The Experts below are selected from a list of 7014 Experts worldwide ranked by ideXlab platform
Frank Uhlmann - One of the best experts on this subject based on the ideXlab platform.
-
Nur1 dephosphorylation confers positive feedback to Mitotic Exit phosphatase activation in budding yeast.
PLoS genetics, 2015Co-Authors: Molly Godfrey, Thomas Kuilman, Frank UhlmannAbstract:Substrate dephosphorylation by the cyclin-dependent kinase (Cdk)-opposing phosphatase, Cdc14, is vital for many events during budding yeast Mitotic Exit. Cdc14 is sequestered in the nucleolus through inhibitory binding to Net1, from which it is released in anaphase following Net1 phosphorylation. Initial Net1 phosphorylation depends on Cdk itself, in conjunction with proteins of the Cdc14 Early Anaphase Release (FEAR) network. Later on, the Mitotic Exit Network (MEN) signaling cascade maintains Cdc14 release. An important unresolved question is how Cdc14 activity can increase in early anaphase, while Cdk activity, that is required for Net1 phosphorylation, decreases and the MEN is not yet active. Here we show that the nuclear rim protein Nur1 interacts with Net1 and, in its Cdk phosphorylated form, inhibits Cdc14 release. Nur1 is dephosphorylated by Cdc14 in early anaphase, relieving the inhibition and promoting further Cdc14 release. Nur1 dephosphorylation thus describes a positive feedback loop in Cdc14 phosphatase activation during Mitotic Exit, required for faithful chromosome segregation and completion of the cell division cycle.
-
A Quantitative Model for Ordered Cdk Substrate Dephosphorylation during Mitotic Exit
Cell, 2011Co-Authors: Céline Bouchoux, Frank UhlmannAbstract:Summary After sister chromatid splitting at anaphase onset, Exit from mitosis comprises an ordered series of events. Dephosphorylation of numerous Mitotic substrates, which were phosphorylated by cyclin-dependent kinase (Cdk), is thought to bring about Mitotic Exit, but how temporal ordering of Mitotic Exit events is achieved is poorly understood. Here, we show, using budding yeast, that dephosphorylation of Cdk substrates involved in sequential Mitotic Exit events occurs with ordered timing. We test different models of how ordering might be achieved by modulating Cdk and Cdk-counteracting phosphatase Cdc14 activities in vivo, as well as by kinetic analysis of Cdk substrate phosphorylation and dephosphorylation in vitro. Our results suggest that the gradual change of the phosphatase to kinase ratio over the course of Mitotic Exit is read out by Cdk substrates that respond by dephosphorylation at distinct thresholds. This provides an example and a mechanistic explanation for a quantitative model of cell-cycle progression.
-
Mitotic Exit in mammalian cells
Molecular systems biology, 2009Co-Authors: Orsolya Kapuy, Frank Uhlmann, Bela NovakAbstract:Mol Syst Biol. 5: 324 The eukaryotic cell cycle comprises an ordered series of events that are controlled by the oscillating activity of cyclin‐dependent kinases (Cdks). The unidirectionality of cell cycle transitions is fundamental for successful completion of this cycle. Increasing activity of Cdk1 in complex with its regulatory cyclin, CycB, drives entry into mitosis, whereas subsequent CycB proteolysis promotes Exit from mitosis and return of the cell cycle to interphase (Morgan, 2007). It is a commonplace view that the thermodynamically irreversible nature of cyclin proteolysis underlies the unidirectionality of Mitotic Exit (Lodish et al , 2004). However, in a biological system, steady‐state levels of proteins (including CycB) result from the relative rates of protein destruction and de novo synthesis—itself a thermodynamically irreversible reaction. We have, therefore, suggested that proteolysis is insufficient to explain the irreversibility of Mitotic Exit. Rather, irreversibiltiy requires systems‐level feedback that locks the cell cycle machinery in a G1 state, with low Cdk1–CycB activity, after Exiting from mitosis (Novak et al , 2007). Proof of principle for this idea has come from experiments in budding yeast (Lopez‐Aviles et al , 2009). These show that Mitotic Exit is driven by cyclin proteolysis but becomes irreversible only when a double‐negative feedback loop consisting of the stoichiometric Cdk1 inhibitor, Sic1, is engaged. Here we argue that systems‐level feedback is likely to explain the irreversibility of Mitotic Exit in most, if not all, eukaryotes. In two recent studies, Gorbsky and coworkers have investigated the irreversibility of Mitotic Exit in …
