Influenza virus RNA is synthesized at fixed sites in the nucleus

We have recently shown that cellular RNA is synthesized at a sub-nuclear structure, the nuclear cage1, which contains proteins also found in other structures called variously the nuclear pore complex, lamina, envelope and matrix2-6. Is the RNA of an exogenous virus also synthesized at the cage? We chose to study influenza virus as it is unusual in its requirement for a host cell nucleus even though there are no cellular counterparts to the transcription of the infecting negative strands of genomic influenza RNA, nor to the replication of the resulting positive RNA strands to form new virion RNA. The cellular sites of these processes have not yet been definitively demonstrated7,8. We now show that nascent viral transcripts are closely associated with the cage and we conclude not only that transcription and replication of viral RNA are nuclear, but also that they occur at fixed sites in the nucleus. © 1982 Nature Publishing Group.