1
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Su AJ, Yendluri SC, Ünal E. Control of meiotic entry by dual inhibition of a key mitotic transcription factor. eLife 2024; 12:RP90425. [PMID: 38411169 PMCID: PMC10939502 DOI: 10.7554/elife.90425] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/28/2024] Open
Abstract
The mitosis to meiosis transition requires dynamic changes in gene expression, but whether and how the mitotic transcriptional machinery is regulated during this transition is unknown. In budding yeast, SBF and MBF transcription factors initiate the mitotic gene expression program. Here, we report two mechanisms that work together to restrict SBF activity during meiotic entry: repression of the SBF-specific Swi4 subunit through LUTI-based regulation and inhibition of SBF by Whi5, a functional homolog of the Rb tumor suppressor. We find that untimely SBF activation causes downregulation of early meiotic genes and delays meiotic entry. These defects are largely driven by the SBF-target G1 cyclins, which block the interaction between the central meiotic regulator Ime1 and its cofactor Ume6. Our study provides insight into the role of SWI4LUTI in establishing the meiotic transcriptional program and demonstrates how the LUTI-based regulation is integrated into a larger regulatory network to ensure timely SBF activity.
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Affiliation(s)
- Amanda J Su
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Siri C Yendluri
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Elçin Ünal
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
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2
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Su AJ, Yendluri SC, Ünal E. Control of meiotic entry by dual inhibition of a key mitotic transcription factor. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.17.533246. [PMID: 36993411 PMCID: PMC10055192 DOI: 10.1101/2023.03.17.533246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
Abstract
The mitosis to meiosis transition requires dynamic changes in gene expression, but whether and how the mitotic transcriptional machinery is regulated during this transition is unknown. In budding yeast, SBF and MBF transcription factors initiate the mitotic gene expression program. Here, we report two mechanisms that work together to restrict SBF activity during meiotic entry: repression of the SBF-specific Swi4 subunit through LUTI-based regulation and inhibition of SBF by Whi5, a homolog of the Rb tumor suppressor. We find that untimely SBF activation causes downregulation of early meiotic genes and delays meiotic entry. These defects are largely driven by the SBF-target G1 cyclins, which block the interaction between the central meiotic regulator Ime1 and its cofactor Ume6. Our study provides insight into the role of SWI4LUTI in establishing the meiotic transcriptional program and demonstrates how the LUTI-based regulation is integrated into a larger regulatory network to ensure timely SBF activity.
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3
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Jiménez-Gutiérrez E, Fernández-Acero T, Alonso-Rodríguez E, Molina M, Martín H. Neomycin Interferes with Phosphatidylinositol-4,5-Bisphosphate at the Yeast Plasma Membrane and Activates the Cell Wall Integrity Pathway. Int J Mol Sci 2022; 23:ijms231911034. [PMID: 36232332 PMCID: PMC9569482 DOI: 10.3390/ijms231911034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Revised: 09/14/2022] [Accepted: 09/15/2022] [Indexed: 11/20/2022] Open
Abstract
The cell wall integrity pathway (CWI) is a MAPK-mediated signaling route essential for yeast cell response to cell wall damage, regulating distinct aspects of fungal physiology. We have recently proven that the incorporation of a genetic circuit that operates as a signal amplifier into this pathway allows for the identification of novel elements involved in CWI signaling. Here, we show that the strong growth inhibition triggered by pathway hyperactivation in cells carrying the “Integrity Pathway Activation Circuit” (IPAC) also allows the easy identification of new stimuli. By using the IPAC, we have found various chemical agents that activate the CWI pathway, including the aminoglycoside neomycin. Cells lacking key components of this pathway are sensitive to this antibiotic, due to the disruption of signaling upon neomycin stimulation. Neomycin reduces both phosphatidylinositol-4,5-bisphosphate (PIP2) availability at the plasma membrane and myriocin-induced TORC2-dependent Ypk1 phosphorylation, suggesting a strong interference with plasma membrane homeostasis, specifically with PIP2. The neomycin-induced transcriptional profile involves not only genes related to stress and cell wall biogenesis, but also to amino acid metabolism, reflecting the action of this antibiotic on the yeast ribosome.
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Affiliation(s)
| | | | | | - María Molina
- Correspondence: (M.M.); (H.M.); Tel.: +34-91-394-1888 (M.M. & H.M.)
| | - Humberto Martín
- Correspondence: (M.M.); (H.M.); Tel.: +34-91-394-1888 (M.M. & H.M.)
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4
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Pérez AP, Artés MH, Moreno DF, Clotet J, Aldea M. Mad3 modulates the G 1 Cdk and acts as a timer in the Start network. SCIENCE ADVANCES 2022; 8:eabm4086. [PMID: 35522754 PMCID: PMC9075807 DOI: 10.1126/sciadv.abm4086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/25/2021] [Accepted: 03/23/2022] [Indexed: 06/14/2023]
Abstract
Cells maintain their size within limits over successive generations to maximize fitness and survival. Sizer, timer, and adder behaviors have been proposed as possible alternatives to coordinate growth and cell cycle progression. Regarding budding yeast cells, a sizer mechanism is thought to rule cell cycle entry at Start. However, while many proteins controlling the size of these cells have been identified, the mechanistic framework in which they participate to achieve cell size homeostasis is not understood. We show here that intertwined APC and SCF degradation machineries with specific adaptor proteins drive cyclic accumulation of the G1 Cdk in the nucleus, reaching maximal levels at Start. The mechanism incorporates Mad3, a centromeric-signaling protein that subordinates G1 progression to the previous mitosis as a memory factor. This alternating-degradation device displays the properties of a timer and, together with the sizer device, would constitute a key determinant of cell cycle entry.
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Affiliation(s)
- Alexis P. Pérez
- Molecular Biology Institute of Barcelona (IBMB), CSIC, 08028 Barcelona, Catalonia, Spain
- Department of Basic Sciences, Universitat Internacional de Catalunya, 08195 Sant Cugat del Vallès, Spain
| | - Marta H. Artés
- Molecular Biology Institute of Barcelona (IBMB), CSIC, 08028 Barcelona, Catalonia, Spain
| | - David F. Moreno
- Molecular Biology Institute of Barcelona (IBMB), CSIC, 08028 Barcelona, Catalonia, Spain
| | - Josep Clotet
- Department of Basic Sciences, Universitat Internacional de Catalunya, 08195 Sant Cugat del Vallès, Spain
| | - Martí Aldea
- Molecular Biology Institute of Barcelona (IBMB), CSIC, 08028 Barcelona, Catalonia, Spain
- Department of Basic Sciences, Universitat Internacional de Catalunya, 08195 Sant Cugat del Vallès, Spain
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5
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Sommer RA, DeWitt JT, Tan R, Kellogg DR. Growth-dependent signals drive an increase in early G1 cyclin concentration to link cell cycle entry with cell growth. eLife 2021; 10:64364. [PMID: 34713806 PMCID: PMC8592568 DOI: 10.7554/elife.64364] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 10/29/2021] [Indexed: 01/13/2023] Open
Abstract
Entry into the cell cycle occurs only when sufficient growth has occurred. In budding yeast, the cyclin Cln3 is thought to initiate cell cycle entry by inactivating a transcriptional repressor called Whi5. Growth-dependent changes in the concentrations of Cln3 or Whi5 have been proposed to link cell cycle entry to cell growth. However, there are conflicting reports regarding the behavior and roles of Cln3 and Whi5. Here, we found no evidence that changes in the concentration of Whi5 play a major role in controlling cell cycle entry. Rather, the data suggest that cell growth triggers cell cycle entry by driving an increase in the concentration of Cln3. We further found that accumulation of Cln3 is dependent upon homologs of mammalian SGK kinases that control cell growth and size. Together, the data are consistent with models in which Cln3 is a crucial link between cell growth and the cell cycle.
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Affiliation(s)
- Robert A Sommer
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, United States
| | - Jerry T DeWitt
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, United States
| | - Raymond Tan
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, United States
| | - Douglas R Kellogg
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, United States
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6
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Montella-Manuel S, Pujol-Carrion N, de la Torre-Ruiz MA. The Cell Wall Integrity Receptor Mtl1 Contributes to Articulate Autophagic Responses When Glucose Availability Is Compromised. J Fungi (Basel) 2021; 7:jof7110903. [PMID: 34829194 PMCID: PMC8623553 DOI: 10.3390/jof7110903] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 10/21/2021] [Accepted: 10/23/2021] [Indexed: 01/02/2023] Open
Abstract
Mtl1protein is a cell wall receptor belonging to the CWI pathway. Mtl1 function is related to glucose and oxidative stress signaling. In this report, we show data demonstrating that Mtl1 plays a critical role in the detection of a descent in glucose concentration, in order to activate bulk autophagy machinery as a response to nutrient deprivation and to maintain cell survival in starvation conditions. Autophagy is a tightly regulated mechanism involving several signaling pathways. The data here show that in Saccharomyces cerevisiae, Mtl1 signals glucose availability to either Ras2 or Sch9 proteins converging in Atg1 phosphorylation and autophagy induction. TORC1 complex function is not involved in autophagy induction during the diauxic shift when glucose is limited. In this context, the GCN2 gene is required to regulate autophagy activation upon amino acid starvation independent of the TORC1 complex. Mtl1 function is also involved in signaling the autophagic degradation of mitochondria during the stationary phase through both Ras2 and Sch9, in a manner dependent on either Atg33 and Atg11 proteins and independent of the Atg32 protein, the mitophagy receptor. All of the above suggest a pivotal signaling role for Mtl1 in maintaining correct cell homeostasis function in periods of glucose scarcity in budding yeast.
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7
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Yahya G, Pérez AP, Mendoza MB, Parisi E, Moreno DF, Artés MH, Gallego C, Aldea M. Stress granules display bistable dynamics modulated by Cdk. J Cell Biol 2021; 220:211705. [PMID: 33480968 PMCID: PMC7836273 DOI: 10.1083/jcb.202005102] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 11/27/2020] [Accepted: 12/23/2020] [Indexed: 12/20/2022] Open
Abstract
Stress granules (SGs) are conserved biomolecular condensates that originate in response to many stress conditions. These membraneless organelles contain nontranslating mRNAs and a diverse subproteome, but our knowledge of their regulation and functional relevance is still incipient. Here, we describe a mutual-inhibition interplay between SGs and Cdc28, the budding yeast Cdk. Among Cdc28 interactors acting as negative modulators of Start, we have identified Whi8, an RNA-binding protein that localizes to SGs and recruits the mRNA of CLN3, the most upstream G1 cyclin, for efficient translation inhibition and Cdk inactivation under stress. However, Whi8 also contributes to recruiting Cdc28 to SGs, where it acts to promote their dissolution. As predicted by a mutual-inhibition framework, the SG constitutes a bistable system that is modulated by Cdk. Since mammalian cells display a homologous mechanism, we propose that the opposing functions of specific mRNA-binding proteins and Cdk’s subjugate SG dynamics to a conserved hysteretic switch.
