Early events in the replication of parvovirus LuIII

Purified infectious LuIII virions characterized for their biological and physicochemical properties were used to analyse early events in the interaction of an autonomous parvovirus with its host cell. It could be shown that adsorption and penetration of LuIII virus are rapid processes which, under optimal conditions, can be completed within 30 to 60 minutes of incubation at 37 degrees C. Uncoating of the viral genome is initiated in the cytoplasm and is continued after the virus has been transported to the nucleus. None of these processes appeared to depend on cell cycle-specific helper function(s). However, the first step in viral replication--formation of viral parental RF-DNA consisting of covalently linked complementary strands--evidently could only be achieved in late S-phase of the cell cycle. No evidence was obtained which would support the hypothesis that viral DNA must be integrated into the cellular genome to allow for the initiation of viral DNA synthesis.