101
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Abstract
The ubiquitin-proteasome system plays a pivotal role in the sequence of events leading to cell division known as the cell cycle. Not only does ubiquitin-mediated proteolysis constitute a critical component of the core oscillator that drives the cell cycle in all eukaryotes, it is also central to the mechanisms that ensure that the integrity of the genome is maintained. These functions are primarily carried out by two families of E3 ubiquitin ligases, the Skp/cullin/F-box-containing and anaphase-promoting complex/cyclosome complexes. However, beyond those functions associated with regulation of central cell cycle events, many peripheral cell cycle-related processes rely on ubiquitylation for signaling, homeostasis, and dynamicity, involving additional types of ubiquitin ligases and regulators. We are only beginning to understand the diversity and complexity of this regulation.
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Affiliation(s)
- Leonardo K Teixeira
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA
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102
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Brownlee CW, Rogers GC. Show me your license, please: deregulation of centriole duplication mechanisms that promote amplification. Cell Mol Life Sci 2013; 70:1021-34. [PMID: 22892665 PMCID: PMC11113234 DOI: 10.1007/s00018-012-1102-6] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Revised: 07/13/2012] [Accepted: 07/17/2012] [Indexed: 12/13/2022]
Abstract
Centrosomes are organelles involved in generating and organizing the interphase microtubule cytoskeleton, mitotic spindles and cilia. At the centrosome core are a pair of centrioles, structures that act as the duplicating elements of this organelle. Centrioles function to recruit and organize pericentriolar material which nucleates microtubules. While centrioles are relatively simple in construction, the mechanics of centriole biogenesis remain an important yet poorly understood process. More mysterious still are the regulatory mechanisms that oversee centriole assembly. The fidelity of centriole duplication is critical as defects in either the assembly or number of centrioles promote aneuploidy, primary microcephaly, birth defects, ciliopathies and tumorigenesis. In addition, some pathogens employ mechanisms to promote centriole overduplication to the detriment of the host cell. This review summarizes our current understanding of this important topic, highlighting the need for further study if new therapeutics are to be developed to treat diseases arising from defects of centrosome duplication.
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Affiliation(s)
- Christopher W. Brownlee
- Department of Cellular and Molecular Medicine, Arizona Cancer Center, University of Arizona, Tucson, AZ 85724 USA
| | - Gregory C. Rogers
- Department of Cellular and Molecular Medicine, Arizona Cancer Center, University of Arizona, Tucson, AZ 85724 USA
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103
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Werner A, Disanza A, Reifenberger N, Habeck G, Becker J, Calabrese M, Urlaub H, Lorenz H, Schulman B, Scita G, Melchior F. SCFFbxw5 mediates transient degradation of actin remodeller Eps8 to allow proper mitotic progression. Nat Cell Biol 2013; 15:179-88. [PMID: 23314863 DOI: 10.1038/ncb2661] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Accepted: 11/26/2012] [Indexed: 12/22/2022]
Abstract
Eps8, a bi-functional actin cytoskeleton remodeller, is a positive regulator of cell proliferation and motility. Here, we describe an unrecognized mechanism regulating Eps8 that is required for proper mitotic progression: whereas Eps8 is stable in G1 and S phase, its half-life drops sharply in G2. This requires G2-specific proteasomal degradation mediated by the ubiquitin E3 ligase SCF(Fbxw5). Consistent with a short window of degradation, Eps8 disappears from the cell cortex early in mitosis, but reappears at the midzone of dividing cells. Failure to reduce Eps8 levels in G2 prolongs its localization at the cell cortex and markedly delays cell rounding and prometaphase duration. However, during late stages of mitosis and cytokinesis, Eps8 capping activity is required to prevent membrane blebbing and cell-shape deformations. Our findings identify SCF(Fbxw5)-driven fluctuation of Eps8 levels as an important mechanism that contributes to cell-shape changes during entry into-and exit from-mitosis.
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Affiliation(s)
- Achim Werner
- Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, Germany.
