genetics and quantitative imaging, we tested experimentally whether altered shapes of cell end correlate with a displaced division site, leading to asymmetric cell division. Our results show that the division site position depends on the radii of curvatures of both ends. This new geometrical mechanism for the proper division plane positioning could be essential to achieve even partitioning of cellular material at each cell division.

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Electron Tomography in the Study of Bacterial Structure and Function

Microscopy Today ◽

10.1017/s1551929500050811 ◽

2005 ◽

Vol 13 (1) ◽

pp. 22-25

Author(s):

Kenneth H. Downing ◽

Haixin Sui ◽

Luis R. Comolli ◽

Hoi-Ying Holman

Keyword(s):

Cell Division ◽

Cell Shape ◽

Electron Tomography ◽

Structure And Function ◽

Interacting Proteins ◽

Ultrastructural Studies ◽

Division Site ◽

Metabolic Functions ◽

Bacterial Structure ◽

And Function

Bacteria contain a wealth of mechanisms that organize their internal and external components into a highly polar structure, frequently with distinctive shape, and constrain certain metabolic functions to particular parts of the cell. For example, cell division generally takes place at the middle of the cell, and a host of interacting proteins are involved in ensuring that the division site is positioned properly. Thus, in spite of the lingering perception among some scientists that these cells are simply bags of freely diffusing enzymes, there is much to be learned from ultrastructural studies. Light microscopy has given evidence of cytoskeletal components that presumably establish and maintain cell shape and participate in cell division.

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

10.1101/722900 ◽

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.

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Gef1p and Scd1p, the Two GDP-GTP Exchange Factors for Cdc42p, Form a Ring Structure that Shrinks during Cytokinesis inSchizosaccharomyces pombe

Molecular Biology of the Cell ◽

10.1091/mbc.e02-10-0665 ◽

2003 ◽

Vol 14 (9) ◽

pp. 3617-3627 ◽

Cited By ~ 45

Author(s):

Kouji Hirota ◽

Kayoko Tanaka ◽

Kunihiro Ohta ◽

Masayuki Yamamoto

Keyword(s):

Cell Proliferation ◽

Cell Division ◽

Fission Yeast ◽

Cell Morphology ◽

Ring Structure ◽

Small Gtpase ◽

Parallel Study ◽

Division Site ◽

Rho Family ◽

Synthetically Lethal

Fission yeast Cdc42p, a small GTPase of the Rho family, is essential for cell proliferation and maintenance of the rod-like cell morphology. Scd1/Ral1p is a GDP-GTP exchange factor (GEF) for Cdc42p. This study and a parallel study by others establish that Gef1p is another GEF for Cdc42p. Deletions of gef1 and scd1 are synthetically lethal, generating round dead cells, and hence mimic the phenotype of cdc42 deletion. Gef1p is localized mainly to the cell division site. Scd1p is also there, but it is also detectable in other parts of the cell, including the nucleus, growing ends, and the tips of conjugation tubes. Gef1p and Scd1p form a ring structure at the cell division site, which shrinks during cytokinesis following the contraction of the actomyosin ring. Formation of the Gef1p/Scd1p ring apparently depends on the integrity of the actomyosin ring. In turn, recruitment of Cdc42p to the cell division site follows the shrinking Gef1p/Scd1p ring; the Cdc42p accumulates like a closing iris. These observations suggest that Gef1p and Scd1p may have a role in mediating between contraction of the actomyosin ring and formation of the septum, by recruiting active Cdc42p to the septation site.

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A novel interplay between GEFs orchestrates Cdc42 activity during cell polarity and cytokinesis

10.1101/364786 ◽

2018 ◽

Cited By ~ 3

Author(s):

Brian S. Hercyk ◽

Julie T. Rich-Robinson ◽

Ahmad S. Mitoubsi ◽

Marcus A. Harrell ◽

Maitreyi E. Das

Keyword(s):

Fission Yeast ◽

Cell Polarity ◽

Cell Separation ◽

Cell Shape ◽

Functional Sites ◽

Cellular Processes ◽

Division Site ◽

Summary Statement ◽

Fine Tune ◽

Do So

ABSTRACTCdc42, a conserved regulator of cell polarity, is activated by two GEFs, Gef1 and Scd1, in fission yeast. Whilegef1andscd1mutants exhibit distinct phenotypes, how they do so is unclear given that they activate the same GTPase. Using the GEF localization pattern during cytokinesis as a paradigm, we report a novel interplay between Gef1 and Scd1 that spatially modulates Cdc42. We find that Gef1 promotes Scd1 localization to the division site during cytokinesis and to the new end during polarized growth through the recruitment of the scaffold Scd2 via a Cdc42 feedforward pathway. Gef1-mediated Scd1 recruitment at the new end enables the transition from monopolar to bipolar growth. Reciprocally, Scd1 restricts Gef1 localization to prevent ectopic Cdc42 activation during cytokinesis to promote cell separation and during interphase to maintain cell shape. Our findings reveal an elegant regulatory pattern in which Gef1 establishes new sites of Scd1-mediated Cdc42 activity, while Scd1 restricts Gef1 to functional sites. We propose that crosstalk between GEFs is a conserved mechanism that orchestrates Cdc42 activation during complex cellular processes.Summary StatementCdc42 GEFs Gef1 and Scd1 crosstalk to fine-tune Cdc42 activity. This crosstalk promotes bipolar growth and maintains cell shape in fission yeast.

