scholarly journals Immobile myosin-II plays a scaffolding role during cytokinesis in budding yeast

2013 ◽  
Vol 200 (3) ◽  
pp. 271-286 ◽  
Author(s):  
Carsten Wloka ◽  
Elizabeth A. Vallen ◽  
Lydia Thé ◽  
Xiaodong Fang ◽  
Younghoon Oh ◽  
...  
Keyword(s):  
Membrane Trafficking ◽  
Budding Yeast ◽  
Myosin Ii ◽  
Small Region ◽  
Myosin V ◽  
Actin Ring ◽  
Essential Light Chain ◽  
Division Site ◽  
Ring Assembly ◽  
Core Components

Core components of cytokinesis are conserved from yeast to human, but how these components are assembled into a robust machine that drives cytokinesis remains poorly understood. In this paper, we show by fluorescence recovery after photobleaching analysis that Myo1, the sole myosin-II in budding yeast, was mobile at the division site before anaphase and became immobilized shortly before cytokinesis. This immobility was independent of actin filaments or the motor domain of Myo1 but required a small region in the Myo1 tail that is thought to be involved in higher-order assembly. As expected, proteins involved in actin ring assembly (tropomyosin and formin) and membrane trafficking (myosin-V and exocyst) were dynamic during cytokinesis. Strikingly, proteins involved in septum formation (the chitin synthase Chs2) and/or its coordination with the actomyosin ring (essential light chain, IQGAP, F-BAR, etc.) displayed Myo1-dependent immobility during cytokinesis, suggesting that Myo1 plays a scaffolding role in the assembly of a cytokinesis machine.

scholarly journals Myosin‑II heavy chain and formin mediate the targeting of myosin essential light chain to the division site before and during cytokinesis

2015 ◽  
Vol 26 (7) ◽  
pp. 1211-1224 ◽  
Author(s):  
Zhonghui Feng ◽  
Satoshi Okada ◽  
Guoping Cai ◽  
Bing Zhou ◽  
Erfei Bi
Keyword(s):  
Heavy Chain ◽  
Light Chain ◽  
Membrane Trafficking ◽  
Myosin Ii ◽  
Myosin V ◽  
Gene Encoding ◽  
Yeast Saccharomyces Cerevisiae ◽  
Essential Light Chain ◽  
Division Site ◽  
Yeast Mutants

MLC1 is a haploinsufficient gene encoding the essential light chain for Myo1, the sole myosin‑II heavy chain in the budding yeast Saccharomyces cerevisiae. Mlc1 defines an essential hub that coordinates actomyosin ring function, membrane trafficking, and septum formation during cytokinesis by binding to IQGAP, myosin‑II, and myosin‑V. However, the mechanism of how Mlc1 is targeted to the division site during the cell cycle remains unsolved. By constructing a GFP‑tagged MLC1 under its own promoter control and using quantitative live‑cell imaging coupled with yeast mutants, we found that septin ring and actin filaments mediate the targeting of Mlc1 to the division site before and during cytokinesis, respectively. Both mechanisms contribute to and are collectively required for the accumulation of Mlc1 at the division site during cytokinesis. We also found that Myo1 plays a major role in the septin‑dependent Mlc1 localization before cytokinesis, whereas the formin Bni1 plays a major role in the actin filament–dependent Mlc1 localization during cytokinesis. Such a two‑tiered mechanism for Mlc1 localization is presumably required for the ordered assembly and robustness of cytokinesis machinery and is likely conserved across species.

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 The Actomyosin Ring Recruits Early Secretory Compartments to the Division Site in Fission Yeast

2008 ◽  
Vol 19 (3) ◽  
pp. 1125-1138 ◽  
Author(s):  
Aleksandar Vjestica ◽  
Xin-Zi Tang ◽  
Snezhana Oliferenko
Keyword(s):  
Endoplasmic Reticulum ◽  
Fission Yeast ◽  
Membrane Trafficking ◽  
Secretory Pathway ◽  
Physical Force ◽  
Daughter Cells ◽  
Division Site ◽  
Ring Assembly ◽  
Membrane Barrier ◽  
Ring Constriction

The ultimate goal of cytokinesis is to establish a membrane barrier between daughter cells. The fission yeast Schizosaccharomyces pombe utilizes an actomyosin-based division ring that is thought to provide physical force for the plasma membrane invagination. Ring constriction occurs concomitantly with the assembly of a division septum that is eventually cleaved. Membrane trafficking events such as targeting of secretory vesicles to the division site require a functional actomyosin ring suggesting that it serves as a spatial landmark. However, the extent of polarization of the secretion apparatus to the division site is presently unknown. We performed a survey of dynamics of several fluorophore-tagged proteins that served as markers for various compartments of the secretory pathway. These included markers for the endoplasmic reticulum, the COPII sites, and the early and late Golgi. The secretion machinery exhibited a marked polarization to the division site. Specifically, we observed an enrichment of the transitional endoplasmic reticulum (tER) accompanied by Golgi cisternae biogenesis. These processes required actomyosin ring assembly and the function of the EFC-domain protein Cdc15p. Cdc15p overexpression was sufficient to induce tER polarization in interphase. Thus, fission yeast polarizes its entire secretory machinery to the cell division site by utilizing molecular cues provided by the actomyosin ring.

