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Golgi partitioning controls mitotic entry through Aurora-A kinase.

Persico A, Cervigni RI, Barretta ML, Corda D, Colanzi A - Mol. Biol. Cell (2010)

Bottom Line: We show that a block of Golgi partitioning impairs centrosome recruitment and activation of Aurora-A, which results in the G2 block of cell cycle progression.Overexpression of Aurora-A overrides this cell cycle block, indicating that Aurora-A is a major effector of the Golgi checkpoint.Our findings provide the basis for further understanding of the signaling pathways that coordinate organelle inheritance and cell duplication.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, 66030 Santa Maria Imbaro, Chieti, Italy.

ABSTRACT
At the onset of mitosis, the Golgi complex undergoes a multistep fragmentation process that is required for its correct partitioning into the daughter cells. Inhibition of this Golgi fragmentation results in cell cycle arrest at the G2 stage, suggesting that correct inheritance of the Golgi complex is monitored by a "Golgi mitotic checkpoint." However, the molecular basis of this G2 block is not known. Here, we show that the G2-specific Golgi fragmentation stage is concomitant with centrosome recruitment and activation of the mitotic kinase Aurora-A, an essential regulator for entry into mitosis. We show that a block of Golgi partitioning impairs centrosome recruitment and activation of Aurora-A, which results in the G2 block of cell cycle progression. Overexpression of Aurora-A overrides this cell cycle block, indicating that Aurora-A is a major effector of the Golgi checkpoint. Our findings provide the basis for further understanding of the signaling pathways that coordinate organelle inheritance and cell duplication.

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Morphology of Golgi membranes and centrosomes through the cell cycle in HeLa cells. (A) Representative images of cells grown on coverslips and processed for immunofluorescence under confocal microscopy 12 h after the S phase block release. The cells were labeled with antibodies against giantin (red; Golgi complex) and γ-tubulin (green) to mark the centrosomes (arrows) at the indicated cell cycle stages. Images were acquired at maximal resolution, with fixed imaging conditions. Bars, 5 μm. (B) Schematic representation of the mechanisms governing activation of cycB-Cdk1 at the centrosome during G2. See text for details.
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Figure 2: Morphology of Golgi membranes and centrosomes through the cell cycle in HeLa cells. (A) Representative images of cells grown on coverslips and processed for immunofluorescence under confocal microscopy 12 h after the S phase block release. The cells were labeled with antibodies against giantin (red; Golgi complex) and γ-tubulin (green) to mark the centrosomes (arrows) at the indicated cell cycle stages. Images were acquired at maximal resolution, with fixed imaging conditions. Bars, 5 μm. (B) Schematic representation of the mechanisms governing activation of cycB-Cdk1 at the centrosome during G2. See text for details.

Mentions: Because the inhibition of the severing of the Golgi ribbon induces a cell cycle block in G2 (Sutterlin et al., 2002; Hidalgo Carcedo et al., 2004), this must affect the signaling processes that govern the activation of the cyclin B–Cdk1 complex (cycB-Cdk1), the master regulator of entry into mitosis (Nigg, 2001). The first activation of cycB-Cdk1 occurs at the centrosome during G2, in coincidence with centrosome separation, and before the hallmarks of mitotic entry become morphologically discernible, such as chromosome condensation and assembly of mitotic spindles (Hirota et al., 2003; Jackman et al., 2003). In HeLa cells, the S phase Golgi ribbon (identified using an anti-giantin antibody; Figure 2A, S phase) was located in close association with the duplicated centrosomes (identified using an anti-γ-tubulin antibody; Figure 2A). During early G2 phase (identified using an anti-phospho-H3 antibody; Figure 6A), the centrosomes began to separate (Figure 2A; G2 phase, arrows), and this coincided with the first evident severing of the Golgi ribbon (i.e., the Golgi fragmentation step essential for mitotic entrance). The Golgi complex thus appeared to be divided into two main groups of isolated membranes, each of which maintained close association with a separated centrosome (Figure 2A, G2 phase). The centrosomes reached their final positions in prophase (Figure 2A, prophase), in preparation for the formation of the mitotic spindles (Nigg, 2001).


