1
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Fan J, Dhingra N, Yang T, Yang V, Zhao X. Srs2 binding to PCNA and its sumoylation contribute to RPA antagonism during the DNA damage response. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.28.587206. [PMID: 38586001 PMCID: PMC10996639 DOI: 10.1101/2024.03.28.587206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/09/2024]
Abstract
Activation of the DNA damage checkpoint upon genotoxin treatment induces a multitude of cellular changes, such as cell cycle arrest, to cope with genome stress. After prolonged genotoxin treatment, the checkpoint can be downregulated to allow cell cycle and growth resumption. In yeast, downregulation of the DNA damage checkpoint requires the Srs2 DNA helicase, which removes the ssDNA binding complex RPA and the associated Mec1 checkpoint kinase from DNA, thus dampening Mec1 activation. However, it is unclear whether the 'anti-checkpoint' role of Srs2 is temporally and spatially regulated to both allow timely checkpoint termination and to prevent superfluous RPA removal. Here we address this question by examining regulatory elements of Srs2, including its phosphorylation, sumoylation, and protein-interaction sites. Our genetic analyses and checkpoint level assessment suggest that the RPA countering role of Srs2 is promoted by Srs2 binding to PCNA, which is known to recruit Srs2 to subsets of ssDNA regions. RPA antagonism is further fostered by Srs2 sumoylation, which we found depends on the Srs2-PCNA interaction. Srs2 sumoylation is additionally reliant on Mec1 and peaks after Mec1 activity reaches maximal levels. Collectively, our data provide evidence for a two-step model wherein checkpoint downregulation is facilitated by PCNA-mediated Srs2 recruitment to ssDNA-RPA filaments and the subsequent Srs2 sumoylation stimulated upon Mec1 hyperactivation. We propose that this mechanism allows Mec1 hyperactivation to trigger checkpoint recovery.
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Affiliation(s)
- Jiayi Fan
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065
| | - Nalini Dhingra
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065
| | - Tammy Yang
- City University of New York Hunter College, New York, NY 10065
| | - Vicki Yang
- City University of New York Hunter College, New York, NY 10065
| | - Xiaolan Zhao
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065
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2
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Rojas J, Oz T, Jonak K, Lyzak O, Massaad V, Biriuk O, Zachariae W. Spo13/MEIKIN ensures a Two-Division meiosis by preventing the activation of APC/C Ama1 at meiosis I. EMBO J 2023; 42:e114288. [PMID: 37728253 PMCID: PMC10577557 DOI: 10.15252/embj.2023114288] [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] [Received: 04/14/2023] [Revised: 09/03/2023] [Accepted: 09/04/2023] [Indexed: 09/21/2023] Open
Abstract
Genome haploidization at meiosis depends on two consecutive nuclear divisions, which are controlled by an oscillatory system consisting of Cdk1-cyclin B and the APC/C bound to the Cdc20 activator. How the oscillator generates exactly two divisions has been unclear. We have studied this question in yeast where exit from meiosis involves accumulation of the APC/C activator Ama1 at meiosis II. We show that inactivation of the meiosis I-specific protein Spo13/MEIKIN results in a single-division meiosis due to premature activation of APC/CAma1 . In the wild type, Spo13 bound to the polo-like kinase Cdc5 prevents Ama1 synthesis at meiosis I by stabilizing the translational repressor Rim4. In addition, Cdc5-Spo13 inhibits the activity of Ama1 by converting the B-type cyclin Clb1 from a substrate to an inhibitor of Ama1. Cdc20-dependent degradation of Spo13 at anaphase I unleashes a feedback loop that increases Ama1's synthesis and activity, leading to irreversible exit from meiosis at the second division. Thus, by repressing the exit machinery at meiosis I, Cdc5-Spo13 ensures that cells undergo two divisions to produce haploid gametes.
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Affiliation(s)
- Julie Rojas
- Laboratory of Chromosome BiologyMax Planck Institute of BiochemistryMartinsriedGermany
- Present address:
Laboratory of GeneticsUniversity of Wisconsin‐MadisonMadisonWIUSA
| | - Tugce Oz
- Laboratory of Chromosome BiologyMax Planck Institute of BiochemistryMartinsriedGermany
| | - Katarzyna Jonak
- Laboratory of Chromosome BiologyMax Planck Institute of BiochemistryMartinsriedGermany
- Present address:
Institute of Biochemistry and BiophysicsPolish Academy of SciencesWarsawPoland
| | - Oleksii Lyzak
- Laboratory of Chromosome BiologyMax Planck Institute of BiochemistryMartinsriedGermany
| | - Vinal Massaad
- Laboratory of Chromosome BiologyMax Planck Institute of BiochemistryMartinsriedGermany
| | - Olha Biriuk
- Laboratory of Chromosome BiologyMax Planck Institute of BiochemistryMartinsriedGermany
| | - Wolfgang Zachariae
- Laboratory of Chromosome BiologyMax Planck Institute of BiochemistryMartinsriedGermany
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3
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Yam CQX, Lim HH, Surana U. DNA damage checkpoint execution and the rules of its disengagement. Front Cell Dev Biol 2022; 10:1020643. [PMID: 36274841 PMCID: PMC9582513 DOI: 10.3389/fcell.2022.1020643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Accepted: 09/21/2022] [Indexed: 11/13/2022] Open
Abstract
Chromosomes are susceptible to damage during their duplication and segregation or when exposed to genotoxic stresses. Left uncorrected, these lesions can result in genomic instability, leading to cells’ diminished fitness, unbridled proliferation or death. To prevent such fates, checkpoint controls transiently halt cell cycle progression to allow time for the implementation of corrective measures. Prominent among these is the DNA damage checkpoint which operates at G2/M transition to ensure that cells with damaged chromosomes do not enter the mitotic phase. The execution and maintenance of cell cycle arrest are essential aspects of G2/M checkpoint and have been studied in detail. Equally critical is cells’ ability to switch-off the checkpoint controls after a successful completion of corrective actions and to recommence cell cycle progression. Interestingly, when corrective measures fail, cells can mount an unusual cellular response, termed adaptation, where they escape checkpoint arrest and resume cell cycle progression with damaged chromosomes at the cost of genome instability or even death. Here, we discuss the DNA damage checkpoint, the mitotic networks it inhibits to prevent segregation of damaged chromosomes and the strategies cells employ to quench the checkpoint controls to override the G2/M arrest.
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Affiliation(s)
| | - Hong Hwa Lim
- A*STAR Singapore Immunology Network, Singapore, Singapore
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Uttam Surana
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
- Department of Pharmacology, National University of Singapore, Singapore, Singapore
- *Correspondence: Uttam Surana,
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4
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Li J, Yang Y, Wang H, Ma D, Wang H, Chu L, Zhang Y, Gao Y. Baicalein Ameliorates Myocardial Ischemia Through Reduction of Oxidative Stress, Inflammation and Apoptosis via TLR4/MyD88/MAPK S/NF-κB Pathway and Regulation of Ca 2+ Homeostasis by L-type Ca 2+ Channels. Front Pharmacol 2022; 13:842723. [PMID: 35370644 PMCID: PMC8967179 DOI: 10.3389/fphar.2022.842723] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Accepted: 01/31/2022] [Indexed: 12/12/2022] Open
Abstract
Background: Baicalein (Bai) is the principal ingredient of Scutellaria baicalensis Georgi. Reports concerning the therapeutic advantages in treating cardiovascular diseases have been published. However, its protective mechanism towards myocardial ischemia (MI) is undefined. Objective: The aim of this study was to investigate the protective mechanisms of Bai on mouse and rat models of MI. Methods: Mice were pre-treated with Bai (30 and 60 mg/kg/day) for 7 days followed by subcutaneous injections of isoproterenol (ISO, 85 mg/kg/day) for 2 days to establish the MI model. Electrocardiograms were recorded and serum was used to detect creatine kinase (CK), lactate dehydrogenase (LDH), superoxide dismutase (SOD), catalase (CAT), glutathione (GSH) and malondialdehyde (MDA). Cardiac tissues were used to detect Ca2+ concentration, morphological pathologies, reactive oxygen species (ROS), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). In addition, the expression levels of Bcl-2-associated X (Bax), B cell lymphoma-2 (Bcl-2), Caspase-3, Toll-like receptor-4 (TLR4), myeloid differentiation protein 88 (MyD88), nuclear factor-kappa B (NF-κB), p-p38, p-extracellular signal-regulated kinase1/2 (p-ERK1/2) and c-Jun N-terminal kinase (p-JNK) were assessed by western blots in myocardial tissues. The effects of Bai on L-type Ca2+ currents (ICa-L), contractility and Ca2+ transients in rat isolated cardiomyocytes were monitored by using patch clamp technique and IonOptix system. Moreover, ISO-induced H9c2 myocardial injury was used to detect levels of inflammation and apoptosis. Results: Bai caused an improvement in heart rate, ST-segment and heart coefficients. Moreover, Bai led to a reduction in CK, LDH and Ca2+ concentrations and improved morphological pathologies. Bai inhibited ROS generation and reinstated SOD, CAT and GSH activities in addition to inhibition of replenishing MDA content. Also, expressions of IL-6 and TNF-α in addition to Bax and Caspase-3 were suppressed, while Bcl-2 expression was upregulated. Bai inhibited protein expressions of TLR4/MyD88/MAPKS/NF-κB and significantly inhibited ICa-L, myocyte contraction and Ca2+ transients. Furthermore, Bai caused a reduction in inflammation and apoptosis in H9c2 cells. Conclusions: Bai demonstrated ameliorative actions towards MI, which might have been related to attenuation of oxidative stress, inflammation and apoptosis via suppression of TLR4/MyD88/MAPKS/NF-κB pathway and adjustment of Ca2+ homeostasis via L-type Ca2+ channels.
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Affiliation(s)
- Jinghan Li
- School of Basic Medicine, Hebei University of Chinese Medicine, Shijiazhuang, China
| | - Yakun Yang
- School of Pharmacy, Hebei University of Chinese Medicine, Shijiazhuang, China
| | - Hua Wang
- School of Basic Medicine, Hebei University of Chinese Medicine, Shijiazhuang, China
| | - Donglai Ma
- School of Pharmacy, Hebei University of Chinese Medicine, Shijiazhuang, China
| | - Hongfang Wang
- School of Pharmacy, Hebei University of Chinese Medicine, Shijiazhuang, China
| | - Li Chu
- School of Pharmacy, Hebei University of Chinese Medicine, Shijiazhuang, China.,Hebei Key Laboratory of Integrative Medicine on Liver-Kidney Patterns, Hebei University of Chinese Medicine, Shijiazhuang, China
| | - Yuanyuan Zhang
- School of Pharmacy, Hebei University of Chinese Medicine, Shijiazhuang, China
| | - Yonggang Gao
- School of Basic Medicine, Hebei University of Chinese Medicine, Shijiazhuang, China
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5
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Haluska C, Jin F, Wang Y. Protein phosphatase 2A (PP2A) promotes anaphase entry after DNA replication stress in budding yeast. Mol Biol Cell 2021; 32:ar36. [PMID: 34668760 PMCID: PMC8694091 DOI: 10.1091/mbc.e21-04-0222] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 10/01/2021] [Accepted: 10/05/2021] [Indexed: 12/31/2022] Open
Abstract
DNA replication stress activates the S-phase checkpoint that arrests the cell cycle, but it is poorly understood how cells recover from this arrest. Cyclin-dependent kinase (CDK) and protein phosphatase 2A (PP2A) are key cell cycle regulators, and Cdc55 is a regulatory subunit of PP2A in budding yeast. We found that yeast cells lacking functional PP2ACdc55 showed slow growth in the presence of hydroxyurea (HU), a DNA synthesis inhibitor, without obvious viability loss. Moreover, PP2A mutants exhibited delayed anaphase entry and sustained levels of anaphase inhibitor Pds1 after HU treatment. A DNA damage checkpoint Chk1 phosphorylates and stabilizes Pds1. We show that chk1Δ and mutation of the Chk1 phosphorylation sites in Pds1 largely restored efficient anaphase entry in PP2A mutants after HU treatment. In addition, deletion of SWE1, which encodes the inhibitory kinase for CDK or mutation of the Swe1 phosphorylation site in CDK (cdc28F19), also suppressed the anaphase entry delay in PP2A mutants after HU treatment. Our genetic data suggest that Swe1/CDK acts upstream of Pds1. Surprisingly, cdc55Δ showed significant suppression to the viability loss of S-phase checkpoint mutants during DNA synthesis block. Together, our results uncover a PP2A-Swe1-CDK-Chk1-Pds1 axis that promotes recovery from DNA replication stress.
