ASSOCIATION OF P34(CDC2) KINASE AND MAP KINASE WITH MICROTUBULES DURING THE MEIOTIC MATURATION OF XENOPUS OOCYTES

p34(cdc2) protein is found in prophase, metaphase and activated Xenopu s oocytes at a similar level whereas its kinase activity oscillates wi thin meiosis. Using an anti-PSTAIRE antibody that recognizes Xenopos p 34(cdc2), it was demonstrated that the major part of p34(cdc2) was ass ociated with microtubules isolated in vitrofrom Xenopos oocytes. Conve rsely, tubulin was recovered in association with p34(cdc2) in p13-Seph arose pellets. The abundance of the fraction of p34(cdc2) which was as sociated with microtubules did not oscillate during the meiotic matura tion and the activation process. By contrast, the histone H1 kinase ac tivity of p34(cdc2) estimated in microtubular oocyte pellets was much higher in metaphase than in prophase oocytes. Cyclin B, which is assoc iated in vivo with p34(cdc2) in prophase and metaphase oocytes, was al so present in the microtubular fractions. However, cyclin was not nece ssary for the binding of p34(cdc2) to microtubules since p34(cdc2) fro m activated eggs, where cyclin was missing, still copurified with micr otubules. Purified MAP2, but not tubulin, was able to bind to p34(cdc2 ), demonstrating that the association between p34(cdc2) and microtubul es 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 purifie d from Xenopus oocytes were able to phosphorylate in vitro rat brain M AP2. However both protein kinases phosphorylated different domains of MAP2, suggesting that they might regulate microtubules in different wa ys.