-
irreversibility of Mitotic Exit is the consequence of systems level feedback
Nature, 2009Co-Authors: Sandra Lopezaviles, Bela Novak, Orsolya Kapuy, Frank UhlmannAbstract:The eukaryotic cell cycle comprises an ordered series of events orchestrated by cyclin-dependent kinases (Cdks), with unidirectional cell-cycle transitions being required for its successful completion. Proteolytic degradation of cyclins has been assumed to be responsible for the irreversible transitions. Here, the contribution of cyclin proteolysis to the irreversibility of Mitotic Exit has been examined with a combination of experiments in budding yeast and mathematical modelling. Although forced cyclin degradation can drive Mitotic Exit, it is not sufficient for irreversibility, due to the re-synthesis of cyclin. Mitotic Exit becomes irreversible only after longer periods of cyclin degradation and activation of a double negative feedback loop involving the Cdk inhibitor Sic1. The eukaryotic cell cycle comprises an ordered series of events orchestrated by cyclin-dependent kinases (Cdks), with unidirectional cell-cycle transitions being required for its successful completion. Proteolytic degradation of cyclins has been assumed to be responsible for the irreversible transitions, but here it is shown that, although forced cyclin degradation can drive Mitotic Exit, the re-synthesis of cyclin means that this is not sufficient for irreversibility. Rather, Mitotic Exit only become irreversible after activation of a double-negative feedback loop. The eukaryotic cell cycle comprises an ordered series of events, orchestrated by the activity of cyclin-dependent kinases (Cdks), leading from chromosome replication during S phase to their segregation in mitosis. The unidirectionality of cell-cycle transitions is fundamental for the successful completion of this cycle. It is thought that irrevocable proteolytic degradation of key cell-cycle regulators makes cell-cycle transitions irreversible, thereby enforcing directionality1,2,3. Here we have experimentally examined the contribution of cyclin proteolysis to the irreversibility of Mitotic Exit, the transition from high Mitotic Cdk activity back to low activity in G1. We show that forced cyclin destruction in Mitotic budding yeast cells efficiently drives Mitotic Exit events. However, these remain reversible after termination of cyclin proteolysis, with recovery of the Mitotic state and cyclin levels. Mitotic Exit becomes irreversible only after longer periods of cyclin degradation, owing to activation of a double-negative feedback loop involving the Cdk inhibitor Sic1 (refs 4, 5). Quantitative modelling suggests that feedback is required to maintain low Cdk activity and to prevent cyclin resynthesis. Our findings demonstrate that the unidirectionality of Mitotic Exit is not the consequence of proteolysis but of systems-level feedback required to maintain the cell cycle in a new stable state.
-
Irreversibility of Mitotic Exit is the consequence of systems-level feedback
Nature, 2009Co-Authors: Sandra López-avilés, Bela Novak, Orsolya Kapuy, Frank UhlmannAbstract:The eukaryotic cell cycle comprises an ordered series of events, orchestrated by the activity of cyclin-dependent kinases (Cdks), leading from chromosome replication during S phase to their segregation in mitosis. The unidirectionality of cell-cycle transitions is fundamental for the successful completion of this cycle. It is thought that irrevocable proteolytic degradation of key cell-cycle regulators makes cell-cycle transitions irreversible, thereby enforcing directionality. Here we have experimentally examined the contribution of cyclin proteolysis to the irreversibility of Mitotic Exit, the transition from high Mitotic Cdk activity back to low activity in G1. We show that forced cyclin destruction in Mitotic budding yeast cells efficiently drives Mitotic Exit events. However, these remain reversible after termination of cyclin proteolysis, with recovery of the Mitotic state and cyclin levels. Mitotic Exit becomes irreversible only after longer periods of cyclin degradation, owing to activation of a double-negative feedback loop involving the Cdk inhibitor Sic1 (refs 4, 5). Quantitative modelling suggests that feedback is required to maintain low Cdk activity and to prevent cyclin resynthesis. Our findings demonstrate that the unidirectionality of Mitotic Exit is not the consequence of proteolysis but of systems-level feedback required to maintain the cell cycle in a new stable state.
