Maloriented bivalents have metaphase positions at the spindle equator with more kinetochore microtubules to one pole than to the other.


:To test the "traction fiber" model for metaphase positioning of bivalents during meiosis, kinetochore fibers of maloriented bivalents, induced during recovery from cold arrest, were analyzed with a liquid crystal polarizing microscope. The measured birefringence retardation of kinetochore fibers is proportional to the number of microtubules in a fiber. Five of the 11 maloriented bivalents analyzed exhibited bipolar malorientations that had at least four times more kinetochore microtubules to one pole than to the other pole, and two had microtubules directed to only one pole. Yet all maloriented bivalents had positions at or near the spindle equator. The traction fiber model predicts such maloriented bivalents should be positioned closer to the pole with more kinetochore microtubules. A metaphase position at the spindle equator, according to the model, requires equal numbers of kinetochore microtubules to both poles. Data from polarizing microscope images were not in accord with those predictions, leading to the conclusion that other factors, in addition to traction forces, must be involved in metaphase positioning in crane-fly spermatocytes. Although the identity of additional factors has not been established, one possibility is that polar ejection forces operate to exert away-from-the-pole forces that could counteract pole-directed traction forces. Another is that kinetochores are "smart," meaning they embody a position-sensitive mechanism that controls their activity.


Mol Biol Cell


LaFountain JR Jr,Oldenbourg R





Has Abstract


2004-12-01 00:00:00














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    journal_title:Molecular biology of the cell

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    journal_title:Molecular biology of the cell

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  • Dynamic association of the PI3P-interacting Mon1-Ccz1 GEF with vacuoles is controlled through its phosphorylation by the type 1 casein kinase Yck3.

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    authors: Vigneron S,Prieto S,Bernis C,Labbé JC,Castro A,Lorca T

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    abstract::Fusion of yeast vacuoles requires the Rab GTPase Ypt7p, four SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptors), the SNARE disassembly chaperones Sec17p/Sec18p, vacuolar lipids, and the Rab-effector complex HOPS (homotypic fusion and vacuole protein sorting). Two HOPS subunits have direct ...

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    abstract::Rapid β2-integrin activation is indispensable for leukocyte adhesion and recruitment to sites of infection and is mediated by chemokine- or P-selectin glycoprotein ligand-1-induced inside-out signaling. Here we uncovered a novel pathway for rapid activation of integrin-dependent leukocyte adhesion, triggered by toll-l...

    journal_title:Molecular biology of the cell

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    authors: Chung KJ,Mitroulis I,Wiessner JR,Zheng YY,Siegert G,Sperandio M,Chavakis T

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  • Distribution and transport of cholesterol in Caenorhabditis elegans.

    abstract::Cholesterol transport is an essential process in all multicellular organisms. In this study we applied two recently developed approaches to investigate the distribution and molecular mechanisms of cholesterol transport in Caenorhabditis elegans. The distribution of cholesterol in living worms was studied by imaging it...

    journal_title:Molecular biology of the cell

    pub_type: 杂志文章


    authors: Matyash V,Geier C,Henske A,Mukherjee S,Hirsh D,Thiele C,Grant B,Maxfield FR,Kurzchalia TV

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  • Receptor-mediated cell mechanosensing.

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    pub_type: 杂志文章,评审


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  • Binding the atypical RA domain of Ste50p to the unfolded Opy2p cytoplasmic tail is essential for the high-osmolarity glycerol pathway.

    abstract::Activation of the high-osmolarity glycerol (HOG) pathway for osmoregulation in the yeast Saccharomyces cerevisiae involves interaction of the adaptor Ste50p with the cytoplasmic tail of single-transmembrane protein Opy2p. We have determined the solution structure of the Ste50p-RA (Ras association) domain, and it shows...

    journal_title:Molecular biology of the cell

    pub_type: 杂志文章


    authors: Ekiel I,Sulea T,Jansen G,Kowalik M,Minailiuc O,Cheng J,Harcus D,Cygler M,Whiteway M,Wu C

    更新日期:2009-12-01 00:00:00

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    abstract::The potential to migrate is one of the most fundamental functions for various epithelial, mesenchymal, and immune cells. Image analysis of motile cell populations, both primary and cultured, typically reveals an intercellular variability in migration speeds. However, cell migration chromatography, the sorting of large...

    journal_title:Molecular biology of the cell

    pub_type: 杂志文章


    authors: Arora A,Niño JLG,Myaing MZ,Chia S,Arasi B,Ravasio A,Huang RY,Dasgupta R,Biro M,Viasnoff V

    更新日期:2020-12-01 00:00:00

  • Constitutively active G protein-coupled receptor mutants block dictyostelium development.

    abstract::cAR1, a G protein-coupled receptor (GPCR) for cAMP, is required for the multicellular development of Dictyostelium. The activation of multiple pathways by cAR1 is transient because of poorly defined adaptation mechanisms. To investigate this, we used a genetic screen for impaired development to isolate four dominant-n...

    journal_title:Molecular biology of the cell

    pub_type: 杂志文章


    authors: Zhang M,Goswami M,Hereld D

    更新日期:2005-02-01 00:00:00

  • Rab GDI: a solubilizing and recycling factor for rab9 protein.

    abstract::Rab proteins are thought to function in the processes by which transport vesicles identify and/or fuse with their respective target membranes. The bulk of these proteins are membrane associated, but a measurable fraction can be found in the cytosol. The cytosolic forms of rab3A, rab11, and Sec4 occur as equimolar comp...

    journal_title:Molecular biology of the cell

    pub_type: 杂志文章


    authors: Soldati T,Riederer MA,Pfeffer SR

    更新日期:1993-04-01 00:00:00

  • Endobrevin/VAMP-8 is the primary v-SNARE for the platelet release reaction.

    abstract::Platelet secretion is critical to hemostasis. Release of granular cargo is mediated by soluble NSF attachment protein receptors (SNAREs), but despite consensus on t-SNAREs usage, it is unclear which Vesicle Associated Membrane Protein (VAMPs: synaptobrevin/VAMP-2, cellubrevin/VAMP-3, TI-VAMP/VAMP-7, and endobrevin/VAM...

    journal_title:Molecular biology of the cell

    pub_type: 杂志文章


    authors: Ren Q,Barber HK,Crawford GL,Karim ZA,Zhao C,Choi W,Wang CC,Hong W,Whiteheart SW

    更新日期:2007-01-01 00:00:00

  • Mammalian septins are required for phagosome formation.

    abstract::Septins are members of a highly conserved family of filamentous proteins that are required in many organisms for the completion of cytokinesis. In addition, septins have been implicated in a number of important cellular processes and have been suggested to have roles in regulating membrane traffic. Given the proposed ...

    journal_title:Molecular biology of the cell

    pub_type: 杂志文章


    authors: Huang YW,Yan M,Collins RF,Diciccio JE,Grinstein S,Trimble WS

    更新日期:2008-04-01 00:00:00

  • Chlamydomonas IFT70/CrDYF-1 is a core component of IFT particle complex B and is required for flagellar assembly.

    abstract::DYF-1 is a highly conserved protein essential for ciliogenesis in several model organisms. In Caenorhabditis elegans, DYF-1 serves as an essential activator for an anterograde motor OSM-3 of intraflagellar transport (IFT), the ciliogenesis-required motility that mediates the transport of flagellar precursors and remov...

    journal_title:Molecular biology of the cell

    pub_type: 杂志文章


    authors: Fan ZC,Behal RH,Geimer S,Wang Z,Williamson SM,Zhang H,Cole DG,Qin H

    更新日期:2010-08-01 00:00:00