Order of function of the budding-yeast mitotic exit-network proteins Tem1, Cdc15, Mob1, Dbf2, and Cdc5

In the budding yeast Saccharomyces cerevisiae the mitotic spindle must be positioned along the mother-bud axis to activate the mitotic exit network (MEN) in anaphase. To examine MEN proteins during mitotic exit, we imaged the MEN activators Tem1p and Cdc15p and the MEN regulator Bub2p in vivo. Quantitative live cell fluorescence microscopy demonstrated the spindle pole body that segregated into the daughter cell (dSPB) signaled mitotic exit upon penetration into the bud. Activation of mitotic exit was associated with an increased abundance of Tem1p-GFP and the localization of Cdc15p-GFP on the dSPB. In contrast, Bub2p-GFP fluorescence intensity decreased in mid-to-late anaphase on the dSPB. Therefore, MEN protein localization fluctuates to switch from Bub2p inhibition of mitotic exit to Cdc15p activation of mitotic exit. The mechanism that elevates Tem1p-GFP abundance in anaphase is specific to dSPB penetration into the bud and Dhc1p and Lte1p promote Tem1p-GFP localization. Finally, fluorescence recovery after photobleaching (FRAP) measurements revealed Tem1p-GFP is dynamic at the dSPB in late anaphase. These data suggest spindle pole penetration into the bud activates mitotic exit, resulting in Tem1p and Cdc15p persistence at the dSPB to initiate the MEN signal cascade.

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

10.1101/352427 ◽

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.

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SIN-like pathway kinases regulate the end of mitosis in the methylotrophic yeast Ogataea polymorpha

10.1101/2021.09.27.461972 ◽

2021 ◽

Author(s):

Shen Jiangyan ◽

Kaoru Takegawa ◽

Gislene Pereira ◽

Hiromi Maekawa

Keyword(s):

Budding Yeast ◽

Methylotrophic Yeast ◽

Growth Conditions ◽

Mitotic Exit ◽

Signalling Pathway ◽

Significant Delay ◽

Yeast Saccharomyces Cerevisiae ◽

Mitotic Exit Network ◽

Septation Initiation Network ◽

Ogataea Polymorpha

The Mitotic exit network (MEN) is a conserved signalling pathway essential for termination of mitosis in the budding yeast Saccharomyces cerevisiae. All MEN components are highly conserved in the methylotrophic budding yeast Ogataea polymorpha, except for Cdc15 kinase. Amongst O. polymorpha protein kinases that have some similarity to ScCdc15, only two had no other obvious homologues in S. cerevisiae and these were named OpHCD1 and OpHCD2 for homologue candidate of ScCdc15. A search in other yeast species revealed that OpHcd2 has an armadillo type fold in the C-terminal region as found in SpCdc7 kinases of the fission yeast Schizosaccharomyces pombe, which are homologues of ScCdc15; while OpHcd1 is homologous to SpSid1 kinase, a component of the Septation Initiation Network (SIN) of S. pombe not present in the MEN. Since the deletion of either OpHCD1 or OpHCD2 resulted in lethality under standard growth conditions, conditional mutants were constructed by introducing an ATP analog sensitive mutation. For OpHCD2, we constructed and used new genetic tools for O. polymorpha that combined the Tet promoter and the improved auxin-degron systems. Conditional mutants for OpHCD1 and OpHCD2 exhibited significant delay in late anaphase and defective cell separation, suggesting that both genes have roles in mitotic exit and cytokinesis. These results suggest a SIN-like signalling pathway regulates termination of mitosis in O. polymorpha and that the loss of Sid1/Hcd1 kinase in the MEN occurred relatively recently during the evolution of budding yeast.

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

Cells ◽

10.3390/cells11010046 ◽

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.

