The Polyoma virus-specific RNA (PyRNA) synthesized in a line of Polyoma-transformed hamster cells, was analyzed and compared with the viral-specific RNA synthesized "late" in productively infected mouse cells. The PyRNA from the transformed cells sedimented heterogeneously on sucrose gradients, including appreciable amounts of PyRNA in the > 40-S region. The overall sedimentation profile resembled that of "late" PyRNA synthesized in mouse cells. Competition hybridization experiments, however, revealed that the bulk of the PyRNA sequences in the transformed cells were different from "late" PyRNA sequences. The use of DNA–DNA hybridization experiments (with Polyoma DNA of high specific radioactivity) enabled an estimate to be made of the average number of viral genomes per transformed cell. No more than two, and possibly less than one, complete genomes were found. These studies support the hypothesis that this line of Polyoma transformed cells contains an incomplete genome, possibly only comprising "early" genes (hence the inability to rescue infectious virus), and that the viral RNA transcribed is covalently linked to host cell RNA moieties.
An Assessment by Competition Hybridization of the Sequence Homology between the RNAs of the Seven Serotypes of FMDV
