The structure of the RNA of RNA-containing tumor viruses

An association between globin messenger RNA and 60S RNA derived from Friend leukemia virus

The association between certain cellular RNAs and purified RNA tumor viruses prompted us to examine the possibility that specific host messenger RNAs might also be incorporated into RNA tumor viruses. Using a mouse cell line infected with Friend leukemia virus, T-3-Cl-2, which can be induced to accumulate mouse-globin messenger RNA, we show that mouse-globin messenger RNA sequences are present in viral particles purified from the culture medium of globin-producing cells. These globin messenger RNA sequences are absent from viral particles derived from T-3-Cl-2 cells that are not producing globin messenger RNA. Virus-associated globin messenger RNA sequences sediment in association with the 60S viral RNA complex as well as in free, 9S form. However, under mild denaturing conditions which result in the conversion of viral 60S RNA to 30S and smaller forms, all the globin sequences sediment as 9S RNA. Appropriate control experiments indicate that the virus-associated globin messenger RNA is resistant to degradation by exogenous ribonuclease; that exogenously added globin messenger RNA does not become associated with the 60S viral RNA complex; and that globin messenger RNA can be detected in virions derived from cells both induced for and constitutively synthesizing globin messenger RNA.

The 3'-terminal nucleosides of the high molecular weight RNA of avian myeloblastosis virus

The RNA isolated from avian myeloblastosis virus was fractionated by sucrose density gradient centrifugation. The 3'-OH terminal nucleosides of various fractions were determined by periodate oxidation followed by tritiated borohydride reduction. The 60-70S fraction and the 35S RNA derived from it by heating both have adenosine as the major terminal nucleoside, with cytidine as the next most frequent terminal. Control samples of tRNA(met) (f. coli) and 28S ribosomal RNA from mouse ascites tumor cells gave the expected terminal residues and molecular weights.