scholarly journals Rho1 Directs Formin-Mediated Actin Ring Assembly during Budding Yeast Cytokinesis

2002 ◽  
Vol 12 (21) ◽  
pp. 1864-1870 ◽  
Author(s):  
Nicola Tolliday ◽  
Lynn VerPlank ◽  
Rong Li
Keyword(s):  
Budding Yeast ◽  
Actin Ring ◽  
Ring Assembly

scholarly journals Molecular mechanism of myosin-II assembly at the division site in Schizosaccharomyces pombe

2000 ◽  
Vol 113 (10) ◽  
pp. 1813-1825 ◽  
Author(s):  
F. Motegi ◽  
K. Nakano ◽  
I. Mabuchi
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Myosin Ii ◽  
Loss Of Function ◽  
Contractile Ring ◽  
Actin Ring ◽  
Medial Region ◽  
Division Site ◽  
Medial Cortex ◽  
Actin Cables ◽  
Mutant Cells

Schizosaccharomyces pombe cells divide by virtue of the F-actin-based contractile ring (F-actin ring). Two myosin-II heavy chains, Myo2 and Myp2/Myo3, have been localized to the F-actin ring. Here, we investigated the mechanism of myosin-II assembly at the division site in S. pombe cells. First, we showed that Cdc4, an EF-hand protein, appears to be a common myosin light chain associated with both Myo2 and Myo3. Loss of function of both Myo2 and Myo3 caused a defect in F-actin assembly at the division site, like the phenotype of cdc4 null cells. It is suggested that Myo2, Myo3 and Cdc4 function in a cooperative manner in the formation of the F-actin ring during mitosis. Next, we investigated the dynamics of myosin-II during mitosis in S. pombe cells. In early mitosis when accumulation of F-actin cables in the medial region was not yet observed, Myo2 was detected primarily as dots widely located in the medial cortex. Myo2 fibers also became visible following the appearance of the dots. The Myo2 dots and fibers then fused with each other to form a medial cortical network. Some Myo2 dots appeared to be localized with F-actin cables which are also accumulated in the medial region. Finally these structures were packed into a thin contractile ring. In mutant cells that cannot form the F-actin ring such as cdc3(ts), cdc8(ts) and cdc12(ts), Myo2 was able to accumulate as dots in the medial cortex, whereas no accumulation of Myo2 dots was detected in cdc4(ts) cells. Moreover, disruption of F-actin in the cell by applying latrunculin-A did not affect the accumulation of Myo2 dots, suggesting that F-actin is not required for their accumulation. A truncated Myo2 which lacks putative Cdc4-binding sites (Myo2dIQs) was able to rescue myo2 null cells, myo3 null cells, cdc4(ts) mutant cells and cdc4 null cells. The Myo2dIQs could assemble into a normal-shaped ring in these cells. Therefore, its assembly at the division site does not require the function of either Cdc4 or Myo3.

scholarly journals Biphasic targeting and cleavage furrow ingression directed by the tail of a myosin II

2010 ◽  
Vol 191 (7) ◽  
pp. 1333-1350 ◽  
Author(s):  
Xiaodong Fang ◽  
Jianying Luo ◽  
Ryuichi Nishihama ◽  
Carsten Wloka ◽  
Christopher Dravis ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Membrane Trafficking ◽  
Myosin Ii ◽  
Force Generation ◽  
Extracellular Matrix Remodeling ◽  
Cleavage Furrow ◽  
Matrix Remodeling ◽  
Division Site ◽  
Targeting Signals

Cytokinesis in animal and fungal cells utilizes a contractile actomyosin ring (AMR). However, how myosin II is targeted to the division site and promotes AMR assembly, and how the AMR coordinates with membrane trafficking during cytokinesis, remains poorly understood. Here we show that Myo1 is a two-headed myosin II in Saccharomyces cerevisiae, and that Myo1 localizes to the division site via two distinct targeting signals in its tail that act sequentially during the cell cycle. Before cytokinesis, Myo1 localization depends on the septin-binding protein Bni5. During cytokinesis, Myo1 localization depends on the IQGAP Iqg1. We also show that the Myo1 tail is sufficient for promoting the assembly of a “headless” AMR, which guides membrane deposition and extracellular matrix remodeling at the division site. Our study establishes a biphasic targeting mechanism for myosin II and highlights an underappreciated role of the AMR in cytokinesis beyond force generation.

