Cell cycle regulation of p34kinase activity in Physarum polycephalum

The regulation of the mitotic histone HI kinase activity has been analyzed during the naturally synchronous cell cycle of Physanun polycephalum plasmodia. The universal binding property of the pl3 Schizosaccharomyces pombe gene product was used to precipitate and assay the cdc2 histone HI kinase activity. The kinase activity peaks at the beginning of metaphase and its decline, which requires protein synthesis, appears to be an early event during the metaphase process. Microtubular poisons, temperature shifts and DNA synthesis inhibitors were used to perturb cell cycle regulatory pathways and characterize their effects on cdc2 kinase activation. Our results suggest that the full activation of the mitotic kinase requires at least two successive triggering signals involving microtubular components and DNA synthesis.