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.

scholarly journals Assembly of normal actomyosin rings in the absence of Mid1p and cortical nodes in fission yeast

2008 ◽  
Vol 183 (6) ◽  
pp. 979-988 ◽  
Author(s):  
Yinyi Huang ◽  
Hongyan Yan ◽  
Mohan K. Balasubramanian
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Ring Structure ◽  
Contractile Ring ◽  
Ring Assembly ◽  
Cell Biol ◽  
In Cells

Cytokinesis in many eukaryotes depends on the function of an actomyosin contractile ring. The mechanisms regulating assembly and positioning of this ring are not fully understood. The fission yeast Schizosaccharomyces pombe divides using an actomyosin ring and is an attractive organism for the study of cytokinesis. Recent studies in S. pombe (Wu, J.Q., V. Sirotkin, D.R. Kovar, M. Lord, C.C. Beltzner, J.R. Kuhn, and T.D. Pollard. 2006. J. Cell Biol. 174:391–402; Vavylonis, D., J.Q. Wu, S. Hao, B. O'Shaughnessy, and T.D. Pollard. 2008. Science. 319:97–100) have suggested that the assembly of the actomyosin ring is initiated from a series of cortical nodes containing several components of this ring. These studies have proposed that actomyosin interactions bring together the cortical nodes to form a compacted ring structure. In this study, we test this model in cells that are unable to assemble cortical nodes. Although the cortical nodes play a role in the timing of ring assembly, we find that they are dispensable for the assembly of orthogonal actomyosin rings. Thus, a mechanism that is independent of cortical nodes is sufficient for the assembly of normal actomyosin rings.

scholarly journals Scw1p Antagonizes the Septation Initiation Network To Regulate Septum Formation and Cell Separation in the Fission Yeast Schizosaccharomyces pombe

2003 ◽  
Vol 2 (3) ◽  
pp. 510-520 ◽  
Author(s):  
Quan-Wen Jin ◽  
Dannel McCollum
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Cell Separation ◽  
Deletion Mutant ◽  
Temperature Sensitive ◽  
Growth Defects ◽  
Septum Formation ◽  
Primary Septum ◽  
Septation Initiation Network ◽  
Ring Constriction

ABSTRACT Cytokinesis in the fission yeast Schizosaccharomyces pombe is regulated by a signaling pathway termed the septation initiation network (SIN). The SIN is essential for initiation of actomyosin ring constriction and septum formation. In a screen to search for mutations that can rescue the sid2-250 SIN mutant, we obtained scw1-18. Both the scw1-18 mutant and the scw1 deletion mutant (scw1Δ mutant), have defects in cell separation. Both the scw1-18 and scw1Δ mutations rescue the growth defects of not just the sid2-250 mutant but also the other temperature-sensitive SIN mutants. Other cytokinesis mutants, such as those defective for actomyosin ring formation, are not rescued by scw1Δ. scw1Δ does not seem to rescue the SIN by restoring SIN signaling defects. However, scw1Δ may function downstream of the SIN to promote septum formation, since scw1Δ can rescue the septum formation defects of the cps1-191β-1,3-glucan synthase mutant, which is required for synthesis of the primary septum.

scholarly journals Roles of putative Rho-GEF Gef2 in division-site positioning and contractile-ring function in fission yeast cytokinesis

2012 ◽  
Vol 23 (7) ◽  
pp. 1181-1195 ◽  
Author(s):  
Yanfang Ye ◽  
I-Ju Lee ◽  
Kurt W. Runge ◽  
Jian-Qiu Wu
Keyword(s):  
Fission Yeast ◽  
Rho Gtpases ◽  
Nucleotide Exchange ◽  
Contractile Ring ◽  
Division Plane ◽  
Cell Functions ◽  
Division Site ◽  
Ring Assembly ◽  
And Function ◽  
Rho Gef

Cytokinesis is crucial for integrating genome inheritance and cell functions. In multicellular organisms, Rho-guanine nucleotide exchange factors (GEFs) and Rho GTPases are key regulators of division-plane specification and contractile-ring formation during cytokinesis, but how they regulate early steps of cytokinesis in fission yeast remains largely unknown. Here we show that putative Rho-GEF Gef2 and Polo kinase Plo1 coordinate to control the medial cortical localization and function of anillin-related protein Mid1. The division-site positioning defects of gef2∆ plo1-ts18 double mutant can be partially rescued by increasing Mid1 levels. We find that Gef2 physically interacts with the Mid1 N-terminus and modulates Mid1 cortical binding. Gef2 localization to cortical nodes and the contractile ring depends on its last 145 residues, and the DBL-homology domain is important for its function in cytokinesis. Our data suggest the interaction between Rho-GEFs and anillins is an important step in the signaling pathways during cytokinesis. In addition, Gef2 also regulates contractile-ring function late in cytokinesis and may negatively regulate the septation initiation network. Collectively, we propose that Gef2 facilitates and stabilizes Mid1 binding to the medial cortex, where the localized Mid1 specifies the division site and induces contractile-ring assembly.

