Frog virus 3 morphogenesis: effect of temperature and metabolic inhibitors

The different stages of frog virus 3 (FV 3) morphogenesis have been investigated in chick embryo fibroblasts infected at an optimal temperature for virus growth (29 degrees C). The metabolic requirements for morphogenesis were determined by adding inhibitors of macromolecular synthesis at different periods in the virus growth cycle. The effect of a non-permissive temperature for FV 3 replication (37 degrees C) was also studied in shift up experiments. The following results were obtained: (I) when DNA replication was inhibited, neither immature nor mature virus particles appeared; (2) continuous protein synthesis was required for every stage of virus morphogenesis. However, the assembly of virions into paracrystalline arrays seemed to be a passive phenomenon. (3) Continuous mRNA transcription was not necessary for assembly of capsid constituents, although most of these capsids appeared empty; there was also a striking increase in the number of aberrant virus structures. (4) If infected cells were shifted to a non-permissive temperature, virus maturation was completely inhibited.