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  • 1
    Publication Date: 2022-05-25
    Description: Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Elsevier B. V. for personal use, not for redistribution. The definitive version was published in Current Biology 15 (2005): 1979-1988, doi:10.1016/j.cub.2005.09.054.
    Description: The pole-to-pole distance of the metaphase spindle is reasonably constant in a given cell type; in the case of vertebrate female oocytes, this steady-state length can be maintained for substantial lengths of time, during which time microtubules remain highly dynamic. Although a number of molecular perturbations have been shown to influence spindle length, a global understanding of the factors that determine metaphase spindle length has not been achieved. Using the Drosophila S2 cell line, we depleted or overexpressed proteins that either generate sliding forces between spindle microtubules (Kinesin-5, Kinesin-14, dynein), promote microtubule polymerization (EB1, Mast/Orbit [CLASP], Minispindles [Dis1/XMAP215/TOG]) or depolymerization (Kinesin-8, Kinesin-13), or mediate sister-chromatid cohesion (Rad21) in order to explore how these forces influence spindle length. Using high-throughput automated microscopy and semiautomated image analyses of 〉4000 spindles, we found a reduction in spindle size after RNAi of microtubule-polymerizing factors or overexpression of Kinesin-8, whereas longer spindles resulted from the knockdown of Rad21, Kinesin-8, or Kinesin-13. In contrast, and differing from previous reports, bipolar spindle length is relatively insensitive to increases in motor-generated sliding forces. However, an ultrasensitive monopolar-to-bipolar transition in spindle architecture was observed at a critical concentration of the Kinesin-5 sliding motor. These observations could be explained by a quantitative model that proposes a coupling between microtubule depolymerization rates and microtubule sliding forces. By integrating extensive RNAi with high-throughput image-processing methodology and mathematical modeling, we reach to a conclusion that metaphase spindle length is sensitive to alterations in microtubule dynamics and sister-chromatid cohesion, but robust against alterations of microtubule sliding force.
    Keywords: RNAi ; Mitosis ; Microtubule ; Drosophila S2 cell
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 2
    Publication Date: 2022-05-25
    Description: © The Authors, 2009 . This article is distributed under the terms of the Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported License. The definitive version was published in Journal of Cell Biology 186 (2009): 727-738, doi:10.1083/jcb.200902083.
    Description: Signals from the mitotic spindle during anaphase specify the location of the actomyosin contractile ring during cytokinesis, but the detailed mechanism remains unresolved. Here, we have imaged the dynamics of green fluorescent protein–tagged myosin filaments, microtubules, and Kinesin-6 (which carries activators of Rho guanosine triphosphatase) at the cell cortex using total internal reflection fluorescence microscopy in flattened Drosophila S2 cells. At anaphase onset, Kinesin-6 relocalizes to microtubule plus ends that grow toward the cortex, but refines its localization over time so that it concentrates on a subset of stable microtubules and along a diffuse cortical band at the equator. The pattern of Kinesin-6 localization closely resembles where new myosin filaments appear at the cortex by de novo assembly. While accumulating at the equator, myosin filaments disappear from the poles of the cell, a process that also requires Kinesin-6 as well as possibly other signals that emanate from the elongating spindle. These results suggest models for how Kinesin-6 might define the position of cortical myosin during cytokinesis.
    Description: This work was supported by a National Institutes of Health grant NIH 38499 to R.D. Vale.
    Repository Name: Woods Hole Open Access Server
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  • 3
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in Nature Plants 1 (2015): 15087, doi:10.1038/nplants.2015.87.
    Description: The molecular motors kinesin and dynein drive bidirectional motility along microtubules (MTs) in most eukaryotic cells1,2. Land plants, however, are a notable exception, since they contain a large number of kinesins but lack cytoplasmic dynein, the foremost processive retrograde transporter3,4. It remains unclear how plants achieve retrograde cargo transport without dynein. Here, we have analyzed the motility of the six members of minus-end-directed kinesin-14 motors in the moss Physcomitrella patens and found that none are processive as native dimers. However, when artificially clustered into as little as dimer of dimers, the type-VI kinesin-14 (a homologue of Arabidopsis KCBP [kinesin-like calmodulin binding protein]) exhibited highly processive and fast motility (up to 0.6 μm/s). Multiple kin14-VI dimers attached to liposomes also induced transport of this membrane cargo over several microns. Consistent with these results, in vivo observations of GFP-tagged kin14-VI in moss cells revealed fluorescent punctae that moved processively towards the minus ends of the cytoplasmic MTs. These data suggest that clustering of a kinesin-14 motor serves as a dynein-independent mechanism for retrograde transport in plants.
    Description: This work was supported by the Human Frontier Science Program, the James A. and Faith Miller Memorial Fund (MBL), the Laura and Arthur Colwin Endowed Summer Research Fellowship Fund (MBL), the TORAY Science Foundation, Grants-in-Aid for Scientific Research (15K14540, MEXT) (G.G), and the NIH (38499; R.D.V).
    Description: 2015-12-29
    Repository Name: Woods Hole Open Access Server
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  • 4
    Publication Date: 2022-05-26
    Description: © 2008 Goshima et al. This article is distributed under the terms of a Creative Commons License (Attribution–Noncommercial–Share Alike 3.0 Unported license). The definitive version was published in Journal of Cell Biology 181 (2008): 421-429, doi:10.1083/jcb.200711053.
