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|Authors: ||VandenBeldt, Kristin J.|
Barnard, Rita M.
Hergert, Polla J.
McEwen, Bruce F.
|Title: ||Kinetochores Use a Novel Mechanism for Coordinating the Dynamics of Individual Microtubules|
|Alternative title: ||Microtubule dynamics and kinetochore function|
|Issue Date: ||2006|
|Abstract: ||Chromosome alignment during mitosis is frequently accompanied by a dynamic
switching between elongation and shortening of kinetochore fibers (K-fibers) that connect
kinetochores and spindle poles [1, 2]. In higher eukaryotes, mature K-fibers consist of 10–30
kinetochore microtubules (kMTs) whose plus-ends are embedded in the kinetochore [1-3]. A
critical and long-standing question is how the dynamics of individual kMTs within the K-fiber
are coordinated [1-5]. We have addressed this question by using electron tomography to
determine the polymerization/depolymerization status of individual kMTs in the K-fibers of
PtK1 and Drosophila S2 cells. Surprisingly, we find that the plus-ends of two-thirds of kMTs
are in a depolymerizing state, even when the K-fiber exhibits net tubulin incorporation at the plus
end [6-8]. Furthermore, almost all individual K-fibers examined had a mixture of kMTs in the
polymerizing and depolymerizing states. Therefore, although K-fibers elongate and shrink as a
unit, the dynamics of individual kMTs within a K-fiber are not coordinated at any given moment.
Our results suggest a novel control mechanism through which attachment to the kinetochore
outer plate prevents shrinkage of kMTs. We discuss the ramifications of this new model on the
regulation of chromosome movement and the stability of K-fibers.|
|Source: ||Current Biology, vol.(12), p.1217-1223|
|Document Type : ||Artigo em Revista Científica Internacional|
|Appears in Collections:||IBMC - Artigo em Revista Científica Internacional|
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