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Affiliation(s)
- Cory Haluska
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL 32306-4300
| | - Fengzhi Jin
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL 32306-4300
| | - Yanchang Wang
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL 32306-4300
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6
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Liakopoulos D. Coupling DNA Replication and Spindle Function in Saccharomyces cerevisiae. Cells 2021; 10:cells10123359. [PMID: 34943867 PMCID: PMC8699587 DOI: 10.3390/cells10123359] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 11/24/2021] [Accepted: 11/27/2021] [Indexed: 12/02/2022] Open
Abstract
In the yeast Saccharomyces cerevisiae DNA replication and spindle assembly can overlap. Therefore, signaling mechanisms modulate spindle dynamics in order to ensure correct timing of chromosome segregation relative to genome duplication, especially when replication is incomplete or the DNA becomes damaged. This review focuses on the molecular mechanisms that coordinate DNA replication and spindle dynamics, as well as on the role of spindle-dependent forces in DNA repair. Understanding the coupling between genome duplication and spindle function in yeast cells can provide important insights into similar processes operating in other eukaryotic organisms, including humans.
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Affiliation(s)
- Dimitris Liakopoulos
- CRBM, Université de Montpellier, CNRS, 1919 Route de Mende, 34293 Montpellier, France;
- Laboratory of Biology, Faculty of Medicine, University of Ioannina, 45110 Ioannina, Greece
- University Research Center of loannina, University of Ioannina, 45110 Ioannina, Greece
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7
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de La Roche Saint-André C, Géli V. Set1-dependent H3K4 methylation becomes critical for limiting DNA damage in response to changes in S-phase dynamics in Saccharomyces cerevisiae. DNA Repair (Amst) 2021; 105:103159. [PMID: 34174709 DOI: 10.1016/j.dnarep.2021.103159] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Revised: 05/27/2021] [Accepted: 06/13/2021] [Indexed: 11/29/2022]
Abstract
DNA replication is a highly regulated process that occurs in the context of chromatin structure and is sensitive to several histone post-translational modifications. In Saccharomyces cerevisiae, the histone methylase Set1 is responsible for the transcription-dependent deposition of H3K4 methylation (H3K4me) throughout the genome. Here we show that a combination of a hypomorphic replication mutation (orc5-1) with the absence of Set1 (set1Δ) compromises the progression through S-phase, and this is associated with a large increase in DNA damage. The ensuing DNA damage checkpoint activation, in addition to that of the spindle assembly checkpoint, restricts the growth of orc5-1 set1Δ. The opposite effects of the lack of RNase H activity and the reduction of histone levels on orc5-1 set1Δ viability are in agreement with their expected effects on replication fork progression. We propose that the role of H3K4 methylation during DNA replication becomes critical when the replication forks acceleration due to decreased origin firing in the orc5-1 background increases the risk for transcription replication conflicts. Furthermore, we show that an increase of reactive oxygen species levels, likely a consequence of the elevated DNA damage, is partly responsible for the lethality in orc5-1 set1Δ.
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Affiliation(s)
- Christophe de La Roche Saint-André
- Marseille Cancer Research Center (CRCM), U1068 Inserm, UMR7258 CNRS, Aix Marseille University, Institut Paoli-Calmettes, Marseille, France.
| | - Vincent Géli
- Marseille Cancer Research Center (CRCM), U1068 Inserm, UMR7258 CNRS, Aix Marseille University, Institut Paoli-Calmettes, Marseille, France
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8
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Pirincci Ercan D, Chrétien F, Chakravarty P, Flynn HR, Snijders AP, Uhlmann F. Budding yeast relies on G 1 cyclin specificity to couple cell cycle progression with morphogenetic development. SCIENCE ADVANCES 2021; 7:eabg0007. [PMID: 34088668 PMCID: PMC8177710 DOI: 10.1126/sciadv.abg0007] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Accepted: 04/19/2021] [Indexed: 05/04/2023]
Abstract
Two models have been put forward for cyclin-dependent kinase (Cdk) control of the cell cycle. In the qualitative model, cell cycle events are ordered by distinct substrate specificities of successive cyclin waves. Alternatively, in the quantitative model, the gradual rise of Cdk activity from G1 phase to mitosis leads to ordered substrate phosphorylation at sequential thresholds. Here, we study the relative contributions of qualitative and quantitative Cdk control in Saccharomyces cerevisiae All S phase and mitotic cyclins can be replaced by a single mitotic cyclin, albeit at the cost of reduced fitness. A single cyclin can also replace all G1 cyclins to support ordered cell cycle progression, fulfilling key predictions of the quantitative model. However, single-cyclin cells fail to polarize or grow buds and thus cannot survive. Our results suggest that budding yeast has become dependent on G1 cyclin specificity to couple cell cycle progression to essential morphogenetic events.
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Affiliation(s)
| | - Florine Chrétien
- Chromosome Segregation Laboratory, The Francis Crick Institute, London, UK
| | - Probir Chakravarty
- Bioinformatics and Biostatistics Science Technology Platform, The Francis Crick Institute, London, UK
| | - Helen R Flynn
- Proteomics Science Technology Platform, The Francis Crick Institute, London, UK
| | | | - Frank Uhlmann
- Chromosome Segregation Laboratory, The Francis Crick Institute, London, UK.
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9
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Higgins R, Kabbaj MH, Sherwin D, Howell LA, Hatcher A, Tomko RJ, Wang Y. The Cdc48 Complex Alleviates the Cytotoxicity of Misfolded Proteins by Regulating Ubiquitin Homeostasis. Cell Rep 2021; 32:107898. [PMID: 32668237 DOI: 10.1016/j.celrep.2020.107898] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 05/04/2020] [Accepted: 06/22/2020] [Indexed: 10/23/2022] Open
Abstract
The accumulation of misfolded proteins is associated with multiple neurodegenerative disorders, but it remains poorly defined how this accumulation causes cytotoxicity. Here, we demonstrate that the Cdc48/p97 segregase machinery drives the clearance of ubiquitinated model misfolded protein Huntingtin (Htt103QP) and limits its aggregation. Nuclear ubiquitin ligase San1 acts upstream of Cdc48 to ubiquitinate Htt103QP. Unexpectedly, deletion of SAN1 and/or its cytosolic counterpart UBR1 rescues the toxicity associated with Cdc48 deficiency, suggesting that ubiquitin depletion, rather than compromised proteolysis of misfolded proteins, causes the growth defect in cells with Cdc48 deficiency. Indeed, Cdc48 deficiency leads to elevated protein ubiquitination levels and decreased free ubiquitin, which depends on San1/Ubr1. Furthermore, enhancing free ubiquitin levels rescues the toxicity in various Cdc48 pathway mutants and restores normal turnover of a known Cdc48-independent substrate. Our work highlights a previously unappreciated function for Cdc48 in ensuring the regeneration of monoubiquitin that is critical for normal cellular function.
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Affiliation(s)
- Ryan Higgins
- Department of Biomedical Sciences, College of Medicine, Florida State University, 1115 West Call Street, Tallahassee, FL 32306, USA
| | - Marie-Helene Kabbaj
- Department of Biomedical Sciences, College of Medicine, Florida State University, 1115 West Call Street, Tallahassee, FL 32306, USA
| | - Delaney Sherwin
- Department of Biomedical Sciences, College of Medicine, Florida State University, 1115 West Call Street, Tallahassee, FL 32306, USA
| | - Lauren A Howell
- Department of Biomedical Sciences, College of Medicine, Florida State University, 1115 West Call Street, Tallahassee, FL 32306, USA
| | - Alexa Hatcher
- College of Nursing, Florida State University, 600 West College Avenue, Tallahassee, FL 32306, USA
| | - Robert J Tomko
- Department of Biomedical Sciences, College of Medicine, Florida State University, 1115 West Call Street, Tallahassee, FL 32306, USA
| | - Yanchang Wang
- Department of Biomedical Sciences, College of Medicine, Florida State University, 1115 West Call Street, Tallahassee, FL 32306, USA.
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10
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Manohar S, Yu Q, Gygi SP, King RW. The Insulin Receptor Adaptor IRS2 is an APC/C Substrate That Promotes Cell Cycle Protein Expression and a Robust Spindle Assembly Checkpoint. Mol Cell Proteomics 2020; 19:1450-1467. [PMID: 32554797 PMCID: PMC8143631 DOI: 10.1074/mcp.ra120.002069] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 06/01/2020] [Indexed: 01/21/2023] Open
Abstract
Insulin receptor substrate 2 (IRS2) is an essential adaptor that mediates signaling downstream of the insulin receptor and other receptor tyrosine kinases. Transduction through IRS2-dependent pathways is important for coordinating metabolic homeostasis, and dysregulation of IRS2 causes systemic insulin signaling defects. Despite the importance of maintaining proper IRS2 abundance, little is known about what factors mediate its protein stability. We conducted an unbiased proteomic screen to uncover novel substrates of the Anaphase Promoting Complex/Cyclosome (APC/C), a ubiquitin ligase that controls the abundance of key cell cycle regulators. We found that IRS2 levels are regulated by APC/C activity and that IRS2 is a direct APC/C target in G1 Consistent with the APC/C's role in degrading cell cycle regulators, quantitative proteomic analysis of IRS2-null cells revealed a deficiency in proteins involved in cell cycle progression. We further show that cells lacking IRS2 display a weakened spindle assembly checkpoint in cells treated with microtubule inhibitors. Together, these findings reveal a new pathway for IRS2 turnover and indicate that IRS2 is a component of the cell cycle control system in addition to acting as an essential metabolic regulator.
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Affiliation(s)
- Sandhya Manohar
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, USA
| | - Qing Yu
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, USA
| | - Steven P Gygi
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, USA
| | - Randall W King
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, USA.
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11
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Khondker S, Kajjo S, Chandler-Brown D, Skotheim J, Rudner A, Ikui AE. PP2A Cdc55 dephosphorylates Pds1 and inhibits spindle elongation in S. cerevisiae. J Cell Sci 2020; 133:jcs243766. [PMID: 32591482 PMCID: PMC7406319 DOI: 10.1242/jcs.243766] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Accepted: 06/11/2020] [Indexed: 11/20/2022] Open
Abstract
PP2ACdc55 (the form of protein phosphatase 2A containing Cdc55) regulates cell cycle progression by reversing cyclin-dependent kinase (CDK)- and polo-like kinase (Cdc5)-dependent phosphorylation events. In S. cerevisiae, Cdk1 phosphorylates securin (Pds1), which facilitates Pds1 binding and inhibits separase (Esp1). During anaphase, Esp1 cleaves the cohesin subunit Scc1 and promotes spindle elongation. Here, we show that PP2ACdc55 directly dephosphorylates Pds1 both in vivo and in vitro Pds1 hyperphosphorylation in a cdc55 deletion mutant enhanced the Pds1-Esp1 interaction, which played a positive role in Pds1 nuclear accumulation and in spindle elongation. We also show that nuclear PP2ACdc55 plays a role during replication stress to inhibit spindle elongation. This pathway acted independently of the known Mec1, Swe1 or spindle assembly checkpoint (SAC) checkpoint pathways. We propose a model where Pds1 dephosphorylation by PP2ACdc55 disrupts the Pds1-Esp1 protein interaction and inhibits Pds1 nuclear accumulation, which prevents spindle elongation, a process that is elevated during replication stress.
