scholarly journals Protein Phosphatase 1 in association with Bud14 inhibits mitotic exit in Saccharomyces cerevisiae

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Dilara Kocakaplan ◽  
Hüseyin Karaburk ◽  
Cansu Dilege ◽  
Idil Kirdök ◽  
Şeyma Nur Bektaş ◽  
...  
Keyword(s):  
Protein Phosphatase ◽  
Regulatory Protein ◽  
Mitotic Exit ◽  
Protein Phosphatase 1 ◽  
Effector Protein ◽  
Checkpoint Response ◽  
Correct Orientation ◽  
Surveillance Mechanism ◽  
Spindle Position

Mitotic exit in budding yeast is dependent on correct orientation of the mitotic spindle along the cell polarity axis. When accurate positioning of the spindle fails, a surveillance mechanism named the Spindle Position Checkpoint (SPOC) prevents cells from exiting mitosis. Mutants with a defective SPOC become multinucleated and lose their genomic integrity. Yet, a comprehensive understanding of the SPOC mechanism is missing. In this study, we identified the type 1 protein phosphatase, Glc7, in association with its regulatory protein Bud14 as a novel checkpoint component. We further showed that Glc7-Bud14 promotes dephosphorylation of the SPOC effector protein Bfa1. Our results suggest a model in which two mechanisms act in parallel for a robust checkpoint response: first, the SPOC kinase Kin4 isolates Bfa1 away from the inhibitory kinase Cdc5 and second, Glc7-Bud14 dephosphorylates Bfa1 to fully activate the checkpoint effector.

scholarly journals Protein Phosphatase 1 in association with Bud14 inhibits mitotic exit in Saccharomyces cerevisiae

2020 ◽  
Author(s):  
Dilara Kocakaplan ◽  
Hüseyin Karabürk ◽  
Cansu Dilege ◽  
Idil Kirdok ◽  
Şeyma Nur Erkan ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mitotic Spindle ◽  
Protein Phosphatase ◽  
Budding Yeast ◽  
Mitotic Exit ◽  
Protein Phosphatase 1 ◽  
Inhibitory Function ◽  
Surveillance Mechanism ◽  
Spindle Position

AbstractSaccharomyces cerevisiae, also known as the budding yeast, orients and elongates its mitotic spindle along its polarity axis in order to segregate one copy of its genomic DNA to the daughter cell. When accurate positioning of the mitotic spindle fails, a surveillance mechanism, named the Spindle Position Checkpoint (SPOC), prevents cells from exiting mitosis unless the spindle orientation is corrected. Mutants with a defective SPOC loss their genomic integrity, become multiploid and aneuploid. Thus, SPOC is a crucial checkpoint for the budding yeast. Yet, a comprehensive understanding of how the SPOC mechanism works is missing. In this study, we identified Bud14 as a novel checkpoint protein. We showed that the mitotic exit inhibitory function of Bud14 requires its association with the type 1 protein phosphatase, Glc7. Our data indicate that Glc7-Bud14 promotes dephosphorylation of the SPOC effector protein Bfa1. Our results support a model in which Glc7-Bud14 works parallel to the SPOC kinase Kin4 in inhibiting mitotic exit.

scholarly journals The Ki-67 and RepoMan mitotic phosphatases assemble via an identical, yet novel mechanism

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Ganesan Senthil Kumar ◽  
Ezgi Gokhan ◽  
Sofie De Munter ◽  
Mathieu Bollen ◽  
Paola Vagnarelli ◽  
...  
Keyword(s):  
Protein Phosphatase ◽  
Mitotic Chromosome ◽  
Cancer Therapeutics ◽  
Mitotic Exit ◽  
Protein Phosphatase 1 ◽  
Aurora B ◽  
Aurora B Kinase ◽  
Ki 67 ◽  
Anaphase Onset

Ki-67 and RepoMan have key roles during mitotic exit. Previously, we showed that Ki-67 organizes the mitotic chromosome periphery and recruits protein phosphatase 1 (PP1) to chromatin at anaphase onset, in a similar manner as RepoMan (<xref ref-type="bibr" rid="bib2">Booth et al., 2014</xref>). Here we show how Ki-67 and RepoMan form mitotic exit phosphatases by recruiting PP1, how they distinguish between distinct PP1 isoforms and how the assembly of these two holoenzymes are dynamically regulated by Aurora B kinase during mitosis. Unexpectedly, our data also reveal that Ki-67 and RepoMan bind PP1 using an identical, yet novel mechanism, interacting with a PP1 pocket that is engaged only by these two PP1 regulators. These findings not only show how two distinct mitotic exit phosphatases are recruited to their substrates, but also provide immediate opportunities for the design of novel cancer therapeutics that selectively target the Ki-67:PP1 and RepoMan:PP1 holoenzymes.

