Abstract
Uninfected chicken embryo cells were analyzed for the presence of viral ribonucleic acid (RNA) by molecular hybridization with the single-stranded deoxyribonucleic acid (DNA) product of the RNA-dependent DNA polymerase contained in avian sarcoma-leukosis virions. Viral RNA was detected in all cells which contained the avian tumor virus group-specific antigen and the virus-related helper factor. The amounts of viral RNA in these cells ranged from approximately 3 to 40 copies of viral-specific sequences per cell. In general, the viral RNA content correlated with the level of helper activity in the cells. Cells infected with Rous-associated virus 2 contained 3,000 to 4,000 copies of viral RNA per cell. RNA from these infected cells hybridized with nearly 100% of the viral (3)H-DNA. By contrast, a maximum of less than 50% hybridization was obtained with RNA from the uninfected helper-positive cells, suggesting that not all of the viral RNA sequences were present in these cells. No viral RNA was detected in cells which lacked group-specific antigen and helper activity. Under the conditions used in these studies, less than 0.3 viral genome equivalents of RNA per cell would have been detected.