The kinesin-14 Klp2 is negatively regulated by the SIN for proper spindle elongation and telophase nuclear positioning

Article (PDF Available)inMolecular biology of the cell 23(23) · October 2012with42 Reads
DOI: 10.1091/mbc.E12-07-0532 · Source: PubMed
In S. pombe, a late mitotic kinase pathway called the Septation Initiation Network (SIN) triggers cytokinesis. Here, we show that the SIN is also involved in regulating anaphase spindle elongation and telophase nuclear positioning via inhibition of Klp2, a minus end directed kinesin-14. Klp2 is known to localize to microtubules (MTs) and have roles in interphase nuclear positioning, mitotic chromosome alignment, and nuclei migration during karyogamy (nuclear fusion during mating). We observe SIN-dependent disappearance of Klp2 from MTs in anaphase and we have found that this is mediated by direct phosphorylation of Klp2 by the SIN kinase Sid2 which abrogates loading of Klp2 onto MTs by inhibiting its interaction with Mal3 (EB1 homolog). Disruption of Klp2 MT localization is required for efficient anaphase spindle elongation. Furthermore, when cytokinesis is delayed, SIN inhibition of Klp2 acts in concert with microtubules emanating from the equatorial microtubule organizing center to position the nuclei away from the cell division site. These results reveal novel functions of the SIN in regulating the MT cytoskeleton and suggest that the SIN may have broader functions in regulating cellular organization in late mitosis than previously realized.

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Available from: Dannel Mccollum
    • "Kinesin-14s are implicated in MT sliding, and accordingly , Klp2 has been shown to slide newly nucleated MTs toward minus ends (Janson et al., 2007). It is therefore likely that Klp2 generates pulling forces during nuclear congression in a similar manner: by sliding antiparallel MTs relative to each other as suggested previously for budding yeast Kar3 (Meluh and Rose, 1990) and for nuclei clustering at the end of mitosis in fission yeast mutants defective in septation (Mana-Capelli et al., 2012). Alternatively, Klp2 might cross-link shrinking plus ends and potentially induce their depolymerization. "
    [Show abstract] [Hide abstract] 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.
    Full-text · Article · Apr 2015
    • "This checkpoint is also triggered by mutants in CAR components (Mishra et al., 2004). The checkpoint arrest requires SIN function (Le Goff et al., 1999; Liu et al., 2000; Liu et al., 1999), and Sid2p is required for CAR maintenance when the checkpoint is active (Gavilán et al., 2014) and for positioning the nuclei away from the CAR in cells arrested by the CAR checkpoint (Table 1) (Mana-Capelli et al., 2012). "
    [Show abstract] [Hide abstract] ABSTRACT: The septation initiation network (SIN) regulates aspects of cell growth and division in Schizosaccharomyces pombe and is essential for cytokinesis. Insufficient signalling results in improper assembly of the contractile ring and failure of cytokinesis, generating multinucleated cells, whereas too much SIN signalling uncouples cytokinesis from the rest of the cell cycle. SIN signalling is therefore tightly controlled to coordinate cytokinesis with chromosome segregation. Signalling originates from the cytoplasmic face of the spindle pole body (SPB), and asymmetric localisation of some SIN proteins to one of the two SPBs during mitosis is important for regulation of the SIN. Recent studies have identified in vivo substrates of the SIN, which include components involved in mitotic control, those of the contractile ring and elements of the signalling pathway regulating polarised growth. The SIN is also required for spore formation following meiosis. This has provided insights into how the SIN performs its diverse functions in the cell cycle and shed new light on its regulation.
    Article · Feb 2015
    • "The SIN coordinates nuclear division with cytokinesis from the SPB by directing the formation, maintenance, and constriction of the CR, as well as septum formation (Balasubramanian et al., 1998; Jin et al., 2006; Hachet and Simanis, 2008; reviewed in Gould and Simanis, 1997; Johnson et al., 2012). In addition, the SIN inhibits polarized cell growth during mitosis and is involved in regulating anaphase spindle elongation and positioning the nuclei away from the cell division site in telophase via inhibition of Klp2, a minus end–directed kine- sin-14 (Mana-Capelli et al., 2012; Gupta et al., 2013). The SIN is the analogue of the mitotic exit network (MEN) in Saccharomyces cerevisiae. "
    [Show abstract] [Hide abstract] ABSTRACT: In Schizosaccharomyces pombe late mitotic events are coordinated with cytokinesis by the septation initiation network (SIN), an essential spindle pole body (SPB)-associated kinase cascade, which controls the formation, maintenance and constriction of the cytokinetic ring. It is not fully understood how SIN initiation is temporally regulated, but it depends on the activation of the GTPase Spg1 that is inhibited during interphase by the essential bipartite GAP, Byr4-Cdc16. Cells are particularly sensitive to the modulation of Byr4, which undergoes cell cycle-dependent phosphorylation presumed to regulate its function. Polo-like kinase, which promotes SIN activation, is partially responsible for Byr4 phosphorylation. Here, we show that Byr4 is also controlled by Cdk1-mediated phosphorylation. A Cdk1 non-phosphorylatable Byr4 phosphomutant displays severe cell division defects including the formation of elongated, multinucleate cells, failure to maintain the cytokinetic ring and compromised SPB association of the SIN kinase Cdc7. Our analyses reveal that Cdk1-mediated phosphoregulation of Byr4 facilitates complete removal of Byr4 from metaphase SPBs in concert with Plo1, revealing an unexpected role for Cdk1 in promoting cytokinesis through activation of the SIN pathway.
    Article · Jun 2014
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