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Chromosome passenger complexes control anaphase duration and spindle elongation via a kinesin-5 brake

The Journal of Cell Biology ◽

10.1083/jcb.201011002 ◽

2011 ◽

Vol 193 (2) ◽

pp. 285-294 ◽

Cited By ~ 21

Author(s):

Daniel K. Rozelle ◽

Scott D. Hansen ◽

Kenneth B. Kaplan

Keyword(s):

Chromosome Segregation ◽

Budding Yeast ◽

Mitotic Exit ◽

Mitotic Exit Network ◽

Spindle Midzone ◽

Spindle Elongation ◽

Spindle Stability

During mitosis, chromosome passenger complexes (CPCs) exhibit a well-conserved association with the anaphase spindle and have been implicated in spindle stability. However, their precise effect on the spindle is not clear. In this paper, we show, in budding yeast, that a CPC consisting of CBF3, Bir1, and Sli15, but not Ipl1, is required for normal spindle elongation. CPC mutants slow spindle elongation through the action of the bipolar kinesins Cin8 and Kip1. The same CPC mutants that slow spindle elongation also result in the enrichment of Cin8 and Kip1 at the spindle midzone. Together, these findings argue that CPCs function to organize the spindle midzone and potentially switch motors between force generators and molecular brakes. We also find that slowing spindle elongation delays the mitotic exit network (MEN)–dependent release of Cdc14, thus delaying spindle breakdown until a minimal spindle size is reached. We propose that these CPC- and MEN-dependent mechanisms are important for coordinating chromosome segregation with spindle breakdown and mitotic exit.

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Targeted localization of Inn1, Cyk3 and Chs2 by the mitotic-exit network regulates cytokinesis in budding yeast

Journal of Cell Science ◽

10.1242/jcs.063891 ◽

2010 ◽

Vol 123 (11) ◽

pp. 1851-1861 ◽

Cited By ~ 63

Author(s):

F. Meitinger ◽

B. Petrova ◽

I. M. Lombardi ◽

D. T. Bertazzi ◽

B. Hub ◽

...

Keyword(s):

Budding Yeast ◽

Mitotic Exit ◽

Mitotic Exit Network

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Budding yeast PAK kinases regulate mitotic exit by two different mechanisms

The Journal of Cell Biology ◽

10.1083/jcb.200209097 ◽

2003 ◽

Vol 160 (6) ◽

pp. 857-874 ◽

Cited By ~ 22

Author(s):

Elena Chiroli ◽

Roberta Fraschini ◽

Alessia Beretta ◽

Mariagrazia Tonelli ◽

Giovanna Lucchini ◽

...

Keyword(s):

Cell Cycle Progression ◽

Budding Yeast ◽

Mitotic Exit ◽

Dominant Negative ◽

Anaphase Promoting Complex ◽

Gene Encoding ◽

Cycle Progression ◽

Mitotic Exit Network ◽

P21 Activated Kinase

We report the characterization of the dominant-negative CLA4t allele of the budding yeast CLA4 gene, encoding a member of the p21-activated kinase (PAK) family of protein kinases, which, together with its homologue STE20, plays an essential role in promoting budding and cytokinesis. Overproduction of the Cla4t protein likely inhibits both endogenous Cla4 and Ste20 and causes a delay in the onset of anaphase that correlates with inactivation of Cdc20/anaphase-promoting complex (APC)–dependent proteolysis of both the cyclinB Clb2 and securin. Although the precise mechanism of APC inhibition by Cla4t remains to be elucidated, our results suggest that Cla4 and Ste20 may regulate the first wave of cyclinB proteolysis mediated by Cdc20/APC, which has been shown to be crucial for activation of the mitotic exit network (MEN). We show that the Cdk1-inhibitory kinase Swe1 is required for the Cla4t-dependent delay in cell cycle progression, suggesting that it might be required to prevent full Cdc20/APC and MEN activation. In addition, inhibition of PAK kinases by Cla4t prevents mitotic exit also by a Swe1-independent mechanism impinging directly on the MEN activator Tem1.

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IQGAP and mitotic exit network (MEN) proteins are required for cytokinesis and re-polarization of the actin cytoskeleton in the budding yeast, Saccharomyces cerevisiae

European Journal of Cell Biology ◽

10.1016/j.ejcb.2006.08.001 ◽

2006 ◽

Vol 85 (11) ◽

pp. 1201-1215 ◽

Cited By ~ 21

Author(s):

Mark Corbett ◽

Yulan Xiong ◽

James R. Boyne ◽

Daniel J. Wright ◽

Ewen Munro ◽

...

