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1
Obeng, George Yaw, Ebenezer Mensah et Richard Opoku. « Fabricators and End-Users of Single-Pot Biomass Stoves : Conceptualizing, Hypothesis and Performance Metrics for Developing Energy Sustainability Framework ». Sustainability 13, no 13 (24 juin 2021) : 7098. http://dx.doi.org/10.3390/su13137098.
Texte intégralRésumé :
In this study, interviewer-based questionnaires of 67 variables were administered to local fabricators and end-users of single-pot biomass stoves (SPBS) in Ghana. Additionally, two randomly selected traditional and improved SPBS were lab-tested using standard performance metrics. From the study, the relationship between fabricators and end-users was conceptualized based on selected indicators and assumptions. The study results indicated that the primary design resources for fabrication were patterns and templates, and that major challenges to fabrication were lack of training in design principles, standards and safety, poor emission efficiency and financial sustainability. Whereas end-users of improved SPBS were less affected by heat and smoke, end-users of traditional SPBS were mostly affected. From hypothesis test, because the calculated χ2cal = 24.05, and is greater than the tabulated χ2crit = 3.841, it is concluded that there is a relationship between heat, smoke effect and gender, and that female end-users of traditional SPBS were particularly affected during cooking. The traditional SPBS emitted more CO2 and CO than improved SPBS. Comparatively, 38% more end-users of traditional SPBS observed charcoal ash residue in the cooking area than improved SPBS users. Four basic practices of managing ashes from SPBS are developed. Finally, a fabricator and end-user framework are developed for energy sustainability and quality improvement.
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Uzawa, Satoru, Fei Li, Ye Jin, Kent L. McDonald, Michael B. Braunfeld, David A. Agard et W. Zacheus Cande. « Spindle Pole Body Duplication in Fission Yeast Occurs at the G1/S Boundary but Maturation Is Blocked until Exit from S by an Event Downstream of Cdc10+ ». Molecular Biology of the Cell 15, no 12 (décembre 2004) : 5219–30. http://dx.doi.org/10.1091/mbc.e04-03-0255.
Texte intégralRésumé :
The regulation and timing of spindle pole body (SPB) duplication and maturation in fission yeast was examined by transmission electron microscopy. When cells are arrested at G1 by nitrogen starvation, the SPB is unduplicated. On release from G1, the SPBs were duplicated after 1–2 h. In cells arrested at S by hydroxyurea, SPBs are duplicated but not mature. In G1 arrest/release experiments with cdc2.33 cells at the restrictive temperature, SPBs remained single, whereas in cells at the permissive temperature, SPBs were duplicated. In cdc10 mutant cells, the SPBs seem not only to be duplicated but also to undergo partial maturation, including invagination of the nuclear envelope underneath the SPB. There may be an S-phase–specific inhibitor of SPB maturation whose expression is under control of cdc10+. This model was examined by induction of overreplication of the genome by overexpression of rum1p or cdc18p. In cdc18p-overexpressing cells, the SPBs are duplicated but not mature, suggesting that cdc18p is one component of this feedback mechanism. In contrast, cells overexpressing rum1p have large, deformed SPBs accompanied by other features of maturation and duplication. We propose a feedback mechanism for maturation of the SPB that is coupled with exit from S to trigger morphological changes.
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Shen, Kuo-Fang, et Stephen A. Osmani. « Regulation of mitosis by the NIMA kinase involves TINA and its newly discovered partner, An-WDR8, at spindle pole bodies ». Molecular Biology of the Cell 24, no 24 (15 décembre 2013) : 3842–56. http://dx.doi.org/10.1091/mbc.e13-07-0422.
Texte intégralRésumé :
The NIMA kinase is required for mitotic nuclear pore complex disassembly and potentially controls other mitotic-specific events. To investigate this possibility, we imaged NIMA–green fluorescent protein (GFP) using four-dimensional spinning disk confocal microscopy. At mitosis NIMA-GFP locates to spindle pole bodies (SPBs), which contain Cdk1/cyclin B, followed by Aurora, TINA, and the BimC kinesin. NIMA promotes NPC disassembly in a spatially regulated manner starting near SPBs. NIMA is also required for TINA, a NIMA-interacting protein, to locate to SPBs during initiation of mitosis, and TINA is then necessary for locating NIMA back to SPBs during mitotic progression. To help expand the NIMA-TINA pathway, we affinity purified TINA and found it to uniquely copurify with An-WDR8, a WD40-domain protein conserved from humans to plants. Like TINA, An-WDR8 accumulates within nuclei during G2 but disperses from nuclei before locating to mitotic SPBs. Without An-WDR8, TINA levels are greatly reduced, whereas TINA is necessary for mitotic targeting of An-WDR8. Finally, we show that TINA is required to anchor mitotic microtubules to SPBs and, in combination with An-WDR8, for successful mitosis. The findings provide new insights into SPB targeting and indicate that the mitotic microtubule-anchoring system at SPBs involves WDR8 in complex with TINA.
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Boyas, Javier Francisco, Jana L. Woodiwiss et Vinayak K. Nahar. « Examining intentions to engage in sun protective behaviors among Latino day laborers : An application of the theory of planned behavior ». Health Promotion Perspectives 11, no 3 (18 août 2021) : 351–59. http://dx.doi.org/10.34172/hpp.2021.45.
Texte intégralRésumé :
Background: The past two decades has revealed an unprecedented increasing incidence of skin cancer within the Latinx population. Although Latino day laborers (LDLs) are at heightened risk for developing skin cancer because of the outdoor work in which they engage, there is limited research examining their intentions to engage in sun protective behaviors (SPBs). Therefore, this study sought to assess the explanatory power of the theory of planned behavior (TPB) to identify attitudinal, subjective norms, and perceived behavioral control factors associated with intentions to engage in SPB among LDLs. Methods: This cross-sectional retrospective study consists of a non-random convenience,community-based, sample of 137 LDLs residing in Mississippi and Illinois. Data were collected using a self-report survey centered on health practices and sun-protective behaviors. Results: Findings revealed that five significant factors shaped intentions to engage in SPBs, including barriers to engaging in SPBs (β =.30, P<0.001), benefits of engaging in SPBs (β =.27,P<0.001), education (β=0.20, P<0.01), and acculturation (β=0.18, P≤0.05). The independent variables tested in the model accounted for 42% of the change in intentions to engage in SPBs. Conclusion: This study demonstrates TPB’s usefulness for predicting future intentions to engage in SPBs among LDLs. Moreover, the strongest factor associated with predicting intentions to engage in SPBs among LDLs was perceived behavioral control. Thus, since SPBs are malleable, emphasis is placed on implementing interventions for this population that promote intentions and address perceived behavioral control.
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Goates, Blair J., et James A. Hoffmann. « Spindle pole body fusion in the smut fungus Tilletia foetida ». Canadian Journal of Botany 64, no 6 (1 juin 1986) : 1221–23. http://dx.doi.org/10.1139/b86-166.
Texte intégralRésumé :
Fusion of double-structured, interphase spindle pole bodies (SPBs) occurred before nuclear fusion in heterokaryotic secondary sporidia. The SPBs of two separate nuclei were juxtaposed with their long axes perpendicular to each other. Also, SPBs were observed oriented with their long axes parallel and fused to each other at both ends. Fusion apparently continued toward the midportion of the SPBs. Nuclei were observed joined together in a narrow region. These nuclei appeared to share a single SPB that was located opposite to a protuberance on both nuclei. Following fusion, the SPB apparently returned to an interphase structure.
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Wang, Linlin, Wenlei Zhu, Jianrong Zhang et Jun-Jie Zhu. « Miniaturized Microfluidic Electrochemical Biosensors Powered by Enzymatic Biofuel Cell ». Biosensors 13, no 2 (22 janvier 2023) : 175. http://dx.doi.org/10.3390/bios13020175.
Texte intégralRésumé :
Electrochemical biosensors, in which enzymatic biofuel cells simultaneously work as energy power and signal generators, have become a research hotspot. They display the merits of power self-support, a simplified structure, in vivo operational feasibility, online and timely monitoring, etc. Since the concept of enzymatic biofuel cell-powered biosensors (EBFC-SPBs) was first proposed, its applications in health monitoring have scored tremendous achievements. However, the creation and practical application of portable EBFC-SPBs are still impeded by the difficulty in their miniaturization. In recent years, the booming microfluidic technology has powerfully pushed forward the progress made in miniaturized and portable EBFC-SPBs. This brief review recalls and summarizes the achievements and progress made in miniaturized EBFC-SPBs. In addition, we also discuss the advantages and challenges that microfluidic and screen-printing technologies provide to wearable and disposable EBFC-SPBs.
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Nurjaman, Omay Komara, et Julia Julia. « Implementasi Pendidikan Karakter Lokal Kasundaan Berbasis Kebijakan SPBS di Kabupaten Sumedang Jawa Barat ». Mimbar Sekolah Dasar 5, no 1 (3 avril 2018) : 1. http://dx.doi.org/10.17509/mimbar-sd.v5i1.9292.
