Intracellular distribution and sedimentation properties of virus-specific RNA in two clones of BHK cells transformed by polyoma virus.

The virus-specific RNA in two independently derived clones of polyoma virus-transformed hamster cells was studied by hybridizing labeled RNA, with excess purified polyoma DNA, immoblized on filters. In one clone (PyBHK1), less than 25% of the total labeled virus-specific RNA was found in the cytoplasm, irrespective of the labeling time. In the other clone (PyBHK2), it was estimated that 39% of the total virus-specific RNA was present inthe cytoplasm after labeling for 3 h. Both the proportion of radioactive label incorporated into virus-specific RNA and the sedimentation pattern of total virus-specific RNA differed markedly between PyBHK and PyBHK2. Most of the virus-specific RNA of PyBHK1 sedimented in the range 25S-35S, whereas a prominent 18S component was present in PyBHK2. Most of the cytoplasmic virus-specific RNA in both clones sedimented at 18S-19S. The sedimentation patterns of virus-specific RNA from whole cells and from washed nuclei of PyBHK1 were closely similar: it was estimated from sedimentation analysis in dimethyl sulfoxide that the molecular weight of 50% of this RNA was within the range 1.1 X10(6) to 2.9 X 10(6). These results, demonstrating the accumulation of virus-specific RNA within the nucleus in at least one virus-transformed cell line, indicate that the large virus-specific RNA previously described in the nuclei of transformed cells may not have represented precursors of virus-specific mRNA.