Evidence for a role of the alpha-tubulin C terminus in the regulation of cyclin B synthesis in developing oocytes

Microinjected mAb YL1/2, an alpha -tubulin antibody specific for the tyrosi nated form of the protein, blocks the cell cycle in developing oocytes, Her e, we have investigated the mechanism involved in the mAb effect, Both deve loping starfish and Xenopus oocytes were injected with two different alpha -tubulin C terminus antibodies. The injected antibodies blocked cell entry into mitosis through specific inhibition of cyclin B synthesis. The antibod y effect was independent of the presence or absence of polymerized microtub ules and was mimicked by injected synthetic peptides corresponding to the t yrosinated alpha -tubulin C terminus, whereas peptides lacking the terminal tyrosine were ineffective, These results indicate that tyrosinated alpha - tubulin, or another protein sharing the same C-terminal epitope, is involve d in specific regulation of cyclin B synthesis in developing oocytes.