51
|
Wloka C, Vallen EA, Thé L, Fang X, Oh Y, Bi E. Immobile myosin-II plays a scaffolding role during cytokinesis in budding yeast. J Cell Biol 2013; 200:271-86. [PMID: 23358243 PMCID: PMC3563683 DOI: 10.1083/jcb.201208030] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2012] [Accepted: 12/28/2012] [Indexed: 01/13/2023] Open
Abstract
Core components of cytokinesis are conserved from yeast to human, but how these components are assembled into a robust machine that drives cytokinesis remains poorly understood. In this paper, we show by fluorescence recovery after photobleaching analysis that Myo1, the sole myosin-II in budding yeast, was mobile at the division site before anaphase and became immobilized shortly before cytokinesis. This immobility was independent of actin filaments or the motor domain of Myo1 but required a small region in the Myo1 tail that is thought to be involved in higher-order assembly. As expected, proteins involved in actin ring assembly (tropomyosin and formin) and membrane trafficking (myosin-V and exocyst) were dynamic during cytokinesis. Strikingly, proteins involved in septum formation (the chitin synthase Chs2) and/or its coordination with the actomyosin ring (essential light chain, IQGAP, F-BAR, etc.) displayed Myo1-dependent immobility during cytokinesis, suggesting that Myo1 plays a scaffolding role in the assembly of a cytokinesis machine.
Collapse
Affiliation(s)
- Carsten Wloka
- Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104
- Institut für Biologie, Freie Universität Berlin, 14195 Berlin, Germany
| | | | - Lydia Thé
- Department of Biology, Swarthmore College, Swarthmore, PA 19081
| | - Xiaodong Fang
- Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104
| | - Younghoon Oh
- Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104
| | - Erfei Bi
- Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104
| |
Collapse
|
52
|
|
53
|
Lockshon D, Olsen CP, Brett CL, Chertov A, Merz AJ, Lorenz DA, Van Gilst MR, Kennedy BK. Rho signaling participates in membrane fluidity homeostasis. PLoS One 2012; 7:e45049. [PMID: 23071506 PMCID: PMC3465289 DOI: 10.1371/journal.pone.0045049] [Citation(s) in RCA: 31] [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: 05/11/2012] [Accepted: 08/14/2012] [Indexed: 01/03/2023] Open
Abstract
Preservation of both the integrity and fluidity of biological membranes is a critical cellular homeostatic function. Signaling pathways that govern lipid bilayer fluidity have long been known in bacteria, yet no such pathways have been identified in eukaryotes. Here we identify mutants of the yeast Saccharomyces cerevisiae whose growth is differentially influenced by its two principal unsaturated fatty acids, oleic and palmitoleic acid. Strains deficient in the core components of the cell wall integrity (CWI) pathway, a MAP kinase pathway dependent on both Pkc1 (yeast's sole protein kinase C) and Rho1 (the yeast RhoA-like small GTPase), were among those inhibited by palmitoleate yet stimulated by oleate. A single GEF (Tus1) and a single GAP (Sac7) of Rho1 were also identified, neither of which participate in the CWI pathway. In contrast, key components of the CWI pathway, such as Rom2, Bem2 and Rlm1, failed to influence fatty acid sensitivity. The differential influence of palmitoleate and oleate on growth of key mutants correlated with changes in membrane fluidity measured by fluorescence anisotropy of TMA-DPH, a plasma membrane-bound dye. This work provides the first evidence for the existence of a signaling pathway that enables eukaryotic cells to control membrane fluidity, a requirement for division, differentiation and environmental adaptation.
Collapse
Affiliation(s)
- Daniel Lockshon
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
- Buck Institute for Age Research, Novato, California, United States of America
| | - Carissa Perez Olsen
- Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
| | - Christopher L. Brett
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - Andrei Chertov
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - Alexey J. Merz
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
| | - Daniel A. Lorenz
- Sonoma State University, Rohnert Park, California, United States of America
| | - Marc R. Van Gilst
- Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
| | - Brian K. Kennedy
- Department of Biochemistry, University of Washington, Seattle, Washington, United States of America
- Buck Institute for Age Research, Novato, California, United States of America
| |
Collapse
|
54
|
α-Synuclein disrupts stress signaling by inhibiting polo-like kinase Cdc5/Plk2. Proc Natl Acad Sci U S A 2012; 109:16119-24. [PMID: 22988096 DOI: 10.1073/pnas.1206286109] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Parkinson disease (PD) results from the slow, progressive loss of dopaminergic neurons in the substantia nigra. Alterations in α-synuclein (aSyn), such as mutations or multiplications of the gene, are thought to trigger this degeneration. Here, we show that aSyn disrupts mitogen-activated protein kinase (MAPK)-controlled stress signaling in yeast and human cells, which results in inefficient cell protective responses and cell death. aSyn is a substrate of the yeast (and human) polo-like kinase Cdc5 (Plk2), and elevated levels of aSyn prevent Cdc5 from maintaining a normal level of GTP-bound Rho1, which is an essential GTPase that regulates stress signaling. The nine N-terminal amino acids of aSyn are essential for the interaction with polo-like kinases. The results support a unique mechanism of PD pathology.
Collapse
|
55
|
Actin depolymerization drives actomyosin ring contraction during budding yeast cytokinesis. Dev Cell 2012; 22:1247-60. [PMID: 22698284 DOI: 10.1016/j.devcel.2012.04.015] [Citation(s) in RCA: 140] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2011] [Revised: 01/27/2012] [Accepted: 04/19/2012] [Indexed: 01/21/2023]
Abstract
Actin filaments and myosin II are evolutionarily conserved force-generating components of the contractile ring during cytokinesis. Here we show that in budding yeast, actin filament depolymerization plays a major role in actomyosin ring constriction. Cofilin mutation or chemically stabilizing actin filaments attenuate actomyosin ring constriction. Deletion of myosin II motor domain or the myosin regulatory light chain reduced the contraction rate and also the rate of actin depolymerization in the ring. We constructed a quantitative microscopic model of actomyosin ring constriction via filament sliding driven by both actin depolymerization and myosin II motor activity. Model simulations based on experimental measurements support the notion that actin depolymerization is the predominant mechanism for ring constriction. The model predicts invariability of total contraction time regardless of the initial ring size, as originally reported for C. elegans embryonic cells. This prediction was validated in yeast cells of different sizes due to different ploidies.
Collapse
|
56
|
Buttery SM, Kono K, Stokasimov E, Pellman D. Regulation of the formin Bnr1 by septins anda MARK/Par1-family septin-associated kinase. Mol Biol Cell 2012; 23:4041-53. [PMID: 22918953 PMCID: PMC3469519 DOI: 10.1091/mbc.e12-05-0395] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The septin-associated kinase Gin4 is required for the localization and activation of Bnr1, and the septin Shs1 is essential for Bnr1 activation. The loss of Gin4 or Shs1 phenocopies the loss of Bnr1; these defects are suppressed by constitutive activation of Bnr1. The data reveal novel regulatory links between the actin and septin cytoskeletons. Formin-family proteins promote the assembly of linear actin filaments and are required to generate cellular actin structures, such as actin stress fibers and the cytokinetic actomyosin contractile ring. Many formin proteins are regulated by an autoinhibition mechanism involving intramolecular binding of a Diaphanous inhibitory domain and a Diaphanous autoregulatory domain. However, the activation mechanism for these Diaphanous-related formins (DRFs) is not completely understood. Although small GTPases play an important role in relieving autoinhibition, other factors likely contribute. Here we describe a requirement for the septin Shs1 and the septin-associated kinase Gin4 for the localization and in vivo activity of the budding yeast DRF Bnr1. In budding yeast strains in which the other formin, Bni1, is conditionally inactivated, the loss of Gin4 or Shs1 results in the loss of actin cables and cell death, similar to the loss of Bnr1. The defects in these strains can be suppressed by constitutive activation of Bnr1. Gin4 is involved in both the localization and activation of Bnr1, whereas the septin Shs1 is required for Bnr1 activation but not its localization. Gin4 promotes the activity of Bnr1 independently of the Gin4 kinase activity, and Gin4 lacking its kinase domain binds to the critical localization region of Bnr1. These data reveal novel regulatory links between the actin and septin cytoskeletons.
