Portal de Periódicos da CAPES

Mechanisms of Spindle-Pole Organization Are Influenced by Kinetochore Activity in Mammalian Cells

2007; Elsevier BV; Volume: 17; Issue: 3 Linguagem: Inglês

10.1016/j.cub.2006.11.071

1879-0445

Amity L. Manning, Duane A. Compton,

Protist diversity and phylogeny

The spindle is a fusiform bipolar-microtubule array that is responsible for chromosome segregation during mitosis [1Wittman T. Hyman A.A. Desai A. The spindle: A dynamic assembly of microtubules and motors.Nat. Cell Biol. 1996; 3: E28-E34Crossref Scopus (396) Google Scholar, 2Hyman A.A. Karsenti E. Morphogenetic properties of microtubules and mitotic spindle assembly.Cell. 1996; 84: 401-410Abstract Full Text Full Text PDF PubMed Scopus (246) Google Scholar, 3Compton D.A. Spindle assembly in animal cells.Annu. Rev. Biochem. 2000; 69: 95-114Crossref PubMed Scopus (223) Google Scholar, 4Wadsworth P. Khodjakov A. E pluribus unum: Towards a universal mechanism for spindle assembly.Trends Cell Biol. 2004; 14: 413-419Abstract Full Text Full Text PDF PubMed Scopus (91) Google Scholar]. Focused poles are an essential feature of spindles in vertebrate somatic cells, and pole focusing has been shown to occur through a centrosome-independent self-organization mechanism where microtubule motors cross-link and focus microtubule minus ends [4Wadsworth P. Khodjakov A. E pluribus unum: Towards a universal mechanism for spindle assembly.Trends Cell Biol. 2004; 14: 413-419Abstract Full Text Full Text PDF PubMed Scopus (91) Google Scholar, 5Gaglio T. Saredi A. Compton D.A. NuMA is required for the organization of microtubules into aster-like mitotic arrays.J. Cell Biol. 1995; 131: 693-708Crossref PubMed Scopus (214) Google Scholar, 6Compton D.A. Focusing on spindle poles.J. Cell Sci. 1998; 111: 1477-1481Crossref PubMed Google Scholar, 7Heald R. Tournebize R. Haberman A. Karsenti E. Hyman A.A. Self-organization of microtubule into bipolar spindles around artificial chromosomes in Xenopus egg extracts.Nature. 1996; 382: 420-425Crossref PubMed Scopus (752) Google Scholar, 8Merdes A. Ramyar K. Vechio J.D. Cleveland D.W. A complex of NuMA and cytoplasmic dynein is essential for mitotic spindle assembly.Cell. 1996; 87: 447-458Abstract Full Text Full Text PDF PubMed Scopus (454) Google Scholar, 9Gaglio T. Saredi A. Bingham J.R. Hasbani M.J. Gill S.R. Schroer T.A. Compton D.A. Opposing motors activities are required for the organization of the mammalian mitotic spindle pole.J. Cell Biol. 1996; 135: 399-414Crossref PubMed Scopus (251) Google Scholar, 10Verde F. Berrez J.-M. Antony C. Karsenti E. Taxol-induced microtubule asters in mitotic extracts of Xenopus eggs: Requirement for phosphorylated factors and cytoplasmic dynein.J. Cell Biol. 1991; 112: 1177-1187Crossref PubMed Scopus (236) Google Scholar, 11Goshima G. Nedelec F. Vale R.D. Mechanisms for focusing mitotic spindle poles by minus end-directed motor proteins.J. Cell Biol. 2005; 171: 229-240Crossref PubMed Scopus (194) Google Scholar]. Most of our understanding of this mechanism for pole focusing derives from studies performed in cell-free extracts devoid of centrosomes and kinetochores [5Gaglio T. Saredi A. Compton D.A. NuMA is required for the organization of microtubules into aster-like mitotic arrays.J. Cell Biol. 1995; 131: 693-708Crossref PubMed Scopus (214) Google Scholar, 7Heald R. Tournebize R. Haberman A. Karsenti E. Hyman A.A. Self-organization of microtubule into bipolar spindles around artificial chromosomes in Xenopus egg extracts.Nature. 1996; 382: 420-425Crossref PubMed Scopus (752) Google Scholar, 9Gaglio T. Saredi A. Bingham J.R. Hasbani M.J. Gill S.R. Schroer T.A. Compton D.A. Opposing motors activities are required for the organization of the mammalian mitotic spindle pole.J. Cell Biol. 1996; 135: 399-414Crossref PubMed Scopus (251) Google Scholar, 10Verde F. Berrez J.-M. Antony C. Karsenti E. Taxol-induced microtubule asters in mitotic extracts of Xenopus eggs: Requirement for phosphorylated factors and cytoplasmic dynein.J. Cell Biol. 1991; 112: 1177-1187Crossref PubMed Scopus (236) Google Scholar]. Here, we examine how sustained force from kinetochores influences the mechanism of pole focusing in cultured cells. We show that the motor-driven self-organization activities associated with NuMA (i.e., cytoplasmic dynein) and HSET are not necessary for pole focusing if sustained force from kinetochores is inhibited in Nuf2- or Mis12-deficient cells. Instead, pole organization relies on TPX2 as it cross-links spindle microtubules to centrosome-associated mitotic asters. Thus, both motor-driven and static-cross-linking mechanisms contribute to spindle-pole organization, and kinetochore activity influences the mechanism of spindle-pole organization. The motor-driven self-organization of microtubule minus ends at spindle poles is needed to organize spindle poles in vertebrate somatic cells when kinetochores actively exert force on spindle microtubules.