1
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Pluta AJ, Studniarek C, Murphy S, Norbury CJ. Cyclin-dependent kinases: Masters of the eukaryotic universe. WILEY INTERDISCIPLINARY REVIEWS. RNA 2023; 15:e1816. [PMID: 37718413 PMCID: PMC10909489 DOI: 10.1002/wrna.1816] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 07/21/2023] [Accepted: 08/03/2023] [Indexed: 09/19/2023]
Abstract
A family of structurally related cyclin-dependent protein kinases (CDKs) drives many aspects of eukaryotic cell function. Much of the literature in this area has considered individual members of this family to act primarily either as regulators of the cell cycle, the context in which CDKs were first discovered, or as regulators of transcription. Until recently, CDK7 was the only clear example of a CDK that functions in both processes. However, new data points to several "cell-cycle" CDKs having important roles in transcription and some "transcriptional" CDKs having cell cycle-related targets. For example, novel functions in transcription have been demonstrated for the archetypal cell cycle regulator CDK1. The increasing evidence of the overlap between these two CDK types suggests that they might play a critical role in coordinating the two processes. Here we review the canonical functions of cell-cycle and transcriptional CDKs, and provide an update on how these kinases collaborate to perform important cellular functions. We also provide a brief overview of how dysregulation of CDKs contributes to carcinogenesis, and possible treatment avenues. This article is categorized under: RNA Interactions with Proteins and Other Molecules > RNA-Protein Complexes RNA Processing > 3' End Processing RNA Processing > Splicing Regulation/Alternative Splicing.
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Affiliation(s)
| | | | - Shona Murphy
- Sir William Dunn School of PathologyUniversity of OxfordOxfordUK
| | - Chris J. Norbury
- Sir William Dunn School of PathologyUniversity of OxfordOxfordUK
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2
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Novák B, Tyson JJ. Computational modeling of chromosome re-replication in mutant strains of fission yeast. Mol Biol Cell 2021; 32:830-841. [PMID: 33534609 PMCID: PMC8108527 DOI: 10.1091/mbc.e20-09-0610] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Typically cells replicate their genome only once per division cycle, but under some circumstances, both natural and unnatural, cells synthesize an overabundance of DNA, either in a disorganized manner (“overreplication”) or by a systematic doubling of chromosome number (“endoreplication”). These variations on the theme of DNA replication and division have been studied in strains of fission yeast, Schizosaccharomyces pombe, carrying mutations that interfere with the function of mitotic cyclin-dependent kinase (Cdk1:Cdc13) without impeding the roles of DNA-replication loading factor (Cdc18) and S-phase cyclin-dependent kinase (Cdk1:Cig2). Some of these mutations support endoreplication, and some overreplication. In this paper, we propose a dynamical model of the interactions among the proteins governing DNA replication and cell division in fission yeast. By computational simulations of the mathematical model, we account for the observed phenotypes of these re-replicating mutants, and by theoretical analysis of the dynamical system, we provide insight into the molecular distinctions between overreplicating and endoreplicating cells. In the case of induced overproduction of regulatory proteins, our model predicts that cells first switch from normal mitotic cell cycles to growth-controlled endoreplication, and ultimately to disorganized overreplication, parallel to the slow increase of protein to very high levels.
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Affiliation(s)
- Béla Novák
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - John J Tyson
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061, USA
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3
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CDK Regulation of Meiosis: Lessons from S. cerevisiae and S. pombe. Genes (Basel) 2020; 11:genes11070723. [PMID: 32610611 PMCID: PMC7397238 DOI: 10.3390/genes11070723] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2020] [Revised: 06/26/2020] [Accepted: 06/26/2020] [Indexed: 12/13/2022] Open
Abstract
Meiotic progression requires precise orchestration, such that one round of DNA replication is followed by two meiotic divisions. The order and timing of meiotic events is controlled through the modulation of the phosphorylation state of proteins. Key components of this phospho-regulatory system include cyclin-dependent kinase (CDK) and its cyclin regulatory subunits. Over the past two decades, studies in budding and fission yeast have greatly informed our understanding of the role of CDK in meiotic regulation. In this review, we provide an overview of how CDK controls meiotic events in both budding and fission yeast. We discuss mechanisms of CDK regulation through post-translational modifications and changes in the levels of cyclins. Finally, we highlight the similarities and differences in CDK regulation between the two yeast species. Since CDK and many meiotic regulators are highly conserved, the findings in budding and fission yeasts have revealed conserved mechanisms of meiotic regulation among eukaryotes.
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4
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Down-regulation of Cdk1 activity in G1 coordinates the G1/S gene expression programme with genome replication. Curr Genet 2019; 65:685-690. [DOI: 10.1007/s00294-018-00926-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 12/20/2018] [Accepted: 12/22/2018] [Indexed: 02/07/2023]
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5
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CDK contribution to DSB formation and recombination in fission yeast meiosis. PLoS Genet 2019; 15:e1007876. [PMID: 30640914 PMCID: PMC6331086 DOI: 10.1371/journal.pgen.1007876] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Accepted: 12/04/2018] [Indexed: 12/19/2022] Open
Abstract
CDKs (cyclin-dependent kinases) associate with different cyclins to form different CDK-complexes that are fundamental for an ordered cell cycle progression, and the coordination of this progression with different aspects of the cellular physiology. During meiosis programmed DNA double-strand breaks (DSBs) initiate recombination that in addition to generating genetic variability are essential for the reductional chromosome segregation during the first meiotic division, and therefore for genome stability and viability of the gametes. However, how meiotic progression and DSB formation are coordinated, and the role CDKs have in the process, is not well understood. We have used single and double cyclin deletion mutants, and chemical inhibition of global CDK activity using the cdc2-asM17 allele, to address the requirement of CDK activity for DSB formation and recombination in fission yeast. We report that several cyclins (Cig1, Cig2, and the meiosis-specific Crs1) control DSB formation and recombination, with a major contribution of Crs1. Moreover, complementation analysis indicates specificity at least for this cyclin, suggesting that different CDK complexes might act in different pathways to promote recombination. Down-regulation of CDK activity impinges on the formation of linear elements (LinEs, protein complexes required for break formation at most DSB hotspot sites). This defect correlates with a reduction in the capability of one structural component (Rec25) to bind chromatin, suggesting a molecular mechanism by which CDK controls break formation. However, reduction in DSB formation in cyclin deletion mutants does not always correspondingly correlate with a proportional reduction in meiotic recombination (crossovers), suggesting that specific CDK complexes might also control downstream events balancing repair pathways. Therefore, our work points to CDK regulation of DSB formation as a key conserved feature in the initiation of meiotic recombination, in addition to provide a view of possible roles CDK might have in other steps of the recombination process. Meiotic division is a cell division process where a single round of DNA replication is followed by two sequential chromosome segregations, the first reductional (homologous chromosomes separate) and the second equational (sister chromatids segregate). As a consequence diploid organisms halve ploidy, producing haploid gametes that after fertilization generate a new diploid organism with a complete chromosome complement. At early stages of meiosis physical exchange between homologous chromosomes ensures the accurate following reductional segregation. Physical exchange is provided by recombination that initiates with highly-controlled self-inflicted DNA damage (DSBs, double strand breaks). We have found that the conserved CDK (cyclin-dependent kinase) activity controls DSB formation in fission yeast. Available data were uncertain about the conservation of CDK in the process, and thus our work points to a broad evolutionary conservation of this regulation. Regulation is exerted at least by controlling chromatin-binding of one structural component of linear elements, a protein complex related to the synaptonemal complex and required for high levels of DSBs. Correspondingly, depletion of CDK activity impairs formation of these structures. In addition, CDK might control homeostatic mechanisms, critical to maintain efficient levels of recombination across the genome and, therefore, high rates of genetic exchange between parental chromosomes.