    Description: Since the discovery of γ-tubulin, attention has focused on its involvement as a microtubule nucleator at the centrosome. However, mislocalization of {gamma}-tubulin away from the centrosome does not inhibit mitotic spindle formation in Drosophila melanogaster, suggesting that a critical function for γ-tubulin might reside elsewhere. A previous RNA interference (RNAi) screen identified five genes (Dgt2–6) required for localizing γ-tubulin to spindle microtubules. We show that the Dgt proteins interact, forming a stable complex. We find that spindle microtubule generation is substantially reduced after knockdown of each Dgt protein by RNAi. Thus, the Dgt complex that we name "augmin" functions to increase microtubule number. Reduced spindle microtubule generation after augmin RNAi, particularly in the absence of functional centrosomes, has dramatic consequences on mitotic spindle formation and function, leading to reduced kinetochore fiber formation, chromosome misalignment, and spindle bipolarity defects. We also identify a functional human homologue of Dgt6. Our results suggest that an important mitotic function for γ-tubulin may lie within the spindle, where augmin and γ-tubulin function cooperatively to amplify the number of microtubules.
    Description: This work is supported by the Special Coordination Funds for Promoting Science and Technology (MEXT, Japan), the Global COE Program “Advanced Systems-Biology: Designing the Biological Function” (MEXT), and the Uehara Memorial Foundation.
    Repository Name: Woods Hole Open Access Server
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  • 5
    Publication Date: 2022-05-26
    Description: Author Posting. © The Author(s), 2016. This is the author's version of the work. It is posted here by permission of American Association for the Advancement of Science for personal use, not for redistribution. The definitive version was published in Science 352 (2016): 595-599, doi:10.1126/science.aad9964.
    Description: Activation of various cell surface receptors triggers the reorganization of downstream signaling molecules into micron- or submicron-sized clusters. However, the functional consequences of such clustering has been unclear. We biochemically reconstituted a 12-component signaling pathway on model membranes, beginning with T cell receptor (TCR) activation and ending with actin assembly. When TCR phoshophorylation was triggered, downstream signaling proteins spontaneously separated into liquid-like clusters that promoted signaling outputs both in vitro and in human Jurkat T cells. Reconstituted clusters were enriched in kinases but excluded phosphatases, and enhanced actin filament assembly by recruiting and organizing actin regulators. These results demonstrate that protein phase separation can create a distinct physical and biochemical compartment that facilitates signaling.
    Description: This work was supported by the HCIA program of HHMI, the NIH (R01-GM56322 to M.K.R.) and Welch Foundation (I–1544 to M.K.R.). X.S. was supported by CRI Irvington postdoctoral fellowship. J.A.D. was supported by NRSA F32 award 5-F32-DK101188. E.H. was supported as a fellow of the Leukemia and Lymphoma Society. J.O. was supported by funds from Tobacco-Related Disease Research Program of the University of California (19FT-0090).
    Description: 2016-10-07
    Repository Name: Woods Hole Open Access Server
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  • 6
    Publication Date: 2022-05-26
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ditlev, J. A., Vega, A. R., Köster, D. V., Su, X., Tani, T., Lakoduk, A. M., Vale, R. D., Mayor, S., Jaqaman, K., & Rosen, M. K. A composition-dependent molecular clutch between T cell signaling condensates and actin. Elife, 8, (2019): e42695, doi:10.7554/eLife.42695.
    Description: During T cell activation, biomolecular condensates form at the immunological synapse (IS) through multivalency-driven phase separation of LAT, Grb2, Sos1, SLP-76, Nck, and WASP. These condensates move radially at the IS, traversing successive radially-oriented and concentric actin networks. To understand this movement, we biochemically reconstituted LAT condensates with actomyosin filaments. We found that basic regions of Nck and N-WASP/WASP promote association and co-movement of LAT condensates with actin, indicating conversion of weak individual affinities to high collective affinity upon phase separation. Condensates lacking these components were propelled differently, without strong actin adhesion. In cells, LAT condensates lost Nck as radial actin transitioned to the concentric network, and engineered condensates constitutively binding actin moved aberrantly. Our data show that Nck and WASP form a clutch between LAT condensates and actin in vitro and suggest that compositional changes may enable condensate movement by distinct actin networks in different regions of the IS. https://doi.org/10.7554/eLife.42695.001
    Description: We thank L Rice, J Hammer III, and our fellow HCIA Summer Institute scientists for stimulating discussions about this study. This work was supported by a Howard Hughes Medical Institute Collaborative Innovation Award, the Welch Foundation (I-1544 to MKR), a JC Bose Fellowship from the Department of Science and Technology, government of India (SM), a Margadarshi Fellowship from the Wellcome Trust – Department of Biotechnology, India Alliance (IA/M/15/1/502018 to SM), NIH (R01 GM100160 to TT) (R35 GM119619 to KJ), a CPRIT Recruitment Award (R1216 to KJ), and the UT Southwestern Endowed Scholars Program (KJ). Research in the Rosen lab is supported by the Howard Hughes Medical Institute. JAD was supported by a National Research Service Award F32 (F32 DK101188). ARV was supported by a CPRIT Training Grant (RP140110, PI: Michael White). DVK was supported by fellowships of the AXA Research Fund and the National Centre for Biological Sciences, Tata Institute for Fundamental Research. XS was supported by a Cancer Research Institute Irvington postdoctoral fellowship.
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  • 7
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
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  • 8
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Cell and Developmental Biology 13 (1997), S. 745-777 
    ISSN: 1081-0706
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Medicine
    Notes: Abstract The kinesin superfamily comprises a large and structurally diverse group of microtubule-based motor proteins that produce a variety of force-generating activities within cells. This review addresses how the structures of kinesin proteins provide clues as to their biological functions and motile properties. We discuss structural features common to all kinesin motors, as well as specialized features that enable subfamilies of related motors to carry out specialized activities. We also discuss how the kinesin motor domain uses chemical energy from ATP hydrolysis to move along microtubules.
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  • 10
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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