Texte intégralRésumé :
This study aims to analyze the implementation of policy on character education "kasundaan" based on regulation Sumedang Regent about "Sumedang Puseur Budaya Sunda " (SPBS)." The method used is a survey, which is completed with interview and FGD. The results from the study found that: (1) SPBS was only instructed in the "SKPD" environment only in the form of Thursday using "Kasumedangan" dress and Sundanese language, (2) no education design of "kasundaan" characters in elementary school, (3) majority of students elementary schools already have the expected behavior in the context of "kasundaan" values based on Bupati's regulation on SPBS. However, a few other minorities, in fact, show behavior that is not as expected, and this become a potential learner to lead to negative behavior. Thus, it can be concluded that the implementation of character education "kasundaan" in elementary school in Sumedang regency conducted without base to regent regulation about SPBS, but refers to school curriculum only. There is no integration between the regent's regulation on SPBS and the school curriculum, so the values of "kasundaan" characters in the regent's regulation on SPBS have not yet been implemented in a structured way at the elementary school level.
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Masuda, H., M. Sevik et WZ Cande. « In vitro microtubule-nucleating activity of spindle pole bodies in fission yeast Schizosaccharomyces pombe : cell cycle-dependent activation in xenopus cell-free extracts ». Journal of Cell Biology 117, no 5 (1 juin 1992) : 1055–66. http://dx.doi.org/10.1083/jcb.117.5.1055.
Texte intégralRésumé :
The spindle pole body (SPB) is the equivalent of the centrosome in fission yeast. In vivo it nucleates microtubules (MTs) during mitosis, but, unlike animal centrosomes, does not act as a microtubule organizing center (MTOC) during interphase. We have studied the MT-nucleating activity of SPBs in vitro and have found that SPBs in permeabilized cells retain in vivo characteristics. SPBs in cells permeabilized during mitosis can nucleate MTs, and are recognized by two antibodies: anti-gamma-tubulin and MPM-2 which recognizes phosphoepitopes. SPBs in cells permeabilized during interphase cannot nucleate MTs and are only recognized by anti-gamma-tubulin. Interphase SPBs which cannot nucleate can be converted to a nucleation competent state by incubation in cytostatic factor (CSF)-arrested Xenopus egg extracts. After incubation, they are recognized by MPM-2, and can nucleate MTs. The conversion does not occur in Xenopus interphase extract, but occurs in Xenopus interphase extract driven into mitosis by preincubation with exogenous cyclin B. The conversion is ATP dependent and inhibited by protein kinase inhibitors and alkaline phosphatase. Purified, active, cdc2 kinase/cyclin B complex in itself is not effective for activation of MT nucleation, although some interphase SPBs are now stained with MPM-2. These results suggest that the ability of SPBs in vitro to nucleate MTs after exposure to CSF-arrested extracts is activated through a downstream pathway which is regulated by cdc2 kinase.
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Hu, Zhiping, Xiaoli Wang, Weirong Wang, Zhenlong Zhang, Huiping Gao et Yanli Mao. « Raman spectroscopy for detecting supported planar lipid bilayers composed of ganglioside-GM1/sphingomyelin/cholesterol in the presence of amyloid-β ». Physical Chemistry Chemical Physics 17, no 35 (2015) : 22711–20. http://dx.doi.org/10.1039/c5cp02366a.
Texte intégral
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Clench, M. H., et J. R. Mathias. « A complex avian intestinal motility response to fasting ». American Journal of Physiology-Gastrointestinal and Liver Physiology 262, no 3 (1 mars 1992) : G498—G504. http://dx.doi.org/10.1152/ajpgi.1992.262.3.g498.
Texte intégralRésumé :
The rhythmic oscillating complex (ROC) is described from a series of experiments that surveyed the myoelectric activity of the avian small intestine as recorded from chronically implanted bipolar electrodes. A highly organized myoelectric event in the fasting avian small intestine, the ROC is demonstrated in detail in chickens (Gallus); it is also found in other gallinaceous birds but not in owls (Strix) or mammals. The ROC comprises rapidly propagating bursts of spike potentials (SPBs) that occur in a regular and predictable pattern: single orad SPBs alternate with groups of aborad SPBs. An average ROC in a chicken contains a mean of 78.9 +/- 2.0 (mean +/- SE) SPBs (37% orad, 63% aborad) that rapidly traverse the full length of the small intestine. The aborad SPBs move at mean velocities of 25.0 +/- 0.5 cm/s and last a mean of 0.9 +/- 0.0 s at an electrode site; the orad SPBs are faster (41.2 +/- 2.3 cm/s) and longer in duration (1.3 +/- 0.0 s). ROC activity continues for a mean of 7.6 +/- 0.2 min. ROCs occur only in a well-fasted gut as often as every 3 h and apparently for as long as the bird remains without food. Because ROCs restimulate fed-state activity in the stomach and small intestine, we hypothesize that they recycle nutritive material for further digestive activity in the distal tract.
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Shen, Jinlong, Tong Zhang, Jimin Xu, Xiaojun LIU et Kun Liu. « Experimental study on friction coefficient and temperature rise of heavy-load grease-lubricated spherical plain bearings with surface texture ». Industrial Lubrication and Tribology 73, no 3 (8 mars 2021) : 536–42. http://dx.doi.org/10.1108/ilt-08-2020-0293.
Texte intégralRésumé :
Purpose This paper aims to improve the tribological performance of grease-lubricated spherical plain bearings (SPBs) under heavy load, dimple-type textures were prepared by laser on the outer surface of the inner ring. The influence of roughness parameters of a textured surface on reducing friction coefficient and temperature rise was also explored. Design/methodology/approach This study adopts a laser processing method to fabricate dimple-type textures. Three-dimensional roughness parameters were used to characterize the textured surfaces. The friction coefficients of five SPBs with surface texture and one original commercially available SPB without surface texture under different nominal loads were measured on a self-established test rig. The data of temperature rise were obtained by nine embedded thermal couples. Findings The results indicate that SPBs with textures generally exhibit lower friction coefficients than the original SPB without textures. The dimple depth has a significant influence on improving the tribological performance, which coincides with the analysis by surface roughness parameters. A textured surface with negative Ssk and high Vvc has the minimum temperature rise. Originality/value As it is too difficult to arrange sensors into heavy-load SPBs, there are few reports about the temperature characteristics. Through nine embedded thermal couples, the distribution of temperature rise on the inner ring of SPBs was given in this study. The positive effect of surface texture on reducing temperature rise and friction coefficient was verified, which is beneficial for the design of heavy-load SPBs.
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Yoshizawa-Fujita, Masahiro, Jun Ishii, Yuko Takeoka et Masahiro Rikukawa. « Oligoether/Zwitterion Diblock Copolymers : Synthesis and Application as Cathode-Coating Material for Li Batteries ». Polymers 13, no 5 (5 mars 2021) : 800. http://dx.doi.org/10.3390/polym13050800.
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Poly (ethylene oxide) (PEO) has been investigated as an ion-conductive matrix for several decades due to its excellent properties. However, further improvements are needed to enable a PEO-based ion-conductive matrix for practical applications. In order to develop novel solid polymer electrolytes based on zwitterions, we synthesized diblock copolymers (PPEGMA-b-SPBs) with oligoether and zwitterionic side-chains and evaluated their physico-chemical properties. PPEGMA-b-SPBs with various unit ratios were synthesized by RAFT polymerization. PPEGMA-b-SPBs with/without LiTFSA exhibited two distinct glass transition temperatures regardless of the unit ratio of PEGMA and SPB. AFM observations clearly revealed phase-separated structures. The ionic conductivity of PPEGMA-b-SPBs increased even at a high salt concentrations such as [EO]:[Li] = 6:1 and was over 10−5 S cm−1 at 25 °C. This tendency is unusual in a PEO matrix. The oxidation stability of PPEGMA-b-SPBs was about 5.0 V vs. Li/Li+, which is a higher value than that of PEO. The improvement of the electrochemical properties is attributed to the introduction of the SPB block into the block copolymers. PPEGMA-b-SPBs were evaluated as cathode-coating materials for Li batteries. The discharge capacity and coulombic efficiency of the cells employing the cathode (LiNi1/3Mn1/3Co1/3O2 (NMC)) coated with the block copolymers were much higher than those of the cell employing the pristine cathode at the 50th cycle in the cut-off voltage range of 3.0–4.6 V.
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Tomlin, Gregory C., Jennifer L. Morrell et Kathleen L. Gould. « The Spindle Pole Body Protein Cdc11p Links Sid4p to the Fission Yeast Septation Initiation Network ». Molecular Biology of the Cell 13, no 4 (avril 2002) : 1203–14. http://dx.doi.org/10.1091/mbc.01-09-0455.
Texte intégralRésumé :
The Schizosaccharomyces pombe septation initiation network (SIN) signals the onset of cell division from the spindle pole body (SPB) and is regulated by the small GTPase Spg1p. The localization of SIN components including Spg1p to the SPB is required for cytokinesis and is dependent on Sid4p, a constitutive resident of SPBs. However, a direct interaction between Sid4p and other members of the SIN has not been detected. To understand how Sid4p is linked to other SIN components, we have begun to characterize an S. pombe homolog of the Saccharomyces cerevisiaeSPB protein Nud1p. We have determined that this S. pombeNud1p homolog corresponds to Cdc11p, a previously uncharacterized SIN element. We report that Cdc11p is present constitutively at SPBs and that its function appears to be required for the localization of all other SIN components to SPBs with the exception of Sid4p. The Cdc11p C terminus localizes the protein to SPBs in a Sid4p-dependent manner, and we demonstrate a direct Cdc11p-Sid4p interaction. The N-terminus of Cdc11p is required for Spg1p binding to SPBs. Our studies indicate that Cdc11p provides a physical link between Sid4p and the Spg1p signaling pathway.
