Specific Phosphorylation of Nucleophosmin on Thr199 by Cyclin-dependent Kinase 2-Cyclin E and Its Role in Centrosome Duplication

Yukari Tokuyama, Henning F. Horn, Kenji Kawamura, Pheruza Tarapore, Kenji Fukasawa

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The kinase activity of cyclin-dependent kinase 2 (CDK2)-cyclin E is required for centrosomes to initiate duplication. We have recently found that nucleophosmin (NPM/B23), a phosphoprotein primarily found in nucleolus, associates with unduplicated centrosomes and is a direct substrate of CDK2-cyclin E in centrosome duplication. Upon phosphorylation by CDK2-cyclin E, NPM/B23 dissociates from centrosomes, which is a pre-requisite step for centrosomes to initiate duplication. Here, we identified that threonine 199 (Thr199) of NPM/B23 is the major phosphorylation target site of CDK2-cyclin E in vitro, and the same site is phosphorylated in vivo. NPM/T199A, a nonphosphorylatable NPM/B23 substitution mutant (Thr199 → Ala) acts as dominant negative when expressed in cells, resulting in specific inhibition of centrosome duplication. As expected, NPM/T199A remains associated with the centrosomes. These observations provide direct evidence that the CDK2-cyclin E-mediated phosphorylation on Thr199 determines association and dissociation of NPM/B23 to the centrosomes, which is a critical control for the centrosome to initiate duplication.

Original languageEnglish
Pages (from-to)21529-21537
Number of pages9
JournalJournal of Biological Chemistry
Issue number24
Publication statusPublished - 15 Jun 2001


ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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