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6
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Rubio A, García-Blanco N, Vázquez-Bolado A, Belén Suárez M, Moreno S. Nutritional cell cycle reprogramming reveals that inhibition of Cdk1 is required for proper MBF-dependent transcription. J Cell Sci 2018; 131:jcs.218743. [PMID: 30154212 DOI: 10.1242/jcs.218743] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Accepted: 08/20/2018] [Indexed: 01/22/2023] Open
Abstract
In nature, cells and in particular unicellular microorganisms are exposed to a variety of nutritional environments. Fission yeast cells cultured in nitrogen-rich media grow fast, divide with a large size and show a short G1 and a long G2. However, when cultured in nitrogen-poor media, they exhibit reduced growth rate and cell size and a long G1 and a short G2. In this study, we compared the phenotypes of cells lacking the highly conserved cyclin-dependent kinase (Cdk) inhibitor Rum1 and the anaphase-promoting complex/cyclosome (APC/C) activator Ste9 in nitrogen-rich and nitrogen-poor media. Rum1 and Ste9 are dispensable for cell division in nitrogen-rich medium. However, in nitrogen-poor medium they are essential for generating a proper wave of MluI cell-cycle box binding factor (MBF)-dependent transcription at the end of G1, which is crucial for promoting a successful S phase. Mutants lacking Rum1 and Ste9 showed premature entry into S phase and a reduced wave of MBF-dependent transcription, leading to replication stress, DNA damage and G2 cell cycle arrest. This work demonstrates how reprogramming the cell cycle by changing the nutritional environment may reveal new roles for cell cycle regulators.
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Affiliation(s)
- Angela Rubio
- Instituto de Biología Funcional y Genómica, CSIC, University of Salamanca, 37007 Salamanca, Spain.,Department of Microbiology and Genetics, University of Salamanca, 37007 Salamanca. Spain
| | - Natalia García-Blanco
- Instituto de Biología Funcional y Genómica, CSIC, University of Salamanca, 37007 Salamanca, Spain.,Department of Microbiology and Genetics, University of Salamanca, 37007 Salamanca. Spain
| | - Alicia Vázquez-Bolado
- Instituto de Biología Funcional y Genómica, CSIC, University of Salamanca, 37007 Salamanca, Spain.,Department of Microbiology and Genetics, University of Salamanca, 37007 Salamanca. Spain
| | - María Belén Suárez
- Instituto de Biología Funcional y Genómica, CSIC, University of Salamanca, 37007 Salamanca, Spain.,Department of Microbiology and Genetics, University of Salamanca, 37007 Salamanca. Spain
| | - Sergio Moreno
- Instituto de Biología Funcional y Genómica, CSIC, University of Salamanca, 37007 Salamanca, Spain
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7
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Paolillo V, Jenkinson C, Horio T, Oakley B. Cyclins in aspergilli: Phylogenetic and functional analyses of group I cyclins. Stud Mycol 2018; 91:1-22. [PMID: 30104814 PMCID: PMC6078057 DOI: 10.1016/j.simyco.2018.06.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
We have identified the cyclin domain-containing proteins encoded by the genomes of 17 species of Aspergillus as well as 15 members of other genera of filamentous ascomycetes. Phylogenetic analyses reveal that the cyclins fall into three groups, as in other eukaryotic phyla, and, more significantly, that they are remarkably conserved in these fungi. All 32 species examined, for example, have three group I cyclins, cyclins that are particularly important because they regulate the cell cycle, and these are highly conserved. Within the group I cyclins there are three distinct clades, and each fungus has a single member of each clade. These findings are in marked contrast to the yeasts Saccharomyces cerevisiae, Schizosaccharomyces pombe, and Candida albicans, which have more numerous group I cyclins. These results indicate that findings on cyclin function made with a model Aspergillus species, such as A. nidulans, are likely to apply to other Aspergilli and be informative for a broad range of filamentous ascomycetes. In this regard, we note that the functions of only one Aspergillus group I cyclin have been analysed (NimECyclin B of A. nidulans). We have consequently carried out an analysis of the members of the other two clades using A. nidulans as our model. We have found that one of these cyclins, PucA, is essential, but deletion of PucA in a strain carrying a deletion of CdhA, an activator of the anaphase promoting complex/cyclosome (APC/C), is not lethal. These data, coupled with data from heterokaryon rescue experiments, indicate that PucA is an essential G1/S cyclin that is required for the inactivation of the APC/C-CdhA, which, in turn, allows the initiation of the S phase of the cell cycle. Our data also reveal that PucA has additional, non-essential, roles in the cell cycle in interphase. The A. nidulans member of the third clade (AN2137) has not previously been named or analyzed. We designate this gene clbA. ClbA localizes to kinetochores from mid G2 until just prior to chromosomal condensation. Deletion of clbA does not affect viability. However, by using a regulatable promoter system new to Aspergillus, we have found that expression of a version of ClbA in which the destruction box sequences have been removed is lethal and causes a mitotic arrest and a high frequency of non-disjunction. Thus, although ClbA is not essential, its timely destruction is essential for viability, chromosomal disjunction, and successful completion of mitosis.
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Affiliation(s)
- V. Paolillo
- Department of Molecular Biosciences, University of Kansas, 1200 Sunnyside Ave., Lawrence, KS 66045, USA
| | - C.B. Jenkinson
- Department of Molecular Biosciences, University of Kansas, 1200 Sunnyside Ave., Lawrence, KS 66045, USA
| | - T. Horio
- Department of Natural Sciences, Nippon Sport Science University, Yokohama, Japan
| | - B.R. Oakley
- Department of Molecular Biosciences, University of Kansas, 1200 Sunnyside Ave., Lawrence, KS 66045, USA
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8
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Navarro FJ, Chakravarty P, Nurse P. Phosphorylation of the RNA-binding protein Zfs1 modulates sexual differentiation in fission yeast. J Cell Sci 2017; 130:4144-4154. [PMID: 29084823 PMCID: PMC5769579 DOI: 10.1242/jcs.208066] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Accepted: 10/24/2017] [Indexed: 12/21/2022] Open
Abstract
Sexual differentiation in the fission yeast Schizosaccharomyces pombe promotes cell cycle arrest and extensive changes in gene expression, resulting in cell-to-cell fusion, the exchange of hereditary material and specialized cell division. These events are detrimental to the cell if they are triggered in inappropriate conditions, and therefore the decision to differentiate must be precisely controlled. Here, we investigated the role of the RNA-binding protein Zfs1 in this process by identifying its targets and characterizing novel post-translational regulatory mechanisms. We found that Zfs1 negatively regulates the G1 cyclin Puc1, and deregulated Puc1 levels inhibit differentiation in the zfs1Δ mutant. We also found that Zfs1 undergoes phosphorylation, which is stimulated upon nitrogen depletion or inhibition of the TOR pathway. Phosphorylation of Zfs1 modulates accumulation of Puc1 and plays an important role in the response of the cell to sexual differentiation signals. We propose that Zfs1 functions as an integrator of nutrient information to modulate sexual differentiation, contributing to the establishment of the differentiation-activating threshold.