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Ohta, Midori, Masamitsu Sato et Masayuki Yamamoto. « Spindle pole body components are reorganized during fission yeast meiosis ». Molecular Biology of the Cell 23, no 10 (15 mai 2012) : 1799–811. http://dx.doi.org/10.1091/mbc.e11-11-0951.
Texte intégralRésumé :
During meiosis, the centrosome/spindle pole body (SPB) must be regulated in a manner distinct from that of mitosis to achieve a specialized cell division that will produce gametes. In this paper, we demonstrate that several SPB components are localized to SPBs in a meiosis-specific manner in the fission yeast Schizosaccharomyces pombe. SPB components, such as Cut12, Pcp1, and Spo15, which stay on the SPB during the mitotic cell cycle, disassociate from the SPB during meiotic prophase and then return to the SPB immediately before the onset of meiosis I. Interestingly, the polo kinase Plo1, which normally localizes to the SPB during mitosis, is excluded from them in meiotic prophase, when meiosis-specific, horse-tail nuclear movement occurs. We found that exclusion of Plo1 during this period was essential to properly remodel SPBs, because artificial targeting of Plo1 to SPBs resulted in an overduplication of SPBs. We also found that the centrin Cdc31 was required for meiotic SPB remodeling. Thus Plo1 and a centrin play central roles in the meiotic SPB remodeling, which is essential for generating the proper number of meiotic SPBs and, thereby provide unique characteristics to meiotic divisions.
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West, Robert R., Elena V. Vaisberg, Rubai Ding, Paul Nurse et J. Richard McIntosh. « cut11 + : A Gene Required for Cell Cycle-dependent Spindle Pole Body Anchoring in the Nuclear Envelope and Bipolar Spindle Formation in Schizosaccharomyces pombe ». Molecular Biology of the Cell 9, no 10 (octobre 1998) : 2839–55. http://dx.doi.org/10.1091/mbc.9.10.2839.
Texte intégralRésumé :
The “cut” mutants of Schizosaccharomyces pombeare defective in spindle formation and/or chromosome segregation, but they proceed through the cell cycle, resulting in lethality. Analysis of temperature-sensitive alleles of cut11 +suggests that this gene is required for the formation of a functional bipolar spindle. Defective spindle structure was revealed with fluorescent probes for tubulin and DNA. Three-dimensional reconstruction of mutant spindles by serial sectioning and electron microscopy showed that the spindle pole bodies (SPBs) either failed to complete normal duplication or were free floating in the nucleoplasm. Localization of Cut11p tagged with the green fluorescent protein showed punctate nuclear envelope staining throughout the cell cycle and SPBs staining from early prophase to mid anaphase. This SPB localization correlates with the time in the cell cycle when SPBs are inserted into the nuclear envelope. Immunoelectron microscopy confirmed the localization of Cut11p to mitotic SPBs and nuclear pore complexes. Cloning and sequencing showed thatcut11 + encodes a novel protein with seven putative membrane-spanning domains and homology to theSaccharomyces cerevisiae gene NDC1. These data suggest that Cut11p associates with nuclear pore complexes and mitotic SPBs as an anchor in the nuclear envelope; this role is essential for mitosis.
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Helmstaedt, Kerstin, Karen Laubinger, Katja Voßkuhl, Özgür Bayram, Silke Busch, Michael Hoppert, Oliver Valerius, Stephan Seiler et Gerhard H. Braus. « The Nuclear Migration Protein NUDF/LIS1 Forms a Complex with NUDC and BNFA at Spindle Pole Bodies ». Eukaryotic Cell 7, no 6 (juin 2008) : 1041–52. http://dx.doi.org/10.1128/ec.00071-07.
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ABSTRACTNuclear migration depends on microtubules, the dynein motor complex, and regulatory components like LIS1 and NUDC. We sought to identify new binding partners of the fungal LIS1 homolog NUDF to clarify its function in dynein regulation. We therefore analyzed the association between NUDF and NUDC inAspergillus nidulans. NUDF and NUDC directly interacted in yeast two-hybrid experiments via NUDF's WD40 domain. NUDC-green fluorescent protein (NUDC-GFP) was localized to immobile dots in the cytoplasm and at the hyphal cortex, some of which were spindle pole bodies (SPBs). We showed by bimolecular fluorescence complementation microscopy that NUDC directly interacted with NUDF at SPBs at different stages of the cell cycle. Applying tandem affinity purification, we isolated the NUDF-associated protein BNFA (forbinding toNUDF). BNFA was dispensable for growth and for nuclear migration. GFP-BNFA fusions localized to SPBs at different stages of the cell cycle. This localization depended on NUDF, since the loss of NUDF resulted in the cytoplasmic accumulation of BNFA. BNFA did not bind to NUDC in a yeast two-hybrid assay. These results show that the conserved NUDF and NUDC proteins play a concerted role at SPBs at different stages of the cell cycle and that NUDF recruits additional proteins specifically to the dynein complex at SPBs.
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Botchkarev, Vladimir V., Mikael V. Garabedian, Brenda Lemos, Eric Paulissen et James E. Haber. « The budding yeast Polo-like kinase localizes to distinct populations at centrosomes during mitosis ». Molecular Biology of the Cell 28, no 8 (15 avril 2017) : 1011–20. http://dx.doi.org/10.1091/mbc.e16-05-0324.
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The budding yeast Polo-like kinase Cdc5 is a key regulator of many mitotic events. Cdc5 coordinates its functions spatially and temporally by changing its localization during the cell cycle: Cdc5 is imported into the nucleus in G2 phase and released to the cytoplasm in anaphase, where it accumulates at the bud neck. Cdc5 also localizes to the spindle pole bodies (SPBs) from S phase until the end of mitosis. Whether Cdc5 changes its SPB population during the cell cycle is not known. We find that Cdc5 localizes to distinct SPB subpopulations, depending on the mitotic stage. Cdc5 localizes to the nuclear side of the SPBs during metaphase and early anaphase and to the cytoplasmic surface of the SPBs during late anaphase. Cdc14 is necessary to relocalize Cdc5 from the nuclear SPB plaque. Accumulation of Cdc5 at the daughter SPB in late anaphase is controlled by Bfa1. We also show that Cdc5 and Bfa1 are found in spatially distinct locations at the SPBs during G2/M arrest after DNA damage. Collectively our data reveal that Cdc5 is a dynamic component of the SPBs during mitosis and provide new insight into its regulation during both late mitotic events and DNA damage–induced G2/M arrest.
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Lengefeld, Jette, Eric Yen, Xiuzhen Chen, Allen Leary, Jackie Vogel et Yves Barral. « Spatial cues and not spindle pole maturation drive the asymmetry of astral microtubules between new and preexisting spindle poles ». Molecular Biology of the Cell 29, no 1 (janvier 2018) : 10–28. http://dx.doi.org/10.1091/mbc.e16-10-0725.
Texte intégralRésumé :
In many asymmetrically dividing cells, the microtubule-organizing centers (MTOCs; mammalian centrosome and yeast spindle pole body [SPB]) nucleate more astral microtubules on one of the two spindle poles than the other. This differential activity generally correlates with the age of MTOCs and contributes to orienting the mitotic spindle within the cell. The asymmetry might result from the two MTOCs being in distinctive maturation states. We investigated this model in budding yeast. Using fluorophores with different maturation kinetics to label the outer plaque components of the SPB, we found that the Cnm67 protein is mobile, whereas Spc72 is not. However, these two proteins were rapidly as abundant on both SPBs, indicating that SPBs mature more rapidly than anticipated. Superresolution microscopy confirmed this finding for Spc72 and for the γ-tubulin complex. Moreover, astral microtubule number and length correlated with the subcellular localization of SPBs rather than their age. Kar9-dependent orientation of the spindle drove the differential activity of the SPBs in astral microtubule organization rather than intrinsic differences between the spindle poles. Together, our data establish that Kar9 and spatial cues, rather than the kinetics of SPB maturation, control the asymmetry of astral microtubule organization between the preexisting and new SPBs.
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Valerio-Santiago, Mauricio, et Fernando Monje-Casas. « Tem1 localization to the spindle pole bodies is essential for mitotic exit and impairs spindle checkpoint function ». Journal of Cell Biology 192, no 4 (14 février 2011) : 599–614. http://dx.doi.org/10.1083/jcb.201007044.
Texte intégralRésumé :
The mitotic exit network (MEN) is a signaling cascade that triggers inactivation of the mitotic cyclin-dependent kinases and exit from mitosis. The GTPase Tem1 localizes on the spindle pole bodies (SPBs) and initiates MEN signaling. Tem1 activity is inhibited until anaphase by Bfa1-Bub2. These proteins are also part of the spindle position checkpoint (SPOC), a surveillance mechanism that restrains mitotic exit until the spindle is correctly positioned. Here, we show that regulation of Tem1 localization is essential for the proper function of the MEN and the SPOC. We demonstrate that the dynamics of Tem1 loading onto SPBs determine the recruitment of other MEN components to this structure, and reevaluate the interdependence in the localization of Tem1, Bfa1, and Bub2. We also find that removal of Tem1 from the SPBs is critical for the SPOC to impede cell cycle progression. Finally, we demonstrate for the first time that localization of Tem1 to the SPBs is a requirement for mitotic exit.
