scholarly journals Cytokinetic nodes in fission yeast arise from two distinct types of nodes that merge during interphase

2014 ◽  
Vol 204 (6) ◽  
pp. 977-988 ◽  
Author(s):  
Matthew Akamatsu ◽  
Julien Berro ◽  
Kai-Ming Pu ◽  
Irene R. Tebbs ◽  
Thomas D. Pollard
Keyword(s):  
Fission Yeast ◽  
Fusion Proteins ◽  
Contractile Ring ◽  
Guanosine Triphosphate ◽  
Quantitative Measurements ◽  
Capture Mechanism ◽  
Septation Initiation Network ◽  
Stationary Type

We investigated the assembly of cortical nodes that generate the cytokinetic contractile ring in fission yeast. Observations of cells expressing fluorescent fusion proteins revealed two types of interphase nodes. Type 1 nodes containing kinase Cdr1p, kinase Cdr2p, and anillin Mid1p form in the cortex around the nucleus early in G2. Type 2 nodes with protein Blt1p, guanosine triphosphate exchange factor Gef2p, and kinesin Klp8p emerge from contractile ring remnants. Quantitative measurements and computer simulations showed that these two types of nodes come together by a diffuse-and-capture mechanism: type 2 nodes diffuse to the equator and are captured by stationary type 1 nodes. During mitosis, cytokinetic nodes with Mid1p and all of the type 2 node markers incorporate into the contractile ring, whereas type 1 nodes with Cdr1p and Cdr2p follow the separating nuclei before dispersing into the cytoplasm, dependent on septation initiation network signaling. The two types of interphase nodes follow parallel branches of the pathway to prepare nodes for cytokinesis.

scholarly journals Analysis of interphase node proteins in fission yeast by quantitative and superresolution fluorescence microscopy

2017 ◽  
Vol 28 (23) ◽  
pp. 3203-3214 ◽  
Author(s):  
Matthew Akamatsu ◽  
Yu Lin ◽  
Joerg Bewersdorf ◽  
Thomas D. Pollard
Keyword(s):  
Cell Cycle ◽  
Fission Yeast ◽  
Steady Increase ◽  
Contractile Ring ◽  
Superresolution Microscopy ◽  
Quantitative Measurements ◽  
Two Phases ◽  
Rho Gef

We used quantitative confocal microscopy and FPALM superresolution microscopy of live fission yeast to investigate the structures and assembly of two types of interphase nodes—multiprotein complexes associated with the plasma membrane that merge together and mature into the precursors of the cytokinetic contractile ring. During the long G2 phase of the cell cycle, seven different interphase node proteins maintain constant concentrations as they accumulate in proportion to cell volume. During mitosis, the total numbers of type 1 node proteins (cell cycle kinases Cdr1p, Cdr2p, Wee1p, and anillin Mid1p) are constant even when the nodes disassemble. Quantitative measurements provide strong evidence that both types of nodes have defined sizes and numbers of constituent proteins, as observed for cytokinesis nodes. Type 1 nodes assemble in two phases—a burst at the end of mitosis, followed by steady increase during interphase to double the initial number. Type 2 nodes containing Blt1p, Rho-GEF Gef2p, and kinesin Klp8p remain intact throughout the cell cycle and are constituents of the contractile ring. They are released from the contractile ring as it disassembles and then associate with type 1 nodes around the equator of the cell during interphase.

scholarly journals Analysis of interphase node proteins in fission yeast by quantitative and super resolution fluorescence microscopy

2017 ◽  
Author(s):  
Matthew Akamatsu ◽  
Yu Lin ◽  
Joerg Bewersdorf ◽  
Thomas D. Pollard
Keyword(s):  
Cell Cycle ◽  
Confocal Microscopy ◽  
Fission Yeast ◽  
Super Resolution ◽  
Steady Increase ◽  
Contractile Ring ◽  
Two Phases ◽  
Super Resolution Microscopy

AbstractWe used quantitative confocal microscopy and FPALM super resolution microscopy of live fission yeast to investigate the structures and assembly of two types of interphase nodes, multiprotein complexes associated with the plasma membrane that merge together and mature into the precursors of the cytokinetic contractile ring. During the long G2 phase of the cell cycle seven different interphase node proteins maintain constant concentrations as they accumulate in proportion to cell volume. During mitosis the total numbers of type 1 node proteins (cell cycle kinases Cdr1p, Cdr2p, Wee1p, and anillin Mid1p) are constant even when the nodes disassemble. Quantitative measurements provide strong evidence that both types of nodes have defined sizes and numbers of constituent proteins, as observed for cytokinesis nodes. Type 1 nodes assemble in two phases, a burst at the end of mitosis, followed by steady increase during interphase to double the initial number. Type 2 nodes containing Blt1p, Rho-GEF Gef2p, and kinesin Klp8p remain intact throughout the cell cycle and are constituents of the contractile ring. They are released from the contractile ring as it disassembles and then associate with type 1 nodes around the equator of the cell during interphase.Highlight summaryFPALM super resolution microscopy and quantitative confocal microscopy reveal that interphase nodes, the precursors to the fission yeast cytokinetic contractile ring, are discrete unitary structures with defined sizes and ratios of component proteins. Type 1 nodes disassemble during mitosis, but type 2 nodes remain intact throughout the cell cycle.

