scholarly journals Cyclin A2 localises in the cytoplasm at the S/G2 transition to activate PLK1

2021 ◽  
Vol 4 (3) ◽  
pp. e202000980
Author(s):  
Helena Silva Cascales ◽  
Kamila Burdova ◽  
Anna Middleton ◽  
Vladislav Kuzin ◽  
Erik Müllers ◽  
...  
Keyword(s):  
Dna Replication ◽  
Feedback Loops ◽  
Kinase Activation ◽  
Mitotic Entry ◽  
Mitotic Kinases ◽  
Mitotic Kinase ◽  
Transition Functions ◽  
G2 Phase ◽  
Cyclin A2 ◽  
Plk1 Expression

Cyclin A2 is a key regulator of the cell cycle, implicated both in DNA replication and mitotic entry. Cyclin A2 participates in feedback loops that activate mitotic kinases in G2 phase, but why active Cyclin A2-CDK2 during the S phase does not trigger mitotic kinase activation remains unclear. Here, we describe a change in localisation of Cyclin A2 from being only nuclear to both nuclear and cytoplasmic at the S/G2 border. We find that Cyclin A2-CDK2 can activate the mitotic kinase PLK1 through phosphorylation of Bora, and that only cytoplasmic Cyclin A2 interacts with Bora and PLK1. Expression of predominately cytoplasmic Cyclin A2 or phospho-mimicking PLK1 T210D can partially rescue a G2 arrest caused by Cyclin A2 depletion. Cytoplasmic presence of Cyclin A2 is restricted by p21, in particular after DNA damage. Cyclin A2 chromatin association during DNA replication and additional mechanisms contribute to Cyclin A2 localisation change in the G2 phase. We find no evidence that such mechanisms involve G2 feedback loops and suggest that cytoplasmic appearance of Cyclin A2 at the S/G2 transition functions as a trigger for mitotic kinase activation.

scholarly journals Cyclin A2 localises in the cytoplasm at the S/G2 transition to activate PLK1

2017 ◽  
Author(s):  
Helena Silva Cascales ◽  
Kamila Burdova ◽  
Anna Middleton ◽  
Vladislav Kuzin ◽  
Erik Müllers ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Replication ◽  
Feedback Loops ◽  
List Type ◽  
Kinase Activation ◽  
Mitotic Kinases ◽  
Mitotic Kinase ◽  
Transition Functions ◽  
G2 Phase ◽  
Cyclin A2

AbstractCyclin A2 is a key regulator of the cell cycle, implicated both in DNA replication and mitotic entry. Cyclin A2 participates in feedback loops that activate mitotic kinases in G2-phase, but why active Cyclin A2-CDK2 during S phase does not trigger mitotic kinase activation remains unclear. Here we describe a change in localisation of Cyclin A2 from being only nuclear to both nuclear and cytoplasmic at the S/G2 border. We find that Cyclin A2-CDK2 can activate the mitotic kinase PLK1 through phosphorylation of Bora, and that only cytoplasmic Cyclin A2 interacts with Bora and PLK1. Expression of predominately cytoplasmic Cyclin A2 or phospho-mimicking PLK1 T210D can partially rescue a G2 arrest caused by Cyclin A2 depletion. Cytoplasmic presence of Cyclin A2 is restricted by p21, in particular after DNA damage. Cyclin A2 chromatin association during DNA replication and additional mechanisms contribute to Cyclin A2 localisation change in G2 phase. We find no evidence that such mechanisms involve G2 feedback loops and suggest that cytoplasmic appearance of Cyclin A2 at the S/G2 transition functions as a trigger for mitotic kinase activation.SynopsisMain mitotic kinases as PLK1 are activated at the S/G2 transition. A change in Cyclin A2 localisation at the S/G2 transition enables activation of PLK1.Main points-Cyclin A2 appears in the cytoplasm at the S/G2 transition-Association with replicating chromatin and p21 restricts Cyclin A2 to the nucleus-DNA damage ensures nuclear Cyclin A2 through p21-Cytoplasmic Cyclin A2 initiates PLK1 activationGraphical abstract