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Affiliation(s)
| | - Probir Chakravarty
- Bioinformatics, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Paul Nurse
- Cell Cycle Laboratory, The Francis Crick Institute, London NW1 1AT, UK
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9
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Swaffer MP, Jones AW, Flynn HR, Snijders AP, Nurse P. CDK Substrate Phosphorylation and Ordering the Cell Cycle. Cell 2016; 167:1750-1761.e16. [PMID: 27984725 PMCID: PMC5161751 DOI: 10.1016/j.cell.2016.11.034] [Citation(s) in RCA: 219] [Impact Index Per Article: 27.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2016] [Revised: 10/14/2016] [Accepted: 11/16/2016] [Indexed: 01/29/2023]
Abstract
S phase and mitotic onset are brought about by the action of multiple different cyclin-CDK complexes. However, it has been suggested that changes in the total level of CDK kinase activity, rather than substrate specificity, drive the temporal ordering of S phase and mitosis. Here, we present a phosphoproteomics-based systems analysis of CDK substrates in fission yeast and demonstrate that the phosphorylation of different CDK substrates can be temporally ordered during the cell cycle by a single cyclin-CDK. This is achieved by rising CDK activity and the differential sensitivity of substrates to CDK activity over a wide dynamic range. This is combined with rapid phosphorylation turnover to generate clearly resolved substrate-specific activity thresholds, which in turn ensures the appropriate ordering of downstream cell-cycle events. Comparative analysis with wild-type cells expressing multiple cyclin-CDK complexes reveals how cyclin-substrate specificity works alongside activity thresholds to fine-tune the patterns of substrate phosphorylation.
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Affiliation(s)
- Matthew P Swaffer
- Cell Cycle Laboratory, The Francis Crick Institute, London NW1 1AT, UK.
| | - Andrew W Jones
- Cell Cycle Laboratory, The Francis Crick Institute, London NW1 1AT, UK; Protein Analysis and Proteomics Platform, The Francis Crick Institute, London NW1 1AT, UK
| | - Helen R Flynn
- Protein Analysis and Proteomics Platform, The Francis Crick Institute, London NW1 1AT, UK
| | - Ambrosius P Snijders
- Protein Analysis and Proteomics Platform, The Francis Crick Institute, London NW1 1AT, UK
| | - Paul Nurse
- Cell Cycle Laboratory, The Francis Crick Institute, London NW1 1AT, UK; Laboratory of Yeast Genetics and Cell Biology, Rockefeller University, New York, NY 10065, USA
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10
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Gutiérrez-Escribano P, Nurse P. A single cyclin-CDK complex is sufficient for both mitotic and meiotic progression in fission yeast. Nat Commun 2015; 6:6871. [PMID: 25891897 PMCID: PMC4411289 DOI: 10.1038/ncomms7871] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Accepted: 03/06/2015] [Indexed: 11/18/2022] Open
Abstract
The dominant model for eukaryotic cell cycle control proposes that cell cycle progression is driven by a succession of CDK complexes with different substrate specificities. However, in fission yeast it has been shown that a single CDK complex generated by the fusion of the Cdc13 cyclin with the CDK protein Cdc2 can drive the mitotic cell cycle. Meiosis is a modified cell cycle programme in which a single S-phase is followed by two consecutive rounds of chromosome segregation. Here we systematically analyse the requirements of the different fission yeast cyclins for meiotic cell cycle progression. We also show that a single Cdc13-Cdc2 complex, in the absence of the other cyclins, can drive the meiotic cell cycle. We propose that qualitatively different CDK complexes are not absolutely required for cell cycle progression either during mitosis or meiosis, and that a single CDK complex can drive both cell cycle programmes.
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Affiliation(s)
| | - Paul Nurse
- Cell Cycle Laboratory Cancer Research UK London Research Institute, London WC2A 3LY, UK
- Laboratory of Yeast Genetics and Cell Biology, Rockefeller University, New York, New York 10065, USA
- The Francis Crick Institute, London NW1 2BE, UK
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11
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Gérard C, Tyson JJ, Coudreuse D, Novák B. Cell cycle control by a minimal Cdk network. PLoS Comput Biol 2015; 11:e1004056. [PMID: 25658582 PMCID: PMC4319789 DOI: 10.1371/journal.pcbi.1004056] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Accepted: 11/21/2014] [Indexed: 12/14/2022] Open
Abstract
In present-day eukaryotes, the cell division cycle is controlled by a complex network of interacting proteins, including members of the cyclin and cyclin-dependent protein kinase (Cdk) families, and the Anaphase Promoting Complex (APC). Successful progression through the cell cycle depends on precise, temporally ordered regulation of the functions of these proteins. In light of this complexity, it is surprising that in fission yeast, a minimal Cdk network consisting of a single cyclin-Cdk fusion protein can control DNA synthesis and mitosis in a manner that is indistinguishable from wild type. To improve our understanding of the cell cycle regulatory network, we built and analysed a mathematical model of the molecular interactions controlling the G1/S and G2/M transitions in these minimal cells. The model accounts for all observed properties of yeast strains operating with the fusion protein. Importantly, coupling the model's predictions with experimental analysis of alternative minimal cells, we uncover an explanation for the unexpected fact that elimination of inhibitory phosphorylation of Cdk is benign in these strains while it strongly affects normal cells. Furthermore, in the strain without inhibitory phosphorylation of the fusion protein, the distribution of cell size at division is unusually broad, an observation that is accounted for by stochastic simulations of the model. Our approach provides novel insights into the organization and quantitative regulation of wild type cell cycle progression. In particular, it leads us to propose a new mechanistic model for the phenomenon of mitotic catastrophe, relying on a combination of unregulated, multi-cyclin-dependent Cdk activities.
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Affiliation(s)
- Claude Gérard
- Oxford Centre for Integrative Systems Biology, Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - John J. Tyson
- Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, United States of America
| | - Damien Coudreuse
- Institut de Génétique et Développement de Rennes, CNRS UMR 6290, Rennes, France
- * E-mail: (DC); (BN)
| | - Béla Novák
- Oxford Centre for Integrative Systems Biology, Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- * E-mail: (DC); (BN)
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12
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Coward J, Harding A. Size Does Matter: Why Polyploid Tumor Cells are Critical Drug Targets in the War on Cancer. Front Oncol 2014; 4:123. [PMID: 24904834 PMCID: PMC4033620 DOI: 10.3389/fonc.2014.00123] [Citation(s) in RCA: 142] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Accepted: 05/11/2014] [Indexed: 12/14/2022] Open
Abstract
Tumor evolution presents a formidable obstacle that currently prevents the development of truly curative treatments for cancer. In this perspective, we advocate for the hypothesis that tumor cells with significantly elevated genomic content (polyploid tumor cells) facilitate rapid tumor evolution and the acquisition of therapy resistance in multiple incurable cancers. We appeal to studies conducted in yeast, cancer models, and cancer patients, which all converge on the hypothesis that polyploidy enables large phenotypic leaps, providing access to many different therapy-resistant phenotypes. We develop a flow-cytometry based method for quantifying the prevalence of polyploid tumor cells, and show the frequency of these cells in patient tumors may be higher than is generally appreciated. We then present recent studies identifying promising new therapeutic strategies that could be used to specifically target polyploid tumor cells in cancer patients. We argue that these therapeutic approaches should be incorporated into new treatment strategies aimed at blocking tumor evolution by killing the highly evolvable, therapy-resistant polyploid cell subpopulations, thus helping to maintain patient tumors in a drug sensitive state.
