On the origin of RNA tumor viruses.

Abstract

RNA tumor viruses are enveloped animal viruses whose virions contain an RNA genome and a DNA polymerase. RNA tumor viruses have been isolated from reptiles, birds, and many orders of mammals, including primates. However, none has been isolated from man. In susceptible animals, RNA tumor viruses cause leukemias, sarcomas, carcinomas, rapid lethal infections with anemia and necrosis, slow infections of the nervous system and lung, and, most frequently, no disease. (The nonpathogenic RNA tumor viruses are assayed by the formation of virion components.) The name RNA tumor viruses describes the oncogenicity of some of the members of the virus group. It does not mean that all of the viruses that belong to this group cause tumors. RNA tumor viruses are also called leukoviruses, rousviruses, oncor­ naviruses, retraviruses, retroviruses, ambiviruses, rnadnaviruses, oncoviruses, and ribodeoxyviruses. I prefer the name ribodeoxyviruses. RNA tumor viruses are very popular organisms for study for several reasons: I. all RNA tumor viruses replicate using RNA to DNA to RNA information transfer, a previously unknown mode of information transfer discovered in this group of viruses; 2. some RNA tumor viruses are the apparent cause of much natural cancer in chickens and in mice; and 3. some RNA tumor viruses, for example the strongly transforming Rous sarcoma virus, are the most efficient carcinogenic agents known in animals or in cell culture. (Transformation is used in animal cell culture