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Hoffmann, James A., et Blair J. Goates. « Ultrastructure of mitosis and the spindle pole body cycle in the smut fungus, Tilletia foetida ». Canadian Journal of Botany 63, no 1 (1 janvier 1985) : 86–96. http://dx.doi.org/10.1139/b85-012.
Texte intégralRésumé :
The interphase nucleus in secondary sporidia of Tilletia foetida consists of mostly diffuse chromatin, one or two nucleoli, and an area of heterochromatin located opposite an electron-dense, extranuclear spindle pole body (SPB). The interphase SPB is an oval- to bar-shaped, double-structured disc that has a crystallinelike substructure. During nuclear migration into nascent sporidia, SPBs and nucleoli are randomly oriented. At the onset of division, chromatin begins to condense and the SPB becomes located on a nuclear protuberance. Cytoplasmic microtubules terminate at the SPBs and multivesicular bodies surround the SPBs from the early stages of SPB division to early postdivision. SPB discs become spheroid and each develops a medial, dense layer. Then, a basal, dense layer develops and elongates as the SPBs separate and become positioned on opposite sides of the nuclear protuberance. The nuclear membrane opens opposite the SPB during SPB division. The nucleolus is extruded into a nuclear bleb and degenerates. SPBs migrate to opposing sides of the nucleus and become diffuse as a microtubular spindle develops between them. Some spindle microtubules terminate at dense chromatin patches that are contiguous with the major mass of chromatin surrounding the spindle. During late division stages, spindle microtubules often appear to be closely juxtaposed. Except for polar openings adjacent to the SPBs, the nuclear membrane is entire until late division when it degenerates in the midregion of the nucleus. During early postdivision, the SPB condenses into a small, dense sphere as the chromatin and heterochromatin opposite the SPB become diffuse. The SPB then elongates into a dense bar and SPB material increases, except at the midportion, reforming the double structure of interphase.
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Chial, Heidi J., Michael P. Rout, Thomas H. Giddings et Mark Winey. « Saccharomyces cerevisiae Ndc1p Is a Shared Component of Nuclear Pore Complexes and Spindle Pole Bodies ». Journal of Cell Biology 143, no 7 (28 décembre 1998) : 1789–800. http://dx.doi.org/10.1083/jcb.143.7.1789.
Texte intégralRésumé :
We report a novel connection between nuclear pore complexes (NPCs) and spindle pole bodies (SPBs) revealed by our studies of the Saccharomyces cerevisiae NDC1 gene. Although both NPCs and SPBs are embedded in the nuclear envelope (NE) in yeast, their known functions are quite distinct. Previous work demonstrated that NDC1 function is required for proper SPB duplication (Winey, M., M.A. Hoyt, C. Chan, L. Goetsch, D. Botstein, and B. Byers. 1993. J. Cell Biol. 122:743–751). Here, we show that Ndc1p is a membrane protein of the NE that localizes to both NPCs and SPBs. Indirect immunofluorescence microscopy shows that Ndc1p displays punctate, nuclear peripheral localization that colocalizes with a known NPC component, Nup49p. Additionally, distinct spots of Ndc1p localization colocalize with a known SPB component, Spc42p. Immunoelectron microscopy shows that Ndc1p localizes to the regions of NPCs and SPBs that interact with the NE. The NPCs in ndc1-1 mutant cells appear to function normally at the nonpermissive temperature. Finally, we have found that a deletion of POM152, which encodes an abundant but nonessential nucleoporin, suppresses the SPB duplication defect associated with a mutation in the NDC1 gene. We show that Ndc1p is a shared component of NPCs and SPBs and propose a shared function in the assembly of these organelles into the NE.
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Visintin, Rosella, et Angelika Amon. « Regulation of the Mitotic Exit Protein Kinases Cdc15 and Dbf2 ». Molecular Biology of the Cell 12, no 10 (octobre 2001) : 2961–74. http://dx.doi.org/10.1091/mbc.12.10.2961.
Texte intégralRésumé :
In budding yeast, the release of the protein phosphatase Cdc14 from its inhibitor Cfi1/Net1 in the nucleolus during anaphase triggers the inactivation of Clb CDKs that leads to exit from mitosis. The mitotic exit pathway controls the association between Cdc14 and Cfi1/Net1. It is comprised of the RAS-like GTP binding protein Tem1, the exchange factor Lte1, the GTPase activating protein complex Bub2-Bfa1/Byr4, and several protein kinases including Cdc15 and Dbf2. Here we investigate the regulation of the protein kinases Dbf2 and Cdc15. We find that Cdc15 is recruited to both spindle pole bodies (SPBs) during anaphase. This recruitment depends on TEM1 but notDBF2 or CDC14 and is inhibited byBUB2. Dbf2 also localizes to SPBs during anaphase, which coincides with activation of Dbf2 kinase activity. Both events depend on the mitotic exit pathway components TEM1 andCDC15. In cells lacking BUB2, Dbf2 localized to SPBs in cell cycle stages other than anaphase and telophase and Dbf2 kinase was prematurely active during metaphase. Our results suggest an order of function of mitotic exit pathway components with respect to SPB localization of Cdc15 and Dbf2 and activation of Dbf2 kinase. BUB2 negatively regulates all 3 events. Loading of Cdc15 on SPBs depends on TEM1, whereas loading of Dbf2 on SPBs and activation of Dbf2 kinase depend onTEM1 and CDC15.
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Wang, Yunwei, Li Li, Yiming Wang, Qingsong Yang, Zhishuang Ye, Liang Sun, Fan Yang et Xuhong Guo. « Effect of Counterions on the Interaction among Concentrated Spherical Polyelectrolyte Brushes ». Polymers 13, no 12 (8 juin 2021) : 1911. http://dx.doi.org/10.3390/polym13121911.
Texte intégralRésumé :
The effect of counterions on interactions among spherical polyelectrolyte brushes (SPBs) was systematically investigated by rheology, small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS). The SPB particles consist of a solid polystyrene (PS) core with a diameter of ca.100 nm and a chemically grafted poly-(acrylic acid) (PAA) brush layer. Metal ions of different valences (Na+, Mg2+ and Al3+) were used as counterions to study the interactions among concentrated SPBs. The so-called “structure factor peak” in SAXS, the “local ordered structure peak” in WAXS and rheological properties indicated the interactions among concentrated SPBs. Combining SAXS, WAXS and rheology, the formation mechanism of the local ordered structure among PAA chains in the overlapped area of adjacent SPB, which was generated due to the bridge function of counterions, was confirmed. In contrast, excessive counterions shielded the electrostatic interaction among PAA chains and destroyed the local ordered structure. This work enriches our understanding of the polyelectrolyte assembly in concentrated SPBs under the effect of counterions and lays the foundations for SPB applications.
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von Fraunhofer, J. A. « Comments on the SPBS study ». American Journal of Orthodontics and Dentofacial Orthopedics 104, no 1 (juillet 1993) : 15A. http://dx.doi.org/10.1016/s0889-5406(08)80115-1.
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Vannini, Michael, Victoria R. Mingione, Ashleigh Meyer, Courtney Sniffen, Jenna Whalen et Anupama Seshan. « A Novel Hyperactive Nud1 Mitotic Exit Network Scaffold Causes Spindle Position Checkpoint Bypass in Budding Yeast ». Cells 11, no 1 (24 décembre 2021) : 46. http://dx.doi.org/10.3390/cells11010046.
Texte intégralRésumé :
Mitotic exit is a critical cell cycle transition that requires the careful coordination of nuclear positioning and cyclin B destruction in budding yeast for the maintenance of genome integrity. The mitotic exit network (MEN) is a Ras-like signal transduction pathway that promotes this process during anaphase. A crucial step in MEN activation occurs when the Dbf2-Mob1 protein kinase complex associates with the Nud1 scaffold protein at the yeast spindle pole bodies (SPBs; centrosome equivalents) and thereby becomes activated. This requires prior priming phosphorylation of Nud1 by Cdc15 at SPBs. Cdc15 activation, in turn, requires both the Tem1 GTPase and the Polo kinase Cdc5, but how Cdc15 associates with SPBs is not well understood. We have identified a hyperactive allele of NUD1, nud1-A308T, that recruits Cdc15 to SPBs in all stages of the cell cycle in a CDC5-independent manner. This allele leads to early recruitment of Dbf2-Mob1 during metaphase and requires known Cdc15 phospho-sites on Nud1. The presence of nud1-A308T leads to loss of coupling between nuclear position and mitotic exit in cells with mispositioned spindles. Our findings highlight the importance of scaffold regulation in signaling pathways to prevent improper activation.
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Rout, M. P., et J. V. Kilmartin. « Components of the yeast spindle and spindle pole body. » Journal of Cell Biology 111, no 5 (1 novembre 1990) : 1913–27. http://dx.doi.org/10.1083/jcb.111.5.1913.
