In this paper, we demonstrate that in Physarum polycephalum, a naturally synchronized slime mold, histone deacetylase (HDAC) inhibitor Trichostatin A (TSA), arrestes the cell cycle at the checkpoints of S/G2, G2/M and mitosis exit, and influences the transcription of two ras genes Ppras1 and Pprap1, as well as the Ras protein level. Antibody neu-tralization experiment using anti-Ras antibody treatment showed that Ras protein played an important role in cell cycle checkpoint control through regulation of the level of Cyclin B1, suggesting that Ras protein might be a key factor for histone acetylation-mediated cell cycle regulation in P. polycephalum.