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Affiliation(s)
- Galal Yahya
- Molecular Biology Institute of Barcelona, Spanish National Research Council, Catalonia, Spain.,Department of Microbiology and Immunology, Zagazig University, Zagazig, Egypt
| | - Alexis P Pérez
- Molecular Biology Institute of Barcelona, Spanish National Research Council, Catalonia, Spain.,Department of Basic Sciences, Universitat Internacional de Catalunya, Barcelona, Spain
| | - Mònica B Mendoza
- Molecular Biology Institute of Barcelona, Spanish National Research Council, Catalonia, Spain
| | - Eva Parisi
- Molecular Biology Institute of Barcelona, Spanish National Research Council, Catalonia, Spain
| | - David F Moreno
- Molecular Biology Institute of Barcelona, Spanish National Research Council, Catalonia, Spain
| | - Marta H Artés
- Molecular Biology Institute of Barcelona, Spanish National Research Council, Catalonia, Spain
| | - Carme Gallego
- Molecular Biology Institute of Barcelona, Spanish National Research Council, Catalonia, Spain
| | - Martí Aldea
- Molecular Biology Institute of Barcelona, Spanish National Research Council, Catalonia, Spain.,Department of Basic Sciences, Universitat Internacional de Catalunya, Barcelona, Spain
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8
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Di Caprio F. Cultivation processes to select microorganisms with high accumulation ability. Biotechnol Adv 2021; 49:107740. [PMID: 33838283 DOI: 10.1016/j.biotechadv.2021.107740] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Revised: 02/26/2021] [Accepted: 03/26/2021] [Indexed: 10/21/2022]
Abstract
The microbial ability to accumulate biomolecules is fundamental for different biotechnological applications aiming at the production of biofuels, food and bioplastics. However, high accumulation is a selective advantage only under certain stressful conditions, such as nutrient depletion, characterized by lower growth rate. Conventional bioprocesses maintain an optimal and stable environment for large part of the cultivation, that doesn't reward cells for their accumulation ability, raising the risk of selection of contaminant strains with higher growth rate, but lower accumulation of products. Here in this work the physiological responses of different microorganisms (microalgae, bacteria, yeasts) under N-starvation and energy starvation are reviewed, with the aim to furnish relevant insights exploitable to develop tailored bioprocesses to select specific strains for their higher accumulation ability. Microorganism responses to starvation are reviewed focusing on cell cycle, biomass production and variations in biochemical composition. Then, the work describes different innovative bioprocess configurations exploiting uncoupled nutrient feeding strategies (feast-famine), tailored to maintain a selective pressure to reward the strains with higher accumulation ability in mixed microbial populations. Finally, the main models developed in recent studies to describe and predict microbial growth and intracellular accumulation upon N-starvation and feast-famine conditions have been reviewed.
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Affiliation(s)
- Fabrizio Di Caprio
- Department of Chemistry, University Sapienza of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy.
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9
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Bulk autophagy induction and life extension is achieved when iron is the only limited nutrient in Saccharomyces cerevisiae. Biochem J 2021; 478:811-837. [DOI: 10.1042/bcj20200849] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 01/26/2021] [Accepted: 01/27/2021] [Indexed: 01/21/2023]
Abstract
We have investigated the effects that iron limitation provokes in Saccharomyces cerevisiae exponential cultures. We have demonstrated that one primary response is the induction of bulk autophagy mediated by TORC1. Coherently, Atg13 became dephosphorylated whereas Atg1 appeared phosphorylated. The signal of iron deprivation requires Tor2/Ypk1 activity and the inactivation of Tor1 leading to Atg13 dephosphorylation, thus triggering the autophagy process. Iron replenishment in its turn, reduces autophagy flux through the AMPK Snf1 and the subsequent activity of the iron-responsive transcription factor, Aft1. This signalling converges in Atg13 phosphorylation mediated by Tor1. Iron limitation promotes accumulation of trehalose and the increase in stress resistance leading to a quiescent state in cells. All these effects contribute to the extension of the chronological life, in a manner totally dependent on autophagy activation.
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10
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Méndez E, Gomar-Alba M, Bañó MC, Mendoza M, Quilis I, Igual JC. The budding yeast Start repressor Whi7 differs in regulation from Whi5, emerging as a major cell cycle brake in response to stress. J Cell Sci 2020; 133:133/24/jcs251413. [PMID: 33443080 PMCID: PMC7774886 DOI: 10.1242/jcs.251413] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Accepted: 11/09/2020] [Indexed: 11/20/2022] Open
Abstract
Start is the main decision point in the eukaryotic cell cycle at which cells commit to a new round of cell division. It involves the irreversible activation of a transcriptional programme through the inactivation of Start transcriptional repressors: the retinoblastoma family in mammals, or Whi5 and its recently identified paralogue Whi7 (also known as Srl3) in budding yeast. Here, we provide a comprehensive comparison of Whi5 and Whi7 that reveals significant qualitative differences. Indeed, the expression, subcellular localization and functionality of Whi7 and Whi5 are differentially regulated. Importantly, Whi7 shows specific properties in its association with promoters not shared by Whi5, and for the first time, we demonstrate that Whi7, and not Whi5, can be the main contributor to Start inhibition such as it occurs in the response to cell wall stress. Our results help to improve understanding of the interplay between multiple differentially regulated Start repressors in order to face specific cellular conditions. Highlighted Article: Cells can use the interplay between functionally redundant but differentially regulated cell-cycle repressors in order to confer new repression capabilities and to respond to specific cellular conditions.
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Affiliation(s)
- Ester Méndez
- Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BIOTECMED) and Departament de Bioquímica i Biologia Molecular, Universitat de València, 46100 Burjassot (Valencia), Spain
| | - Mercè Gomar-Alba
- Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BIOTECMED) and Departament de Bioquímica i Biologia Molecular, Universitat de València, 46100 Burjassot (Valencia), Spain.,Institut de Génétique et de Biologie Moléculaire et Cellulaire, 67404 Illkirch, France.,Centre National de la Recherche Scientifique, UMR7104, 67404 Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U964, 67404 Illkirch, France.,Université de Strasbourg, 67000 Strasbourg, France
| | - M Carmen Bañó
- Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BIOTECMED) and Departament de Bioquímica i Biologia Molecular, Universitat de València, 46100 Burjassot (Valencia), Spain
| | - Manuel Mendoza
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, 67404 Illkirch, France.,Centre National de la Recherche Scientifique, UMR7104, 67404 Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U964, 67404 Illkirch, France.,Université de Strasbourg, 67000 Strasbourg, France
| | - Inma Quilis
- Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BIOTECMED) and Departament de Bioquímica i Biologia Molecular, Universitat de València, 46100 Burjassot (Valencia), Spain
| | - J Carlos Igual
- Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BIOTECMED) and Departament de Bioquímica i Biologia Molecular, Universitat de València, 46100 Burjassot (Valencia), Spain
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11
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Mitochondrial Localization of the Yeast Forkhead Factor Hcm1. Int J Mol Sci 2020; 21:ijms21249574. [PMID: 33339134 PMCID: PMC7765673 DOI: 10.3390/ijms21249574] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Revised: 12/10/2020] [Accepted: 12/14/2020] [Indexed: 12/24/2022] Open
Abstract
Hcm1 is a member of the forkhead transcription factor family involved in segregation, spindle pole dynamics, and budding in Saccharomyces cerevisiae. Our group described the role of Hcm1 in mitochondrial biogenesis and stress resistance, and in the cellular adaptation to mitochondrial respiratory metabolism when nutrients decrease. Regulation of Hcm1 activity occurs at the protein level, subcellular localization, and transcriptional activity. Here we report that the amount of protein increased in the G1/S transition phase when the factor accumulated in the nucleus. In the G2/M phases, the Hcm1 amount decreased, and it was translocated outside the nucleus with a network-like localization. Preparation of highly purified mitochondria by a sucrose gradient density demonstrated that Hcm1 colocalized with mitochondrial markers, inducing expression of COX1, a mitochondrial encoded subunit of cytochrome oxidase, in the G2/M phases. Taken together, these results show a new localization of Hcm1 and suggest that it acts as a mitochondrial transcription factor regulating the metabolism of this organelle.
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12
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The Smc5/6 Core Complex Is a Structure-Specific DNA Binding and Compacting Machine. Mol Cell 2020; 80:1025-1038.e5. [PMID: 33301731 DOI: 10.1016/j.molcel.2020.11.011] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2019] [Revised: 10/13/2020] [Accepted: 11/04/2020] [Indexed: 01/09/2023]
Abstract
The structural organization of chromosomes is a crucial feature that defines the functional state of genes and genomes. The extent of structural changes experienced by genomes of eukaryotic cells can be dramatic and spans several orders of magnitude. At the core of these changes lies a unique group of ATPases-the SMC proteins-that act as major effectors of chromosome behavior in cells. The Smc5/6 proteins play essential roles in the maintenance of genome stability, yet their mode of action is not fully understood. Here we show that the human Smc5/6 complex recognizes unusual DNA configurations and uses the energy of ATP hydrolysis to promote their compaction. Structural analyses reveal subunit interfaces responsible for the functionality of the Smc5/6 complex and how mutations in these regions may lead to chromosome breakage syndromes in humans. Collectively, our results suggest that the Smc5/6 complex promotes genome stability as a DNA micro-compaction machine.
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13
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The Path towards Predicting Evolution as Illustrated in Yeast Cell Polarity. Cells 2020; 9:cells9122534. [PMID: 33255231 PMCID: PMC7760196 DOI: 10.3390/cells9122534] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 11/18/2020] [Accepted: 11/21/2020] [Indexed: 01/14/2023] Open
Abstract
A bottom-up route towards predicting evolution relies on a deep understanding of the complex network that proteins form inside cells. In a rapidly expanding panorama of experimental possibilities, the most difficult question is how to conceptually approach the disentangling of such complex networks. These can exhibit varying degrees of hierarchy and modularity, which obfuscate certain protein functions that may prove pivotal for adaptation. Using the well-established polarity network in budding yeast as a case study, we first organize current literature to highlight protein entrenchments inside polarity. Following three examples, we see how alternating between experimental novelties and subsequent emerging design strategies can construct a layered understanding, potent enough to reveal evolutionary targets. We show that if you want to understand a cell’s evolutionary capacity, such as possible future evolutionary paths, seemingly unimportant proteins need to be mapped and studied. Finally, we generalize this research structure to be applicable to other systems of interest.
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14
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Carballar R, Martínez-Láinez JM, Samper B, Bru S, Bállega E, Mirallas O, Ricco N, Clotet J, Jiménez J. CDK-mediated Yku80 Phosphorylation Regulates the Balance Between Non-homologous End Joining (NHEJ) and Homologous Directed Recombination (HDR). J Mol Biol 2020; 432:166715. [PMID: 33217428 DOI: 10.1016/j.jmb.2020.11.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 11/04/2020] [Accepted: 11/11/2020] [Indexed: 11/28/2022]
Abstract
There are two major pathways for repairing DNA double-strand breaks (DSBs): homologous directed recombination (HDR) and non-homologous end-joining (NHEJ). While NHEJ functions throughout the cell cycle, HDR is only possible during S/G2 phases, suggesting that there are cell cycle-specific mechanisms regulating the balance between the two repair systems. The regulation exerted by CDKs on HDR has been extensively demonstrated, and here we present evidence that the CDK Pho85, in association with the G1 cyclin Pcl1, phosphorylates Yku80 on Ser 623 to regulate NHEJ activity. Cells bearing a non-phosphorylatable version of Yku80 show increased NHEJ and reduced HDR activity. Accordingly, yku80S623A cells present diminished viability upon treatment with the DSB-producer bleomycin, specifically in the G2 phase of the cell cycle. Interestingly, the mutation of the equivalent residue in human Ku80 increases sensitivity to bleomycin in several cancer cell lines, suggesting that this mechanism is conserved in humans. Altogether, our results reveal a new mechanism whereby G1-CDKs mediate the choice between HDR and NHEJ repair pathways, putting the error prone NHEJ on a leash and enabling error free HDR in G2 when homologous sequences are available.
