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 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 Regulation of Rho-GEF Rgf3 by the arrestin Art1 in fission yeast cytokinesis

2015 ◽  
Vol 26 (3) ◽  
pp. 453-466 ◽  
Author(s):  
Reshma Davidson ◽  
Damien Laporte ◽  
Jian-Qiu Wu
Keyword(s):  
Fission Yeast ◽  
Rho Gtpases ◽  
Nucleotide Exchange ◽  
Protein Levels ◽  
Cellular Processes ◽  
Division Site ◽  
Guanine Nucleotide Exchange ◽  
C Terminus ◽  
Early Anaphase ◽  
Rho Gef

Rho GTPases, activated by guanine nucleotide exchange factors (GEFs), are essential regulators of polarized cell growth, cytokinesis, and many other cellular processes. However, the regulation of Rho-GEFs themselves is not well understood. Rgf3 is an essential GEF for Rho1 GTPase in fission yeast. We show that Rgf3 protein levels and localization are regulated by arrestin-related protein Art1. art1∆ cells lyse during cell separation with a thinner and defective septum. As does Rgf3, Art1 concentrates to the contractile ring starting at early anaphase and spreads to the septum during and after ring constriction. Art1 localization depends on its C-terminus, and Art1 is important for maintaining Rgf3 protein levels. Biochemical experiments reveal that the Rgf3 C-terminus binds to Art1. Using an Rgf3 conditional mutant and mislocalization experiments, we found that Art1 and Rgf3 are interdependent for localization to the division site. As expected, active Rho1 levels at the division site are reduced in art1∆ and rgf3 mutant cells. Taken together, these data reveal that the arrestin family protein Art1 regulates the protein levels and localization of the Rho-GEF Rgf3, which in turn modulates active Rho1 levels during fission yeast cytokinesis.

scholarly journals Roles of the novel coiled-coil protein Rng10 in septum formation during fission yeast cytokinesis

2016 ◽  
Vol 27 (16) ◽  
pp. 2528-2541 ◽  
Author(s):  
Yajun Liu ◽  
I-Ju Lee ◽  
Mingzhai Sun ◽  
Casey A. Lower ◽  
Kurt W. Runge ◽  
...  
Keyword(s):  
Fission Yeast ◽  
Rho Gtpases ◽  
Cellular Localization ◽  
Affinity Purification ◽  
Coiled Coil ◽  
The Novel ◽  
Septum Formation ◽  
Division Site ◽  
And Function

Rho GAPs are important regulators of Rho GTPases, which are involved in various steps of cytokinesis and other processes. However, regulation of Rho-GAP cellular localization and function is not fully understood. Here we report the characterization of a novel coiled-coil protein Rng10 and its relationship with the Rho-GAP Rga7 in fission yeast. Both rng10Δ and rga7Δ result in defective septum and cell lysis during cytokinesis. Rng10 and Rga7 colocalize on the plasma membrane at the cell tips during interphase and at the division site during cell division. Rng10 physically interacts with Rga7 in affinity purification and coimmunoprecipitation. Of interest, Rga7 localization is nearly abolished without Rng10. Moreover, Rng10 and Rga7 work together to regulate the accumulation and dynamics of glucan synthases for successful septum formation in cytokinesis. Our results show that cellular localization and function of the Rho-GAP Rga7 are regulated by a novel protein, Rng10, during cytokinesis in fission yeast.

scholarly journals An ECT2–centralspindlin complex regulates the localization and function of RhoA

2005 ◽  
Vol 170 (4) ◽  
pp. 571-582 ◽  
Author(s):  
Özlem Yüce ◽  
Alisa Piekny ◽  
Michael Glotzer
Keyword(s):  
Actin Polymerization ◽  
Molecular Mechanisms ◽  
Myosin Ii ◽  
Cell Cortex ◽  
Contractile Ring ◽  
Division Plane ◽  
Central Spindle ◽  
Ring Assembly ◽  
Cortical Localization ◽  
And Function

In anaphase, the spindle dictates the site of contractile ring assembly. Assembly and ingression of the contractile ring involves activation of myosin-II and actin polymerization, which are triggered by the GTPase RhoA. In many cells, the central spindle affects division plane positioning via unknown molecular mechanisms. Here, we dissect furrow formation in human cells and show that the RhoGEF ECT2 is required for cortical localization of RhoA and contractile ring assembly. ECT2 concentrates on the central spindle by binding to centralspindlin. Depletion of the centralspindlin component MKLP1 prevents central spindle localization of ECT2; however, RhoA, F-actin, and myosin still accumulate on the equatorial cell cortex. Depletion of the other centralspindlin component, CYK-4/MgcRacGAP, prevents cortical accumulation of RhoA, F-actin, and myosin. CYK-4 and ECT2 interact, and this interaction is cell cycle regulated via ECT2 phosphorylation. Thus, central spindle localization of ECT2 assists division plane positioning and the CYK-4 subunit of centralspindlin acts upstream of RhoA to promote furrow assembly.

