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gamma-tubulin functions in mammalian cells.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	gamma-tubulin functions in mammalian cells./
作者:	Shu, Hong-Bing.
面頁冊數:	1 online resource (166 pages)
附註:	Source: Dissertations Abstracts International, Volume: 57-07, Section: B.
Contained By:	Dissertations Abstracts International57-07B.
標題:	Cellular biology. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9605444click for full text (PQDT)
ISBN:	9798208942680

gamma-tubulin functions in mammalian cells.
Shu, Hong-Bing.

gamma-tubulin functions in mammalian cells. - 1 online resource (166 pages)

Source: Dissertations Abstracts International, Volume: 57-07, Section: B.

Thesis (Ph.D.)--Emory University, 1995.

Includes bibliographical references

My goal was to determine the function of γ-tubulin in mammalian cells. α-, β-, and γ-tubulins are highly conserved members of the tubulin gene superfamily. While the more abundant members, α- and β-tubulin, constitute the building blocks of cellular microtubule polymers. γ-tubulin is an extremely low abundance protein localized at the pericentriolar material. Based on genetic and biochemical approaches, it has been hypothesized that γ-tubulin plays a role in nucleation of microtubles. To test this hypothesis, we have experimentally elevated the expression of γ-tubulin in cytoplasmic sites other than the centrosome. From these studies, we can draw several conclusions. First, as expected, overexpression of γ-tubulin causes a dramatic reorganization of the radially arranged normal cellular microtubule architecture. Furthermore, using an in vivo microtubule nucleation assay, we show that overexpressed γ-tubulin forms numerous microtubule nucleation sites outside the centrosome. These results are consistent with the hypothesis that γ-tublin play a role in nucleation of microtubule assembly. Second, in the presence of extracentrosomal microtubules a mitotic checkpoint is abrogated. That is, cells which overexpress γ-tubulin enter multiple rounds of S-phase in the absence of intact mitotic spindles and productive cell divisions. From these results we predict that microtubule/kinetochore interactions are monitored by a mitotic checkpoint and the progression of the cell cycle to the subsequent S phase does not depend on the complete morphogenesis of an intact mitotic spindle in the previous M phase. Third, in a fraction of cells which overexpress γ-tubulin, overexpressed γ-tubulin self-assembles into novel tubular structures with a diameter of ~50 nm which we have named γ-tubules. The γ-tubules do not contain α- and β-tubulin. Our data provide the first evidence that γ-tubulin can assemble into macro-molecular assemblies with distinct morphological, thermodynamic, and pharmacological properties. Based on these structural observation, and biochemical data published elsewhere, we speculate that γ-tubulin may form an annulus at the minus end of microtubule where it may nucleate microtubule assembly.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2023

Mode of access: World Wide Web

ISBN: 9798208942680Subjects--Topical Terms:

3172791
Cellular biology.
Subjects--Index Terms:

microtubuleIndex Terms--Genre/Form:

542853
Electronic books.

gamma-tubulin functions in mammalian cells.
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520 $a My goal was to determine the function of γ-tubulin in mammalian cells. α-, β-, and γ-tubulins are highly conserved members of the tubulin gene superfamily. While the more abundant members, α- and β-tubulin, constitute the building blocks of cellular microtubule polymers. γ-tubulin is an extremely low abundance protein localized at the pericentriolar material. Based on genetic and biochemical approaches, it has been hypothesized that γ-tubulin plays a role in nucleation of microtubles. To test this hypothesis, we have experimentally elevated the expression of γ-tubulin in cytoplasmic sites other than the centrosome. From these studies, we can draw several conclusions. First, as expected, overexpression of γ-tubulin causes a dramatic reorganization of the radially arranged normal cellular microtubule architecture. Furthermore, using an in vivo microtubule nucleation assay, we show that overexpressed γ-tubulin forms numerous microtubule nucleation sites outside the centrosome. These results are consistent with the hypothesis that γ-tublin play a role in nucleation of microtubule assembly. Second, in the presence of extracentrosomal microtubules a mitotic checkpoint is abrogated. That is, cells which overexpress γ-tubulin enter multiple rounds of S-phase in the absence of intact mitotic spindles and productive cell divisions. From these results we predict that microtubule/kinetochore interactions are monitored by a mitotic checkpoint and the progression of the cell cycle to the subsequent S phase does not depend on the complete morphogenesis of an intact mitotic spindle in the previous M phase. Third, in a fraction of cells which overexpress γ-tubulin, overexpressed γ-tubulin self-assembles into novel tubular structures with a diameter of ~50 nm which we have named γ-tubules. The γ-tubules do not contain α- and β-tubulin. Our data provide the first evidence that γ-tubulin can assemble into macro-molecular assemblies with distinct morphological, thermodynamic, and pharmacological properties. Based on these structural observation, and biochemical data published elsewhere, we speculate that γ-tubulin may form an annulus at the minus end of microtubule where it may nucleate microtubule assembly.
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