ABSTRACT
Uninfected and Rous sarcoma virus (RSV)-transformed chick embryo fibroblasts (CEF) were exposed to various concentrations of alpha-amanitin for different lengths of time. At a concentration of 4 micrograms alpha-amanitin/ml, RSV-transformed cells were shown to maintain a normal rate of transcription of all classes of RNA, whereas in uninfected cells transcription was reduced to a very low level. These observations cannot be accounted for by a difference in the penetration rate of alpha-amanitin through the plasma membrane. Investigation of the ultrastructure showed that the degree of nucleolar fragmentation induced by alpha-amanitin was comparable in both types of cells. Persistence of transcription with concomitant nucleolar fragmentation in alpha-amanitin-treated RSV-transformed CEF is not in accord with the hypothesis that nucleolar integrity is required for preribosomal RNA transcription.