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104
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Cuevas R, Korzeniewski N, Tolstov Y, Hohenfellner M, Duensing S. FGF-2 Disrupts Mitotic Stability in Prostate Cancer through the Intracellular Trafficking Protein CEP57. Cancer Res 2012; 73:1400-10. [DOI: 10.1158/0008-5472.can-12-1857] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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105
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Abstract
Centrioles are the key foundation of centrosomes and cilia, yet a molecular understanding of how they form has only recently begun to emerge. Building a fully functional centriole that can form a centrosome and cilium requires two cell cycles. Centriole building starts with procentriole nucleation, a process that is coordinated by the conserved proteins Plk4/Zyg-1, and Asterless/Cep152. Subsequently, Sas-6, a conserved procentriole protein, self-assembles to provide nine-fold symmetry to the centriole scaffold. The procentriole then continues to elongate into a centriole, a process controlled by Sas-4/CPAP and CP110. Then, centrioles recruit Sas-4-mediated pre-assembled centrosomal complexes from the cytoplasm to form the pericentriolar material (PCM). Finally, CP110 and its interacting proteins are involved in controlling the timing of centriole templating of the cilium.
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Affiliation(s)
- Tomer Avidor-Reiss
- Department of Biological Sciences, University of Toledo, Toledo, OH 43606, USA.
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106
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Slevin LK, Nye J, Pinkerton DC, Buster DW, Rogers GC, Slep KC. The structure of the plk4 cryptic polo box reveals two tandem polo boxes required for centriole duplication. Structure 2012; 20:1905-17. [PMID: 23000383 DOI: 10.1016/j.str.2012.08.025] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Revised: 08/26/2012] [Accepted: 08/28/2012] [Indexed: 11/19/2022]
Abstract
Centrioles are key microtubule polarity determinants. Centriole duplication is tightly controlled to prevent cells from developing multipolar spindles, a situation that promotes chromosomal instability. A conserved component in the duplication pathway is Plk4, a polo kinase family member that localizes to centrioles in M/G1. To limit centriole duplication, Plk4 levels are controlled through trans-autophosphorylation that primes ubiquitination. In contrast to Plks 1-3, Plk4 possesses a unique central region called the "cryptic polo box." Here, we present the crystal structure of this region at 2.3 Å resolution. Surprisingly, the structure reveals two tandem homodimerized polo boxes, PB1-PB2, that form a unique winged architecture. The full PB1-PB2 cassette is required for binding the centriolar protein Asterless as well as robust centriole targeting. Thus, with its C-terminal polo box (PB3), Plk4 has a triple polo box architecture that facilitates oligomerization, targeting, and promotes trans-autophosphorylation, limiting centriole duplication to once per cell cycle.
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Affiliation(s)
- Lauren K Slevin
- Department of Biology, CB 3280, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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107
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Hatano T, Sluder G. The interrelationship between APC/C and Plk1 activities in centriole disengagement. Biol Open 2012; 1:1153-60. [PMID: 23213396 PMCID: PMC3507193 DOI: 10.1242/bio.20122626] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Accepted: 08/06/2012] [Indexed: 11/20/2022] Open
Abstract
Mother–daughter centriole disengagement, the necessary first step in centriole duplication, involves Plk1 activity in early mitosis and separase activity after APC/C activity mediates securin degradation. Plk1 activity is thought to be essential and sufficient for centriole disengagement with separase activity playing a supporting but non-essential role. In separase null cells, however, centriole disengagement is substantially delayed. The ability of APC/C activity alone to mediate centriole disengagement has not been directly tested. We investigate the interrelationship between Plk1 and APC/C activities in disengaging centrioles in S or G2 HeLa and RPE1 cells, cell types that do not reduplicate centrioles when arrested in S phase. Knockdown of the interphase APC/C inhibitor Emi1 leads to centriole disengagement and reduplication of the mother centrioles, though this is slow. Strong inhibition of Plk1 activity, if any, during S does not block centriole disengagement and mother centriole reduplication in Emi1 depleted cells. Centriole disengagement depends on APC/C–Cdh1 activity, not APC/C–Cdc20 activity. Also, Plk1 and APC/C–Cdh1 activities can independently promote centriole disengagement in G2 arrested cells. Thus, Plk1 and APC/C–Cdh1 activities are independent but slow pathways for centriole disengagement. By having two slow mechanisms for disengagement working together, the cell ensures that centrioles will not prematurely separate in late G2 or early mitosis, thereby risking multipolar spindle assembly, but rather disengage in a timely fashion only late in mitosis.
