Dogterom, M. and Félix, M. A. and Guet, C. C. and Leibler, S. (1996) Influence of M-phase chromatin on the anisotropy of microtubule asters. Journal of Cell Biology, 133 (1). pp. 125-140. ISSN 0021-9525 http://resolver.caltech.edu/CaltechAUTHORS:20120202-094636381
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In many eukaryotic cells going through M-phase, a bipolar spindle is formed by microtubules nucleated from centrosomes. These microtubules, in addition to being "captured" by kinetochores, may be stabilized by chromatin in two different ways: short-range stabilization effects may affect microtubules in close contact with the chromatin, while long-range stabilization effects may "guide" microtubule growth towards the chromatin (e.g., by introducing a diffusive gradient of an enzymatic activity that affects microtubule assembly). Here, we use both meiotic and mitotic extracts from Xenopus laevis eggs to study microtubule aster formation and microtubule dynamics in the presence of chromatin. In "low-speed" meiotic extracts, in the presence of salmon sperm chromatin, we find that short-range stabilization effects lead to a strong anisotropy of the microtubule asters. Analysis of the dynamic parameters of microtubule growth show that this anisotropy arises from a decrease in the catastrophe frequency, an increase in the rescue frequency and a decrease in the growth velocity. In this system we also find evidence for long-range "guidance" effects, which lead to a weak anisotropy of the asters. Statistically relevant results on these long-range effects are obtained in "high-speed" mitotic extracts in the presence of artificially constructed chromatin stripes. We find that aster anisotropy is biased in the direction of the chromatin and that the catastrophe frequency is reduced in its vicinity. In this system we also find a surprising dependence of the catastrophe and the rescue frequencies on the length of microtubules nucleated from centrosomes: the catastrophe frequency increase and the rescue frequency decreases with microtubule length.
|Additional Information:||© 1996 Rockefeller University Press. Received for publication 19 October 1995 and in revised form 18 January 1996. Published April 1, 1996. We would like to thank T. Holly and T. Mitchison for providing us with centrosomes; M. Glotzer and T. Mitchison for giving us the plasmid for Δ90 cyclin B; J. Stock and members of his laboratory for help with biochemical preparations; R. Zimmerman for help with the biotinylation of DNA; J. Shepherd for help with the patterning of surfaces; D. Tsui for use of his clean room facility, and D. Fygenson, T. Holy, E. Karsenti, E. Kennedy, A. Levine, T. Mitchison, and G. Waters for valuable discussions, constant encouragement and technical help. This work was partially supported by the National Institutes of Health (Grant No. GM-50712) and the Human Frontier Science Program.|
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|Deposited By:||Tony Diaz|
|Deposited On:||24 Feb 2012 19:33|
|Last Modified:||26 Dec 2012 14:46|
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