Texte intégralRésumé :
Yeast spindle pole bodies (SPBs) with attached nuclear microtubles were enriched approximately 600-fold from yeast cell extracts. 14 mAbs prepared against this enriched SPB fraction define at least three components of the SPB and spindle. Immunofluorescent staining of yeast cells showed that throughout the cell cycle two of the components (110 and 90 kD) were localized exclusively to the SPB region, and the other (80 kD) was localized both to the SPB region and to particulate dots in short spindles. Immunoelectron microscopy confirmed and extended most of these findings. Thus the 110-kD component was localized to a layer in the SPB just to the nuclear side of the plane of the inner nuclear membrane. The 90-kD component was localized in a layer across the cytoplasmic face of intact SPBs, and, in SPBs where nuclear microtubules were removed by extraction with DEAE-dextran, the 90-kD component was also found in an inner nuclear layer close to where spindle microtubules emerge. In intact SPBs with attached nuclear microtubules the anit-80-kD mAb labels microtubules, particularly those close to the SPB. These results begin to provide a preliminary molecular map of the SPB and should also enable the corresponding genes to be isolated.
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Bauer, Robert, Mary L. Berbee et Franz Oberwinkler. « An electron microscopic study of meiosis and the spindle pole body cycle in the smut fungus Sphacelotheca polygoni-serrulati ». Canadian Journal of Botany 69, no 2 (1 février 1991) : 245–55. http://dx.doi.org/10.1139/b91-035.
Texte intégralRésumé :
An electron microscopic study was made of meiosis and the meiotic spindle pole body (SPB) cycle in germinating teliospores of the smut fungus Sphacelotheca polygoni-serrulati. SPB development in prophase I and duplication in interphase I were studied in detail. During prophase, the globular elements of the biglobular SPB enlarged, became oblate in form, developed internal layering, and became associated with astral microtubules. The middle piece decreased in size and finally disappeared. Prior to metaphase I, the two oblate elements moved apart along the intact surface of the nuclear envelope, and the nuclear membrane bulged into the space between the two SPBs. Metaphase I – early telophase I and metaphase II – early telophase II SPBs were intranuclear, oblate spheroidal in shape, and traversed by an electron-dense disc. In interphase I, an electron-dense bar appeared in association with the nuclear side of the original SPB. The bar initially overlapped one edge of the electron-dense disc and later appeared at the side of the disc. The bar became one of the metaphase II SPBs. Similarities and differences between meiosis and SPBs in Sphacelotheca polygoni-serrulati, Ustilago maydis, Ustilago esculenta, Tilletia foetida, and other heterobasidiomycetes are discussed. Key words: heterobasidiomycetes, Ustilaginales, Sphacelotheca, meiosis, spindle pole body, ultrastructure.
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Nickas, Mark E., Aviva E. Diamond, Min-Jay Yang et Aaron M. Neiman. « Regulation of Spindle Pole Function by an Intermediary Metabolite ». Molecular Biology of the Cell 15, no 6 (juin 2004) : 2606–16. http://dx.doi.org/10.1091/mbc.e04-02-0128.
Texte intégralRésumé :
Spore formation in the yeast Saccharomyces cerevisiae depends on a modification of spindle pole bodies (SPBs) at the onset of meiosis II that allows them to promote de novo membrane formation. Depletion of the environmental carbon source during sporulation results in modification of only one SPB from each meiosis II spindle and formation of a two-spored ascus, called a nonsister dyad (NSD). We have found that mutants impaired in the glyoxylate pathway, which is required for the conversion of acetate to glucose, make NSDs when acetate is the primary carbon source. Wild-type cells make NSDs when the carbon source is glycerol, which is converted to glucose independently of the glyoxylate pathway. During NSD formation in glycerol, only the two SPBs created at the meiosis I/II transition (“daughters”) are modified. In these conditions, the SPB components Mpc70p and Spo74p are not recruited to mother SPBs. Moreover, cooverexpression of Mpc70p and Spo74p suppresses NSD formation in glycerol. Our findings indicate that flux through the glyoxylate pathway during sporulation regulates modification of mother SPBs via recruitment of Mpc70p and Spo74p. These results define a cellular response in which the accumulation of an intermediary metabolite serves as a measure of biosynthetic capacity to regulate the number of daughter cells formed.
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Nurjaman, Omay Komara, et Julia Julia. « Implementasi Pendidikan Karakter Lokal Kasundaan Berbasis Kebijakan SPBS di Kabupaten Sumedang Jawa Barat ». Mimbar Sekolah Dasar 5, no 1 (3 avril 2018) : 1–15. http://dx.doi.org/10.53400/mimbar-sd.v5i1.9292.
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This study aims to analyze the implementation of policy on kasundaan character education based on Sumedang Regent regulation about Sumedang Puseur Budaya Sunda (SPBS). The method used was a survey to the elementary school students, which was completed with interviews and FGD. The results of the study found that: (1) SPBS was only instructed in the "SKPD" environment only in the form of Thursday using kasumedangan dress and Sundanese language, (2) no education design of kasundaan characters in elementary school, (3) the majority of elementary school students already have the expected behavior in the context of kasundaan values based on Regent's regulation on SPBS. However, a few other minorities, in fact, show the unexpected behavior that potentially leads the students to negative behavior. Thus, it can be concluded that the implementation of kasundaan character education in elementary school in Sumedang conducted only based school curriculum in spite of Regent’s regulation.
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Li, Ping, Yize Shao, Hui Jin et Hong-Guo Yu. « Ndj1, a telomere-associated protein, regulates centrosome separation in budding yeast meiosis ». Journal of Cell Biology 209, no 2 (20 avril 2015) : 247–59. http://dx.doi.org/10.1083/jcb.201408118.
Texte intégralRésumé :
Yeast centrosomes (called spindle pole bodies [SPBs]) remain cohesive for hours during meiotic G2 when recombination takes place. In contrast, SPBs separate within minutes after duplication in vegetative cells. We report here that Ndj1, a previously known meiosis-specific telomere-associated protein, is required for protecting SPB cohesion. Ndj1 localizes to the SPB but dissociates from it ∼16 min before SPB separation. Without Ndj1, meiotic SPBs lost cohesion prematurely, whereas overproduction of Ndj1 delayed SPB separation. When produced ectopically in vegetative cells, Ndj1 caused SPB separation defects and cell lethality. Localization of Ndj1 to the SPB depended on the SUN domain protein Mps3, and removal of the N terminus of Mps3 allowed SPB separation and suppressed the lethality of NDJ1-expressing vegetative cells. Finally, we show that Ndj1 forms oligomeric complexes with Mps3, and that the Polo-like kinase Cdc5 regulates Ndj1 protein stability and SPB separation. These findings reveal the underlying mechanism that coordinates yeast centrosome dynamics with meiotic telomere movement and cell cycle progression.
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Melloy, Patricia, Shu Shen, Erin White, J. Richard McIntosh et Mark D. Rose. « Nuclear fusion during yeast mating occurs by a three-step pathway ». Journal of Cell Biology 179, no 4 (19 novembre 2007) : 659–70. http://dx.doi.org/10.1083/jcb.200706151.
Texte intégralRésumé :
In Saccharomyces cerevisiae, mating culminates in nuclear fusion to produce a diploid zygote. Two models for nuclear fusion have been proposed: a one-step model in which the outer and inner nuclear membranes and the spindle pole bodies (SPBs) fuse simultaneously and a three-step model in which the three events occur separately. To differentiate between these models, we used electron tomography and time-lapse light microscopy of early stage wild-type zygotes. We observe two distinct SPBs in ∼80% of zygotes that contain fused nuclei, whereas we only see fused or partially fused SPBs in zygotes in which the site of nuclear envelope (NE) fusion is already dilated. This demonstrates that SPB fusion occurs after NE fusion. Time-lapse microscopy of zygotes containing fluorescent protein tags that localize to either the NE lumen or the nucleoplasm demonstrates that outer membrane fusion precedes inner membrane fusion. We conclude that nuclear fusion occurs by a three-step pathway.
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Wang, Mengqiao, et Ruth N. Collins. « A lysine deacetylase Hos3 is targeted to the bud neck and involved in the spindle position checkpoint ». Molecular Biology of the Cell 25, no 18 (15 septembre 2014) : 2720–34. http://dx.doi.org/10.1091/mbc.e13-10-0619.
Texte intégralRésumé :
An increasing number of cellular activities can be regulated by reversible lysine acetylation. Targeting the enzymes responsible for such posttranslational modifications is instrumental in defining their substrates and functions in vivo. Here we show that a Saccharomyces cerevisiae lysine deacetylase, Hos3, is asymmetrically targeted to the daughter side of the bud neck and to the daughter spindle pole body (SPB). The morphogenesis checkpoint member Hsl7 recruits Hos3 to the neck region. Cells with a defect in spindle orientation trigger Hos3 to load onto both SPBs. When associated symmetrically with both SPBs, Hos3 functions as a spindle position checkpoint (SPOC) component to inhibit mitotic exit. Neck localization of Hos3 is essential for its symmetric association with SPBs in cells with misaligned spindles. Our data suggest that Hos3 facilitates cross-talk between the morphogenesis checkpoint and the SPOC as a component of the intricate monitoring of spindle orientation after mitotic entry and before commitment to mitotic exit.
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Hatunoğlu, Erdem, Fırat Öztürk, Tuğça Bilenler, Sertaç Aksakallı et Neslihan Şimşek. « Antibacterial and mechanical properties of propolis added to glass ionomer cement ». Angle Orthodontist 84, no 2 (14 août 2013) : 368–73. http://dx.doi.org/10.2319/020413-101.1.
