Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 103, Issue 12, Pages 4493-4498Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0600702103
Keywords
aurora kinase inhibitor; mitosis; mitotic spindle
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Funding
- NCI NIH HHS [T32 CA009361, T32 CA 09361] Funding Source: Medline
- NICHD NIH HHS [HD 23696, R01 HD023696] Funding Source: Medline
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Oncoprotein 18/Stathmin (Op18) is a microtubule-destabilizing protein that is inhibited by phosphorylation in response to many types of signals. During mitosis, phosphorylation of Op18 by cdc2 is necessary but not sufficient for Op18 inhibition. The presence of mitotic chromosomes is additionally required and involves phosphorylation of Ser-16 in Xenopus Op18 (and/or Ser-63 in human). Given that Ser-16 is an excellent Aurora A (Aur-A) kinase consensus phosphorylation site and the Aurora kinase inhibitor ZM447439 (ZM) blocks phosphorylation in the activation loop of Aur-A, we asked whether either Aur-A or Aurora B (Aur-B) might regulate Op18. We find that ZM blocks the ability of mitotic chromatin to induce Op18 hyperphosphorylation in Xenopus egg extracts. Depletion of Aur-B, but not Aur-A, blocks hyperphosphorylation of Op18, and chromatin assembled in the absence of Aur-B fails to induce hyperphosphorylation. These results suggest that Aur-B, which concentrates at centromeres of metaphase chromosomes, contributes to localized regulation of Op18 during the process of spindle assembly.
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