Bela Novak - One of the best experts on this subject based on the ideXlab platform.
-
a pp2a b55 recognition signal controls substrate dephosphorylation kinetics during Mitotic Exit
Journal of Cell Biology, 2016Co-Authors: Michael J Cundell, Lukas Hutter, Ricardo Nunes Bastos, Elena Poser, James Holder, Shabaz Mohammed, Bela Novak, Francis A BarrAbstract:PP2A-B55 is one of the major phosphatases regulating cell division. Despite its importance for temporal control during Mitotic Exit, how B55 substrates are recognized and differentially dephosphorylated is unclear. Using phosphoproteomics combined with kinetic modeling to extract B55-dependent rate constants, we have systematically identified B55 substrates and assigned their temporal order in Mitotic Exit. These substrates share a bipartite polybasic recognition determinant (BPR) flanking a Cdk1 phosphorylation site. Experiments and modeling show that dephosphorylation rate is encoded into B55 substrates, including its inhibitor ENSA, by cooperative action of basic residues within the BPR. A complementary acidic surface on B55 decodes this signal, supporting a cooperative electrostatic mechanism for substrate selection. A further level of specificity is encoded into B55 substrates because B55 displays selectivity for phosphothreonine. These simple biochemical properties, combined with feedback control of B55 activity by the phosphoserine-containing substrate/inhibitor ENSA, can help explain the temporal sequence of events during Exit from mitosis.
-
pp2a b55 and fcp1 regulate greatwall and ensa dephosphorylation during Mitotic Exit
PLOS Genetics, 2014Co-Authors: Nadia Hegarat, Bela Novak, Clare Vesely, P K Vinod, Cory A Ocasio, Nisha Peter, Julian Gannon, Antony W Oliver, Helfrid HocheggerAbstract:Entry into mitosis is triggered by activation of Cdk1 and inactivation of its counteracting phosphatase PP2A/B55. Greatwall kinase inactivates PP2A/B55 via its substrates Ensa and ARPP19. Both Greatwall and Ensa/ARPP19 are regulated by phosphorylation, but the dynamic regulation of Greatwall activity and the phosphatases that control Greatwall kinase and its substrates are poorly understood. To address these questions we applied a combination of mathematical modelling and experiments using phospho-specific antibodies to monitor Greatwall, Ensa/ARPP19 and Cdk substrate phosphorylation during Mitotic entry and Exit. We demonstrate that PP2A/B55 is required for Gwl dephosphorylation at the essential Cdk site Thr194. Ensa/ARPP19 dephosphorylation is mediated by the RNA Polymerase II carboxy terminal domain phosphatase Fcp1. Surprisingly, inhibition or depletion of neither Fcp1 nor PP2A appears to block dephosphorylation of the bulk of Mitotic Cdk1 substrates during Mitotic Exit. Taken together our results suggest a hierarchy of phosphatases coordinating Greatwall, Ensa/ARPP19 and Cdk substrate dephosphorylation during Mitotic Exit.