scholarly journals Fission yeast Cyk3p is a transglutaminase-like protein that participates in cytokinesis and cell morphogenesis

2012 ◽  
Vol 23 (13) ◽  
pp. 2433-2444 ◽  
Author(s):  
Luther W. Pollard ◽  
Masayuki Onishi ◽  
John R. Pringle ◽  
Matthew Lord
Keyword(s):  
Fission Yeast ◽  
Primary Role ◽  
Cell Integrity ◽  
Cell Morphogenesis ◽  
Contractile Ring ◽  
Physiological Importance ◽  
Complex Process ◽  
Catalytic Active Site ◽  
Thiol Proteases ◽  
Ring Constriction

Cell morphogenesis is a complex process that relies on a diverse array of proteins and pathways. We have identified a transglutaminase-like protein (Cyk3p) that functions in fission yeast morphogenesis. The phenotype of a cyk3 knockout strain indicates a primary role for Cyk3p in cytokinesis. Correspondingly, Cyk3p localizes both to the actomyosin contractile ring and the division septum, promoting ring constriction, septation, and subsequent cell separation following ring disassembly. In addition, Cyk3p localizes to polarized growth sites and plays a role in cell shape determination, and it also appears to contribute to cell integrity during stationary phase, given its accumulation as dynamic puncta at the cortex of such cells. Our results and the conservation of Cyk3p across fungi point to a role in cell wall synthesis and remodeling. Cyk3p possesses a transglutaminase domain that is essential for function, even though it lacks the catalytic active site. In a wider sense, our work illustrates the physiological importance of inactive members of the transglutaminase family, which are found throughout eukaryotes. We suggest that the proposed evolution of animal transglutaminase cross-linking activity from ancestral bacterial thiol proteases was accompanied by the emergence of a subclass whose function does not depend on enzymatic activity.

scholarly journals A Link between Aurora Kinase and Clp1/Cdc14 Regulation Uncovered by the Identification of a Fission Yeast Borealin-Like Protein

2009 ◽  
Vol 20 (16) ◽  
pp. 3646-3659 ◽  
Author(s):  
K. Adam Bohnert ◽  
Jun-Song Chen ◽  
Dawn M. Clifford ◽  
Craig W. Vander Kooi ◽  
Kathleen L. Gould
Keyword(s):  
Cell Division ◽  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Kinase Activity ◽  
Sequence Similarity ◽  
Aurora Kinase ◽  
Genetic Interactions ◽  
Aurora B ◽  
Contractile Ring ◽  
Chromosomal Passenger

The chromosomal passenger complex (CPC) regulates various events in cell division. This complex is composed of a catalytic subunit, Aurora B kinase, and three nonenzymatic subunits, INCENP, Survivin, and Borealin. Together, these four subunits interdependently regulate CPC function, and they are highly conserved among eukaryotes. However, a Borealin homologue has never been characterized in the fission yeast, Schizosaccharomyces pombe . Here, we isolate a previously uncharacterized S. pombe protein through association with the Cdc14 phosphatase homologue, Clp1/Flp1, and identify it as a Borealin-like member of the CPC. Nbl1 (novel Borealin-like 1) physically associates with known CPC components, affects the kinase activity and stability of the S. pombe Aurora B homologue, Ark1, colocalizes with known CPC subunits during mitosis, and shows sequence similarity to human Borealin. Further analysis of the Clp1–Nbl1 interaction indicates that Clp1 requires CPC activity for proper accumulation at the contractile ring (CR). Consistent with this, we describe negative genetic interactions between mutant alleles of CPC and CR components. Thus, this study characterizes a fission yeast Borealin homologue and reveals a previously unrecognized connection between the CPC and the process of cytokinesis in S. pombe .

scholarly journals Role of Tropomyosin in Formin-mediated Contractile Ring Assembly in Fission Yeast

2009 ◽  
Vol 20 (8) ◽  
pp. 2160-2173 ◽  
Author(s):  
Colleen T. Skau ◽  
Erin M. Neidt ◽  
David R. Kovar
Keyword(s):  
Fission Yeast ◽  
Actin Filament ◽  
Actin Filaments ◽  
Actin Polymerization ◽  
Actin Assembly ◽  
Animal Cells ◽  
Contractile Ring ◽  
Direct Role ◽  
Ring Assembly

Like animal cells, fission yeast divides by assembling actin filaments into a contractile ring. In addition to formin Cdc12p and profilin, the single tropomyosin isoform SpTm is required for contractile ring assembly. Cdc12p nucleates actin filaments and remains processively associated with the elongating barbed end while driving the addition of profilin-actin. SpTm is thought to stabilize mature filaments, but it is not known how SpTm localizes to the contractile ring and whether SpTm plays a direct role in Cdc12p-mediated actin polymerization. Using “bulk” and single actin filament assays, we discovered that Cdc12p can recruit SpTm to actin filaments and that SpTm has diverse effects on Cdc12p-mediated actin assembly. On its own, SpTm inhibits actin filament elongation and depolymerization. However, Cdc12p completely overcomes the combined inhibition of actin nucleation and barbed end elongation by profilin and SpTm. Furthermore, SpTm increases the length of Cdc12p-nucleated actin filaments by enhancing the elongation rate twofold and by allowing them to anneal end to end. In contrast, SpTm ultimately turns off Cdc12p-mediated elongation by “trapping” Cdc12p within annealed filaments or by dissociating Cdc12p from the barbed end. Therefore, SpTm makes multiple contributions to contractile ring assembly during and after actin polymerization.