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Affiliation(s)
- Toshiyuki Hatano
- Department of Cell Biology, University of Massachusetts Medical School , Worcester, MA 01605 , USA
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108
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Majumder S, Slabodnick M, Pike A, Marquardt J, Fisk HA. VDAC3 regulates centriole assembly by targeting Mps1 to centrosomes. Cell Cycle 2012; 11:3666-78. [PMID: 22935710 DOI: 10.4161/cc.21927] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Centrioles are duplicated during S-phase to generate the two centrosomes that serve as mitotic spindle poles during mitosis. The centrosomal pool of the Mps1 kinase is important for centriole assembly, but how Mps1 is delivered to centrosomes is unknown. Here we have identified a centrosome localization domain within Mps1 and identified the mitochondrial porin VDAC3 as a protein that binds to this region of Mps1. Moreover, we show that VDAC3 is present at the mother centriole and modulates centriole assembly by recruiting Mps1 to centrosomes.
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Affiliation(s)
- Shubhra Majumder
- Department of Molecular Genetics, The Ohio State University, Columbus, OH, USA
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109
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Habermann K, Lange BM. New insights into subcomplex assembly and modifications of centrosomal proteins. Cell Div 2012; 7:17. [PMID: 22800182 PMCID: PMC3479078 DOI: 10.1186/1747-1028-7-17] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Accepted: 07/04/2012] [Indexed: 12/19/2022] Open
Abstract
This review provides a brief overview of the recent work on centrosome proteomics, protein complex identification and functional characterization with an emphasis on the literature of the last three years. Proteomics, genetic screens and comparative genomics studies in different model organisms have almost exhaustively identified the molecular components of the centrosome. However, much knowledge is still missing on the protein-protein interactions, protein modifications and molecular changes the centrosome undergoes throughout the cell cycle and development. The dynamic nature of this large multi-protein complex is reflected in the variety of annotated subcellular locations and biological processes of its proposed components. Some centrosomal proteins and complexes have been studied intensively in different organisms and provided detailed insight into centrosome functions. For example, the molecular, structural and functional characterization of the γ-Tubulin ring complex (γ-TuRC) and the the discovery of the Augmin/HAUS complex has advanced our understanding of microtubule (MT) capture, nucleation and organization. Surprising findings revealed new functions and localizations of proteins that were previously regarded as bona fide centriolar or centrosome components, e.g. at the kinetochore or in the nuclear pore complex regulating MT plus end capture or mRNA processing. Many centrosome components undergo posttranslational modifications such as phosphorylation, SUMOylation and ubiquitylation that are critical in modulating centrosome function and biology. A wealth of information has recently become available driven by new developments in technologies such as mass spectrometry, light and electron microscopy providing more detailed molecular and structural definition of the centrosome and particular roles of proteins throughout the cell cycle and development.
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Affiliation(s)
- Karin Habermann
- Department of Vertebrate Genomics, Max Planck Institute for Molecular Genetics, Berlin, Germany.