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Affiliation(s)
- Reyes Carballar
- Basic Sciences Department, Faculty of Medicine and Health Sciences, Universitat Internacional de Catalunya, Barcelona, Spain
| | - Joan M Martínez-Láinez
- Basic Sciences Department, Faculty of Medicine and Health Sciences, Universitat Internacional de Catalunya, Barcelona, Spain
| | - Bàrbara Samper
- Basic Sciences Department, Faculty of Medicine and Health Sciences, Universitat Internacional de Catalunya, Barcelona, Spain
| | - Samuel Bru
- Basic Sciences Department, Faculty of Medicine and Health Sciences, Universitat Internacional de Catalunya, Barcelona, Spain
| | - Elisabet Bállega
- Basic Sciences Department, Faculty of Medicine and Health Sciences, Universitat Internacional de Catalunya, Barcelona, Spain
| | - Oriol Mirallas
- Basic Sciences Department, Faculty of Medicine and Health Sciences, Universitat Internacional de Catalunya, Barcelona, Spain
| | - Natalia Ricco
- Basic Sciences Department, Faculty of Medicine and Health Sciences, Universitat Internacional de Catalunya, Barcelona, Spain
| | - Josep Clotet
- Basic Sciences Department, Faculty of Medicine and Health Sciences, Universitat Internacional de Catalunya, Barcelona, Spain.
| | - Javier Jiménez
- Basic Sciences Department, Faculty of Medicine and Health Sciences, Universitat Internacional de Catalunya, Barcelona, Spain.
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15
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Crane MM, Tsuchiya M, Blue BW, Almazan JD, Chen KL, Duffy SR, Golubeva A, Grimm AM, Guard AM, Hill SA, Huynh E, Kelly RM, Kiflezghi M, Kim HD, Lee M, Lee TI, Li J, Nguyen BM, Whalen RM, Yeh FY, McCormick M, Kennedy BK, Delaney JR, Kaeberlein M. Rb analog Whi5 regulates G1 to S transition and cell size but not replicative lifespan in budding yeast. TRANSLATIONAL MEDICINE OF AGING 2019; 3:104-108. [PMID: 32190787 PMCID: PMC7080187 DOI: 10.1016/j.tma.2019.10.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
An increase in cell size with age is a characteristic feature of replicative aging in budding yeast. Deletion of the gene encoding Whi5 results in shortened duration of G1 and reduced cell size, and has been previously suggested to increase replicative lifespan. Upon careful analysis of multiple independently derived haploid and homozygous diploid whi5Δ mutants, we find no effect on lifespan, but we do confirm the reduction in cell size. We suggest that instead of antagonizing lifespan, the elongated G1 phase of the cell cycle during aging may actually play an important role in allowing aged cells time to repair accumulating DNA damage.
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Affiliation(s)
- Matthew M. Crane
- Department of Pathology, University of Washington, Seattle, WA, USA
| | | | - Ben W. Blue
- Department of Pathology, University of Washington, Seattle, WA, USA
| | - Jared D. Almazan
- Department of Pathology, University of Washington, Seattle, WA, USA
| | - Kenneth L. Chen
- Department of Pathology, University of Washington, Seattle, WA, USA
- Department of Genome Sciences, University of Washington, Seattle, Washington, USA
- Medical Scientist Training Program, University of Washington, Seattle, Washington USA
| | - Siobhan R. Duffy
- Department of Pathology, University of Washington, Seattle, WA, USA
| | | | - Annaiz M Grimm
- Department of Pathology, University of Washington, Seattle, WA, USA
| | - Alison M Guard
- Department of Pathology, University of Washington, Seattle, WA, USA
| | - Shauna A Hill
- Department of Pathology, University of Washington, Seattle, WA, USA
| | - Ellen Huynh
- Department of Pathology, University of Washington, Seattle, WA, USA
| | - Ryan M Kelly
- Department of Pathology, University of Washington, Seattle, WA, USA
| | | | - Hyunsung D. Kim
- Department of Pathology, University of Washington, Seattle, WA, USA
| | - Mitchell Lee
- Department of Pathology, University of Washington, Seattle, WA, USA
| | - Ting-I Lee
- Department of Pathology, University of Washington, Seattle, WA, USA
| | - Jiayi Li
- Department of Pathology, University of Washington, Seattle, WA, USA
| | - Bao M.G. Nguyen
- Department of Pathology, University of Washington, Seattle, WA, USA
| | - Riley M. Whalen
- Department of Pathology, University of Washington, Seattle, WA, USA
| | - Feng Y. Yeh
- Department of Pathology, University of Washington, Seattle, WA, USA
| | - Mark McCormick
- Department of Biochemistry and Molecular Biology, University of New Mexico, Albuquerque, NM, USA
| | | | - Joe R. Delaney
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC, USA
| | - Matt Kaeberlein
- Department of Pathology, University of Washington, Seattle, WA, USA
- Department of Genome Sciences, University of Washington, Seattle, Washington, USA
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16
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Moreno DF, Jenkins K, Morlot S, Charvin G, Csikasz-Nagy A, Aldea M. Proteostasis collapse, a hallmark of aging, hinders the chaperone-Start network and arrests cells in G1. eLife 2019; 8:48240. [PMID: 31518229 PMCID: PMC6744273 DOI: 10.7554/elife.48240] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Accepted: 09/05/2019] [Indexed: 12/26/2022] Open
Abstract
Loss of proteostasis and cellular senescence are key hallmarks of aging, but direct cause-effect relationships are not well understood. We show that most yeast cells arrest in G1 before death with low nuclear levels of Cln3, a key G1 cyclin extremely sensitive to chaperone status. Chaperone availability is seriously compromised in aged cells, and the G1 arrest coincides with massive aggregation of a metastable chaperone-activity reporter. Moreover, G1-cyclin overexpression increases lifespan in a chaperone-dependent manner. As a key prediction of a model integrating autocatalytic protein aggregation and a minimal Start network, enforced protein aggregation causes a severe reduction in lifespan, an effect that is greatly alleviated by increased expression of specific chaperones or cyclin Cln3. Overall, our data show that proteostasis breakdown, by compromising chaperone activity and G1-cyclin function, causes an irreversible arrest in G1, configuring a molecular pathway postulating proteostasis decay as a key contributing effector of cell senescence.
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Affiliation(s)
- David F Moreno
- Molecular Biology Institute of Barcelona (IBMB), CSIC, Barcelona, Spain
| | - Kirsten Jenkins
- Randall Division of Cell and Molecular Biophysics, King's College London, London, United Kingdom.,Institute of Mathematical and Molecular Biomedicine, King's College London, London, United Kingdom
| | - Sandrine Morlot
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Strasbourg, France.,Université de Strasbourg, Illkirch, France
| | - Gilles Charvin
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Strasbourg, France.,Université de Strasbourg, Illkirch, France
| | - Attila Csikasz-Nagy
- Randall Division of Cell and Molecular Biophysics, King's College London, London, United Kingdom.,Institute of Mathematical and Molecular Biomedicine, King's College London, London, United Kingdom.,Faculty of Information Technology and Bionics, Pázmány Péter Catholic University, Budapest, Hungary
| | - Martí Aldea
- Molecular Biology Institute of Barcelona (IBMB), CSIC, Barcelona, Spain.,Department of Basic Sciences, Universitat Internacional de Catalunya, Sant Cugat del Vallès, Spain
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17
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Pomraning KR, Collett JR, Kim J, Panisko EA, Culley DE, Dai Z, Deng S, Hofstad BA, Butcher MG, Magnuson JK. Transcriptomic analysis of the oleaginous yeast Lipomyces starkeyi during lipid accumulation on enzymatically treated corn stover hydrolysate. BIOTECHNOLOGY FOR BIOFUELS 2019; 12:162. [PMID: 31289462 PMCID: PMC6593508 DOI: 10.1186/s13068-019-1510-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2019] [Accepted: 06/19/2019] [Indexed: 05/24/2023]
Abstract
BACKGROUND Efficient and economically viable production of biofuels from lignocellulosic biomass is dependent on mechanical and chemical pretreatment and enzymatic hydrolysis of plant material. These processing steps yield simple sugars as well as plant-derived and process-added organic acids, sugar-derived dehydration products, aldehydes, phenolics and other compounds that inhibit the growth of many microorganisms. Lipomyces starkeyi is an oleaginous yeast capable of robust growth on a variety of sugars and lipid accumulation on pretreated lignocellulosic substrates making it attractive as an industrial producer of biofuels. Here, we examined gene expression during batch growth and lipid accumulation in a 20-L bioreactor with either a blend of pure glucose and xylose or pretreated corn stover (PCS) that had been enzymatically hydrolyzed as the carbon sources. RESULTS We monitored sugar and ammonium utilization as well as biomass accumulation and found that growth of L. starkeyi is inhibited with PCS hydrolysate as the carbon source. Both acetic acid and furfural are present at concentrations toxic to L. starkeyi in PCS hydrolysate. We quantified gene expression at seven time-points for each carbon source during batch growth and found that gene expression is similar at physiologically equivalent points. Analysis of promoter regions revealed that gene expression during the transition to lipid accumulation is regulated by carbon and nitrogen catabolite repression, regardless of carbon source and is associated with decreased expression of the translation machinery and suppression of the cell cycle. We identified 73 differentially expressed genes during growth phase in the bioreactor that may be involved in detoxification of corn stover hydrolysate. CONCLUSIONS Growth of L. starkeyi is inhibited by compounds present in PCS hydrolysate. Here, we monitored key metabolites to establish physiologically equivalent comparisons during a batch bioreactor run comparing PCS hydrolysate and purified sugars. L. starkeyi's response to PCS hydrolysate is primarily at the beginning of the run during growth phase when inhibitory compounds are presumably at their highest concentration and inducing the general detoxification response by L. starkeyi. Differentially expressed genes identified herein during growth phase will aid in the improvement of industrial strains capable of robust growth on substrates containing various growth inhibitory compounds.
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Affiliation(s)
| | | | - Joonhoon Kim
- Pacific Northwest National Laboratory, Richland, WA USA
- Joint BioEnergy Institute, Emeryville, CA USA
| | | | | | - Ziyu Dai
- Pacific Northwest National Laboratory, Richland, WA USA
| | - Shuang Deng
- Pacific Northwest National Laboratory, Richland, WA USA
| | | | | | - Jon K. Magnuson
- Pacific Northwest National Laboratory, Richland, WA USA
- Joint BioEnergy Institute, Emeryville, CA USA
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18
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Vall-Llaura N, Mir N, Garrido L, Vived C, Cabiscol E. Redox control of yeast Sir2 activity is involved in acetic acid resistance and longevity. Redox Biol 2019; 24:101229. [PMID: 31153040 PMCID: PMC6543126 DOI: 10.1016/j.redox.2019.101229] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 05/10/2019] [Accepted: 05/19/2019] [Indexed: 01/07/2023] Open
Abstract
Yeast Sir2 is an NAD-dependent histone deacetylase related to oxidative stress and aging. In a previous study, we showed that Sir2 is regulated by S-glutathionylation of key cysteine residues located at the catalytic domain. Mutation of these residues results in strains with increased resistance to disulfide stress. In the present study, these mutant cells were highly resistant to acetic acid and had an increased chronological life span. Mutant cells had increased acetyl-CoA synthetase activity, which converts acetic acid generated by yeast metabolism to acetyl.CoA. This could explain the acetic acid resistance and lower levels of this toxic acid in the extracellular media during aging. Increased acetyl-CoA levels would raise lipid droplets, a source of energy during aging, and fuel glyoxylate-dependent gluconeogenesis. The key enzyme of this pathway, phosphoenolpyruvate carboxykinase (Pck1), showed increased activity in these Sir2 mutant cells during aging. Sir2 activity decreased when cells shifted to the diauxic phase in the mutant strains, compared to the WT strain. Since Pck1 is inactivated through Sir2-dependent deacetylation, the decline in Sir2 activity explained the rise in Pck1 activity. As a consequence, storage of sugars such as trehalose would increase. We conclude that extended longevity observed in the mutants was a combination of increased lipid droplets and trehalose, and decreased acetic acid in the extracellular media. These results offer a deeper understanding of the redox regulation of Sir2 in acetic acid resistance, which is relevant in some food and industrial biotechnology and also in the metabolism associated to calorie restriction, aging and pathologies such as diabetes.
