Polo kinase and Asp are needed to promote the mitotic organizing activity of centrosomes

Abstract

Interfering with the activity of polo-like kinases can lead to the formation of monopolar spindles1,2,3,4. Polo-like kinases also regulate mitotic entry, activation of the anaphase-promoting complex and the necessary preconditions for cytokinesis5,6. Similarities between the phenotypes of the Drosophila mutants asp and polo point towards a common role in spindle pole function. The abnormal spindles of asp mutants are bipolar but have disorganized broad poles at which γ-tubulin has an abnormal distribution7. Moreover, the synergism or of polo1 aspE3 double mutants indicates a possible involvement of these genes in a common process8. Asp is a microtubule-associated protein of relative molecular mass 220,000 (Mr 220K) found at the face of the centrosome that contacts spindle microtubules. In partially purified centrosomes, it is required with γ-tubulin to organize microtubule asters7. Here, we show that Asp is the previously identified Mr 220K substrate of Polo kinase9. Polo phosphorylates Asp in vitro, converting it into an MPM2 epitope. Polo and Asp proteins immunoprecipitate together and exist as part of a 25–38S complex. Extracts of polo-derived embryos are unable to restore the ability of salt-stripped centrosomes to nucleate microtubule asters. This can be rescued by addition of phosphorylated Asp or active Polo kinase.

Cite this article

do Carmo Avides, M., Tavares, A. & Glover, D. Polo kinase and Asp are needed to promote the mitotic organizing activity of centrosomes. Nat Cell Biol 3, 421–424 (2001). https://doi.org/10.1038/35070110

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