scholarly journals The Rho-GEF Gef3 interacts with the septin complex and activates the GTPase Rho4 during fission yeast cytokinesis

2015 ◽  
Vol 26 (2) ◽  
pp. 238-255 ◽  
Author(s):  
Ning Wang ◽  
Mo Wang ◽  
Yi-Hua Zhu ◽  
Timothy W. Grosel ◽  
Daokun Sun ◽  
...  
Keyword(s):  
Fission Yeast ◽  
Rho Gtpases ◽  
Cell Polarization ◽  
Nucleotide Exchange ◽  
Cellular Processes ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factors ◽  
Rho Gef

Rho GTPases, activated by Rho guanine nucleotide exchange factors (GEFs), are conserved molecular switches for signal transductions that regulate diverse cellular processes, including cell polarization and cytokinesis. The fission yeast Schizosaccharomyces pombe has six Rho GTPases (Cdc42 and Rho1–Rho5) and seven Rho GEFs (Scd1, Rgf1–Rgf3, and Gef1–Gef3). The GEFs for Rho2–Rho5 have not been unequivocally assigned. In particular, Gef3, the smallest Rho GEF, was barely studied. Here we show that Gef3 colocalizes with septins at the cell equator. Gef3 physically interacts with septins and anillin Mid2 and depends on them to localize. Gef3 coprecipitates with GDP-bound Rho4 in vitro and accelerates nucleotide exchange of Rho4, suggesting that Gef3 is a GEF for Rho4. Consistently, Gef3 and Rho4 are in the same genetic pathways to regulate septum formation and/or cell separation. In gef3∆ cells, the localizations of two potential Rho4 effectors—glucanases Eng1 and Agn1—are abnormal, and active Rho4 level is reduced, indicating that Gef3 is involved in Rho4 activation in vivo. Moreover, overexpression of active Rho4 or Eng1 rescues the septation defects of mutants containing gef3∆. Together our data support that Gef3 interacts with the septin complex and activates Rho4 GTPase as a Rho GEF for septation in fission yeast.

scholarly journals The formins Cdc12 and For3 cooperate during contractile ring assembly in cytokinesis

2013 ◽  
Vol 203 (1) ◽  
pp. 101-114 ◽  
Author(s):  
Valerie C. Coffman ◽  
Jennifer A. Sees ◽  
David R. Kovar ◽  
Jian-Qiu Wu
Keyword(s):  
Fluorescence Microscopy ◽  
Fission Yeast ◽  
Actin Filaments ◽  
De Novo ◽  
Ring Formation ◽  
Actin Assembly ◽  
Contractile Ring ◽  
Synthetic Lethal ◽  
Division Site ◽  
Ring Assembly

Both de novo–assembled actin filaments at the division site and existing filaments recruited by directional cortical transport contribute to contractile ring formation during cytokinesis. However, it is unknown which source is more important. Here, we show that fission yeast formin For3 is responsible for node condensation into clumps in the absence of formin Cdc12. For3 localization at the division site depended on the F-BAR protein Cdc15, and for3 deletion was synthetic lethal with mutations that cause defects in contractile ring formation. For3 became essential in cells expressing N-terminal truncations of Cdc12, which were more active in actin assembly but depended on actin filaments for localization to the division site. In tetrad fluorescence microscopy, double mutants of for3 deletion and cdc12 truncations were severely defective in contractile ring assembly and constriction, although cortical transport of actin filaments was normal. Together, these data indicate that different formins cooperate in cytokinesis and that de novo actin assembly at the division site is predominant for contractile ring formation.

scholarly journals Myosin-II reorganization during mitosis is controlled temporally by its dephosphorylation and spatially by Mid1 in fission yeast

2004 ◽  
Vol 165 (5) ◽  
pp. 685-695 ◽  
Author(s):  
Fumio Motegi ◽  
Mithilesh Mishra ◽  
Mohan K. Balasubramanian ◽  
Issei Mabuchi
Keyword(s):  
Fission Yeast ◽  
Myosin Ii ◽  
Phosphorylation Site ◽  
Terminal Region ◽  
Contractile Ring ◽  
Actin Ring ◽  
Division Site ◽  
Ring Assembly ◽  
Medial Cortex ◽  
Early Mitosis

