New species of rapidly hybridizing RNA in contact-inhibited as well as transformed hamster cell lines.

The rapidly hybridizing RNA sequences transcribed in primary hamster embryo cells and in lines of serially propagated hamster cells were compared by the technique of RNA-DNA hybridization-competition. Such sequences are known to be transcribed from reiterated DNA sites. There were no rapidly hybridizing RNA sequences in primary hamster embryo cells that were not also present in transformed cell lines. However, in reciprocal experiments, unlabeled RNA from primary hamster embryo cells competed with only 62 to 66% of the hybridizable radioactivity present in RNA from transformed lines. In contrast, the rapidly hybridizing RNA sequences detected in untransformed, contact-inhibited cell lines were similar to those present in transformed cells. Thus, primary hamster embryo cells appear to lack rapidly hybridizing RNA sequences that are transcribed in both transformed and untransformed cell lines. Moreover, these results indicate that the acquisition of oncogenicity is not necessarily correlated with the transcription of additional, rapidly hybridizing RNA sequences, since such new sequences may already be present in serially propagated, untransformed cells.