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Affiliation(s)
- Shoily Khondker
- Biology Department, Brooklyn College, The City University of New York, Brooklyn, NY 11238, USA
- Biology Program, CUNY Graduate Center, New York, NY 10016, USA
| | - Sam Kajjo
- Ottawa Institute of Systems Biology and Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON, K1N 6N5, Canada
| | | | - Jan Skotheim
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Adam Rudner
- Ottawa Institute of Systems Biology and Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON, K1N 6N5, Canada
| | - Amy E. Ikui
- Biology Department, Brooklyn College, The City University of New York, Brooklyn, NY 11238, USA
- Biology Program, CUNY Graduate Center, New York, NY 10016, USA
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12
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Yam CQX, Chia DB, Shi I, Lim HH, Surana U. Dun1, a Chk2-related kinase, is the central regulator of securin-separase dynamics during DNA damage signaling. Nucleic Acids Res 2020; 48:6092-6107. [PMID: 32402080 PMCID: PMC7293041 DOI: 10.1093/nar/gkaa355] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Revised: 04/23/2020] [Accepted: 04/29/2020] [Indexed: 01/26/2023] Open
Abstract
The DNA damage checkpoint halts cell cycle progression in G2 in response to genotoxic insults. Central to the execution of cell cycle arrest is the checkpoint-induced stabilization of securin-separase complex (yeast Pds1-Esp1). The checkpoint kinases Chk1 and Chk2 (yeast Chk1 and Rad53) are thought to critically contribute to the stability of securin-separase complex by phosphorylation of securin, rendering it resistant to proteolytic destruction by the anaphase promoting complex (APC). Dun1, a Rad53 paralog related to Chk2, is also essential for checkpoint-imposed arrest. Dun1 is required for the DNA damage-induced transcription of DNA repair genes; however, its role in the execution of cell cycle arrest remains unknown. Here, we show that Dun1′s role in checkpoint arrest is independent of its involvement in the transcription of repair genes. Instead, Dun1 is necessary to prevent Pds1 destruction during DNA damage in that the Dun1-deficient cells degrade Pds1, escape G2 arrest and undergo mitosis despite the presence of checkpoint-active Chk1 and Rad53. Interestingly, proteolytic degradation of Pds1 in the absence of Dun1 is mediated not by APC but by the HECT domain-containing E3 ligase Rsp5. Our results suggest a regulatory scheme in which Dun1 prevents chromosome segregation during DNA damage by inhibiting Rsp5-mediated proteolytic degradation of securin Pds1.
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Affiliation(s)
- Candice Qiu Xia Yam
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Proteos, 61 Biopolis Drive, Singapore.,Bioprocessing Technology Institute, A*STAR, Singapore
| | - David Boy Chia
- Biotransformation Innovation Platform, A*STAR, Singapore
| | - Idina Shi
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Proteos, 61 Biopolis Drive, Singapore
| | - Hong Hwa Lim
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Proteos, 61 Biopolis Drive, Singapore.,Bioprocessing Technology Institute, A*STAR, Singapore
| | - Uttam Surana
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research (A*STAR), Proteos, 61 Biopolis Drive, Singapore.,Bioprocessing Technology Institute, A*STAR, Singapore.,Biotransformation Innovation Platform, A*STAR, Singapore.,Department of Pharmacology, National University of Singapore, Singapore
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13
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Matellán L, Monje-Casas F. Regulation of Mitotic Exit by Cell Cycle Checkpoints: Lessons From Saccharomyces cerevisiae. Genes (Basel) 2020; 11:E195. [PMID: 32059558 PMCID: PMC7074328 DOI: 10.3390/genes11020195] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 02/07/2020] [Accepted: 02/11/2020] [Indexed: 02/06/2023] Open
Abstract
In order to preserve genome integrity and their ploidy, cells must ensure that the duplicated genome has been faithfully replicated and evenly distributed before they complete their division by mitosis. To this end, cells have developed highly elaborated checkpoints that halt mitotic progression when problems in DNA integrity or chromosome segregation arise, providing them with time to fix these issues before advancing further into the cell cycle. Remarkably, exit from mitosis constitutes a key cell cycle transition that is targeted by the main mitotic checkpoints, despite these surveillance mechanisms being activated by specific intracellular signals and acting at different stages of cell division. Focusing primarily on research carried out using Saccharomyces cerevisiae as a model organism, the aim of this review is to provide a general overview of the molecular mechanisms by which the major cell cycle checkpoints control mitotic exit and to highlight the importance of the proper regulation of this process for the maintenance of genome stability during the distribution of the duplicated chromosomes between the dividing cells.
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Affiliation(s)
| | - Fernando Monje-Casas
- Centro Andaluz de Biología Molecular y Medicina Regenerativa (CABIMER), Spanish National Research Council (CSIC)—University of Seville—University Pablo de Olavide, Avda, Américo Vespucio, 24, 41092 Sevilla, Spain;
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14
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Fumasoni M, Murray AW. The evolutionary plasticity of chromosome metabolism allows adaptation to constitutive DNA replication stress. eLife 2020; 9:e51963. [PMID: 32043971 PMCID: PMC7069727 DOI: 10.7554/elife.51963] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Accepted: 02/11/2020] [Indexed: 01/22/2023] Open
Abstract
Many biological features are conserved and thus considered to be resistant to evolutionary change. While rapid genetic adaptation following the removal of conserved genes has been observed, we often lack a mechanistic understanding of how adaptation happens. We used the budding yeast, Saccharomyces cerevisiae, to investigate the evolutionary plasticity of chromosome metabolism, a network of evolutionary conserved modules. We experimentally evolved cells constitutively experiencing DNA replication stress caused by the absence of Ctf4, a protein that coordinates the enzymatic activities at replication forks. Parallel populations adapted to replication stress, over 1000 generations, by acquiring multiple, concerted mutations. These mutations altered conserved features of two chromosome metabolism modules, DNA replication and sister chromatid cohesion, and inactivated a third, the DNA damage checkpoint. The selected mutations define a functionally reproducible evolutionary trajectory. We suggest that the evolutionary plasticity of chromosome metabolism has implications for genome evolution in natural populations and cancer.
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Affiliation(s)
- Marco Fumasoni
- Department of Molecular and Cellular Biology, Harvard UniversityCambridgeUnited States
| | - Andrew W Murray
- Department of Molecular and Cellular Biology, Harvard UniversityCambridgeUnited States
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15
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Leitao RM, Jasani A, Talavara RA, Pham A, Okobi QJ, Kellogg DR. A Conserved PP2A Regulatory Subunit Enforces Proportional Relationships Between Cell Size and Growth Rate. Genetics 2019; 213:517-528. [PMID: 31488515 PMCID: PMC6781898 DOI: 10.1534/genetics.119.301012] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Accepted: 08/10/2019] [Indexed: 11/18/2022] Open
Abstract
Cell size is proportional to growth rate. Thus, cells growing rapidly in rich nutrients can be nearly twice the size of cells growing slowly in poor nutrients. This proportional relationship appears to hold across all orders of life, yet the underlying mechanisms are unknown. In budding yeast, most growth occurs during mitosis, and the proportional relationship between cell size and growth rate is therefore enforced primarily by modulating growth in mitosis. When growth is slow, the duration of mitosis is increased to allow more time for growth, yet the amount of growth required to complete mitosis is reduced, which leads to the birth of small daughter cells. Previous studies have found that Rts1, a member of the conserved B56 family of protein phosphatase 2A regulatory subunits, works in a TORC2 signaling network that influences cell size and growth rate. However, it was unclear whether Rts1 influences cell growth and size in mitosis. Here, we show that Rts1 is required for the proportional relationship between cell size and growth rate during mitosis. Moreover, nutrients and Rts1 influence the duration and extent of growth in mitosis via Wee1 and Pds1/securin, two conserved regulators of mitotic progression. Together, the data are consistent with a model in which global signals that set growth rate also set the critical amount of growth required for cell cycle progression, which would provide a simple mechanistic explanation for the proportional relationship between cell size and growth rate.
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Affiliation(s)
- Ricardo M Leitao
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, California 95064
| | - Akshi Jasani
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, California 95064
| | - Rafael A Talavara
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, California 95064
| | - Annie Pham
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, California 95064
| | - Quincy J Okobi
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, California 95064
| | - Douglas R Kellogg
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, California 95064
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16
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Lanz MC, Dibitetto D, Smolka MB. DNA damage kinase signaling: checkpoint and repair at 30 years. EMBO J 2019; 38:e101801. [PMID: 31393028 PMCID: PMC6745504 DOI: 10.15252/embj.2019101801] [Citation(s) in RCA: 150] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Revised: 07/03/2019] [Accepted: 07/24/2019] [Indexed: 12/27/2022] Open
Abstract
From bacteria to mammalian cells, damaged DNA is sensed and targeted by DNA repair pathways. In eukaryotes, kinases play a central role in coordinating the DNA damage response. DNA damage signaling kinases were identified over two decades ago and linked to the cell cycle checkpoint concept proposed by Weinert and Hartwell in 1988. Connections between the DNA damage signaling kinases and DNA repair were scant at first, and the initial perception was that the importance of these kinases for genome integrity was largely an indirect effect of their roles in checkpoints, DNA replication, and transcription. As more substrates of DNA damage signaling kinases were identified, it became clear that they directly regulate a wide range of DNA repair factors. Here, we review our current understanding of DNA damage signaling kinases, delineating the key substrates in budding yeast and humans. We trace the progress of the field in the last 30 years and discuss our current understanding of the major substrate regulatory mechanisms involved in checkpoint responses and DNA repair.
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Affiliation(s)
- Michael Charles Lanz
- Department of Molecular Biology and GeneticsWeill Institute for Cell and Molecular BiologyCornell UniversityIthacaNYUSA
| | - Diego Dibitetto
- Department of Molecular Biology and GeneticsWeill Institute for Cell and Molecular BiologyCornell UniversityIthacaNYUSA
| | - Marcus Bustamante Smolka
- Department of Molecular Biology and GeneticsWeill Institute for Cell and Molecular BiologyCornell UniversityIthacaNYUSA
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17
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Zhou Q, Pham KTM, Hu H, Kurasawa Y, Li Z. A kinetochore-based ATM/ATR-independent DNA damage checkpoint maintains genomic integrity in trypanosomes. Nucleic Acids Res 2019; 47:7973-7988. [PMID: 31147720 PMCID: PMC6736141 DOI: 10.1093/nar/gkz476] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Revised: 04/23/2019] [Accepted: 05/17/2019] [Indexed: 02/02/2023] Open
Abstract
DNA damage-induced cell cycle checkpoints serve as surveillance mechanisms to maintain genomic stability, and are regulated by ATM/ATR-mediated signaling pathways that are conserved from yeast to humans. Trypanosoma brucei, an early divergent microbial eukaryote, lacks key components of the conventional DNA damage-induced G2/M cell cycle checkpoint and the spindle assembly checkpoint, and nothing is known about how T. brucei controls its cell cycle checkpoints. Here we discover a kinetochore-based, DNA damage-induced metaphase checkpoint in T. brucei. MMS-induced DNA damage triggers a metaphase arrest by modulating the abundance of the outer kinetochore protein KKIP5 in an Aurora B kinase- and kinetochore-dependent, but ATM/ATR-independent manner. Overexpression of KKIP5 arrests cells at metaphase through stabilizing the mitotic cyclin CYC6 and the cohesin subunit SCC1, mimicking DNA damage-induced metaphase arrest, whereas depletion of KKIP5 alleviates the DNA damage-induced metaphase arrest and causes chromosome mis-segregation and aneuploidy. These findings suggest that trypanosomes employ a novel DNA damage-induced metaphase checkpoint to maintain genomic integrity.