Interplay between mitotic kinesins and the Aurora kinase–PP1 (protein phosphatase 1) axis

2013 ◽  
Vol 41 (6) ◽  
pp. 1761-1765 ◽  
Author(s):  
John C. Meadows
Keyword(s):  
Protein Phosphatase ◽  
Spindle Assembly Checkpoint ◽  
Spindle Checkpoint ◽  
Aurora Kinase ◽  
Protein Phosphatase 1 ◽  
Aurora B ◽  
Spatial Gradient ◽  
Cell Cycle Regulators ◽  
Aurora B Kinase ◽  
Surveillance Mechanism

Correct transmission of genetic information from mother to daughter cells is necessary for development and survival. Accurate segregation is achieved by bipolar attachment of sister kinetochores in each chromatid pair to spindle microtubules emanating from opposite spindle poles, a process known as chromosome bi-orientation. Achieving this requires dynamic interplay between kinetochore proteins, kinesin motor proteins and cell cycle regulators. Chromosome bi-orientation is monitored by a surveillance mechanism known as the SAC (spindle assembly checkpoint). The Aurora B kinase, which is bound to the inner centromere during early mitosis, plays a central role in both chromosome bi-orientation and the spindle checkpoint. The application of tension across centromeres establishes a spatial gradient of high phosphorylation activity at the inner centromere and low phosphorylation activity at the outer kinetochore. This gradient is further refined by the association of PP1 (protein phosphatase 1) to the outer kinetochore, which stabilizes kinetochore–microtubule interactions and silences the spindle checkpoint by dephosphorylating Aurora B kinase targets when chromosome bi-orientation is achieved. In the present review, I discuss emerging evidence that bidirectional cross-talk between mitotic kinesins and the Aurora kinase–PP1 axis is crucial for co-ordinating chromosome bi-orientation and spindle checkpoint signalling in eukaryotes.

scholarly journals Protein phosphatase 1 is essential for Greatwall inactivation at mitotic exit

EMBO Reports ◽  
2015 ◽  
Vol 16 (11) ◽  
pp. 1501-1510 ◽  
Author(s):  
Andreas Heim ◽  
Anja Konietzny ◽  
Thomas U Mayer
Keyword(s):  
Protein Phosphatase ◽  
Mitotic Exit ◽  
Protein Phosphatase 1

scholarly journals The cortical protein Lte1 promotes mitotic exit by inhibiting the spindle position checkpoint kinase Kin4

2011 ◽  
Vol 193 (6) ◽  
pp. 1033-1048 ◽  
Author(s):  
Daniela Trinca Bertazzi ◽  
Bahtiyar Kurtulmus ◽  
Gislene Pereira
Keyword(s):  
Kinase Activity ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Mitotic Exit ◽  
Cell Protein ◽  
Cell Axis ◽  
Pole Body ◽  
Catalytically Active ◽  
Surveillance Mechanism ◽  
Spindle Position

The spindle position checkpoint (SPOC) is an essential surveillance mechanism that allows mitotic exit only when the spindle is correctly oriented along the cell axis. Key SPOC components are the kinase Kin4 and the Bub2–Bfa1 GAP complex that inhibit the mitotic exit–promoting GTPase Tem1. During an unperturbed cell cycle, Kin4 associates with the mother spindle pole body (mSPB), whereas Bub2–Bfa1 is at the daughter SPB (dSPB). When the spindle is mispositioned, Bub2–Bfa1 and Kin4 bind to both SPBs, which enables Kin4 to phosphorylate Bfa1 and thereby block mitotic exit. Here, we show that the daughter cell protein Lte1 physically interacts with Kin4 and inhibits Kin4 kinase activity. Specifically, Lte1 binds to catalytically active Kin4 and promotes Kin4 hyperphosphorylation, which restricts Kin4 binding to the mSPB. This Lte1-mediated exclusion of Kin4 from the dSPB is essential for proper mitotic exit of cells with a correctly aligned spindle. Therefore, Lte1 promotes mitotic exit by inhibiting Kin4 activity at the dSPB.

scholarly journals Interaction of Protein Phosphatase 1 Delta with Nucleolin in Human Osteoblastic Cells

2002 ◽  
Vol 50 (9) ◽  
pp. 1187-1193 ◽  
Author(s):  
Hiroyuki Morimoto ◽  
Hirohiko Okamura ◽  
Tatsuji Haneji
Keyword(s):  
Protein Phosphatase ◽  
Actinomycin D ◽  
Protein Phosphatase 1 ◽  
Immunofluorescence Method ◽  
Whole Cell Lysate ◽  
Protein Phosphatase Type 1 ◽  
Mg63 Cells ◽  
Human Osteoblastic Cells ◽  
Protein Phosphatase Type