Texte intégralRésumé :
ABSTRACTObjective:To investigate whether adding ethanolic extracts of propolis (EEP) might influence the antibacterial and mechanical (shear-peel band strength [SPBS]) properties of conventional glass ionomer cement (GIC) used in orthodontic band cementation.Materials and Methods:The cement was divided into four groups: one using the original composition and three with 10%, 25%, and 50% EEP added to the liquid and then manipulated. An antimicrobial assay, broth-dilution method was used to determine the antibacterial capacity of the GIC containing EEP. Eighty teeth were used for the mechanical assay, and an Instron testing machine was used to evaluate the SPBS. Kolmogorov-Smirnov and Kruskal-Wallis tests were used for statistical analyses.Results:GIC with the addition of 25% and 50% EEP activated inhibition of Streptococcus mutans (ATCC 25175) growth, but this effect did not occur in the group to which 10% EEP was added or in the control GIC group. There was no significant difference between the groups in terms of SPBS (P > .05).Conclusions:The addition of EEP may increase antibacterial properties without negatively modifying the mechanical properties of conventional GIC.
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Helfers, Richard C., Paul D. Reynolds et Jon Maskály. « Applying Social Exchange Theory to Police Deviance : Exploring Self-Protective Behaviors Among Police Officers ». Criminal Justice Review 44, no 2 (4 septembre 2018) : 183–203. http://dx.doi.org/10.1177/0734016818796547.
Texte intégralRésumé :
Social exchange theory is one of the prominent paradigms used to explain the processes linking organizational treatment of employees to their job performance. However, the theoretical link between perceived organizational treatment and police deviance has not been fully explored. This research addresses this gap by analyzing the relationship between perceptions of organizational justice and the use of police self-protective behaviors (SPBs) using organizational support and organizational indifference as ad hoc indicators of the social exchange process. Data were collected using an online self-report survey distributed to police officers in a southern state who are members of a police officer association ( n = 1,861). Consistent with previous social exchange research, the findings generally support the idea that fairness is related to SPBs, but largely to the extent that it enhances the social exchange in terms of increasing perceptions of organizational support and reducing perceptions of organizational indifference, which both directly affect an officer’s use of SPBs, and are a type of police deviance. Specific findings, relevant policy implications, and directions for future research are discussed.
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Fraschini, Roberta, Claudio D'Ambrosio, Marianna Venturetti, Giovanna Lucchini et Simonetta Piatti. « Disappearance of the budding yeast Bub2–Bfa1 complex from the mother-bound spindle pole contributes to mitotic exit ». Journal of Cell Biology 172, no 3 (30 janvier 2006) : 335–46. http://dx.doi.org/10.1083/jcb.200507162.
Texte intégralRésumé :
Budding yeast spindle position checkpoint is engaged by misoriented spindles and prevents mitotic exit by inhibiting the G protein Tem1 through the GTPase-activating protein (GAP) Bub2/Bfa1. Bub2 and Bfa1 are found on both duplicated spindle pole bodies until anaphase onset, when they disappear from the mother-bound spindle pole under unperturbed conditions. In contrast, when spindles are misoriented they remain symmetrically localized at both SPBs. Thus, symmetric localization of Bub2/Bfa1 might lead to inhibition of Tem1, which is also present at SPBs. Consistent with this hypothesis, we show that a Bub2 version symmetrically localized on both SPBs throughout the cell cycle prevents mitotic exit in mutant backgrounds that partially impair it. This effect is Bfa1 dependent and can be suppressed by high Tem1 levels. Bub2 removal from the mother-bound SPB requires its GAP activity, which in contrast appears to be dispensable for Tem1 inhibition. Moreover, it correlates with the passage of one spindle pole through the bud neck because it needs septin ring formation and bud neck kinases.
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Windasari, Ike Yuliana, Dina Prasetyowati et Ali Shodiqin. « Analisis Pemahaman Konsep Berdasarkan Teori Apos pada Materi Barisan Geometri di Kelas XI SMA Negeri 1 Godong ». Imajiner : Jurnal Matematika dan Pendidikan Matematika 2, no 5 (30 septembre 2020) : 417–27. http://dx.doi.org/10.26877/imajiner.v2i5.6664.
Texte intégralRésumé :
Penelitian ini bertujuan untuk mengetahui: (1) pemahaman konsep pada materi barisan geometri kelas XI bagi siswa yang berkemampuan tinggi berdasarkan teori APOS, (2) pemahaman konsep pada materi barisan geometri kelas XI bagi siswa yang berkemampuan sedang berdasarkan teori APOS, (3) pemahaman konsep pada materi barisan geometri kelas XI bagi siswa yang berkemampuan rendah berdasarkan teori APOS. Metode yang digunakan adalah metode penelitian kualitatif. Instrumen utama pada penelitian ini adalah peneliti itu sendiri dibantu dengan tiga intstrumen bantu yaitu tes tertulis, pedoman wawancara, dan lembar validasi. Subjek penelitian dipilih dengan teknik pengambilan sampel purposive sampling. Teknik pengumpulan data dilaksanakan dengan metode tes untuk menentukan subjek, selanjutnya metode wawancara yang telah dipilih sesuai dengan tingkat pemahaman siswa berdasarkan teori APOS. Teknik pemeriksaan keabsahan data penelitian ini menggunakan triagulasi waktu. Hasil penelitian menunjukkan bahwa pemahaman siswa pada materi barisan geometri bervariasi yakni pada tahap aksi, proses, objek, dan skema. Subjek penelitian berkemampuan tinggi (SPBT) memiliki pemahaman konsep pada tahap aksi, proses, dan skema. Subjek penelitian berkemampuan sedang (SPBS) memiliki pemahaman konsep pada tahap aksi dan skema. Sedangkan, subjek penelitian berkemampuan rendah (SPBR) memiliki pemahaman konsep pada tahap aksi. Ketiga subjek pada materi barisan geometri sama-sama memiliki pemahaman pada tahap aksi. Adapun indikator pemahaman konsep matematika siswa berdasarkan teori APOS yang belum dilakukan siswa adalah pada tahap objek, kebanyakan siswa belum mampu menjelaskan sifat atau ciri-ciri karakteristik pada soal yang diberikan.
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Qian, Weiqiao, Qin Zhu, Bing Duan, Weijun Tang, Yuan Yuan et Aiguo Hu. « Electrostatic self-assembled nanoparticles based on spherical polyelectrolyte brushes for magnetic resonance imaging ». Dalton Transactions 47, no 23 (2018) : 7663–68. http://dx.doi.org/10.1039/c8dt01069b.
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Arquint, Christian, Anna-Maria Gabryjonczyk et Erich A. Nigg. « Centrosomes as signalling centres ». Philosophical Transactions of the Royal Society B : Biological Sciences 369, no 1650 (5 septembre 2014) : 20130464. http://dx.doi.org/10.1098/rstb.2013.0464.
Texte intégralRésumé :
Centrosomes—as well as the related spindle pole bodies (SPBs) of yeast—have been extensively studied from the perspective of their microtubule-organizing roles. Moreover, the biogenesis and duplication of these organelles have been the subject of much attention, and the importance of centrosomes and the centriole–ciliary apparatus for human disease is well recognized. Much less developed is our understanding of another facet of centrosomes and SPBs, namely their possible role as signalling centres. Yet, many signalling components, including kinases and phosphatases, have been associated with centrosomes and spindle poles, giving rise to the hypothesis that these organelles might serve as hubs for the integration and coordination of signalling pathways. In this review, we discuss a number of selected studies that bear on this notion. We cover different processes (cell cycle control, development, DNA damage response) and organisms (yeast, invertebrates and vertebrates), but have made no attempt to be comprehensive. This field is still young and although the concept of centrosomes and SPBs as signalling centres is attractive, it remains primarily a concept—in need of further scrutiny. We hope that this review will stimulate thought and experimentation.
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Fong, Kimberly K., Krishna K. Sarangapani, Erik C. Yusko, Michael Riffle, Aida Llauró, Beth Graczyk, Trisha N. Davis et Charles L. Asbury. « Direct measurement of the strength of microtubule attachment to yeast centrosomes ». Molecular Biology of the Cell 28, no 14 (7 juillet 2017) : 1853–61. http://dx.doi.org/10.1091/mbc.e17-01-0034.
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Centrosomes, or spindle pole bodies (SPBs) in yeast, are vital mechanical hubs that maintain load-bearing attachments to microtubules during mitotic spindle assembly, spindle positioning, and chromosome segregation. However, the strength of microtubule-centrosome attachments is unknown, and the possibility that mechanical force might regulate centrosome function has scarcely been explored. To uncover how centrosomes sustain and regulate force, we purified SPBs from budding yeast and used laser trapping to manipulate single attached microtubules in vitro. Our experiments reveal that SPB–microtubule attachments are extraordinarily strong, rupturing at forces approximately fourfold higher than kinetochore attachments under identical loading conditions. Furthermore, removal of the calmodulin-binding site from the SPB component Spc110 weakens SPB–microtubule attachment in vitro and sensitizes cells to increased SPB stress in vivo. These observations show that calmodulin binding contributes to SPB mechanical integrity and suggest that its removal may cause pole delamination and mitotic failure when spindle forces are elevated. We propose that the very high strength of SPB–microtubule attachments may be important for spindle integrity in mitotic cells so that tensile forces generated at kinetochores do not cause microtubule detachment and delamination at SPBs.
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Jones, Christine M., Jun-Song Chen, Alyssa E. Johnson, Zachary C. Elmore, Sierra N. Cullati, Janel R. Beckley et Kathleen L. Gould. « Relief of the Dma1-mediated checkpoint requires Dma1 autoubiquitination and dynamic localization ». Molecular Biology of the Cell 29, no 18 (septembre 2018) : 2176–89. http://dx.doi.org/10.1091/mbc.e18-04-0261.
