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.

scholarly journals Differential requirement for Bub1 and Bub3 in regulation of meiotic versus mitotic chromosome segregation

2020 ◽  
Vol 219 (4) ◽  
Author(s):  
Gisela Cairo ◽  
Anne M. MacKenzie ◽  
Soni Lacefield
Keyword(s):  
Chromosome Segregation ◽  
Protein Phosphatase ◽  
Mitotic Chromosome ◽  
Budding Yeast ◽  
Meiotic Chromosome ◽  
Protein Phosphatase 1 ◽  
Aurora B ◽  
Chromosome Missegregation ◽  
Anaphase Onset ◽  
Spindle Microtubules

Accurate chromosome segregation depends on the proper attachment of kinetochores to spindle microtubules before anaphase onset. The Ipl1/Aurora B kinase corrects improper attachments by phosphorylating kinetochore components and so releasing aberrant kinetochore–microtubule interactions. The localization of Ipl1 to kinetochores in budding yeast depends upon multiple pathways, including the Bub1–Bub3 pathway. We show here that in meiosis, Bub3 is crucial for correction of attachment errors. Depletion of Bub3 results in reduced levels of kinetochore-localized Ipl1 and concomitant massive chromosome missegregation caused by incorrect chromosome–spindle attachments. Depletion of Bub3 also results in shorter metaphase I and metaphase II due to premature localization of protein phosphatase 1 (PP1) to kinetochores, which antagonizes Ipl1-mediated phosphorylation. We propose a new role for the Bub1–Bub3 pathway in maintaining the balance between kinetochore localization of Ipl1 and PP1, a balance that is essential for accurate meiotic chromosome segregation and timely anaphase onset.

scholarly journals Bub3 and Bub1 maintain the balance of kinetochore-localized Aurora B Kinase and Protein Phosphatase I to Regulate Chromosome Segregation and Anaphase Onset in Meiosis

2019 ◽  
Author(s):  
Gisela Cairo ◽  
Anne M. MacKenzie ◽  
Soni Lacefield
Keyword(s):  
Chromosome Segregation ◽  
Protein Phosphatase ◽  
Meiotic Chromosome ◽  
Protein Phosphatase 1 ◽  
Aurora B ◽  
Aurora B Kinase ◽  
Checkpoint Proteins ◽  
Anaphase Onset ◽  
Normal Duration ◽  
Spindle Microtubules

AbstractAccurate chromosome segregation depends on proper attachment of kinetochores to spindle microtubules prior to anaphase onset. The Ipl1/Aurora B kinase corrects improper attachments by phosphorylating kinetochore components and so releasing aberrant kinetochore-microtubule interactions. The localization of Ipl1 to kinetochores in budding yeast depends upon multiple pathways, including the Bub1/Bub3 pathway. We show here that in meiosis, Bub3 is crucial for correction of attachment errors. Depletion of Bub3 results in reduced levels of kinetochore-localized Ipl1, and concomitant massive chromosome mis-segregation caused by incorrect chromosome-spindle attachments. Depletion of Bub3 also results in shorter metaphase I and metaphase II due to premature localization of protein phosphatase 1 (PP1) to kinetochores, which antagonizes Ipl1-mediated phosphorylation. We propose a new role for the Bub1-Bub3 pathway in maintaining the balance between kinetochore-localization of Ipl1 and PP1, a balance that is essential for accurate meiotic chromosome segregation and timely anaphase onset.SummaryCairo et al show that in S. cerevisiae meiosis, spindle checkpoint proteins Bub1 and Bub3 have an essential role in preventing chromosome mis-segregation and setting the normal duration of anaphase I and anaphase II onset by regulating the kinetochore-localization of Ipl1 and PP1.

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 Aurora B kinase and protein phosphatase 1 have opposing roles in modulating kinetochore assembly

2008 ◽  
Vol 181 (2) ◽  
pp. 241-254 ◽  
Author(s):  
Michael J. Emanuele ◽  
Weijie Lan ◽  
Miri Jwa ◽  
Stephanie A. Miller ◽  
Clarence S.M. Chan ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Protein Phosphatase ◽  
Protein Phosphatase 1 ◽  
Aurora B ◽  
Aurora B Kinase ◽  
Culture Cells ◽  
Kinetochore Assembly ◽  
M Phase ◽  
Egg Extracts ◽  
Cycle Dependent

The outer kinetochore binds microtubules to control chromosome movement. Outer kinetochore assembly is restricted to mitosis, whereas the inner kinetochore remains tethered to centromeres throughout the cell cycle. The cues that regulate this transient assembly are unknown. We find that inhibition of Aurora B kinase significantly reduces outer kinetochore assembly in Xenopus laevis and human tissue culture cells, frog egg extracts, and budding yeast. In X. leavis M phase extracts, preassembled kinetochores disassemble after inhibiting Aurora B activity with either drugs or antibodies. Kinetochore disassembly, induced by Aurora B inhibition, is rescued by restraining protein phosphatase 1 (PP1) activity. PP1 is necessary for kinetochores to disassemble at the exit from M phase, and purified enzyme is sufficient to cause disassembly on isolated mitotic nuclei. These data demonstrate that Aurora B activity is required for kinetochore maintenance and that PP1 is necessary and sufficient to disassemble kinetochores. We suggest that Aurora B and PP1 coordinate cell cycle–dependent changes in kinetochore assembly though phosphorylation of kinetochore substrates.

scholarly journals Chromosome clustering in mitosis by the nuclear protein Ki-67

2021 ◽  
Author(s):  
Konstantinos Stamatiou ◽  
Paola Vagnarelli
Keyword(s):  
Protein Phosphatase ◽  
Mitotic Chromosome ◽  
Nuclear Protein ◽  
Protein A ◽  
Mitotic Exit ◽  
Proliferating Cells ◽  
Ki 67 ◽  
Mitotic Entry ◽  
Long Time

Ki-67 is highly expressed in proliferating cells, a characteristic that made the protein a very important proliferation marker widely used in the clinic. However, the molecular functions and properties of Ki-67 remained quite obscure for a long time. Only recently important discoveries have shed some light on its function and shown that Ki-67 has a major role in the formation of mitotic chromosome periphery compartment, it is associated with protein phosphatase one (PP1) and regulates chromatin function in interphase and mitosis. In this review, we discuss the role of Ki-67 during cell division. Specifically, we focus on the importance of Ki-67 in chromosome individualisation at mitotic entry (prometaphase) and its contribution to chromosome clustering and nuclear remodelling during mitotic exit.

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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