An overview of the fission yeast septation initiation network (SIN)

2008 ◽  
Vol 36 (3) ◽  
pp. 411-415 ◽  
Author(s):  
Andrea Krapp ◽  
Viesturs Simanis
Keyword(s):  
Cell Cycle ◽  
Signal Transduction ◽  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Protein Kinases ◽  
Signal Transduction Network ◽  
Septum Formation ◽  
Ras Superfamily ◽  
Septation Initiation Network

The fission yeast septation initiation network, or SIN, is a signal transduction network that is required for septum formation in Schizosaccharomyces pombe. Its activity is tightly regulated through the cell cycle, to ensure proper co-ordination of mitosis and cytokinesis. SIN signalling requires three protein kinases for its function and is mediated by a ras-superfamily GTPase. We discuss the elements of the SIN and how they are regulated.

scholarly journals A SAC phosphoinositide phosphatase controls rice development via hydrolyzing phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate

2019 ◽  
Author(s):  
Tao Guo ◽  
Hua-Chang Chen ◽  
Zi-Qi Lu ◽  
Min Diao ◽  
Ke Chen ◽  
...  
Keyword(s):  
Actin Polymerization ◽  
Membrane Lipids ◽  
Dependent Manner ◽  
Cytoskeleton Organization ◽  
Cellular Processes ◽  
Phosphoinositide Phosphatase ◽  
Actin Cytoskeleton Organization ◽  
Phosphatidylinositol 4 ◽  
Related Proteins

AbstractPhosphoinositides (PIs) as regulatory membrane lipids play essential roles in multiple cellular processes. Although the exact molecular targets of PIs-dependent modulation remain largely elusive, the effects of disturbed PIs metabolism could be employed to propose regulatory modules associated with particular downstream targets of PIs. Here, we identified the role of GRAIN NUMBER AND PLANT HEIGHT 1 (GH1), which encodes a suppressor of actin (SAC) domain-containing phosphatase with unknown function in rice. Endoplasmic reticulum-localized GH1 specifically dephosphorylated and hydrolyzed phosphatidylinositol 4-phosphate (PI4P) and phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2]. Inactivation of GH1 resulted in massive accumulation of both PI4P and PI(4,5)P2, while excessive GH1 caused their depletion. Notably, superabundant PI4P and PI(4,5)P2 could both disrupt actin cytoskeleton organization and suppress cell elongation. Interestingly, both PI4P and PI(4,5)P2 inhibited actin-related proteins 2 and 3 (Arp2/3) complex-nucleated actin branching networks in vitro, whereas PI(4,5)P2 showed more dramatic effect in a dose-dependent manner. Overall, the overaccumulation of PI(4,5)P2 resulted from dysfunction of SAC phosphatase possibly perturbs Arp2/3 complex-mediated actin polymerization, thereby disordering the cell development. These findings imply that Arp2/3 complex might be the potential molecular target of PI(4,5)P2-dependent modulation in eukaryotes, thereby providing new insights into the relationship between PIs homeostasis and plants growth and development.

scholarly journals Analysis of the contribution of phosphoinositides to medial septation in fission yeast highlights the importance of PI(4,5)P2 for medial contractile ring anchoring

2018 ◽  
Vol 29 (18) ◽  
pp. 2148-2155 ◽  
Author(s):  
Chloe E. Snider ◽  
Alaina H. Willet ◽  
HannahSofia T. Brown ◽  
Kathleen L. Gould
Keyword(s):  
Plasma Membrane ◽  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Specific Role ◽  
Elevated Plasma ◽  
Contractile Ring ◽  
Nuclear Position

In Schizosaccharomyces pombe, loss of the plasma membrane PI4-kinase scaffold Efr3 leads to sliding of the cytokinetic ring (CR) away from the cell center during anaphase, implicating phosphoinositides (PIPs) in CR anchoring. However, whether other PIP regulators contribute to CR anchoring has not been investigated. Here we report that mutants of other PIP kinases and their regulators divide with off-center septa, similar to efr3∆. Using new biosensors for S. pombe PIPs, we confirm that these mutants have disrupted PIP composition. We extend a previous finding that a mutant known to decrease PI(3,5)P2 levels indirectly affects CR positioning by increasing vacuole size which disrupts nuclear position at the onset of mitosis. Indeed, we found that other mutants with increased vacuole size also disrupt medial division via this mechanism. Although elevated plasma membrane PI(4,5)P2 levels do not affect medial cytokinesis, mutants with decreased levels display CR sliding events indicating a specific role for PI(4,5)P2 in CR anchoring.

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