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110
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Centrosomes in the zebrafish (Danio rerio): a review including the related basal body. Cilia 2012; 1:9. [PMID: 23351173 PMCID: PMC3555702 DOI: 10.1186/2046-2530-1-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Accepted: 06/07/2012] [Indexed: 12/15/2022] Open
Abstract
Ever since Edouard Van Beneden and Theodor Boveri first formally described the centrosome in the late 1800s, it has captivated cell biologists. The name clearly indicated its central importance to cell functioning, even to these early investigators. We now know of its role as a major microtubule-organizing center (MTOC) and of its dynamic roles in cell division, vesicle trafficking and for its relative, the basal body, ciliogenesis. While centrosomes are found in most animal cells, notably it is absent in most oocytes and higher plant cells. Nevertheless, it appears that critical components of the centrosome act as MTOCs in these cells as well. The zebrafish has emerged as an exciting and promising new model organism, primarily due to the pioneering efforts of George Streisinger to use zebrafish in genetic studies and due to Christiane Nusslein-Volhard, Wolfgang Driever and their teams of collaborators, who applied forward genetics to elicit a large number of mutant lines. The transparency and rapid external development of the embryo allow for experiments not easily done in other vertebrates. The ease of producing transgenic lines, often with the use of fluorescent reporters, and gene knockdowns with antisense morpholinos further contributes to the appeal of the model as an experimental system. The added advantage of high-throughput screening of small-molecule libraries, as well as the ease of mass rearing together with low cost, makes the zebrafish a true frontrunner as a model vertebrate organism. The zebrafish has a body plan shared by all vertebrates, including humans. This conservation of body plan provides added significance to the existing lines of zebrafish as human disease models and adds an impetus to the ongoing efforts to develop new models. In this review, the current state of knowledge about the centrosome in the zebrafish model is explored. Also, studies on the related basal body in zebrafish and their relationship to ciliogenesis are reviewed.
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111
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Peel N, Dougherty M, Goeres J, Liu Y, O'Connell KF. The C. elegans F-box proteins LIN-23 and SEL-10 antagonize centrosome duplication by regulating ZYG-1 levels. J Cell Sci 2012; 125:3535-44. [PMID: 22623721 DOI: 10.1242/jcs.097105] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The correct segregation of DNA during cell division requires formation of a bipolar spindle, organized at each pole by a centrosome. The regulation of centrosome duplication such that each mitotic cell has exactly two centrosomes is therefore of central importance to cell division. Deregulation of centrosome duplication causes the appearance of supernumerary centrosomes, which are a hallmark of many cancer cells and can contribute to tumorigenesis. Overexpression of the kinase Plk4, which is required for centrosome duplication, causes the formation of extra centrosomes, and aberrant Plk4 expression levels are associated with cancer. Data from Drosophila and human cells show that Plk4 levels are regulated by the SCF ubiquitin ligase and proteasomal degradation. Recognition of Plk4 by the SCF complex is mediated by the F-box protein Slimb/βTrCP. We show that levels of the C. elegans Plk4 homolog ZYG-1 are elevated by impairing proteasome or SCF function, indicating that ZYG-1 is regulated by a conserved mechanism. In C. elegans, similar to Drosophila and humans, we find that the Slimb/βTrCP homolog LIN-23 regulates ZYG-1 levels. In addition, we show that a second F-box protein, SEL-10, also contributes to ZYG-1 regulation. Co-depletion of LIN-23 and SEL-10 suggests these proteins function cooperatively. Because SEL-10 is the homolog of human FBW7, which is frequently mutated in cancer, our findings have implications for understanding tumorigenesis.
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Affiliation(s)
- Nina Peel
- Department of Biology, The College of New Jersey, Ewing, NJ 08628, USA.
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112
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Goehring NW, Hyman AA. Organelle growth control through limiting pools of cytoplasmic components. Curr Biol 2012; 22:R330-9. [PMID: 22575475 DOI: 10.1016/j.cub.2012.03.046] [Citation(s) in RCA: 142] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The critical importance of controlling the size and number of intracellular organelles has led to a variety of mechanisms for regulating the formation and growth of cellular structures. In this review, we explore a class of mechanisms for organelle growth control that rely primarily on the cytoplasm as a 'limiting pool' of available material. These mechanisms are based on the idea that, as organelles grow, they incorporate subunits from the cytoplasm. If this subunit pool is limited, organelle growth will lead to depletion of subunits from the cytoplasm. Free subunit concentration therefore provides a measure of the number of incorporated subunits and thus the current size of the organelle. Because organelle growth rates are typically a function of subunit concentration, cytoplasmic depletion links organelle size, free subunit concentration, and growth rates, ensuring that as the organelle grows, its rate of growth slows. Thus, a limiting cytoplasmic pool provides a powerful mechanism for size-dependent regulation of growth without recourse to active mechanisms to measure size or modulate growth rates. Variations of this general idea allow not only for size control, but also cell-size-dependent scaling of cellular structures, coordination of growth between similar structures within a cell, and the enforcement of singularity in structure formation, when only a single copy of a structure is desired. Here, we review several examples of such mechanisms in cellular processes as diverse as centriole duplication, centrosome and nuclear size control, cell polarity, and growth of flagella.
