The Role of Xgrip210 in γ-Tubulin Ring Complex Assembly and Centrosome Recruitment

The γ-tubulin ring complex (γTuRC), purified from the cytoplasm of vertebrate and invertebrate cells, is a microtubule nucleator in vitro. Structural studies have shown that γTuRC is a structure shaped like a lock-washer and topped with a cap. Microtubules are thought to nucleate from the uncapped side of the γTuRC. Consequently, the cap structure of the γTuRC is distal to the base of the microtubules, giving the end of the microtubule the shape of a pointed cap. Here, we report the cloning and characterization of a new subunit of Xenopus γTuRC, Xgrip210. We show that Xgrip210 is a conserved centrosomal protein that is essential for the formation of γTuRC. Using immunogold labeling, we found that Xgrip210 is localized to the ends of microtubules nucleated by the γTuRC and that its localization is more distal, toward the tip of the γTuRC-cap structure, than that of γ-tubulin. Immunodepletion of Xgrip210 blocks not only the assembly of the γTuRC, but also the recruitment of γ-tubulin and its interacting protein, Xgrip109, to the centrosome. These results suggest that Xgrip210 is a component of the γTuRC cap structure that is required for the assembly of the γTuRC.

[1]  A. Iwamatsu,et al.  Characterization and Reconstitution of Drosophila γ-Tubulin Ring Complex Subunits , 2000, The Journal of cell biology.

[2]  D. Agard,et al.  Structure of the γ-tubulin ring complex: a template for microtubule nucleation , 2000, Nature Cell Biology.

[3]  T. J. Keating,et al.  Immunostructural evidence for the template mechanism of microtubule nucleation , 2000, Nature Cell Biology.

[4]  Yixian Zheng,et al.  A new function for the γ -tubulin ring complex as a microtubule minus-end cap , 2000, Nature Cell Biology.

[5]  Yixian Zheng,et al.  Gamma-tubulin complexes and their interaction with microtubule-organizing centers. , 1999, Current opinion in structural biology.

[6]  Timothy J. Mitchison,et al.  Characterization of Two Related Drosophila γ-tubulin Complexes that Differ in Their Ability to Nucleate Microtubules , 1999, The Journal of cell biology.

[7]  B. Alberts,et al.  Recruitment of the γ-Tubulin Ring Complex to Drosophila Salt-stripped Centrosome Scaffolds , 1998, The Journal of cell biology.

[8]  B. Alberts,et al.  Recruitment of the gamma-tubulin ring complex to Drosophila salt-stripped centrosome scaffolds. , 1998 .

[9]  A Khodjakov,et al.  The disassembly and reassembly of functional centrosomes in vitro. , 1998, Proceedings of the National Academy of Sciences of the United States of America.

[10]  A. Hyman,et al.  The role of nucleation in patterning microtubule networks. , 1998, Journal of cell science.

[11]  A. Iwamatsu,et al.  Xgrip109: A γ Tubulin–Associated Protein with an Essential Role in γ Tubulin Ring Complex (γTuRC) Assembly and Centrosome Function , 1998, The Journal of cell biology.

[12]  Eric Karsenti,et al.  Spindle Assembly in Xenopus Egg Extracts: Respective Roles of Centrosomes and Microtubule Self-Organization , 1997, The Journal of cell biology.

[13]  G. Tavosanis,et al.  Essential role for γ‐tubulin in the acentriolar female meiotic spindle of Drosophila , 1997, The EMBO journal.

[14]  T. Mitchison,et al.  Microtubule polymerization dynamics. , 1997, Annual review of cell and developmental biology.

[15]  J. Mulholland,et al.  Analysis of Tub4p, a yeast gamma-tubulin-like protein: implications for microtubule-organizing center function , 1996, The Journal of cell biology.

[16]  E. Schiebel,et al.  gamma-Tubulin-like Tub4p of Saccharomyces cerevisiae is associated with the spindle pole body substructures that organize microtubules and is required for mitotic spindle formation , 1996, The Journal of cell biology.

[17]  Yixian Zheng,et al.  Nucleation of microtubule assembly by a γ-tubulin-containing ring complex , 1995, Nature.

[18]  M. Snyder,et al.  A highly divergent gamma-tubulin gene is essential for cell growth and proper microtubule organization in Saccharomyces cerevisiae , 1995, The Journal of cell biology.

[19]  D A Agard,et al.  Three-dimensional structural characterization of centrosomes from early Drosophila embryos , 1995, The Journal of cell biology.

[20]  C. Sunkel,et al.  Gamma‐tubulin is required for the structure and function of the microtubule organizing centre in Drosophila neuroblasts. , 1995, The EMBO journal.

[21]  B. Alberts,et al.  Nucleation of microtubule assembly by a gamma-tubulin-containing ring complex. , 1995, Nature.

[22]  T. Mitchison,et al.  A heterodimeric coiled-coil protein required for mitotic chromosome condensation in vitro , 1994, Cell.

[23]  M. Kirschner,et al.  In vitro reconstitution of centrosome assembly and function: The central role of γ-tubulin , 1994, Cell.

[24]  M. Félix,et al.  Centrosome assembly in vitro: role of gamma-tubulin recruitment in Xenopus sperm aster formation , 1994, The Journal of cell biology.

[25]  B. Alberts,et al.  The centrosome and cellular organization. , 1994, Annual review of biochemistry.

[26]  B. Oakley.  γ-Tubulin: the microtubule organizer? , 1992 .

[27]  M. Yanagida,et al.  The fission yeast gamma-tubulin is essential for mitosis and is localized at microtubule organizing centers. , 1991, Journal of cell science.

[28]  B. Oakley,et al.  γ-tubulin is a component of the spindle pole body that is essential for microtubule function in Aspergillus nidulans , 1990, Cell.

[29]  B. Oakley,et al.  Identification of γ-tubulin, a new member of the tubulin superfamily encoded by mipA gene of Aspergillus nidulans , 1989, Nature.

[30]  M. Kirschner,et al.  Microtubule assembly nucleated by isolated centrosomes , 1984, Nature.

[31]  M. Kirschner,et al.  Dynamic instability of microtubule growth , 1984, Nature.

[32]  J. Sambrook,et al.  Molecular Cloning: A Laboratory Manual , 2001 .

[33]  G. Borisy,et al.  The pericentriolar material in Chinese hamster ovary cells nucleates microtubule formation , 1977, The Journal of cell biology.

[34]  J. Huxley,et al.  The Cell in Development and Heredity , 1925, Nature.