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Affiliation(s)
- Núria Vall-Llaura
- Department de Ciències Mèdiques Bàsiques, IRBLleida, Universitat de Lleida, Catalonia, Spain.
| | - Noèlia Mir
- Department de Ciències Mèdiques Bàsiques, IRBLleida, Universitat de Lleida, Catalonia, Spain.
| | - Lourdes Garrido
- Department de Ciències Mèdiques Bàsiques, IRBLleida, Universitat de Lleida, Catalonia, Spain.
| | - Celia Vived
- Department de Ciències Mèdiques Bàsiques, IRBLleida, Universitat de Lleida, Catalonia, Spain.
| | - Elisa Cabiscol
- Department de Ciències Mèdiques Bàsiques, IRBLleida, Universitat de Lleida, Catalonia, Spain.
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19
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Moreno DF, Parisi E, Yahya G, Vaggi F, Csikász-Nagy A, Aldea M. Competition in the chaperone-client network subordinates cell-cycle entry to growth and stress. Life Sci Alliance 2019; 2:2/2/e201800277. [PMID: 30988162 PMCID: PMC6467244 DOI: 10.26508/lsa.201800277] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Revised: 04/08/2019] [Accepted: 04/08/2019] [Indexed: 12/22/2022] Open
Abstract
The precise coordination of growth and proliferation has a universal prevalence in cell homeostasis. As a prominent property, cell size is modulated by the coordination between these processes in bacterial, yeast, and mammalian cells, but the underlying molecular mechanisms are largely unknown. Here, we show that multifunctional chaperone systems play a concerted and limiting role in cell-cycle entry, specifically driving nuclear accumulation of the G1 Cdk-cyclin complex. Based on these findings, we establish and test a molecular competition model that recapitulates cell-cycle-entry dependence on growth rate. As key predictions at a single-cell level, we show that availability of the Ydj1 chaperone and nuclear accumulation of the G1 cyclin Cln3 are inversely dependent on growth rate and readily respond to changes in protein synthesis and stress conditions that alter protein folding requirements. Thus, chaperone workload would subordinate Start to the biosynthetic machinery and dynamically adjust proliferation to the growth potential of the cell.
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Affiliation(s)
- David F Moreno
- Molecular Biology Institute of Barcelona, CSIC, Catalonia, Spain
| | - Eva Parisi
- Molecular Biology Institute of Barcelona, CSIC, Catalonia, Spain
| | - Galal Yahya
- Molecular Biology Institute of Barcelona, CSIC, Catalonia, Spain.,Department of Microbiology and Immunology, Zagazig University, Zagazig, Egypt
| | - Federico Vaggi
- Department of Informatics, Ecole Normale Supérieure, INRIA, Sierra Team, Paris, France
| | - Attila Csikász-Nagy
- Randall Centre for Cell and Molecular Biophysics and Institute of Mathematical and Molecular Biomedicine, King's College London, London, UK .,Pázmány Péter Catholic University, Faculty of Information Technology and Bionics, Budapest, Hungary
| | - Martí Aldea
- Molecular Biology Institute of Barcelona, CSIC, Catalonia, Spain .,Department of Basic Sciences, Universitat Internacional de Catalunya, Sant Cugat del Vallès, Spain
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20
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Quilis I, Taberner FJ, Martínez-Garay CA, Alepuz P, Igual JC. Karyopherin Msn5 is involved in a novel mechanism controlling the cellular level of cell cycle regulators Cln2 and Swi5. Cell Cycle 2019; 18:580-595. [PMID: 30739521 PMCID: PMC6464581 DOI: 10.1080/15384101.2019.1578148] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
The yeast β-karyopherin Msn5 controls the SBF cell-cycle transcription factor, responsible for the periodic expression of CLN2 cyclin gene at G1/S, and the nuclear export of Cln2 protein. Here we show that Msn5 regulates Cln2 by an additional mechanism. Inactivation of Msn5 causes a severe reduction in the cellular content of Cln2. This occurs by a post-transcriptional mechanism, since CLN2 mRNA level is not importantly affected in asynchronous cultures. Cln2 stability is not significantly altered in msn5 cells and inactivation of Msn5 causes a reduction in protein level even when Cln2 is stabilized. Therefore, the reduced amount of Cln2 in msn5 cells is mainly due not to a higher rate of protein degradation but to a defect in Cln2 synthesis. In fact, analysis of polysome profiles indicated that Msn5 inactivation causes a shift of CLN2 and SWI5 mRNAs from heavy-polysomal to light-polysomal and non-polysomal fractions, supporting a defect in Cln2 and Swi5 protein synthesis in the msn5 mutant. The analysis of truncated versions of Cln2 and of chimeric cyclins combining distinct domains from Cln2 and the related Cln1 cyclin identified an internal region in Cln2 from 181 to 225 residues that when fused to GFP is able to confer Msn5-dependent regulation of protein cellular content. Finally, we showed that a high level of Cln2 is toxic in the absence of Msn5. In summary, we described that Msn5 is required for the proper protein synthesis of specific proteins, introducing a new level of control of cell cycle regulators.
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Affiliation(s)
- Inma Quilis
- a Departament de Bioquímica i Biologia Molecular , Universitat de València , Valencia , Spain.,b Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BIOTECMED) , Universitat de València , Valencia , Spain
| | - Francisco J Taberner
- a Departament de Bioquímica i Biologia Molecular , Universitat de València , Valencia , Spain.,b Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BIOTECMED) , Universitat de València , Valencia , Spain
| | - Carlos A Martínez-Garay
- a Departament de Bioquímica i Biologia Molecular , Universitat de València , Valencia , Spain.,b Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BIOTECMED) , Universitat de València , Valencia , Spain
| | - Paula Alepuz
- a Departament de Bioquímica i Biologia Molecular , Universitat de València , Valencia , Spain.,b Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BIOTECMED) , Universitat de València , Valencia , Spain
| | - J Carlos Igual
- a Departament de Bioquímica i Biologia Molecular , Universitat de València , Valencia , Spain.,b Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BIOTECMED) , Universitat de València , Valencia , Spain
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21
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Martínez-Láinez JM, Moreno DF, Parisi E, Clotet J, Aldea M. Centromeric signaling proteins boost G1 cyclin degradation and modulate cell size in budding yeast. PLoS Biol 2018; 16:e2005388. [PMID: 30080861 PMCID: PMC6095599 DOI: 10.1371/journal.pbio.2005388] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Revised: 08/16/2018] [Accepted: 07/20/2018] [Indexed: 11/18/2022] Open
Abstract
Cell size scales with ploidy in a great range of eukaryotes, but the underlying mechanisms remain unknown. Using various orthogonal single-cell approaches, we show that cell size increases linearly with centromere (CEN) copy number in budding yeast. This effect is due to a G1 delay mediated by increased degradation of Cln3, the most upstream G1 cyclin acting at Start, and specific centromeric signaling proteins, namely Mad3 and Bub3. Mad3 binds both Cln3 and Cdc4, the adaptor component of the Skp1/Cul1/F-box (SCF) complex that targets Cln3 for degradation, these interactions being essential for the CEN-dosage dependent effects on cell size. Our results reveal a pathway that modulates cell size as a function of CEN number, and we speculate that, in cooperation with other CEN-independent mechanisms, it could assist the cell to attain efficient mass/ploidy ratios.
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Affiliation(s)
- Joan M. Martínez-Láinez
- Institut de Biologia Molecular de Barcelona IBMB-CSIC, Barcelona, Catalonia, Spain
- Departament de Ciències Bàsiques, Universitat Internacional de Catalunya, Barcelona, Spain
| | - David F. Moreno
- Institut de Biologia Molecular de Barcelona IBMB-CSIC, Barcelona, Catalonia, Spain
| | - Eva Parisi
- Institut de Biologia Molecular de Barcelona IBMB-CSIC, Barcelona, Catalonia, Spain
| | - Josep Clotet
- Departament de Ciències Bàsiques, Universitat Internacional de Catalunya, Barcelona, Spain
| | - Martí Aldea
- Institut de Biologia Molecular de Barcelona IBMB-CSIC, Barcelona, Catalonia, Spain
- Departament de Ciències Bàsiques, Universitat Internacional de Catalunya, Barcelona, Spain
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22
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Parisi E, Yahya G, Flores A, Aldea M. Cdc48/p97 segregase is modulated by cyclin-dependent kinase to determine cyclin fate during G1 progression. EMBO J 2018; 37:embj.201798724. [PMID: 29950310 DOI: 10.15252/embj.201798724] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Revised: 05/14/2018] [Accepted: 06/12/2018] [Indexed: 01/26/2023] Open
Abstract
Cells sense myriad signals during G1, and a rapid response to prevent cell cycle entry is of crucial importance for proper development and adaptation. Cln3, the most upstream G1 cyclin in budding yeast, is an extremely short-lived protein subject to ubiquitination and proteasomal degradation. On the other hand, nuclear accumulation of Cln3 depends on chaperones that are also important for its degradation. However, how these processes are intertwined to control G1-cyclin fate is not well understood. Here, we show that Cln3 undergoes a challenging ubiquitination step required for both degradation and full activation. Segregase Cdc48/p97 prevents degradation of ubiquitinated Cln3, and concurrently stimulates its ER release and nuclear accumulation to trigger Start. Cdc48/p97 phosphorylation at conserved Cdk-target sites is important for recruitment of specific cofactors and, in both yeast and mammalian cells, to attain proper G1-cyclin levels and activity. Cdk-dependent modulation of Cdc48 would subjugate G1 cyclins to fast and reversible state switching, thus arresting cells promptly in G1 at developmental or environmental checkpoints, but also resuming G1 progression immediately after proliferative signals reappear.
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Affiliation(s)
- Eva Parisi
- Molecular Biology Institute of Barcelona IBMB-CSIC, Barcelona, Catalonia, Spain
| | - Galal Yahya
- Molecular Biology Institute of Barcelona IBMB-CSIC, Barcelona, Catalonia, Spain.,Department of Microbiology and Immunology, School of Pharmacy, Zagazig University, Zagazig, Egypt
| | - Alba Flores
- Molecular Biology Institute of Barcelona IBMB-CSIC, Barcelona, Catalonia, Spain
| | - Martí Aldea
- Molecular Biology Institute of Barcelona IBMB-CSIC, Barcelona, Catalonia, Spain .,Departament de Ciències Bàsiques, Universitat Internacional de Catalunya, Barcelona, Catalonia, Spain
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23
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Talarek N, Gueydon E, Schwob E. Homeostatic control of START through negative feedback between Cln3-Cdk1 and Rim15/Greatwall kinase in budding yeast. eLife 2017; 6. [PMID: 28600888 PMCID: PMC5484617 DOI: 10.7554/elife.26233] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Accepted: 06/10/2017] [Indexed: 12/30/2022] Open
Abstract
How cells coordinate growth and division is key for size homeostasis. Phosphorylation by G1-CDK of Whi5/Rb inhibitors of SBF/E2F transcription factors triggers irreversible S-phase entry in yeast and metazoans, but why this occurs at a given cell size is not fully understood. We show that the yeast Rim15-Igo1,2 pathway, orthologous to Gwl-Arpp19/ENSA, is up-regulated in early G1 and helps promoting START by preventing PP2ACdc55 to dephosphorylate Whi5. RIM15 overexpression lowers cell size while IGO1,2 deletion delays START in cells with low CDK activity. Deletion of WHI5, CDC55 and ectopic CLN2 expression suppress the START delay of igo1,2∆ cells. Rim15 activity increases after cells switch from fermentation to respiration, where Igo1,2 contribute to chromosome maintenance. Interestingly Cln3-Cdk1 also inhibits Rim15 activity, which enables homeostatic control of Whi5 phosphorylation and cell cycle entry. We propose that Rim15/Gwl regulation of PP2A plays a hitherto unappreciated role in cell size homeostasis during metabolic rewiring of the cell cycle. DOI:http://dx.doi.org/10.7554/eLife.26233.001
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Affiliation(s)
| | | | - Etienne Schwob
- IGMM, CNRS, University of Montpellier, Montpellier, France
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24
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Aldea M, Jenkins K, Csikász-Nagy A. Growth Rate as a Direct Regulator of the Start Network to Set Cell Size. Front Cell Dev Biol 2017; 5:57. [PMID: 28603712 PMCID: PMC5445111 DOI: 10.3389/fcell.2017.00057] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Accepted: 05/11/2017] [Indexed: 11/13/2022] Open
Abstract
Cells are able to adjust their growth and size to external inputs to comply with specific fates and developmental programs. Molecular pathways controlling growth also have an enormous impact in cell size, and bacteria, yeast, or epithelial cells modify their size as a function of growth rate. This universal feature suggests that growth (mass) and proliferation (cell number) rates are subject to general coordinating mechanisms. However, the underlying molecular connections are still a matter of debate. Here we review the current ideas on growth and cell size control, and focus on the possible mechanisms that could link the biosynthetic machinery to the Start network in budding yeast. In particular, we discuss the role of molecular chaperones in a competition framework to explain cell size control by growth at the individual cell level.
