scholarly journals Unifying the mechanism of mitotic exit control in a spatiotemporal logical model

PLoS Biology ◽  
2020 ◽  
Vol 18 (11) ◽  
pp. e3000917
Author(s):  
Rowan S. M. Howell ◽  
Cinzia Klemm ◽  
Peter H. Thorpe ◽  
Attila Csikász-Nagy
Keyword(s):  
Living Cells ◽  
Mitotic Exit ◽  
Spatial Effects ◽  
Protein Activity ◽  
Logical Model ◽  
Mitotic Exit Network ◽  
Early Anaphase ◽  
Gap Phase ◽  
Cell Variation ◽  
Spindle Position

The transition from mitosis into the first gap phase of the cell cycle in budding yeast is controlled by the Mitotic Exit Network (MEN). The network interprets spatiotemporal cues about the progression of mitosis and ensures that release of Cdc14 phosphatase occurs only after completion of key mitotic events. The MEN has been studied intensively; however, a unified understanding of how localisation and protein activity function together as a system is lacking. In this paper, we present a compartmental, logical model of the MEN that is capable of representing spatial aspects of regulation in parallel to control of enzymatic activity. We show that our model is capable of correctly predicting the phenotype of the majority of mutants we tested, including mutants that cause proteins to mislocalise. We use a continuous time implementation of the model to demonstrate that Cdc14 Early Anaphase Release (FEAR) ensures robust timing of anaphase, and we verify our findings in living cells. Furthermore, we show that our model can represent measured cell–cell variation in Spindle Position Checkpoint (SPoC) mutants. This work suggests a general approach to incorporate spatial effects into logical models. We anticipate that the model itself will be an important resource to experimental researchers, providing a rigorous platform to test hypotheses about regulation of mitotic exit.

scholarly journals Unifying the mechanism of mitotic exit control in a spatio-temporal logical model

2020 ◽  
Author(s):  
R. S. M. Howell ◽  
C. Klemm ◽  
P. H. Thorpe ◽  
A. Csikász-Nagy
Keyword(s):  
Mitotic Exit ◽  
Protein Activity ◽  
Logical Model ◽  
Temporal Cues ◽  
Early Anaphase ◽  
Unified View ◽  
Spatio Temporal ◽  
Cell Variation ◽  
The Impact

1AbstractThe transition from mitosis into the first gap phase of the cell cycle in budding yeast is controlled by the Mitotic Exit Network (MEN). The network interprets spatio-temporal cues about the progression of mitosis and ensures that release of Cdc14 phosphatase occurs only after completion of key mitotic events. The MEN has been studied intensively however a unified understanding of how localization and protein activity function together as a system is lacking. In this paper we present a compartmental, logical model of the MEN that is capable of representing spatial aspects of regulation in parallel to control of enzymatic activity. Through optimization of the model, we reveal insights into role of Cdc5 in Cdc15 localization and the importance of Lte1 regulation in control of Bfa1. We show that our model is capable of correctly predicting the phenotype of ∼ 80% of mutants we tested, including mutants representing mislocalizing proteins. We use a continuous time implementation of the model to demonstrate the role of Cdc14 Early Anaphase Release (FEAR) to ensure robust timing of anaphase and verify our findings in living cells. We show that our model can represent measured cell-cell variation in Spindle Position Checkpoint (SPoC) mutants. Finally, we use the model to predict the impact of forced localization of MEN proteins and validate these predictions experimentally. This model represents a unified view of the mechanism of mitotic exit control.

scholarly journals Spatial signals link exit from mitosis to spindle position

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Jill Elaine Falk ◽  
Dai Tsuchiya ◽  
Jolien Verdaasdonk ◽  
Soni Lacefield ◽  
Kerry Bloom ◽  
...  
Keyword(s):  
Spindle Pole ◽  
Mitotic Exit ◽  
Zone Model ◽  
Cytoplasmic Microtubule ◽  
Binucleate Cells ◽  
Spindle Pole Bodies ◽  
Mitotic Exit Network ◽  
Bud Neck ◽  
Competing Models ◽  
Spindle Position