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Chromosome segregation and cell division are coupled to prevent aneuploidy and cell death. In the fission yeast Schizosaccharomyces pombe, the septation initiation network (SIN) promotes cytokinesis, but upon mitotic checkpoint activation, the SIN is actively inhibited to prevent cytokinesis from occurring before chromosomes have safely segregated. SIN inhibition during the mitotic checkpoint is mediated by the E3 ubiquitin ligase Dma1. Dma1 binds to the CK1-phosphorylated SIN scaffold protein Sid4 at the spindle pole body (SPB), and ubiquitinates it. Sid4 ubiquitination antagonizes the SPB localization of the Pololike kinase Plo1, the major SIN activator, so that SIN signaling is delayed. How this checkpoint is silenced once spindle defects are resolved has not been clear. Here we establish that Dma1 transiently leaves SPBs during anaphase B due to extensive autoubiquitination. The SIN is required for Dma1 to return to SPBs later in anaphase. Blocking Dma1 removal from SPBs by permanently tethering it to Sid4 prevents SIN activation and cytokinesis. Therefore, controlling Dma1’s SPB dynamics in anaphase is an essential step in S. pombe cell division and the silencing of the Dma1-dependent mitotic checkpoint.
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Hao, Shuai, Xiaoxuan Sun, He Zhang, Junfeng Zhai et Shaojun Dong. « Recent development of biofuel cell based self-powered biosensors ». Journal of Materials Chemistry B 8, no 16 (2020) : 3393–407. http://dx.doi.org/10.1039/c9tb02428j.
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Fox, Colette, Juan Zou, Juri Rappsilber et Adele L. Marston. « Cdc14 phosphatase directs centrosome re-duplication at the meiosis I to meiosis II transition in budding yeast ». Wellcome Open Research 2 (5 janvier 2017) : 2. http://dx.doi.org/10.12688/wellcomeopenres.10507.1.
Texte intégralRésumé :
Background Gametes are generated through a specialized cell division called meiosis, in which ploidy is reduced by half because two consecutive rounds of chromosome segregation, meiosis I and meiosis II, occur without intervening DNA replication. This contrasts with the mitotic cell cycle where DNA replication and chromosome segregation alternate to maintain the same ploidy. At the end of mitosis, CDKs are inactivated. This low CDK state in late mitosis/G1 allows for critical preparatory events for DNA replication and centrosome/spindle pole body (SPB) duplication. However, their execution is inhibited until S phase, where further preparatory events are also prevented. This “licensing” ensures that both the chromosomes and the centrosomes/SPBs replicate exactly once per cell cycle, thereby maintaining constant ploidy. Crucially, between meiosis I and meiosis II, centrosomes/SPBs must be re-licensed, but DNA re-replication must be avoided. In budding yeast, the Cdc14 protein phosphatase triggers CDK down regulation to promote exit from mitosis. Cdc14 also regulates the meiosis I to meiosis II transition, though its mode of action has remained unclear. Methods Fluorescence and electron microscopy was combined with proteomics to probe SPB duplication in cells with inactive or hyperactive Cdc14. Results We demonstrate that Cdc14 ensures two successive nuclear divisions by re-licensing SPBs at the meiosis I to meiosis II transition. We show that Cdc14 is asymmetrically enriched on a single SPB during anaphase I and provide evidence that this enrichment promotes SPB re-duplication. Cells with impaired Cdc14 activity fail to promote extension of the SPB half-bridge, the initial step in morphogenesis of a new SPB. Conversely, cells with hyper-active Cdc14 duplicate SPBs, but fail to induce their separation. Conclusion Our findings implicate reversal of key CDK-dependent phosphorylations in the differential licensing of cyclical events at the meiosis I to meiosis I transition.
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Fox, Colette, Juan Zou, Juri Rappsilber et Adele L. Marston. « Cdc14 phosphatase directs centrosome re-duplication at the meiosis I to meiosis II transition in budding yeast ». Wellcome Open Research 2 (21 février 2017) : 2. http://dx.doi.org/10.12688/wellcomeopenres.10507.2.
Texte intégralRésumé :
Background: Gametes are generated through a specialized cell division called meiosis, in which ploidy is reduced by half because two consecutive rounds of chromosome segregation, meiosis I and meiosis II, occur without intervening DNA replication. This contrasts with the mitotic cell cycle where DNA replication and chromosome segregation alternate to maintain the same ploidy. At the end of mitosis, cyclin-dependent kinases (CDKs) are inactivated. This low CDK state in late mitosis/G1 allows for critical preparatory events for DNA replication and centrosome/spindle pole body (SPB) duplication. However, their execution is inhibited until S phase, where further preparatory events are also prevented. This “licensing” ensures that both the chromosomes and the centrosomes/SPBs replicate exactly once per cell cycle, thereby maintaining constant ploidy. Crucially, between meiosis I and meiosis II, centrosomes/SPBs must be re-licensed, but DNA re-replication must be avoided. In budding yeast, the Cdc14 protein phosphatase triggers CDK down regulation to promote exit from mitosis. Cdc14 also regulates the meiosis I to meiosis II transition, though its mode of action has remained unclear. Methods: Fluorescence and electron microscopy was combined with proteomics to probe SPB duplication in cells with inactive or hyperactive Cdc14. Results: We demonstrate that Cdc14 ensures two successive nuclear divisions by re-licensing SPBs at the meiosis I to meiosis II transition. We show that Cdc14 is asymmetrically enriched on a single SPB during anaphase I and provide evidence that this enrichment promotes SPB re-duplication. Cells with impaired Cdc14 activity fail to promote extension of the SPB half-bridge, the initial step in morphogenesis of a new SPB. Conversely, cells with hyper-active Cdc14 duplicate SPBs, but fail to induce their separation. Conclusion: Our findings implicate reversal of key CDK-dependent phosphorylations in the differential licensing of cyclical events at the meiosis I to meiosis II transition.
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Zekert, Nadine, Daniel Veith et Reinhard Fischer. « Interaction of the Aspergillus nidulans Microtubule-Organizing Center (MTOC) Component ApsB with Gamma-Tubulin and Evidence for a Role of a Subclass of Peroxisomes in the Formation of Septal MTOCs ». Eukaryotic Cell 9, no 5 (26 mars 2010) : 795–805. http://dx.doi.org/10.1128/ec.00058-10.
Texte intégralRésumé :
ABSTRACT Peroxisomes are a diverse class of organelles involved in different physiological processes in eukaryotic cells. Although proteins imported into peroxisomes carry a peroxisomal targeting sequence at the C terminus (PTS1) or an alternative one close to the N terminus (PTS2), the protein content of peroxisomes varies drastically. Here we suggest a new class of peroxisomes involved in microtubule (MT) formation. Eukaryotic cells assemble MTs from distinct points in the cell. In the fungus Aspergillus nidulans, septum-associated microtubule-organizing centers (sMTOCs) are very active in addition to the spindle pole bodies (SPBs). Previously, we identified a novel MTOC-associated protein, ApsB (Schizosaccharomyces pombe mto1), whose absence affected MT formation from sMTOCs more than from SPBs, suggesting that the two protein complexes are organized differently. We show here that sMTOCs share at least two further components, gamma-tubulin and GcpC (S. pombe Alp6) with SPBs and found that ApsB interacts with gamma-tubulin. In addition, we discovered that ApsB interacts with the Woronin body protein HexA and is targeted to a subclass of peroxisomes via a PTS2 peroxisomal targeting sequence. The PTS2 motif was necessary for function but could be replaced with a PTS1 motif at the C terminus of ApsB. These results suggest a novel function for a subclass of peroxisomes in cytoskeletal organization.
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Masuda, Hirohisa, et Takashi Toda. « Synergistic role of fission yeast Alp16GCP6 and Mzt1MOZART1 in γ-tubulin complex recruitment to mitotic spindle pole bodies and spindle assembly ». Molecular Biology of the Cell 27, no 11 (juin 2016) : 1753–63. http://dx.doi.org/10.1091/mbc.e15-08-0577.
Texte intégralRésumé :
In fission yeast, γ-tubulin ring complex (γTuRC)–specific components Gfh1GCP4, Mod21GCP5, and Alp16GCP6 are nonessential for cell growth. Of these deletion mutants, only alp16Δ shows synthetic lethality with temperature-sensitive mutants of Mzt1MOZART1, a component of the γTuRC required for recruitment of the complex to microtubule-organizing centers. γ-Tubulin small complex levels at mitotic spindle pole bodies (SPBs, the centrosome equivalent in fungi) and microtubule levels for preanaphase spindles are significantly reduced in alp16Δ cells but not in gfh1Δ or mod21Δ cells. Furthermore, alp16Δ cells often form monopolar spindles and frequently lose a minichromosome when the spindle assembly checkpoint is inactivated. Alp16GCP6 promotes Mzt1-dependent γTuRC recruitment to mitotic SPBs and enhances spindle microtubule assembly in a manner dependent on its expression levels. Gfh1GCP4 and Mod21GCP5 are not required for Alp16GCP6-dependent γTuRC recruitment. Mzt1 has an additional role in the activation of the γTuRC for spindle microtubule assembly. The ratio of Mzt1 to γTuRC levels for preanaphase spindles is higher than at other stages of the cell cycle. Mzt1 overproduction enhances spindle microtubule assembly without affecting γTuRC levels at mitotic SPBs. We propose that Alp16GCP6 and Mzt1 act synergistically for efficient bipolar spindle assembly to ensure faithful chromosome segregation.