Collapse
Affiliation(s)
- Shawnna M Buttery
- Howard Hughes Medical Institute, Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | | | | | | |
Collapse
|
57
|
Sanchez-Diaz A, Nkosi PJ, Murray S, Labib K. The Mitotic Exit Network and Cdc14 phosphatase initiate cytokinesis by counteracting CDK phosphorylations and blocking polarised growth. EMBO J 2012; 31:3620-34. [PMID: 22872148 DOI: 10.1038/emboj.2012.224] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Accepted: 07/17/2012] [Indexed: 01/27/2023] Open
Abstract
Polarisation of the actin cytoskeleton must cease during cytokinesis, to support efficient assembly and contraction of the actomyosin ring at the site of cell division, but the underlying mechanisms are still understood poorly in most species. In budding yeast, the Mitotic Exit Network (MEN) releases Cdc14 phosphatase from the nucleolus during anaphase, leading to the inactivation of mitotic forms of cyclin-dependent kinase (CDK) and the onset of septation, before G1-CDK can be reactivated and drive re-polarisation of the actin cytoskeleton to a new bud. Here, we show that premature inactivation of mitotic CDK, before release of Cdc14, allows G1-CDK to divert the actin cytoskeleton away from the actomyosin ring to a new site of polarised growth, thereby delaying progression through cytokinesis. Our data indicate that cells normally avoid this problem via the MEN-dependent release of Cdc14, which counteracts all classes of CDK-mediated phosphorylations during cytokinesis and blocks polarised growth. The dephosphorylation of CDK targets is therefore central to the mechanism by which the MEN and Cdc14 initiate cytokinesis and block polarised growth during late mitosis.
Collapse
Affiliation(s)
- Alberto Sanchez-Diaz
- Paterson Institute for Cancer Research, University of Manchester, Manchester, UK
| | | | | | | |
Collapse
|
58
|
The kinomes of apicomplexan parasites. Microbes Infect 2012; 14:796-810. [DOI: 10.1016/j.micinf.2012.04.007] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Revised: 04/11/2012] [Accepted: 04/11/2012] [Indexed: 11/21/2022]
|
59
|
Wloka C, Bi E. Mechanisms of cytokinesis in budding yeast. Cytoskeleton (Hoboken) 2012; 69:710-26. [DOI: 10.1002/cm.21046] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2012] [Accepted: 06/15/2012] [Indexed: 01/22/2023]
|
60
|
Richthammer C, Enseleit M, Sanchez-Leon E, März S, Heilig Y, Riquelme M, Seiler S. RHO1 and RHO2 share partially overlapping functions in the regulation of cell wall integrity and hyphal polarity in Neurospora crassa. Mol Microbiol 2012; 85:716-33. [DOI: 10.1111/j.1365-2958.2012.08133.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
|
61
|
Han DP, Zhu QL, Cui JT, Wang PX, Qu S, Cao QF, Zong YP, Feng B, Zheng MH, Lu AG. Polo-like kinase 1 is overexpressed in colorectal cancer and participates in the migration and invasion of colorectal cancer cells. Med Sci Monit 2012; 18:BR237-46. [PMID: 22648245 PMCID: PMC3560731 DOI: 10.12659/msm.882900] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2011] [Accepted: 11/13/2011] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Polo-like kinase 1 (PLK1) is an important molecule in proliferation of many human cancers. The aim of study is to clarify the expression patterns and potential function of PLK1 in colorectal cancers. MATERIAL/METHODS Fifty-six colorectal cancers samples were collected and arranged onto a tissue array and the expression of PLK1 were detected by immunohistochemistry and correlated with clinico-pathological characteristics and expression of PCNA. Expression of PLK1 in 9 colorectal cancer cells lines was investigated by RT-PCR and Western blot, then SW1116 cells lines were treated with PLK1 siRNA and the efficiency was examined by Western blot. Transwell test was applied to detect the migration and invasion capability of cancer cells by counting the number of cells passing through the membranes. Cell proliferation and apoptosis were examined by Cell Counting Kit-8 (CCK-8) and Annexin-V Kit. RESULTS PLK1 was positively expressed in 73.2% (41/56) of colorectal cancers tissues, but in only 3.6% (2/56) of normal tissues, and was associated with Duke's stage (P<0.01), tumor size (P<0.01), invasion extent (P<0.05) and lymphatic metastasis (P<0.01). The expression of PLK1 was correlated with expression of PCNA (R=0.553, P<0.01). PLK1 was inhibited in SW1116 cells by treating with PLK1 siRNA oligos, which resulted in a decreased number of cells passing through the membrane as compared with control groups (P<0.01) at 24 hours after transfection. Cell proliferation was inhibited from 48 hours after transfection, while cells apoptosis was induced from 72 hours after transfection. CONCLUSIONS PLK1 could be a progression marker for colorectal cancer patients and PLK1 depletion can inhibit migration and invasion capability of colorectal cancer cells SW1116, suggesting that PLK1 might be involved in metastasis and invasion of colorectal cancer. Therapeutic strategies targeting PLK1 may be a new approach to colorectal cancer.
Collapse
Affiliation(s)
| | | | | | | | | | | | | | | | | | - Ai-guo Lu
- Lu Ai-Guo, Department of General Surgery, Shanghai Ruijin Hospital, Shanghai Minimally Invasive Surgery Center, 197 Ruijin Er Rd, Shanghai 200025, China, e-mail:
| |
Collapse
|
62
|
Bi E, Park HO. Cell polarization and cytokinesis in budding yeast. Genetics 2012; 191:347-87. [PMID: 22701052 PMCID: PMC3374305 DOI: 10.1534/genetics.111.132886] [Citation(s) in RCA: 217] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2011] [Accepted: 11/04/2011] [Indexed: 12/26/2022] Open
Abstract
Asymmetric cell division, which includes cell polarization and cytokinesis, is essential for generating cell diversity during development. The budding yeast Saccharomyces cerevisiae reproduces by asymmetric cell division, and has thus served as an attractive model for unraveling the general principles of eukaryotic cell polarization and cytokinesis. Polarity development requires G-protein signaling, cytoskeletal polarization, and exocytosis, whereas cytokinesis requires concerted actions of a contractile actomyosin ring and targeted membrane deposition. In this chapter, we discuss the mechanics and spatial control of polarity development and cytokinesis, emphasizing the key concepts, mechanisms, and emerging questions in the field.
Collapse
Affiliation(s)
- Erfei Bi
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6058, USA.
| | | |
Collapse
|
63
|
Regulation of cell wall biogenesis in Saccharomyces cerevisiae: the cell wall integrity signaling pathway. Genetics 2012; 189:1145-75. [PMID: 22174182 DOI: 10.1534/genetics.111.128264] [Citation(s) in RCA: 617] [Impact Index Per Article: 51.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The yeast cell wall is a strong, but elastic, structure that is essential not only for the maintenance of cell shape and integrity, but also for progression through the cell cycle. During growth and morphogenesis, and in response to environmental challenges, the cell wall is remodeled in a highly regulated and polarized manner, a process that is principally under the control of the cell wall integrity (CWI) signaling pathway. This pathway transmits wall stress signals from the cell surface to the Rho1 GTPase, which mobilizes a physiologic response through a variety of effectors. Activation of CWI signaling regulates the production of various carbohydrate polymers of the cell wall, as well as their polarized delivery to the site of cell wall remodeling. This review article centers on CWI signaling in Saccharomyces cerevisiae through the cell cycle and in response to cell wall stress. The interface of this signaling pathway with other pathways that contribute to the maintenance of cell wall integrity is also discussed.
Collapse
|
64
|
Krause SA, Cundell MJ, Poon PP, McGhie J, Johnston GC, Price C, Gray JV. Functional specialisation of yeast Rho1 GTP exchange factors. J Cell Sci 2012; 125:2721-31. [PMID: 22344253 DOI: 10.1242/jcs.100685] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Rho GTPases are regulated in complex spatiotemporal patterns that might be dependent, in part at least, on the multiplicity of their GTP exchange factors (GEFs). Here, we examine the extent of and basis for functional specialisation of the Rom2 and Tus1 GEFs that activate the yeast Rho1 GTPase, the orthologue of mammalian RhoA. First, we find that these GEFs selectively activate different Rho1-effector branches. Second, the synthetic genetic networks around ROM2 and TUS1 confirm very different global in vivo roles for these GEFs. Third, the GEFs are not functionally interchangeable: Tus1 cannot replace the essential role of Rom2, even when overexpressed. Fourth, we find that Rom2 and Tus1 localise differently: Rom2 to the growing bud surface and to the bud neck at cytokinesis; Tus1 only to the bud neck, but in a distinct pattern. Finally, we find that these GEFs are dependent on different protein co-factors: Rom2 function and localisation is largely dependent on Ack1, a SEL1-domain-containing protein; Tus1 function and localisation is largely dependent on the Tus1-interacting protein Ypl066w (which we name Rgl1). We have revealed a surprising level of diversity among the Rho1 GEFs that contributes another level of complexity to the spatiotemporal control of Rho1.
