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 tyrosinated form of the protein, blocks the cell cycle in developing oocytes. Here, we have investigated the mechanism involved in the mAb effect. Both developing 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 antibody effect was independent of the presence or absence of polymerized microtubules and was mimicked by injected synthetic peptides corresponding to the tyrosinated (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 involved in specific regulation of cyclin B synthesis in developing oocytes.