-
Mitotic Exit in mammalian cells
Molecular systems biology, 2009Co-Authors: Orsolya Kapuy, Frank Uhlmann, Bela NovakAbstract:Mol Syst Biol. 5: 324 The eukaryotic cell cycle comprises an ordered series of events that are controlled by the oscillating activity of cyclin‐dependent kinases (Cdks). The unidirectionality of cell cycle transitions is fundamental for successful completion of this cycle. Increasing activity of Cdk1 in complex with its regulatory cyclin, CycB, drives entry into mitosis, whereas subsequent CycB proteolysis promotes Exit from mitosis and return of the cell cycle to interphase (Morgan, 2007). It is a commonplace view that the thermodynamically irreversible nature of cyclin proteolysis underlies the unidirectionality of Mitotic Exit (Lodish et al , 2004). However, in a biological system, steady‐state levels of proteins (including CycB) result from the relative rates of protein destruction and de novo synthesis—itself a thermodynamically irreversible reaction. We have, therefore, suggested that proteolysis is insufficient to explain the irreversibility of Mitotic Exit. Rather, irreversibiltiy requires systems‐level feedback that locks the cell cycle machinery in a G1 state, with low Cdk1–CycB activity, after Exiting from mitosis (Novak et al , 2007). Proof of principle for this idea has come from experiments in budding yeast (Lopez‐Aviles et al , 2009). These show that Mitotic Exit is driven by cyclin proteolysis but becomes irreversible only when a double‐negative feedback loop consisting of the stoichiometric Cdk1 inhibitor, Sic1, is engaged. Here we argue that systems‐level feedback is likely to explain the irreversibility of Mitotic Exit in most, if not all, eukaryotes. In two recent studies, Gorbsky and coworkers have investigated the irreversibility of Mitotic Exit in …
-
irreversibility of Mitotic Exit is the consequence of systems level feedback
Nature, 2009Co-Authors: Sandra Lopezaviles, Bela Novak, Orsolya Kapuy, Frank UhlmannAbstract:The eukaryotic cell cycle comprises an ordered series of events orchestrated by cyclin-dependent kinases (Cdks), with unidirectional cell-cycle transitions being required for its successful completion. Proteolytic degradation of cyclins has been assumed to be responsible for the irreversible transitions. Here, the contribution of cyclin proteolysis to the irreversibility of Mitotic Exit has been examined with a combination of experiments in budding yeast and mathematical modelling. Although forced cyclin degradation can drive Mitotic Exit, it is not sufficient for irreversibility, due to the re-synthesis of cyclin. Mitotic Exit becomes irreversible only after longer periods of cyclin degradation and activation of a double negative feedback loop involving the Cdk inhibitor Sic1. The eukaryotic cell cycle comprises an ordered series of events orchestrated by cyclin-dependent kinases (Cdks), with unidirectional cell-cycle transitions being required for its successful completion. Proteolytic degradation of cyclins has been assumed to be responsible for the irreversible transitions, but here it is shown that, although forced cyclin degradation can drive Mitotic Exit, the re-synthesis of cyclin means that this is not sufficient for irreversibility. Rather, Mitotic Exit only become irreversible after activation of a double-negative feedback loop. The eukaryotic cell cycle comprises an ordered series of events, orchestrated by the activity of cyclin-dependent kinases (Cdks), leading from chromosome replication during S phase to their segregation in mitosis. The unidirectionality of cell-cycle transitions is fundamental for the successful completion of this cycle. It is thought that irrevocable proteolytic degradation of key cell-cycle regulators makes cell-cycle transitions irreversible, thereby enforcing directionality1,2,3. Here we have experimentally examined the contribution of cyclin proteolysis to the irreversibility of Mitotic Exit, the transition from high Mitotic Cdk activity back to low activity in G1. We show that forced cyclin destruction in Mitotic budding yeast cells efficiently drives Mitotic Exit events. However, these remain reversible after termination of cyclin proteolysis, with recovery of the Mitotic state and cyclin levels. Mitotic Exit becomes irreversible only after longer periods of cyclin degradation, owing to activation of a double-negative feedback loop involving the Cdk inhibitor Sic1 (refs 4, 5). Quantitative modelling suggests that feedback is required to maintain low Cdk activity and to prevent cyclin resynthesis. Our findings demonstrate that the unidirectionality of Mitotic Exit is not the consequence of proteolysis but of systems-level feedback required to maintain the cell cycle in a new stable state.