Collapse
Affiliation(s)
- Sue Ann Krause
- School of Life Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | | | | | | | | | | | | |
Collapse
|
65
|
Ye Y, Lee IJ, Runge KW, Wu JQ. Roles of putative Rho-GEF Gef2 in division-site positioning and contractile-ring function in fission yeast cytokinesis. Mol Biol Cell 2012; 23:1181-95. [PMID: 22298427 PMCID: PMC3315812 DOI: 10.1091/mbc.e11-09-0800] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
How Rho-GEFs and Rho GTPases regulate division-site selection during cytokinesis in fission yeast is unknown. The Rho-GEF Gef2 interacts with the anillin Mid1 to regulate contractile-ring positioning and assembly in coordination with the polo kinase Plo1. In addition, Gef2 is involved in contractile-ring stability and disassembly. Cytokinesis is crucial for integrating genome inheritance and cell functions. In multicellular organisms, Rho-guanine nucleotide exchange factors (GEFs) and Rho GTPases are key regulators of division-plane specification and contractile-ring formation during cytokinesis, but how they regulate early steps of cytokinesis in fission yeast remains largely unknown. Here we show that putative Rho-GEF Gef2 and Polo kinase Plo1 coordinate to control the medial cortical localization and function of anillin-related protein Mid1. The division-site positioning defects of gef2∆ plo1-ts18 double mutant can be partially rescued by increasing Mid1 levels. We find that Gef2 physically interacts with the Mid1 N-terminus and modulates Mid1 cortical binding. Gef2 localization to cortical nodes and the contractile ring depends on its last 145 residues, and the DBL-homology domain is important for its function in cytokinesis. Our data suggest the interaction between Rho-GEFs and anillins is an important step in the signaling pathways during cytokinesis. In addition, Gef2 also regulates contractile-ring function late in cytokinesis and may negatively regulate the septation initiation network. Collectively, we propose that Gef2 facilitates and stabilizes Mid1 binding to the medial cortex, where the localized Mid1 specifies the division site and induces contractile-ring assembly.
Collapse
Affiliation(s)
- Yanfang Ye
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210, USA
| | | | | | | |
Collapse
|
66
|
Abstract
Studies of the processes leading to the construction of a bud and its separation from the mother cell in Saccharomyces cerevisiae have provided foundational paradigms for the mechanisms of polarity establishment, cytoskeletal organization, and cytokinesis. Here we review our current understanding of how these morphogenetic events occur and how they are controlled by the cell-cycle-regulatory cyclin-CDK system. In addition, defects in morphogenesis provide signals that feed back on the cyclin-CDK system, and we review what is known regarding regulation of cell-cycle progression in response to such defects, primarily acting through the kinase Swe1p. The bidirectional communication between morphogenesis and the cell cycle is crucial for successful proliferation, and its study has illuminated many elegant and often unexpected regulatory mechanisms. Despite considerable progress, however, many of the most puzzling mysteries in this field remain to be resolved.
Collapse
Affiliation(s)
- Audrey S. Howell
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710
| | - Daniel J. Lew
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710
| |
Collapse
|
67
|
Simpson-Lavy KJ, Brandeis M. Phosphorylation of Cdc5 regulates its accumulation. Cell Div 2011; 6:23. [PMID: 22204387 PMCID: PMC3269358 DOI: 10.1186/1747-1028-6-23] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Accepted: 12/28/2011] [Indexed: 12/31/2022] Open
Abstract
Background Cdc5 (polo kinase/Plk1) is a highly conserved key regulator of the S. cerevisiae cell cycle from S-phase until cytokinesis. However, much of the regulatory mechanisms that govern Cdc5 remain to be determined. Cdc5 is phosphorylated on up to 10 sites during mitosis. In this study, we investigated the function of phosphorylation site T23, the only full consensus Cdk1 (Cdc28) phosphorylation site present. Findings Cdc5T23A introduces a degron that reduces its cellular amount to undetectable levels, which are nevertheless sufficient for normal cell proliferation. The degron acts in cis and is reversed by N-terminal GFP-tagging. Cdk1 kinase activity is required to maintain Cdc5 levels during G2. This, Cdk1 inhibited, Cdc5 degradation is APC/CCdh1 independent and requires new protein synthesis. Cdc5T23E is hyperactive, and reduces the levels of Cdc5 (in trans) and drastically reduces Clb2 levels. Conclusions Phosphorylation of Cdc5 by Cdk1 is required to maintain Cdc5 levels during G2. However, phosphorylation of T23 (probably by Cdk1) caps Cdc5 and other CLB2 cluster protein accumulation, preventing potential protein toxicity, which may arise from their overexpression or from APC/CCdh1 inactivation.
Collapse
Affiliation(s)
- Kobi J Simpson-Lavy
- The Department of Genetics, The Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
| | | |
Collapse
|
68
|
Independent modulation of the kinase and polo-box activities of Cdc5 protein unravels unique roles in the maintenance of genome stability. Proc Natl Acad Sci U S A 2011; 108:E914-23. [PMID: 21987786 DOI: 10.1073/pnas.1106448108] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Polo-like kinases (PLKs) are evolutionarily conserved kinases essential for cell cycle regulation. These kinases are characterized by the presence of a C-terminal phosphopeptide-interaction domain, the polo-box domain (PBD). How the functional domains of PLKs work together to promote cell division is not understood. To address this, we performed a genetic screen to identify mutations that independently modulate the kinase and PBD activities of yeast PLK/Cdc5. This screen identified a mutagenic hotspot in the F-helix region of Cdc5 kinase domain that allows one to control kinase activity in vivo. These mutations can be systematically engineered into other major eukaryotic cell cycle kinases to similarly regulate their activity in live cells. Here, using this approach, we show that the kinase activity of Cdc5 can promote the execution of several stages of mitosis independently of PBD activity. In particular, we observe that the activation of Cdc14 and execution of mitotic exit are uniquely sensitive to the modulation of Cdc5 kinase activity. In contrast, PBD-defective mutants are capable of completing mitosis but are unable to maintain spindle pole body integrity. Consistent with this defect, PBD-deficient cells progressively double the size of their genome and ultimately lose genome integrity. Collectively, these results highlight the specific contributions of Cdc5 functional domains to cell division and reveal unexpected mechanisms controlling spindle pole body behavior and genome stability.
Collapse
|
69
|
Tzeng YW, Huang JN, Schuyler SC, Wu CH, Juang YL. Functions of the mitotic B-type cyclins CLB1, CLB2, and CLB3 at mitotic exit antagonized by the CDC14 phosphatase. Fungal Genet Biol 2011; 48:966-78. [DOI: 10.1016/j.fgb.2011.07.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Revised: 07/05/2011] [Accepted: 07/06/2011] [Indexed: 01/11/2023]
|
70
|
Meitinger F, Boehm ME, Hofmann A, Hub B, Zentgraf H, Lehmann WD, Pereira G. Phosphorylation-dependent regulation of the F-BAR protein Hof1 during cytokinesis. Genes Dev 2011; 25:875-88. [PMID: 21498574 DOI: 10.1101/gad.622411] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Spatial and timely coordination of cytokinesis is crucial for the maintenance of organelle inheritance and genome integrity. The mitotic exit network (MEN) pathway controls both the timely initiation of mitotic exit and cytokinesis in budding yeast. Here we identified the conserved F-BAR protein Hof1 as a substrate of the MEN kinase complex Dbf2-Mob1 during cytokinesis. We show that polo-like kinase Cdc5 first phosphorylates Hof1 to allow subsequent phosphorylation by Dbf2-Mob1. This releases Hof1 from the septin ring and facilitates Hof1 binding to the medial actomyosin ring (AMR), where Hof1 promotes AMR contraction and membrane ingression. Domain structure analysis established that the central, unstructured, region of Hof1, named the ring localization sequence (RLS), is sufficient to mediate Hof1's binding to the medial ring in a cell cycle-dependent manner. Genetic and functional data support a model in which Dbf2-Mob1 regulates Hof1 by inducing domain rearrangements, leading to the exposure of the Hof1 RLS domain during telophase.
Collapse
Affiliation(s)
- Franz Meitinger
- Molecular Biology of Centrosomes and Cilia Unit, DKFZ-ZMBH Alliance, German Cancer Research Center, 69120 Heidelberg, Germany
| | | | | | | | | | | | | |
Collapse
|
71
|
The Rho1 GTPase acts together with a vacuolar glutathione S-conjugate transporter to protect yeast cells from oxidative stress. Genetics 2011; 188:859-70. [PMID: 21625004 DOI: 10.1534/genetics.111.130724] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Maintenance of redox homeostasis is critical for the survival of all aerobic organisms. In the budding yeast Saccharomyces cerevisiae, as in other eukaryotes, reactive oxygen species (ROS) are generated during metabolism and upon exposure to environmental stresses. The abnormal production of ROS triggers defense mechanisms to avoid the deleterious consequence of ROS accumulation. Here, we show that the Rho1 GTPase is necessary to confer resistance to oxidants in budding yeast. Temperature-sensitive rho1 mutants (rho1(ts)) are hypersensitive to oxidants and exhibit high accumulation of ROS even at a semipermissive temperature. Rho1 associates with Ycf1, a vacuolar glutathione S-conjugate transporter, which is important for heavy metal detoxification in yeast. Rho1 and Ycf1 exhibit a two-hybrid interaction with each other and form a bimolecular fluorescent complex on the vacuolar membrane. A fluorescent-based complementation assay suggests that the GTP-bound Rho1 associates with Ycf1 and that their interaction is enhanced upon exposure to hydrogen peroxide. The rho1(ts) mutants also exhibit hypersensitivity to cadmium, while cells carrying a deletion of YCF1 or mutations in a component of the Pkc1-MAP kinase pathway exhibit little or minor sensitivity to oxidants. We thus propose that Rho1 protects yeast cells from oxidative stress by regulating multiple downstream targets including Ycf1. Since both Rho1 and Ycf1 belong to highly conserved families of proteins, similar mechanisms may exist in other eukaryotes.
