Abstract
The sensitivity to actinomycin D of the early steps of the in vitro replication of murine sarcoma virus (Moloney) (M-MSV) was investigated by treating infected mouse cells with the antibiotic (0.25 µg/ml) for 6 h periods at several times after infection. The results obtained indicate that M-MSV production is inhibited when actinomycin D is added within 2 h of infection.