Leptomycin B, which had been discovered as a cell cycle inhibitor active against fission yeast, was found to inhibit nuclear export of proteins. On the other hand, trichostatin A and trapoxin specifically inhibit histone deacetylation that regulates transcription. A microtubule-deacetylating enzyme was identified by the analysis of proteins acetylated by trichostatin A but not trapoxin. Studies on the molecular mode of action of these inhibitors have revealed the important roles of the target molecules in cellular functions and contribute to the current progress in understanding the mechanisms of gene expression and cell division.