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Affiliation(s)
- Jermaine Coward
- Mater Medical Research Institute, Princess Alexandra Hospital , Woolloongabba, QLD , Australia
| | - Angus Harding
- The University of Queensland Diamantina Institute, The University of Queensland, Translational Research Institute , Brisbane, QLD , Australia
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13
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De Souza CP, Hashmi SB, Osmani AH, Osmani SA. Application of a new dual localization-affinity purification tag reveals novel aspects of protein kinase biology in Aspergillus nidulans. PLoS One 2014; 9:e90911. [PMID: 24599037 PMCID: PMC3944740 DOI: 10.1371/journal.pone.0090911] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 02/04/2014] [Indexed: 12/22/2022] Open
Abstract
Filamentous fungi occupy critical environmental niches and have numerous beneficial industrial applications but devastating effects as pathogens and agents of food spoilage. As regulators of essentially all biological processes protein kinases have been intensively studied but how they regulate the often unique biology of filamentous fungi is not completely understood. Significant understanding of filamentous fungal biology has come from the study of the model organism Aspergillus nidulans using a combination of molecular genetics, biochemistry, cell biology and genomic approaches. Here we describe dual localization-affinity purification (DLAP) tags enabling endogenous N or C-terminal protein tagging for localization and biochemical studies in A. nidulans. To establish DLAP tag utility we endogenously tagged 17 protein kinases for analysis by live cell imaging and affinity purification. Proteomic analysis of purifications by mass spectrometry confirmed association of the CotA and NimXCdk1 kinases with known binding partners and verified a predicted interaction of the SldABub1/R1 spindle assembly checkpoint kinase with SldBBub3. We demonstrate that the single TOR kinase of A. nidulans locates to vacuoles and vesicles, suggesting that the function of endomembranes as major TOR cellular hubs is conserved in filamentous fungi. Comparative analysis revealed 7 kinases with mitotic specific locations including An-Cdc7 which unexpectedly located to mitotic spindle pole bodies (SPBs), the first such localization described for this family of DNA replication kinases. We show that the SepH septation kinase locates to SPBs specifically in the basal region of apical cells in a biphasic manner during mitosis and again during septation. This results in gradients of SepH between G1 SPBs which shift along hyphae as each septum forms. We propose that SepH regulates the septation initiation network (SIN) specifically at SPBs in the basal region of G1 cells and that localized gradients of SIN activity promote asymmetric septation.
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Affiliation(s)
- Colin P. De Souza
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
| | - Shahr B. Hashmi
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
| | - Aysha H. Osmani
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
| | - Stephen A. Osmani
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, United States of America
- * E-mail:
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14
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Donovan P, Cato K, Legaie R, Jayalath R, Olsson G, Hall B, Olson S, Boros S, Reynolds BA, Harding A. Hyperdiploid tumor cells increase phenotypic heterogeneity within Glioblastoma tumors. MOLECULAR BIOSYSTEMS 2014; 10:741-58. [PMID: 24448662 DOI: 10.1039/c3mb70484j] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Here we report the identification of a proliferative, viable, and hyperdiploid tumor cell subpopulation present within Glioblastoma (GB) patient tumors. Using xenograft tumor models, we demonstrate that hyperdiploid cell populations are maintained in xenograft tumors and that clonally expanded hyperdiploid cells support tumor formation and progression in vivo. In some patient tumorsphere lines, hyperdiploidy is maintained during long-term culture and in vivo within xenograft tumor models, suggesting that hyperdiploidy can be a stable cell state. In other patient lines hyperdiploid cells display genetic drift in vitro and in vivo, suggesting that in these patients hyperdiploidy is a transient cell state that generates novel phenotypes, potentially facilitating rapid tumor evolution. We show that the hyperdiploid cells are resistant to conventional therapy, in part due to infrequent cell division due to a delay in the G₀/G₁ phase of the cell cycle. Hyperdiploid tumor cells are significantly larger and more metabolically active than euploid cancer cells, and this correlates to an increased sensitivity to the effects of glycolysis inhibition. Together these data identify GB hyperdiploid tumor cells as a potentially important subpopulation of cells that are well positioned to contribute to tumor evolution and disease recurrence in adult brain cancer patients, and suggest tumor metabolism as a promising point of therapeutic intervention against this subpopulation.
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Affiliation(s)
- Prudence Donovan
- Ecole polytechnique fédérale de Lausanne EPFL, School of Life Sciences SV, Swiss Institute for Experimental Cancer Research ISREC, Switzerland.
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15
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Davidich MI, Bornholdt S. Boolean network model predicts knockout mutant phenotypes of fission yeast. PLoS One 2013; 8:e71786. [PMID: 24069138 PMCID: PMC3777975 DOI: 10.1371/journal.pone.0071786] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2013] [Accepted: 06/27/2013] [Indexed: 12/02/2022] Open
Abstract
Boolean networks (or: networks of switches) are extremely simple mathematical models of biochemical signaling networks. Under certain circumstances, Boolean networks, despite their simplicity, are capable of predicting dynamical activation patterns of gene regulatory networks in living cells. For example, the temporal sequence of cell cycle activation patterns in yeasts S. pombe and S. cerevisiae are faithfully reproduced by Boolean network models. An interesting question is whether this simple model class could also predict a more complex cellular phenomenology as, for example, the cell cycle dynamics under various knockout mutants instead of the wild type dynamics, only. Here we show that a Boolean network model for the cell cycle control network of yeast S. pombe correctly predicts viability of a large number of known mutants. So far this had been left to the more detailed differential equation models of the biochemical kinetics of the yeast cell cycle network and was commonly thought to be out of reach for models as simplistic as Boolean networks. The new results support our vision that Boolean networks may complement other mathematical models in systems biology to a larger extent than expected so far, and may fill a gap where simplicity of the model and a preference for an overall dynamical blueprint of cellular regulation, instead of biochemical details, are in the focus.
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Affiliation(s)
- Maria I. Davidich
- Institute for Theoretical Physics, University of Bremen, Bremen, Germany
| | - Stefan Bornholdt
- Institute for Theoretical Physics, University of Bremen, Bremen, Germany
- * E-mail:
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16
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Abstract
Cell size is an important adaptive trait that influences nearly all aspects of cellular physiology. Despite extensive characterization of the cell-cycle regulatory network, the molecular mechanisms coupling cell growth to division, and thereby controlling cell size, have remained elusive. Recent work in yeast has reinvigorated the size control field and suggested provocative mechanisms for the distinct functions of setting and sensing cell size. Further examination of size-sensing models based on spatial gradients and molecular titration, coupled with elucidation of the pathways responsible for nutrient-modulated target size, may reveal the fundamental principles of eukaryotic cell size control.
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17
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Uhlmann F, Bouchoux C, López-Avilés S. A quantitative model for cyclin-dependent kinase control of the cell cycle: revisited. Philos Trans R Soc Lond B Biol Sci 2012; 366:3572-83. [PMID: 22084384 PMCID: PMC3203462 DOI: 10.1098/rstb.2011.0082] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The eukaryotic cell division cycle encompasses an ordered series of events. Chromosomal DNA is replicated during S phase of the cell cycle before being distributed to daughter cells in mitosis. Both S phase and mitosis in turn consist of an intricately ordered sequence of molecular events. How cell cycle ordering is achieved, to promote healthy cell proliferation and avert insults on genomic integrity, has been a theme of Paul Nurse's research. To explain a key aspect of cell cycle ordering, sequential S phase and mitosis, Stern & Nurse proposed 'A quantitative model for cdc2 control of S phase and mitosis in fission yeast'. In this model, S phase and mitosis are ordered by their dependence on increasing levels of cyclin-dependent kinase (Cdk) activity. Alternative mechanisms for ordering have been proposed that rely on checkpoint controls or on sequential waves of cyclins with distinct substrate specificities. Here, we review these ideas in the light of experimental evidence that has meanwhile accumulated. Quantitative Cdk control emerges as the basis for cell cycle ordering, fine-tuned by cyclin specificity and checkpoints. We propose a molecular explanation for quantitative Cdk control, based on thresholds imposed by Cdk-counteracting phosphatases, and discuss its implications.
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Affiliation(s)
- Frank Uhlmann
- Chromosome Segregation Laboratory, Cancer Research UK London Research Institute, 44 Lincoln's Inn Fields, London WC2A 3LY, UK.