Collapse
|
72
|
Bohnert KA, Gould KL. On the cutting edge: post-translational modifications in cytokinesis. Trends Cell Biol 2011; 21:283-92. [PMID: 21349716 DOI: 10.1016/j.tcb.2011.01.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Revised: 01/25/2011] [Accepted: 01/26/2011] [Indexed: 11/24/2022]
Abstract
Cytokinesis represents the final stage in the cell cycle, in which two daughter cells, each with their complement of the duplicated genome, physically separate. At the core of this process sits highly conserved machinery responsible for specifying the plane of division, building a contractile apparatus and ultimately cleaving cells in two. Although the 'parts list' of contributing proteins has been well described, mechanisms by which these parts are spatially and temporally regulated are only beginning to be understood. With advancements in biochemical and proteomic analyses, recent work has uncovered multiple new roles for post-translational modifications in the regulation of cytokinesis. Here, we review these latest findings and interpret our current understanding of cytokinesis in light of relevant modifications.
Collapse
Affiliation(s)
- K Adam Bohnert
- Howard Hughes Medical Institute and Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | | |
Collapse
|
73
|
Bloom J, Cristea IM, Procko AL, Lubkov V, Chait BT, Snyder M, Cross FR. Global analysis of Cdc14 phosphatase reveals diverse roles in mitotic processes. J Biol Chem 2010; 286:5434-45. [PMID: 21127052 DOI: 10.1074/jbc.m110.205054] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Cdc14 phosphatase regulates multiple events during anaphase and is essential for mitotic exit in budding yeast. Cdc14 is regulated in both a spatial and temporal manner. It is sequestered in the nucleolus for most of the cell cycle by the nucleolar protein Net1 and is released into the nucleus and cytoplasm during anaphase. To identify novel binding partners of Cdc14, we used affinity purification of Cdc14 and mass spectrometric analysis of interacting proteins from strains in which Cdc14 localization or catalytic activity was altered. To alter Cdc14 localization, we used a strain deleted for NET1, which causes full release of Cdc14 from the nucleolus. To alter Cdc14 activity, we generated mutations in the active site of Cdc14 (C283S or D253A), which allow binding of substrates, but not dephosphorylation, by Cdc14. Using this strategy, we identified new interactors of Cdc14, including multiple proteins involved in mitotic events. A subset of these proteins displayed increased affinity for catalytically inactive mutants of Cdc14 compared with the wild-type version, suggesting they are likely substrates of Cdc14. We have also shown that several of the novel Cdc14-interacting proteins, including Kar9 (a protein that orients the mitotic spindle) and Bni1 and Bnr1 (formins that nucleate actin cables and may be important for actomyosin ring contraction) are specifically dephosphorylated by Cdc14 in vitro and in vivo. Our findings suggest the dephosphorylation of the formins may be important for their observed localization change during exit from mitosis and indicate that Cdc14 targets proteins involved in wide-ranging mitotic events.
Collapse
Affiliation(s)
- Joanna Bloom
- The Rockefeller University, New York, New York 10065, USA
| | | | | | | | | | | | | |
Collapse
|
74
|
Negishi T, Ohya Y. The cell wall integrity checkpoint: coordination between cell wall synthesis and the cell cycle. Yeast 2010; 27:513-9. [PMID: 20583321 DOI: 10.1002/yea.1795] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The cell wall is an essential cellular component for the survival of fungi. The cell wall of the budding yeast Saccharomyces cerevisiae undergoes remodelling during the cell cycle. Evidence is accumulating that there are regulatory mechanisms that link cell wall remodelling and cell cycle progression. Here, we review one such mechanism, known as the 'cell wall integrity checkpoint', which functions to control cell cycle progression in response to cell wall perturbation.
Collapse
Affiliation(s)
- Takahiro Negishi
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Chiba, Japan
| | | |
Collapse
|
75
|
Chen YC, Weinreich M. Dbf4 regulates the Cdc5 Polo-like kinase through a distinct non-canonical binding interaction. J Biol Chem 2010; 285:41244-54. [PMID: 21036905 DOI: 10.1074/jbc.m110.155242] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Cdc7-Dbf4 is a conserved, two-subunit kinase required for initiating eukaryotic DNA replication. Recent studies have shown that Cdc7-Dbf4 also regulates the mitotic exit network (MEN) and monopolar homolog orientation in meiosis I (Matos, J., Lipp, J. J., Bogdanova, A., Guillot, S., Okaz, E., Junqueira, M., Shevchenko, A., and Zachariae, W. (2008) Cell 135, 662-678 and Miller, C. T., Gabrielse, C., Chen, Y. C., and Weinreich, M. (2009) PLoS Genet. 5, e1000498). Both activities likely involve a Cdc7-Dbf4 interaction with Cdc5, the single Polo-like kinase in budding yeast. We previously showed that Dbf4 binds the Cdc5 polo-box domain (PBD) via an ∼40-residue N-terminal sequence, which lacks a PBD consensus binding site (S(pS/pT)(P/X)), and that Dbf4 inhibits Cdc5 function during mitosis. Here we identify a non-consensus PBD binding site within Dbf4 and demonstrate that the PBD-Dbf4 interaction occurs via a distinct PBD surface from that used to bind phosphoproteins. Genetic and biochemical analysis of multiple dbf4 mutants indicate that Dbf4 inhibits Cdc5 function through direct binding. Surprisingly, mutation of invariant Cdc5 residues required for binding phosphorylated substrates has little effect on yeast viability or growth rate. Instead, cdc5 mutants defective for binding phosphoproteins exhibit enhanced resistance to microtubule disruption and an increased rate of spindle elongation. This study, therefore, details the molecular nature of a new type of PBD binding and reveals that Cdc5 targeting to phosphorylated substrates likely regulates spindle dynamics.
Collapse
Affiliation(s)
- Ying-Chou Chen
- Van Andel Research Institute, Grand Rapids, Michigan 49503, USA
| | | |
Collapse
|
76
|
Cytokinesis and cancer: Polo loves ROCK'n' Rho(A). J Genet Genomics 2010; 37:159-72. [PMID: 20347825 DOI: 10.1016/s1673-8527(09)60034-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2009] [Revised: 02/08/2010] [Accepted: 02/09/2010] [Indexed: 12/11/2022]
Abstract
Cytokinesis is the last step of the M (mitosis) phase, yet it is crucial for the faithful division of one cell into two. Cytokinesis failure is often associated with cancer. Cytokinesis can be morphologically divided into four steps: cleavage furrow initiation, cleavage furrow ingression, midbody formation and abscission. Molecular studies have revealed that RhoA as well as its regulators and effectors are important players to ensure a successful cytokinesis. At the same time, Polo-like kinase 1 (Plk1) is an important kinase that can target many substrates and carry out different functions during mitosis, including cytokinesis. Recent studies are beginning to unveil a closer tie between Plk1 and RhoA networks. More specifically, Plk1 phosphorylates the centralspindlin complex Cyk4 and MKLP1/CHO1, thus recruiting RhoA guanine nucleotide-exchange factor (GEF) Ect2 through its phosphopeptide-binding BRCT domains. Ect2 itself can be phosphorylated by Plk1 in vitro. Plk1 can also phosphorylate another GEF MyoGEF to regulate RhoA activity. Once activated, RhoA-GTP will activate downstream effectors, including ROCK1 and ROCK2. ROCK2 is among the proteins that associate with Plk1 Polo-binding domain (PBD) in a large proteomic screen, and Plk1 can phosphorylate ROCK2 in vitro. We review current understandings of the interplay between Plk1, RhoA proteins and other proteins (e.g., NudC, MKLP2, PRC1, CEP55) involved in cytokinesis, with particular emphasis of its clinical implications in cancer.
Collapse
|
77
|
Meitinger F, Petrova B, Lombardi IM, Bertazzi DT, Hub B, Zentgraf H, Pereira G. Targeted localization of Inn1, Cyk3 and Chs2 by the mitotic-exit network regulates cytokinesis in budding yeast. J Cell Sci 2010; 123:1851-61. [PMID: 20442249 DOI: 10.1242/jcs.063891] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The mitotic-exit network (MEN) is a signaling pathway that is essential for the coordination of mitotic exit and cytokinesis. Whereas the role of the MEN in mitotic exit is well established, the molecular mechanisms by which MEN components regulate cytokinesis remain poorly understood. Here, we show that the MEN controls components involved in septum formation, including Inn1, Cyk3 and Chs2. MEN-deficient mutants, forced to exit mitosis as a result of Cdk1 inactivation, show defects in targeting Cyk3 and Inn1 to the bud-neck region. In addition, we found that the chitin synthase Chs2 did not efficiently localize at the bud neck in the absence of MEN activity. Ultrastructural analysis of the bud neck revealed that low MEN activity led to unilateral, uncoordinated extension of the primary and secondary septa. This defect was partially suppressed by increased levels of Cyk3. We therefore propose that the MEN directly controls cytokinesis via targeting of Inn1, Cyk3 and Chs2 to the bud neck.