The structural mechanisms that underpin mitotic kinase activation

2013 ◽  
Vol 41 (4) ◽  
pp. 1037-1041 ◽  
Author(s):  
Charlotte A. Dodson ◽  
Tamanna Haq ◽  
Sharon Yeoh ◽  
Andrew M. Fry ◽  
Richard Bayliss
Keyword(s):  
Protein Phosphorylation ◽  
Protein Kinases ◽  
Rational Design ◽  
Significant Proportion ◽  
Small Subset ◽  
Kinase Activation ◽  
Mitotic Kinases ◽  
Mitotic Kinase ◽  
Almost All ◽  
Structural Mechanisms

In eukaryotic cells, the peak of protein phosphorylation occurs during mitosis, switching the activities of a significant proportion of proteins and orchestrating a wholesale reorganization of cell shape and internal architecture. Most mitotic protein phosphorylation events are catalysed by a small subset of serine/threonine protein kinases. These include members of the Cdk (cyclin-dependent kinase), Plk (Polo-like kinase), Aurora, Nek (NimA-related kinase) and Bub families, as well as Haspin, Greatwall and Mps1/TTK. There has been steady progress in resolving the structural mechanisms that regulate the catalytic activities of these mitotic kinases. From structural and biochemical perspectives, kinase activation appears not as a binary process (from inactive to active), but as a series of states that exhibit varying degrees of activity. In its lowest activity state, a mitotic kinase may exhibit diverse autoinhibited or inactive conformations. Kinase activation proceeds via phosphorylation and/or association with a binding partner. These remodel the structure into an active conformation that is common to almost all protein kinases. However, all mitotic kinases of known structure have divergent features, many of which are key to understanding their specific regulatory mechanisms. Finally, mitotic kinases are an important class of drug target, and their structural characterization has facilitated the rational design of chemical inhibitors.

scholarly journals On the molecular mechanisms of mitotic kinase activation

Open Biology ◽  
2012 ◽  
Vol 2 (11) ◽  
pp. 120136 ◽  
Author(s):  
Richard Bayliss ◽  
Andrew Fry ◽  
Tamanna Haq ◽  
Sharon Yeoh
Keyword(s):  
Protein Interactions ◽  
Molecular Mechanisms ◽  
Critical Role ◽  
Significant Proportion ◽  
Structural Basis ◽  
Kinase Activation ◽  
Mitotic Kinases ◽  
Mitotic Kinase ◽  
Disease Biology ◽  
Activation Mechanisms

During mitosis, human cells exhibit a peak of protein phosphorylation that alters the behaviour of a significant proportion of proteins, driving a dramatic transformation in the cell's shape, intracellular structures and biochemistry. These mitotic phosphorylation events are catalysed by several families of protein kinases, including Auroras, Cdks, Plks, Neks, Bubs, Haspin and Mps1/TTK. The catalytic activities of these kinases are activated by phosphorylation and through protein–protein interactions. In this review, we summarize the current state of knowledge of the structural basis of mitotic kinase activation mechanisms. This review aims to provide a clear and comprehensive primer on these mechanisms to a broad community of researchers, bringing together the common themes, and highlighting specific differences. Along the way, we have uncovered some features of these proteins that have previously gone unreported, and identified unexplored questions for future work. The dysregulation of mitotic kinases is associated with proliferative disorders such as cancer, and structural biology will continue to play a critical role in the development of chemical probes used to interrogate disease biology and applied to the treatment of patients.

How protein kinases co-ordinate mitosis in animal cells

2011 ◽  
Vol 435 (1) ◽  
pp. 17-31 ◽  
Author(s):  
Hoi Tang Ma ◽  
Randy Y. C. Poon
Keyword(s):  
Protein Kinases ◽  
Feedback Loops ◽  
Cell Physiology ◽  
Animal Cells ◽  
Aurora Kinases ◽  
Cyclin Dependent Kinases ◽  
Mitotic Kinases ◽  
Mitotic Kinase ◽  
Recurrent Theme

Mitosis is associated with profound changes in cell physiology and a spectacular surge in protein phosphorylation. To accomplish these, a remarkably large portion of the kinome is involved in the process. In the present review, we will focus on classic mitotic kinases, such as cyclin-dependent kinases, Polo-like kinases and Aurora kinases, as well as more recently characterized players such as NIMA (never in mitosis in Aspergillus nidulans)-related kinases, Greatwall and Haspin. Together, these kinases co-ordinate the proper timing and fidelity of processes including centrosomal functions, spindle assembly and microtubule–kinetochore attachment, as well as sister chromatid separation and cytokinesis. A recurrent theme of the mitotic kinase network is the prevalence of elaborated feedback loops that ensure bistable conditions. Sequential phosphorylation and priming phosphorylation on substrates are also frequently employed. Another important concept is the role of scaffolds, such as centrosomes for protein kinases during mitosis. Elucidating the entire repertoire of mitotic kinases, their functions, regulation and interactions is critical for our understanding of normal cell growth and in diseases such as cancers.

