scholarly journals A two-step mechanism for the inactivation of microtubule organizing center function at the centrosome

2018 ◽  
Author(s):  
Jérémy Magescas ◽  
Jennifer C. Zonka ◽  
Jessica L. Feldman
Keyword(s):  
Cell Cycle ◽  
Mitotic Spindle ◽  
Microtubule Organizing Center ◽  
Step Process ◽  
C Elegans ◽  
Pulling Forces ◽  
Organizing Center ◽  
Pericentriolar Material ◽  
And Behavior ◽  
Step Mechanism

SummaryDuring mitosis, the centrosome acts as a microtubule organizing center (MTOC), orchestrating microtubules into the mitotic spindle through its pericentriolar material (PCM). This activity is biphasic, cycling through assembly and disassembly during the cell cycle. Although hyperactive centrosomal MTOC activity is a hallmark of some cancers, little is known about how the centrosome is inactivated as an MTOC. Analysis of endogenous PCM proteins in C. elegans revealed that the PCM is composed of distinct protein territories that are removed from the centrosome at different rates and using different behaviors. Inhibition of PP2A phosphatases stabilized the PCM and perturbation of cortical pulling forces altered the timing and behavior by which proteins were removed from the centrosome. These data indicate that PCM disassembly is a two-step process, beginning with a phosphatase-dependent dissolution of PCM proteins followed by the ejection of ruptured PCM by cortical forces, ultimately inactivating MTOC function at the centrosome.

scholarly journals A two-step mechanism for the inactivation of microtubule organizing center function at the centrosome

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Jérémy Magescas ◽  
Jenny C Zonka ◽  
Jessica L Feldman
Keyword(s):  
Cell Cycle ◽  
Mitotic Spindle ◽  
Outer Sphere ◽  
Microtubule Organizing Center ◽  
C Elegans ◽  
Mitotic Kinases ◽  
Pulling Forces ◽  
Organizing Center ◽  
Pericentriolar Material ◽  
Step Mechanism

The centrosome acts as a microtubule organizing center (MTOC), orchestrating microtubules into the mitotic spindle through its pericentriolar material (PCM). This activity is biphasic, cycling through assembly and disassembly during the cell cycle. Although hyperactive centrosomal MTOC activity is a hallmark of some cancers, little is known about how the centrosome is inactivated as an MTOC. Analysis of endogenous PCM proteins in C. elegans revealed that the PCM is composed of partially overlapping territories organized into an inner and outer sphere that are removed from the centrosome at different rates and using different behaviors. We found that phosphatases oppose the addition of PCM by mitotic kinases, ultimately catalyzing the dissolution of inner sphere PCM proteins at the end of mitosis. The nature of the PCM appears to change such that the remaining aging PCM outer sphere is mechanically ruptured by cortical pulling forces, ultimately inactivating MTOC function at the centrosome.

CEP110 and ninein are located in a specific domain of the centrosome associated with centrosome maturation

2002 ◽  
Vol 115 (9) ◽  
pp. 1825-1835 ◽  
Author(s):  
Young Y. Ou ◽  
Gary J. Mack ◽  
Meifeng Zhang ◽  
Jerome B. Rattner
Keyword(s):  
Cell Cycle ◽  
Protein Interactions ◽  
Protein Function ◽  
Similar Distribution ◽  
Microtubule Organizing Center ◽  
Specific Domain ◽  
The Reformation ◽  
Mother And Daughter ◽  
Organizing Center ◽  
Pericentriolar Material

