CENP-E Is a Plus End–Directed Kinetochore Motor Required for Metaphase Chromosome Alignment

Abstract

Mitosis requires dynamic attachment of chromosomes to spindle microtubules. This interaction is mediated largely by kinetochores. During prometaphase, forces exerted at kinetochores, in combination with polar ejection forces, drive congression of chromosomes to the metaphase plate. A major question has been whether kinetochore-associated microtubule motors play an important role in congression. Using immunodepletion from and antibody addition to Xenopus egg extracts, we show that the kinetochore-associated kinesin-like motor protein CENP-E is essential for positioning chromosomes at the metaphase plate. We further demonstrate that CENP-E powers movement toward microtubule plus ends in vitro. These findings support a model in which CENP-E functions in congression to tether kinetochores to dynamic microtubule plus ends.

CENP-meta, an Essential Kinetochore Kinesin Required for the Maintenance of Metaphase Chromosome Alignment in Drosophila

“…4, A–C). These data suggest a role for CENP-meta in chromosome congression, or the maintenance of that congression, in agreement with the model proposed earlier from experiments showing misalignment of chromosomes in spindles assembled in vitro using Xenopus egg extracts depleted of CENP-E (Wood et al 1997). Additionally, the chromosomes sometimes appear to be undercondensed, perhaps as a secondary consequence of mitotic arrest.…”

“…CENP-E has also been implicated in the dynamic attachment of kinetochores to disassembling microtubules in vitro (Lombillo et al 1995). Together, the available data suggest a general model in which plus-end directed kinesins, such as CENP-E (Wood et al 1997), are required during chromosome congression to power the movement of the trailing kinetochores towards the unstable microtubule plus ends. In addition, such kinesins may tether the kinetochore to the spindle microtubules (Lombillo et al 1995; Wood et al 1997) and perhaps play a crucial role in signaling the mitotic checkpoint machinery about the status of chromosome capture and/or alignment.…”

“…A number of important kinetochore components have been identified. Among these are several motor proteins from the kinesin superfamily including CENP-E (Yen et al 1992; Wood et al 1997), the MCAK/XKCM1 family (Wordeman and Mitchison 1995; Walczak et al 1996; Maney et al 1998), and cytoplasmic dynein and its associated components (Steuer et al 1990; Pfarr et al 1990). Besides motor enzymes, a number of other proteins are at least transiently associated with kinetochores during mitosis.…”

“…Consistent with this view, microinjection of cells with antibodies specific for CENP-E caused a delay in anaphase onset (Yen et al 1991) and a misalignment of chromosomes (Schaar et al 1997). Similarly, both immunodepletion and inhibitory antibody addition experiments with Xenopus cell-free extracts caused failure in chromosome alignment at metaphase (Wood et al 1997), while antisense oligonucleotide meditated suppression of CENP-E accumulation in mammalian cultured cells yields chronically mono-oriented chromosomes with spindles flattened along the plane of the substrate (Yao et al 2000). …”

“…For example, the relocalization of CENP-E to the midzone at anaphase-B may indicate an additional role for this plus-end motor (Wood et al 1997) in spindle elongation and/or cytokinesis. CENP-E has also been implicated as part of, or a target of, the spindle assembly checkpoint based on a physical interaction with the spindle assembly protein hBubR1 (Chan et al 1998, Chan et al 1999; Yao et al 2000).…”