scholarly journals Protein phosphatase 6 regulates mitotic spindle formation by controlling the T-loop phosphorylation state of Aurora A bound to its activator TPX2

2010 ◽  
Vol 191 (7) ◽  
pp. 1315-1332 ◽  
Author(s):  
Kang Zeng ◽  
Ricardo Nunes Bastos ◽  
Francis A. Barr ◽  
Ulrike Gruneberg
Keyword(s):  
Protein Phosphatase ◽  
Aurora A ◽  
Spindle Formation ◽  
Regulatory Subunits ◽  
Kinase Activation ◽  
Activator Proteins ◽  
Mitotic Kinase ◽  
General Importance ◽  
The Stability

Many protein kinases are activated by a conserved regulatory step involving T-loop phosphorylation. Although there is considerable focus on kinase activator proteins, the importance of specific T-loop phosphatases reversing kinase activation has been underappreciated. We find that the protein phosphatase 6 (PP6) holoenzyme is the major T-loop phosphatase for Aurora A, an essential mitotic kinase. Loss of PP6 function by depletion of catalytic or regulatory subunits interferes with spindle formation and chromosome alignment because of increased Aurora A activity. Aurora A T-loop phosphorylation and the stability of the Aurora A–TPX2 complex are increased in cells depleted of PP6 but not other phosphatases. Furthermore, purified PP6 acts as a T-loop phosphatase for Aurora A–TPX2 complexes in vitro, whereas catalytically inactive mutants cannot dephosphorylate Aurora A or rescue the PPP6C depletion phenotype. These results demonstrate a hitherto unappreciated role for PP6 as the T-loop phosphatase regulating Aurora A activity during spindle formation and suggest the general importance of this form of regulation.

scholarly journals Cell cycle arrest of cdc mutants and specificity of the RAD9 checkpoint.

Genetics ◽  
1993 ◽  
Vol 134 (1) ◽  
pp. 63-80 ◽  
Author(s):  
T A Weinert ◽  
L H Hartwell
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Dna Replication ◽  
Cell Cycle Control ◽  
Dna Lesions ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
A Cell ◽  
G2 Phase ◽  
Rad Mutants

Abstract In eucaryotes a cell cycle control called a checkpoint ensures that mitosis occurs only after chromosomes are completely replicated and any damage is repaired. The function of this checkpoint in budding yeast requires the RAD9 gene. Here we examine the role of the RAD9 gene in the arrest of the 12 cell division cycle (cdc) mutants, temperature-sensitive lethal mutants that arrest in specific phases of the cell cycle at a restrictive temperature. We found that in four cdc mutants the cdc rad9 cells failed to arrest after a shift to the restrictive temperature, rather they continued cell division and died rapidly, whereas the cdc RAD cells arrested and remained viable. The cell cycle and genetic phenotypes of the 12 cdc RAD mutants indicate the function of the RAD9 checkpoint is phase-specific and signal-specific. First, the four cdc RAD mutants that required RAD9 each arrested in the late S/G2 phase after a shift to the restrictive temperature when DNA replication was complete or nearly complete, and second, each leaves DNA lesions when the CDC gene product is limiting for cell division. Three of the four CDC genes are known to encode DNA replication enzymes. We found that the RAD17 gene is also essential for the function of the RAD9 checkpoint because it is required for phase-specific arrest of the same four cdc mutants. We also show that both X- or UV-irradiated cells require the RAD9 and RAD17 genes for delay in the G2 phase. Together, these results indicate that the RAD9 checkpoint is apparently activated only by DNA lesions and arrests cell division only in the late S/G2 phase.