Collapse
Affiliation(s)
- Franz Meitinger
- German Cancer Research Centre, DKFZ-ZMBH Alliance, Molecular Biology of Centrosomes and Cilia Unit, Im Neuenheimer Feld 581, 69120 Heidelberg, Germany
| | | | | | | | | | | | | |
Collapse
|
78
|
Heng YW, Koh CG. Actin cytoskeleton dynamics and the cell division cycle. Int J Biochem Cell Biol 2010; 42:1622-33. [PMID: 20412868 DOI: 10.1016/j.biocel.2010.04.007] [Citation(s) in RCA: 195] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2010] [Revised: 04/12/2010] [Accepted: 04/14/2010] [Indexed: 11/29/2022]
Abstract
The network of actin filaments is one of the crucial cytoskeletal structures contributing to the morphological framework of a cell and which participates in the dynamic regulation of cellular functions. In adherent cell types, cells adhere to the substratum during interphase and spread to assume their characteristic shape supported by the actin cytoskeleton. This actin cytoskeleton is reorganized during mitosis to form rounded cells with increased cortical rigidity. The actin cytoskeleton is re-established after mitosis, allowing cells to regain their extended shape and attachment to the substratum. The modulation of such drastic changes in cell shape in coordination with cell cycle progression suggests a tight regulatory interaction between cytoskeleton signalling, cell-cell/cell-matrix adhesions and mitotic events. Here, we review the contribution of the actin cytoskeleton to cell cycle progression with an emphasis on the effectors responsible for the regulation of the actin cytoskeleton and integration of their activities with the cell cycle machinery.
Collapse
Affiliation(s)
- Yi-Wen Heng
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | | |
Collapse
|
79
|
Abstract
Eukaryotic cells display a wide range of morphologies important for cellular function and development. A particular cell shape is made via the generation of asymmetry in the organization of cytoskeletal elements, usually leading to actin localization at sites of growth. The Rho family of GTPases is present in all eukaryotic cells, from yeast to mammals, and their role as key regulators in the signalling pathways that control actin organization and morphogenetic processes is well known. In the present review we will discuss the role of Rho GTPases as regulators of yeasts' polarized growth, their mechanism of activation and signalling pathways in Saccharomyces cerevisiae and Schizosaccharomyces pombe. These two model yeasts have been very useful in the study of the molecular mechanisms responsible for cell polarity. As in other organisms with cell walls, yeast's polarized growth is closely related to cell-wall biosynthesis, and Rho GTPases are critical modulators of this process. They provide the co-ordinated regulation of cell-wall biosynthetic enzymes and actin organization required to maintain cell integrity during vegetative growth.
Collapse
|
80
|
ABC transporters in Saccharomyces cerevisiae and their interactors: new technology advances the biology of the ABCC (MRP) subfamily. Microbiol Mol Biol Rev 2010; 73:577-93. [PMID: 19946134 DOI: 10.1128/mmbr.00020-09] [Citation(s) in RCA: 141] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Members of the ATP-binding cassette (ABC) transporter superfamily exist in bacteria, fungi, plants, and animals and play key roles in the efflux of xenobiotic compounds, physiological substrates, and toxic intracellular metabolites. Based on sequence relatedness, mammalian ABC proteins have been divided into seven subfamilies, ABC subfamily A (ABCA) to ABCG. This review focuses on recent advances in our understanding of ABC transporters in the model organism Saccharomyces cerevisiae. We propose a revised unified nomenclature for the six yeast ABC subfamilies to reflect the current mammalian designations ABCA to ABCG. In addition, we specifically review the well-studied yeast ABCC subfamily (formerly designated the MRP/CFTR subfamily), which includes six members (Ycf1p, Bpt1p, Ybt1p/Bat1p, Nft1p, Vmr1p, and Yor1p). We focus on Ycf1p, the best-characterized yeast ABCC transporter. Ycf1p is located in the vacuolar membrane in yeast and functions in a manner analogous to that of the human multidrug resistance-related protein (MRP1, also called ABCC1), mediating the transport of glutathione-conjugated toxic compounds. We review what is known about Ycf1p substrates, trafficking, processing, posttranslational modifications, regulation, and interactors. Finally, we discuss a powerful new yeast two-hybrid technology called integrated membrane yeast two-hybrid (iMYTH) technology, which was designed to identify interactors of membrane proteins. iMYTH technology has successfully identified novel interactors of Ycf1p and promises to be an invaluable tool in future efforts to comprehensively define the yeast ABC interactome.
Collapse
|
81
|
Chesarone MA, DuPage AG, Goode BL. Unleashing formins to remodel the actin and microtubule cytoskeletons. Nat Rev Mol Cell Biol 2009; 11:62-74. [PMID: 19997130 DOI: 10.1038/nrm2816] [Citation(s) in RCA: 394] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Formins are highly conserved proteins that have essential roles in remodelling the actin and microtubule cytoskeletons to influence eukaryotic cell shape and behaviour. Recent work has identified numerous cellular factors that locally recruit, activate or inactivate formins to bridle and unleash their potent effects on actin nucleation and elongation. The effects of formins on microtubules have also begun to be described, which places formins in a prime position to coordinate actin and microtubule dynamics. The emerging complexity in the mechanisms governing formins mirrors the wide range of essential functions that they perform in cell motility, cell division and cell and tissue morphogenesis.
Collapse
Affiliation(s)
- Melissa A Chesarone
- Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, Massachusetts 02454, USA
| | | | | |
Collapse
|
82
|
Chen SF, Juang YL, Chou WK, Lai JM, Huang CYF, Kao CY, Wang FS. Inferring a transcriptional regulatory network of the cytokinesis-related genes by network component analysis. BMC SYSTEMS BIOLOGY 2009; 3:110. [PMID: 19943917 PMCID: PMC2800846 DOI: 10.1186/1752-0509-3-110] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/13/2009] [Accepted: 11/27/2009] [Indexed: 11/10/2022]
Abstract
Background Network Component Analysis (NCA) is a network structure-driven framework for deducing regulatory signal dynamics. In contrast to principal component analysis, which can be employed to select the high-variance genes, NCA makes use of the connectivity structure from transcriptional regulatory networks to infer dynamics of transcription factor activities. Using the budding yeast Saccharomyces cerevisiae as a model system, we aim to deduce regulatory actions of cytokinesis-related genes, using precise spatial proximity (midbody) and/or temporal synchronicity (cytokinesis) to avoid full-scale computation from genome-wide databases. Results NCA was applied to infer regulatory actions of transcription factor activity from microarray data and partial transcription factor-gene connectivity information for cytokinesis-related genes, which were a subset of genome-wide datasets. No literature has so far discussed the inferred results through NCA are independent of the scale of the gene expression dataset. To avoid full-scale computation from genome-wide databases, four cytokinesis-related gene cases were selected for NCA by running computational analysis over the transcription factor database to confirm the approach being scale-free. The inferred dynamics of transcription factor activity through NCA were independent of the scale of the data matrix selected from the four cytokinesis-related gene sets. Moreover, the inferred regulatory actions were nearly identical to published observations for the selected cytokinesis-related genes in the budding yeast; namely, Mcm1, Ndd1, and Fkh2, which form a transcription factor complex to control expression of the CLB2 cluster (i.e. BUD4, CHS2, IQG1, and CDC5). Conclusion In this study, using S. cerevisiae as a model system, NCA was successfully applied to infer similar regulatory actions of transcription factor activities from two various microarray databases and several partial transcription factor-gene connectivity datasets for selected cytokinesis-related genes independent of data sizes. The regulated action for four selected cytokinesis-related genes (BUD4, CHS2, IQG1, and CDC5) belongs to the M-phase or M/G1 phase, consistent with the empirical observations that in S. cerevisiae, the Mcm1-Ndd1-Fkh2 transcription factor complex can regulate expression of the cytokinesis-related genes BUD4, CHS2, IQG1, and CDC5. Since Bud4, Iqg1, and Cdc5 are highly conserved between human and yeast, results obtained from NCA for cytokinesis in the budding yeast can lead to a suggestion that human cells should have the transcription regulator(s) as the budding yeast Mcm1-Ndd1-Fkh2 transcription factor complex in controlling occurrence of cytokinesis.