In budding yeast, if the spindle becomes mispositioned, cells prevent exit from mitosis by inhibiting the mitotic exit network (MEN). The MEN is a signaling cascade that localizes to spindle pole bodies (SPBs) and activates the phosphatase Cdc14. There are two competing models that explain MEN regulation by spindle position. In the 'zone model', exit from mitosis occurs when a MEN-bearing SPB enters the bud. The 'cMT-bud neck model' posits that cytoplasmic microtubule (cMT)-bud neck interactions prevent MEN activity. Here we find that 1) eliminating cMT– bud neck interactions does not trigger exit from mitosis and 2) loss of these interactions does not precede Cdc14 activation. Furthermore, using binucleate cells, we show that exit from mitosis occurs when one SPB enters the bud despite the presence of a mispositioned spindle. We conclude that exit from mitosis is triggered by a correctly positioned spindle rather than inhibited by improper spindle position.

scholarly journals Putting the Brake on FEAR: Tof2 Promotes the Biphasic Release of Cdc14 Phosphatase during Mitotic Exit

2009 ◽  
Vol 20 (1) ◽  
pp. 245-255 ◽  
Author(s):  
William G. Waples ◽  
Charly Chahwan ◽  
Marta Ciechonska ◽  
Brigitte D. Lavoie
Keyword(s):  
Chromosome Segregation ◽  
Genetic Data ◽  
Mitotic Exit ◽  
Genetic Interactions ◽  
Genetic Screens ◽  
Rdna Array ◽  
Mitotic Exit Network ◽  
M Phase ◽  
Early Anaphase ◽  
Biphasic Release

The completion of chromosome segregation during anaphase requires the hypercondensation of the ∼1-Mb rDNA array, a reaction dependent on condensin and Cdc14 phosphatase. Using systematic genetic screens, we identified 29 novel genetic interactions with budding yeast condensin. Of these, FOB1, CSM1, LRS4, and TOF2 were required for the mitotic condensation of the tandem rDNA array localized on chromosome XII. Interestingly, whereas Fob1 and the monopolin subunits Csm1 and Lrs4 function in rDNA condensation throughout M phase, Tof2 was only required during anaphase. We show that Tof2, which shares homology with the Cdc14 inhibitor Net1/Cfi1, interacts with Cdc14 phosphatase and its deletion suppresses defects in mitotic exit network (MEN) components. Consistent with these genetic data, the onset of Cdc14 release from the nucleolus was similar in TOF2 and tof2Δ cells; however, the magnitude of the release was dramatically increased in the absence of Tof2, even when the MEN pathway was compromised. These data support a model whereby Tof2 coordinates the biphasic release of Cdc14 during anaphase by restraining a population of Cdc14 in the nucleolus after activation of the Cdc14 early anaphase release (FEAR) network, for subsequent release by the MEN.

scholarly journals BFA1 has multiple positive roles in directing late mitotic events in S. cerevisiae

2018 ◽  
Author(s):  
J Whalen ◽  
C Sniffen ◽  
S Gartland ◽  
M Vannini ◽  
A Seshan
Keyword(s):  
Budding Yeast ◽  
Spindle Pole Body ◽  
Biological Significance ◽  
Spindle Pole ◽  
Mitotic Exit ◽  
Genome Integrity ◽  
Mitotic Exit Network ◽  
M Phase ◽  
Regulation Of Cell Cycle ◽  
Spindle Position

