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831.
Yulia Steblyanko Girish Rajendraprasad Mariana Osswald Susana Eibes Ariana Jacome Stephan Geley Antnio J Pereira Helder Maiato Marin Barisic 《The EMBO journal》2020,39(23)
Mitotic spindle microtubules (MTs) undergo continuous poleward flux, whose driving force and function in humans remain unclear. Here, we combined loss‐of‐function screenings with analysis of MT‐dynamics in human cells to investigate the molecular mechanisms underlying MT‐flux. We report that kinesin‐7/CENP‐E at kinetochores (KTs) is the predominant driver of MT‐flux in early prometaphase, while kinesin‐4/KIF4A on chromosome arms facilitates MT‐flux during late prometaphase and metaphase. Both these activities work in coordination with kinesin‐5/EG5 and kinesin‐12/KIF15, and our data suggest that the MT‐flux driving force is transmitted from non‐KT‐MTs to KT‐MTs by the MT couplers HSET and NuMA. Additionally, we found that the MT‐flux rate correlates with spindle length, and this correlation depends on the establishment of stable end‐on KT‐MT attachments. Strikingly, we find that MT‐flux is required to regulate spindle length by counteracting kinesin 13/MCAK‐dependent MT‐depolymerization. Thus, our study unveils the long‐sought mechanism of MT‐flux in human cells as relying on the coordinated action of four kinesins to compensate for MT‐depolymerization and regulate spindle length. 相似文献
832.
833.
《Tissue & cell》2016,48(6):605-615
Head shaping in mammalian sperm is regulated by a number of factors including acrosome formation, nuclear condensation and the action of the microtubular manchette. A role has also been suggested for the attendant Sertoli cells and the perinuclear theca (PT). In comparison, relatively little information is available on this topic in birds and the presence of a PT per se has not been described in this vertebrate order. This study revealed that a similar combination of factors contributed to head shaping in the ostrich, emu and rhea, although the Sertoli cells seem to play a limited role in ratites. A fibro-granular structure analogous to the mammalian PT was identified, consisting of sub- and post-acrosomal components. The latter was characterized by stage-specific finger-like projections that appeared to emanate from the cytoplasmic face of the nuclear envelope. They were particularly obvious beneath the base of the acrosome, and closely aligned, but not connected to, the manchette microtubules. During the final stages of chromatin condensation and elongation of the sperm head the projections abruptly disappeared. They appear to play a role in stabilizing the shape of the sperm head during the caudal translocation of the spermatid cytoplasm. 相似文献
834.
《Cell host & microbe》2021,29(8):1277-1293.e6
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835.
Martin Würtz Anna Bhler Annett Neuner Erik Zupa Lukas Rohland Peng Liu Bram J. A. Vermeulen Stefan Pfeffer Sebastian Eustermann Elmar Schiebel 《Open biology》2021,11(2)
Cryo-electron microscopy recently resolved the structure of the vertebrate γ-tubulin ring complex (γ-TuRC) purified from Xenopus laevis egg extract and human cells to near-atomic resolution. These studies clarified the arrangement and stoichiometry of γ-TuRC components and revealed that one molecule of actin and the small protein MZT1 are embedded into the complex. Based on this structural census of γ-TuRC core components, we developed a recombinant expression system for the reconstitution and purification of human γ-TuRC from insect cells. The recombinant γ-TuRC recapitulates the structure of purified native γ-TuRC and has similar functional properties in terms of microtubule nucleation and minus end capping. This recombinant system is a central step towards deciphering the activation mechanisms of the γ-TuRC and the function of individual γ-TuRC core components. 相似文献
836.
Abstract: Gravity-induced events such as amyloplast sedimentation and lateral auxin transport were probed with cytoskeletal drugs in coleoptiles of rice ( Oryza sativa L.). Amyloplast sedimentation was retarded by taxol. Lateral transport of auxin (3 H-indoleacetic acid) was strongly inhibited by EPC (ethyl N-phenylcarbamate), but only partially inhibited by taxol. 1 mM EPC reduced gravitropism while phototropism was not affected. The findings suggest that microtubules may transduce pressure or proximity of amyloplasts to the auxin exporter in the plasmalemma. 相似文献
837.
Dr. Françoise Tripier-Darcy Jacqueline Braunwald André Kirn 《Cell and tissue research》1980,209(2):271-277
Summary Intranuclear microtubules appear in chick embryo fibroblasts upon infection with Frog Virus 3 (FV 3). Both the diameter and the annular shape of the microtubule profiles, established from electron microscopic observations using a goniometer, suggest that they are identical to naturally occurring cytoplasmic microtubules. Furthermore, the use of vinblastine allowed demonstration of the tubulin composition of the intranuclear microtubules. 相似文献
838.
Summary
Euglypha acanthophora and Euglypha strigosa, testate amoebae with siliceous shells, undergo binary fission producing daughter cells. The siliceous plates from which the shells are constructed are produced in the Golgi and perinuclear regions of the parent. At binary fission these pass along microtubule pathways and are manoeuvered into position in the daughter-cell by microtubule (20–25 nm) and microfilament (7–9 nm) systems. The latter in the form of adhesion plaques are instrumental in the coordination and deployment of the shell-plates. 相似文献
839.
Summary The antarctic teleost, Pagothenia borchgrevinki inhabits the Antarctic Ocean where the water temperature remains around -1.9° C throughout the year. Dermal melanophores of this fish respond within minutes to epinephrine and theophylline with melanosome aggregation and dispersion, respectively. Numerous cytoplasmic microtubules are present in these cells despite the low environmental temperature. In longitudinal profiles, many microtubules are twisted, beaded and sometimes even branched. In cross sections, C-, U-, S-, 6- and other irregularly shaped tubules are observed. Nocodazole partially disrupts microtubules and inhibits epinephrine-induced pigment aggregation. Pigment movements are also prevented by erythro-9-[3-(2-hydroxynonyl)] adenine. Although the participation of these incomplete microtubules in cell motility remains uncertain, the results indicate that this fish has a cold-resistant microtubule system on which melanosome movements depend. Unlike those in melanophores, microtubules in the axons of spinal nerves are of uniform thickness and often contain an electron-dense core in the center. 相似文献
840.
《Molecular cell》2022,82(1):75-89.e9
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