-
Irreversibility of Mitotic Exit is the consequence of systems-level feedback
Nature, 2009Co-Authors: Sandra López-avilés, Bela Novak, Orsolya Kapuy, Frank UhlmannAbstract:The eukaryotic cell cycle comprises an ordered series of events, orchestrated by the activity of cyclin-dependent kinases (Cdks), leading from chromosome replication during S phase to their segregation in mitosis. The unidirectionality of cell-cycle transitions is fundamental for the successful completion of this cycle. It is thought that irrevocable proteolytic degradation of key cell-cycle regulators makes cell-cycle transitions irreversible, thereby enforcing directionality. Here we have experimentally examined the contribution of cyclin proteolysis to the irreversibility of Mitotic Exit, the transition from high Mitotic Cdk activity back to low activity in G1. We show that forced cyclin destruction in Mitotic budding yeast cells efficiently drives Mitotic Exit events. However, these remain reversible after termination of cyclin proteolysis, with recovery of the Mitotic state and cyclin levels. Mitotic Exit becomes irreversible only after longer periods of cyclin degradation, owing to activation of a double-negative feedback loop involving the Cdk inhibitor Sic1 (refs 4, 5). Quantitative modelling suggests that feedback is required to maintain low Cdk activity and to prevent cyclin resynthesis. Our findings demonstrate that the unidirectionality of Mitotic Exit is not the consequence of proteolysis but of systems-level feedback required to maintain the cell cycle in a new stable state.
Satoshi Yoshida - One of the best experts on this subject based on the ideXlab platform.
-
Inhibition of Cdc42 during Mitotic Exit is required for cytokinesis
The Journal of cell biology, 2013Co-Authors: Benjamin D. Atkins, Daniel J Lew, Satoshi Yoshida, Koji Saito, David PellmanAbstract:The role of Cdc42 and its regulation during cytokinesis is not well understood. Using biochemical and imaging approaches in budding yeast, we demonstrate that Cdc42 activation peaks during the G1/S transition and during anaphase but drops during Mitotic Exit and cytokinesis. Cdc5/Polo kinase is an important upstream cell cycle regulator that suppresses Cdc42 activity. Failure to down-regulate Cdc42 during Mitotic Exit impairs the normal localization of key cytokinesis regulators—Iqg1 and Inn1—at the division site, and results in an abnormal septum. The effects of Cdc42 hyperactivation are largely mediated by the Cdc42 effector p21-activated kinase Ste20. Inhibition of Cdc42 and related Rho guanosine triphosphatases may be a general feature of cytokinesis in eukaryotes.
-
Spatial regulation of Cdc55–PP2A by Zds1/Zds2 controls Mitotic entry and Mitotic Exit in budding yeast
The Journal of cell biology, 2011Co-Authors: Valentina Rossio, Satoshi YoshidaAbstract:Budding yeast CDC55 encodes a regulatory B subunit of the PP2A (protein phosphatase 2A), which plays important roles in Mitotic entry and Mitotic Exit. The spatial and temporal regulation of PP2A is poorly understood, although recent studies demonstrated that the conserved proteins Zds1 and Zds2 stoichiometrically bind to Cdc55–PP2A and regulate it in a complex manner. Zds1/Zds2 promote Cdc55–PP2A function for Mitotic entry, whereas Zds1/Zds2 inhibit Cdc55–PP2A function during Mitotic Exit. In this paper, we propose that Zds1/Zds2 primarily control Cdc55 localization. Cortical and cytoplasmic localization of Cdc55 requires Zds1/Zds2, and Cdc55 accumulates in the nucleus in the absence of Zds1/Zds2. By genetically manipulating the nucleocytoplasmic distribution of Cdc55, we showed that Cdc55 promotes Mitotic entry when in the cytoplasm. On the other hand, nuclear Cdc55 prevents Mitotic Exit. Our analysis defines the long-sought molecular function for the zillion different screens family proteins and reveals the importance of the regulation of PP2A localization for proper Mitotic progression.
-
spatial regulation of cdc55 pp2a by zds1 zds2 controls Mitotic entry and Mitotic Exit in budding yeast
Journal of Cell Biology, 2011Co-Authors: Valentina Rossio, Satoshi YoshidaAbstract:Budding yeast CDC55 encodes a regulatory B subunit of the PP2A (protein phosphatase 2A), which plays important roles in Mitotic entry and Mitotic Exit. The spatial and temporal regulation of PP2A is poorly understood, although recent studies demonstrated that the conserved proteins Zds1 and Zds2 stoichiometrically bind to Cdc55–PP2A and regulate it in a complex manner. Zds1/Zds2 promote Cdc55–PP2A function for Mitotic entry, whereas Zds1/Zds2 inhibit Cdc55–PP2A function during Mitotic Exit. In this paper, we propose that Zds1/Zds2 primarily control Cdc55 localization. Cortical and cytoplasmic localization of Cdc55 requires Zds1/Zds2, and Cdc55 accumulates in the nucleus in the absence of Zds1/Zds2. By genetically manipulating the nucleocytoplasmic distribution of Cdc55, we showed that Cdc55 promotes Mitotic entry when in the cytoplasm. On the other hand, nuclear Cdc55 prevents Mitotic Exit. Our analysis defines the long-sought molecular function for the zillion different screens family proteins and reveals the importance of the regulation of PP2A localization for proper Mitotic progression.