ABSTRACTThe proper regulation of cell cycle transitions is paramount to the maintenance of cellular genome integrity. In budding yeast, the mitotic exit network (MEN) is a Ras-like signaling cascade that effects the transition from M phase to G1 during the cell division cycle in budding yeast. MEN activation is tightly regulated. It occurs during anaphase and is coupled to mitotic spindle position by the spindle position checkpoint (SPoC). Bfa1 is a key component of the SPoC and functions as part of a two-component GAP complex along with Bub2. The GAP activity of Bfa1-Bub2 keeps the MEN GTPase Tem1 inactive in cells with mispositioned spindles, thereby preventing inappropriate mitotic exit and preserving genome integrity. Interestingly, a GAP-independent role for Bfa1 in mitotic exit regulation has been previously identified. However the nature of this Bub2-independent role and its biological significance are not understood. Here we show that Bfa1 also activates the MEN by promoting the localization of Tem1 primarily to the daughter spindle pole body (dSPB). We demonstrate that the overexpression of BFA1 is lethal due to defects in Tem1 localization, which is required for its activity. In addition, our studies demonstrate a Tem1-independent role for Bfa1 in promoting proper cytokinesis. Cells lacking TEM1, in which the essential mitotic exit function is bypassed, exhibit cytokinesis defects. These defects are suppressed by the overexpression of BFA1. We conclude that Bfa1 functions to both inhibit and activate late mitotic events.

scholarly journals A Novel Hyperactive Nud1 Mitotic Exit Network Scaffold Causes Spindle Position Checkpoint Bypass in Budding Yeast

Cells ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 46
Author(s):  
Michael Vannini ◽  
Victoria R. Mingione ◽  
Ashleigh Meyer ◽  
Courtney Sniffen ◽  
Jenna Whalen ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Budding Yeast ◽  
Signal Transduction Pathway ◽  
Spindle Pole ◽  
Mitotic Exit ◽  
Independent Manner ◽  
Spindle Pole Bodies ◽  
Mitotic Exit Network ◽  
Cell Cycle Transition ◽  
Spindle Position

Mitotic exit is a critical cell cycle transition that requires the careful coordination of nuclear positioning and cyclin B destruction in budding yeast for the maintenance of genome integrity. The mitotic exit network (MEN) is a Ras-like signal transduction pathway that promotes this process during anaphase. A crucial step in MEN activation occurs when the Dbf2-Mob1 protein kinase complex associates with the Nud1 scaffold protein at the yeast spindle pole bodies (SPBs; centrosome equivalents) and thereby becomes activated. This requires prior priming phosphorylation of Nud1 by Cdc15 at SPBs. Cdc15 activation, in turn, requires both the Tem1 GTPase and the Polo kinase Cdc5, but how Cdc15 associates with SPBs is not well understood. We have identified a hyperactive allele of NUD1, nud1-A308T, that recruits Cdc15 to SPBs in all stages of the cell cycle in a CDC5-independent manner. This allele leads to early recruitment of Dbf2-Mob1 during metaphase and requires known Cdc15 phospho-sites on Nud1. The presence of nud1-A308T leads to loss of coupling between nuclear position and mitotic exit in cells with mispositioned spindles. Our findings highlight the importance of scaffold regulation in signaling pathways to prevent improper activation.

scholarly journals LTE1 promotes exit from mitosis by multiple mechanisms

2016 ◽  
Vol 27 (25) ◽  
pp. 3991-4001 ◽  
Author(s):  
Jill E. Falk ◽  
Ian W. Campbell ◽  
Kelsey Joyce ◽  
Jenna Whalen ◽  
Anupama Seshan ◽  
...  
Keyword(s):  
Mother Cell ◽  
Regulatory Elements ◽  
Spindle Pole ◽  
Mitotic Exit ◽  
Genome Integrity ◽  
Cell Compartment ◽  
Activating Function ◽  
Spindle Pole Bodies ◽  
Mitotic Exit Network ◽  
Spindle Position

In budding yeast, alignment of the anaphase spindle along the mother–bud axis is crucial for maintaining genome integrity. If the anaphase spindle becomes misaligned in the mother cell compartment, cells arrest in anaphase because the mitotic exit network (MEN), an essential Ras-like GTPase signaling cascade, is inhibited by the spindle position checkpoint (SPoC). Distinct localization patterns of MEN and SPoC components mediate MEN inhibition. Most components of the MEN localize to spindle pole bodies. If the spindle becomes mispositioned in the mother cell compartment, cells arrest in anaphase due to inhibition of the MEN by the mother cell–restricted SPoC kinase Kin4. Here we show that a bud-localized activating signal is necessary for full MEN activation. We identify Lte1 as this signal and show that Lte1 activates the MEN in at least two ways. It inhibits small amounts of Kin4 that are present in the bud via its central domain. An additional MEN-activating function of Lte1 is mediated by its N- and C-terminal GEF domains, which, we propose, directly activate the MEN GTPase Tem1. We conclude that control of the MEN by spindle position is exerted by both negative and positive regulatory elements that control the pathway’s GTPase activity.

