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


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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    • "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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    • "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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    Full-text · Article · Jan 2013 · PLoS ONE
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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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