Newcastle disease virus-specific RNA: an analysis of 24 S and 35 S RNA transcripts.

The denaturation of Newcastle disease virus-specific 24 S and 35 S RNA by heat or formamide treatment led to a shift of a large part (60--80%) of RNA into the 18 S zone. The remaining 20--40% could not be dissociated further by repeated denaturation or by centrifugation in dimethyl sulfoxide-sucrose gradient. Hybridization-competition analysis revealed that the majority (approximately 75%) of the non-dissociable 35 S RNA and almost all the material present in the non-dissociable 24 S RNA were represented by nucleotide sequences homologous to 18 S RNA. On the other hand, the non-dissociable 35 S RNA lacked some of the sequences present in 18 S RNA, since no more than 45% of the labelled 18 S RNA could be displaced from the hybrid by an excess of unlabelled non-dissociable 35 S RNA. The possible origin of 24 S and 35 S RNA is discussed.