Mitosis, microtubules, and the matrix - PubMed (original) (raw)

Review

Mitosis, microtubules, and the matrix

J M Scholey et al. J Cell Biol. 2001.

Abstract

The mechanical events of mitosis depend on the action of microtubules and mitotic motors, but whether these spindle components act alone or in concert with a spindle matrix is an important question.

PubMed Disclaimer

Figures

Figure 1.

Figure 1.

Skeletor and the microtrabecular lattice. (A and B) The skeletor matrix. Skeletor forms a reticular matrix around condensing chromosomes in the absence of MTs during prophase (A). As the nuclear envelope fenestrates and microtubules enter the nuclear region during prometaphase, the skeletor matrix organizes and stabilizes microtubules in the central spindle, providing support for the fusiform morphology of the spindle through metaphase (B). (C and D) The microtrabecular lattice matrix. A spring-like lattice associated with chromosomes forms around kinetochore microtubules. During prometaphase and metaphase (C) this lattice is deformed or stretched toward the metaphase plate by plus end–directed motors (shown attached to the fibrous corona). At anaphase (D), these motors are turned off and the elastic recoil of the matrix drives the poleward movement of chromosomes.

Figure 2.

Figure 2.

The NuMA matrix and MT–MT cross-linking motors. (A) The NuMA matrix. The NuMA protein oligomerizes into a highly branched and cross-linked lattice around the spindle poles. Because NuMA is believed to associate with both microtubules and certain mitotic motors, such a matrix could anchor and cross-link microtubules and also immobilize motors at or near the poles. The latter activity would provide a stationary substrate for motor-driven MT transport within the spindle, allowing minus end–directed motors such as cytoplasmic dynein to focus the minus ends of MTs at the poles and plus end–directed motors such as bipolar kinesins to cross-link polar microtubules into asters and drive the poleward flux of kinetochore microtubules. (B) A matrix of MT–MT cross-linking and sliding motors. The spindle is packed with a dense array of MT–MT cross-linking and sliding motors. Specific interactions that occur between these motors and spindle MTs drive the formation and function of the spindle. (Inset, top left) Bipolar kinesins such as KLP61F can cross-link parallel MTs into bundles, thus contributing to the organization of MTs in the half spindles, but generate no net axial force between them. (Inset, top right) In contrast, when bipolar kinesins cross-link antiparallel MTs into bundles, they can generate paraxial force and thus slide them in relation to one another. Asymmetric motors like dynein and Ncd can presumably cross-link and slide either parallel or antiparallel MTs in relation to one another, dependent upon the nature of the binding between their nucleotide-insensitive MT binding site and the MT surface lattice, and the polarity of motion driven by their motor domains.

Similar articles

Cited by

References

    1. Bi, G., R.L. Morris, G. Liao, J.M. Alderton, J.M. Scholey, and R.A. Steinhardt. 1997. Kinesin- and myosin-driven steps of vesicle recruitment for Ca2+-regulated exocytosis. J. Cell Biol. 138:999–1008. - PMC - PubMed
    1. Blangy, A., L. Arnaud, and E.A. Nigg. 1997. Phosphorylation by p34cdc2 protein kinase regulates binding of the kinesin-related motor HsEg5 to the dynactin subunit p150Glued. J. Biol. Chem. 272:19418–19424. - PubMed
    1. Compton, D.A. 2000. Spindle assembly in animal cells. Annu. Rev. Biochem. 69:95–114. - PubMed
    1. Cullen, C.F., and H. Ohkura. 2001. Msps protein is localized to acentrosomal poles to ensure bipolarity of Drosophila meiotic spindles. Nat. Cell Biol. 3:637–642. - PubMed
    1. Debec, A., R.F. Kalpin, D.R. Daily, P.D. McCallum, W.F. Rothwell, and W. Sullivan. 1996. Live analysis of free centrosomes in normal and aphidicolin-treated Drosophila embryos. J. Cell Biol. 134:103–115. - PMC - PubMed

Publication types

MeSH terms

Substances

LinkOut - more resources