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Affiliation(s)
- Martí Aldea
- Molecular Biology Institute of Barcelona, Consejo Superior de Investigaciones CientíficasBarcelona, Spain.,Departament de Ciències Bàsiques, Universitat Internacional de CatalunyaBarcelona, Spain
| | - Kirsten Jenkins
- Randall Division of Cell and Molecular Biophysics and Institute of Mathematical and Molecular Biomedicine, King's College LondonLondon, United Kingdom
| | - Attila Csikász-Nagy
- Randall Division of Cell and Molecular Biophysics and Institute of Mathematical and Molecular Biomedicine, King's College LondonLondon, United Kingdom.,Faculty of Information Technology and Bionics, Pázmány Péter Catholic UniversityBudapest, Hungary
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25
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Ren P, Malik A, Zeng F. Identification of YPL014W (Cip1) as a novel negative regulator of cyclin-dependent kinase in Saccharomyces cerevisiae. Genes Cells 2016; 21:543-52. [PMID: 27005485 DOI: 10.1111/gtc.12361] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Accepted: 02/22/2016] [Indexed: 02/06/2023]
Abstract
Cyclin-dependent kinases drive cell division cycle progression in eukaryotic cells. In the model eukaryotic organism Saccharomyces cerevisiae (budding yeast), a single cyclin-dependent kinase, Cdk1, is essential and sufficient to drive the cell cycle. Misregulated CDK activity induces unscheduled proliferation as well as genomic instability, which are hallmarks of the cancer. Here, we report a novel Cdk1-interacting protein, YPL014W, which we name Cip1 (for Cdk1-interacting protein 1). Our results show that Cip1 specifically interacts with G1 /S-phase Cln2-Cdk1 complex but not with S-phase Clb5-Cdk1 or M-phase Clb2-Cdk1 complexes. Also Cip1 phosphorylation is cell cycle regulated in a S-phase Cdk1-dependent manner. Over-expression of Cip1 blocks cell cycle progression in G1 and stabilizes the S-phase Cdk1 inhibitor Sic1 in vivo. In addition, disruption of CIP1 (cip1Δ) leads to faster G1 /S-phase transition compared to wild-type cells. Moreover, Cip1 inhibits Cln2-CDK activity both in vivo and in vitro. Our finding proves Cip1 as a novel negative regulator of cyclin-dependent kinase in S. cerevisiae.
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Affiliation(s)
- Ping Ren
- Department of Biochemistry and Molecular Biology, Biophysics Unit, School of Medicine, Universitat Autonoma de Barcelona, 08193, Bellaterra, Catalonia, Spain
| | - Asrar Malik
- Department of Biochemistry and Molecular Biology, Biophysics Unit, School of Medicine, Universitat Autonoma de Barcelona, 08193, Bellaterra, Catalonia, Spain
| | - Fanli Zeng
- Department of Biochemistry and Molecular Biology, Biophysics Unit, School of Medicine, Universitat Autonoma de Barcelona, 08193, Bellaterra, Catalonia, Spain
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26
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Tamayo E, Benabdellah K, Ferrol N. Characterization of Three New Glutaredoxin Genes in the Arbuscular Mycorrhizal Fungus Rhizophagus irregularis: Putative Role of RiGRX4 and RiGRX5 in Iron Homeostasis. PLoS One 2016; 11:e0149606. [PMID: 26900849 PMCID: PMC4765768 DOI: 10.1371/journal.pone.0149606] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Accepted: 02/02/2016] [Indexed: 01/07/2023] Open
Abstract
Glutaredoxins (GRXs) are small ubiquitous oxidoreductases involved in the regulation of the redox state in living cells. In an attempt to identify the full complement of GRXs in the arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis, three additional GRX homologs, besides the formerly characterized GintGRX1 (renamed here as RiGRX1), were identified. The three new GRXs (RiGRX4, RiGRX5 and RiGRX6) contain the CXXS domain of monothiol GRXs, but whereas RiGRX4 and RiGRX5 belong to class II GRXs, RiGRX6 belongs to class I together with RiGRX1. By using a yeast expression system, we observed that the newly identified homologs partially reverted sensitivity of the GRX deletion yeast strains to external oxidants. Furthermore, our results indicated that RiGRX4 and RiGRX5 play a role in iron homeostasis in yeast. Gene expression analyses revealed that RiGRX1 and RiGRX6 were more highly expressed in the intraradical (IRM) than in the extraradical mycelium (ERM). Exposure of the ERM to hydrogen peroxide induced up-regulation of RiGRX1, RiGRX4 and RiGRX5 gene expression. RiGRX4 expression was also up-regulated in the ERM when the fungus was grown in media supplemented with a high iron concentration. These data indicate the two monothiol class II GRXs, RiGRX4 and RiGRX5, might be involved in oxidative stress protection and in the regulation of fungal iron homeostasis. Increased expression of RiGRX1 and RiGRX6 in the IRM suggests that these GRXs should play a key role in oxidative stress protection of R. irregularis during its in planta phase.
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Affiliation(s)
- Elisabeth Tamayo
- Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Karim Benabdellah
- Genomic Medicine Department, GENYO, Centre for Genomics and Oncological Research, Pfizer-University of Granada-Andalusian Regional Government, Parque Tecnológico Ciencias de la Salud, Granada, Spain
| | - Nuria Ferrol
- Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
- * E-mail:
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27
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Georgieva MV, Yahya G, Codó L, Ortiz R, Teixidó L, Claros J, Jara R, Jara M, Iborra A, Gelpí JL, Gallego C, Orozco M, Aldea M. Inntags: small self-structured epitopes for innocuous protein tagging. Nat Methods 2015; 12:955-8. [PMID: 26322837 DOI: 10.1038/nmeth.3556] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 07/06/2015] [Indexed: 11/09/2022]
Abstract
Protein tagging is widely used in approaches ranging from affinity purification to fluorescence-based detection in live cells. However, an intrinsic limitation of tagging is that the native function of the protein may be compromised or even abolished by the presence of the tag. Here we describe and characterize a set of small, innocuous protein tags (inntags) that we anticipate will find application in a variety of biological techniques.
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Affiliation(s)
- Maya V Georgieva
- Molecular Biology Institute of Barcelona (IBMB), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain
| | - Galal Yahya
- Molecular Biology Institute of Barcelona (IBMB), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain.,Department of Microbiology and Immunology, School of Pharmacy, Zagazig University, Zagazig, Egypt
| | - Laia Codó
- Barcelona Supercomputing Center (BSC), Barcelona, Spain.,Joint BSC-CRG-IRB Programme in Computational Biology, Barcelona, Spain
| | - Raúl Ortiz
- Molecular Biology Institute of Barcelona (IBMB), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain
| | | | | | | | | | | | - Josep Lluís Gelpí
- Barcelona Supercomputing Center (BSC), Barcelona, Spain.,Joint BSC-CRG-IRB Programme in Computational Biology, Barcelona, Spain.,Departament de Bioquimica, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain
| | - Carme Gallego
- Molecular Biology Institute of Barcelona (IBMB), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain
| | - Modesto Orozco
- Joint BSC-CRG-IRB Programme in Computational Biology, Barcelona, Spain.,Departament de Bioquimica, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain.,Institute for Research in Biomedicine (IRB Barcelona), Barcelona, Spain
| | - Martí Aldea
- Molecular Biology Institute of Barcelona (IBMB), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain
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28
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Sundaram V, Petkova MI, Pujol-Carrion N, Boada J, de la Torre-Ruiz MA. Tor1, Sch9 and PKA downregulation in quiescence rely on Mtl1 to preserve mitochondrial integrity and cell survival. Mol Microbiol 2015; 97:93-109. [DOI: 10.1111/mmi.13013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/30/2015] [Indexed: 12/12/2022]
Affiliation(s)
- Venkatraghavan Sundaram
- Department of Basic Medical Sciences; IRB-Lleida; University of Lleida; Av. Alcalde Rovira Roure n° 80 25198 Lleida Spain
| | - Mima I. Petkova
- Department of Basic Medical Sciences; IRB-Lleida; University of Lleida; Av. Alcalde Rovira Roure n° 80 25198 Lleida Spain
| | - Nuria Pujol-Carrion
- Department of Basic Medical Sciences; IRB-Lleida; University of Lleida; Av. Alcalde Rovira Roure n° 80 25198 Lleida Spain
| | - Jordi Boada
- Department of Experimental Medicine; IRB-Lleida; University of Lleida; Av. Alcalde Rovira Roure n° 80 25198 Lleida Spain
| | - Maria Angeles de la Torre-Ruiz
- Department of Basic Medical Sciences; IRB-Lleida; University of Lleida; Av. Alcalde Rovira Roure n° 80 25198 Lleida Spain
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29
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Spiesser TW, Kühn C, Krantz M, Klipp E. Bud-Localization of CLB2 mRNA Can Constitute a Growth Rate Dependent Daughter Sizer. PLoS Comput Biol 2015; 11:e1004223. [PMID: 25910075 PMCID: PMC4429581 DOI: 10.1371/journal.pcbi.1004223] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Accepted: 03/03/2015] [Indexed: 11/19/2022] Open
Abstract
Maintenance of cellular size is a fundamental systems level process that requires balancing of cell growth with proliferation. This is achieved via the cell division cycle, which is driven by the sequential accumulation and destruction of cyclins. The regulatory network around these cyclins, particularly in G1, has been interpreted as a size control network in budding yeast, and cell size as being decisive for the START transition. However, it is not clear why disruptions in the G1 network may lead to altered size rather than loss of size control, or why the S-G2-M duration also depends on nutrients. With a mathematical population model comprised of individually growing cells, we show that cyclin translation would suffice to explain the observed growth rate dependence of cell volume at START. Moreover, we assess the impact of the observed bud-localisation of the G2 cyclin CLB2 mRNA, and find that localised cyclin translation could provide an efficient mechanism for measuring the biosynthetic capacity in specific compartments: The mother in G1, and the growing bud in G2. Hence, iteration of the same principle can ensure that the mother cell is strong enough to grow a bud, and that the bud is strong enough for independent life. Cell sizes emerge in the model, which predicts that a single CDK-cyclin pair per growth phase suffices for size control in budding yeast, despite the necessity of the cell cycle network around the cyclins to integrate other cues. Size control seems to be exerted twice, where the G2/M control affects bud size through bud-localized translation of CLB2 mRNA, explaining the dependence of the S-G2-M duration on nutrients. Taken together, our findings suggest that cell size is an emergent rather than a regulatory property of the network linking growth and proliferation.