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Affiliation(s)
- Qing Zhou
- Department of Microbiology and Molecular Genetics, McGovern Medical School, University of Texas Health Science Center at Houston, TX 77030, USA
| | - Kieu T M Pham
- Department of Microbiology and Molecular Genetics, McGovern Medical School, University of Texas Health Science Center at Houston, TX 77030, USA
| | - Huiqing Hu
- Department of Microbiology and Molecular Genetics, McGovern Medical School, University of Texas Health Science Center at Houston, TX 77030, USA
| | - Yasuhiro Kurasawa
- Department of Microbiology and Molecular Genetics, McGovern Medical School, University of Texas Health Science Center at Houston, TX 77030, USA
| | - Ziyin Li
- Department of Microbiology and Molecular Genetics, McGovern Medical School, University of Texas Health Science Center at Houston, TX 77030, USA
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18
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Sparapani S, Bachewich C. Characterization of a novel separase-interacting protein and candidate new securin, Eip1p, in the fungal pathogen Candida albicans. Mol Biol Cell 2019; 30:2469-2489. [PMID: 31411946 PMCID: PMC6743357 DOI: 10.1091/mbc.e18-11-0696] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Revised: 07/03/2019] [Accepted: 07/22/2019] [Indexed: 12/12/2022] Open
Abstract
Proper chromosome segregation is crucial for maintaining genomic stability and dependent on separase, a conserved and essential cohesin protease. Securins are key regulators of separases, but remain elusive in many organisms due to sequence divergence. Here, we demonstrate that the separase homologue Esp1p in the ascomycete Candida albicans, an important pathogen of humans, is essential for chromosome segregation. However, C. albicans lacks a sequence homologue of securins found in model ascomycetes. We sought a functional homologue through identifying Esp1p interacting factors. Affinity purification of Esp1p and mass spectrometry revealed Esp1p-Interacting Protein1 (Eip1p)/Orf19.955p, an uncharacterized protein specific to Candida species. Functional analyses demonstrated that Eip1p is important for chromosome segregation but not essential, and modulated in an APCCdc20-dependent manner, similar to securins. Eip1p is strongly enriched in response to methyl methanesulfate (MMS) or hydroxyurea (HU) treatment, and its depletion partially suppresses an MMS or HU-induced metaphase block. Further, Eip1p depletion reduces Mcd1p/Scc1p, a cohesin subunit and separase target. Thus, Eip1p may function as a securin. However, other defects in Eip1p-depleted cells suggest additional roles. Overall, the results introduce a candidate new securin, provide an approach for identifying these divergent proteins, reveal a putative anti-fungal therapeutic target, and highlight variations in mitotic regulation in eukaryotes.
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Affiliation(s)
- Samantha Sparapani
- Department of Biology, Concordia University, Montreal, QC H4B 1R6, Canada
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19
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Ballew O, Lacefield S. The DNA damage checkpoint and the spindle position checkpoint: guardians of meiotic commitment. Curr Genet 2019; 65:1135-1140. [PMID: 31028453 DOI: 10.1007/s00294-019-00981-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Revised: 04/19/2019] [Accepted: 04/22/2019] [Indexed: 12/16/2022]
Abstract
Exogenous signals induce cells to enter the specialized cell division process of meiosis, which produces haploid gametes from diploid progenitor cells. Once cells initiate the meiotic divisions, it is imperative that they complete meiosis. Inappropriate exit from meiosis and entrance into mitosis can create polyploid cells and can lead to germline tumors. Saccharomyces cerevisiae cells enter meiosis when starved of nutrients but can return to mitosis if provided nutrient-rich medium before a defined commitment point. Once past the meiotic commitment point in prometaphase I, cells stay committed to meiosis even in the presence of a mitosis-inducing signal. Recent research investigated the maintenance of meiotic commitment in budding yeast and found that two checkpoints that do not normally function in meiosis I, the DNA damage checkpoint and the spindle position checkpoint, have crucial functions in maintaining meiotic commitment. Here, we review these findings and discuss how the mitosis-inducing signal of nutrient-rich medium could activate these two checkpoints in meiosis to prevent inappropriate meiotic exit.
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Affiliation(s)
- Olivia Ballew
- Department of Biology, Indiana University, Bloomington, IN, USA
| | - Soni Lacefield
- Department of Biology, Indiana University, Bloomington, IN, USA.
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20
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The DNA Damage Checkpoint and the Spindle Position Checkpoint Maintain Meiotic Commitment in Saccharomyces cerevisiae. Curr Biol 2019; 29:449-460.e2. [PMID: 30686741 DOI: 10.1016/j.cub.2018.12.043] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2018] [Revised: 11/26/2018] [Accepted: 12/21/2018] [Indexed: 01/17/2023]
Abstract
During meiosis, diploid progenitor cells undergo one round of DNA replication followed by two rounds of chromosome segregation to form haploid gametes. Once cells initiate the meiotic divisions, it is imperative that they finish meiosis. A failure to maintain meiosis can result in highly aberrant polyploid cells, which could lead to oncogenesis in the germline. How cells stay committed to finishing meiosis, even in the presence of a mitosis-inducing signal, is poorly understood. We addressed this question in budding yeast, in which cells enter meiosis when starved. If nutrient-rich medium is added before a defined commitment point in mid-prometaphase I, they can return to mitosis. Cells in stages beyond the commitment point will finish meiosis, even with nutrient addition. Because checkpoints are signaling pathways known to couple cell-cycle processes with one another, we asked if checkpoints could ensure meiotic commitment. We find that two checkpoints with well-defined functions in mitosis, the DNA damage checkpoint and the spindle position checkpoint, have crucial roles in meiotic commitment. With nutrient-rich medium addition at stages beyond the commitment point, cells that are deficient in both checkpoints because they lack Rad53 and either Bub2, Bfa1, or Kin4 can return to mitotic growth and go on to form polyploid cells. The results demonstrate that the two checkpoints prevent cells from exiting meiosis in the presence of a mitosis-inducing signal. This study reveals a previously unknown function for the DNA damage checkpoint and the spindle position checkpoint in maintaining meiotic commitment.
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21
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Li S, Giardina DM, Siegal ML. Control of nongenetic heterogeneity in growth rate and stress tolerance of Saccharomyces cerevisiae by cyclic AMP-regulated transcription factors. PLoS Genet 2018; 14:e1007744. [PMID: 30388117 PMCID: PMC6241136 DOI: 10.1371/journal.pgen.1007744] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Revised: 11/14/2018] [Accepted: 10/05/2018] [Indexed: 01/01/2023] Open
Abstract
Genetically identical cells exhibit extensive phenotypic variation even under constant and benign conditions. This so-called nongenetic heterogeneity has important clinical implications: within tumors and microbial infections, cells show nongenetic heterogeneity in growth rate and in susceptibility to drugs or stress. The budding yeast, Saccharomyces cerevisiae, shows a similar form of nongenetic heterogeneity in which growth rate correlates positively with susceptibility to acute heat stress at the single-cell level. Using genetic and chemical perturbations, combined with high-throughput single-cell assays of yeast growth and gene expression, we show here that heterogeneity in intracellular cyclic AMP (cAMP) levels acting through the conserved Ras/cAMP/protein kinase A (PKA) pathway and its target transcription factors, Msn2 and Msn4, underlies this nongenetic heterogeneity. Lower levels of cAMP correspond to slower growth, as shown by direct comparison of cAMP concentration in subpopulations enriched for slower vs. faster growing cells. Concordantly, an endogenous reporter of this pathway’s activity correlates with growth in individual cells. The paralogs Msn2 and Msn4 differ in their roles in nongenetic heterogeneity in a way that demonstrates slow growth and stress tolerance are not inevitably linked. Heterogeneity in growth rate requires each, whereas only Msn2 is required for heterogeneity in expression of Tsl1, a subunit of trehalose synthase that contributes to acute-stress tolerance. Perturbing nongenetic heterogeneity by mutating genes in this pathway, or by culturing wild-type cells with the cell-permeable cAMP analog 8-bromo-cAMP or the PKA inhibitor H89, significantly impacts survival of acute heat stress. Perturbations that increase intracellular cAMP levels reduce the slower-growing subpopulation and increase susceptibility to acute heat stress, whereas PKA inhibition slows growth and decreases susceptibility to acute heat stress. Loss of Msn2 reduces, but does not completely eliminate, the correlation in individual cells between growth rate and acute-stress survival, suggesting a major role for the Msn2 pathway in nongenetic heterogeneity but also a residual benefit of slow growth. Our results shed light on the genetic control of nongenetic heterogeneity and suggest a possible means of defeating bet-hedging pathogens or tumor cells by making them more uniformly susceptible to treatment. Nongenetic heterogeneity exists when a trait differs among individuals that have identical genotypes and environments. A clonal population can maximize its long-term success in an uncertain environment by diversifying its phenotypes via nongenetic heterogeneity: the currently unfavored ones may become the favored ones when conditions change. Nongenetic heterogeneity has clinical relevance. For example, populations of tumor cells or infectious microbes show cell-to-cell differences in growth and in drug or stress tolerance. This heterogeneity hampers efficient treatment and can potentiate harmful evolution of a tumor or pathogen. We show that in budding yeast, heterogeneity in intracellular cyclic AMP levels acting through the conserved Ras/cAMP/protein kinase A (PKA) pathway and its target transcription factors, Msn2 and Msn4, underlies the nongenetic heterogeneity of both single-cell growth rate and acute heat-stress tolerance. Perturbations of this pathway significantly affect population survival upon acute heat stress. These results illuminate a mechanism of nongenetic heterogeneity and suggest the potential value of antitumor or antifungal treatment strategies that target nongenetic heterogeneity to render the tumor or pathogen population more uniformly susceptible to a second drug that aims to kill.
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Affiliation(s)
- Shuang Li
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America
| | - Daniella M. Giardina
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America
| | - Mark L. Siegal
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America
- * E-mail:
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22
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Nie ZW, Chen L, Jin QS, Gao YY, Wang T, Zhang X, Miao YL. Function and regulation mechanism of Chk1 during meiotic maturation in porcine oocytes. Cell Cycle 2017; 16:2220-2229. [PMID: 28933982 DOI: 10.1080/15384101.2017.1373221] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Abstract
Checkpoint 1 (Chk1), as an important member of DNA replication checkpoint and DNA damage response, has an important role during the G2/M stage of mitosis. In this study, we used porcine oocyte as a model to investigate the function of Chk1 during porcine oocyte maturation. Chk1 was expressed from germinal vesicle (GV) to metaphase II (MII) stages, mainly localized in the cytoplasm at GV stage and moved to the spindle after germinal vesicle breakdown (GVBD). Chk1 depletion not only induced oocytes to be arrested at MI stage with abnormal chromosomes arrangement, but also inhibited the degradation of Cyclin B1 and decreased the expression of Mitotic Arrest Deficient 2-Like 1 (Mad2L1), one of spindle assembly checkpoint (SAC) proteins, and cadherin 1 (Cdh1), one of coactivation for anaphase-promoting complex/cyclosome (APC/C). Moreover, Chk1 overexpression delayed GVBD. These results demonstrated that Chk1 facilitated the timely degradation of Cyclin B1 at anaphase I (AI) and maintained the expression of Mad2L1 and Cdh1, which ensured that all chromosomes were accurately located in a line, and then oocytes passed metaphase I (MI) and AI and exited from the first meiotic division successfully. In addition, we proved that Chk1 had not function on GVBD of porcine oocytes, which suggested that maturation of porcine oocytes did not need the DNA damage checkpoint, which was different from the mouse oocyte maturation.