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Wilson, Richard, Clara Pitois, Aurélien Podglajen, Albert Hertzog, Milena Corcos et Riwal Plougonven. « Detection of turbulence occurrences from temperature, pressure, and position measurements under superpressure balloons ». Atmospheric Measurement Techniques 16, no 2 (20 janvier 2023) : 311–30. http://dx.doi.org/10.5194/amt-16-311-2023.
Texte intégralRésumé :
Abstract. This article deals with the detection of small-scale turbulence from in situ meteorological measurements performed under superpressure balloons (SPBs). These balloons allow long-duration flights (several months) at a prerequisite height level. The data set is gathered from the Strateole-2 probationary campaign during which eights SPBs flew in the tropical tropopause layer at altitudes of around 19 and 20.5 km from November 2019 to March 2020. Turbulence is not directly measured by the instrument set onboard the SPBs. Nonetheless, there is the potential to derive information about the occurrence of turbulence from the temporally well-resolved measurements of pressure, temperature, and position. It constitutes a challenge to extract the aforementioned information from a measurement set that was not designed for quantifying turbulence, and the paper explains the methodology developed to overcome this difficulty. It is observed that SPBs oscillate quasi-periodically around their equilibrium positions. The oscillation periods, which are 220 s on average with a range of 130 to 500 s, are close to but noticeably smaller than the Brunt–Väisälä period (∼300 s). The amplitude of these vertical motions is ∼±15 m, inducing large fluctuations in all quantities, whether measured (e.g., pressure, temperature and position) or inferred (e.g., density and potential temperature). The relationships between the changes in these quantities and the vertical displacements of the balloons are used to infer properties of the flow in which the SPBs drift. In the case of active turbulence, the vertical stratification as well as the wind shear are likely to be reduced by mixing. Hence, the increments of potential temperature, δθ, and of the vertical displacements of the balloon, δzB, are expected to be uncorrelated because ∂θ/∂z→0. Moreover, the local vertical gradients of measured quantities, temperature (T) and horizontal velocities (u and v), are estimated from the covariance of the increments of the considered quantity with δzB. The Richardson number of the flow is deduced. Several binary indexes (true or false) to describe the state of the flow, laminar or turbulent, are evaluated. These turbulence indexes, based either on correlations between δθ and δzB or on estimates of the local Richardson number, are found to be consistent, as they differ in less than 3 % of cases. The flow is observed to be turbulent for about 5 % of the time, with strong inhomogeneities along the longitude.
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Nguyen, Trung T., Kirsten Heimann et Wei Zhang. « Protein Recovery from Underutilised Marine Bioresources for Product Development with Nutraceutical and Pharmaceutical Bioactivities ». Marine Drugs 18, no 8 (27 juillet 2020) : 391. http://dx.doi.org/10.3390/md18080391.
Texte intégralRésumé :
The global demand for dietary proteins and protein-derived products are projected to dramatically increase which cannot be met using traditional protein sources. Seafood processing by-products (SPBs) and microalgae are promising resources that can fill the demand gap for proteins and protein derivatives. Globally, 32 million tonnes of SPBs are estimated to be produced annually which represents an inexpensive resource for protein recovery while technical advantages in microalgal biomass production would yield secure protein supplies with minimal competition for arable land and freshwater resources. Moreover, these biomaterials are a rich source of proteins with high nutritional quality while protein hydrolysates and biopeptides derived from these marine proteins possess several useful bioactivities for commercial applications in multiple industries. Efficient utilisation of these marine biomaterials for protein recovery would not only supplement global demand and save natural bioresources but would also successfully address the financial and environmental burdens of biowaste, paving the way for greener production and a circular economy. This comprehensive review analyses the potential of using SPBs and microalgae for protein recovery and production critically assessing the feasibility of current and emerging technologies used for the process development. Nutritional quality, functionalities, and bioactivities of the extracted proteins and derived products together with their potential applications for commercial product development are also systematically summarised and discussed.
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Chen, Chang-Rung, Jing Chen et Eric C. Chang. « A Conserved Interaction between Moe1 and Mal3 Is Important for Proper Spindle Formation in Schizosaccharomyces pombe ». Molecular Biology of the Cell 11, no 12 (décembre 2000) : 4067–77. http://dx.doi.org/10.1091/mbc.11.12.4067.
Texte intégralRésumé :
Moe1 is a conserved fission yeast protein that negatively affects microtubule stability/assembly. We conducted a two-hybrid screen to search for Moe1-binding proteins and isolated Mal3, a homologue of human EB1. We show that Moe1 and Mal3 expressed in bacteria form a complex and that Moe1 and Mal3 expressed in fission yeast cosediment with microtubules. Deletion of either moe1 ormal3 does not result in lethality; however, deletion of both moe1 and mal3 leads to cell death in the cold. The resulting cells appear to die of chromosome missegregation, which correlates with the presence of abnormal spindles. We investigated the cause for the formation of monopolar spindles and found that only one of the two spindle pole bodies (SPBs) contains γ-tubulin, although both SPBs appear to be equal in size and properly inserted in the nuclear membrane. Moreover, the moe1 mal3 double null mutant in the cold contains abnormally short and abundant interphase microtubule bundles. These data suggest that Moe1 and Mal3 play a role in maintaining proper microtubule dynamics/integrity and distribution of γ-tubulin to the SPBs during mitosis. Finally, we show that human Moe1 and EB1 can each rescue the phenotype of the moe1 mal3 double null mutant and form a complex, suggesting that these proteins are part of a well-conserved mechanism for regulating spindle functioning.
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Cuschieri, Lara, Rita Miller et Jackie Vogel. « γ-Tubulin Is Required for Proper Recruitment and Assembly of Kar9–Bim1 Complexes in Budding Yeast ». Molecular Biology of the Cell 17, no 10 (octobre 2006) : 4420–34. http://dx.doi.org/10.1091/mbc.e06-03-0245.
Texte intégralRésumé :
Microtubule plus-end–interacting proteins (+TIPs) promote the dynamic interactions between the plus ends (+ends) of astral microtubules and cortical actin that are required for preanaphase spindle positioning. Paradoxically, +TIPs such as the EB1 orthologue Bim1 and Kar9 also associate with spindle pole bodies (SPBs), the centrosome equivalent in budding yeast. Here, we show that deletion of four C-terminal residues of the budding yeast γ-tubulin Tub4 (tub4-Δdsyl) perturbs Bim1 and Kar9 localization to SPBs and Kar9-dependant spindle positioning. Surprisingly, we find Kar9 localizes to microtubule +ends in tub4-Δdsyl cells, but these microtubules fail to position the spindle when targeted to the bud. Using cofluorescence and coaffinity purification, we show Kar9 complexes in tub4-Δdsyl cells contain reduced levels of Bim1. Astral microtubule dynamics is suppressed in tub4-Δdsyl cells, but it are restored by deletion of Kar9. Moreover, Myo2- and F-actin–dependent dwelling of Kar9 in the bud is observed in tub4-Δdsyl cells, suggesting defective Kar9 complexes tether microtubule +ends to the cortex. Overproduction of Bim1, but not Kar9, restores Kar9-dependent spindle positioning in the tub4-Δdsyl mutant, reduces cortical dwelling, and promotes Bim1–Kar9 interactions. We propose that SPBs, via the tail of Tub4, promote the assembly of functional +TIP complexes before their deployment to microtubule +ends.
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Lim, H. H., P. Y. Goh et U. Surana. « Spindle pole body separation in Saccharomyces cerevisiae requires dephosphorylation of the tyrosine 19 residue of Cdc28. » Molecular and Cellular Biology 16, no 11 (novembre 1996) : 6385–97. http://dx.doi.org/10.1128/mcb.16.11.6385.
Texte intégralRésumé :
In eukaryotes, mitosis requires the activation of cdc2 kinase via association with cyclin B and dephosphorylation of the threonine 14 and tyrosine 15 residues. It is known that in the budding yeast Saccharomyces cerevisiae, a homologous kinase, Cdc28, mediates the progression through M phase, but it is not clear what specific mitotic function its activation by the dephosphorylation of an equivalent tyrosine (Tyr-19) serves. We report here that cells expressing cdc28-E19 (in which Tyr-19 is replaced by glutamic acid) perform Start-related functions, complete DNA synthesis, and exhibit high levels of Clb2-associated kinase activity but are unable to form bipolar spindles. The failure of these cells to form mitotic spindles is due to their inability to segregate duplicated spindle pole bodies (SPBs), a phenotype strikingly similar to that exhibited by a previously reported mutant defective in both kinesin-like motor proteins Cin8 and Kip1. We also find that the overexpression of SWE1, the budding-yeast homolog of wee1, also leads to a failure to segregate SPBs. These results imply that dephosphorylation of Tyr-19 is required for the segregation of SPBs. The requirement of Tyr-19 dephosphorylation for spindle assembly is also observed under conditions in which spindle formation is independent of mitosis, suggesting that the involvement of Cdc28/Clb kinase in SPB separation is direct. On the basis of these results, we propose that one of the roles of Tyr-19 dephosphorylation is to promote SPB separation.