Keyword(s):

Saccharomyces Cerevisiae ◽

Actin Cytoskeleton ◽

Budding Yeast ◽

Mitotic Exit ◽

Yeast Saccharomyces Cerevisiae ◽

Mitotic Exit Network

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Loss of CDC5 Function in Saccharomyces cerevisiae Leads to Defects in Swe1p Regulation and Bfa1p/Bub2p-Independent Cytokinesis

Genetics ◽

10.1093/genetics/163.1.21 ◽

2003 ◽

Vol 163 (1) ◽

pp. 21-33 ◽

Cited By ~ 1

Author(s):

Chong Jin Park ◽

Sukgil Song ◽

Philip R Lee ◽

Wenying Shou ◽

Raymond J Deshaies ◽

...

Keyword(s):

Budding Yeast ◽

Mitotic Exit ◽

Multiple Roles ◽

Growth Defect ◽

Temperature Sensitive ◽

Negative Regulators ◽

Mitotic Exit Network ◽

M Phase ◽

Phase Progression ◽

Bud Site

Abstract In many organisms, polo kinases appear to play multiple roles during M-phase progression. To provide new insights into the function of budding yeast polo kinase Cdc5p, we generated novel temperature-sensitive cdc5 mutants by mutagenizing the C-terminal domain. Here we show that, at a semipermissive temperature, the cdc5-3 mutant exhibited a synergistic bud elongation and growth defect with loss of HSL1, a component important for normal G2/M transition. Loss of SWE1, which phosphorylates and inactivates the budding yeast Cdk1 homolog Cdc28p, suppressed the cdc5-3 hsl1Δ defect, suggesting that Cdc5p functions at a point upstream of Swe1p. In addition, the cdc5-4 and cdc5-7 mutants exhibited chained cell morphologies with shared cytoplasms between the connected cell bodies, indicating a cytokinetic defect. Close examination of these mutants revealed delayed septin assembly at the incipient bud site and loosely organized septin rings at the mother-bud neck. Components in the mitotic exit network (MEN) play important roles in normal cytokinesis. However, loss of BFA1 or BUB2, negative regulators of the MEN, failed to remedy the cytokinetic defect of these mutants, indicating that Cdc5p promotes cytokinesis independently of Bfa1p and Bub2p. Thus, Cdc5p contributes to the activation of the Swe1p-dependent Cdc28p/Clb pathway, normal septin function, and cytokinesis.

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A Novel Pathway that Coordinates Mitotic Exit with Spindle Position

Molecular Biology of the Cell ◽

10.1091/mbc.e07-03-0242 ◽

2007 ◽

Vol 18 (9) ◽

pp. 3440-3450 ◽

Cited By ~ 15

Author(s):

Scott A. Nelson ◽

John A. Cooper

Keyword(s):

Molecular Mechanism ◽

Mitotic Spindle ◽

Budding Yeast ◽

Small Gtpase ◽

Mitotic Exit ◽

Signaling Cascade ◽

Biochemical Evidence ◽

Guanine Exchange Factor ◽

Mitotic Exit Network ◽

Spindle Position

In budding yeast, the spindle position checkpoint (SPC) delays mitotic exit until the mitotic spindle moves into the neck between the mother and bud. This checkpoint works by inhibiting the mitotic exit network (MEN), a signaling cascade initiated and controlled by Tem1, a small GTPase. Tem1 is regulated by a putative guanine exchange factor, Lte1, but the function and regulation of Lte1 remains poorly understood. Here, we identify novel components of the checkpoint that operate upstream of Lte1. We present genetic evidence in agreement with existing biochemical evidence for the molecular mechanism of a pathway that links microtubule-cortex interactions with Lte1 and mitotic exit. Each component of this pathway is required for the spindle position checkpoint to delay mitotic exit until the spindle is positioned correctly.

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