Collapse
Affiliation(s)
- Shun-Fu Chen
- Department of Chemical Engineering, National Chung Cheng University, Chia-Yi 62102, Taiwan.
| | | | | | | | | | | | | |
Collapse
|
83
|
Nishihama R, Schreiter JH, Onishi M, Vallen EA, Hanna J, Moravcevic K, Lippincott MF, Han H, Lemmon MA, Pringle JR, Bi E. Role of Inn1 and its interactions with Hof1 and Cyk3 in promoting cleavage furrow and septum formation in S. cerevisiae. ACTA ACUST UNITED AC 2009; 185:995-1012. [PMID: 19528296 PMCID: PMC2711614 DOI: 10.1083/jcb.200903125] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Cytokinesis requires coordination of actomyosin ring (AMR) contraction with rearrangements of the plasma membrane and extracellular matrix. In Saccharomyces cerevisiae, new membrane, the chitin synthase Chs2 (which forms the primary septum [PS]), and the protein Inn1 are all delivered to the division site upon mitotic exit even when the AMR is absent. Inn1 is essential for PS formation but not for Chs2 localization. The Inn1 C-terminal region is necessary for localization, and distinct PXXP motifs in this region mediate functionally important interactions with SH3 domains in the cytokinesis proteins Hof1 (an F-BAR protein) and Cyk3 (whose overexpression can restore PS formation in inn1Δ cells). The Inn1 N terminus resembles C2 domains but does not appear to bind phospholipids; nonetheless, when overexpressed or fused to Hof1, it can provide Inn1 function even in the absence of the AMR. Thus, Inn1 and Cyk3 appear to cooperate in activating Chs2 for PS formation, which allows coordination of AMR contraction with ingression of the cleavage furrow.
Collapse
Affiliation(s)
- Ryuichi Nishihama
- Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
84
|
Burkard ME, Maciejowski J, Rodriguez-Bravo V, Repka M, Lowery DM, Clauser KR, Zhang C, Shokat KM, Carr SA, Yaffe MB, Jallepalli PV. Plk1 self-organization and priming phosphorylation of HsCYK-4 at the spindle midzone regulate the onset of division in human cells. PLoS Biol 2009; 7:e1000111. [PMID: 19468302 PMCID: PMC2680336 DOI: 10.1371/journal.pbio.1000111] [Citation(s) in RCA: 141] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2008] [Accepted: 03/31/2009] [Indexed: 12/24/2022] Open
Abstract
Animal cells initiate cytokinesis in parallel with anaphase onset, when an actomyosin ring assembles and constricts through localized activation of the small GTPase RhoA, giving rise to a cleavage furrow. Furrow formation relies on positional cues provided by anaphase spindle microtubules (MTs), but how such cues are generated remains unclear. Using chemical genetics to achieve both temporal and spatial control, we show that the self-organized delivery of Polo-like kinase 1 (Plk1) to the midzone and its local phosphorylation of a MT-bound substrate are critical for generating this furrow-inducing signal. When Plk1 was active but unable to target itself to this equatorial landmark, both cortical RhoA recruitment and furrow induction failed to occur, thus recapitulating the effects of anaphase-specific Plk1 inhibition. Using tandem mass spectrometry and phosphospecific antibodies, we found that Plk1 binds and directly phosphorylates the HsCYK-4 subunit of centralspindlin (also known as MgcRacGAP) at the midzone. At serine 157, this modification creates a major docking site for the tandem BRCT repeats of the Rho GTP exchange factor Ect2. Cells expressing only a nonphosphorylatable form of HsCYK-4 failed to localize Ect2 at the midzone and were severely impaired in cleavage furrow formation, implying that HsCYK-4 is Plk1's rate-limiting target upstream of RhoA. Conversely, tethering an inhibitor-resistant allele of Plk1 to HsCYK-4 allowed furrows to form despite global inhibition of all other Plk1 molecules in the cell. Our findings illuminate two key mechanisms governing the initiation of cytokinesis in human cells and illustrate the power of chemical genetics to probe such regulation both in time and space.
Collapse
Affiliation(s)
- Mark E. Burkard
- Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York, United States of America
- Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, New York, United States of America
| | - John Maciejowski
- Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York, United States of America
| | - Verónica Rodriguez-Bravo
- Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York, United States of America
| | - Michael Repka
- Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York, United States of America
| | - Drew M. Lowery
- Departments of Biology and Biological Engineering, Center for Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Karl R. Clauser
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
| | - Chao Zhang
- Howard Hughes Medical Institute, University of California at San Francisco, San Francisco, California, United States of America
- Department of Cellular and Molecular Pharmacology, University of California at San Francisco, San Francisco, California, United States of America
| | - Kevan M. Shokat
- Howard Hughes Medical Institute, University of California at San Francisco, San Francisco, California, United States of America
- Department of Cellular and Molecular Pharmacology, University of California at San Francisco, San Francisco, California, United States of America
| | - Steven A. Carr
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
| | - Michael B. Yaffe
- Departments of Biology and Biological Engineering, Center for Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
| | - Prasad V. Jallepalli
- Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York, United States of America
| |
Collapse
|
85
|
Abstract
Proper spatial and temporal regulation of the small GTPase RhoA at the equatorial cortex represents a critical step in the specification of the division plane in eukaryotes. Despite increased understanding of the mechanisms whereby RhoA becomes active following chromosome segregation, far less is known about how RhoA is spatially regulated so that it concentrates precisely at the division site. In the April 1, 2009, issue of Genes & Development, Yoshida and colleagues (pp. 810-823) uncovered two genetically separable mechanisms whereby Rho1 is recruited to the bud neck in the budding yeast Saccharomyces cerevisiae to facilitate cytokinesis.
Collapse
Affiliation(s)
- Benjamin A Wolfe
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois 60637, USA
| | | |
Collapse
|
86
|
Yoshida S, Bartolini S, Pellman D. Mechanisms for concentrating Rho1 during cytokinesis. Genes Dev 2009; 23:810-23. [PMID: 19339687 DOI: 10.1101/gad.1785209] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The small GTP-binding protein, Rho1/RhoA plays a central role in cytokinetic actomyosin ring (CAR) assembly and cytokinesis. Concentration of Rho proteins at the division site is a general feature of cytokinesis, yet the mechanisms for recruiting Rho to the division site for cytokinesis remain poorly understood. We find that budding yeast utilizes two mechanisms to concentrate Rho1 at the division site. During anaphase, the primary mechanism for recruiting Rho1 is binding to its guanine nucleotide exchange factors (GEFs). GEF-dependent recruitment requires that Rho1 has the ability to pass through its GDP or unliganded state prior to being GTP-loaded. We were able to test this model by generating viable yeast lacking all identifiable Rho1 GEFs. Later, during septation and abscission, a second GEF-independent mechanism contributes to Rho1 bud neck targeting. This GEF-independent mechanism requires the Rho1 polybasic sequence that binds to acidic phospholipids, including phosphatidylinositol 4,5-bisphosphate (PIP2). This latter mechanism is functionally important because Rho1 activation or increased cellular levels of PIP2 promote cytokinesis in the absence of a contractile ring. These findings comprehensively define the targeting mechanisms of Rho1 essential for cytokinesis in yeast, and are likely to be relevant to cytokinesis in other organisms.
Collapse
Affiliation(s)
- Satoshi Yoshida
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Division of Hematology/Oncology, Children's Hospital Boston, Boston, Massachusetts 02115, USA
| | | | | |
Collapse
|
87
|
Archambault V, Glover DM. Polo-like kinases: conservation and divergence in their functions and regulation. Nat Rev Mol Cell Biol 2009; 10:265-75. [PMID: 19305416 DOI: 10.1038/nrm2653] [Citation(s) in RCA: 492] [Impact Index Per Article: 32.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Polo-like kinases (Plks) are potent regulators of M phase that are conserved from yeasts to humans. Their roles in mitotic entry, spindle pole functions and cytokinesis are broadly conserved despite physical and molecular differences in these processes in disparate organisms. Plks are characterized by their Polo-box domain, which mediates protein interactions. They are additionally controlled by phosphorylation, proteolysis and transcription, depending on the biological context. Plks are now recognized to link cell division to developmental processes and to function in differentiated cells. A comparison of Plk function and regulation between organisms offers insight into the rich variations of cell division.
Collapse
Affiliation(s)
- Vincent Archambault
- Cancer Research UK, Cell Cycle Genetics Research Group, University of Cambridge, Department of Genetics, Downing Street, Cambridge, CB2 3EH, UK.
| | | |
Collapse
|
88
|
Roberts-Galbraith RH, Gould KL. Stepping into the ring: the SIN takes on contractile ring assembly. Genes Dev 2009; 22:3082-8. [PMID: 19056889 DOI: 10.1101/gad.1748908] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The septation initiation network (SIN) regulates the timing of septum formation in Schizosaccharomyces pombe. However, whether and how the SIN functions in contractile ring formation has remained unclear. In this issue of Genes & Development, Hachet and Simanis (3205-3216) demonstrate that the SIN acts downstream from the Plo1 kinase to control a final step in contractile ring assembly. Furthermore, their careful analysis of contractile ring formation may help bridge two existing models of cytokinetic ring formation.
