%0 Journal Article %A Bossart, Walter %A Egger, Denise %A Rasser, Yvonne %A Bienz, Kurt %T Electron Microscopical Observations of the Structure of the Virus of Viral Haemorrhagic Septicaemia (VHS) of Rainbow Trout (Salmo gairdneri) %D 1982 %J Journal of General Virology, %V 63 %N 1 %P 131-140 %@ 1465-2099 %R https://doi.org/10.1099/0022-1317-63-1-131 %K poliovirus %K in vitro transcription %K isolated nuclei %K RNA synthesis inhibition %I Microbiology Society, %X SUMMARY Nuclei isolated from uninfected HEp-2 cells synthesized RNA for 60 to 90 min. The individual RNA polymerase activities were determined by α-amanitin differential inhibition and the RNA products characterized byelectron microscope (EM) autoradiography and sucrose gradient centrifugation. In nucleiprepared from poliovirus-infected cells, the capacity tosynthesize RNA in vitro decreased with time after infection. RNA polymerase II activity (hnRNA synthesis) was preferentially inhibited more than was the polymerase I activity (rRNA synthesis). Poliovirus-infected cytoplasm (S-30) inhibited in vitro RNA synthesis in uninfected nuclei by selectively affecting the polymerase II activity. Selective inhibition of hnRNA synthesis by the crude extracts could be monitored by EM autoradiography directly. Determinations of individual RNA polymerase activities by differential α-amanitin inhibition were done only after treatment of the infected cytoplasm with micrococcal nuclease to abolish virus RNA replication. Selective inhibition of hnRNA synthesis depended on preincubation of the nuclei together with the infected cytoplasm, indicating that inhibitory substances from the infected cytoplasm entered the nuclei. Isolated nuclei therefore provide a useful system for studying the nature ofthe inhibitor(s) and of host RNA synthesis inhibition by picornaviruses. %U https://www.microbiologyresearch.org/content/journal/jgv/10.1099/0022-1317-63-1-131