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Affiliation(s)
- Nathan W Goehring
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany.
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113
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Coon TA, Glasser JR, Mallampalli RK, Chen BB. Novel E3 ligase component FBXL7 ubiquitinates and degrades Aurora A, causing mitotic arrest. Cell Cycle 2012; 11:721-9. [PMID: 22306998 DOI: 10.4161/cc.11.4.19171] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Aurora family kinases play pivotal roles in several steps during mitosis. Specifically, Aurora A kinase is an important regulator of bipolar mitotic spindle formation and chromosome segregation. Like other members of the Aurora family, Aurora A kinase is also regulated by post-translational modifications. Here, we show that a previously undescribed E3 ligase component belonging to the SCF (Skp-Cullin1-F-box protein) E3 ligase family, SCFFBXL7, impairs cell proliferation by mediating Aurora A polyubiquitination and degradation. Both Aurora A and FBXL7 co-localize within the centrosome during spindle formation. FBXL7 ectopic expression led to G(2)/M phase arrest in transformed epithelia, resulting in the appearance of tetraploidy and mitotic arrest with circular monopolar spindles and multipolar spindle formation. Interestingly, FBXL7 specifically interacts with Aurora A during mitosis but not in interphase, suggesting a regulatory role for FBXL7 in controlling Aurora A abundance during mitosis.
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Affiliation(s)
- Tiffany A Coon
- Department of Medicine, Acute Lung Injury Center of Excellence, University of Pittsburgh, Pittsburgh, PA, USA
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114
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Brito DA, Gouveia SM, Bettencourt-Dias M. Deconstructing the centriole: structure and number control. Curr Opin Cell Biol 2012; 24:4-13. [PMID: 22321829 DOI: 10.1016/j.ceb.2012.01.003] [Citation(s) in RCA: 100] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Revised: 01/02/2012] [Accepted: 01/07/2012] [Indexed: 11/18/2022]
Abstract
Centrioles are very small microtubule-based organelles essential for centrosome, cilia and flagella assembly, which are involved in a variety of cellular and developmental processes. Although the centriole was first described almost a century ago, the knowledge on its assembly mechanism remains poor. In the past decade, forefront functional studies have provided important data on the different players involved in centriole biogenesis. Centriole research has now started to profit from highly sensitive structural, imaging, and biochemical techniques that are unveiling how those players contribute to assemble such a small and complex structure. We will review those studies and discuss how this field will increasingly benefit from the newborn and exciting era of super resolution analyses.
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Affiliation(s)
- Daniela A Brito
- Instituto Gulbenkian de Ciência, Rua da Quinta Grande, 6, P-2780-156 Oeiras, Portugal
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115
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Al-Hakim AK, Bashkurov M, Gingras AC, Durocher D, Pelletier L. Interaction proteomics identify NEURL4 and the HECT E3 ligase HERC2 as novel modulators of centrosome architecture. Mol Cell Proteomics 2012; 11:M111.014233. [PMID: 22261722 DOI: 10.1074/mcp.m111.014233] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Centrosomes are composed of a centriole pair surrounded by an intricate proteinaceous matrix referred to as pericentriolar material. Although the mechanisms underpinning the control of centriole duplication are now well understood, we know relatively little about the control of centrosome size and shape. Here we used interaction proteomics to identify the E3 ligase HERC2 and the neuralized homologue NEURL4 as novel interaction partners of the centrosomal protein CP110. Using high resolution imaging, we find that HERC2 and NEURL4 localize to the centrosome and that interfering with their function alters centrosome morphology through the appearance of aberrant filamentous structures that stain for a subset of pericentriolar material proteins including pericentrin and CEP135. Using an RNA interference-resistant transgene approach in combination with structure-function analyses, we show that the association between CP110 and HERC2 depends on nonoverlapping regions of NEURL4. Whereas CP110 binding to NEURL4 is dispensable for the regulation of pericentriolar material architecture, its association with HERC2 is required to maintain normal centrosome integrity. NEURL4 is a substrate of HERC2, and together these results indicate that the NEURL4-HERC2 complex participates in the ubiquitin-dependent regulation of centrosome architecture.