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Coudreuse D, Nurse P. Driving the cell cycle with a minimal CDK control network. Nature 2010; 468:1074-9. [DOI: 10.1038/nature09543] [Citation(s) in RCA: 300] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2010] [Accepted: 09/28/2010] [Indexed: 01/18/2023]
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20
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Abstract
Cyclin-dependent kinases (CDKs) are key regulators of eukaryotic cell cycle progression. The cyclin subunit activates the CDK and also imparts to the complex, at least in some cases, substrate specificity. Saccharomyces cerevisiae, an organism in which the roles of individual cyclins are best studied, contains nine cyclins (three G(1) cyclins and six B-type cyclins) capable of activating the main cell cycle CDK, Cdc28. Analysis of the genome of the pathogenic yeast Candida albicans revealed only two sequences corresponding to B-type cyclins, C. albicans Clb2 (CaClb2) and CaClb4. Notably, no homolog of the S. cerevisiae S-phase-specific cyclins, Clb5/Clb6, could be detected. Here, we performed an in vitro analysis of the activity of CaClb2 and CaClb4 and of three G(1) cyclins, as well as an analysis of the phenotype of S. cerevisiae cells expressing CaClb2 or CaClb4 instead of Clb5. Remarkably, replacement of CLB5 by CaCLB4 caused rapid diploidization of S. cerevisiae. In addition, both in vivo and in vitro analyses indicate that, in spite of the higher sequence similarity of CaClb2 to Clb5/Clb6, CaClb4 is the functional homolog of Clb5/Clb6. The activity of a CaClb2/CaClb4 cyclin hybrid suggests that the cyclin box domain of CaClb4 carries the functional specificity of the protein. These results have implications for our understanding of the evolution of specificity of the cell cycle cyclins.
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21
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Virtudazo EV, Kawamoto S, Ohkusu M, Aoki S, Sipiczki M, Takeo K. The single Cdk1-G1 cyclin of Cryptococcus neoformans is not essential for cell cycle progression, but plays important roles in the proper commitment to DNA synthesis and bud emergence in this yeast. FEMS Yeast Res 2010; 10:605-18. [PMID: 20528951 DOI: 10.1111/j.1567-1364.2010.00633.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The cell cycle pattern of the pathogenic basidiomycetous yeast Cryptococcus neoformans differs from that of the ascomycetous budding yeast Saccharomyces cerevisiae. To clarify the cell cycle control mechanisms at the molecular level, homologues of cell cycle control genes in C. neoformans were cloned and analyzed. Here, we report on the cloning and characterization of genes coding for CDK1 cyclin homologues, in particular, the C. neoformans G1 cyclin. We have identified three putative CDK1 cyclin homologues and two putative CDK5 (PHO85) cyclin homologues from the genome. Complementation tests in an S. cerevisiae G1 cyclin triple mutant confirmed that C. neoformans CLN1 is able to complement S. cerevisiae G1 cyclin deficiency, demonstrating that it is a G1 cyclin homologue. Interestingly, cells deleted of the single Cdk1-G1 cyclin were viable, demonstrating that this gene is not essential. However, it exhibited aberrant budding and cell division and a clear delay in the initiation of DNA synthesis as well as an extensive delay in budding. The fact that the mutant managed to traverse the G1 to M phase may be due to the activities of Pho85-related G1 cyclins. Also, that C. neoformans had only a single Cdk1-G1 cyclin highlighted the importance of keeping in order the commitment to the initiation of DNA synthesis first and then that of budding, as discussed.
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Affiliation(s)
- Eric V Virtudazo
- Medical Mycology Research Center, Division of Molecular Biology, Chiba University, Chuo-ku, Chiba, Japan
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22
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Abstract
Because the normal control of cell proliferation is disturbed in cancer, the cyclin-dependent kinases (CDKs) that trigger DNA synthesis and mitosis have been popular targets for inhibition with small molecules, but the jury is still out on whether this will be an effective anti-tumor strategy. There is debate about which of the multiple CDKs active during the mammalian cell cycle might be good targets, reflecting fundamental confusion about what, precisely, those different CDKs really do. In the classical view, based largely on their activation timing in cycling cells, different CDKs are specialized to perform discrete functions during distinct cell-cycle intervals. A revisionist model has emerged in which all functions essential to cell division can be performed by a single catalytic subunit, based on the ability of cells to proliferate and animals to survive when individual CDKs are removed by gene deletion or depleted by RNA interference. That those situations in no way resemble ones in which CDKs are inhibited pharmacologically is often overlooked or downplayed. A more nuanced - and accurate - picture is now coming into view, thanks to recent studies that reveal kinetically distinct pathways of activation for closely related CDKs and CDK-specific roles in the temporal control of S phase. The basic question of whether CDKs can be effectively targeted in cancer has yet to be answered but can now be addressed in chemical-genetic model systems that approximate the situation - still hypothetical - of truly selective CDK inhibition in vivo.
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Affiliation(s)
- Robert P Fisher
- Department of Structural and Chemical Biology, Mount Sinai School of Medicine, New York, USA,
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23
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Crosstalk between Nap1 protein and Cds1 checkpoint kinase to maintain chromatin integrity. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2008; 1783:1595-604. [PMID: 18474252 DOI: 10.1016/j.bbamcr.2008.03.019] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2007] [Revised: 03/26/2008] [Accepted: 03/26/2008] [Indexed: 11/22/2022]
Abstract
The nucleosome assembly protein Nap1 has been implicated in various cellular functions such as histone shuttling into the nucleus, nucleosome assembly, chromatin remodelling, transcriptional control and cell-cycle regulation in Saccharomyces cerevisiae. In Schizosaccharomyces pombe nap1 null mutant cells are viable but they showed a delay in the onset of mitosis which is rescued by the absence of the replication Cds1 checkpoint kinase. In contrast, the absence of the DNA-damage Chk1 checkpoint kinase is unable to rescue the delay. Moreover, the double nap1 cds1 mutant cells lose viability and cells show positive H2AX phosphorylation, suggesting that the viability of nap1-deleted cells is due to the Cds1 kinase. We also show that overexpression of Nap1 protein blocks the cell cycle in G1 phase.
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Dischinger S, Krapp A, Xie L, Paulson JR, Simanis V. Chemical genetic analysis of the regulatory role of Cdc2p in the S. pombe septation initiation network. J Cell Sci 2008; 121:843-53. [PMID: 18303049 DOI: 10.1242/jcs.021584] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The protein kinase Cdc2p is the master regulator of cell cycle progression in the fission yeast Schizosaccharomyces pombe. It is required both for entry into mitosis and for onset of DNA replication. Cdc2p must be inactivated to permit exit from mitosis, licensing of replication origins and cytokinesis. To study the role of Cdc2p in greater detail, we generated a cdc2 allele that is sensitive to an inhibitory ATP analogue. We show that the inhibitor-induced cell cycle arrest is reversible and examine the effect of inhibiting Cdc2p on the regulation of the septation initiation network (SIN), which controls the initiation of cytokinesis in S. pombe. We found that specific inactivation of Cdc2p in a mitotically arrested cell promotes the asymmetrical recruitment of SIN proteins to the spindle poles and the recruitment of the most downstream SIN components and beta-(1,3) glucan synthase to the contractile ring. Thus, we conclude that inactivation of Cdc2p is sufficient to activate the SIN and promote cytokinesis.
