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

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.

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 p53-dependent polyploidisation after DNA damage in G2 phase

2020 ◽  
Author(s):  
Anna Middleton ◽  
Rakesh Suman ◽  
Peter O’Toole ◽  
Karen Akopyan ◽  
Arne Lindqvist
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Cell Tracking ◽  
Phase Cell ◽  
List Type ◽  
Dependent Manner ◽  
Cell Cycle Exit ◽  
Polyploid Cells ◽  
G2 Phase ◽  
Damaged Dna

AbstractCell cycle progression in the presence of damaged DNA can lead to accumulation of mutations and pose a risk for tumour development. In response to DNA damage in G2 phase, human cells can be forced to exit the cell cycle in a p53-p21- and APC/CCdh1-dependent manner. Cells that exit the cell cycle in G2 phase become senescent, but it is unclear what determines this commitment and whether other cell fates occur. We find that a subset of immortalised RPE-1 cells and primary human fibroblasts spontaneously initiate DNA re-replication several days after forced cell cycle exit in G2 phase. By combining single cell tracking for more than a week with quantitative immunofluorescence, we find that the resulting polyploid cells contain increased levels of damaged DNA and frequently exit the cell cycle again in the next G2 phase. Subsequently, these cells either enter senescence or commit to another round of DNA re-replication, further increasing the ploidy. At least a subset of the polyploid cells show abnormal centrosome numbers or localisation. In conclusion, cells that are forced to exit the cell cycle in G2 phase face multiple choices that lead to various phenotypes, including propagation of cells with different ploidies. Our findings suggest a mechanism by which p53-positive cells can evade senescence that risks genome integrity.Main points-Cell cycle exit from G2 phase does not necessarily lead to senescence-Resumption of proliferation after G2 phase cell cycle exit starts with DNA replication-Successive cell cycle exits lead to propagation of cells with different ploidies-A p53-dependent mechanism allows eventual proliferation after DNA damage

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 Regulation of Cell Division in Bacteria by Monitoring Genome Integrity and DNA Replication Status

2019 ◽  
Vol 202 (2) ◽  
Author(s):  
Peter E. Burby ◽  
Lyle A. Simmons
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Cell Division ◽  
Dna Replication ◽  
Cell Cycle Progression ◽  
Genome Instability ◽  
Sos Response ◽  
Bacterial Cells ◽  
Cycle Progression ◽  
Content Type

ABSTRACT All organisms regulate cell cycle progression by coordinating cell division with DNA replication status. In eukaryotes, DNA damage or problems with replication fork progression induce the DNA damage response (DDR), causing cyclin-dependent kinases to remain active, preventing further cell cycle progression until replication and repair are complete. In bacteria, cell division is coordinated with chromosome segregation, preventing cell division ring formation over the nucleoid in a process termed nucleoid occlusion. In addition to nucleoid occlusion, bacteria induce the SOS response after replication forks encounter DNA damage or impediments that slow or block their progression. During SOS induction, Escherichia coli expresses a cytoplasmic protein, SulA, that inhibits cell division by directly binding FtsZ. After the SOS response is turned off, SulA is degraded by Lon protease, allowing for cell division to resume. Recently, it has become clear that SulA is restricted to bacteria closely related to E. coli and that most bacteria enforce the DNA damage checkpoint by expressing a small integral membrane protein. Resumption of cell division is then mediated by membrane-bound proteases that cleave the cell division inhibitor. Further, many bacterial cells have mechanisms to inhibit cell division that are regulated independently from the canonical LexA-mediated SOS response. In this review, we discuss several pathways used by bacteria to prevent cell division from occurring when genome instability is detected or before the chromosome has been fully replicated and segregated.

scholarly journals Regulation of DNA Replication Licensing and Re-Replication by Cdt1

2021 ◽  
Vol 22 (10) ◽  
pp. 5195
Author(s):  
Hui Zhang
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Dna Replication ◽  
Genome Stability ◽  
E3 Ligase ◽  
S Phase ◽  
Replication Initiation ◽  
Nuclear Antigen ◽  
Repair Synthesis ◽  
Ubiquitin E3 Ligase

In eukaryotic cells, DNA replication licensing is precisely regulated to ensure that the initiation of genomic DNA replication in S phase occurs once and only once for each mitotic cell division. A key regulatory mechanism by which DNA re-replication is suppressed is the S phase-dependent proteolysis of Cdt1, an essential replication protein for licensing DNA replication origins by loading the Mcm2-7 replication helicase for DNA duplication in S phase. Cdt1 degradation is mediated by CRL4Cdt2 ubiquitin E3 ligase, which further requires Cdt1 binding to proliferating cell nuclear antigen (PCNA) through a PIP box domain in Cdt1 during DNA synthesis. Recent studies found that Cdt2, the specific subunit of CRL4Cdt2 ubiquitin E3 ligase that targets Cdt1 for degradation, also contains an evolutionarily conserved PIP box-like domain that mediates the interaction with PCNA. These findings suggest that the initiation and elongation of DNA replication or DNA damage-induced repair synthesis provide a novel mechanism by which Cdt1 and CRL4Cdt2 are both recruited onto the trimeric PCNA clamp encircling the replicating DNA strands to promote the interaction between Cdt1 and CRL4Cdt2. The proximity of PCNA-bound Cdt1 to CRL4Cdt2 facilitates the destruction of Cdt1 in response to DNA damage or after DNA replication initiation to prevent DNA re-replication in the cell cycle. CRL4Cdt2 ubiquitin E3 ligase may also regulate the degradation of other PIP box-containing proteins, such as CDK inhibitor p21 and histone methylase Set8, to regulate DNA replication licensing, cell cycle progression, DNA repair, and genome stability by directly interacting with PCNA during DNA replication and repair synthesis.

Overlapping Roles of the Spindle Assembly and DNA Damage Checkpoints in the Cell-Cycle Response to Altered Chromosomes in Saccharomyces cerevisiae

Genetics ◽  
2002 ◽  
Vol 161 (2) ◽  
pp. 521-534
Author(s):  
Peter M Garber ◽  
Jasper Rine
Keyword(s):  
Dna Damage ◽  
Dna Replication ◽  
Spindle Checkpoint ◽  
Dna Lesions ◽  
Replication Proteins ◽  
Replication Checkpoint ◽  
Dna Damage Checkpoints ◽  
Dna Replication Checkpoint ◽  
Mcm Proteins ◽  
Stalled Replication Forks

Abstract The MAD2-dependent spindle checkpoint blocks anaphase until all chromosomes have achieved successful bipolar attachment to the mitotic spindle. The DNA damage and DNA replication checkpoints block anaphase in response to DNA lesions that may include single-stranded DNA and stalled replication forks. Many of the same conditions that activate the DNA damage and DNA replication checkpoints also activated the spindle checkpoint. The mad2Δ mutation partially relieved the arrest responses of cells to mutations affecting the replication proteins Mcm3p and Pol1p. Thus a previously unrecognized aspect of spindle checkpoint function may be to protect cells from defects in DNA replication. Furthermore, in cells lacking either the DNA damage or the DNA replication checkpoints, the spindle checkpoint contributed to the arrest responses of cells to the DNA-damaging agent methyl methanesulfonate, the replication inhibitor hydroxyurea, and mutations affecting Mcm2p and Orc2p. Thus the spindle checkpoint was sensitive to a wider range of chromosomal perturbations than previously recognized. Finally, the DNA replication checkpoint did not contribute to the arrests of cells in response to mutations affecting ORC, Mcm proteins, or DNA polymerase δ. Thus the specificity of this checkpoint may be more limited than previously recognized.

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