scholarly journals Oscillations in Cdc14 release and sequestration reveal a circuit underlying mitotic exit

2010 ◽  
Vol 190 (2) ◽  
pp. 209-222 ◽  
Author(s):  
Romilde Manzoni ◽  
Francesca Montani ◽  
Clara Visintin ◽  
Fabrice Caudron ◽  
Andrea Ciliberto ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Feedback Loop ◽  
Mitotic Exit ◽  
Centrosome Duplication ◽  
Negative Feedback Loop ◽  
Cyclin Dependent Kinase ◽  
Bud Formation ◽  
Mitotic Exit Network ◽  
Early Anaphase ◽  
Periodic Cycles

In budding yeast, the phosphatase Cdc14 orchestrates progress through anaphase and mitotic exit, thereby resetting the cell cycle for a new round of cell division. Two consecutive pathways, Cdc fourteen early anaphase release (FEAR) and mitotic exit network (MEN), contribute to the progressive activation of Cdc14 by regulating its release from the nucleolus, where it is kept inactive by Cfi1. In this study, we show that Cdc14 activation requires the polo-like kinase Cdc5 together with either Clb–cyclin-dependent kinase (Cdk) or the MEN kinase Dbf2. Once active, Cdc14 triggers a negative feedback loop that, in the presence of stable levels of mitotic cyclins, generates periodic cycles of Cdc14 release and sequestration. Similar phenotypes have been described for yeast bud formation and centrosome duplication. A common theme emerges where events that must happen only once per cycle, although intrinsically capable of oscillations, are limited to one occurrence by the cyclin–Cdk cell cycle engine.

scholarly journals Mutual regulation of cyclin-dependent kinase and the mitotic exit network

2010 ◽  
Vol 188 (3) ◽  
pp. 351-368 ◽  
Author(s):  
Cornelia König ◽  
Hiromi Maekawa ◽  
Elmar Schiebel
Keyword(s):  
Spindle Pole Body ◽  
Spindle Pole ◽  
Mitotic Exit ◽  
Cyclin Dependent Kinase ◽  
Spatial Regulation ◽  
Daughter Cells ◽  
Pole Body ◽  
Mitotic Exit Network ◽  
Mutual Regulation ◽  
Early Anaphase

The mitotic exit network (MEN) is a spindle pole body (SPB)–associated, GTPase-driven signaling cascade that controls mitotic exit. The inhibitory Bfa1–Bub2 GTPase-activating protein (GAP) only associates with the daughter SPB (dSPB), raising the question as to how the MEN is regulated on the mother SPB (mSPB). Here, we show mutual regulation of cyclin-dependent kinase 1 (Cdk1) and the MEN. In early anaphase Cdk1 becomes recruited to the mSPB depending on the activity of the MEN kinase Cdc15. Conversely, Cdk1 negatively regulates binding of Cdc15 to the mSPB. In addition, Cdk1 phosphorylates the Mob1 protein to inhibit the activity of Dbf2–Mob1 kinase that regulates Cdc14 phosphatase. Our data revise the understanding of the spatial regulation of the MEN. Although MEN activity in the daughter cells is controlled by Bfa1–Bub2, Cdk1 inhibits MEN activity at the mSPB. Consistent with this model, only triple mutants that lack BUB2 and the Cdk1 phosphorylation sites in Mob1 and Cdc15 show mitotic exit defects.

scholarly journals Regulation of the Bfa1p–Bub2p complex at spindle pole bodies by the cell cycle phosphatase Cdc14p

