Mitotic Spindle Poles are Organized by Structural and Motor Proteins in Addition to Centrosomes
Open Access
- 8 September 1997
- journal article
- Published by Rockefeller University Press in The Journal of cell biology
- Vol. 138 (5) , 1055-1066
- https://doi.org/10.1083/jcb.138.5.1055
Abstract
The focusing of microtubules into mitotic spindle poles in vertebrate somatic cells has been assumed to be the consequence of their nucleation from centrosomes. Contrary to this simple view, in this article we show that an antibody recognizing the light intermediate chain of cytoplasmic dynein (70.1) disrupts both the focused organization of microtubule minus ends and the localization of the nuclear mitotic apparatus protein at spindle poles when injected into cultured cells during metaphase, despite the presence of centrosomes. Examination of the effects of this dynein-specific antibody both in vitro using a cell-free system for mitotic aster assembly and in vivo after injection into cultured cells reveals that in addition to its direct effect on cytoplasmic dynein this antibody reduces the efficiency with which dynactin associates with microtubules, indicating that the antibody perturbs the cooperative binding of dynein and dynactin to microtubules during spindle/aster assembly. These results indicate that microtubule minus ends are focused into spindle poles in vertebrate somatic cells through a mechanism that involves contributions from both centrosomes and structural and microtubule motor proteins. Furthermore, these findings, together with the recent observation that cytoplasmic dynein is required for the formation and maintenance of acentrosomal spindle poles in extracts prepared from Xenopus eggs (Heald, R., R. Tournebize, T. Blank, R. Sandaltzopoulos, P. Becker, A. Hyman, and E. Karsenti. 1996. Nature (Lond.). 382: 420–425) demonstrate that there is a common mechanism for focusing free microtubule minus ends in both centrosomal and acentrosomal spindles. We discuss these observations in the context of a search-capture-focus model for spindle assembly.Keywords
This publication has 75 references indexed in Scilit:
- Pathways of spindle assemblyCurrent Opinion in Cell Biology, 1997
- A Complex of NuMA and Cytoplasmic Dynein Is Essential for Mitotic Spindle AssemblyCell, 1996
- Opposing motor activities are required for the organization of the mammalian mitotic spindle pole.The Journal of cell biology, 1996
- Self-organization of microtubules into bipolar spindles around artificial chromosomes in Xenopus egg extractsNature, 1996
- Phosphorylation by p34cdc2 regulates spindle association of human Eg5, a kinesin-related motor essential for bipolar spindle formation in vivoPublished by Elsevier ,1995
- Taxol-induced microtubule asters in mitotic extracts of Xenopus eggs: requirement for phosphorylated factors and cytoplasmic dynein.The Journal of cell biology, 1991
- Aster-free spindle poles in insect spermatocytes: evidence for chromosome-induced spindle formation?The Journal of cell biology, 1986
- Centrosomes and mitotic polesExperimental Cell Research, 1984
- 10-nm filaments are induced to collapse in living cells microinjected with monoclonal and polyclonal antibodies against tubulin.The Journal of cell biology, 1984
- The absence of centrioles from spindle poles of rat kangaroo (PtK2) cells undergoing meiotic-like reduction division in vitro.The Journal of cell biology, 1977