scholarly journals Nonmedially assembled F-actin cables incorporate into the actomyosin ring in fission yeast

2012 ◽  
Vol 199 (5) ◽  
pp. 831-847 ◽  
Author(s):  
Junqi Huang ◽  
Yinyi Huang ◽  
Haochen Yu ◽  
Dhivya Subramanian ◽  
Anup Padmanabhan ◽  
...  
Keyword(s):  
De Novo ◽  
Actin Dynamics ◽  
Actin Assembly ◽  
Animal Cells ◽  
Myosin V ◽  
Contractile Ring ◽  
Division Site ◽  
Ring Assembly ◽  
Actin Cables

In many eukaryotes, cytokinesis requires the assembly and constriction of an actomyosin-based contractile ring. Despite the central role of this ring in cytokinesis, the mechanism of F-actin assembly and accumulation in the ring is not fully understood. In this paper, we investigate the mechanism of F-actin assembly during cytokinesis in Schizosaccharomyces pombe using lifeact as a probe to monitor actin dynamics. Previous work has shown that F-actin in the actomyosin ring is assembled de novo at the division site. Surprisingly, we find that a significant fraction of F-actin in the ring was recruited from formin-Cdc12p nucleated long actin cables that were generated at multiple nonmedial locations and incorporated into the ring by a combination of myosin II and myosin V activities. Our results, together with findings in animal cells, suggest that de novo F-actin assembly at the division site and directed transport of F-actin cables assembled elsewhere can contribute to ring assembly.

scholarly journals The novel proteins Rng8 and Rng9 regulate the myosin-V Myo51 during fission yeast cytokinesis

2014 ◽  
Vol 205 (3) ◽  
pp. 357-375 ◽  
Author(s):  
Ning Wang ◽  
Libera Lo Presti ◽  
Yi-Hua Zhu ◽  
Minhee Kang ◽  
Zhengrong Wu ◽  
...  
Keyword(s):  
Fission Yeast ◽  
Molecular Motors ◽  
Coiled Coil ◽  
Myosin V ◽  
Contractile Ring ◽  
Novel Proteins ◽  
Ring Assembly ◽  
Actin Cables ◽  
Order Complexes

The myosin-V family of molecular motors is known to be under sophisticated regulation, but our knowledge of the roles and regulation of myosin-Vs in cytokinesis is limited. Here, we report that the myosin-V Myo51 affects contractile ring assembly and stability during fission yeast cytokinesis, and is regulated by two novel coiled-coil proteins, Rng8 and Rng9. Both rng8Δ and rng9Δ cells display similar defects as myo51Δ in cytokinesis. Rng8 and Rng9 are required for Myo51’s localizations to cytoplasmic puncta, actin cables, and the contractile ring. Myo51 puncta contain multiple Myo51 molecules and walk continuously on actin filaments in rng8+ cells, whereas Myo51 forms speckles containing only one dimer and does not move efficiently on actin tracks in rng8Δ. Consistently, Myo51 transports artificial cargos efficiently in vivo, and this activity is regulated by Rng8. Purified Rng8 and Rng9 form stable higher-order complexes. Collectively, we propose that Rng8 and Rng9 form oligomers and cluster multiple Myo51 dimers to regulate Myo51 localization and functions.

scholarly journals Pushing for answers: is myosin V directly involved in moving mitochondria?

2008 ◽  
Vol 181 (1) ◽  
pp. 15-18 ◽  
Author(s):  
Rajeshwari R. Valiathan ◽  
Lois S. Weisman
Keyword(s):  
Cell Division ◽  
Light Chain ◽  
Budding Yeast ◽  
Myosin V ◽  
Class V ◽  
Mitochondrial Transport ◽  
Direct Involvement ◽  
Cell Biol ◽  
Myosin Motors

In budding yeast, the actin-based class V myosin motors, Myo2 and Myo4, transport virtually all organelles from mother to bud during cell division. Until recently, it appeared that mitochondria may be an exception, with studies showing that the Arp2/3 complex is required for their movement. However, several recent studies have proposed that Myo2 has a direct involvement in mitochondria inheritance. In this issue, Altmann et al. (Altmann, K., M. Frank, D. Neumann, S. Jakobs, and B. Westermann. 2008. J. Cell Biol. 181:119–130) provide the strongest support yet that Myo2 and its associated light chain Mlc1 function directly and significantly in both mitochondria–actin interactions and in the movement of mitochondria from mother to bud. The conflicting functions of Arp 2/3 and Myo2 may be reconciled by the existence of multiple pathways involved in mitochondrial transport.

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