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Affiliation(s)
- Abdallah K Al-Hakim
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario M5G 1X5, Canada
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116
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Mahen R, Venkitaraman AR. Pattern formation in centrosome assembly. Curr Opin Cell Biol 2012; 24:14-23. [PMID: 22245706 DOI: 10.1016/j.ceb.2011.12.012] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Revised: 12/21/2011] [Accepted: 12/23/2011] [Indexed: 01/01/2023]
Abstract
A striking but poorly explained feature of cell division is the ability to assemble and maintain organelles not bounded by membranes, from freely diffusing components in the cytosol. This process is driven by information transfer across biological scales such that interactions at the molecular scale allow pattern formation at the scale of the organelle. One important example of such an organelle is the centrosome, which is the main microtubule organising centre in the cell. Centrosomes consist of two centrioles surrounded by a cloud of proteins termed the pericentriolar material (PCM). Profound structural and proteomic transitions occur in the centrosome during specific cell cycle stages, underlying events such as centrosome maturation during mitosis, in which the PCM increases in size and microtubule nucleating capacity. Here we use recent insights into the spatio-temporal behaviour of key regulators of centrosomal maturation, including Polo-like kinase 1, CDK5RAP2 and Aurora-A, to propose a model for the assembly and maintenance of the PCM through the mobility and local interactions of its constituent proteins. We argue that PCM structure emerges as a pattern from decentralised self-organisation through a reaction-diffusion mechanism, with or without an underlying template, rather than being assembled from a central structural template alone. Self-organisation of this kind may have broad implications for the maintenance of mitotic structures, which, like the centrosome, exist stably as supramolecular assemblies on the micron scale, based on molecular interactions at the nanometer scale.
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Affiliation(s)
- Robert Mahen
- The Medical Research Council Cancer Cell Unit, Hutchison/MRC Research Centre, Hills Road, Cambridge, CB2 OXZ, United Kingdom.
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117
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Silverman JS, Skaar JR, Pagano M. SCF ubiquitin ligases in the maintenance of genome stability. Trends Biochem Sci 2011; 37:66-73. [PMID: 22099186 DOI: 10.1016/j.tibs.2011.10.004] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Revised: 10/10/2011] [Accepted: 10/19/2011] [Indexed: 10/15/2022]
Abstract
In response to genotoxic stress, eukaryotic cells activate the DNA damage response (DDR), a series of pathways that coordinate cell cycle arrest and DNA repair to prevent deleterious mutations. In addition, cells possess checkpoint mechanisms that prevent aneuploidy by regulating the number of centrosomes and spindle assembly. Among these mechanisms, ubiquitin-mediated degradation of key proteins has an important role in the regulation of the DDR, centrosome duplication and chromosome segregation. This review discusses the functions of a group of ubiquitin ligases, the SCF (SKP1-CUL1-F-box protein) family, in the maintenance of genome stability. Given that general proteasome inhibitors are currently used as anticancer agents, a better understanding of the ubiquitylation of specific targets by specific ubiquitin ligases may result in improved cancer therapeutics.