-
Ras recruits Mitotic Exit regulator Lte1 to the bud cortex in budding yeast
The Journal of cell biology, 2003Co-Authors: Satoshi Yoshida, Ryuji Ichihashi, Akio Toh-eAbstract:ACdc25 family protein Lte1 (low temperature essential) is essential for Mitotic Exit at a lowered temperature and has been presumed to be a guanine nucleotide exchange factor (GEF) for a small GTPase Tem1, which is a key regulator of Mitotic Exit. We found that Lte1 physically associates with Ras2-GTP both in vivo and in vitro and that the Cdc25 homology domain (CHD) of Lte1 is essential for the interaction with Ras2. Furthermore, we found that the proper localization of Lte1 to the bud cortex is dependent on active Ras and that the overexpression of a derivative of Lte1 without the CHD suppresses defects in Mitotic Exit of a Δlte1 mutant and a Δras1 Δras2 mutant. These results suggest that Lte1 is a downstream effector protein of Ras in Mitotic Exit and that the Ras GEF domain of Lte1 is not essential for Mitotic Exit but required for its localization.
Don W Cleveland - One of the best experts on this subject based on the ideXlab platform.
-
TRIP13 and APC15 drive Mitotic Exit by turnover of interphase- and unattached kinetochore-produced MCC
Nature Communications, 2018Co-Authors: Dong-hyun Kim, Joo Seok Han, Peter Ly, Qiaozhen Ye, Kyungjae Myung, Moira A. Mcmahon, Kevin D. Corbett, Don W ClevelandAbstract:The Mitotic checkpoint ensures accurate chromosome segregation through assembly of the Mitotic checkpoint complex (MCC), a soluble inhibitor of the anaphase-promoting complex/cyclosome (APC/C) produced by unattached kinetochores. MCC is also assembled during interphase by Mad1/Mad2 bound at nuclear pores, thereby preventing premature Mitotic Exit prior to kinetochore maturation and checkpoint activation. Using degron tagging to rapidly deplete the AAA+ ATPase TRIP13, we show that its catalytic activity is required to maintain a pool of open-state Mad2 for MCC assembly, thereby supporting Mitotic checkpoint activation, but is also required for timely Mitotic Exit through catalytic disassembly of MCC. Strikingly, combining TRIP13 depletion with elimination of APC15-dependent Cdc20 ubiquitination/degradation results in a complete inability to Exit mitosis, even when MCC assembly at unattached kinetochores is prevented. Thus, Mitotic Exit requires MCC produced either in interphase or mitosis to be disassembled by TRIP13-catalyzed removal of Mad2 or APC15-driven ubiquitination/degradation of its Cdc20 subunit.The Mitotic checkpoint complex (MCC) is assembled during both mitosis and interphase. Here, the authors use auxin-inducible degron tags to rapidly degrade TRIP13 and find that Mitotic Exit requires MCC disassembly by TRIP13-catalyzed removal of Mad2 or APC1-driven ubiquitination of Cdc20.
-
TRIP13 and APC15 drive Mitotic Exit by turnover of interphase- and unattached kinetochore-produced MCC.