The mammalian centrosome consists of a pair of centrioles surrounded by pericentriolar material (PCM). The architecture and composition of the centrosome, especially the PCM, changes during the cell cycle. Recently, a subset of PCM proteins have been shown to be arranged in a tubular conformation with an open and a closed end within the centrosome. The presence of such a specific configuration can be used as a landmark for mapping proteins in both a spatial and a temporal fashion. Such mapping studies can provide information about centrosome organization, protein dynamics,protein-protein interactions as well as protein function. In this study, the centrosomal proteins CEP110 and ninein were mapped in relationship to the tubular configuration. Both proteins were found to exhibit a similar distribution pattern. In the mother centrosome, they were found at both ends of the centrosome tube, including the site of centrosome duplication. However,in the daughter centrosome they were present only at the closed end. At the closed end of the mother and daughter centrosome tube, both CEP110 and ninein co-localized with the centriolar protein CEP250/c-Nap1, which confirms ninein's centriole association and places CEP110 in association with this structure. Importantly, the appearance of CEP110 and ninein at the open end of the daughter centrosome occurred during the telophase-G1 transition of the next cell cycle, concomitant with the maturation of the daughter centrosome into a mother centrosome. Microinjection of antibodies against either CEP110 or ninein into metaphase HeLa cells disrupted the reformation of the tubular conformation of proteins within the centrosome following cell division and consequently led to dispersal of centrosomal material throughout the cytosol. Further, microinjection of antibodies to either CEP110 or ninein into metaphase PtK2 cells not only disrupted the tubular configuration within the centrosome but also affected the centrosome's ability to function as a microtubule organizing center (MTOC). This MTOC function was also disrupted when the antibodies were injected into postmitotic cells. Taken together, our results indicate that: (1) a population of CEP110 and ninein is located in a specific domain within the centrosome, which corresponds to the open end of the centrosome tube and is the site of protein addition associated with maturation of a daughter centrosome into a mother centrosome; and (2) the addition of CEP110 and ninein are essential for the reformation of specific aspects of the interphase centrosome architecture following mitosis as well as being required for the centrosome to function as a MTOC.

scholarly journals The centriolar satellite protein Cfap53/Ccdc11 facilitates the formation of the first zygotic microtubule organizing center in the zebrafish embryo

2020 ◽  
Author(s):  
Sven Willekers ◽  
Federico Tessadori ◽  
Babet van der Vaart ◽  
Heiko Henning ◽  
Riccardo Stucchi ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Danio Rerio ◽  
Mitotic Spindle ◽  
Sperm Cell ◽  
Zebrafish Embryo ◽  
Animal Species ◽  
Microtubule Organizing Center ◽  
Microtubule Network ◽  
Cell Divisions ◽  
Organizing Center

AbstractIn embryos from most animal species a zygotic centrosome is assembled by the centriole derived from the sperm cell and pericentriolar proteins present in the oocyte. This zygotic centrosome acts as a microtubule organizing center (MTOC) to assemble the mitotic spindle in the first and all subsequent cell divisions. As MTOC formation has been studied mainly in adult cells, very little is known about the formation of the first zygotic MTOC. Here we find that zebrafish (Danio rerio) embryos lacking maternal or paternal Cfap53, a centriolar satellite protein, arrest during the first cell cycle due to a failure in proper formation of the mitotic spindle. During the first cell cycle Cfap53 co-localizes with γ-tubulin and other centrosomal and centriolar satellite proteins to the very large MTOC. Furthermore, we find that γ-tubulin localization to the MTOC is impaired in the absence of Cfap53 or when the microtubule network is disrupted. Based on these results we propose a model in which maternal and paternal Cfap53 participates in the organization of the first zygotic MTOC of the embryo. Once the zygotic MTOC is formed, Cfap53 is dispensable for MTOC formation and integrity in subsequent cell divisions.

scholarly journals Breaking the ties that bind: New advances in centrosome biology

2012 ◽  
Vol 197 (1) ◽  
pp. 11-18 ◽  
Author(s):  
Balca R. Mardin ◽  
Elmar Schiebel
Keyword(s):  
Cell Cycle ◽  
Cancer Cells ◽  
Recent Work ◽  
Genomic Instability ◽  
Centrosome Duplication ◽  
Animal Cells ◽  
Microtubule Organizing Center ◽  
Centrosome Separation ◽  
Organizing Center ◽  
Pericentriolar Material

