An RNA-Dependent DNA Polymerase in Virions of Rous Sarcoma Virus

Many spontaneous tumors in animals are associated with viruses of a particular class—the RNA tumor viruses. These viruses have virions of about 100 mµ diameter, a lipid-containing envelope, and an internal ribonucleoprotein core or nucleoid containing single-stranded RNA. The RNA tumor viruses are non-cytopathic; they do not kill infected cells, but replicate along with the infected cells. The replication may or may not include production of infectious virus, and may or may not be associated with the conversion of the infected cell to a tumor cell. The replication of the nucleic acid of RNA tumor viruses has appeared to be different from that of other RNA viruses since early experiments with inhibitors. First, it was found that virus production was sensitive to actinomycin D (Temin, 1963), then that inhibition of DNA synthesis soon after infection blocked virus production (Bader, 1964; Temin, 1964a), and third, that there appeared to be increased...