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The centrosomal protein C-Nap1 is required for cell cycle-regulated centrosome cohesion.

Mayor T, Stierhof YD, Tanaka K, Fry AM, Nigg EA - J. Cell Biol. (2000)

Bottom Line: Antibodies raised against different domains of C-Nap1 prove that this protein dissociates from spindle poles during mitosis, but reaccumulates at centrosomes at the end of cell division.Use of the same antibodies in immunoelectron microscopy shows that C-Nap1 is confined to the proximal end domains of centrioles, indicating that a putative linker structure must contain additional proteins.We conclude that C-Nap1 is a key component of a dynamic, cell cycle-regulated structure that mediates centriole-centriole cohesion.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology, Sciences II, University of Geneva, CH-1211 Geneva, Switzerland.

ABSTRACT
Duplicating centrosomes are paired during interphase, but are separated at the onset of mitosis. Although the mechanisms controlling centrosome cohesion and separation are important for centrosome function throughout the cell cycle, they remain poorly understood. Recently, we have proposed that C-Nap1, a novel centrosomal protein, is part of a structure linking parental centrioles in a cell cycle-regulated manner. To test this model, we have performed a detailed structure-function analysis on C-Nap1. We demonstrate that antibody-mediated interference with C-Nap1 function causes centrosome splitting, regardless of the cell cycle phase. Splitting occurs between parental centrioles and is not dependent on the presence of an intact microtubule or microfilament network. Centrosome splitting can also be induced by overexpression of truncated C-Nap1 mutants, but not full-length protein. Antibodies raised against different domains of C-Nap1 prove that this protein dissociates from spindle poles during mitosis, but reaccumulates at centrosomes at the end of cell division. Use of the same antibodies in immunoelectron microscopy shows that C-Nap1 is confined to the proximal end domains of centrioles, indicating that a putative linker structure must contain additional proteins. We conclude that C-Nap1 is a key component of a dynamic, cell cycle-regulated structure that mediates centriole-centriole cohesion.

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Cell cycle–regulated centrosome association of C-Nap1. This schematic model summarizes current information about the function and precise subcellular localization of C-Nap1, as inferred from the results presented in this study (see text for details).
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Figure 7: Cell cycle–regulated centrosome association of C-Nap1. This schematic model summarizes current information about the function and precise subcellular localization of C-Nap1, as inferred from the results presented in this study (see text for details).

Mentions: Taken together, our immunocytochemical analyses at both the light- and electron-microscopic levels indicate that the entire C-Nap1 protein is located close to the tips of both parental centrioles. However, although the NH2 terminus could be detected at a greater distance from the tips than the COOH terminus, no C-Nap1 protein could be seen spanning the entire region between the two centrioles. Thus, we conclude that any cohesive structure extending from one centriole to the other is almost certain to contain additional, as yet unidentified proteins (Fig. 7). Furthermore, the association between parental centriole and procentriole is unlikely to be mediated by C-Nap1, and finally, C-Nap1 is almost completely absent from mitotic spindle poles.


The centrosomal protein C-Nap1 is required for cell cycle-regulated centrosome cohesion.

Mayor T, Stierhof YD, Tanaka K, Fry AM, Nigg EA - J. Cell Biol. (2000)

Cell cycle–regulated centrosome association of C-Nap1. This schematic model summarizes current information about the function and precise subcellular localization of C-Nap1, as inferred from the results presented in this study (see text for details).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2169446&req=5

Figure 7: Cell cycle–regulated centrosome association of C-Nap1. This schematic model summarizes current information about the function and precise subcellular localization of C-Nap1, as inferred from the results presented in this study (see text for details).
Mentions: Taken together, our immunocytochemical analyses at both the light- and electron-microscopic levels indicate that the entire C-Nap1 protein is located close to the tips of both parental centrioles. However, although the NH2 terminus could be detected at a greater distance from the tips than the COOH terminus, no C-Nap1 protein could be seen spanning the entire region between the two centrioles. Thus, we conclude that any cohesive structure extending from one centriole to the other is almost certain to contain additional, as yet unidentified proteins (Fig. 7). Furthermore, the association between parental centriole and procentriole is unlikely to be mediated by C-Nap1, and finally, C-Nap1 is almost completely absent from mitotic spindle poles.

Bottom Line: Antibodies raised against different domains of C-Nap1 prove that this protein dissociates from spindle poles during mitosis, but reaccumulates at centrosomes at the end of cell division.Use of the same antibodies in immunoelectron microscopy shows that C-Nap1 is confined to the proximal end domains of centrioles, indicating that a putative linker structure must contain additional proteins.We conclude that C-Nap1 is a key component of a dynamic, cell cycle-regulated structure that mediates centriole-centriole cohesion.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology, Sciences II, University of Geneva, CH-1211 Geneva, Switzerland.

ABSTRACT
Duplicating centrosomes are paired during interphase, but are separated at the onset of mitosis. Although the mechanisms controlling centrosome cohesion and separation are important for centrosome function throughout the cell cycle, they remain poorly understood. Recently, we have proposed that C-Nap1, a novel centrosomal protein, is part of a structure linking parental centrioles in a cell cycle-regulated manner. To test this model, we have performed a detailed structure-function analysis on C-Nap1. We demonstrate that antibody-mediated interference with C-Nap1 function causes centrosome splitting, regardless of the cell cycle phase. Splitting occurs between parental centrioles and is not dependent on the presence of an intact microtubule or microfilament network. Centrosome splitting can also be induced by overexpression of truncated C-Nap1 mutants, but not full-length protein. Antibodies raised against different domains of C-Nap1 prove that this protein dissociates from spindle poles during mitosis, but reaccumulates at centrosomes at the end of cell division. Use of the same antibodies in immunoelectron microscopy shows that C-Nap1 is confined to the proximal end domains of centrioles, indicating that a putative linker structure must contain additional proteins. We conclude that C-Nap1 is a key component of a dynamic, cell cycle-regulated structure that mediates centriole-centriole cohesion.

Show MeSH
Related in: MedlinePlus