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Affiliation(s)
- Thomas W. Spiesser
- Theoretical Biophysics, Humboldt-Universität zu Berlin, Berlin, Germany
- * E-mail: (TWS); (EK)
| | - Clemens Kühn
- Theoretical Biophysics, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Marcus Krantz
- Theoretical Biophysics, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Edda Klipp
- Theoretical Biophysics, Humboldt-Universität zu Berlin, Berlin, Germany
- * E-mail: (TWS); (EK)
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30
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Polymenis M, Aramayo R. Translate to divide: сontrol of the cell cycle by protein synthesis. MICROBIAL CELL 2015; 2:94-104. [PMID: 28357283 PMCID: PMC5348972 DOI: 10.15698/mic2015.04.198] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Protein synthesis underpins much of cell growth and, consequently, cell multiplication. Understanding how proliferating cells commit and progress into the cell cycle requires knowing not only which proteins need to be synthesized, but also what determines their rate of synthesis during cell division.
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Affiliation(s)
- Michael Polymenis
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA
| | - Rodolfo Aramayo
- Department of Biology, Texas A&M University, College Station, TX 77843, USA
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31
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Jiménez J, Bru S, Ribeiro M, Clotet J. Live fast, die soon: cell cycle progression and lifespan in yeast cells. MICROBIAL CELL 2015; 2:62-67. [PMID: 28357278 PMCID: PMC5349179 DOI: 10.15698/mic2015.03.191] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Our understanding of lifespan has benefited enormously from the study of a simple model, the yeast Saccharomyces cerevisiae. Although a unicellular organism, yeasts undergo many of the processes directly related with aging that to some extent are conserved in mammalian cells. Nutrient-limiting conditions have been involved in lifespan extension, especially in the case of caloric restriction, which also has a direct impact on cell cycle progression. In fact, other environmental stresses (osmotic, oxidative) that interfere with normal cell cycle progression also influence the lifespan of cells, indicating a relationship between lifespan and cell cycle control. In the present review we compile and discuss new findings related to how cell cycle progression is regulated by other nutrients. We centred this review on the analysis of phosphate, also give some attention to nitrogen, and the impact of these nutrients on lifespan.
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Affiliation(s)
- Javier Jiménez
- Dept. Ciències Bàsiques, Facultat de Medicina i Ciències de la Salut. Universitat Internacional de Catalunya, Barcelona, Catalonia, Spain
| | - Samuel Bru
- Dept. Ciències Bàsiques, Facultat de Medicina i Ciències de la Salut. Universitat Internacional de Catalunya, Barcelona, Catalonia, Spain
| | - Mariana Ribeiro
- Dept. Ciències Bàsiques, Facultat de Medicina i Ciències de la Salut. Universitat Internacional de Catalunya, Barcelona, Catalonia, Spain
| | - Josep Clotet
- Dept. Ciències Bàsiques, Facultat de Medicina i Ciències de la Salut. Universitat Internacional de Catalunya, Barcelona, Catalonia, Spain
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32
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Liu X, Wang X, Yang X, Liu S, Jiang L, Qu Y, Hu L, Ouyang Q, Tang C. Reliable cell cycle commitment in budding yeast is ensured by signal integration. eLife 2015; 4. [PMID: 25590650 PMCID: PMC4378612 DOI: 10.7554/elife.03977] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Accepted: 01/07/2015] [Indexed: 12/29/2022] Open
Abstract
Cell fate decisions are critical for life, yet little is known about how their
reliability is achieved when signals are noisy and fluctuating with time. In this
study, we show that in budding yeast, the decision of cell cycle commitment (Start)
is determined by the time integration of its triggering signal Cln3. We further
identify the Start repressor, Whi5, as the integrator. The instantaneous kinase
activity of Cln3-Cdk1 is recorded over time on the phosphorylated Whi5, and the
decision is made only when phosphorylated Whi5 reaches a threshold. Cells adjust the
threshold by modulating Whi5 concentration in different nutrient conditions to
coordinate growth and division. Our work shows that the strategy of signal
integration, which was previously found in decision-making behaviors of animals, is
adopted at the cellular level to reduce noise and minimize uncertainty. DOI:http://dx.doi.org/10.7554/eLife.03977.001 Budding yeast and other single-celled organisms can reproduce by dividing to produce
two daughter cells. The timing of the cell division is critical because if the cell
is still small when it divides, the resulting daughter cells may not be big enough to
survive. In budding yeast, the irreversible decision to divide—known as the
‘Start’ checkpoint—is only made once a cell reaches a certain
size and is triggered by a protein called Cln3. This protein controls the activity of
another protein called Whi5, which normally prevents the cell from dividing by
switching off particular genes. Cln3 adds phosphate groups to Whi5 to make
‘phosphorylated Whi5’, which allows the genes involved in cell division
to be switched on. It is commonly believed that the level of Cln3 reflects the size of the cell and the
nutrient conditions. Therefore, one model of cell division proposes that the cell
passes the Start checkpoint when the level of Cln3 reaches a threshold value.
However, levels of the Cln3 protein in cells can naturally fluctuate, and computer
simulations based on this model showed that this would not produce reliable decisions
on when to divide. So how do cells manage to distinguish noise from the genuine
signals that indicate it is the right time to divide? To address this question, Liu et al. studied yeast cells containing an artificial
version of the gene encoding the Cln3 protein whose levels could be adjusted by
adding a particular chemical. This revealed that cells with higher levels of Cln3
passed through the Start checkpoint sooner than cells that had lower levels of
Cln3. The observation suggests that cells add up the amount of Cln3 present over a period
of time to see if this reaches the threshold needed for the Start checkpoint. This
could be possible if, instead of sensing Cln3 levels directly, the cell senses the
accumulation of phosphorylated Whi5. To test this idea, Liu et al. carried out
additional experiments and found that the decision to pass the Start checkpoint only
occurs when the amount of phosphorylated Whi5 reaches a certain threshold. The cells are able to coordinate their growth and division under different nutrient
conditions by altering the threshold of phosphorylated Whi5. When the nutrient supply
is poor, more phosphorylated Whi5 needs to be accumulated to allow the cell to pass
the Start checkpoint. In this way, cells adjust when they divide according to
nutrient conditions. Similar strategies may be found in other signaling or
decision-making systems. DOI:http://dx.doi.org/10.7554/eLife.03977.002
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Affiliation(s)
- Xili Liu
- Center for Quantitative Biology, Peking University, Beijing, China
| | - Xin Wang
- Center for Quantitative Biology, Peking University, Beijing, China
| | - Xiaojing Yang
- Center for Quantitative Biology, Peking University, Beijing, China
| | - Sen Liu
- Institute of Molecular Biology, College of Medical Science, China Three Gorges University, Yichang, China
| | - Lingli Jiang
- Center for Quantitative Biology, Peking University, Beijing, China
| | - Yimiao Qu
- Center for Quantitative Biology, Peking University, Beijing, China
| | - Lufeng Hu
- Center for Quantitative Biology, Peking University, Beijing, China
| | - Qi Ouyang
- Center for Quantitative Biology, Peking University, Beijing, China
| | - Chao Tang
- Center for Quantitative Biology, Peking University, Beijing, China
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33
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Wannige CT, Kulasiri D, Samarasinghe S. The meiotic-mitotic initiation switch in budding yeast maintains its function robustly against sensitive parameter perturbations. Biosystems 2014; 124:61-74. [PMID: 25195149 DOI: 10.1016/j.biosystems.2014.09.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Revised: 09/01/2014] [Accepted: 09/02/2014] [Indexed: 11/30/2022]
Abstract
Experiments show that the meiotic-mitotic initiation switch in budding yeast functions robustly during the early hours of meiosis initiation. In this study, we explain these experimental observations first by understanding how this switching occurs during the early hours of meiosis by studying the temporal variation of this switch at the gene expression level. Then, we investigate the effects on this meiotic-mitotic switching from the perturbations of the most sensitive parameters in budding yeast meiosis initiation network. We use a mathematical model of meiosis initiation in budding yeast for this task and find the most sensitive group of parameters that influence the expressions of meiosis and mitosis initiators at all stages of the meiotic-mitotic switch. The results indicate that the transition region of the switch, where a double negative feedback loop between meiosis (Ime2) and mitosis (Cdk1/Cln3) initiators plays a major role, shows lower robustness. Feedback loops are frequently observed serving as a major robust adaption mechanism in many biological networks. Consequences of this less robust region appear in the transition region of the resulting switches. Most importantly, despite the differences observed in the transition region, we find that the meiotic-mitotic switch robustly maintains its main function of transition from meiosis to mitosis when the nutrients are re-supplied, against the perturbations in the sensitive parameters.
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Affiliation(s)
- C T Wannige
- Centre for Advanced Computational Solutions (C-fACS), Department of Molecular Biosciences, Lincoln University, Christchurch, New Zealand
| | - D Kulasiri
- Centre for Advanced Computational Solutions (C-fACS), Department of Molecular Biosciences, Lincoln University, Christchurch, New Zealand.
| | - S Samarasinghe
- Centre for Advanced Computational Solutions (C-fACS), Department of Molecular Biosciences, Lincoln University, Christchurch, New Zealand
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34
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Willhite DG, Brigati JR, Selcer KE, Denny JE, Duck ZA, Wright SE. Pheromone responsiveness is regulated by components of the Gpr1p-mediated glucose sensing pathway inSaccharomyces cerevisiae. Yeast 2014; 31:361-74. [DOI: 10.1002/yea.3030] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Revised: 06/24/2014] [Accepted: 07/03/2014] [Indexed: 11/10/2022] Open
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35
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Wannige CT, Kulasiri D, Samarasinghe S. A nutrient dependant switch explains mutually exclusive existence of meiosis and mitosis initiation in budding yeast. J Theor Biol 2014; 341:88-101. [PMID: 24099720 DOI: 10.1016/j.jtbi.2013.09.030] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Accepted: 09/20/2013] [Indexed: 10/26/2022]
Abstract
Nutrients from living environment are vital for the survival and growth of any organism. Budding yeast diploid cells decide to grow by mitosis type cell division or decide to create unique, stress resistant spores by meiosis type cell division depending on the available nutrient conditions. To gain a molecular systems level understanding of the nutrient dependant switching between meiosis and mitosis initiation in diploid cells of budding yeast, we develop a theoretical model based on ordinary differential equations (ODEs) including the mitosis initiator and its relations to budding yeast meiosis initiation network. Our model accurately and qualitatively predicts the experimentally revealed temporal variations of related proteins under different nutrient conditions as well as the diverse mutant studies related to meiosis and mitosis initiation. Using this model, we show how the meiosis and mitosis initiators form an all-or-none type bistable switch in response to available nutrient level (mainly nitrogen). The transitions to and from meiosis or mitosis initiation states occur via saddle node bifurcation. This bidirectional switch helps the optimal usage of available nutrients and explains the mutually exclusive existence of meiosis and mitosis pathways.
