Bub2 regulation of cytokinesis and septation in budding yeast

Park, Su Young; Cable, Addie E; Blair, Jessica; Stockstill, Katherine E.; Shannon, Katie B.

doi:10.1186/1471-2121-10-43

Cited by 7 publications

(10 citation statements)

References 35 publications

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“…6’ and 8’, respectively, Fig. 4C ), consistently with previous data on bub2Δ cells [ 56 ]. Thus, the TEM1-Q79L allele accelerates at least some aspects of cytokinesis without affecting cell viability.…”

Section: Resultssupporting

confidence: 91%

Asymmetry of the Budding Yeast Tem1 GTPase at Spindle Poles Is Required for Spindle Positioning But Not for Mitotic Exit

et al. 2015

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The asymmetrically dividing yeast S. cerevisiae assembles a bipolar spindle well after establishing the future site of cell division (i.e., the bud neck) and the division axis (i.e., the mother-bud axis). A surveillance mechanism called spindle position checkpoint (SPOC) delays mitotic exit and cytokinesis until the spindle is properly positioned relative to the mother-bud axis, thereby ensuring the correct ploidy of the progeny. SPOC relies on the heterodimeric GTPase-activating protein Bub2/Bfa1 that inhibits the small GTPase Tem1, in turn essential for activating the mitotic exit network (MEN) kinase cascade and cytokinesis. The Bub2/Bfa1 GAP and the Tem1 GTPase form a complex at spindle poles that undergoes a remarkable asymmetry during mitosis when the spindle is properly positioned, with the complex accumulating on the bud-directed old spindle pole. In contrast, the complex remains symmetrically localized on both poles of misaligned spindles. The mechanism driving asymmetry of Bub2/Bfa1/Tem1 in mitosis is unclear. Furthermore, whether asymmetry is involved in timely mitotic exit is controversial. We investigated the mechanism by which the GAP Bub2/Bfa1 controls GTP hydrolysis on Tem1 and generated a series of mutants leading to constitutive Tem1 activation. These mutants are SPOC-defective and invariably lead to symmetrical localization of Bub2/Bfa1/Tem1 at spindle poles, indicating that GTP hydrolysis is essential for asymmetry. Constitutive tethering of Bub2 or Bfa1 to both spindle poles impairs SPOC response but does not impair mitotic exit. Rather, it facilitates mitotic exit of MEN mutants, likely by increasing the residence time of Tem1 at spindle poles where it gets active. Surprisingly, all mutant or chimeric proteins leading to symmetrical localization of Bub2/Bfa1/Tem1 lead to increased symmetry at spindle poles of the Kar9 protein that mediates spindle positioning and cause spindle misalignment. Thus, asymmetry of the Bub2/Bfa1/Tem1 complex is crucial to control Kar9 distribution and spindle positioning during mitosis.

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Section: Resultssupporting

confidence: 91%

Asymmetry of the Budding Yeast Tem1 GTPase at Spindle Poles Is Required for Spindle Positioning But Not for Mitotic Exit

et al. 2015

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“…Interestingly, several members of the yeast spindle orientation checkpoint such as Bub2 are SCD proteins. Bub2 resides in the spindle pole body and activates the mitotic exit network once the spindle has been correctly positioned providing a link between spindle orientation and mitotic progression into cytokinesis [24,25]. The presence of an SCD in Bub2 suggests that this surveillance mechanism may also be under Tel1/Mec1 control.…”

Section: Discussionmentioning

confidence: 99%

An S/T-Q cluster domain census unveils new putative targets under Tel1/Mec1 control

Cheung

Lucas²,

Hicks

et al. 2012

BMC Genomics

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BackgroundThe cellular response to DNA damage is immediate and highly coordinated in order to maintain genome integrity and proper cell division. During the DNA damage response (DDR), the sensor kinases Tel1 and Mec1 in Saccharomyces cerevisiae and ATM and ATR in human, phosphorylate multiple mediators which activate effector proteins to initiate cell cycle checkpoints and DNA repair. A subset of kinase substrates are recognized by the S/T-Q cluster domain (SCD), which contains motifs of serine (S) or threonine (T) followed by a glutamine (Q). However, the full repertoire of proteins and pathways controlled by Tel1 and Mec1 is unknown.ResultsTo identify all putative SCD-containing proteins, we analyzed the distribution of S/T-Q motifs within verified Tel1/Mec1 targets and arrived at a unifying SCD definition of at least 3 S/T-Q within a stretch of 50 residues. This new SCD definition was used in a custom bioinformatics pipeline to generate a census of SCD-containing proteins in both yeast and human. In yeast, 436 proteins were identified, a significantly larger number of hits than were expected by chance. These SCD-containing proteins did not distribute equally across GO-ontology terms, but were significantly enriched for those involved in processes related to the DDR. We also found a significant enrichment of proteins involved in telophase and cytokinesis, protein transport and endocytosis suggesting possible novel Tel1/Mec1 targets in these pathways. In the human proteome, a wide range of similar proteins were identified, including homologs of some SCD-containing proteins found in yeast. This list also included high concentrations of proteins in the Mediator, spindle pole body/centrosome and actin cytoskeleton complexes.ConclusionsUsing a bioinformatic approach, we have generated a census of SCD-containing proteins that are involved not only in known DDR pathways but several other pathways under Tel1/Mec1 control suggesting new putative targets for these kinases.

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“…Bub2p may also be important in regulating nuclear envelope fission, given its many roles in regulating the end of the cell cycle. Overexpression of Bub2p has also been linked to cytokinesis defects (Park et al 2009). …”

Section: Discussionmentioning

confidence: 99%

Influence of the bud neck on nuclear envelope fission in Saccharomyces cerevisiae

Melloy

Rose

2017

Experimental Cell Research

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Studies have shown that nuclear envelope fission (karyokinesis) in budding yeast depends on cytokinesis, but not distinguished whether this was a direct requirement, indirect, because of cell cycle arrest, or due to bud neck-localized proteins impacting both processes. To determine the requirements for karyokinesis, we examined mutants conditionally defective for bud emergence and/or nuclear migration. The common mutant phenotype was completion of the nuclear division cycle within the mother cell, but karyokinesis did not occur. In the cdc24 swe1 mutant, at the non-permissive temperature, multiple nuclei accumulated within the unbudded cell, with connected nuclear envelopes. Upon return to the permissive temperature, the cdc24 swe1 mutant initiated bud emergence, but only the nucleus spanning the neck underwent fission suggesting that the bud neck region is important for fission initiation. The neck may be critical for either mechanical reasons, as the contractile ring might facilitate fission, or for regulatory reasons, as the site of a protein network regulating nuclear envelope fission, mitotic exit, and cytokinesis. We also found that 77–85% of pairs of septin mutant nuclei completed nuclear envelope fission. In addition, 27% of myo1Δ mutant nuclei completed karyokinesis. These data suggested that fission is not dependent on mechanical contraction at the bud neck, but was instead controlled by regulatory proteins there.

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Bub2 regulation of cytokinesis and septation in budding yeast

Cited by 7 publications

References 35 publications

Asymmetry of the Budding Yeast Tem1 GTPase at Spindle Poles Is Required for Spindle Positioning But Not for Mitotic Exit

Asymmetry of the Budding Yeast Tem1 GTPase at Spindle Poles Is Required for Spindle Positioning But Not for Mitotic Exit

An S/T-Q cluster domain census unveils new putative targets under Tel1/Mec1 control

Influence of the bud neck on nuclear envelope fission in Saccharomyces cerevisiae

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