Characterization of a replication-defective temperature-sensitive mutant of Rous sarcoma virus.

A temperature-sensitive mutant (LA83) of Rous sarcoma virus defective both in the transformation and replication function has been isolated and partially characterized. Temperature-shift experiments showed that the defects in both the focus-forming and replication functions were late and continuous. The mutant LA83 was complemented by avian leukosis viruses. Complementation of LA83 replication was also observed with the glycoprotein-deletion mutant, Brian high-titer RSV(-) suggesting that the env gene in LA83 was not defective. At the nonpermissive temperature LA83-infected cells produced noninfectious particles with a yield of about 30%. The noninfectious particles had only about 3% of reverse-transcriptase activity as the infectious LA83 produced at the permissive temperature. However, the LA83 virions were as thermolabile as the parent wild-type PR-B virions.