Association of p34(cdc2) kinase and MAP kinase with microtubules during the meiotic maturation of Xenopus oocytes

Abstract

p34(cdc2) protein is found in prophase, metaphase and activated Xenopus oocytes at a similar level whereas its kinase activity oscillates within meiosis. Using an anti-PSTAIRE antibody that recognizes Xenopus p34(cdc2), it was demonstrated that the major part of p34(cdc2) was associated with microtubules isolated in vitro from Xenopus oocytes. Conversely, tubulin was recovered in association with p34(cdc2) in p13-Sepharose pellets. The abundance of the fraction of p34(cdc2) which was associated with microtubules did not oscillate during the meiotic maturation and the activation process. By contrast, the histone H1 kinase activity of p34(cdc2) estimated in microtubular oocyte pellets was much higher in metaphase than in prophase oocytes. Cyclin B, which is associated in vivo with p34(cdc2) in prophase and metaphase oocytes,was also present in the microtubular fractions. However. cyclin was not necessary for the binding of p34(cdc2) to microtubules since p34(cdc2) from activated eggs, where cyclin was missing, still copurified with microtubules. Purified MAP2, but not tubulin, was able to bind to p34(cdc2), demonstrating that the association between p34(cdc2) and microtubules was mediated by microtubule-associated proteins. During the meiotic maturation of Xenopus oocytes, several protein kinases were activated, among them MAP kinase. MAP kinase also associated with microtubules. It was demonstrated that both p34(cdc2) kinase and MAP kinase purified from Xenopus oocytes were able to phosphorylate in vitro rat brain MAP2. However both protein kinases phosphorylated different domains of MAP2, suggesting that they might regulate microtubules in different ways.