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An anillin homologue, Mid2p, acts during fission yeast cytokinesis to organize the septin ring and promote cell separation

The Journal of Cell Biology ◽

10.1083/jcb.200211126 ◽

2003 ◽

Vol 160 (7) ◽

pp. 1093-1103 ◽

Cited By ~ 100

Author(s):

Joseph J. Tasto ◽

Jennifer L. Morrell ◽

Kathleen L. Gould

Keyword(s):

Cell Cycle ◽

Cell Division ◽

Fission Yeast ◽

Cell Separation ◽

Cell Cycle Progression ◽

Dependent Manner ◽

Septin Ring ◽

Protein Levels ◽

Division Site ◽

Cell Biol

Anillin is a conserved protein required for cell division (Field, C.M., and B.M. Alberts. 1995. J. Cell Biol. 131:165–178; Oegema, K., M.S. Savoian, T.J. Mitchison, and C.M. Field. 2000. J. Cell Biol. 150:539–552). One fission yeast homologue of anillin, Mid1p, is necessary for the proper placement of the division site within the cell (Chang, F., A. Woollard, and P. Nurse. 1996. J. Cell Sci. 109(Pt 1):131–142; Sohrmann, M., C. Fankhauser, C. Brodbeck, and V. Simanis. 1996. Genes Dev. 10:2707–2719). Here, we identify and characterize a second fission yeast anillin homologue, Mid2p, which is not orthologous with Mid1p. Mid2p localizes as a single ring in the middle of the cell after anaphase in a septin- and actin-dependent manner and splits into two rings during septation. Mid2p colocalizes with septins, and mid2Δ cells display disorganized, diffuse septin rings and a cell separation defect similar to septin deletion strains. mid2 gene expression and protein levels fluctuate during the cell cycle in a sep1- and Skp1/Cdc53/F-box (SCF)–dependent manner, respectively, implying that Mid2p activity must be carefully regulated. Overproduction of Mid2p depolarizes cell growth and affects the organization of both the septin and actin cytoskeletons. In the presence of a nondegradable Mid2p fragment, the septin ring is stabilized and cell cycle progression is delayed. These results suggest that Mid2p influences septin ring organization at the site of cell division and its turnover might normally be required to permit septin ring disassembly.

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Studies in Fission Yeast on Mechanisms of Cell Division Site Placement

Cell Structure and Function ◽

10.1247/csf.26.539 ◽

2001 ◽

Vol 26 (6) ◽

pp. 539-544 ◽

Cited By ~ 13

Author(s):

Fred Chang

Keyword(s):

Cell Division ◽

Fission Yeast ◽

Division Site

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A nitrogen starvation-induced dormant G0 state in fission yeast: the establishment from uncommitted G1 state and its delay for return to proliferation

Journal of Cell Science ◽

10.1242/jcs.109.6.1347 ◽

1996 ◽

Vol 109 (6) ◽

pp. 1347-1357 ◽

Cited By ~ 12

Author(s):

S.S. Su ◽

Y. Tanaka ◽

I. Samejima ◽

K. Tanaka ◽

M. Yanagida

Keyword(s):

Cell Division ◽

Fission Yeast ◽

Cell Shape ◽

Nitrogen Starvation ◽

Stable State ◽

Mitotic Cell ◽

Yeast Cells ◽

Dormant Cells ◽

State Dependent ◽

G1 Cells

Fission yeast cells either remain in the mitotic cell cycle or exit to meiotic sporulation from an uncommitted G1 state dependent on the presence or absence of nitrogen source in the medium (Nurse and Bissett, 1981). We examined how heterothallic haploid cells, which cannot sporulate, behave under nitrogen-starvation for longer than 25 days at 26 degrees C. These cells were shown to enter a stable state (designated the dormant G0) with nearly full viability. Maintaining the dormant cells required glucose, suggesting that the cells remained metabolically active although cell division had ceased. They differed dramatically from mitotic and uncommitted G1 cells in heat resistance, and also in cytoplasmic and nuclear morphologies. After nitrogen replenishment, the initial responses of dormant G0 cells were investigated. The kinetics for reentry into the proliferative state were delayed considerably, and the changes in cell shape were enhanced particularly for those recovering from extended nitrogen starvation. A part of the delay could be accounted for by the duration of nuclear decondensation and cell elongation for the first cell division.

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