Localization of the ubiquitin ligase Dma1 to the fission yeast contractile ring is modulated by phosphorylation

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.

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Paxillin-Mediated Recruitment of Calcineurin to the Contractile Ring Is Required for the Correct Progression of Cytokinesis in Fission Yeast

Cell Reports ◽

10.1016/j.celrep.2018.09.062 ◽

2018 ◽

Vol 25 (3) ◽

pp. 772-783.e4 ◽

Cited By ~ 14

Author(s):

Rebeca Martín-García ◽

Victor Arribas ◽

Pedro M. Coll ◽

Mario Pinar ◽

Raul A. Viana ◽

...

Keyword(s):

Fission Yeast ◽

Contractile Ring

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Formin’ the cytokinetic ring

The Journal of Cell Biology ◽

10.1083/jcb.2031if ◽

2013 ◽

Vol 203 (1) ◽

pp. 3-3

Author(s):

Ben Short

Keyword(s):

Fission Yeast ◽

Contractile Ring

Study reveals how two formin proteins cooperate to assemble the contractile ring in fission yeast.

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

The Journal of Cell Biology ◽

10.1083/jcb.201308146 ◽

2014 ◽

Vol 205 (3) ◽

pp. 357-375 ◽

Cited By ~ 30

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.

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Fission yeast myosin Myo2 is down-regulated in actin affinity by light chain phosphorylation

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1703161114 ◽

2017 ◽

Vol 114 (35) ◽

pp. E7236-E7244 ◽

Cited By ~ 12

Author(s):

Luther W. Pollard ◽

Carol S. Bookwalter ◽

Qing Tang ◽

Elena B. Krementsova ◽

Kathleen M. Trybus ◽

...

Keyword(s):

Fission Yeast ◽

Light Chain ◽

Force Production ◽

Class Ii ◽

Cell System ◽

Cell Cortex ◽

Animal Cells ◽

Contractile Ring ◽

Biophysical Studies

Studies in fission yeast Schizosaccharomyces pombe have provided the basis for the most advanced models of the dynamics of the cytokinetic contractile ring. Myo2, a class-II myosin, is the major source of tension in the contractile ring, but how Myo2 is anchored and regulated to produce force is poorly understood. To enable more detailed biochemical/biophysical studies, Myo2 was expressed in the baculovirus/Sf9 insect cell system with its two native light chains, Rlc1 and Cdc4. Milligram yields of soluble, unphosphorylated Myo2 were obtained that exhibited high actin-activated ATPase activity and in vitro actin filament motility. The fission yeast specific chaperone Rng3 was thus not required for expression or activity. In contrast to nonmuscle myosins from animal cells that require phosphorylation of the regulatory light chain for activation, phosphorylation of Rlc1 markedly reduced the affinity of Myo2 for actin. Another unusual feature of Myo2 was that, unlike class-II myosins, which generally form bipolar filamentous structures, Myo2 showed no inclination to self-assemble at approximately physiological salt concentrations, as analyzed by sedimentation velocity ultracentrifugation. This lack of assembly supports the hypothesis that clusters of Myo2 depend on interactions at the cell cortex in structural units called nodes for force production during cytokinesis.

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Myosins generate contractile force and maintain organization in the cytokinetic contractile ring

10.1101/2021.05.02.442363 ◽

2021 ◽

Author(s):

Zachary A. McDargh ◽

Shuyuan Wang ◽

Harvey F. Chin ◽

Sathish Thiyagarajan ◽

Erdem Karatekin ◽

...

Keyword(s):

Fission Yeast ◽

Striated Muscle ◽

Protein Complexes ◽

Myosin Ii ◽

Force Production ◽

Super Resolution ◽

Building Blocks ◽

Contractile Ring ◽

Ring Model ◽

Self Assembling

During cytokinesis, cells assemble an actomyosin contractile ring whose tension constricts and divides cells, but the ring tension was rarely measured. Actomyosin force generation is well understood for the regular sarcomeric architecture of striated muscle, but recent super-resolution studies of fission yeast contractile rings revealed organizational building blocks that are not sarcomeres but irregularly positioned plasma membrane-anchored protein complexes called nodes. Here, we measured contractile ring tensions in fission yeast protoplast cells. The myosin II isoforms Myo2 and Myp2 generated the tension, with a ~2-fold greater contribution from Myo2. Simulations of a molecularly detailed ring model revealed a sliding node mechanism for tension, where nodes hosting tense actin filaments were pulled bidirectionally around the ring. Myo2 and Myp2 chaperoned self-assembling components into the ring organization, and anchored the ring against bridging instabilities. Thus, beyond force production, Myo2 and Myp2 are the principal organizers, bundlers and anchors of the contractile ring.

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The F-actin bundler α-actinin Ain1 is tailored for ring assembly and constriction during cytokinesis in fission yeast

Molecular Biology of the Cell ◽

10.1091/mbc.e16-01-0010 ◽

2016 ◽

Vol 27 (11) ◽

pp. 1821-1833 ◽

Cited By ~ 35

Author(s):

Yujie Li ◽

Jenna R. Christensen ◽

Kaitlin E. Homa ◽

Glen M. Hocky ◽

Alice Fok ◽

...

Keyword(s):

Fission Yeast ◽

Actin Filament ◽

Actin Filaments ◽

Biochemical Properties ◽

Ring Formation ◽

Cross Linking ◽

Contractile Ring ◽

Mixed Polarity ◽

Dividing Cells

The actomyosin contractile ring is a network of cross-linked actin filaments that facilitates cytokinesis in dividing cells. Contractile ring formation has been well characterized in Schizosaccharomyces pombe, in which the cross-linking protein α-actinin SpAin1 bundles the actin filament network. However, the specific biochemical properties of SpAin1 and whether they are tailored for cytokinesis are not known. Therefore we purified SpAin1 and quantified its ability to dynamically bind and bundle actin filaments in vitro using a combination of bulk sedimentation assays and direct visualization by two-color total internal reflection fluorescence microscopy. We found that, while SpAin1 bundles actin filaments of mixed polarity like other α-actinins, SpAin1 has lower bundling activity and is more dynamic than human α-actinin HsACTN4. To determine whether dynamic bundling is important for cytokinesis in fission yeast, we created the less dynamic bundling mutant SpAin1(R216E). We found that dynamic bundling is critical for cytokinesis, as cells expressing SpAin1(R216E) display disorganized ring material and delays in both ring formation and constriction. Furthermore, computer simulations of initial actin filament elongation and alignment revealed that an intermediate level of cross-linking best facilitates filament alignment. Together our results demonstrate that dynamic bundling by SpAin1 is important for proper contractile ring formation and constriction.

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