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25
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Abstract
To maximize the probability of survival and proliferation, cells coordinate various intracellular activities in response to changes in the extracellular environment. Eukaryotic cells transduce diverse cellular stimuli by multiple mitogen-activated protein kinase (MAPK) cascades. Exposure of cells to stress results in rapid activation of a highly conserved family of MAPKs, known as stress-activated protein kinases (SAPKs). Activation of SAPKs results in the generation of a set of adaptive responses that leads to the modulation of several aspects of cell physiology essential for cell survival, such as gene expression, translation, and morphogenesis. This chapter proposes that regulation of cell cycle progression is another general stress response critical for cell survival. Studies from yeast, both Schizosaccharomyces pombe and Saccharomyces cerevisiae, have served to start understanding how SAPKs control cell cycle progression in response to stress.
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Affiliation(s)
- J Clotet
- Department of Molecular and Cellular Biology, Universitat Internacional de Catalunya, Sant Cugat del Vallès, Spain
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26
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Castillo-Lluva S, Pérez-Martín J. The induction of the mating program in the phytopathogen Ustilago maydis is controlled by a G1 cyclin. THE PLANT CELL 2005; 17:3544-60. [PMID: 16258033 PMCID: PMC1315387 DOI: 10.1105/tpc.105.036319] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Our understanding of how cell cycle regulation and virulence are coordinated during the induction of fungal pathogenesis is limited. In the maize smut fungus Ustilago maydis, pathogenesis and sexual development are intricately interconnected. Furthermore, the first step in the infection process is mating, and this is linked to the cell cycle. In this study, we have identified a new G1 cyclin gene from U. maydis that we have named cln1. We investigated the roles of Cln1 in growth and differentiation in U. maydis and found that although not essential for growth, its absence produces dramatic morphological defects. We provide results that are consistent with Cln1 playing a conserved role in regulating the length of G1 and cell size, but also additional morphological functions. We also present experiments indicating that the cyclin Cln1 controls sexual development in U. maydis. Overexpression of cln1 blocks sexual development, while its absence enables the cell to express sexual determinants in conditions where wild-type cells were unable to initiate this developmental program. We conclude that Cln1 contributes to negative regulation of the timing of sexual development, and we propose the existence of a negative crosstalk between mating program and vegetative growth that may help explain why these two developmental options are incompatible in U. maydis.
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Affiliation(s)
- Sonia Castillo-Lluva
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, Campus de Cantoblanco, Universidad Autónoma de Madrid, Spain
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27
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Malapeira J, Moldón A, Hidalgo E, Smith GR, Nurse P, Ayté J. A meiosis-specific cyclin regulated by splicing is required for proper progression through meiosis. Mol Cell Biol 2005; 25:6330-7. [PMID: 16024772 PMCID: PMC1190344 DOI: 10.1128/mcb.25.15.6330-6337.2005] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The meiotic cell cycle is modified from the mitotic cell cycle by having a premeiotic S phase which leads to high levels of recombination, a reductional pattern of chromosome segregation at the first division, and a second division with no intervening DNA synthesis. Cyclin-dependent kinases are essential for progression through the meiotic cell cycle, as for the mitotic cycle. Here we show that a fission yeast cyclin, Rem1, is present only during meiosis. Cells lacking Rem1 have impaired meiotic recombination, and Rem1 is required for premeiotic DNA synthesis when Cig2 is not present. rem1 expression is regulated at the level of both transcription and splicing, with Mei4 as a positive and Cig2 a negative factor of rem1 splicing. This regulation ensures the timely appearance of the different cyclins during meiosis, which is required for the proper progression through the meiotic cell cycle. We propose that the meiosis-specific B-type cyclin Rem1 has a central role in bringing about progression through meiosis.
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Affiliation(s)
- Jordi Malapeira
- The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA
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28
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Uzawa S, Li F, Jin Y, McDonald KL, Braunfeld MB, Agard DA, Cande WZ. Spindle pole body duplication in fission yeast occurs at the G1/S boundary but maturation is blocked until exit from S by an event downstream of cdc10+. Mol Biol Cell 2004; 15:5219-30. [PMID: 15385623 PMCID: PMC532005 DOI: 10.1091/mbc.e04-03-0255] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The regulation and timing of spindle pole body (SPB) duplication and maturation in fission yeast was examined by transmission electron microscopy. When cells are arrested at G1 by nitrogen starvation, the SPB is unduplicated. On release from G1, the SPBs were duplicated after 1-2 h. In cells arrested at S by hydroxyurea, SPBs are duplicated but not mature. In G1 arrest/release experiments with cdc2.33 cells at the restrictive temperature, SPBs remained single, whereas in cells at the permissive temperature, SPBs were duplicated. In cdc10 mutant cells, the SPBs seem not only to be duplicated but also to undergo partial maturation, including invagination of the nuclear envelope underneath the SPB. There may be an S-phase-specific inhibitor of SPB maturation whose expression is under control of cdc10(+). This model was examined by induction of overreplication of the genome by overexpression of rum1p or cdc18p. In cdc18p-overexpressing cells, the SPBs are duplicated but not mature, suggesting that cdc18p is one component of this feedback mechanism. In contrast, cells overexpressing rum1p have large, deformed SPBs accompanied by other features of maturation and duplication. We propose a feedback mechanism for maturation of the SPB that is coupled with exit from S to trigger morphological changes.
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Affiliation(s)
- Satoru Uzawa
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
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29
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Grallert A, Krapp A, Bagley S, Simanis V, Hagan IM. Recruitment of NIMA kinase shows that maturation of the S. pombe spindle-pole body occurs over consecutive cell cycles and reveals a role for NIMA in modulating SIN activity. Genes Dev 2004; 18:1007-21. [PMID: 15132994 PMCID: PMC406291 DOI: 10.1101/gad.296204] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Mitotic exit in Saccharomyces cerevisiae and septation in Schizosaccharomyces pombe are regulated by a conserved signaling network called the mitotic exit and septum initiation networks (SIN), respectively. The network is active on one of the two anaphase B spindle-pole bodies (SPBs). Whereas the inherent asymmetry of growth by budding accounts for elements of the asymmetry in S. cerevisiae, it has been unclear how, or why, the pathway is asymmetric in S. pombe. We show that elements of SPB duplication in S. pombe are conservative, and that the SIN is active on the new SPB. SIN association with the new SPB persists after transient depolymerization of microtubules. The localization of the NIMA-related kinase, Fin1, reveals further complexity in SPB inheritance. Fin1 associates with the SPB bearing the older components in all cells and with the "new" SPB in half of the population. Fin1 only binds the new SPB when this new SPB has arisen from the duplication of an SPB that is two or more cycles old. Thus, each of the four SPBs generated over two consecutive cell cycles are different, because they have distinct fates in the next cell cycle. Fin1 binds the SPB once the SIN is active and the association requires the SIN inhibitors Byr4 and Cdc16. Fin1 physically associates with Byr4. Compromising Fin1 function leads to SIN activation on both anaphase B SPBs and promotes septation, indicating that Fin1 restrains SIN activity on the old SPB.
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Affiliation(s)
- Agnes Grallert
- Cancer Research UK Cell Division Group, Paterson Institute for Cancer Research, Manchester M20 4BX, UK
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30
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Daga RR, Bolaños P, Moreno S. Regulated mRNA Stability of the Cdk Inhibitor Rum1 Links Nutrient Status to Cell Cycle Progression. Curr Biol 2003; 13:2015-24. [PMID: 14653990 DOI: 10.1016/j.cub.2003.10.061] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND The survival of a cell depends on continuous sensing of the nutritional environment and appropriate coordination of the cell cycle. The fission yeast Schizosaccharomyces pombe is an excellent model system in which to study these processes. In the presence of nutrients, fission yeast cells grow and divide, spending most of their time in G2; when nutrients are limiting, they are promoted into mitosis and arrest the cell cycle in G1. The molecular mechanisms underlying this response are currently unknown. RESULTS Here, we show that expression of the fission yeast Cdk inhibitor Rum1, a key regulator of Cdc2/cyclin B in G1, is subject to regulated mRNA stability in response to nutrient deprivation. In complete minimal medium, rum1 mRNAs are very unstable. Following nitrogen starvation, rum1 mRNAs are rapidly stabilized, allowing the accumulation of Rum1 protein to delay the G1 phase of the subsequent cell cycle. Instability of rum1 mRNAs in complete minimal medium depends on the presence of AU-rich elements in the 3'UTR. We also show that lack of this mechanism has consequences in the mitotic cell cycle, in meiosis, and in the control of ploidy. CONCLUSION We propose that mRNA stability is an important mechanism to fine tune the expression of the rum1 gene, in order to allow the production of appropriate levels of Rum1 protein in response to changes in the nutritional environment.
