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  The mechanism regulating the dissociation of the centrosomal protein C-Nap1 from mitotic spindle poles

Mayor, T., Hacker, U., Stierhof, Y. D., & Nigg, E. A. (2002). The mechanism regulating the dissociation of the centrosomal protein C-Nap1 from mitotic spindle poles. Journal of Cell Science, 115(16), 3275-3284.

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Genre: Journal Article
Alternative Title : J. Cell Sci.

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 Creators:
Mayor, T.1, Author              
Hacker, U.1, Author              
Stierhof, Y. D., Author
Nigg, E. A.1, Author              
Affiliations:
1Former Research Groups, Max Planck Institute of Biochemistry, Max Planck Society, ou_1565145              

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Free keywords: C-Nap1; Nek2; centrosome; mitotic spindle; phosphorylation
 Abstract: The centrosomal protein C-Nap1 is thought to play an important role in centrosome cohesion during interphase of the cell cycle. At the onset of mitosis, when centrosomes separate for bipolar spindle formation, C-Nap1 dissociates from centrosomes. Here we report the results of experiments aimed at determining whether the dissociation of C-Nap1 from mitotic centrosomes is triggered by proteolysis or phosphorylation. Specifically, we analyzed both the cell cycle regulation of endogenous C-Nap1 and the fate of exogenously expressed full-length C-Nap1. Western blot analyses suggested a reduction in the endogenous C-Nap1 level during M phase, but studies using proteasome inhibitors and destruction assays performed in Xenopus extracts argue against ubiquitin-dependent degradation of C-Nap1. Instead, our data indicate that the mitotic C-Nap1 signal is reduced as a consequence of M-phase-specific phosphorylation. Overexpression of full-length C-Nap1 in human U2OS cells caused the formation of large structures that embedded the centrosome and impaired its microtubule nucleation activity. Remarkably, however, these centrosome-associated structures did not interfere with cell division. Instead, centrosomes were found to separate from these structures at the onset of mitosis, indicating that a localized and cell-cycle-regulated activity can dissociate C-Nap1 from centrosomes. A prime candidate for this activity is the centrosomal protein kinase Nek2, as the formation of large C-Nap1 structures was substantially reduced upon co-expression of active Nek2. We conclude that the dissociation of C-Nap1 from mitotic centrosomes is regulated by localized phosphorylation rather than generalized proteolysis.

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Language(s): eng - English
 Dates: 2002-08-15
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: eDoc: 41759
ISI: 000177825800006
 Degree: -

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Title: Journal of Cell Science
  Alternative Title : J. Cell Sci.
Source Genre: Journal
 Creator(s):
Affiliations:
Publ. Info: -
Pages: - Volume / Issue: 115 (16) Sequence Number: - Start / End Page: 3275 - 3284 Identifier: ISSN: 0021-9533