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      Distinct Roles of Myosin-II Isoforms in Cytokinesis under Normal and Stressed Conditions


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          To address the question of why more than one myosin-II isoform is expressed in a single cell to drive cytokinesis, we analyzed the roles of the myosin-II isoforms, Myo2 and Myp2, of the fission yeast Schizosaccharomyces pombe, in cytokinesis under normal and stressed conditions. We found that Myp2 controls the disassembly, stability, and constriction initiation of the Myo2 ring in response to high-salt stress. A C-terminal coiled-coil domain of Myp2 is required for its immobility and contractility during cytokinesis, and when fused to the tail of the dynamic Myo2, renders the chimera the low-turnover property. We also found, by following distinct processes in real time at the single-cell level, that Myo2 and Myp2 are differentially required but collectively essential for guiding extracellular matrix remodeling during cytokinesis. These results suggest that the dynamic and immobile myosin-II isoforms are evolved to carry out cytokinesis with robustness under different growth conditions.

          Graphical Abstract


          • The myosin-II isoforms Myo2 and Myp2 display distinct responses to cellular stress

          • Myp2 controls the constriction initiation of Myo2 during stress response

          • A C-terminal region of Myp2 is required for its immobility during cytokinesis

          • Myo2 and Myp2 are differentially required for guiding ECM remodeling during cytokinesis


          Molecular Mechanism of Behavior; Cell Biology; Functional Aspects of Cell Biology

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          Most cited references48

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          Understanding cytokinesis: lessons from fission yeast.

          For decades after the discovery that a contractile ring made of actin filaments and myosin II produces the force to constrict the cleavage furrow of animal cells, the complexity of cytokinesis has slowed progress in understanding the mechanism. Mechanistic insights, however, have been obtained by genetic, biochemical, microscopic and mathematical modelling approaches in the fission yeast Schizosaccharomyces pombe. Many features that have been identified in fission yeast are probably shared with animal cells, as both inherited many cytokinesis genes from their common ancestor about one billion years ago.
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            Involvement of an Actomyosin Contractile Ring in Saccharomyces cerevisiae Cytokinesis

            In Saccharomyces cerevisiae, the mother cell and bud are connected by a narrow neck. The mechanism by which this neck is closed during cytokinesis has been unclear. Here we report on the role of a contractile actomyosin ring in this process. Myo1p (the only type II myosin in S. cerevisiae) forms a ring at the presumptive bud site shortly before bud emergence. Myo1p ring formation depends on the septins but not on F-actin, and preexisting Myo1p rings are stable when F-actin is depolymerized. The Myo1p ring remains in the mother–bud neck until the end of anaphase, when a ring of F-actin forms in association with it. The actomyosin ring then contracts to a point and disappears. In the absence of F-actin, the Myo1p ring does not contract. After ring contraction, cortical actin patches congregate at the mother–bud neck, and septum formation and cell separation rapidly ensue. Strains deleted for MYO1 are viable; they fail to form the actin ring but show apparently normal congregation of actin patches at the neck. Some myo1Δ strains divide nearly as efficiently as wild type; other myo1Δ strains divide less efficiently, but it is unclear whether the primary defect is in cytokinesis, septum formation, or cell separation. Even cells lacking F-actin can divide, although in this case division is considerably delayed. Thus, the contractile actomyosin ring is not essential for cytokinesis in S. cerevisiae. In its absence, cytokinesis can still be completed by a process (possibly localized cell–wall synthesis leading to septum formation) that appears to require septin function and to be facilitated by F-actin.
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              Yeast Cbk1 and Mob2 activate daughter-specific genetic programs to induce asymmetric cell fates.

              In Saccharomyces cerevisiae, mothers and daughters have distinct fates. We show that Cbk1 kinase and its interacting protein Mob2 regulate this asymmetry by inducing daughter-specific genetic programs. Daughter-specific expression is due to Cbk1/Mob2-dependent activation and localization of the Ace2 transcription factor to the daughter nucleus. Ectopic localization of active Ace2 to mother nuclei is sufficient to activate daughter-specific genes in mothers. Eight genes are daughter-specific under the tested conditions, while two are daughter-specific only in saturated cultures. Some daughter-specific gene products contribute to cell separation by degrading the cell wall. These experiments define programs of gene expression specific to daughters and describe how those programs are controlled.

                Author and article information

                16 March 2019
                26 April 2019
                16 March 2019
                : 14
                : 69-87
                [1 ]Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6058, USA
                [2 ]Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9747 AE Groningen, The Netherlands
                [3 ]Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210, USA
                Author notes
                []Corresponding author ebi@ 123456pennmedicine.upenn.edu

                These authors contributed equally


                Lead Contact

                © 2019 The Author(s)

                This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

                : 20 July 2018
                : 30 January 2019
                : 12 March 2019

                molecular mechanism of behavior,cell biology,functional aspects of cell biology


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