Collapse
Affiliation(s)
- Rachel H Roberts-Galbraith
- Howard Hughes Medical Institute, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA
| | | |
Collapse
|
89
|
Tully GH, Nishihama R, Pringle JR, Morgan DO. The anaphase-promoting complex promotes actomyosin-ring disassembly during cytokinesis in yeast. Mol Biol Cell 2008; 20:1201-12. [PMID: 19109423 DOI: 10.1091/mbc.e08-08-0822] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The anaphase-promoting complex (APC) is a ubiquitin ligase that controls progression through mitosis by targeting specific proteins for degradation. It is unclear whether the APC also contributes to the control of cytokinesis, the process that divides the cell after mitosis. We addressed this question in the yeast Saccharomyces cerevisiae by studying the effects of APC mutations on the actomyosin ring, a structure containing actin, myosin, and several other proteins that forms at the division site and is important for cytokinesis. In wild-type cells, actomyosin-ring constituents are removed progressively from the ring during contraction and disassembled completely thereafter. In cells lacking the APC activator Cdh1, the actomyosin ring contracts at a normal rate, but ring constituents are not disassembled normally during or after contraction. After cytokinesis in mutant cells, aggregates of ring proteins remain at the division site and at additional foci in other parts of the cell. A key target of APC(Cdh1) is the ring component Iqg1, the destruction of which contributes to actomyosin-ring disassembly. Deletion of CDH1 also exacerbates actomyosin-ring disassembly defects in cells with mutations in the myosin light-chain Mlc2, suggesting that Mlc2 and the APC employ independent mechanisms to promote ring disassembly during cytokinesis.
Collapse
Affiliation(s)
- Gregory H Tully
- Department of Physiology, University of California, San Francisco, CA 94158, USA
| | | | | | | |
Collapse
|
90
|
Takaki T, Trenz K, Costanzo V, Petronczki M. Polo-like kinase 1 reaches beyond mitosis--cytokinesis, DNA damage response, and development. Curr Opin Cell Biol 2008; 20:650-60. [PMID: 19000759 DOI: 10.1016/j.ceb.2008.10.005] [Citation(s) in RCA: 136] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2008] [Revised: 09/29/2008] [Accepted: 10/13/2008] [Indexed: 01/12/2023]
Abstract
Polo-like kinase 1 (Plk1) is a key regulator of cell division in eukaryotic cells. In this review we focus on recent leaps in our understanding of how Plk1 controls cytokinesis, the final stage of cell division. Furthermore, we will go beyond mitosis to highlight unexpected roles of Plk1 during interphase and during animal development. In vertebrate cells, Plk1 has emerged as a novel player in maintaining genomic stability during DNA replication and as an important modulator of the DNA damage checkpoint. Plk1 functions extend past the 'core' cell cycle. Plk1 acts as a link between developmental processes and the cell cycle machinery during asymmetric cell divisions in flies and worms. The term 'mitotic kinase' might not do justice to Plk1 in the light of these recent results.
Collapse
Affiliation(s)
- Tohru Takaki
- Cell Division and Aneuploidy Laboratory, Cancer Research UK London Research Institute, Clare Hall Laboratories, South Mimms, Hertfordshire EN6 3LD, United Kingdom
| | | | | | | |
Collapse
|
91
|
Schwartz D, Chou MF, Church GM. Predicting protein post-translational modifications using meta-analysis of proteome scale data sets. Mol Cell Proteomics 2008; 8:365-79. [PMID: 18974045 DOI: 10.1074/mcp.m800332-mcp200] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protein post-translational modifications are an important biological regulatory mechanism, and the rate of their discovery using high throughput techniques is rapidly increasingly. To make use of this wealth of sequence data, we introduce a new general strategy designed to predict a variety of post-translational modifications in several organisms. We used the motif-x program to determine phosphorylation motifs in yeast, fly, mouse, and man and lysine acetylation motifs in man. These motifs were then scanned against proteomic sequence data using a newly developed tool called scan-x to globally predict other potential modification sites within these organisms. 10-fold cross-validation was used to determine the sensitivity and minimum specificity for each set of predictions, all of which showed improvement over other available tools for phosphoprediction. New motif discovery is a byproduct of this approach, and the phosphorylation motif analyses provide strong evidence of evolutionary conservation of both known and novel kinase motifs.
Collapse
Affiliation(s)
- Daniel Schwartz
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA.
| | | | | |
Collapse
|
92
|
The synthetic genetic network around PKC1 identifies novel modulators and components of protein kinase C signaling in Saccharomyces cerevisiae. EUKARYOTIC CELL 2008; 7:1880-7. [PMID: 18806213 DOI: 10.1128/ec.00222-08] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Budding yeast Saccharomyces cerevisiae contains one protein kinase C (PKC) isozyme encoded by the essential gene PKC1. Pkc1 is activated by the small GTPase Rho1 and plays a central role in the cell wall integrity (CWI) signaling pathway. This pathway acts primarily to remodel the cell surface throughout the normal life cycle and upon various environmental stresses. The pathway is heavily branched, with multiple nonessential branches feeding into and out of the central essential Rho1-Pkc1 module. In an attempt to identify novel components and modifiers of CWI signaling, we determined the synthetic lethal genetic network around PKC1 by using dominant-negative synthetic genetic array analysis. The resulting mutants are hypersensitive to lowered Pkc1 activity. The corresponding 21 nonessential genes are closely related to CWI function: 14 behave in a chemical-genetic epistasis test as acting in the pathway, and 6 of these genes encode known components. Twelve of the 21 null mutants display elevated CWI reporter activity, consistent with the idea that the pathway is activated by and compensates for loss of the gene products. Four of the 21 mutants display low CWI reporter activity, consistent with the idea that the pathway is compromised in these mutants. One of the latter group of mutants lacks Ack1(Ydl203c), an uncharacterized SEL-1 domain-containing protein that we find modulates pathway activity. Epistasis analysis places Ack1 upstream of Pkc1 in the CWI pathway and dependent on the upstream Rho1 GTP exchange factors Rom2 and Tus1. Overall, the synthetic genetic network around PKC1 directly and efficiently identifies known and novel components of PKC signaling in yeast.
Collapse
|
93
|
Logan MR, Nguyen T, Szapiel N, Knockleby J, Por H, Zadworny M, Neszt M, Harrison P, Bussey H, Mandato CA, Vogel J, Lesage G. Genetic interaction network of the Saccharomyces cerevisiae type 1 phosphatase Glc7. BMC Genomics 2008; 9:336. [PMID: 18627629 PMCID: PMC2481269 DOI: 10.1186/1471-2164-9-336] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2008] [Accepted: 07/15/2008] [Indexed: 01/21/2023] Open
Abstract
Background Protein kinases and phosphatases regulate protein phosphorylation, a critical means of modulating protein function, stability and localization. The identification of functional networks for protein phosphatases has been slow due to their redundant nature and the lack of large-scale analyses. We hypothesized that a genome-scale analysis of genetic interactions using the Synthetic Genetic Array could reveal protein phosphatase functional networks. We apply this approach to the conserved type 1 protein phosphatase Glc7, which regulates numerous cellular processes in budding yeast. Results We created a novel glc7 catalytic mutant (glc7-E101Q). Phenotypic analysis indicates that this novel allele exhibits slow growth and defects in glucose metabolism but normal cell cycle progression and chromosome segregation. This suggests that glc7-E101Q is a hypomorphic glc7 mutant. Synthetic Genetic Array analysis of glc7-E101Q revealed a broad network of 245 synthetic sick/lethal interactions reflecting that many processes are required when Glc7 function is compromised such as histone modification, chromosome segregation and cytokinesis, nutrient sensing and DNA damage. In addition, mitochondrial activity and inheritance and lipid metabolism were identified as new processes involved in buffering Glc7 function. An interaction network among 95 genes genetically interacting with GLC7 was constructed by integration of genetic and physical interaction data. The obtained network has a modular architecture, and the interconnection among the modules reflects the cooperation of the processes buffering Glc7 function. Conclusion We found 245 genes required for the normal growth of the glc7-E101Q mutant. Functional grouping of these genes and analysis of their physical and genetic interaction patterns bring new information on Glc7-regulated processes.
Collapse
Affiliation(s)
- Michael R Logan
- Department of Biology, McGill University, Montreal (QC), Canada.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
94
|
Involvement of Saccharomyces cerevisiae Avo3p/Tsc11p in maintaining TOR complex 2 integrity and coupling to downstream signaling. EUKARYOTIC CELL 2008; 7:1328-43. [PMID: 18552287 DOI: 10.1128/ec.00065-08] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Target-of-rapamycin proteins (TORs) are Ser/Thr kinases serving a central role in cell growth control. TORs function in two conserved multiprotein complexes, TOR complex 1 (TORC1) and TORC2; the mechanisms underlying their actions and regulation are not fully elucidated. Saccharomyces TORC2, containing Tor2p, Avo1p, Avo2p, Avo3p/Tsc11p, Bit61p, and Lst8p, regulates cell integrity and actin organization. Two classes of avo3 temperature-sensitive (avo3(ts)) mutants that we previously identified display cell integrity and actin defects, yet one is suppressed by AVO1 while the other is suppressed by AVO2 or SLM1, defining two TORC2 downstream signaling mechanisms, one mediated by Avo1p and the other by Avo2p/Slm1p. Employing these mutants, we explored Avo3p functions in TORC2 structure and signaling. By observing binary protein interactions using coimmunoprecipitation, we discovered that the composition of TORC2 and its recruitment of the downstream effectors Slm1p and Slm2p were differentially affected in different avo3(ts) mutants. These molecular defects can be corrected only by expressing AVO3, not by expressing suppressors, highlighting the role of Avo3p as a structural and signaling scaffold for TORC2. Phenotypic modifications of avo3(ts) mutants by deletion of individual Rho1p-GTPase-activating proteins indicate that two TORC2 downstream signaling branches converge on Rho1p activation. Our results also suggest that Avo2p/Slm1p-mediated signaling, but not Avo1p-mediated signaling, links to Rho1p activation specifically through the Rho1p-guanine nucleotide exchange factor Tus1p.