scholarly journals Assembly of the cytokinetic contractile ring from a broad band of nodes in fission yeast

2006 ◽  
Vol 174 (3) ◽  
pp. 391-402 ◽  
Author(s):  
Jian-Qiu Wu ◽  
Vladimir Sirotkin ◽  
David R. Kovar ◽  
Matthew Lord ◽  
Christopher C. Beltzner ◽  
...  
Keyword(s):  
Fission Yeast ◽  
Fusion Proteins ◽  
Cell Separation ◽  
Actin Polymerization ◽  
Myosin Ii ◽  
Broad Band ◽  
Compact Ring ◽  
Contractile Ring ◽  
Single Spot ◽  
Anaphase B

We observed live fission yeast expressing pairs of functional fluorescent fusion proteins to test the popular model that the cytokinetic contractile ring assembles from a single myosin II progenitor or a Cdc12p-Cdc15p spot. Under our conditions, the anillin-like protein Mid1p establishes a broad band of small dots or nodes in the cortex near the nucleus. These nodes mature by the addition of conventional myosin II (Myo2p, Cdc4p, and Rlc1p), IQGAP (Rng2p), pombe Cdc15 homology protein (Cdc15p), and formin (Cdc12p). The nodes coalesce laterally into a compact ring when Cdc12p and profilin Cdc3p stimulate actin polymerization. We did not observe assembly of contractile rings by extension of a leading cable from a single spot or progenitor. Arp2/3 complex and its activators accumulate in patches near the contractile ring early in anaphase B, but are not concentrated in the contractile ring and are not required for assembly of the contractile ring. Their absence delays late steps in cytokinesis, including septum formation and cell separation.

scholarly journals Characterization of the roles of Blt1p in fission yeast cytokinesis

2014 ◽  
Vol 25 (13) ◽  
pp. 1946-1957 ◽  
Author(s):  
John W. Goss ◽  
Sunhee Kim ◽  
Hannah Bledsoe ◽  
Thomas D. Pollard
Keyword(s):  
Cell Division ◽  
Fission Yeast ◽  
Cell Separation ◽  
Analytical Ultracentrifugation ◽  
Contractile Ring ◽  
Glucan Synthase ◽  
Temporal Regulation ◽  
Septation Initiation Network ◽  
Ring Constriction

Spatial and temporal regulation of cytokinesis is essential for cell division, yet the mechanisms that control the formation and constriction of the contractile ring are incompletely understood. In the fission yeast Schizosaccharomyces pombe proteins that contribute to the cytokinetic contractile ring accumulate during interphase in nodes—precursor structures around the equatorial cortex. During mitosis, additional proteins join these nodes, which condense to form the contractile ring. The cytokinesis protein Blt1p is unique in being present continuously in nodes from early interphase through to the contractile ring until cell separation. Blt1p was shown to stabilize interphase nodes, but its functions later in mitosis were unclear. We use analytical ultracentrifugation to show that purified Blt1p is a tetramer. We find that Blt1p interacts physically with Sid2p and Mob1p, a protein kinase complex of the septation initiation network, and confirm known interactions with F-BAR protein Cdc15p. Contractile rings assemble normally in blt1∆ cells, but the initiation of ring constriction and completion of cell division are delayed. We find three defects that likely contribute to this delay. Without Blt1p, contractile rings recruited and retained less Sid2p/Mob1p and Clp1p phosphatase, and β-glucan synthase Bgs1p accumulated slowly at the cleavage site.

scholarly journals Schizosaccharomyces pombe Pxl1 Is a Paxillin Homologue That Modulates Rho1 Activity and Participates in Cytokinesis

2008 ◽  
Vol 19 (4) ◽  
pp. 1727-1738 ◽  
Author(s):  
Mario Pinar ◽  
Pedro M. Coll ◽  
Sergio A. Rincón ◽  
Pilar Pérez
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Rho Gtpases ◽  
Actin Polymerization ◽  
Cell Integrity ◽  
Contractile Ring ◽  
Cytoskeleton Organization ◽  
Lim Domains ◽  
Actin Cytoskeleton Organization ◽  
Septation Initiation Network