Nature communications, 2018Co-Authors: Dong-hyun Kim, Joo Seok Han, Kyungjae Myung, Moira A. Mcmahon, Kevin D. Corbett, Don W ClevelandAbstract:The Mitotic checkpoint ensures accurate chromosome segregation through assembly of the Mitotic checkpoint complex (MCC), a soluble inhibitor of the anaphase-promoting complex/cyclosome (APC/C) produced by unattached kinetochores. MCC is also assembled during interphase by Mad1/Mad2 bound at nuclear pores, thereby preventing premature Mitotic Exit prior to kinetochore maturation and checkpoint activation. Using degron tagging to rapidly deplete the AAA+ ATPase TRIP13, we show that its catalytic activity is required to maintain a pool of open-state Mad2 for MCC assembly, thereby supporting Mitotic checkpoint activation, but is also required for timely Mitotic Exit through catalytic disassembly of MCC. Strikingly, combining TRIP13 depletion with elimination of APC15-dependent Cdc20 ubiquitination/degradation results in a complete inability to Exit mitosis, even when MCC assembly at unattached kinetochores is prevented. Thus, Mitotic Exit requires MCC produced either in interphase or mitosis to be disassembled by TRIP13-catalyzed removal of Mad2 or APC15-driven ubiquitination/degradation of its Cdc20 subunit.
-
TRIP13 and APC15 drive Mitotic Exit by turnover of interphase- and unattached kinetochore-produced MCC
NATURE PUBLISHING GROUP, 2018Co-Authors: Dong-hyun Kim, Joo Seok Han, Kyungjae Myung, Moira A. Mcmahon, Kevin D. Corbett, Don W ClevelandAbstract:The Mitotic checkpoint ensures accurate chromosome segregation through assembly of the Mitotic checkpoint complex (MCC), a soluble inhibitor of the anaphase-promoting complex/cyclosome (APC/C) produced by unattached kinetochores. MCC is also assembled during interphase by Mad1/Mad2 bound at nuclear pores, thereby preventing premature Mitotic Exit prior to kinetochore maturation and checkpoint activation. Using degron tagging to rapidly deplete the AAA+ ATPase TRIP13, we show that its catalytic activity is required to maintain a pool of open-state Mad2 for MCC assembly, thereby supporting Mitotic checkpoint activation, but is also required for timely Mitotic Exit through catalytic disassembly of MCC. Strikingly, combining TRIP13 depletion with elimination of APC15-dependent Cdc20 ubiquitination/degradation results in a complete inability to Exit mitosis, even when MCC assembly at unattached kinetochores is prevented. Thus, Mitotic Exit requires MCC produced either in interphase or mitosis to be disassembled by TRIP13-catalyzed removal of Mad2 or APC15-driven ubiquitination/degradation of its Cdc20 subunit. © The Author(s) 201
Ethel Queralt - One of the best experts on this subject based on the ideXlab platform.
-
Regulation of Mitotic Exit in Saccharomyces cerevisiae
Methods in molecular biology (Clifton N.J.), 2016Co-Authors: Barbara Baro, Ethel Queralt, Fernando Monje-casasAbstract:The Mitotic Exit Network (MEN) is an essential signaling pathway, closely related to the Hippo pathway in mammals, which promotes Mitotic Exit and initiates cytokinesis in the budding yeast Saccharomyces cerevisiae. Here, we summarize the current knowledge about the MEN components and their regulation.
-
Mitotic Exit Function of Polo-like Kinase Cdc5 Is Dependent on Sequential Activation by Cdk1
Cell reports, 2016Co-Authors: Jose-antonio Rodriguez-rodriguez, Yolanda Moyano, Soraya Játiva, Ethel QueraltAbstract:To complete mitosis, Saccharomyces cerevisiae needs to activate the Mitotic phosphatase Cdc14. Two pathways contribute to Cdc14 regulation: FEAR (Cdc14 early anaphase release) and MEN (Mitotic Exit network). Cdc5 polo-like kinase was found to be an important Mitotic Exit component. However, its specific role in Mitotic Exit regulation and its involvement in Cdc14 release remain unclear. Here, we provide insight into the mechanism by which Cdc5 contributes to the timely release of Cdc14. Our genetic and biochemical data indicate that Cdc5 acts in parallel with MEN during anaphase. This MEN-independent Cdc5 function requires active separase and activation by Cdk1-dependent phosphorylation. Cdk1 first phosphorylates Cdc5 to activate it in early anaphase, and then, in late anaphase, further phosphorylation of Cdc5 by Cdk1 is needed to promote its MEN-related functions.
-
Cdk-counteracting phosphatases unlock Mitotic Exit.