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Affiliation(s)
- Zheng-Wen Nie
- a Institute of Stem Cell and Regenerative Biology, College of Animal Science and Technology & College of Veterinary Medicine, Huazhong Agricultural University , Wuhan , Hubel , China.,b Key Laboratory of Agricultural Animal Genetics , Breeding and Reproduction (Huazhong Agricultural University), Ministry of Education , Wuhan , Hubel , China
| | - Li Chen
- a Institute of Stem Cell and Regenerative Biology, College of Animal Science and Technology & College of Veterinary Medicine, Huazhong Agricultural University , Wuhan , Hubel , China.,b Key Laboratory of Agricultural Animal Genetics , Breeding and Reproduction (Huazhong Agricultural University), Ministry of Education , Wuhan , Hubel , China
| | - Qiu-Shi Jin
- a Institute of Stem Cell and Regenerative Biology, College of Animal Science and Technology & College of Veterinary Medicine, Huazhong Agricultural University , Wuhan , Hubel , China.,b Key Laboratory of Agricultural Animal Genetics , Breeding and Reproduction (Huazhong Agricultural University), Ministry of Education , Wuhan , Hubel , China
| | - Ying-Ying Gao
- a Institute of Stem Cell and Regenerative Biology, College of Animal Science and Technology & College of Veterinary Medicine, Huazhong Agricultural University , Wuhan , Hubel , China.,b Key Laboratory of Agricultural Animal Genetics , Breeding and Reproduction (Huazhong Agricultural University), Ministry of Education , Wuhan , Hubel , China
| | - Tao Wang
- a Institute of Stem Cell and Regenerative Biology, College of Animal Science and Technology & College of Veterinary Medicine, Huazhong Agricultural University , Wuhan , Hubel , China.,b Key Laboratory of Agricultural Animal Genetics , Breeding and Reproduction (Huazhong Agricultural University), Ministry of Education , Wuhan , Hubel , China
| | - Xia Zhang
- a Institute of Stem Cell and Regenerative Biology, College of Animal Science and Technology & College of Veterinary Medicine, Huazhong Agricultural University , Wuhan , Hubel , China.,c The Cooperative Innovation Center for Sustainable Pig Production , Huazhong Agricultural University , Wuhan , Hubel , China
| | - Yi-Liang Miao
- a Institute of Stem Cell and Regenerative Biology, College of Animal Science and Technology & College of Veterinary Medicine, Huazhong Agricultural University , Wuhan , Hubel , China.,b Key Laboratory of Agricultural Animal Genetics , Breeding and Reproduction (Huazhong Agricultural University), Ministry of Education , Wuhan , Hubel , China.,c The Cooperative Innovation Center for Sustainable Pig Production , Huazhong Agricultural University , Wuhan , Hubel , China
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23
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DNA damage signalling targets the kinetochore to promote chromatin mobility. Nat Cell Biol 2016; 18:281-90. [PMID: 26829389 DOI: 10.1038/ncb3308] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 01/04/2016] [Indexed: 12/11/2022]
Abstract
In budding yeast, chromatin mobility increases after a DNA double-strand break (DSB). This increase is dependent on Mec1, the yeast ATR kinase, but the targets responsible for this phenomenon are unknown. Here we report that the Mec1-dependent phosphorylation of Cep3, a kinetochore component, is required to stimulate chromatin mobility after DNA breaks. Cep3 phosphorylation counteracts a constraint on chromosome movement imposed by the attachment of centromeres to the spindle pole body. A second constraint, imposed by the tethering of telomeres to the nuclear periphery, is also relieved after chromosome breakage. A non-phosphorylatable Cep3 mutant that impairs DSB-induced chromatin mobility is proficient in DSB repair, suggesting that break-induced chromatin mobility may be dispensable for homology search. Rather, we propose that the relief of centromeric constraint promotes cell cycle arrest and faithful chromosome segregation through the engagement of the spindle assembly checkpoint.
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24
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Bokros M, Gravenmier C, Jin F, Richmond D, Wang Y. Fin1-PP1 Helps Clear Spindle Assembly Checkpoint Protein Bub1 from Kinetochores in Anaphase. Cell Rep 2016; 14:1074-1085. [PMID: 26832405 DOI: 10.1016/j.celrep.2016.01.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 11/13/2015] [Accepted: 12/29/2015] [Indexed: 01/04/2023] Open
Abstract
The spindle assembly checkpoint (SAC) monitors chromosome attachment defects, and the assembly of SAC proteins at kinetochores is essential for its activation, but the SAC disassembly process remains unknown. We found that deletion of a 14-3-3 protein, Bmh1, or hyperactivation of Cdc14 early anaphase release (FEAR) allows premature SAC silencing in budding yeast, which depends on a kinetochore protein Fin1 that forms a complex with protein phosphatase PP1. Previous works suggest that FEAR-dependent Fin1 dephosphorylation promotes Bmh1-Fin1 dissociation, which enables kinetochore recruitment of Fin1-PP1. We found persistent kinetochore association of SAC protein Bub1 in fin1Δ mutants after anaphase entry. Therefore, we revealed a mechanism that clears SAC proteins from kinetochores. After anaphase entry, FEAR activation promotes kinetochore enrichment of Fin1-PP1, resulting in SAC disassembly at kinetochores. This mechanism is required for efficient SAC silencing after SAC is challenged, and untimely Fin1-kinetochore association causes premature SAC silencing and chromosome missegregation.
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Affiliation(s)
- Michael Bokros
- Department of Biomedical Sciences, College of Medicine, Florida State University, 1115 West Call Street, Tallahassee, FL 32306-4300, USA
| | - Curtis Gravenmier
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306, USA
| | - Fengzhi Jin
- Department of Biomedical Sciences, College of Medicine, Florida State University, 1115 West Call Street, Tallahassee, FL 32306-4300, USA
| | - Daniel Richmond
- Department of Biomedical Sciences, College of Medicine, Florida State University, 1115 West Call Street, Tallahassee, FL 32306-4300, USA
| | - Yanchang Wang
- Department of Biomedical Sciences, College of Medicine, Florida State University, 1115 West Call Street, Tallahassee, FL 32306-4300, USA.
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25
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Palou G, Palou R, Zeng F, Vashisht AA, Wohlschlegel JA, Quintana DG. Three Different Pathways Prevent Chromosome Segregation in the Presence of DNA Damage or Replication Stress in Budding Yeast. PLoS Genet 2015; 11:e1005468. [PMID: 26332045 PMCID: PMC4558037 DOI: 10.1371/journal.pgen.1005468] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 07/27/2015] [Indexed: 11/18/2022] Open
Abstract
A surveillance mechanism, the S phase checkpoint, blocks progression into mitosis in response to DNA damage and replication stress. Segregation of damaged or incompletely replicated chromosomes results in genomic instability. In humans, the S phase checkpoint has been shown to constitute an anti-cancer barrier. Inhibition of mitotic cyclin dependent kinase (M-CDK) activity by Wee1 kinases is critical to block mitosis in some organisms. However, such mechanism is dispensable in the response to genotoxic stress in the model eukaryotic organism Saccharomyces cerevisiae. We show here that the Wee1 ortholog Swe1 does indeed inhibit M-CDK activity and chromosome segregation in response to genotoxic insults. Swe1 dispensability in budding yeast is the result of a redundant control of M-CDK activity by the checkpoint kinase Rad53. In addition, our results indicate that Swe1 is an effector of the checkpoint central kinase Mec1. When checkpoint control on M-CDK and on Pds1/securin stabilization are abrogated, cells undergo aberrant chromosome segregation. Genetic inheritance during cell proliferation requires chromosome duplication (replication) and segregation of the replicated chromosomes to the two daughter cells. In response to the presence of DNA damage, cells block chromosome segregation to avoid the inheritance of damaged, incompletely replicated chromosomes. Failure to do so results in loss of genomic integrity. Here we show that three different, redundant pathways are responsible for such control in budding yeast, a model eukaryotic organism. One of the pathways had been described before and blocks the separation of the replicated chromosomes. We show now that two additional pathways inhibit the essential pro-mitotic Cyclin Dependent Kinase (M-CDK) activity. One of them involves the conserved inhibition of M-CDK through tyrosine phosphorylation, which was puzzlingly dispensable in the response to challenged replication in budding yeast. We show that the reason for such dispensability is the existence of redundant control of M-CDK activity by Rad53. Rad53 is part of a surveillance mechanism termed the S phase checkpoint that detects and responds to replication insults. Such control mechanism has been proposed to constitute an anti-cancer barrier in human cells.
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Affiliation(s)
- Gloria Palou
- Department of Biochemistry and Molecular Biology, Biophysics Unit, School of Medicine, Universitat Autonoma de Barcelona, Bellaterra, Catalonia, Spain
| | - Roger Palou
- Department of Biochemistry and Molecular Biology, Biophysics Unit, School of Medicine, Universitat Autonoma de Barcelona, Bellaterra, Catalonia, Spain
| | - Fanli Zeng
- Department of Biochemistry and Molecular Biology, Biophysics Unit, School of Medicine, Universitat Autonoma de Barcelona, Bellaterra, Catalonia, Spain
| | - Ajay A. Vashisht
- Department of Biological Chemistry, University of California, Los Angeles, Los Angeles, California, United States of America
| | - James A. Wohlschlegel
- Department of Biological Chemistry, University of California, Los Angeles, Los Angeles, California, United States of America
| | - David G. Quintana
- Department of Biochemistry and Molecular Biology, Biophysics Unit, School of Medicine, Universitat Autonoma de Barcelona, Bellaterra, Catalonia, Spain
- * E-mail:
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Luo G, Kim J, Song K. The C-terminal domains of human neurofibromin and its budding yeast homologs Ira1 and Ira2 regulate the metaphase to anaphase transition. Cell Cycle 2015; 13:2780-9. [PMID: 25486365 PMCID: PMC4615033 DOI: 10.4161/15384101.2015.945870] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The human tumor suppressor neurofibromin contains a cysteine and serine-rich domain/Ras-GTPase activating protein domain (CSRD/RasGAP) and a C-terminal domain (CTD). Domain studies of neurofibromin suggest it has other functions in addition to being a RasGAP, but the mechanisms underlying its tumor suppressor activity are not well understood. The budding yeast Saccharomyces cerevisiae is a good model system for studying neurofibromin function because it possesses Ira1 and Ira2, which are homologous to human neurofibromin in both sequence and function. We found that overexpression of CTD or a neurofibromin CTD-homologous domain (CHD) of Ira1/2 in budding yeast delayed degradation of the securin protein Pds1, whereas overexpression of CSRD/RasGAP did not affect Pds1 degradation. We also found that when CTD or CHD was overexpressed, the number of cells in metaphase was higher than in the control. These results demonstrate that CTD and CHD function in the metaphase to anaphase transition. In addition, Δira1Δira2 cells bypassed mitotic arrest in response to spindle damage, indicating that Ira1 and Ira2 may be involved in the spindle assembly checkpoint (SAC). However, Δira1Δira2Δmad2 cells are more sensitive to spindle damage than Δmad2 or Δira1Δira2 cells are, suggesting that Ira1/2 and Mad2 function in different pathways. Overexpression of CTD but not CSRD/RasGAP partially rescued the hypersensitivity of Δira1Δira2Δmad2 cells to microtubule-destabilizing drugs, indicating a role for CTD in the SAC pathway. Taken together, independently of RasGAP activity, the C-terminal domains of neurofibromin, Ira1, and Ira2 regulate the metaphase to anaphase transition in a Mad2-independent fashion.
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Affiliation(s)
- Guangming Luo
- a Department of Biochemistry; College of Life Science and Biotechnology ; Yonsei University ; Seoul , Korea
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Roccuzzo M, Visintin C, Tili F, Visintin R. FEAR-mediated activation of Cdc14 is the limiting step for spindle elongation and anaphase progression. Nat Cell Biol 2015; 17:251-61. [PMID: 25706236 DOI: 10.1038/ncb3105] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Accepted: 01/09/2015] [Indexed: 01/01/2023]
Abstract
Cleavage of cohesins and cyclin-dependent kinase (CDK) inhibition are thought to be sufficient for triggering chromosome segregation. Here we identify an essential requirement for anaphase chromosome movement. We show that, at anaphase onset, the phosphatase Cdc14 and the polo-like kinase Cdc5 are redundantly required to drive spindle elongation. This role of Cdc14 is mediated by the FEAR network, a group of proteins that activates Cdc14 at anaphase onset, and we suggest that Cdc5 facilitates both Cdc14 activation and CDK inhibition. We further identify the kinesin-5 motor protein Cin8 as a key target of Cdc14. Indeed, Cin8 mutants lacking critical CDK phosphorylation sites suppress the requirement for Cdc14 and Cdc5 in anaphase spindle elongation. Our results indicate that cohesin dissolution and CDK inhibition per se are not sufficient to drive sister chromatid segregation but that the motor protein Cin8 must be activated to elongate the spindle.
