STKE: Checkpoint Control at the Golgi

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Science  11 Mar 2005:
Vol. 307, Issue 5715, pp. 1537b
DOI: 10.1126/science.307.5715.1537b

Organelles, such as the Golgi apparatus, must disperse equally during cell division. However, it is not clear whether checkpoints exist for sensing organelle integrity during mitosis. Preisinger et al. examined the link between Golgi morphology and cell cycle control. GRASP65, a structural component of Golgi membranes, is required for Golgi fragmentation before entry into mitosis. The C terminus of GRASP65 is phosphorylated primarily by the mitotic kinase Cdk1-cyclin B and to a lesser extent by polo-like kinase 1 (Plk1), an enzyme required for normal mitotic spindle function. Phosphorylation of Golgi-associated GRASP65 on the Cdk1-cyclin B consensus sites correlated with entry into mitosis. Plk1 was detected in a complex with GRASP65 and the Golgi protein GM130 in mitotic cell extracts, but only if GRASP65 was phosphorylated by Cdk1-cyclin B, suggesting that the mitotic kinase creates docking sites on GRASP65 for Plk1. When cells were depleted of Plk1, mitotic fragmentation of the Golgi into clusters was decreased. Overexpression of the GRASP65 C terminus delayed entry into mitosis. However, cells expressing a GRASP65 C terminus harboring a mutant that cannot bind Plk passed through mitosis normally. Passage through mitosis may thus depend largely on the influence of GRASP65-associated Plk1 on the Golgi, where it may help to ensure appropriate Golgi fragmentation and thereby equal partitioning into daughter cells. — LDC

EMBO J. 24, 753 (2005).

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