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    Regulation of microtubule dynamics by reaction cascades around chromosomes (2008)
    American Association for the Advancement of Science (AAAS)
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    Publikationsdatum: 2008-10-25
    Beschreibung: During spindle assembly, chromosomes generate gradients of microtubule stabilization through a reaction-diffusion process, but how this is achieved is not well understood. We measured the spatial distribution of microtubule aster asymmetry around chromosomes by incubating centrosomes and micropatterned chromatin patches in frog egg extracts. We then screened for microtubule stabilization gradient shapes that would generate such spatial distributions with the use of computer simulations. Only a long-range, sharply decaying microtubule stabilization gradient could generate aster asymmetries fitting the experimental data. We propose a reaction-diffusion model that combines the chromosome generated Ran-guanosine triphosphate-Importin reaction network to a secondary phosphorylation network as a potential mechanism for the generation of such gradients.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Athale, Chaitanya A -- Dinarina, Ana -- Mora-Coral, Maria -- Pugieux, Celine -- Nedelec, Francois -- Karsenti, Eric -- New York, N.Y. -- Science. 2008 Nov 21;322(5905):1243-7. doi: 10.1126/science.1161820. Epub 2008 Oct 23.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Cell Biology and Biophysics Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, Heidelberg, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18948504" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Cell Cycle Proteins/physiology ; Centrosome/physiology ; Chromatin/physiology ; Chromosomes, Human/physiology ; Computer Simulation ; Diffusion ; Humans ; Microtubule-Associated Proteins/physiology ; Microtubules/*physiology ; Models, Biological ; Nuclear Proteins/physiology ; Ovum/cytology ; Phosphoproteins/physiology ; Spindle Apparatus/*physiology ; Xenopus ; Xenopus Proteins/physiology ; ran GTP-Binding Protein/metabolism
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
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    Threshold effect of growth rate on population variability of Escherichia coli cell lengths (2017)
    Royal Society
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    Publikationsdatum: 2017-02-25
    Beschreibung: A long-standing question in biology is the effect of growth on cell size. Here, we estimate the effect of Escherichia coli growth rate ( r ) on population cell size distributions by estimating the coefficient of variation of cell lengths (CV L ) from image analysis of fixed cells in DIC microscopy. We find that the CV L is constant at growth rates less than one division per hour, whereas above this threshold, CV L increases with an increase in the growth rate. We hypothesize that stochastic inhibition of cell division owing to replication stalling by a RecA-dependent mechanism, combined with the growth rate threshold of multi-fork replication (according to Cooper and Helmstetter), could form the basis of such a threshold effect. We proceed to test our hypothesis by increasing the frequency of stochastic stalling of replication forks with hydroxyurea (HU) treatment and find that cell length variability increases only when the growth rate exceeds this threshold. The population effect is also reproduced in single-cell studies using agar-pad cultures and ‘mother machine’-based experiments to achieve synchrony. To test the role of RecA, critical for the repair of stalled replication forks, we examine the CV L of E. coli recA cells. We find cell length variability in the mutant to be greater than wild-type, a phenotype that is rescued by plasmid-based RecA expression. Additionally, we find that RecA-GFP protein recruitment to nucleoids is more frequent at growth rates exceeding the growth rate threshold and is further enhanced on HU treatment. Thus, we find growth rates greater than a threshold result in increased E. coli cell lengths in the population, and this effect is, at least in part, mediated by RecA recruitment to the nucleoid and stochastic inhibition of division.
    Schlagwort(e): microbiology, biophysics, cellular biology
    Digitale ISSN: 2054-5703
    Thema: Allgemeine Naturwissenschaft
    Publiziert von Royal Society
    Standort Signatur Erwartet Verfügbarkeit
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