Characteristics of virus-specific RNA in avian sarcoma virus-transformed BHK-21 cells and revertants

Abstract

Several characteristics of viral RNA transcripts in a clone of avian sarcoma virus (ASV)-transformed baby hamster kidney cells have been studied and compared with the characteristics of viral RNA in clones of cells reverted to a normal phenotype. As reported previously [Deng, C. T., Boettiger, D., Macpherson, I., and Varmus, H. E. (1974). Virology 62, 512–5211, both transformed and reverted cells contain one DNA copy of the viral genome per cell, but the concentration of viral RNA is 2- to 85-fold higher in the transformed cells than in the reverted cells. We now show that ASV RNA from cells of both types contains poly(A) sequences, is threefold more abundant in the cytoplasm than in the nuclei, and is associated with polyribosomes. In the transformed clone, whole cell RNA contains 35 and 24 S species of ASV RNA, whereas only 24 S ASV RNA is detected in the cytoplasm; in the reverted clones, the 24 S species of ASV RNA is present in whole cell RNA and in poly(A)-containing cytoplasmic RNA, but the amounts of viral RNA in these cells are too low to determine unambiguously whether they also contain 35 S ASV RNA. Nucleotide sequences specific for the transforming gene of ASV are present in the RNA, including the polyribosome-associated RNA, of both transformed and reverted cell types, but the concentration of these sequences is reduced in the reverted cell and its polyribosomes in proportion to the overall reduction in viral RNA in reverted cells. Thus, a reduction in the concentration of viral RNA may be the only change in viral gene expression in the reverted cells.