Cytokinesis in many eukaryotes requires an actomyosin contractile ring. Here, we show that in fission yeast the myosin-II heavy chain Myo2 initially accumulates at the division site via its COOH-terminal 134 amino acids independently of F-actin. The COOH-terminal region can access to the division site at early G2, whereas intact Myo2 does so at early mitosis. Ser1444 in the Myo2 COOH-terminal region is a phosphorylation site that is dephosphorylated during early mitosis. Myo2 S1444A prematurely accumulates at the future division site and promotes formation of an F-actin ring even during interphase. The accumulation of Myo2 requires the anillin homologue Mid1 that functions in proper ring placement. Myo2 interacts with Mid1 in cell lysates, and this interaction is inhibited by an S1444D mutation in Myo2. Our results suggest that dephosphorylation of Myo2 liberates the COOH-terminal region from an intramolecular inhibition. Subsequently, dephosphorylated Myo2 is anchored by Mid1 at the medial cortex and promotes the ring assembly in cooperation with F-actin.

scholarly journals A single-headed fission yeast myosin V transports actin in a tropomyosin-dependent manner

2016 ◽  
Vol 214 (2) ◽  
pp. 167-179 ◽  
Author(s):  
Qing Tang ◽  
Neil Billington ◽  
Elena B. Krementsova ◽  
Carol S. Bookwalter ◽  
Matthew Lord ◽  
...  
Keyword(s):  
Fission Yeast ◽  
Cellular Localization ◽  
Dependent Manner ◽  
Myosin V ◽  
Contractile Ring ◽  
Class V ◽  
Ring Assembly ◽  
Attachment Sites ◽  
And Function

Myo51, a class V myosin in fission yeast, localizes to and assists in the assembly of the contractile ring, a conserved eukaryotic actomyosin structure that facilitates cytokinesis. Rng8 and Rng9 are binding partners that dictate the cellular localization and function of Myo51. Myo51 was expressed in insect cells in the presence or absence of Rng8/9. Surprisingly, electron microscopy of negatively stained images and hydrodynamic measurements showed that Myo51 is single headed, unlike most class V myosins. When Myo51–Rng8/9 was bound to actin-tropomyosin, two attachment sites were observed: the typical ATP-dependent motor domain attachment and a novel ATP-independent binding of the tail mediated by Rng8/9. A modified motility assay showed that this additional binding site anchors Myo51–Rng8/9 so that it can cross-link and slide actin-tropomyosin filaments relative to one another, functions that may explain the role of this motor in contractile ring assembly.

scholarly journals Calcium spikes accompany cleavage furrow ingression and cell separation during fission yeast cytokinesis

2021 ◽  
Vol 32 (1) ◽  
pp. 15-27 ◽  
Author(s):  
Abhishek Poddar ◽  
Oumou Sidibe ◽  
Aniruddha Ray ◽  
Qian Chen
Keyword(s):  
Fission Yeast ◽  
Cell Separation ◽  
Cleavage Furrow ◽  
Cell Integrity ◽  
Embryonic Cells ◽  
Contractile Ring ◽  
Calcium Spikes ◽  
Division Plane ◽  
Ring Constriction ◽  
And Function

Calcium rises transiently at the division plane during cytokinesis of embryonic cells, but the conservation and function of such calcium transients remain unclear. We discovered similar calcium spikes during fission yeast cytokinesis, and demonstrated that calcium promotes contractile ring constriction and daughter cell integrity.

scholarly journals The Multiple Functions of Rho GTPases in Fission Yeasts

Cells ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 1422
Author(s):  
Jero Vicente-Soler ◽  
Teresa Soto ◽  
Alejandro Franco ◽  
José Cansado ◽  
Marisa Madrid
Keyword(s):  
Fission Yeast ◽  
Rho Gtpases ◽  
Current Knowledge ◽  
Model Organism ◽  
Nucleotide Exchange ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factors ◽  
Physiological Processes ◽  
Evolutionary Changes ◽  
Rho Family

The Rho family of GTPases represents highly conserved molecular switches involved in a plethora of physiological processes. Fission yeast Schizosaccharomyces pombe has become a fundamental model organism to study the functions of Rho GTPases over the past few decades. In recent years, another fission yeast species, Schizosaccharomyces japonicus, has come into focus offering insight into evolutionary changes within the genus. Both fission yeasts contain only six Rho-type GTPases that are spatiotemporally controlled by multiple guanine–nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs), and whose intricate regulation in response to external cues is starting to be uncovered. In the present review, we will outline and discuss the current knowledge and recent advances on how the fission yeasts Rho family GTPases regulate essential physiological processes such as morphogenesis and polarity, cellular integrity, cytokinesis and cellular differentiation.

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