Initial activation of cyclin-B1-cdc2 kinase requires phosphorylation of cyclin B1

• Published in: EMBO reports Vol. 3; no. 6; pp. 551 - 556
• Main Authors: Peter, Marion, Le Peuch, Christian, Labbé, Jean-Claude, Meyer, April N, Donoghue, Daniel J, Dorée, Marcel
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.06.2002; Oxford University Press
• Subjects: Animals; CDC2 Protein Kinase - metabolism; cdc25 Phosphatases - metabolism; Cell Cycle Proteins - metabolism; Cyclin B - metabolism; Cyclin B1; Enzyme Activation; Maturation-Promoting Factor - metabolism; Oocytes; Phosphorylation; Protein Serine-Threonine Kinases - metabolism; Scientific Reports; Xenopus; Xenopus Proteins
• ISSN: 1469-221X; 1469-3178
• DOI: 10.1093/embo-reports/kvf111

At the G2/M transition of the cell cycle, the cdc25c phosphatase dephosphorylates inhibitory residues of cdc2, and cyclin‐B–cdc2 kinase (MPF) is activated. Phosphorylation of cyclin B1 induces its nuclear accumulation, and, since cdc25c is also believed to accumulate and activate shortly before G2/M in the nucleus, it has been proposed that this induces cyclin‐B1–cdc2 kinase activation. We demonstrate that cyclin B1 phosphorylation has another essential function in vivo: it is required for cdc25c and MPF activation, which does not require nuclear accumulation of cyclin B1, and occurs in the cytoplasm.