[Transcription of influenza virus genome. Location and dependence on the nuclear primer function]

The synthesis of the complete and incomplete transcripts (the templates in genome replication and mRNA, respectively) of influenza A WSN virus in chicken fibroblasts was analyzed by gel electrophoresis analysis of the duplexes formed between virion RNA and complementary RNA. Three steps in the transcription could be defined: 1) primary transcription when similar amounts of mRNA of all the genes are accumulated; 2) early secondary transcription when mRNA of NS gene is synthesized in larger amounts than that of other genes and 3) late secondary transcription when the amplification of transcription from all the genes is performed. The synthesis of complete transcripts starts during or after primary transcription. When actinomycin D was added to infected cells, the synthesis of incomplete transcripts was inhibited to a larger degree then that of complete transcripts. Most of incomplete transcripts was observed within the cell nucleic while the complete transcripts were found in the nuclei and cytoplasm, suggesting that the synthesis of incomplete transcripts is located in the nuclei. alpha-Amanitin blocked the synthesis of incomplete transcripts without interfering with that of complete transcripts. These data suggest that the synthesis of complete transcripts does not require the synthesis of cell mRNA as primers in transcription.