We examined the expression and cytolocalization of the protein phosphatase type 1 delta (PP1δ) isoform and nucleolin in human osteoblastic MG63 and Saos-2 cells. Cellular fractionation of MG63 cells was done and protein was prepared from each fraction. Anti-nucleolin antibody interacted with the 100- and 95-kD proteins present in the whole-cell lysate. The 100-kD protein was detected in nuclear and nucleolar fractions. The 95-kD protein was detected in cytosolic and nucleoplasmic fractions. PP1δ and nucleolin were co-localized in the nucleolus in MG63 and Saos-2 cells revealed by an immunofluorescence method. PP1δ and nucleolin were also co-immunoprecipitated with anti-nucleolin and anti-PP1δ antibodies. In the actinomycin D-treated cells, the subcellular localization of PP1δ and nucleolin was changed. Expression of PP1δ was upregulated with actinomycin D treatment. The level of 100-kD protein did not change in the actinomycin D-treated cells. However, the level of the 95-kD band increased with actinomycin D treatment. These results indicate that PP1δ was associated with nucleolin in the nucleolus of MG63 and Saos-2 cells and that nucleolin is a possible candidate substrate for PP1δ.

scholarly journals Different Levels of Bfa1/Bub2 GAP Activity Are Required to Prevent Mitotic Exit of Budding Yeast Depending on the Type of Perturbations

2008 ◽  
Vol 19 (10) ◽  
pp. 4328-4340 ◽  
Author(s):  
Junwon Kim ◽  
Selma Sun Jang ◽  
Kiwon Song
Keyword(s):  
Budding Yeast ◽  
Mitotic Exit ◽  
Nucleotide Exchange ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Surveillance Mechanism ◽  
Spindle Position ◽  
First Time ◽  
Different Levels

In budding yeast, Tem1 is a key regulator of mitotic exit. Bfa1/Bub2 stimulates Tem1 GTPase activity as a GTPase-activating protein (GAP). Lte1 possesses a guanine-nucleotide exchange factor (GEF) domain likely for Tem1. However, recent observations showed that cells may control mitotic exit without either Lte1 or Bfa1/Bub2 GAP activity, obscuring how Tem1 is regulated. Here, we assayed BFA1 mutants with varying GAP activities for Tem1, showing for the first time that Bfa1/Bub2 GAP activity inhibits Tem1 in vivo. A decrease in GAP activity allowed cells to bypass mitotic exit defects. Interestingly, different levels of GAP activity were required to prevent mitotic exit depending on the type of perturbation. Although essential, more Bfa1/Bub2 GAP activity was needed for spindle damage than for DNA damage to fully activate the checkpoint. Conversely, Bfa1/Bub2 GAP activity was insufficient to delay mitotic exit in cells with misoriented spindles. Instead, decreased interaction of Bfa1 with Kin4 was observed in BFA1 mutant cells with a defective spindle position checkpoint. These findings demonstrate that there is a GAP-independent surveillance mechanism of Bfa1/Bub2, which, together with the GTP/GDP switch of Tem1, may be required for the genomic stability of cells with misaligned spindles.

scholarly journals Protein Phosphatase 1 inactivates Mps1 to ensure efficient Spindle Assembly Checkpoint silencing

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Margarida Moura ◽  
Mariana Osswald ◽  
Nelson Leça ◽  
João Barbosa ◽  
António J Pereira ◽  
...  
Keyword(s):  
Protein Phosphatase ◽  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Mitotic Exit ◽  
Protein Phosphatase 1 ◽  
Anaphase Onset ◽  
Phosphorylation Cascade ◽  
Spindle Microtubules ◽  
Early Mitosis

Faithfull genome partitioning during cell division relies on the Spindle Assembly Checkpoint (SAC), a conserved signaling pathway that delays anaphase onset until all chromosomes are attached to spindle microtubules. Mps1 kinase is an upstream SAC regulator that promotes the assembly of an anaphase inhibitor through a sequential multi-target phosphorylation cascade. Thus, the SAC is highly responsive to Mps1, whose activity peaks in early mitosis as a result of its T-loop autophosphorylation. However, the mechanism controlling Mps1 inactivation once kinetochores attach to microtubules and the SAC is satisfied remains unknown. Here we show in vitro and in Drosophila that Protein Phosphatase 1 (PP1) inactivates Mps1 by dephosphorylating its T-loop. PP1-mediated dephosphorylation of Mps1 occurs at kinetochores and in the cytosol, and inactivation of both pools of Mps1 during metaphase is essential to ensure prompt and efficient SAC silencing. Overall, our findings uncover a mechanism of SAC inactivation required for timely mitotic exit.

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