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Affiliation(s)
- C T Wannige
- Centre for Advanced Computational Solutions (C-fACS), Department of Molecular Biosciences, Lincoln University, Christchurch, New Zealand
| | - D Kulasiri
- Centre for Advanced Computational Solutions (C-fACS), Department of Molecular Biosciences, Lincoln University, Christchurch, New Zealand.
| | - S Samarasinghe
- Centre for Advanced Computational Solutions (C-fACS), Department of Molecular Biosciences, Lincoln University, Christchurch, New Zealand
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36
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Cai Y, Futcher B. Effects of the yeast RNA-binding protein Whi3 on the half-life and abundance of CLN3 mRNA and other targets. PLoS One 2013; 8:e84630. [PMID: 24386402 PMCID: PMC3875557 DOI: 10.1371/journal.pone.0084630] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Accepted: 11/15/2013] [Indexed: 11/20/2022] Open
Abstract
Whi3 is an RNA binding protein known to bind the mRNA of the yeast G1 cyclin gene CLN3. It inhibits CLN3 function, but the mechanism of this inhibition is unclear; in previous studies, Whi3 made no observable difference to CLN3 mRNA levels, translation, or protein abundance. Here, we re-approach this issue using microarrays, RNA-Seq, ribosome profiling, and other methods. By multiple methods, we find that the whi3 mutation causes a small but consistent increase in the abundance of hundreds of mRNAs, including the CLN3 mRNA. The effect on various mRNAs is roughly in proportion to the density of GCAU or UGCAU motifs carried by these mRNAs, which may be a binding site for Whi3. mRNA instability of Whi3 targets may in part depend on a 3′ AU rich element (ARE), AUUUUA. In addition, the whi3 mutation causes a small increase in the translational efficiency of CLN3 mRNA. The increase in CLN3 mRNA half-life and abundance together with the increase in translational efficiency is fully sufficient to explain the small-cell phenotype of whi3 mutants. Under stress conditions, Whi3 becomes a component of P-bodies or stress granules, but Whi3 also acts under non-stress condition, when no P-bodies are visible. We suggest that Whi3 may be a very broadly-acting, but mild, modulator of mRNA stability. In CLN3, Whi3 may bind to the 3′ GCAU motifs to attract the Ccr4-Not complex to promote RNA deadenylation and turnover, and Whi3 may bind to the 5′ GCAU motifs to inhibit translation.
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Affiliation(s)
- Ying Cai
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, United States of America
| | - Bruce Futcher
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, United States of America
- * E-mail:
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37
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Whi3, an S. cerevisiae RNA-binding protein, is a component of stress granules that regulates levels of its target mRNAs. PLoS One 2013; 8:e84060. [PMID: 24386330 PMCID: PMC3873981 DOI: 10.1371/journal.pone.0084060] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Accepted: 11/11/2013] [Indexed: 01/31/2023] Open
Abstract
RNA binding proteins (RBPs) are vital to the regulation of mRNA transcripts, and can alter mRNA localization, degradation, translation, and storage. Whi3 was originally identified in a screen for small cell size mutants, and has since been characterized as an RBP. The identification of Whi3-interacting mRNAs involved in mediating cellular responses to stress suggested that Whi3 might be involved in stress-responsive RNA processing. We show that Whi3 localizes to stress granules in response to glucose deprivation or heat shock. The kinetics and pattern of Whi3 localization in response to a range of temperatures were subtly but distinctly different from those of known components of RNA processing granules. Deletion of Whi3 resulted in an increase in the relative abundance of Whi3 target RNAs, either in the presence or absence of heat shock. Increased levels of the CLN3 mRNA in whi3Δ cells may explain their decreased cell size. Another mRNA target of Whi3 encodes the zinc-responsive transcription factor Zap1, suggesting a role for Whi3 in response to zinc stress. Indeed, we found that whi3Δ cells have enhanced sensitivity to zinc toxicity. Together our results suggest an expanded model for Whi3 function: in addition to its role as a regulator of the cell cycle, Whi3 may have a role in stress-dependent RNA processing and responses to a variety of stress conditions.
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38
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Yahya G, Parisi E, Flores A, Gallego C, Aldea M. A Whi7-anchored loop controls the G1 Cdk-cyclin complex at start. Mol Cell 2013; 53:115-26. [PMID: 24374311 DOI: 10.1016/j.molcel.2013.11.015] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Revised: 10/30/2013] [Accepted: 11/21/2013] [Indexed: 01/12/2023]
Abstract
Cells commit to a new cell cycle at Start by activation of the G1 Cdk-cyclin complex which, in turn, triggers a genome-wide transcriptional wave that executes the G1/S transition. In budding yeast, the Cdc28-Cln3 complex is regulated by an ER-retention mechanism that is important for proper cell size control. We have isolated small-cell-size CDC28 mutants showing impaired retention at the ER and premature accumulation of the Cln3 cyclin in the nucleus. The differential interactome of a quintuple Cdc28(wee) mutant pinpointed Whi7, a Whi5 paralog targeted by Cdc28 that associates to the ER in a phosphorylation-dependent manner. Our results demonstrate that the Cln3 cyclin and Whi7 act in a positive feedback loop to release the G1 Cdk-cyclin complex and trigger Start once a critical size has been reached, thus uncovering a key nonlinear mechanism at the earliest known events of cell-cycle entry.
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Affiliation(s)
- Galal Yahya
- Molecular Biology Institute of Barcelona (IBMB-CSIC), 08028 Barcelona, Catalonia, Spain
| | - Eva Parisi
- Molecular Biology Institute of Barcelona (IBMB-CSIC), 08028 Barcelona, Catalonia, Spain
| | - Alba Flores
- Molecular Biology Institute of Barcelona (IBMB-CSIC), 08028 Barcelona, Catalonia, Spain
| | - Carme Gallego
- Molecular Biology Institute of Barcelona (IBMB-CSIC), 08028 Barcelona, Catalonia, Spain
| | - Martí Aldea
- Molecular Biology Institute of Barcelona (IBMB-CSIC), 08028 Barcelona, Catalonia, Spain.
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39
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The MAP kinase Slt2 is involved in vacuolar function and actin remodeling in Saccharomyces cerevisiae mutants affected by endogenous oxidative stress. Appl Environ Microbiol 2013; 79:6459-71. [PMID: 23956390 DOI: 10.1128/aem.01692-13] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Oxidative stress causes transient actin cytoskeleton depolarization and also provokes vacuole fragmentation in wild-type cells. Under conditions of oxidative stress induced by hydrogen peroxide, the Slt2 protein is required to repolarize the actin cytoskeleton and to promote vacuole fusion. In this study, we show that grx3 grx4 and grx5 mutants are cellular models of endogenous oxidative stress. This stress is the result of alterations in iron homeostasis that lead to impairment of vacuolar function and also to disorganization of the actin cytoskeleton. Slt2 overexpression suppresses defects in vacuolar function and actin cytoskeleton organization in the grx3 grx4 mutant. Slt2 exerts this effect independently of the intracellular levels of reactive oxygen species (ROS) and of iron homeostasis. The deletion of SLT2 in the grx3 grx4 mutant results in synthetic lethality related to vacuolar function with substantial vacuole fragmentation. The observation that both Vps4 and Vps73 (two proteins related to vacuole sorting) suppress vacuole fragmentation and actin depolarization in the grx3 grx4 slt2 triple mutant strengthens the hypothesis that Slt2 plays a role in vacuole homeostasis related to actin dynamics. Here we show that in sod1, grx5, and grx3 grx4 slt2 mutants, all of which are affected by chronic oxidative stress, the overexpression of Slt2 favors vacuole fusion through a mechanism dependent on an active actin cytoskeleton.
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40
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Rubinstein A, Hazan O, Chor B, Pinter RY, Kassir Y. The effective application of a discrete transition model to explore cell-cycle regulation in yeast. BMC Res Notes 2013; 6:311. [PMID: 23915717 PMCID: PMC3750494 DOI: 10.1186/1756-0500-6-311] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2013] [Accepted: 07/31/2013] [Indexed: 11/15/2022] Open
Abstract
Background Bench biologists often do not take part in the development of computational models for their systems, and therefore, they frequently employ them as “black-boxes”. Our aim was to construct and test a model that does not depend on the availability of quantitative data, and can be directly used without a need for intensive computational background. Results We present a discrete transition model. We used cell-cycle in budding yeast as a paradigm for a complex network, demonstrating phenomena such as sequential protein expression and activity, and cell-cycle oscillation. The structure of the network was validated by its response to computational perturbations such as mutations, and its response to mating-pheromone or nitrogen depletion. The model has a strong predicative capability, demonstrating how the activity of a specific transcription factor, Hcm1, is regulated, and what determines commitment of cells to enter and complete the cell-cycle. Conclusion The model presented herein is intuitive, yet is expressive enough to elucidate the intrinsic structure and qualitative behavior of large and complex regulatory networks. Moreover our model allowed us to examine multiple hypotheses in a simple and intuitive manner, giving rise to testable predictions. This methodology can be easily integrated as a useful approach for the study of networks, enriching experimental biology with computational insights.
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Affiliation(s)
- Amir Rubinstein
- School of Computer Science, Tel Aviv University, Tel Aviv 69978, Israel
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41
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Balogun FO, Truman AW, Kron SJ. DNA resection proteins Sgs1 and Exo1 are required for G1 checkpoint activation in budding yeast. DNA Repair (Amst) 2013; 12:751-60. [PMID: 23835406 DOI: 10.1016/j.dnarep.2013.06.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Revised: 06/02/2013] [Accepted: 06/03/2013] [Indexed: 12/24/2022]
Abstract
Double-strand breaks (DSBs) in budding yeast trigger activation of DNA damage checkpoints, allowing repair to occur. Although resection is necessary for initiating damage-induced cell cycle arrest in G2, no role has been assigned to it in the activation of G1 checkpoint. Here we demonstrate for the first time that the resection proteins Sgs1 and Exo1 are required for efficient G1 checkpoint activation. We find in G1 arrested cells that histone H2A phosphorylation in response to ionizing radiation is independent of Sgs1 and Exo1. In contrast, these proteins are required for damage-induced recruitment of Rfa1 to the DSB sites, phosphorylation of the Rad53 effector kinase, cell cycle arrest and RNR3 expression. Checkpoint activation in G1 requires the catalytic activity of Sgs1, suggesting that it is DNA resection mediated by Sgs1 that stimulates the damage response pathway rather than protein-protein interactions with other DDR proteins. Together, these results implicate DNA resection, which is thought to be minimal in G1, as necessary for activation of the G1 checkpoint.
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Affiliation(s)
- Fiyinfolu O Balogun
- Committee on Molecular Pathogenesis and Molecular Medicine, University of Chicago, Chicago, IL 60637, USA
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Acetyl-CoA induces transcription of the key G1 cyclin CLN3 to promote entry into the cell division cycle in Saccharomyces cerevisiae. Proc Natl Acad Sci U S A 2013; 110:7318-23. [PMID: 23589851 DOI: 10.1073/pnas.1302490110] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
In budding yeast cells, nutrient repletion induces rapid exit from quiescence and entry into a round of growth and division. The G1 cyclin CLN3 is one of the earliest genes activated in response to nutrient repletion. Subsequent to its activation, hundreds of cell-cycle genes can then be expressed, including the cyclins CLN1/2 and CLB5/6. Although much is known regarding how CLN3 functions to activate downstream targets, the mechanism through which nutrients activate CLN3 transcription in the first place remains poorly understood. Here we show that a central metabolite of glucose catabolism, acetyl-CoA, induces CLN3 transcription by promoting the acetylation of histones present in its regulatory region. Increased rates of acetyl-CoA synthesis enable the Gcn5p-containing Spt-Ada-Gcn5-acetyltransferase transcriptional coactivator complex to catalyze histone acetylation at the CLN3 locus alongside ribosomal and other growth genes to promote entry into the cell division cycle.