The centrosome, which consists of two centrioles and the surrounding pericentriolar material, is the primary microtubule-organizing center (MTOC) in animal cells. Like chromosomes, centrosomes duplicate once per cell cycle and defects that lead to abnormalities in the number of centrosomes result in genomic instability, a hallmark of most cancer cells. Increasing evidence suggests that the separation of the two centrioles (disengagement) is required for centrosome duplication. After centriole disengagement, a proteinaceous linker is established that still connects the two centrioles. In G2, this linker is resolved (centrosome separation), thereby allowing the centrosomes to separate and form the poles of the bipolar spindle. Recent work has identified new players that regulate these two processes and revealed unexpected mechanisms controlling the centrosome cycle.

scholarly journals A role for a novel centrosome cycle in asymmetric cell division

2007 ◽  
Vol 177 (1) ◽  
pp. 13-20 ◽  
Author(s):  
Nasser M. Rusan ◽  
Mark Peifer
Keyword(s):  
Asymmetric Cell Division ◽  
Asymmetric Division ◽  
Spindle Orientation ◽  
The Novel ◽  
Microtubule Organizing Center ◽  
Spindle Positioning ◽  
Central Brain ◽  
Organizing Center ◽  
Pericentriolar Material ◽  
Step Mechanism

Tissue stem cells play a key role in tissue maintenance. Drosophila melanogaster central brain neuroblasts are excellent models for stem cell asymmetric division. Earlier work showed that their mitotic spindle orientation is established before spindle formation. We investigated the mechanism by which this occurs, revealing a novel centrosome cycle. In interphase, the two centrioles separate, but only one is active, retaining pericentriolar material and forming a “dominant centrosome.” This centrosome acts as a microtubule organizing center (MTOC) and remains stationary, forming one pole of the future spindle. The second centriole is inactive and moves to the opposite side of the cell before being activated as a centrosome/MTOC. This is accompanied by asymmetric localization of Polo kinase, a key centrosome regulator. Disruption of centrosomes disrupts the high fidelity of asymmetric division. We propose a two-step mechanism to ensure faithful spindle positioning: the novel centrosome cycle produces a single interphase MTOC, coarsely aligning the spindle, and spindle–cortex interactions refine this alignment.

scholarly journals Centriole-less pericentriolar material serves as a microtubule organizing center at the base of C. elegans sensory cilia

2020 ◽  
Author(s):  
Jérémy Magescas ◽  
Sani Eskinazi ◽  
Michael V. Tran ◽  
Jessica L. Feldman
Keyword(s):  
Sensory Neurons ◽  
Super Resolution ◽  
Spatial Separation ◽  
Animal Cells ◽  
Microtubule Organizing Center ◽  
Tissue Specific ◽  
C Elegans ◽  
Organizing Center ◽  
Pericentriolar Material ◽  
Specific Degradation

SummaryDuring mitosis in animal cells, the centrosome acts as a microtubule organizing center (MTOC) to assemble the mitotic spindle. MTOC function at the centrosome is driven by proteins within the pericentriolar material (PCM), however the molecular complexity of the PCM makes it difficult to differentiate the proteins required for MTOC activity from other centrosomal functions. We used the natural spatial separation of PCM proteins during mitotic exit to identify a minimal module of proteins required for centrosomal MTOC function in C. elegans. Using tissue specific degradation, we show that SPD-5, the functional homolog of CDK5RAP2, is essential for embryonic mitosis while SPD-2/CEP192 and PCMD-1, which are essential in the zygote, are dispensable. Surprisingly, although the centriole is known to be degraded in the ciliated sensory neurons in C. elegans [1-3], we find evidence for “centriole-less PCM” at the base of cilia and use this structure as a minimal testbed to dissect centrosomal MTOC function. Super-resolution imaging revealed that this PCM inserts inside the lumen of the ciliary axoneme and directly nucleates the assembly of dendritic microtubules towards the cell body. Tissue-specific degradation in ciliated sensory neurons revealed a role for SPD-5 and the conserved microtubule nucleator γ-TuRC, but not SPD-2 or PCMD-1, in MTOC function at centriole-less PCM. This MTOC function was in the absence of regulation by mitotic kinases, highlighting the intrinsic ability of these proteins to drive microtubule growth and organization and further supporting a model that SPD-5 is the primary driver of MTOC function at the PCM.