2002 ◽  
Vol 157 (3) ◽  
pp. 367-379 ◽  
Author(s):  
Gislene Pereira ◽  
Claire Manson ◽  
Joan Grindlay ◽  
Elmar Schiebel
Keyword(s):  
Spindle Pole Body ◽  
Spindle Pole ◽  
Mitotic Exit ◽  
Gtpase Activating Protein ◽  
Signal Transduction Cascade ◽  
Pole Body ◽  
Spindle Pole Bodies ◽  
Short Period ◽  
Mitotic Exit Network ◽  
Early Anaphase

The budding yeast mitotic exit network (MEN) is a GTPase-driven signal transduction cascade that controls the release of the phosphatase Cdc14p from the nucleolus in anaphase and thereby drives mitotic exit. We show that Cdc14p is partially released from the nucleolus in early anaphase independent of the action of the MEN components Cdc15p, Dbf2p, and Tem1p. Upon release, Cdc14p binds to the spindle pole body (SPB) via association with the Bfa1p–Bub2p GTPase activating protein complex, which is known to regulate the activity of the G protein Tem1p. Cdc14p also interacts with this GTPase. The association of the MEN component Mob1p with the SPB acts as a marker of MEN activation. The simultaneous binding of Cdc14p and Mob1p to the SPB in early anaphase suggests that Cdc14p initially activates the MEN. In a second, later step, which coincides with mitotic exit, Cdc14p reactivates the Bfa1p–Bub2p complex by dephosphorylating Bfa1p. This inactivates the MEN and displaces Mob1p from SPBs. These data indicate that Cdc14p activates the MEN in early anaphase but later inactivates it through Bfa1p dephosphorylation and so restricts MEN activity to a short period in anaphase.

scholarly journals The Mitotic Exit Network Mob1p-Dbf2p Kinase Complex Localizes to the Nucleus and Regulates Passenger Protein Localization

2005 ◽  
Vol 16 (12) ◽  
pp. 5465-5479 ◽  
Author(s):  
Jan Stoepel ◽  
Michelle A. Ottey ◽  
Cornelia Kurischko ◽  
Philip Hieter ◽  
Francis C. Luca
Keyword(s):  
Chromatin Immunoprecipitation ◽  
Protein Localization ◽  
Mitotic Exit ◽  
Mitotic Exit Network ◽  
Chromosomal Passenger ◽  
Early Anaphase ◽  
Chromosomal Passenger Proteins ◽  
Kinetochore Region ◽  
Passenger Proteins ◽  
Passenger Protein

The Saccharomyces cerevisiae mitotic exit network (MEN) is a conserved signaling network that coordinates CDK inactivation, cytokinesis and G1 gene transcription. The MEN Cdc14p phosphatase is sequestered in the nucleolus and transiently released in early anaphase and telophase. Cdc14p mediates mitotic exit by dephosphorylating Cdk1p substrates and promoting Cdk1p inactivation. Cdc14p also regulates the localization of chromosomal passenger proteins, which redistribute from kinetochores to the mitotic spindle during anaphase. Here we present evidence that the MEN protein kinase complex Mob1p-Dbf2p localizes to mitotic nuclei and partially colocalizes with Cdc14p and kinetochore proteins. Chromatin immunoprecipitation (ChIP) experiments reveal that Mob1p, Dbf2p, and Cdc14p associate with centromere DNA and require the centromere binding protein Ndc10p for this association. We establish that Mob1p is essential for maintaining the localization of Aurora, INCENP, and Survivin chromosomal passenger proteins on anaphase spindles, whereas Cdc14p and the Mob1p-Dbf2p-activating kinase Cdc15p are required for establishing passenger protein localization on the spindle. Moreover, Mob1p, but not Cdc15p, is required for dissociating Aurora from the kinetochore region. These findings reveal kinetochores as sites for MEN signaling and implicate MEN in coordinating chromosome segregation and/or spindle integrity with mitotic exit and cytokinesis via regulation of chromosome passenger proteins.

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