The Journal of Cell Biology, Vol 110, 391-404, Copyright © 1990 by The Rockefeller University Press

ARTICLES

Poleward force at the kinetochore in metaphase depends on the number of kinetochore microtubules

TS Hays and ED Salmon
Biology Department, University of North Carolina, Chapel Hill 27514.

To examine the dependence of poleward force at a kinetochore on the number of kinetochore microtubules (kMTs), we altered the normal balance in the number of microtubules at opposing homologous kinetochores in meiosis I grasshopper spermatocytes at metaphase with a focused laser microbeam. Observations were made with light and electron microscopy. Irradiations that partially damaged one homologous kinetochore caused the bivalent chromosome to shift to a new equilibrium position closer to the pole to which the unirradiated kinetochore was tethered; the greater the dose of irradiation, the farther the chromosome moved. The number of kMTs on the irradiated kinetochore decreased with severity of irradiation, while the number of kMTs on the unirradiated kinetochore remained constant and independent of chromosome-to-pole distance. Assuming a balance of forces on the chromosome at congression equilibrium, our results demonstrate that the net poleward force on a chromosome depends on the number of kMTs and the distance from the pole. In contrast, the velocity of chromosome movement showed little dependence on the number of kMTs. Possible mechanisms which explain the relationship between the poleward force at a kinetochore, the number of kinetochore microtubules, and the lengths of the kinetochore fibers at congression equilibrium include a "traction fiber model" in which poleward force producers are distributed along the length of the kinetochore fibers, or a "kinetochore motor-polar ejection model" in which force producers located at or near the kinetochore pull the chromosomes poleward along the kMTs and against an ejection force that is produced by the polar microtubule array and increases in strength toward the pole.
CiteULike    Complore    Connotea    Del.icio.us    Digg    Facebook    Reddit    Technorati    Twitter    What's this?

This article has been cited by other articles:

• Villasante, A., Abad, J. P., Mendez-Lago, M. (2007). Centromeres were derived from telomeres during the evolution of the eukaryotic chromosome. Proc. Natl. Acad. Sci. USA 104: 10542-10547 [Abstract] [Full Text]  
• Cui, W., Hawley, R. S. (2005). The HhH(2)/NDD Domain of the Drosophila Nod Chromokinesin-like Protein Is Required for Binding to Chromosomes in the Oocyte Nucleus. Genetics 171: 1823-1835 [Abstract] [Full Text]  
• Rogers, G. C., Rogers, S. L., Sharp, D. J. (2005). Spindle microtubules in flux. J. Cell Sci. 118: 1105-1116 [Abstract] [Full Text]  
• LaFountain, J. R. Jr., Oldenbourg, R. (2004). Maloriented Bivalents Have Metaphase Positions at the Spindle Equator with More Kinetochore Microtubules to One Pole than to the Other. Mol. Biol. Cell 15: 5346-5355 [Abstract] [Full Text]  
• Labbe, J.-C., McCarthy, E. K., Goldstein, B. (2004). The forces that position a mitotic spindle asymmetrically are tethered until after the time of spindle assembly. JCB 167: 245-256 [Abstract] [Full Text]  
• Savoian, M. S., Gatt, M. K., Riparbelli, M. G., Callaini, G., Glover, D. M. (2004). Drosophila Klp67A is required for proper chromosome congression and segregation during meiosis I. J. Cell Sci. 117: 3669-3677 [Abstract] [Full Text]  
• Kapoor, T. M., Compton, D. A. (2002). Searching for the middle ground: mechanisms of chromosome alignment during mitosis. JCB 157: 551-556 [Abstract] [Full Text]  
• LaFountain, J. R. Jr., Oldenbourg, R., Cole, R. W., Rieder, C. L. (2001). Microtubule Flux Mediates Poleward Motion of Acentric Chromosome Fragments during Meiosis in Insect Spermatocytes. Mol. Biol. Cell 12: 4054-4065 [Abstract] [Full Text]  
• Levesque, A. A., Compton, D. A. (2001). The chromokinesin Kid is necessary for chromosome arm orientation and oscillation, but not congression, on mitotic spindles. JCB 154: 1135-1146 [Abstract] [Full Text]  
• Ngan, V. K., Bellman, K., Hill, B. T., Wilson, L., Jordan, M. A. (2001). Mechanism of Mitotic Block and Inhibition of Cell Proliferation by the Semisynthetic Vinca Alkaloids Vinorelbine and Its Newer Derivative Vinflunine. Mol. Pharmacol. 60: 225-232 [Abstract] [Full Text]  
• Rieder, C., Cole, R (1999). Chromatid cohesion during mitosis: lessons from meiosis. J. Cell Sci. 112: 2607-2613 [Abstract]  
• McEwen, B. F., Heagle, A. B., Cassels, G. O., Buttle, K. F., Rieder, C. L. (1997). Kinetochore Fiber Maturation in PtK1 Cells and Its Implications for the Mechanisms of Chromosome Congression and Anaphase Onset. JCB 137: 1567-1580 [Abstract] [Full Text]  
• Waters, J., Skibbens, R., Salmon, E. (1996). Oscillating mitotic newt lung cell kinetochores are, on average, under tension and rarely push. J. Cell Sci. 109: 2823-2831 [Abstract]  
• Skibbens, R., Rieder, C., Salmon, E. (1995). Kinetochore motility after severing between sister centromeres using laser microsurgery: evidence that kinetochore directional instability and position is regulated by tension. J. Cell Sci. 108: 2537-2548 [Abstract]  
• Cassimeris, L, Rieder, C., Salmon, E. (1994). Microtubule assembly and kinetochore directional instability in vertebrate monopolar spindles: implications for the mechanism of chromosome congression. J. Cell Sci. 107: 285-297 [Abstract]  

Home | Help | Feedback | Subscriptions | Archive | Search | Table of Contents