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Rodríguez-Colman MJ, Sorolla MA, Vall-Llaura N, Tamarit J, Ros J, Cabiscol E. The FOX transcription factor Hcm1 regulates oxidative metabolism in response to early nutrient limitation in yeast. Role of Snf1 and Tor1/Sch9 kinases. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:2004-15. [PMID: 23481038 DOI: 10.1016/j.bbamcr.2013.02.015] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Revised: 02/13/2013] [Accepted: 02/15/2013] [Indexed: 02/07/2023]
Abstract
Within Saccharomyces cerevisiae, Hcm1is a member of the forkhead transcription factor family with a role in chromosome organization. Our group recently described its involvement in mitochondrial biogenesis and stress resistance, and reports here that Hcm1 played a role in adaptation to respiratory metabolism when glucose or nitrogen was decreased. Regulation of Hcm1 activity occurs in at least three ways: i) protein quantity, ii) subcellular localization, and iii) transcriptional activity. Transcriptional activity was measured using a reporter gene fused to a promoter that contains a binding site for Hcm1. We also analyzed the levels of several genes whose expression is known to be regulated by Hcm1 levels and the role of the main kinases known to respond to nutrients. Lack of sucrose-nonfermenting (Snf1) kinase increases cytoplasmic localization of Hcm1, whereas Δtor1 cells showed a mild increase in nuclear Hcm1. In vitro experiments showed that Snf1 clearly phosphorylates Hcm1 while Sch9 exerts a milder phosphorylation. Although in vitroTor1 does not directly phosphorylate Hcm1, in vivo rapamycin treatment increases nuclear Hcm1. We conclude that Hcm1 participates in the adaptation of cells from fermentation to respiratory metabolism during nutrient scarcity. According to our hypothesis, when nutrient levels decrease, Snf1 phosphorylates Hcm1. This results in a shift from the cytoplasm to the nucleus and increased transcriptional activity of genes involved in respiration, use of alternative energy sources, NAD synthesis and oxidative stress resistance.
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Freeberg MA, Han T, Moresco JJ, Kong A, Yang YC, Lu ZJ, Yates JR, Kim JK. Pervasive and dynamic protein binding sites of the mRNA transcriptome in Saccharomyces cerevisiae. Genome Biol 2013; 14:R13. [PMID: 23409723 PMCID: PMC4053964 DOI: 10.1186/gb-2013-14-2-r13] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2012] [Accepted: 02/14/2013] [Indexed: 01/31/2023] Open
Abstract
Background Protein-RNA interactions are integral components of nearly every aspect of biology, including regulation of gene expression, assembly of cellular architectures, and pathogenesis of human diseases. However, studies in the past few decades have only uncovered a small fraction of the vast landscape of the protein-RNA interactome in any organism, and even less is known about the dynamics of protein-RNA interactions under changing developmental and environmental conditions. Results Here, we describe the gPAR-CLIP (global photoactivatable-ribonucleoside-enhanced crosslinking and immunopurification) approach for capturing regions of the untranslated, polyadenylated transcriptome bound by RNA-binding proteins (RBPs) in budding yeast. We report over 13,000 RBP crosslinking sites in untranslated regions (UTRs) covering 72% of protein-coding transcripts encoded in the genome, confirming 3' UTRs as major sites for RBP interaction. Comparative genomic analyses reveal that RBP crosslinking sites are highly conserved, and RNA folding predictions indicate that secondary structural elements are constrained by protein binding and may serve as generalizable modes of RNA recognition. Finally, 38% of 3' UTR crosslinking sites show changes in RBP occupancy upon glucose or nitrogen deprivation, with major impacts on metabolic pathways as well as mitochondrial and ribosomal gene expression. Conclusions Our study offers an unprecedented view of the pervasiveness and dynamics of protein-RNA interactions in vivo.
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Truman AW, Kristjansdottir K, Wolfgeher D, Hasin N, Polier S, Zhang H, Perrett S, Prodromou C, Jones GW, Kron SJ. CDK-dependent Hsp70 Phosphorylation controls G1 cyclin abundance and cell-cycle progression. Cell 2013; 151:1308-18. [PMID: 23217712 PMCID: PMC3778871 DOI: 10.1016/j.cell.2012.10.051] [Citation(s) in RCA: 102] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2012] [Revised: 08/07/2012] [Accepted: 10/26/2012] [Indexed: 12/31/2022]
Abstract
In budding yeast, the essential functions of Hsp70 chaperones Ssa1–4 are regulated through expression level, isoform specificity, and cochaperone activity. Suggesting a novel regulatory paradigm, we find that phosphorylation of Ssa1 T36 within a cyclin-dependent kinase (CDK) consensus site conserved among Hsp70 proteins alters cochaperone and client interactions. T36 phosphorylation triggers displacement of Ydj1, allowing Ssa1 to bind the G1 cyclin Cln3 and promote its degradation. The stress CDK Pho85 phosphorylates T36 upon nitrogen starvation or pheromone stimulation, destabilizing Cln3 to delay onset of S phase. In turn, the mitotic CDK Cdk1 phosphorylates T36 to block Cln3 accumulation in G2/M. Suggesting broad conservation from yeast to human, CDK-dependent phosphorylation of Hsc70 T38 similarly regulates Cyclin D1 binding and stability. These results establish an active role for Hsp70 chaperones as signal transducers mediating growth control of G1 cyclin abundance and activity.
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Affiliation(s)
- Andrew W Truman
- Ludwig Center for Metastasis Research, The University of Chicago, Chicago, IL 60637, USA
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Phosphate-activated cyclin-dependent kinase stabilizes G1 cyclin to trigger cell cycle entry. Mol Cell Biol 2013; 33:1273-84. [PMID: 23339867 DOI: 10.1128/mcb.01556-12] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
G1 cyclins, in association with a cyclin-dependent kinase (CDK), are universal activators of the transcriptional G1-S machinery during entry into the cell cycle. Regulation of cyclin degradation is crucial for coordinating progression through the cell cycle, but the mechanisms that modulate cyclin stability to control cell cycle entry are still unknown. Here, we show that a lack of phosphate downregulates Cln3 cyclin and leads to G1 arrest in Saccharomyces cerevisiae. The stability of Cln3 protein is diminished in strains with low activity of Pho85, a phosphate-sensing CDK. Cln3 is an in vitro substrate of Pho85, and both proteins interact in vivo. More interestingly, cells that carry a CLN3 allele encoding aspartic acid substitutions at the sites of Pho85 phosphorylation maintain high levels of Cln3 independently of Pho85 activity. Moreover, these cells do not properly arrest in G1 in the absence of phosphate and they die prematurely. Finally, the activity of Pho85 is essential for accumulating Cln3 and for reentering the cell cycle after phosphate refeeding. Taken together, our data indicate that Cln3 is a molecular target of the Pho85 kinase that is required to modulate cell cycle entry in response to environmental changes in nutrient availability.
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Abstract
It has been suggested that irreducible sets of states in Probabilistic Boolean Networks correspond to cellular phenotype. In this study, we identify such sets of states for each phase of the budding yeast cell cycle. We find that these “ergodic sets” underly the cyclin activity levels during each phase of the cell cycle. Our results compare to the observations made in several laboratory experiments as well as the results of differential equation models. Dynamical studies of this model: (i) indicate that under stochastic external signals the continuous oscillating waves of cyclin activity and the opposing waves of CKIs emerge from the logic of a Boolean-based regulatory network without the need for specific biochemical/kinetic parameters; (ii) suggest that the yeast cell cycle network is robust to the varying behavior of cell size (e.g., cell division under nitrogen deprived conditions); (iii) suggest the irreversibility of the Start signal is a function of logic of the G1 regulon, and changing the structure of the regulatory network can render start reversible.
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Petkova MI, Pujol-Carrion N, de la Torre-Ruiz MA. Mtl1 O-mannosylation mediated by both Pmt1 and Pmt2 is important for cell survival under oxidative conditions and TOR blockade. Fungal Genet Biol 2012; 49:903-14. [PMID: 22960125 DOI: 10.1016/j.fgb.2012.08.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Revised: 07/08/2012] [Accepted: 08/20/2012] [Indexed: 11/28/2022]
Abstract
Mtl1 is a cell surface sensor and member of the Pkc1-MAPK pathway that senses oxidative stress and nutrient starvation. Here we demonstrate that the Mtl1 cytoplasmic domain physically interacts with the GEF (GTPase Exchange Factor) protein Rom2 of the CWI (Cell wall Integrity) pathway. Mtl1 is N-glycosylated protein, highly O-mannosylated by Pmt1, Pmt4 and mostly by Pmt2. Mtl1 localises to the bud, septum, the tip of the shmoo and the cell periphery. The O-mannosylation deficiency that occurs in both the pmt1 and pmt2 mutants adversely affects the distribution of Mtl1 on the septum and also hinders Mtl1 localisation in the tip of the shmoo. Here we present results demonstrating that: (i) O-mannosylation and, more specifically that affecting Mtl1 protein is required for cell survival in response to both oxidative stress and TOR blockade; (ii) Slt2 activity is impaired upon rapamycin treatment in both pmt2 and mtl1 mutants; (iii) Mtl1 is transcriptionally upregulated in quiescent conditions, (iv) O-mannosylation mediated by Pmt1 and Pmt2 favours Mtl1 protein stability. We propose a relevant role for Mtl1 O-mannosylation mediated by both Pmt1 and Pmt2 in the response to oxidative stress and in rapamycin treatment.
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Affiliation(s)
- Mima Ivanova Petkova
- Departament de Ciències Mèdiques Bàsiques, IRBLleida, Universidad de Lleida, Lleida 25008, Spain
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Ferrezuelo F, Colomina N, Palmisano A, Garí E, Gallego C, Csikász-Nagy A, Aldea M. The critical size is set at a single-cell level by growth rate to attain homeostasis and adaptation. Nat Commun 2012; 3:1012. [DOI: 10.1038/ncomms2015] [Citation(s) in RCA: 151] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2012] [Accepted: 07/20/2012] [Indexed: 11/09/2022] Open
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Barberis M. Sic1 as a timer of Clb cyclin waves in the yeast cell cycle--design principle of not just an inhibitor. FEBS J 2012; 279:3386-410. [PMID: 22356687 DOI: 10.1111/j.1742-4658.2012.08542.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Cellular systems biology aims to uncover design principles that describe the properties of biological networks through interaction of their components in space and time. The cell cycle is a complex system regulated by molecules that are integrated into functional modules to ensure genome integrity and faithful cell division. In budding yeast, cyclin-dependent kinases (Cdk1/Clb) drive cell cycle progression, being activated and inactivated in a precise temporal sequence. In this module, which we refer to as the 'Clb module', different Cdk1/Clb complexes are regulated to generate waves of Clb activity, a functional property of cell cycle control. The inhibitor Sic1 plays a critical role in the Clb module by binding to and blocking Cdk1/Clb activity, ultimately setting the timing of DNA replication and mitosis. Fifteen years of research subsequent to the identification of Sic1 have lead to the development of an integrative approach that addresses its role in regulating the Clb module. Sic1 is an intrinsically disordered protein and achieves its inhibitory function by cooperative binding, where different structural regions stretch on the Cdk1/Clb surface. Moreover, Sic1 promotes S phase entry, facilitating Cdk1/Clb5 nuclear transport, and therefore revealing a double function of inhibitor/activator that rationalizes a mechanism to prevent precocious DNA replication. Interestingly, the investigation of Clb temporal dynamics by mathematical modelling and experimental validation provides evidence that Sic1 acts as a timer to coordinate oscillations of Clb cyclin waves. Here we review these findings, focusing on the design principle underlying the Clb module, which highlights the role of Sic1 in regulating phase-specific Cdk1/Clb activities.
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Affiliation(s)
- Matteo Barberis
- Institute for Biology, Theoretical Biophysics, Humboldt University Berlin, Germany.
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