Golgi partitioning controls mitotic entry through Aurora-A kinase.

Persico A, Cervigni RI, Barretta ML, Corda D, Colanzi A - Mol. Biol. Cell (2010)

Morphology of Golgi membranes and centrosomes through the cell cycle in HeLa cells. (A) Representative images of cells grown on coverslips and processed for immunofluorescence under confocal microscopy 12 h after the S phase block release. The cells were labeled with antibodies against giantin (red; Golgi complex) and γ-tubulin (green) to mark the centrosomes (arrows) at the indicated cell cycle stages. Images were acquired at maximal resolution, with fixed imaging conditions. Bars, 5 μm. (B) Schematic representation of the mechanisms governing activation of cycB-Cdk1 at the centrosome during G2. See text for details.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
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Figure 2: Morphology of Golgi membranes and centrosomes through the cell cycle in HeLa cells. (A) Representative images of cells grown on coverslips and processed for immunofluorescence under confocal microscopy 12 h after the S phase block release. The cells were labeled with antibodies against giantin (red; Golgi complex) and γ-tubulin (green) to mark the centrosomes (arrows) at the indicated cell cycle stages. Images were acquired at maximal resolution, with fixed imaging conditions. Bars, 5 μm. (B) Schematic representation of the mechanisms governing activation of cycB-Cdk1 at the centrosome during G2. See text for details.
Mentions: Because the inhibition of the severing of the Golgi ribbon induces a cell cycle block in G2 (Sutterlin et al., 2002; Hidalgo Carcedo et al., 2004), this must affect the signaling processes that govern the activation of the cyclin B–Cdk1 complex (cycB-Cdk1), the master regulator of entry into mitosis (Nigg, 2001). The first activation of cycB-Cdk1 occurs at the centrosome during G2, in coincidence with centrosome separation, and before the hallmarks of mitotic entry become morphologically discernible, such as chromosome condensation and assembly of mitotic spindles (Hirota et al., 2003; Jackman et al., 2003). In HeLa cells, the S phase Golgi ribbon (identified using an anti-giantin antibody; Figure 2A, S phase) was located in close association with the duplicated centrosomes (identified using an anti-γ-tubulin antibody; Figure 2A). During early G2 phase (identified using an anti-phospho-H3 antibody; Figure 6A), the centrosomes began to separate (Figure 2A; G2 phase, arrows), and this coincided with the first evident severing of the Golgi ribbon (i.e., the Golgi fragmentation step essential for mitotic entrance). The Golgi complex thus appeared to be divided into two main groups of isolated membranes, each of which maintained close association with a separated centrosome (Figure 2A, G2 phase). The centrosomes reached their final positions in prophase (Figure 2A, prophase), in preparation for the formation of the mitotic spindles (Nigg, 2001).

Bottom Line: We show that a block of Golgi partitioning impairs centrosome recruitment and activation of Aurora-A, which results in the G2 block of cell cycle progression.Overexpression of Aurora-A overrides this cell cycle block, indicating that Aurora-A is a major effector of the Golgi checkpoint.Our findings provide the basis for further understanding of the signaling pathways that coordinate organelle inheritance and cell duplication.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, 66030 Santa Maria Imbaro, Chieti, Italy.

ABSTRACT
At the onset of mitosis, the Golgi complex undergoes a multistep fragmentation process that is required for its correct partitioning into the daughter cells. Inhibition of this Golgi fragmentation results in cell cycle arrest at the G2 stage, suggesting that correct inheritance of the Golgi complex is monitored by a "Golgi mitotic checkpoint." However, the molecular basis of this G2 block is not known. Here, we show that the G2-specific Golgi fragmentation stage is concomitant with centrosome recruitment and activation of the mitotic kinase Aurora-A, an essential regulator for entry into mitosis. We show that a block of Golgi partitioning impairs centrosome recruitment and activation of Aurora-A, which results in the G2 block of cell cycle progression. Overexpression of Aurora-A overrides this cell cycle block, indicating that Aurora-A is a major effector of the Golgi checkpoint. Our findings provide the basis for further understanding of the signaling pathways that coordinate organelle inheritance and cell duplication.

Show MeSH
Related in: MedlinePlus