Regulation of thymidine kinase synthesis during the cell cycle of Physarum polycephalum: the effects of two microtubule inhibitors.

Methyl benzimidazole carbamate and griseofulvin are two microtubule inhibitors which perturb plasmodial mitosis in Physarum polycephalum. These two compounds perturb not only the mitotic process leading to abortive mitosis but delay the onset of mitosis. Both drugs delayed the onset of thymidine kinase synthesis (EC 2.7.1.21, ATP: thymidine 5'phosphotransferase) which occurred concomitantly with mitosis. Thus, thymidine kinase synthesis, a cell cycle event which is not thought to have any relationship with the microtubular system, was perturbed in the same way as mitosis in the presence of two chemically unrelated microtubule inhibitors. It is suggested that the microtubular system is an essential part of a regulatory pathway of the cell cycle which plays a role in at least two events of the cell cycle: the onset of thymidine kinase synthesis, and the onset of mitosis.