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Affiliation(s)
- Rafael R Daga
- Instituto de Microbiología Bioquímica, Universidad de Salamanca, Campus Miguel de Unamuno, 37007 Salamanca, Spain
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31
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Abstract
Major events of the cell cycle--DNA synthesis, mitosis and cell division-are regulated by a complex network of protein interactions that control the activities of cyclin-dependent kinases. The network can be modeled by a set of nonlinear differential equations and its behavior predicted by numerical simulation. Computer simulations are necessary for detailed quantitative comparisons between theory and experiment, but they give little insight into the qualitative dynamics of the control system and how molecular interactions determine the fundamental physiological properties of cell replication. To that end, bifurcation diagrams are a useful analytical tool, providing new views of the dynamical organization of the cell cycle, the role of checkpoints in assuring the integrity of the genome, and the abnormal regulation of cell cycle events in mutants. These claims are demonstrated by an analysis of cell cycle regulation in fission yeast.
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Affiliation(s)
- John J Tyson
- Department of Biology, Virginia Polytechnic Institute & State University, Blacksburg 24061, USA.
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32
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Abstract
To remain viable, cells have to coordinate cell growth with cell division. In yeast, this occurs at two control points: the boundaries between G1 and S phases, also known as Start, and between G2 and M phases. Theoretically, coordination can be achieved by independent regulation of growth and division, or by participation of surveillance mechanisms in which cell size feeds back into cell-cycle control. This article discusses recent advances in the identification of sizing mechanisms in budding and in fission yeast, and how these mechanisms integrate with environmental stimuli. A comparison of the G1-S and G2-M size-control modules in the two species reveals a degree of conservation higher than previously thought. This reinforces the notion that internal sizing could be a conserved feature of cell-cycle control throughout eukaryotes.
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Affiliation(s)
- Ivan Rupes
- Department of Biology, Queen's University, Kingston, Ontario, Canada K7L 3N6.
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33
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Vas A, Mok W, Leatherwood J. Control of DNA rereplication via Cdc2 phosphorylation sites in the origin recognition complex. Mol Cell Biol 2001; 21:5767-77. [PMID: 11486016 PMCID: PMC87296 DOI: 10.1128/mcb.21.17.5767-5777.2001] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cdc2 kinase is a master regulator of cell cycle progression in the fission yeast Schizosaccharomyces pombe. Our data indicate that Cdc2 phosphorylates replication factor Orp2, a subunit of the origin recognition complex (ORC). Cdc2 phosphorylation of Orp2 appears to be one of multiple mechanisms by which Cdc2 prevents DNA rereplication in a single cell cycle. Cdc2 phosphorylation of Orp2 is not required for Cdc2 to activate DNA replication initiation. Phosphorylation of Orp2 appears first in S phase and becomes maximal in G(2) and M when Cdc2 kinase activity is required to prevent reinitiation of DNA replication. A mutant lacking Cdc2 phosphorylation sites in Orp2 (orp2-T4A) allowed greater rereplication of DNA than congenic orp2 wild-type strains when the limiting replication initiation factor Cdc18 was deregulated. Thus, Cdc2 phosphorylation of Orp2 may be redundant with regulation of Cdc18 for preventing reinitiation of DNA synthesis. Since Cdc2 phosphorylation sites are present in Orp2 (also known as Orc2) from yeasts to metazoans, we propose that cell cycle-regulated phosphorylation of the ORC provides a safety net to prevent DNA rereplication and resulting genetic instability.
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Affiliation(s)
- A Vas
- Department of Molecular Genetics and Microbiology, State University of New York, Stony Brook, NY 11794-5222, USA
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34
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Sveiczer A, Tyson JJ, Novak B. A stochastic, molecular model of the fission yeast cell cycle: role of the nucleocytoplasmic ratio in cycle time regulation. Biophys Chem 2001; 92:1-15. [PMID: 11527575 DOI: 10.1016/s0301-4622(01)00183-1] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
We propose a stochastic version of a recently published, deterministic model of the molecular mechanism regulating the mitotic cell cycle of fission yeast, Schizosaccharomyces pombe. Stochasticity is introduced in two ways: (i) by considering the known asymmetry of cell division, which produces daughter cells of slightly different sizes; and (ii) by assuming that the nuclear volumes of the two newborn cells may also differ. In this model, the accumulation of cyclins in the nucleus is proportional to the ratio of cytoplasmic to nuclear volumes. We have simulated the cell-cycle statistics of populations of wild-type cells and of wee1(-) mutant cells. Our results are consistent with well known experimental observations.
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Affiliation(s)
- A Sveiczer
- Department of Agricultural Chemical Technology, Budapest University of Technology and Economics, 1521 Budapest, Szt. Gellert ter 4, Hungary.
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35
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Affiliation(s)
- J W Harper
- Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA.
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36
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Abstract
Cyclin-dependent kinase (CDK) activity is essential for eukaryotic cell cycle events. Multiple cyclins activate CDKs in all eukaryotes, but it is unclear whether multiple cyclins are really required for cell cycle progression. It has been argued that cyclins may predominantly act as simple enzymatic activators of CDKs; in opposition to this idea, it has been argued that cyclins might target the activated CDK to particular substrates or inhibitors. Such targeting might occur through a combination of factors, including temporal expression, protein associations, and subcellular localization.
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Affiliation(s)
- M E Miller
- The Rockefeller University, New York, NY 10021, USA
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37
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Novak B, Pataki Z, Ciliberto A, Tyson JJ. Mathematical model of the cell division cycle of fission yeast. CHAOS (WOODBURY, N.Y.) 2001; 11:277-286. [PMID: 12779461 DOI: 10.1063/1.1345725] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Much is known about the genes and proteins controlling the cell cycle of fission yeast. Can these molecular components be spun together into a consistent mechanism that accounts for the observed behavior of growth and division in fission yeast cells? To answer this question, we propose a mechanism for the control system, convert it into a set of 14 differential and algebraic equations, study these equations by numerical simulation and bifurcation theory, and compare our results to the physiology of wild-type and mutant cells. In wild-type cells, progress through the cell cycle (G1-->S-->G2-->M) is related to cyclic progression around a hysteresis loop, driven by cell growth and chromosome alignment on the metaphase plate. However, the control system operates much differently in double-mutant cells, wee1(-) cdc25Delta, which are defective in progress through the latter half of the cell cycle (G2 and M phases). These cells exhibit "quantized" cycles (interdivision times clustering around 90, 160, and 230 min). We show that these quantized cycles are associated with a supercritical Hopf bifurcation in the mechanism, when the wee1 and cdc25 genes are disabled. (c) 2001 American Institute of Physics.