Collapse
|
95
|
The yeast Tor signaling pathway is involved in G2/M transition via polo-kinase. PLoS One 2008; 3:e2223. [PMID: 18493323 PMCID: PMC2375053 DOI: 10.1371/journal.pone.0002223] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2008] [Accepted: 04/02/2008] [Indexed: 12/20/2022] Open
Abstract
The target of rapamycin (Tor) protein plays central roles in cell growth. Rapamycin inhibits cell growth and promotes cell cycle arrest at G1 (G0). However, little is known about whether Tor is involved in other stages of the cell division cycle. Here we report that the rapamycin-sensitive Tor complex 1 (TORC1) is involved in G2/M transition in S. cerevisiae. Strains carrying a temperature-sensitive allele of KOG1 (kog1-105) encoding an essential component of TORC1, as well as yeast cell treated with rapamycin show mitotic delay with prolonged G2. Overexpression of Cdc5, the yeast polo-like kinase, rescues the growth defect of kog1-105, and in turn, Cdc5 activity is attenuated in kog1-105 cells. The TORC1-Type2A phosphatase pathway mediates nucleocytoplasmic transport of Cdc5, which is prerequisite for its proper localization and function. The C-terminal polo-box domain of Cdc5 has an inhibitory role in nuclear translocation. Taken together, our results indicate a novel function of Tor in the regulation of cell cycle and proliferation.
Collapse
|
96
|
Abstract
Polo-like kinase 1 (Plk1) is a key regulator of cell division in eukaryotic cells. New techniques, including the application of small-molecule inhibitors, have greatly expanded our knowledge of the functions, targets, and regulation of this key mitotic enzyme. In this review, we focus on how Plk1 is recruited to centrosomes, kinetochores, and the spindle midzone and what the specific tasks of Plk1 at these distinct subcellular structures might be. In particular, we highlight new work on the role of Plk1 in cytokinesis in human cells. Finally, we describe how better understanding of Plk1 functions allows critical evaluation of Plk1 as a potential drug target for cancer therapy.
Collapse
Affiliation(s)
- Mark Petronczki
- Cell Division and Aneuploidy Laboratory, Cancer Research UK London Research Institute, Clare Hall Laboratories, South Mimms, Hertfordshire, EN6 3LD, United Kingdom.
| | | | | |
Collapse
|
97
|
Kono K, Nogami S, Abe M, Nishizawa M, Morishita S, Pellman D, Ohya Y. G1/S cyclin-dependent kinase regulates small GTPase Rho1p through phosphorylation of RhoGEF Tus1p in Saccharomyces cerevisiae. Mol Biol Cell 2008; 19:1763-71. [PMID: 18256282 DOI: 10.1091/mbc.e07-09-0950] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Rho1p is an essential small GTPase that plays a key role in the morphogenesis of Saccharomyces cerevisiae. We show here that the activation of Rho1p is regulated by a cyclin-dependent kinase (CDK). Rho1p is activated at the G1/S transition at the incipient-bud sites by the Cln2p (G1 cyclin) and Cdc28p (CDK) complex, in a process mediated by Tus1p, a guanine nucleotide exchange factor for Rho1p. Tus1p interacts physically with Cln2p/Cdc28p and is phosphorylated in a Cln2p/Cdc28p-dependent manner. CDK phosphorylation consensus sites in Tus1p are required for both Cln2p-dependent activation of Rho1p and polarized organization of the actin cytoskeleton. We propose that Cln2p/Cdc28p-dependent phosphorylation of Tus1p is required for appropriate temporal and spatial activation of Rho1p at the G1/S transition.
Collapse
Affiliation(s)
- Keiko Kono
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Chiba 277-8562, Japan
| | | | | | | | | | | | | |
Collapse
|
98
|
A coupled chemical-genetic and bioinformatic approach to Polo-like kinase pathway exploration. ACTA ACUST UNITED AC 2008; 14:1261-72. [PMID: 18022565 DOI: 10.1016/j.chembiol.2007.09.011] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2007] [Revised: 09/04/2007] [Accepted: 09/26/2007] [Indexed: 11/20/2022]
Abstract
Protein phosphorylation is a ubiquitous mechanism for cellular signal propagation, and signaling network complexity presents a challenge to protein kinase substrate identification. Few targets of Polo-like kinases are known, despite their significant role in coordinating cell-cycle progression. Here, we combine chemical-genetic, bioinformatic, and proteomic tools for Polo-like kinase substrate identification. Specific pharmacological inhibition of budding yeast Polo-like kinase, Cdc5, resulted in a misaligned preanaphase spindle and subsequently delayed anaphase nuclear migration, revealing a Cdc5 function. A cellular screen for Cdc5 substrates identified Spc72, a spindle pole body (SPB) component and microtubule anchor required for nuclear positioning. Spc72 bound to the Cdc5 PBD in a mitosis-specific manner, was phosphorylated by Cdc5 in vitro, and demonstrated a loss of mitotic phosphorylation in vivo upon Cdc5 inhibition. Finally, an examination of Cdc5 binding by SPB-localized proteins expanded our knowledge of Cdc5 function at the SPB.
Collapse
|
99
|
Abstract
Polo-like kinase 1 (PLK1) has important functions in maintaining genome stability via its role in mitosis. Because PLK1 is up-regulated in many invasive carcinomas, we asked whether it may also play a role in acquisition of invasiveness, a crucial step in transition to malignancy. In a model of metaplastic basal-like breast carcinoma progression, we found that PLK1 expression is necessary but not sufficient to induce invasiveness through laminin-rich extracellular matrix. PLK1 mediates invasion via vimentin and beta1 integrin, both of which are necessary. We observed that PLK1 phosphorylates vimentin on Ser82, which in turn regulates cell surface levels of beta1 integrin. We found PLK1 to be also highly expressed in preinvasive in situ carcinomas of the breast. These results support a role for the involvement of PLK1 in the invasion process and point to this pathway as a potential therapeutic target for preinvasive and invasive breast carcinoma treatment.
Collapse
MESH Headings
- Animals
- Apoptosis/physiology
- Blotting, Western
- Breast Neoplasms/enzymology
- Breast Neoplasms/genetics
- Breast Neoplasms/therapy
- Carcinoma, Ductal, Breast/enzymology
- Carcinoma, Ductal, Breast/pathology
- Carcinoma, Intraductal, Noninfiltrating/enzymology
- Carcinoma, Intraductal, Noninfiltrating/pathology
- Cell Cycle Proteins/antagonists & inhibitors
- Cell Cycle Proteins/genetics
- Cell Cycle Proteins/metabolism
- Cell Movement
- Collagen
- Drug Combinations
- Extracellular Matrix/enzymology
- Female
- Humans
- In Situ Nick-End Labeling
- Integrin beta1/metabolism
- Laminin/metabolism
- Mice
- Mice, Inbred BALB C
- Mice, Nude
- Phosphorylation
- Protein Serine-Threonine Kinases/antagonists & inhibitors
- Protein Serine-Threonine Kinases/genetics
- Protein Serine-Threonine Kinases/metabolism
- Proteoglycans
- Proto-Oncogene Proteins/antagonists & inhibitors
- Proto-Oncogene Proteins/genetics
- Proto-Oncogene Proteins/metabolism
- RNA, Small Interfering/pharmacology
- Vimentin/metabolism
- Polo-Like Kinase 1
Collapse
Affiliation(s)
- Aylin Rizki
- Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA.
| | | | | |
Collapse
|
100
|
Abstract
Cytokinesis is the process by which cells physically separate after the duplication and spatial segregation of the genetic material. A number of general principles apply to this process. First the microtubule cytoskeleton plays an important role in the choice and positioning of the division site. Once the site is chosen, the local assembly of the actomyosin contractile ring remodels the plasma membrane. Finally, membrane trafficking to and membrane fusion at the division site cause the physical separation of the daughter cells, a process termed abscission. Here we will discuss recent advances in our understanding of the mechanisms of cytokinesis in animals, yeast, and plants.
Collapse
Affiliation(s)
- Francis A Barr
- University of Liverpool, Cancer Research Centre, 200 London Road, Liverpool L3 9TA, UK.
| | | |
Collapse
|