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Affiliation(s)
- Michela Roccuzzo
- Department of Experimental Oncology, European Institute of Oncology, Milan 20139, Italy
| | - Clara Visintin
- Department of Experimental Oncology, European Institute of Oncology, Milan 20139, Italy
| | - Federico Tili
- Department of Experimental Oncology, European Institute of Oncology, Milan 20139, Italy
| | - Rosella Visintin
- Department of Experimental Oncology, European Institute of Oncology, Milan 20139, Italy
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28
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Lu D, Hsiao JY, Davey NE, Van Voorhis VA, Foster SA, Tang C, Morgan DO. Multiple mechanisms determine the order of APC/C substrate degradation in mitosis. ACTA ACUST UNITED AC 2014; 207:23-39. [PMID: 25287299 PMCID: PMC4195823 DOI: 10.1083/jcb.201402041] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
To ensure proper mitotic progression, robust ordering of the destruction of APC/CCdc20 substrates is driven by the integration of molecular mechanisms ranging from phosphorylation-dependent interaction with substrates to sensing of the status of the spindle assembly checkpoint. The ubiquitin protein ligase anaphase-promoting complex or cyclosome (APC/C) controls mitosis by promoting ordered degradation of securin, cyclins, and other proteins. The mechanisms underlying the timing of APC/C substrate degradation are poorly understood. We explored these mechanisms using quantitative fluorescence microscopy of GFP-tagged APC/CCdc20 substrates in living budding yeast cells. Degradation of the S cyclin, Clb5, begins early in mitosis, followed 6 min later by the degradation of securin and Dbf4. Anaphase begins when less than half of securin is degraded. The spindle assembly checkpoint delays the onset of Clb5 degradation but does not influence securin degradation. Early Clb5 degradation depends on its interaction with the Cdk1–Cks1 complex and the presence of a Cdc20-binding “ABBA motif” in its N-terminal region. The degradation of securin and Dbf4 is delayed by Cdk1-dependent phosphorylation near their Cdc20-binding sites. Thus, a remarkably diverse array of mechanisms generates robust ordering of APC/CCdc20 substrate destruction.
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Affiliation(s)
- Dan Lu
- Department of Physiology and Department of Biochemistry and Biophysics and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94158
| | - Jennifer Y Hsiao
- Department of Physiology and Department of Biochemistry and Biophysics and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94158
| | - Norman E Davey
- Department of Physiology and Department of Biochemistry and Biophysics and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94158
| | - Vanessa A Van Voorhis
- Department of Physiology and Department of Biochemistry and Biophysics and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94158
| | - Scott A Foster
- Department of Physiology and Department of Biochemistry and Biophysics and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94158
| | - Chao Tang
- Center for Quantitative Biology and Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China
| | - David O Morgan
- Department of Physiology and Department of Biochemistry and Biophysics and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94158
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Marston AL. Chromosome segregation in budding yeast: sister chromatid cohesion and related mechanisms. Genetics 2014; 196:31-63. [PMID: 24395824 PMCID: PMC3872193 DOI: 10.1534/genetics.112.145144] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Accepted: 09/18/2013] [Indexed: 12/28/2022] Open
Abstract
Studies on budding yeast have exposed the highly conserved mechanisms by which duplicated chromosomes are evenly distributed to daughter cells at the metaphase-anaphase transition. The establishment of proteinaceous bridges between sister chromatids, a function provided by a ring-shaped complex known as cohesin, is central to accurate segregation. It is the destruction of this cohesin that triggers the segregation of chromosomes following their proper attachment to microtubules. Since it is irreversible, this process must be tightly controlled and driven to completion. Furthermore, during meiosis, modifications must be put in place to allow the segregation of maternal and paternal chromosomes in the first division for gamete formation. Here, I review the pioneering work from budding yeast that has led to a molecular understanding of the establishment and destruction of cohesion.
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Affiliation(s)
- Adele L Marston
- The Wellcome Trust Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JR, United Kingdom
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30
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Rad53 downregulates mitotic gene transcription by inhibiting the transcriptional activator Ndd1. Mol Cell Biol 2013; 34:725-38. [PMID: 24324011 DOI: 10.1128/mcb.01056-13] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The 33 genes in the Saccharomyces cerevisiae mitotic CLB2 transcription cluster have been known to be downregulated by the DNA damage checkpoint for many years. Here, we show that this is mediated by the checkpoint kinase Rad53 and the dedicated transcriptional activator of the cluster, Ndd1. Ndd1 is phosphorylated in response to DNA damage, which blocks recruitment to promoters and leads to the transcriptional downregulation of the CLB2 cluster. Finally, we show that downregulation of Ndd1 is an essential function of Rad53, as a hypomorphic ndd1 allele rescues RAD53 deletion.
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31
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Zhang Y, Hunter T. Roles of Chk1 in cell biology and cancer therapy. Int J Cancer 2013; 134:1013-23. [PMID: 23613359 DOI: 10.1002/ijc.28226] [Citation(s) in RCA: 300] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Accepted: 04/11/2013] [Indexed: 01/05/2023]
Abstract
The evolutionally conserved DNA damage response (DDR) and cell cycle checkpoints preserve genome integrity. Central to these genome surveillance pathways is a protein kinase, Chk1. DNA damage induces activation of Chk1, which then transduces the checkpoint signal and facilitates cell cycle arrest and DNA damage repair. Significant progress has been made recently toward our understanding of Chk1 regulation and its implications in cancer etiology and therapy. Specifically, a model that involves both spatiotemporal and conformational changes of proteins has been proposed for Chk1 activation. Further, emerging evidence suggests that Chk1 does not appear to be a tumor suppressor; instead, it promotes tumor growth and may contribute to anticancer therapy resistance. Recent data from our laboratory suggest that activating, but not inhibiting, Chk1 in the absence of chemotherapy might represent an innovative approach to suppress tumor growth. These findings suggest unique regulation of Chk1 in cell biology and cancer etiology, pointing to novel strategies for targeting Chk1 in cancer therapy.
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Affiliation(s)
- Youwei Zhang
- Department of Pharmacology, Case Comprehensive Cancer Center, School of Medicine, Case Western Reserve University, Cleveland, OH
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32
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Postnikoff SDL, Harkness TAA. Mechanistic insights into aging, cell-cycle progression, and stress response. Front Physiol 2012; 3:183. [PMID: 22675309 PMCID: PMC3366476 DOI: 10.3389/fphys.2012.00183] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2012] [Accepted: 05/17/2012] [Indexed: 12/22/2022] Open
Abstract
The longevity of an organism depends on the health of its cells. Throughout life cells are exposed to numerous intrinsic and extrinsic stresses, such as free radicals, generated through mitochondrial electron transport, and ultraviolet irradiation. The cell has evolved numerous mechanisms to scavenge free radicals and repair damage induced by these insults. One mechanism employed by the yeast Saccharomycescerevisiae to combat stress utilizes the Anaphase Promoting Complex (APC), an essential multi-subunit ubiquitin-protein ligase structurally and functionally conserved from yeast to humans that controls progression through mitosis and G1. We have observed that yeast cells expressing compromised APC subunits are sensitive to multiple stresses and have shorter replicative and chronological lifespans. In a pathway that runs parallel to that regulated by the APC, members of the Forkhead box (Fox) transcription factor family also regulate stress responses. The yeast Fox orthologs Fkh1 and Fkh2 appear to drive the transcription of stress response factors and slow early G1 progression, while the APC seems to regulate chromatin structure, chromosome segregation, and resetting of the transcriptome in early G1. In contrast, under non-stress conditions, the Fkhs play a complex role in cell-cycle progression, partially through activation of the APC. Direct and indirect interactions between the APC and the yeast Fkhs appear to be pivotal for lifespan determination. Here we explore the potential for these interactions to be evolutionarily conserved as a mechanism to balance cell-cycle regulation with stress responses.
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Affiliation(s)
- S D L Postnikoff
- Department of Anatomy and Cell Biology, University of Saskatchewan Saskatoon, SK, Canada
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33
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Holt LJ. Regulatory modules: Coupling protein stability to phopshoregulation during cell division. FEBS Lett 2012; 586:2773-7. [PMID: 22664379 DOI: 10.1016/j.febslet.2012.05.045] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Revised: 05/23/2012] [Accepted: 05/23/2012] [Indexed: 11/28/2022]
Abstract
Multiple post-translational regulation systems regulate cell biology. Two key mechanisms that coordinate the myriad processes of cell replication are phosphorylation and ubiquitin-mediated degradation of proteins. Regulatory modules have evolved to integrate these two control systems at key decision points in the cell division cycle. These modules enable information to be processed with high fidelity by filtering noise, improving specificity, generating feedback loops, and optimizing spatiotemporal coordination of cellular processes. This review provides examples of these modules and considers the advantages of this signaling nexus.
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Affiliation(s)
- Liam J Holt
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
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34
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Witkin KL, Chong Y, Shao S, Webster MT, Lahiri S, Walters AD, Lee B, Koh JLY, Prinz WA, Andrews BJ, Cohen-Fix O. The budding yeast nuclear envelope adjacent to the nucleolus serves as a membrane sink during mitotic delay. Curr Biol 2012; 22:1128-33. [PMID: 22658600 DOI: 10.1016/j.cub.2012.04.022] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Revised: 03/17/2012] [Accepted: 04/12/2012] [Indexed: 11/17/2022]
Abstract
The mechanisms that dictate nuclear shape are largely unknown. Here we screened the budding yeast deletion collection for mutants with abnormal nuclear shape. A common phenotype was the appearance of a nuclear extension, particularly in mutants in DNA repair and chromosome segregation genes. Our data suggest that these mutations led to the abnormal nuclear morphology indirectly, by causing a checkpoint-induced cell-cycle delay. Indeed, delaying cells in mitosis by other means also led to the appearance of nuclear extensions, whereas inactivating the DNA damage checkpoint pathway in a DNA repair mutant reduced the fraction of cells with nuclear extensions. Formation of a nuclear extension was specific to a mitotic delay, because cells arrested in S or G2 had round nuclei. Moreover, the nuclear extension always coincided with the nucleolus, while the morphology of the DNA mass remained largely unchanged. Finally, we found that phospholipid synthesis continued unperturbed when cells delayed in mitosis, and inhibiting phospholipid synthesis abolished the formation of nuclear extensions. Our data suggest a mechanism that promotes nuclear envelope expansion during mitosis. When mitotic progression is delayed, cells sequester the added membrane to the nuclear envelope associated with the nucleolus, possibly to avoid disruption of intranuclear organization.
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Affiliation(s)
- Keren L Witkin
- Laboratory of Cell and Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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35
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Finn K, Lowndes NF, Grenon M. Eukaryotic DNA damage checkpoint activation in response to double-strand breaks. Cell Mol Life Sci 2012; 69:1447-73. [PMID: 22083606 PMCID: PMC11115150 DOI: 10.1007/s00018-011-0875-3] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Revised: 10/19/2011] [Accepted: 10/20/2011] [Indexed: 02/07/2023]
Abstract
Double-strand breaks (DSBs) are the most detrimental form of DNA damage. Failure to repair these cytotoxic lesions can result in genome rearrangements conducive to the development of many diseases, including cancer. The DNA damage response (DDR) ensures the rapid detection and repair of DSBs in order to maintain genome integrity. Central to the DDR are the DNA damage checkpoints. When activated by DNA damage, these sophisticated surveillance mechanisms induce transient cell cycle arrests, allowing sufficient time for DNA repair. Since the term "checkpoint" was coined over 20 years ago, our understanding of the molecular mechanisms governing the DNA damage checkpoint has advanced significantly. These pathways are highly conserved from yeast to humans. Thus, significant findings in yeast may be extrapolated to vertebrates, greatly facilitating the molecular dissection of these complex regulatory networks. This review focuses on the cellular response to DSBs in Saccharomyces cerevisiae, providing a comprehensive overview of how these signalling pathways function to orchestrate the cellular response to DNA damage and preserve genome stability in eukaryotic cells.