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Affiliation(s)
- Bela Novak
- Department of Agricultural Chemical Technology, Budapest University of Technology and Economics, Szt Gellert ter 4, 1111 Budapest, Hungary
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38
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John PC, Mews M, Moore R. Cyclin/Cdk complexes: their involvement in cell cycle progression and mitotic division. PROTOPLASMA 2001; 216:119-142. [PMID: 11732181 DOI: 10.1007/bf02673865] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
DNA replication and mitosis are dependent on the activity of cyclin-dependent protein kinase (CDK) enzymes, which are heterodimers of a catalytic subunit with a cyclin subunit. Cyclin binding to specific individual proteins is thought to provide potential substrates to Cdk. Protein binding by cyclins is assessed in terms of its mechanisms and biological significance, using evidence from diverse organisms including substrate specificity in animal Cdk enzymes containing D-, A-, and B-type cyclins and extensive cyclin gene manipulations in yeasts. Assembly of protein complexes with cyclin/Cdk is noted and the capacity of the cyclin-dependent kinase subunit Cks, in such complex, to extend the range of Cdk substrates is documented and discussed in terms of cell cycle regulation. Cell cycle progression involves changing abundance of individual cyclins, due to changing rates of their transcription or proteolysis, with consequent changes in the substrates of CDK through the cell cycle. Some overlap of the functions of individual cyclins in vivo has been identified by cyclin deletions and is suggested to follow a pattern in which cyclins can commonly complete functions initiated by the preceding cyclins well enough to preserve viability as groups of cyclins are removed by proteolysis. Cyclin accumulation is particularly important in terminating the G1 phase, when it raises CDK activity and starts events leading to DNA replication. It is suggested that plants share this mechanism. The distribution of cyclins and Cdk in maize root tip cells during mitosis and cytokinesis indicates the presence of Cdk1 (Cdc2a) and cyclin CycB1zm;2 at the mature and disassembling preprophase band and the presence of CycB1zm;2 at condensing and condensed chromosomes. Both observations correlate with the earlier-reported capacity of injected metaphase cyclin/CDK to accelerate preprophase band disassembly and chromosome condensation and with observations of the location of Cdk and cyclins in other laboratories. Additionally CycB1zm;2 is seen at the nuclear envelope during its breakdown, which correlates with an acceleration of the process by injected metaphase cyclin B/CDK. A phenomenon possibly unique to the plant kingdom is the persistence of mitotic cyclins after anaphase. Participation of cyclins in cytokinesis is indicated by the concentration of the mitotic cyclin CycA1;zm;1 at the phragmoplast. It is suggested that cyclins have a general function of spatially focusing Cdk activity and that in the plant cell the concentrations of cyclins are important mediators of CDK activity at the cytoskeleton, chromosomes, spindle, nuclear envelope, and phragmoplast.
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Affiliation(s)
- P C John
- Plant Cell Biology Group, Research School of Biological Sciences, Australian National University, Canberra, ACT 2601, Australia
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39
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Abstract
Cdc2, a cyclin-dependent kinase, controls cell cycle progression in fission yeast. New details of Cdc2 regulation and function have been uncovered in recent studies. These studies involve cyclins that associate with Cdc2 in G1-phase and the proteins that regulate inhibitory phosphorylation of Cdc2 during S-phase and G2-phase. Recent investigations have also provided a better understanding of proteins that regulate DNA replication and that are directly or indirectly controlled by Cdc2.
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Affiliation(s)
- B A Moser
- Department of Molecular Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.
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40
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Abstract
Over the past 25 years, the genetic control of cell size has mainly been addressed in yeast, a single-celled organism. Recent insights from Drosophila have shed light on the signalling pathways responsible for adjusting and maintaining cell size in metazoans. Evidence is emerging for a signalling cascade conserved in evolution that links external nutrient sources to cell size.
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Affiliation(s)
- H Stocker
- Zoologisches Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057, Zürich, Switzerland
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41
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Grishchuk EL, Frolov DY, Savchenko GV. Overexpression ofapc10 + in fission yeast can suppress the temperature sensitivity ofnuc2-663 mutant but not its sterility. Mol Biol 2000. [DOI: 10.1007/bf02759608] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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42
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Tanaka K, Okayama H. A pcl-like cyclin activates the Res2p-Cdc10p cell cycle "start" transcriptional factor complex in fission yeast. Mol Biol Cell 2000; 11:2845-62. [PMID: 10982385 PMCID: PMC14960 DOI: 10.1091/mbc.11.9.2845] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2000] [Revised: 06/02/2000] [Accepted: 06/26/2000] [Indexed: 11/11/2022] Open
Abstract
In the fission yeast Schizosaccharomyces pombe, the "start" of the cell cycle is controlled by the two functionally redundant transcriptional regulator complexes, Res1p-Cdc10p and Res2p-Cdc10p, that activate genes essential for the onset and progression of S phase. The activity of the Res2p-Cdc10p complex is regulated at least by the availability of the Rep2 trans-activator subunit in the mitotic cell cycle. We have recently isolated the pas1(+) gene as a multicopy suppressor of the res1 null mutant. This gene encodes a novel cyclin that shares homology with the Pho85 kinase-associated cyclins of the budding yeast Saccharomyces cerevisiae. Genetic analysis reveals that Pas1 cyclin is unrelated to phosphate metabolism and stimulates the G(1)-S transition by specifically activating the Res2p-Cdc10p complex independently of Rep2p. Pas1 cyclin also controls mating pheromone signaling. Cells lacking pas1(+) are highly sensitive to mating pheromone, responding with facilitated G(1) arrest and premature commitment to conjugation. Pas1 cyclin associates in vivo with both Cdc2 and Pef1 kinases, the latter of which is a fission yeast counterpart of the budding yeast Pho85 kinase, but genetic analysis indicates that the Pef1p-associated Pas1p is responsible for the activation of Res2p-Cdc10p during the G(1)-S transition.
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Affiliation(s)
- K Tanaka
- Department of Biochemistry and Molecular Biology, The University of Tokyo, Graduate School of Medicine, Bunkyo-ku, Tokyo 113-0033, Japan
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43
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Blanco MA, Sánchez-Díaz A, de Prada JM, Moreno S. APC(ste9/srw1) promotes degradation of mitotic cyclins in G(1) and is inhibited by cdc2 phosphorylation. EMBO J 2000; 19:3945-55. [PMID: 10921876 PMCID: PMC306614 DOI: 10.1093/emboj/19.15.3945] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Fission yeast ste9/srw1 is a WD-repeat protein highly homologous to budding yeast Hct1/Cdh1 and Drosophila Fizzy-related that are involved in activating APC/C (anaphase-promoting complex/cyclosome). We show that APC(ste9/srw1) specifically promotes the degradation of mitotic cyclins cdc13 and cig1 but not the S-phase cyclin cig2. APC(ste9/srw1) is not necessary for the proteolysis of cdc13 and cig1 that occurs at the metaphase-anaphase transition but it is absolutely required for their degradation in G(1). Therefore, we propose that the main role of APC(ste9/srw1) is to promote degradation of mitotic cyclins when cells need to delay or arrest the cell cycle in G(1). We also show that ste9/srw1 is negatively regulated by cdc2-dependent protein phosphorylation. In G(1), when cdc2-cyclin kinase activity is low, unphosphorylated ste9/srw1 interacts with APC/C. In the rest of the cell cycle, phosphorylation of ste9/srw1 by cdc2-cyclin complexes both triggers proteolysis of ste9/srw1 and causes its dissociation from the APC/C. This mechanism provides a molecular switch to prevent inactivation of cdc2 in G(2) and early mitosis and to allow its inactivation in G(1).
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Affiliation(s)
- M A Blanco
- Instituto de Microbiología Bioquímica, Departamento de Microbiología y Genética, CSIC/Universidad de Salamanca, Edificio Departamental, Campus Miguel de Unamuno, 37007 Salamanca, Spain
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