Cdc15 integrates Tem1 GTPase-mediated spatial signals with Polo kinase-mediated temporal cues to activate mitotic exit

David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Genes & development (Impact Factor: 10.8). 09/2011; 25(18):1943-54. DOI: 10.1101/gad.17257711
Source: PubMed


In budding yeast, a Ras-like GTPase signaling cascade known as the mitotic exit network (MEN) promotes exit from mitosis. To ensure the accurate execution of mitosis, MEN activity is coordinated with other cellular events and restricted to anaphase. The MEN GTPase Tem1 has been assumed to be the central switch in MEN regulation. We show here that during an unperturbed cell cycle, restricting MEN activity to anaphase can occur in a Tem1 GTPase-independent manner. We found that the anaphase-specific activation of the MEN in the absence of Tem1 is controlled by the Polo kinase Cdc5. We further show that both Tem1 and Cdc5 are required to recruit the MEN kinase Cdc15 to spindle pole bodies, which is both necessary and sufficient to induce MEN signaling. Thus, Cdc15 functions as a coincidence detector of two essential cell cycle oscillators: the Polo kinase Cdc5 synthesis/degradation cycle and the Tem1 G-protein cycle. The Cdc15-dependent integration of these temporal (Cdc5 and Tem1 activity) and spatial (Tem1 activity) signals ensures that exit from mitosis occurs only after proper genome partitioning.

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    • "Our data do not exclude an important role of Bfa1 as a target for Cdc5 in the adaptation response, but rather indicate that Cdc5 acts in an additional biochemical pathway that has a considerable impact on the process of adaptation. In fact, we envision that Cdc5 could have a dual contribution to the adaptation process: the first one via its housekeeping function in activating mitotic exit (i.e., Bfa1 inhibition and Cdc15 activation;Rock and Amon, 2011), and the second one via its DNA damage-specific function mediated by the RSC pathway identified in this study. It is a formal possibility that the Bfa1-independent contribution of Cdc5 to checkpoint adaptation is mediated through a currently unknown regulatory input on the mitotic exit network, since overexpression of CDC5 can suppress the Cdc14 activation defects of some MEN mutants (Visintin et al., 2003). "
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    ABSTRACT: Cell-cycle checkpoints are essential feedback mechanisms that promote genome integrity. However, in the face of unrepairable DNA lesions, bypass mechanisms can suppress checkpoint activity and allow cells to resume proliferation. The molecular mechanisms underlying this biological response are currently not understood. Taking advantage of unique separation-of-function mutants, we show that the Polo-like kinase (PLK) Cdc5 uses a phosphopriming-based interaction mechanism to suppress G2/M checkpoint arrest by targeting Polo kinase activity to centrosomes. We also show that key subunits of the evolutionarily conserved RSC complex are critical downstream effectors of Cdc5 activity in checkpoint suppression. Importantly, the lethality and checkpoint defects associated with loss of Cdc5 Polo box activity can be fully rescued by artificially anchoring Cdc5 kinase domain to yeast centrosomes. Collectively, our results highlight a previously unappreciated role for centrosomes as key signaling centers for the suppression of cell-cycle arrest induced by persistent or unrepairable DNA damage.
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    • "The likely negative regulation of Cdc15 and/or Dbf2/Mob1 by mitotic CDK (Jaspersen and Morgan 2000) may be relieved by dephosphorylation of these proteins by Cdc14, after its release by the FEAR pathway prior to MEN activation (Konig et al. 2010). Tem1 appears to be the first MEN component loaded onto Nud1 at the SBP, and photobleaching analysis shows that it is initially highly dynamic in early anaphase (Cenamor et al. 1999; Bardin et al. 2000; Menssen et al. 2001; Visintin and Amon 2001; Molk et al. 2004; Rock and Amon 2011; Valerio-Santiago and Monje-Casas 2011). "
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    Full-text · Article · Dec 2012 · Genetics
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    • "During mitosis, association of MEN components with SPBs is essential for MEN activity (Rock and Amon, 2011; Valerio-Santiago and Monje-Casas, 2011). The MEN components Bub2-Bfa1, Tem1, Cdc15, and Dbf2-Mob1 localize to SPBs in a manner that depends on the spindle pole body component Nud1 (Bardin et al., 2000; Gruneberg et al., 2000; Visintin and Amon, 2001). "
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    ABSTRACT: The mitotic exit network (MEN) is an essential GTPase signaling pathway that triggers exit from mitosis in budding yeast. We show here that during meiosis, the MEN is dispensable for exit from meiosis I but contributes to the timely exit from meiosis II. Consistent with a role for the MEN during meiosis II, we find that the signaling pathway is active only during meiosis II. Our analysis further shows that MEN signaling is modulated during meiosis in several key ways. Whereas binding of MEN components to spindle pole bodies (SPBs) is necessary for MEN signaling during mitosis, during meiosis MEN signaling occurs off SPBs and does not require the SPB recruitment factor Nud1. Furthermore, unlike during mitosis, MEN signaling is controlled through the regulated interaction between the MEN kinase Dbf20 and its activating subunit Mob1. Our data lead to the conclusion that a pathway essential for vegetative growth is largely dispensable for the specialized meiotic divisions and provide insights into how cell cycle regulatory pathways are modulated to accommodate different modes of cell division.
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