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Affiliation(s)
- Karen Finn
- Centre for Chromosome Biology, School of Natural Sciences, National University of Ireland Galway, Galway, Ireland
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36
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Searle JS, Wood MD, Kaur M, Tobin DV, Sanchez Y. Proteins in the nutrient-sensing and DNA damage checkpoint pathways cooperate to restrain mitotic progression following DNA damage. PLoS Genet 2011; 7:e1002176. [PMID: 21779180 PMCID: PMC3136438 DOI: 10.1371/journal.pgen.1002176] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2011] [Accepted: 05/23/2011] [Indexed: 11/18/2022] Open
Abstract
Checkpoint pathways regulate genomic integrity in part by blocking anaphase until all chromosomes have been completely replicated, repaired, and correctly aligned on the spindle. In Saccharomyces cerevisiae, DNA damage and mono-oriented or unattached kinetochores trigger checkpoint pathways that bifurcate to regulate both the metaphase to anaphase transition and mitotic exit. The sensor-associated kinase, Mec1, phosphorylates two downstream kinases, Chk1 and Rad53. Activation of Chk1 and Rad53 prevents anaphase and causes inhibition of the mitotic exit network. We have previously shown that the PKA pathway plays a role in blocking securin and Clb2 destruction following DNA damage. Here we show that the Mec1 DNA damage checkpoint regulates phosphorylation of the regulatory (R) subunit of PKA following DNA damage and that the phosphorylated R subunit has a role in restraining mitosis following DNA damage. In addition we found that proteins known to regulate PKA in response to nutrients and stress either by phosphorylation of the R subunit or regulating levels of cAMP are required for the role of PKA in the DNA damage checkpoint. Our data indicate that there is cross-talk between the DNA damage checkpoint and the proteins that integrate nutrient and stress signals to regulate PKA. Previous studies showed that phosphorylation of a subset of regulatory (R) subunits of the cAMP-dependent protein kinase (PKA) occurred under conditions that down-regulate global PKA activity, including growth on non-fermentable carbon sources. However, the role of the phosphorylation sites has not been elucidated. Addition of glucose to cells growing on a non-fermentable carbon source causes a transient increase of cAMP and PKA activity, which drives cells into S phase. A second peak in cAMP was proposed to restrain mitosis if the daughter cell had not reached an appropriate size. We identified a role for PKA in restraining mitosis following DNA damage. Here we provide evidence of cross-talk between the DNA damage checkpoint and PKA by phosphorylation of the R subunit. The R subunit phosphorylation sites and cAMP are necessary for the role of PKA following DNA damage. We propose that activation of PKA in response to DNA damage occurs in two steps: the phosphorylation of a subset of R subunits, probably to allow localized activation of these complexes, and cAMP to activate PKA. Our work suggests that the checkpoint and nutrient-sensing pathways share a signaling node to restrain mitosis following nutrient-induced rapid transition through the cell cycle and DNA damage.
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Affiliation(s)
- Jennifer S. Searle
- Department of Pharmacology and Toxicology, Norris Cotton Cancer Center, Dartmouth Medical School, Hanover, New Hampshire, United States of America
- Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America
| | - Matthew D. Wood
- Department of Pharmacology and Toxicology, Norris Cotton Cancer Center, Dartmouth Medical School, Hanover, New Hampshire, United States of America
| | - Mandeep Kaur
- Department of Pharmacology and Toxicology, Norris Cotton Cancer Center, Dartmouth Medical School, Hanover, New Hampshire, United States of America
| | - David V. Tobin
- Department of Pharmacology and Toxicology, Norris Cotton Cancer Center, Dartmouth Medical School, Hanover, New Hampshire, United States of America
| | - Yolanda Sanchez
- Department of Pharmacology and Toxicology, Norris Cotton Cancer Center, Dartmouth Medical School, Hanover, New Hampshire, United States of America
- * E-mail:
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37
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Wood MD, Sanchez Y. Deregulated Ras signaling compromises DNA damage checkpoint recovery in S. cerevisiae. Cell Cycle 2010; 9:3353-63. [PMID: 20716966 DOI: 10.4161/cc.9.16.12713] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The DNA damage checkpoint maintains genome stability by arresting the cell cycle and promoting DNA repair under genotoxic stress. Cells must downregulate the checkpoint signaling pathways in order to resume cell division after completing DNA repair. While the mechanisms of checkpoint activation have been well-characterized, the process of checkpoint recovery, and the signals regulating it, has only recently been investigated. We have identified a new role for the Ras signaling pathway as a regulator of DNA damage checkpoint recovery. Here we report that in budding yeast, deletion of the IRA1 and IRA2 genes encoding negative regulators of Ras prevents cellular recovery from a DNA damage induced arrest. The checkpoint kinase Rad53 is dephosphorylated in an IRA-deficient strain, indicating that recovery failure is not caused by constitutive checkpoint pathway activation. The ira1Δ ira2Δ recovery defect requires the checkpoint kinase Chk1 and the cAMP-dependent protein kinase (PKA) catalytic subunit Tpk2. Furthermore, PKA phosphorylation sites on the anaphase promoting complex specificity factor Cdc20 are required for the recovery defect, indicating a link between the recovery defect and PKA regulation of mitosis. This work identifies a new signaling pathway that can regulate DNA damage checkpoint recovery and implicates the Ras signaling pathway as an important regulator of mitotic events.
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Affiliation(s)
- Matthew D Wood
- Department of Pharmacology and Toxicology, Norris Cotton Cancer Center, Dartmouth Medical School, Hanover, NH, USA
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38
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Checkpoint kinase 1 modulates sensitivity to cisplatin after spindle checkpoint activation in SW620 cells. Int J Biochem Cell Biol 2010; 42:318-28. [DOI: 10.1016/j.biocel.2009.11.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2009] [Revised: 10/30/2009] [Accepted: 11/10/2009] [Indexed: 01/17/2023]
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39
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Zhang T, Nirantar S, Lim HH, Sinha I, Surana U. DNA damage checkpoint maintains CDH1 in an active state to inhibit anaphase progression. Dev Cell 2009; 17:541-51. [PMID: 19853567 DOI: 10.1016/j.devcel.2009.09.006] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2008] [Revised: 02/20/2009] [Accepted: 09/18/2009] [Indexed: 01/11/2023]
Abstract
DNA damage checkpoint prevents segregation of damaged chromosomes by imposing cell-cycle arrest. In budding yeast, Mec1, Chk1, and Rad53 (homologous to human ATM/ATR, Chk1, and Chk2 kinases, respectively) are among the main effectors of this pathway. The DNA damage checkpoint is thought to inhibit chromosome segregation by preventing separase-mediated cleavage of cohesins. Here, we describe a regulatory network that prevents segregation of damaged chromosomes by restricting spindle elongation and acts in parallel with inhibition of cohesin cleavage. This control circuit involves Rad53, polo kinase, the anaphase-promoting complex activator Cdh1, and the bimC kinesin family proteins Cin8 and Kip1. The inhibition of polo kinase by Rad53-dependent phosphorylation prevents it from inactivating Cdh1. As a result, Cdh1 remains in a partially active state and limits Cin8 and Kip1 accumulation, thereby restraining spindle elongation. Hence, the DNA damage checkpoint suppresses both cohesin cleavage and spindle elongation to preserve chromosome stability.
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Affiliation(s)
- Tao Zhang
- Institute of Molecular and Cell Biology, A*STAR (Agency for Science, Technology and Research) 61, Biopolis Drive, Proteos, Singapore 138673
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40
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Alberghina L, Coccetti P, Orlandi I. Systems biology of the cell cycle of Saccharomyces cerevisiae: From network mining to system-level properties. Biotechnol Adv 2009; 27:960-978. [PMID: 19465107 DOI: 10.1016/j.biotechadv.2009.05.021] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Following a brief description of the operational procedures of systems biology (SB), the cell cycle of budding yeast is discussed as a successful example of a top-down SB analysis. After the reconstruction of the steps that have led to the identification of a sizer plus timer network in the G1 to S transition, it is shown that basic functions of the cell cycle (the setting of the critical cell size and the accuracy of DNA replication) are system-level properties, detected only by integrating molecular analysis with modelling and simulation of their underlying networks. A detailed network structure of a second relevant regulatory step of the cell cycle, the exit from mitosis, derived from extensive data mining, is constructed and discussed. To reach a quantitative understanding of how nutrients control, through signalling, metabolism and transcription, cell growth and cycle is a very relevant aim of SB. Since we know that about 900 gene products are required for cell cycle execution and control in budding yeast, it is quite clear that a purely systematic approach would require too much time. Therefore lines for a modular SB approach, which prioritises molecular and computational investigations for faster cell cycle understanding, are proposed. The relevance of the insight coming from the cell cycle SB studies in developing a new framework for tackling very complex biological processes, such as cancer and aging, is discussed.
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Affiliation(s)
- Lilia Alberghina
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, P.zza della Scienza 2, 20126 Milano, Italy.
| | - Paola Coccetti
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, P.zza della Scienza 2, 20126 Milano, Italy
| | - Ivan Orlandi
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, P.zza della Scienza 2, 20126 Milano, Italy
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41
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Rahal R, Amon A. Mitotic CDKs control the metaphase-anaphase transition and trigger spindle elongation. Genes Dev 2008; 22:1534-48. [PMID: 18519644 DOI: 10.1101/gad.1638308] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Mitotic cyclin-dependent kinases (CDKs) control entry into mitosis, but their role during mitotic progression is less well understood. Here we characterize the functions of CDK activity associated with the mitotic cyclins Clb1, Clb2, and Clb3. We show that Clb-CDKs are important for the activation of the ubiquitin ligase Anaphase-Promoting Complex/Cyclosome (APC/C)-Cdc20 that triggers the metaphase-anaphase transition. Furthermore, we define an essential role for Clb-CDK activity in anaphase spindle elongation. Thus, mitotic CDKs serve not only to initiate M phase, but are also needed continuously throughout mitosis to trigger key mitotic events such as APC/C activation and anaphase spindle elongation.
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Affiliation(s)
- Rami Rahal
- Center for Cancer Research, Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 USA
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42
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Kilkenny ML, Doré AS, Roe SM, Nestoras K, Ho JC, Watts FZ, Pearl LH. Structural and functional analysis of the Crb2-BRCT2 domain reveals distinct roles in checkpoint signaling and DNA damage repair. Genes Dev 2008; 22:2034-47. [PMID: 18676809 PMCID: PMC2492745 DOI: 10.1101/gad.472808] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Accepted: 06/04/2008] [Indexed: 12/25/2022]
Abstract
Schizosaccharomyces pombe Crb2 is a checkpoint mediator required for the cellular response to DNA damage. Like human 53BP1 and Saccharomyces cerevisiae Rad9 it contains Tudor(2) and BRCT(2) domains. Crb2-Tudor(2) domain interacts with methylated H4K20 and is required for recruitment to DNA dsDNA breaks. The BRCT(2) domain is required for dimerization, but its precise role in DNA damage repair and checkpoint signaling is unclear. The crystal structure of the Crb2-BRCT(2) domain, alone and in complex with a phosphorylated H2A.1 peptide, reveals the structural basis for dimerization and direct interaction with gamma-H2A.1 in ionizing radiation-induced foci (IRIF). Mutational analysis in vitro confirms the functional role of key residues and allows the generation of mutants in which dimerization and phosphopeptide binding are separately disrupted. Phenotypic analysis of these in vivo reveals distinct roles in the DNA damage response. Dimerization mutants are genotoxin sensitive and defective in checkpoint signaling, Chk1 phosphorylation, and Crb2 IRIF formation, while phosphopeptide-binding mutants are only slightly sensitive to IR, have extended checkpoint delays, phosphorylate Chk1, and form Crb2 IRIF. However, disrupting phosphopeptide binding slows formation of ssDNA-binding protein (Rpa1/Rad11) foci and reduces levels of Rad22(Rad52) recombination foci, indicating a DNA repair defect.
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Affiliation(s)
- Mairi L. Kilkenny
- CR-UK DNA Repair Enzymes Group, Section of Structural Biology, The Institute of Cancer Research, Chelsea, London SW3 6JB, United Kingdon
| | - Andrew S. Doré
- CR-UK DNA Repair Enzymes Group, Section of Structural Biology, The Institute of Cancer Research, Chelsea, London SW3 6JB, United Kingdon
| | - S. Mark Roe
- CR-UK DNA Repair Enzymes Group, Section of Structural Biology, The Institute of Cancer Research, Chelsea, London SW3 6JB, United Kingdon
| | - Konstantinos Nestoras
- Genome Damage and Stability Centre, University of Sussex, Falmer, Brighton, East Sussex BN1 9RQ, United Kingdom
| | - Jenny C.Y. Ho
- Genome Damage and Stability Centre, University of Sussex, Falmer, Brighton, East Sussex BN1 9RQ, United Kingdom
| | - Felicity Z. Watts
- Genome Damage and Stability Centre, University of Sussex, Falmer, Brighton, East Sussex BN1 9RQ, United Kingdom
| | - Laurence H. Pearl
- CR-UK DNA Repair Enzymes Group, Section of Structural Biology, The Institute of Cancer Research, Chelsea, London SW3 6JB, United Kingdon
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43
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Tong Y, Ben-Shlomo A, Zhou C, Wawrowsky K, Melmed S. Pituitary tumor transforming gene 1 regulates Aurora kinase A activity. Oncogene 2008; 27:6385-95. [PMID: 18663361 DOI: 10.1038/onc.2008.234] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Pituitary tumor transforming gene 1 (PTTG1), a transforming gene highly expressed in several cancers, is a mammalian securin protein regulating both G1/S and G2/M phases. Using protein array screening, we showed PTTG1 interacting with Aurora kinase A (Aurora-A), and confirmed the interaction using co-immunoprecipitation, His-tagged pull-down assays and intracellular immunofluorescence colocalization. PTTG1 transfection into HCT116 cells prevented Aurora-A T288 autophosphorylation, inhibited phosphorylation of the histone H3 Aurora-A substrate and resulted in abnormally condensed chromatin. PTTG1-null cell proliferation was more sensitive to Aurora-A knock down and to Aurora kinase Inhibitor III treatment. The results indicate that PTTG1 and Aurora-A interact to regulate cellular responses to anti-neoplastic drugs. PTTG1 knockdown is therefore a potential approach to improve the efficacy of tumor Aurora kinase inhibitors.