Current opinion in cell biology, 2008Co-Authors: Ethel Queralt, Frank UhlmannAbstract:Entry into mitosis of the eukaryotic cell cycle is driven by rising cyclin-dependent kinase (Cdk) activity. During Exit from mitosis, Cdk activity must again decline. Cdk downregulation by itself, however, is not able to guide Mitotic Exit, if not a phosphatase reverses Mitotic Cdk phosphorylation events. In budding yeast, this role is played by the Cdc14 phosphatase. We are gaining an increasingly detailed picture of its regulation during anaphase, and of the way it orchestrates ordered progression through mitosis. Much less is known about protein dephosphorylation during Mitotic Exit in organisms other than budding yeast, but evidence is now mounting for crucial contributions of regulated phosphatases also in metazoan cells.
-
Mitotic Exit in two dimensions.
Journal of theoretical biology, 2007Co-Authors: Attila Tóth, Ethel Queralt, Frank Uhlmann, Bela NovakAbstract:Metaphase of mitosis is brought about in all eukaryotes by activation of cylin-dependent kinase (Cdk1), whereas Exit from mitosis requires down-regulation of Cdk1 activity and dephosphorylation of its target proteins. In budding yeast, the completion of Mitotic Exit requires the release and activation of the Cdc14 protein-phosphatase, which is kept inactive in the nucleolus during most of the cell cycle. Activation of Cdc14 is controlled by two regulatory networks called FEAR (Cdc fourteen early anaphase release) and MEN (Mitotic Exit network). We have shown recently that the anaphase promoting protease (separase) is essential for Cdc14 activation, thereby it makes Mitotic Exit dependent on execution of anaphase. Based on this finding, we have proposed a new model for Mitotic Exit in budding yeast. Here we explain the essence of the model by phaseplane analysis, which reveals two underlying bistable switches in the regulatory network. One bistable switch is caused by mutual activation (positive feedback) between Cdc14 activating MEN and Cdc14 itself. The mitosis-inducing Cdk1 activity inhibits the activation of this positive feedback loop and thereby controlling this switch. The other irreversible switch is generated by a double-negative feedback (mutual antagonism) between mitosis inducing Cdk1 activity and its degradation machinery (APC(Cdh1)). The Cdc14 phosphatase helps turning this switch in favor of APC(Cdh1) side. Both of these bistable switches have characteristic thresholds, the first one for Cdk1 activity, while the second for Cdc14 activity. We show that the physiological behaviors of certain cell cycle mutants are suggestive for those Cdk1 and Cdc14 thresholds. The two bistable switches turn on in a well-defined order. In this paper, we explain how the activation of Cdc20 (which causes the activation of separase and a decrease of Cdk1 kinase activity) provides an initial trigger for the activation of the MEN-Cdc14 positive feedback loops, which in turn, flips the second irreversible Cdk-APC(Cdh1) switch on the APC(Cdh1) side).
-
Downregulation of PP2ACdc55 Phosphatase by Separase Initiates Mitotic Exit in Budding Yeast
Cell, 2006Co-Authors: Ethel Queralt, Bela Novak, Chris Lehane, Frank UhlmannAbstract:After anaphase, the high Mitotic cyclin-dependent kinase (Cdk) activity is downregulated to promote Exit from mitosis. To this end, in the budding yeast S. cerevisiae, the Cdk counteracting phosphatase Cdc14 is activated. In metaphase, Cdc14 is kept inactive in the nucleolus by its inhibitor Net1. During anaphase, Cdk- and Polo-dependent phosphorylation of Net1 is thought to release active Cdc14. How Net1 is phosphorylated specifically in anaphase, when Mitotic kinase activity starts to decline, has remained unexplained. Here, we show that PP2A(Cdc55) phosphatase keeps Net1 underphosphorylated in metaphase. The sister chromatid-separating protease separase, activated at anaphase onset, interacts with and downregulates PP2A(Cdc55), thereby facilitating Cdk-dependent Net1 phosphorylation. PP2A(Cdc55) downregulation also promotes phosphorylation of Bfa1, contributing to activation of the "Mitotic Exit network" that sustains Cdc14 as Cdk activity declines. These findings allow us to present a new quantitative model for Mitotic Exit in budding yeast.