Detection of polycistronic transcripts in Newcastle disease virus infected cells and identification of their sequence content.

The synthesis of six to seven polycistronic transcripts of Newcastle disease virus (NDV) in BHK cells was detected by Northern hybridization using cDNA clones generated by reverse transcription of five NDV mRNAs. Within the molecular weight range resolved by the gel electrophoresis system employed, four of the transcripts were suggested to be distronic, containing sequences of two genes, NP-P, P-M, M-F0 and F0-HN, respectively. In addition, tricistronic molecules of M-F0-HN and possibly of NP-P-M as well as P-M-F0 appeared to develop, although they were very low in amount. These data suggest a gene order of NP-P-M-F0-HN on the NDV genome. The polycistronic as well as monocistronic transcripts were generated with an almost constant proportion in amount throughout the virus replication. Further, at least several of them were also generated under the conditions where only the primary transcription was allowed by inhibiting de novo protein synthesis. Therefore, it appears likely that there is no distinct temporal control in NDV genome expression.