Abstract
DNA-dependent RNA synthesis in an isolated rat liver nuclei
in
vitro
assay was inhibited by 41 and 61% in the presence of α-amanitin, the inhibitor specific for RNA polymerase II and phaseolinone, a new mycotoxin, respectively. This inhibition reached 97% when these two inhibitors were present together. The RNA polymerase activity present in a nucleolar fraction was inhibited by greater than 80% in presence of phaseolinone, but phaseolinone and DNA showed no interaction as judged from CD spectra or density gradient centrifugation of toxin-treated DNA. This evidence suggested that phaseolinone inhibited RNA polymerase activity other than RNA polymerase II.