Asterless is a scaffold for the onset of centriole assembly

Cancer Research UK Cell Cycle Genetics Group, University of Cambridge, Department of Genetics, Downing Street, Cambridge CB2 3EH, UK.
Nature (Impact Factor: 41.46). 10/2010; 467(7316):714-8. DOI: 10.1038/nature09445
Source: PubMed

ABSTRACT Centrioles are found in the centrosome core and, as basal bodies, at the base of cilia and flagella. Centriole assembly and duplication is controlled by Polo-like-kinase 4 (Plk4): these processes fail if Plk4 is downregulated and are promoted by Plk4 overexpression. Here we show that the centriolar protein Asterless (Asl; human orthologue CEP152) provides a conserved molecular platform, the amino terminus of which interacts with the cryptic Polo box of Plk4 whereas the carboxy terminus interacts with the centriolar protein Sas-4 (CPAP in humans). Drosophila Asl and human CEP152 are required for the centrosomal loading of Plk4 in Drosophila and CPAP in human cells, respectively. Depletion of Asl or CEP152 caused failure of centrosome duplication; their overexpression led to de novo centriole formation in Drosophila eggs, duplication of free centrosomes in Drosophila embryos, and centrosome amplification in cultured Drosophila and human cells. Overexpression of a Plk4-binding-deficient mutant of Asl prevented centriole duplication in cultured cells and embryos. However, this mutant protein was able to promote microtubule organizing centre (MTOC) formation in both embryos and oocytes. Such MTOCs had pericentriolar material and the centriolar protein Sas-4, but no centrioles at their core. Formation of such acentriolar MTOCs could be phenocopied by overexpression of Sas-4 in oocytes or embryos. Our findings identify independent functions for Asl as a scaffold for Plk4 and Sas-4 that facilitates self-assembly and duplication of the centriole and organization of pericentriolar material.

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Available from: David M Glover, Mar 12, 2014
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    • "The accumulation of the PCM typically initiates at the proximal end of the mother centriole and increases in size as cells transverse from interphase to mitosis (Palazzo et al., 2000). While a growing list of proteins, including Aurora-A (Hannak et al., 2001), PLK1 (Blagden and Glover, 2003), CDK5RAP2 (Lizarraga et al., 2010; Megraw et al., 1999), PCNT (Lee and Rhee, 2011; Zimmerman et al., 2004), SAS-4 (Kirkham et al., 2003; Kohlmaier et al., 2009), CEP152 (Dzhindzhev et al., 2010; Firat-Karalar et al., 2014), and SPD2 (Gomez-Ferreria et al., 2007), are found to participate in the PCM assembly and in centrosome biogenesis, the molecular architecture of the PCM and the mechanisms governing PCM assembly and centriole biogenesis are not clear. "
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    ABSTRACT: Although it is known that the centrioles play instructive roles in pericentriolar material (PCM) assembly and that the PCM is essential for proper centriole formation, the mechanism that governs centriole-PCM interaction is poorly understood. Here, we show that ATF5 forms a characteristic 9-fold symmetrical ring structure in the inner layer of the PCM outfitting the proximal end of the mother centriole. ATF5 controls the centriole-PCM interaction in a cell-cycle- and centriole-age-dependent manner. Interaction of ATF5 with polyglutamylated tubulin (PGT) on the mother centriole and with PCNT in the PCM renders ATF5 as a required molecule in mother centriole-directed PCM accumulation and in PCM-dependent centriole formation. ATF5 depletion blocks PCM accumulation at the centrosome and causes fragmentation of centrioles, leading to the formation of multi-polar mitotic spindles and genomic instability. These data show that ATF5 is an essential structural protein that is required for the interaction between the mother centriole and the PCM. Copyright © 2015 Elsevier Inc. All rights reserved.
    Cell 07/2015; 162(3). DOI:10.1016/j.cell.2015.06.055 · 32.24 Impact Factor
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    • "If not, then perhaps the multiple functions of Asl have been divided between Cep152 and Cep192, with Cep192 performing the functions allocated to Asl-C. Asl overexpression induces centriole amplification (Dzhindzhev et al., 2010; Stevens et al., 2010). Our experiments have revealed several new properties of Asl that better explain the control Asl exerts on centriole numbers. "
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    ABSTRACT: Plk4 (Polo-like kinase 4) and its binding partner Asterless (Asl) are essential, conserved centriole assembly factors that induce centriole amplification when overexpressed. Previous studies found that Asl acts as a scaffolding protein; its N terminus binds Plk4's tandem Polo box cassette (PB1-PB2) and targets Plk4 to centrioles to initiate centriole duplication. However, how Asl overexpression drives centriole amplification is unknown. In this paper, we investigated the Asl-Plk4 interaction in Drosophila melanogaster cells. Surprisingly, the N-terminal region of Asl is not required for centriole duplication, but a previously unidentified Plk4-binding domain in the C terminus is required. Mechanistic analyses of the different Asl regions revealed that they act uniquely during the cell cycle: the Asl N terminus promotes Plk4 homodimerization and autophosphorylation during interphase, whereas the Asl C terminus stabilizes Plk4 during mitosis. Therefore, Asl affects Plk4 in multiple ways to regulate centriole duplication. Asl not only targets Plk4 to centrioles but also modulates Plk4 stability and activity, explaining the ability of overexpressed Asl to drive centriole amplification.
    The Journal of Cell Biology 02/2015; 208(16):401-414. DOI:10.1083/jcb.201410105 · 9.83 Impact Factor
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    • "Moreover, Sas-4 null mutant flies show a reduction of PCM components in testes (Gopalakrishnan et al. 2011, 2012). This reflects the ability of Sas-4 to form complexes with CNN and Dplp; centrosomes with mutant Sas-4 unable to form such complexes have reduced PCM (Dzhindzhev et al. 2010; Gopalakrishnan et al. 2011). A double mutation in Sas-4 protein sequence that abolishes its binding to tubulin enhances centrosomal protein complex formation leading to abnormally large centrosomes and asters (Gopalakrishnan et al. 2012). "
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    ABSTRACT: The centrosome was discovered in the late 19th century when mitosis was first described. Long recognized as a key organelle of the spindle pole, its core component, the centriole, was realized more than 50 or so years later also to comprise the basal body of the cilium. Here, we chart the more recent acquisition of a molecular understanding of centrosome structure and function. The strategies for gaining such knowledge were quickly developed in the yeasts to decipher the structure and function of their distinctive spindle pole bodies. Only within the past decade have studies with model eukaryotes and cultured cells brought a similar degree of sophistication to our understanding of the centrosome duplication cycle and the multiple roles of this organelle and its component parts in cell division and signaling. Now as we begin to understand these functions in the context of development, the way is being opened up for studies of the roles of centrosomes in human disease. Copyright © 2015 Cold Spring Harbor Laboratory Press; all rights reserved.
    Cold Spring Harbor Perspectives in Medicine 02/2015; 7(1-2). DOI:10.1101/cshperspect.a015800 · 9.47 Impact Factor
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