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Affiliation(s)
- Y Tong
- Department of Medicine, Cedars-Sinai Research Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA 90048, USA
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44
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Heidinger-Pauli JM, Unal E, Guacci V, Koshland D. The kleisin subunit of cohesin dictates damage-induced cohesion. Mol Cell 2008; 31:47-56. [PMID: 18614046 DOI: 10.1016/j.molcel.2008.06.005] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2007] [Revised: 06/16/2008] [Accepted: 06/19/2008] [Indexed: 12/28/2022]
Abstract
Cohesin, the protein complex that mediates sister chromatid cohesion, is required for faithful chromosome segregation and efficient repair of double-strand breaks (DSBs). Cohesion generation is normally restricted to S phase. However, in G2/M, a DSB activates cohesion generation near the DSB and genome-wide. Here, using budding yeast, we show that DSB-induced cohesion occurs when cohesin contains the kleisin subunit, Mcd1 (Scc1), but not when Mcd1 is replaced by its meiotic isoform, Rec8. We exploit this divergence to demonstrate that serine 83 of Mcd1 and the Chk1 kinase are critical determinants for DSB-induced cohesion. We propose that a DSB in G2/M activates Mec1 (ATR), which in turn stimulates Chk1-dependent phosphorylation of Mcd1 at serine 83. Serine 83 phosphorylation promotes chromatin-bound cohesin to become cohesive.
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Affiliation(s)
- Jill M Heidinger-Pauli
- Department of Embryology, Howard Hughes Medical Institute, Carnegie Institution, 3520 San Martin Drive, Baltimore, MD 21218, USA
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45
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Holt LJ, Krutchinsky AN, Morgan DO. Positive feedback sharpens the anaphase switch. Nature 2008; 454:353-7. [PMID: 18552837 DOI: 10.1038/nature07050] [Citation(s) in RCA: 158] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2008] [Accepted: 04/24/2008] [Indexed: 12/22/2022]
Abstract
At the onset of anaphase, sister-chromatid cohesion is dissolved abruptly and irreversibly, ensuring that all chromosome pairs disjoin almost simultaneously. The regulatory mechanisms that generate this switch-like behaviour are unclear. Anaphase is initiated when a ubiquitin ligase, the anaphase-promoting complex (APC), triggers the destruction of securin, thereby allowing separase, a protease, to disrupt sister-chromatid cohesion. Here we demonstrate that the cyclin-dependent kinase 1 (Cdk1)-dependent phosphorylation of securin near its destruction-box motif inhibits securin ubiquitination by the APC. The phosphatase Cdc14 reverses securin phosphorylation, thereby increasing the rate of securin ubiquitination. Because separase is known to activate Cdc14 (refs 5 and 6), our results support the existence of a positive feedback loop that increases the abruptness of anaphase. Consistent with this model, we show that mutations that disrupt securin phosphoregulation decrease the synchrony of chromosome segregation. Our results also suggest that coupling securin degradation with changes in Cdk1 and Cdc14 activities helps coordinate the initiation of sister-chromatid separation with changes in spindle dynamics.
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Affiliation(s)
- Liam J Holt
- Department of Physiology, University of California, San Francisco, California 94158, USA
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46
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Limón-Mortés MC, Mora-Santos M, Espina A, Pintor-Toro JA, López-Román A, Tortolero M, Romero F. UV-induced degradation of securin is mediated by SKP1-CUL1-beta TrCP E3 ubiquitin ligase. J Cell Sci 2008; 121:1825-31. [PMID: 18460583 DOI: 10.1242/jcs.020552] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Securin is a chaperone protein with bifunctional properties. It binds to separase to inhibit premature sister chromatid separation until the onset of anaphase, and it also takes part in cell-cycle arrest after UV irradiation. At metaphase-to-anaphase transition, securin is targeted for proteasomal destruction by the anaphase-promoting complex or cyclosome (APC/C), allowing activation of separase. However, although securin is reported to undergo proteasome-dependent degradation after UV irradiation, the ubiquitin ligase responsible for securin ubiquitylation has not been well characterized. In this study, we show that UV radiation induced a marked reduction of securin in both the nucleus and cytoplasm. Moreover, we show that GSK-3beta inhibitors prevent securin degradation, and that CUL1 and betaTrCP are involved in this depletion. We also confirmed that SKP1-CUL1-betaTrCP (SCF(betaTrCP)) ubiquitylates securin in vivo, and identified a conserved and unconventional betaTrCP recognition motif (DDAYPE) in the securin primary amino acid sequence of humans, nonhuman primates and rodents. Furthermore, downregulation of betaTrCP caused an accumulation of securin in non-irradiated cells. We conclude that SCF(betaTrCP) is the E3 ubiquitin ligase responsible for securin degradation after UV irradiation, and that it is involved in securin turnover in nonstressed cells.
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47
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Kim EM, Burke DJ. DNA damage activates the SAC in an ATM/ATR-dependent manner, independently of the kinetochore. PLoS Genet 2008; 4:e1000015. [PMID: 18454191 PMCID: PMC2265443 DOI: 10.1371/journal.pgen.1000015] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2007] [Accepted: 01/31/2008] [Indexed: 12/21/2022] Open
Abstract
The DNA damage checkpoint and the spindle assembly checkpoint (SAC) are two important regulatory mechanisms that respond to different lesions. The DNA damage checkpoint detects DNA damage, initiates protein kinase cascades, and inhibits the cell cycle. The SAC relies on kinetochore-dependent assembly of protein complexes to inhibit mitosis when chromosomes are detached from the spindle. The two checkpoints are thought to function independently. Here we show that yeast cells lacking the DNA damage checkpoint arrest prior to anaphase in response to low doses of the DNA damaging agent methyl methane sulfonate (MMS). The arrest requires the SAC proteins Mad1, Mad2, Mad3, Bub1, and Bub3 and works through Cdc20 and Pds1 but unlike the normal SAC, does not require a functional kinetochore. Mec1 (ATR) and Tel1 (ATM) are also required, independently of Chk1 and Rad53, suggesting that Mec1 and Tel1 inhibit anaphase in response to DNA damage by utilizing SAC proteins. Our results demonstrate cross-talk between the two checkpoints and suggest that assembling inhibitory complexes of SAC proteins at unattached kinetochores is not obligatory for their inhibitory activity. Furthermore, our results suggest that there are novel, important targets of ATM and ATR for cell cycle regulation.
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Affiliation(s)
- Eun Mi Kim
- Department of Biochemistry and Molecular Genetics, University of Virginia Medical Center, Charlottesville, Virginia, United States of America
| | - Daniel J. Burke
- Department of Biochemistry and Molecular Genetics, University of Virginia Medical Center, Charlottesville, Virginia, United States of America
- * E-mail:
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48
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Rodier G, Coulombe P, Tanguay PL, Boutonnet C, Meloche S. Phosphorylation of Skp2 regulated by CDK2 and Cdc14B protects it from degradation by APC(Cdh1) in G1 phase. EMBO J 2008; 27:679-91. [PMID: 18239684 DOI: 10.1038/emboj.2008.6] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2007] [Accepted: 01/08/2008] [Indexed: 12/26/2022] Open
Abstract
The p27(Kip1) ubiquitin ligase receptor Skp2 is often overexpressed in human tumours and displays oncogenic properties. The activity of SCF(Skp2) is regulated by the APC(Cdh1), which targets Skp2 for degradation. Here we show that Skp2 phosphorylation on Ser64/Ser72 positively regulates its function in vivo. Phosphorylation of Ser64, and to a lesser extent Ser72, stabilizes Skp2 by interfering with its association with Cdh1, without affecting intrinsic ligase activity. Cyclin-dependent kinase (CDK)2-mediated phosphorylation of Skp2 on Ser64 allows its expression in mid-G1 phase, even in the presence of active APC(Cdh1). Reciprocally, dephosphorylation of Skp2 by the mitotic phosphatase Cdc14B at the M --> G1 transition promotes its degradation by APC(Cdh1). Importantly, lowering the levels of Cdc14B accelerates cell cycle progression from mitosis to S phase in an Skp2-dependent manner, demonstrating epistatic relationship of Cdc14B and Skp2 in the regulation of G1 length. Thus, our results reveal that reversible phosphorylation plays a key role in the timing of Skp2 expression in the cell cycle.
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Affiliation(s)
- Geneviève Rodier
- Institut de Recherche en Immunologie et Cancérologie, Université de Montréal, Montreal, Quebec, Canada
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49
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Abstract
Cdc20 is an essential cell-cycle regulator required for the completion of mitosis in organisms from yeast to man and contains at its C terminus a WD40 repeat domain that mediates protein-protein interactions. In mitosis, Cdc20 binds to and activates the ubiquitin ligase activity of a large molecular machine called the anaphase-promoting complex/cyclosome (APC/C) and enables the ubiquitination and degradation of securin and cyclin B, thus promoting the onset of anaphase and mitotic exit. APC/C(Cdc20) is temporally and spatially regulated during the somatic and embryonic cell cycle by numerous mechanisms, including the spindle checkpoint and the cytostatic factor (CSF). Therefore, Cdc20 serves as an integrator of multiple intracellular signaling cascades that regulate progression through mitosis. This review summarizes recent progress toward the understanding of the functions of Cdc20, the mechanisms by which it activates APC/C, and its regulation by phosphorylation and by association with its binding proteins.
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Affiliation(s)
- Hongtao Yu
- Department of Pharmacology, The University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390-9041, USA.
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50
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Liang F, Wang Y. DNA damage checkpoints inhibit mitotic exit by two different mechanisms. Mol Cell Biol 2007; 27:5067-78. [PMID: 17485442 PMCID: PMC1951953 DOI: 10.1128/mcb.00095-07] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cyclin-dependent kinase (CDK) governs cell cycle progression, and its kinase activity fluctuates during the cell cycle. Mitotic exit pathways are responsible for the inactivation of CDK after chromosome segregation by promoting the release of a nucleolus-sequestered phosphatase, Cdc14, which antagonizes CDK. In the budding yeast Saccharomyces cerevisiae, mitotic exit is controlled by the FEAR (for "Cdc-fourteen early anaphase release") and mitotic exit network (MEN) pathways. In response to DNA damage, two branches of the DNA damage checkpoint, Chk1 and Rad53, are activated in budding yeast to prevent anaphase entry and mitotic exit, allowing cells more time to repair damaged DNA. Here we present evidence indicating that yeast cells negatively regulate mitotic exit through two distinct pathways in response to DNA damage. Rad53 prevents mitotic exit by inhibiting the MEN pathway, whereas the Chk1 pathway prevents FEAR pathway-dependent Cdc14 release in the presence of DNA damage. In contrast to previous data, the Rad53 pathway negatively regulates MEN independently of Cdc5, a Polo-like kinase essential for mitotic exit. Instead, a defective Rad53 pathway alleviates the inhibition of MEN by Bfa1.
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Affiliation(s)
- Fengshan Liang
- Department of Biomedical Sciences, College of Medicine, Florida State University, 1115 West Call Street, Tallahassee, FL 32306, USA
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