Abstract
Chromosome congression is the alignment of chromosomes at the spindle equator, and is a prerequisite for faithful chromosome segregation. Recent data suggest that before kinetochores attach to the end of microtubules (end-on attachment), chromosomes can move along microtubules towards the spindle equator through attachment of kinetochores to the lateral surface of microtubules (lateral attachment). Here we address this mechanism, focusing on the contribution of two mitotic motors, Kid and CENP-E. In cells depleted of Hec1, which is essential for end-on attachment, chromosomes show partial and transient congression. This transient congression is further perturbed by co-depletion of Kid, suggesting its role in chromosome congression. In comparison, CENP-E suppresses chromosome congression, probably by tethering kinetochores to short, unstable microtubules, and works in congression only when microtubules are stabilized. Our results may reflect the differential contributions of Kid and CENP-E in chromosome congression in physiological conditions where stabilized microtubules are becoming increased.
Highlights
Chromosome congression is the alignment of chromosomes at the spindle equator, and is a prerequisite for faithful chromosome segregation
Congression of laterally attached chromosomes is thought to be achieved by transport along spindle microtubules by CENP-E2,4, a microtubule plusend-directed motor of the kinesin-7 family localizing to kinetochores[5], and polar ejection forces (PEFs)[6] exerted mainly by Kid[7,8,9], a chromokinesin of the kinesin-10 family localizing to chromosomes
We propose a model in which Kid and CENP-E cooperatively contribute to chromosome congression in physiological conditions, depending on the stability of spindle microtubules
Summary
Chromosome congression is the alignment of chromosomes at the spindle equator, and is a prerequisite for faithful chromosome segregation. Recent data suggest that before kinetochores attach to the end of microtubules (end-on attachment), chromosomes can move along microtubules towards the spindle equator through attachment of kinetochores to the lateral surface of microtubules (lateral attachment) We address this mechanism, focusing on the contribution of two mitotic motors, Kid and CENP-E. In cells depleted of Hec[1], which is essential for end-on attachment, chromosomes show partial and transient congression. Our results may reflect the differential contributions of Kid and CENP-E in chromosome congression in physiological conditions where stabilized microtubules are becoming increased. Recent data suggest that chromosome congression can occur in the absence of bi-orientation, and bi-orientation is established at the spindle equator while lateral attachment is converted to end-on attachment[2,3]. We propose a model in which Kid and CENP-E cooperatively contribute to chromosome congression in physiological conditions, depending on the stability of spindle microtubules
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