Rous sarcoma virus synthesis

This enzyme is associated with the virions of RNA tumor viruses such as the Rous sarcoma virus (RSV). The enzyme has remarkable enzymatic activity in that it can catalyze several seemingly diverse steps in the synthesis of double-stranded DNA from the single-stranded RNA viral genome. The enzyme uses a tRNA for tryp-tophan as a primer to make a copy of DNA that is complementary to the viral RNA. The resulting RNA-DNA hybrid is converted to a double-stranded DNA molecule by ribon-uclease (RNase)H and DNA-dependent DNA polymerase activities that are intrinsic to reverse transcriptase. 

Cerulenin inhibits formation of polyisoprenol, probably by uncom-petitively inhibiting HMG-CoA synthetase.250 It strongly inhibited production of Rous-sarcoma virus by infected, chick-embryo cells, but an effect on the viral glycoproteins was not observed.251 Other effects of cerulenin, such as its inhibition of fatty acid synthesis, may have caused inhibition of virus production. The inhibition, by cerulenin, of secretion of proteins by bacilli has been noted for some time, but no satisfactory explanation has as yet been offered (see Ref. 252, and ref-... 

Density-gradient separations of cytoplasmic fractions from liver have been carried out to study the distribution of activity of several enzymes (Thomson, 1959). Ribosomes and polysomes have been fractionated to elucidate the mechanisms of protein synthesis (Watson, 1964), Various viruses have been studied with the density-gradient technique polio virus (Levintow and Darnell, 1960), Rous sarcoma virus (Crawford, 1960), Shope papilloma virus (Williams et ai, 1960), and adenoviruses (Allison et ai, 1960). Density-gradient fractionation has been particularly useful for separation of DNA molecules from various species of bacteria (Rolfe and Meselson, 1959) and from animal cells (Kit, 1961), Other types of molecules, e.g., antibodies, lipoproteins, and rheumatoid factor have been isolated by density-gradient methods [see Charlwood (1966) for examples]. 

Defective viruses viruses that lack genes for the synthesis of functional capsid or envelope proteins. For example, the Rous sarcoma virus is unable to synthesize one of its envelope proteins. In order to complete its replication cycle and form new virus particles, the missing gene must be provided by a helper virus. The helper virus is a member of a group of viruses often found in association with the Rous sarcoma virus, and known as Rous-associated viruses (RAV). In the absence of an RAV, the normal host cell is transformed into a tumor-forming cell. Most acute transforming Retroviridae are D.v. Deficient viruses (see) are often included with the D.v. 

Thomas and J. A. Montgomery, Adenosylhomocysteine hydrolase Inhibitors synthesis of 5 -deoxy-5 -(isobutylthio)-3-deaza-adenosine and its effect on Rous sarcoma virus and Gross murine leukemia virus, Blochem. Biophys. Res. Commun. 82 417 (1978). 

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