γ-Tubulin and the fungal microtubule cytoskeleton

1995 ◽  
Vol 73 (S1) ◽  
pp. 352-358 ◽  
Author(s):  
Berl R. Oakley
Keyword(s):  
Cell Cycle ◽  
Mitotic Spindle ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Microtubule Organizing Center ◽  
Pole Body ◽  
Spindle Pole Bodies ◽  
Key Words Tubulin ◽  
Organizing Center ◽  
Chromosomal Condensation

γ-Tubulin is present in phylogenetically diverse eukaryotes. It is a component of microtubule organizing centers such as the spindle pole bodies of fungi. In Aspergillus nidulans and Schizosaccharomyces pombe, it is essential for nuclear division, and, thus, for viability. In A. nidulans, nuclei carrying a γ-tubulin disruption can be maintained in heterokaryons, and the phenotypes caused by the disruption can be determined in uninucleate spores produced by the heterokaryons. Experiments with heterokaryons created in strains with mutations that allow synchronization of the cell cycle reveal that γ-tubulin is not required for the transition from the G1 phase of the cell cycle through S phase to G2, nor for the entry into mitosis as judged by chromosomal condensation. It is, however, required for the formation of the mitotic spindle and for the successful completion of mitosis. Staining with the MPM-2 monoclonal antibody reveals that spindle pole body replication occurs in the absence of functional γ-tubulin. Finally, human γ-tubulin functions in fission yeast, and this indicates that γ-tubulin has similar functions in widely divergent organisms. Key words: tubulin, microtubule, spindle pole body, microtubule organizing center.

The Xenopus protein kinase pEg2 associates with the centrosome in a cell cycle-dependent manner, binds to the spindle microtubules and is involved in bipolar mitotic spindle assembly

1998 ◽  
Vol 111 (5) ◽  
pp. 557-572 ◽  
Author(s):  
C. Roghi ◽  
R. Giet ◽  
R. Uzbekov ◽  
N. Morin ◽  
I. Chartrain ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Protein Kinase ◽  
Mitotic Spindle ◽  
Cultured Cells ◽  
Dependent Manner ◽  
Egg Extracts ◽  
Pericentriolar Material ◽  
Spindle Microtubules ◽  
Cycle Dependent

By differential screening of a Xenopus laevis egg cDNA library, we have isolated a 2,111 bp cDNA which corresponds to a maternal mRNA specifically deadenylated after fertilisation. This cDNA, called Eg2, encodes a 407 amino acid protein kinase. The pEg2 sequence shows significant identity with members of a new protein kinase sub-family which includes Aurora from Drosophila and Ipl1 (increase in ploidy-1) from budding yeast, enzymes involved in centrosome migration and chromosome segregation, respectively. A single 46 kDa polypeptide, which corresponds to the deduced molecular mass of pEg2, is immunodetected in Xenopus oocyte and egg extracts, as well as in lysates of Xenopus XL2 cultured cells. In XL2 cells, pEg2 is immunodetected only in S, G2 and M phases of the cell cycle, where it always localises to the centrosomal region of the cell. In addition, pEg2 ‘invades’ the microtubules at the poles of the mitotic spindle in metaphase and anaphase. Immunoelectron microscopy experiments show that pEg2 is located precisely around the pericentriolar material in prophase and on the spindle microtubules in anaphase. We also demonstrate that pEg2 binds directly to taxol stabilised microtubules in vitro. In addition, we show that the presence of microtubules during mitosis is not necessary for an association between pEg2 and the centrosome. Finally we show that a catalytically inactive pEg2 kinase stops the assembly of bipolar mitotic spindles in Xenopus egg extracts.

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