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Affiliation(s)
- Joshua S Silverman
- Department of Radiation Oncology, New York University School of Medicine, 522 First Avenue, Smilow Research Building 1107, New York, NY 10016, USA
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118
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Sir JH, Barr AR, Nicholas AK, Carvalho OP, Khurshid M, Sossick A, Reichelt S, D’Santos C, Woods CG, Gergely F. A primary microcephaly protein complex forms a ring around parental centrioles. Nat Genet 2011; 43:1147-53. [PMID: 21983783 PMCID: PMC3299569 DOI: 10.1038/ng.971] [Citation(s) in RCA: 171] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2011] [Accepted: 09/14/2011] [Indexed: 12/12/2022]
Abstract
Autosomal recessive primary microcephaly (MCPH) is characterized by a substantial reduction in prenatal human brain growth without alteration of the cerebral architecture and is caused by biallelic mutations in genes coding for a subset of centrosomal proteins. Although at least three of these proteins have been implicated in centrosome duplication, the nature of the centrosome dysfunction that underlies the neurodevelopmental defect in MCPH is unclear. Here we report a homozygous MCPH-causing mutation in human CEP63. CEP63 forms a complex with another MCPH protein, CEP152, a conserved centrosome duplication factor. Together, these two proteins are essential for maintaining normal centrosome numbers in cells. Using super-resolution microscopy, we found that CEP63 and CEP152 co-localize in a discrete ring around the proximal end of the parental centriole, a pattern specifically disrupted in CEP63-deficient cells derived from patients with MCPH. This work suggests that the CEP152-CEP63 ring-like structure ensures normal neurodevelopment and that its impairment particularly affects human cerebral cortex growth.
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Affiliation(s)
- Joo-Hee Sir
- Cancer Research UK Cambridge Research Institute Li Ka Shing Centre Robinson Way Cambridge CB2 0RE UK
- Department of Oncology University of Cambridge Cambridge UK
| | - Alexis R. Barr
- Cancer Research UK Cambridge Research Institute Li Ka Shing Centre Robinson Way Cambridge CB2 0RE UK
- Department of Oncology University of Cambridge Cambridge UK
| | - Adeline K. Nicholas
- Department of Medical Genetics Cambridge Institute for Medical Research University of Cambridge Cambridge CB2 0XY UK
| | - Ofelia P. Carvalho
- Department of Medical Genetics Cambridge Institute for Medical Research University of Cambridge Cambridge CB2 0XY UK
| | - Maryam Khurshid
- Department of Medical Genetics Cambridge Institute for Medical Research University of Cambridge Cambridge CB2 0XY UK
| | - Alex Sossick
- Gurdon Institute Tennis Court Road Cambridge CB2 1QN UK
| | - Stefanie Reichelt
- Cancer Research UK Cambridge Research Institute Li Ka Shing Centre Robinson Way Cambridge CB2 0RE UK
| | - Clive D’Santos
- Cancer Research UK Cambridge Research Institute Li Ka Shing Centre Robinson Way Cambridge CB2 0RE UK
| | - C. Geoffrey Woods
- Department of Medical Genetics Cambridge Institute for Medical Research University of Cambridge Cambridge CB2 0XY UK
| | - Fanni Gergely
- Cancer Research UK Cambridge Research Institute Li Ka Shing Centre Robinson Way Cambridge CB2 0RE UK
- Department of Oncology University of Cambridge Cambridge UK
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The centrosome cycle: Centriole biogenesis, duplication and inherent asymmetries. Nat Cell Biol 2011; 13:1154-60. [PMID: 21968988 DOI: 10.1038/ncb2345] [Citation(s) in RCA: 440] [Impact Index Per Article: 33.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Centrosomes are microtubule-organizing centres of animal cells. They influence the morphology of the microtubule cytoskeleton, function as the base for the primary cilium and serve as a nexus for important signalling pathways. At the core of a typical centrosome are two cylindrical microtubule-based structures termed centrioles, which recruit a matrix of associated pericentriolar material. Cells begin the cell cycle with exactly one centrosome, and the duplication of centrioles is constrained such that it occurs only once per cell cycle and at a specific site in the cell. As a result of this duplication mechanism, the two centrioles differ in age and maturity, and thus have different functions; for example, the older of the two centrioles can initiate the formation of a ciliary axoneme. We discuss spatial aspects of the centrosome duplication cycle, the mechanism of centriole assembly and the possible consequences of the inherent asymmetry of centrioles and centrosomes.
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Abstract
Regulatory mechanisms to prevent centriole overduplication during the cell cycle are not completely understood. In this issue, FBXW5 is shown to control the degradation of the centriole assembly factor HsSAS-6. Moreover, the study proposes that FBXW5 is a substrate of both PLK4 and APC/C, two established regulators of centriole duplication.
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