Temporal Control of Contractile Ring Assembly by Plo1 Regulation of Myosin II Recruitment by Mid1/Anillin

Institut Curie, Centre de Recherche F-75248 Paris, France.
Current biology: CB (Impact Factor: 9.57). 03/2011; 21(6):473-9. DOI: 10.1016/j.cub.2011.02.003
Source: PubMed

ABSTRACT In eukaryotes, cytokinesis generally involves an actomyosin ring, the contraction of which promotes daughter cell segregation. Assembly of the contractile ring is tightly controlled in space and time. In the fission yeast, contractile ring components are first organized by the anillin-like protein Mid1 into medial cortical nodes. These nodes then coalesce laterally into a functional contractile ring. Although Mid1 is present at the medial cortex throughout G2, recruitment of contractile ring components to nodes starts only at mitotic onset, indicating that this event is cell-cycle regulated. Polo kinases are key temporal coordinators of mitosis and cytokinesis, and the Polo-like kinase Plo1 is known to activate Mid1 nuclear export at mitotic onset, coupling division plane specification to nuclear position. Here we provide evidence that Plo1 also triggers the recruitment of contractile ring components into medial cortical nodes. Plo1 binds at least two independent sites on Mid1, including a consensus site phosphorylated by Cdc2. Plo1 phosphorylates several residues within the first 100 amino acids of Mid1, which directly interact with the IQGAP Rng2, and influences the timing of myosin II recruitment. Plo1 thereby facilitates contractile ring assembly at mitotic onset.

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Available from: Damarys Loew, Sep 28, 2015
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    • "Next, we examined the kinetics of nuclear congression in wildtype and mutant zygotes by monitoring the migration of the SPB at 1-min intervals before and after cell fusion until SPBs were juxtaposed (hereafter referred to as SPB fusion), using Sfi1-GFP as a marker (Almonacid et al., 2011). Distances between the two SPBs over time were measured from kymographs (Fig. 2, A and B). "
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    ABSTRACT: Microtubules (MTs) and associated motors play a central role in nuclear migration, which is crucial for diverse biological functions including cell division, polarity, and sexual reproduction. In this paper, we report a dual mechanism underlying nuclear congression during fission yeast karyogamy upon mating of haploid cells. Using microfluidic chambers for long-term imaging, we captured the precise timing of nuclear congression and identified two minus end-directed motors operating in parallel in this process. Kinesin-14 Klp2 associated with MTs may cross-link and slide antiparallel MTs emanating from the two nuclei, whereas dynein accumulating at spindle pole bodies (SPBs) may pull MTs nucleated from the opposite SPB. Klp2-dependent nuclear congression proceeds at constant speed, whereas dynein accumulation results in an increase of nuclear velocity over time. Surprisingly, the light intermediate chain Dli1, but not dynactin, is required for this previously unknown function of dynein. We conclude that efficient nuclear congression depends on the cooperation of two minus end-directed motors. © 2015 Scheffler et al.
    The Journal of Cell Biology 04/2015; 209(1):47-58. DOI:10.1083/jcb.201409087 · 9.83 Impact Factor
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    • "Mid1 rather than Cdr2, is central to this process. Upon mitotic entry, the nuclear pool of Mid1 is signalled into the nodes where it is activated to interact with proteins involved in CAR architecture and function [14], [15]. In the “search, capture and pull model”, Mid1 recruits cytoskeletal proteins such as the formin Cdc12 or the type II myosin (heavy chain Myo2 and light chains Cdc4 and Rlc1). "
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    ABSTRACT: Most cells enter mitosis once they have reached a defined size. In the fission yeast Schizosaccharomyces pombe, mitotic entry is orchestrated by a geometry-sensing mechanism that involves the Cdk1/Cdc2-inhibiting Wee1 kinase. The factors upstream of Wee1 gather together in interphase to form a characteristic medial and cortical belt of nodes. Nodes are also considered to be precursors of the cytokinesis contractile actomyosin ring (CAR). Here we describe a new component of the interphase nodes and cytokinesis rings, which we named Nod1. Consistent with its role in cell size control at division, nod1Δ cells were elongated and epistatic with regulators of Wee1. Through biochemical and localisation studies, we placed Nod1 in a complex with the Rho-guanine nucleotide exchange factor Gef2. Nod1 and Gef2 mutually recruited each other in nodes and Nod1 also assembles Gef2 in rings. Like gef2Δ, nod1Δ cells showed a mild displacement of their division plane and this phenotype was severely exacerbated when the parallel Polo kinase pathway was also compromised. We conclude that Nod1 specifies the division site by localising Gef2 to the mitotic cell middle. Previous work showed that Gef2 in turn anchors factors that control the spatio-temporal recruitment of the actin nucleation machinery. It is believed that the actin filaments originated from the nodes pull nodes together into a single contractile ring. Surprisingly however, we found that node proteins could form pre-ring helical filaments in a cdc12-112 mutant in which nucleation of the actin ring is impaired. Furthermore, the deletion of either nod1 or gef2 created an un-expected situation where different ring components were recruited sequentially rather than simultaneously. At later stages of cytokinesis, these various rings appeared inter-fitted rather than merged. This study brings a new slant to the understanding of CAR assembly and function.
    PLoS ONE 01/2013; 8(1):e54142. DOI:10.1371/journal.pone.0054142 · 3.23 Impact Factor
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    • "It may act as a scaffold, stabilizing and increasing the amount of Mid1 and recruiting myosin and its light chain. Since the assembly of cytokinesis proteins into nodes is regulated by the Polo kinase Plo1, it will be interesting to determine if phosphorylation of Mid1 by Plo1 regulates binding to Rng2 [13]. Rng2 is essential for recruitment of Factin to the ring in both node dependent and independent pathways, but the mechanism by which Rng2 leads to F-actin recruitment to the ring is unresolved. "
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    ABSTRACT: IQGAPs are a family of scaffolding proteins with multiple domains, named for the IQ motifs and GTPase activating protein (GAP) related domains. Despite their GAP homology, IQGAP proteins act as effectors for GTP-bound GTPases of the Ras superfamily and do not stimulate GTP hydrolysis. IQGAPs are found in eukaryotic cells from yeast to human, and localize to actin-containing structures such as lamellipodia, membrane ruffles, cell-cell adhesions, phagocytic cups, and the actomyosin ring formed during cytokinesis. Mammalian IQGAPs also act as scaffolds for signaling pathways. IQGAPs perform their myriad functions through association with a large number of proteins including filamentous actin (F-actin), GTPases, calcium-binding proteins, microtubule binding proteins, kinases, and receptors. The focus of this paper is on recent studies describing new binding partners, mechanisms of regulation, and biochemical and physiological functions of IQGAPs in yeast, amoeba, and mammalian cells.
    International Journal of Cell Biology 02/2012; 2012(11):894817. DOI:10.1155/2012/894817
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