Schizosaccharomyces pombe Rho GTPases regulate actin cytoskeleton organization and cell integrity. We studied the fission yeast gene SPBC4F6.12 based on its ability to suppress the thermosensitivity of cdc42-1625 mutant strain. This gene, named pxl1+, encodes a protein with three LIM domains that is similar to paxillin. Pxl1 does not interact with Cdc42 but it interacts with Rho1, and it negatively regulates this GTPase. Fission yeast Pxl1 forms a contractile ring in the cell division region and deletion of pxl1+ causes a delay in cell–cell separation, suggesting that it has a function in cytokinesis. Pxl1 N-terminal region is required and sufficient for its localization to the medial ring, whereas the LIM domains are necessary for its function. Pxl1 localization requires actin polymerization and the actomyosin ring, but it is independent of the septation initiation network (SIN) function. Moreover, Pxl1 colocalizes and interacts with Myo2, and Cdc15, suggesting that it is part of the actomyosin ring. Here, we show that in cells lacking Pxl1, the myosin ring is not correctly assembled and that actomyosin ring contraction is delayed. Together, these data suggest that Pxl1 modulates Rho1 GTPase signaling and plays a role in the formation and contraction of the actomyosin ring during cytokinesis.

scholarly journals Cooperation between Rho-GEF Gef2 and its binding partner Nod1 in the regulation of fission yeast cytokinesis

2013 ◽  
Vol 24 (20) ◽  
pp. 3187-3204 ◽  
Author(s):  
Yi-Hua Zhu ◽  
Yanfang Ye ◽  
Zhengrong Wu ◽  
Jian-Qiu Wu
Keyword(s):  
Fission Yeast ◽  
Rho Gtpases ◽  
Adaptor Protein ◽  
Nucleotide Exchange ◽  
Contractile Ring ◽  
Temporal Regulation ◽  
Division Site ◽  
Septation Initiation Network ◽  
Rho Gef

Cytokinesis is the last step of the cell-division cycle, which requires precise spatial and temporal regulation to ensure genetic stability. Rho guanine nucleotide exchange factors (Rho GEFs) and Rho GTPases are among the key regulators of cytokinesis. We previously found that putative Rho-GEF Gef2 coordinates with Polo kinase Plo1 to control the medial cortical localization of anillin-like protein Mid1 in fission yeast. Here we show that an adaptor protein, Nod1, colocalizes with Gef2 in the contractile ring and its precursor cortical nodes. Like gef2∆, nod1∆ has strong genetic interactions with various cytokinesis mutants involved in division-site positioning, suggesting a role of Nod1 in early cytokinesis. We find that Nod1 and Gef2 interact through the C-termini, which is important for their localization. The contractile-ring localization of Nod1 and Gef2 also depends on the interaction between Nod1 and the F-BAR protein Cdc15, where the Nod1/Gef2 complex plays a role in contractile-ring maintenance and affects the septation initiation network. Moreover, Gef2 binds to purified GTPases Rho1, Rho4, and Rho5 in vitro. Taken together, our data indicate that Nod1 and Gef2 function cooperatively in a protein complex to regulate fission yeast cytokinesis.

Flp1, a fission yeast orthologue of theS. cerevisiae CDC14gene, is not required for cyclin degradation or rum1p stabilisation at the end of mitosis

2001 ◽  
Vol 114 (14) ◽  
pp. 2649-2664 ◽  
Author(s):  
Nathalie Cueille ◽  
Ekaterina Salimova ◽  
Veronica Esteban ◽  
Miguel Blanco ◽  
Sergio Moreno ◽  
...  
Keyword(s):  
Fission Yeast ◽  
Kinase Inhibitor ◽  
Cell Cycle Control ◽  
Cyclin Dependent Kinase ◽  
Loss Of Function ◽  
Contractile Ring ◽  
Network Function ◽  
Cyclin Dependent Kinase Inhibitor ◽  
Septation Initiation Network ◽  
Specificity Factor

In Saccharomyces cerevisiae, the phosphoprotein phosphatase Cdc14p plays a central role in exit from mitosis, by promoting B-type cyclin degradation and allowing accumulation of the cyclin-dependent kinase inhibitor Sic1p. Cdc14p is sequestered in the nucleolus during interphase, from where it is released at the end of mitosis, dependent upon mitotic exit network function. The CDC14 gene is essential and loss-of-function mutants arrest at the end of mitosis. We have identified a fission yeast orthologue of CDC14 through database searches. A Schizosaccharomyces pombe flp1 (cdc fourteen-like-phosphatase) null mutant is viable, divides at a reduced size and shows defects in septation. flp1p is not the essential effector of the S. pombe septation initiation network, but may potentiate signalling of the onset of septation. In contrast to S. cerevisiae Cdc14p, flp1p is not required for the accumulation or destruction of the B-type cyclin cdc13p, the cyclin-dependent kinase inhibitor rum1p, or for dephosphorylation of the APC/C specificity factor ste9p in G1. Like its budding yeast counterpart, flp1p is restricted to the nucleolus until mitosis, when it is dispersed through the nucleus. In contrast to S. cerevisiae Cdc14p, flp1p is also present on the mitotic spindle and contractile ring. The potential roles of flp1p in cell cycle control are discussed.

Type 2 Diabetes Overtakes Type 1 in Hispanic Girls

2008 ◽  
Vol 38 (15) ◽  
pp. 18
Author(s):  
SHERRY BOSCHERT
Keyword(s):  
Type 2 Diabetes
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