Metabolic requirements for infection by Rous sarcoma virus: I. The transient requirement for DNA synthesis

Abstract

The replication of Rous sarcoma virus (RSV) was demonstrated to require DNA synthesis only during the early stages of the infectious cycle. A specific inhibitor of DNA synthesis, d-arabinosyl cytosine (cytosine arabinoside), prevented virus growth if added within 8 hours after initial exposure of cells to RSV, but virus growth was unaffected by later addition of the antibiotic. The addition of puromycin or 2,6-diaminopurine riboside later than 8 hours after RSV prevented further increase of infectious virus, demonstrating that RNA and protein synthesis are continuously required for growth of RSV. Cells maintained on a serum-deficient medium lost the ability to synthesize DNA, while RNA and protein synthesis continued at a high rate. Cells infected after serum depletion yielded little virus if maintained on serum-deficient medium, but cells infected prior to serum depletion produced large quantities of virus for as long as 39 days after serum depletion. These experiments support the interpretation of antimetabolite data and demonstrate that the DNA required for virus replication is not a “pool” of DNA synthesized early in infection and incorporated later into virions. A requirement for protein synthesis during the early phase of RSV-infection was examined using puromycin and d-arabinosyl cytosine. The DNA-synthetic phase proceeded in the presence of puromycin, demonstrating that preexisting cellular enzymes are sufficient to establish the required DNA.