Timing of nucleolar DNA replication in Amoeba proteus

1976 ◽  
Vol 22 (3) ◽  
pp. 521-530
Author(s):  
I. Minassian ◽  
L.G. Bell
Keyword(s):  
Electron Microscope ◽  
Dna Replication ◽  
Dna Synthesis ◽  
Central Region ◽  
Thymidine Incorporation ◽  
Tritiated Thymidine ◽  
Amoeba Proteus ◽  
Electron Microscope Autoradiography ◽  
Microscope Autoradiography ◽  
G2 Phase

Light- and electron-microscope autoradiography have been used to follow the incorporation of [3H]thymidine at different stages during the interphase of synchronously growing populations of Amoeba proteus. Two main patterns were found for tritiated thymidine incorporation, i.e. DNA synthesis. The major incorporation was in the central region of the nucleus, but a lesser degree of incorporation occurred in the nucleolar region. The bulk of this nucleolar DNA was found to be late replicating, i.e. it replicated during the G2 phase.

Cdc18p can block mitosis by two independent mechanisms

1998 ◽  
Vol 111 (20) ◽  
pp. 3101-3108 ◽  
Author(s):  
E. Greenwood ◽  
H. Nishitani ◽  
P. Nurse
Keyword(s):  
Dna Replication ◽  
S Phase ◽  
Checkpoint Control ◽  
Replication Checkpoint ◽  
Mitotic Kinase ◽  
C Terminus ◽  
N Terminus ◽  
Dna Replication Checkpoint ◽  
Checkpoint Genes

The DNA replication checkpoint is required to maintain the integrity of the genome, inhibiting mitosis until S phase has been successfully completed. The checkpoint preventing premature mitosis in Schizosaccharomyces pombe relies on phosphorylation of the tyrosine-15 residue on cdc2p to prevent its activation and hence mitosis. The cdc18 gene is essential for both generating the DNA replication checkpoint and the initiation of S phase, thus providing a key role for the overall control and coordination of the cell cycle. We show that the C terminus of the protein is capable of both initiating DNA replication and the checkpoint function of cdc18p. The C terminus of cdc18p acts upstream of the DNA replication checkpoint genes rad1, rad3, rad9, rad17, hus1 and cut5 and requires the wee1p/mik1p tyrosine kinases to block mitosis. The N terminus of cdc18p can also block mitosis but does so in the absence of the DNA replication checkpoint genes and the wee1p/mik1p kinases therefore acting downstream of these genes. Because the N terminus of cdc18p associates with cdc2p in vivo, we suggest that by binding the cdc2p/cdc13p mitotic kinase directly, it exerts an effect independently of the normal checkpoint control, probably in an unphysiological manner.

WEE1 kinase limits CDK activities to safeguard DNA replication and mitotic entry

2020 ◽  
Vol 819-820 ◽  
pp. 111694 ◽  
Author(s):  
Camilla R. Elbæk ◽  
Valdemaras Petrosius ◽  
Claus S. Sørensen
Keyword(s):  
Dna Replication ◽  
Mitotic Entry ◽  
Wee1 Kinase

scholarly journals Oncogenic MYC amplifies mitotic perturbations

Open Biology ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 190136 ◽  
Author(s):  
Samantha Littler ◽  
Olivia Sloss ◽  
Bethany Geary ◽  
Andrew Pierce ◽  
Anthony D. Whetton ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Mitotic Chromosome ◽  
Chromosome Instability ◽  
Ros Production ◽  
Mitotic Entry ◽  
Multiple Networks ◽  
Mitotic Kinase ◽  
Dependent Processes ◽  
Ability To Drive ◽  
Oncogenic Transcription Factor

The oncogenic transcription factor MYC modulates vast arrays of genes, thereby influencing numerous biological pathways including biogenesis, metabolism, proliferation, apoptosis and pluripotency. When deregulated, MYC drives genomic instability via several mechanisms including aberrant proliferation, replication stress and ROS production. Deregulated MYC also promotes chromosome instability, but less is known about how MYC influences mitosis. Here, we show that deregulating MYC modulates multiple aspects of mitotic chromosome segregation. Cells overexpressing MYC have altered spindle morphology, take longer to align their chromosomes at metaphase and enter anaphase sooner. When challenged with a variety of anti-mitotic drugs, cells overexpressing MYC display more anomalies, the net effect of which is increased micronuclei, a hallmark of chromosome instability. Proteomic analysis showed that MYC modulates multiple networks predicted to influence mitosis, with the mitotic kinase PLK1 identified as a central hub. In turn, we show that MYC modulates several PLK1-dependent processes, namely mitotic entry, spindle assembly and SAC satisfaction. These observations thus underpin the pervasive nature of oncogenic MYC and provide a mechanistic rationale for MYC's ability to drive chromosome instability.

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