Stavnezer E, Ringold G, Varmus H E, Bishop J M
J Virol. 1976 Oct;20(1):342-7. doi: 10.1128/JVI.20.1.342-347.1976.
Cells producing type C (avain sarcoma virus) or type B (mouse mammary tumor virus) RNA tumor viruses contain small amounts of RNA complementary to the viral genomes. The negative strands are complementary to at least 30 to 45% of the viral genomes and are found as RNA-RNA duplexes in the nucleus and cytoplasm of infected cells and in mature virions.