Replication of measles virus: continued synthesis of nucleocapsid RNA and increased synthesis of mRNA in the presence of cycloheximide.

The effect of cycloheximide on virus specific RNA synthesis in Vero cells infected with either wild-strain (Edmonston) or subacute sclerosing panencephalitis strain measles virus was investigated. At 3 days postinfection, cells treated with cycloheximide (2.6 x 10(-4) M) and then exposed to [(3)H]uridine showed a marked increase in labeled virus-specific RNA. A major portion of this incremental labeled RNA was putative viral mRNA which sedimented at 16, 22, and 30S. Five distinct classes of polyribosomes, which were not evident in untreated cells, were found in cycloheximide-treated cells and each contained similar species of virus-specific RNA. Viral nucleocapsid RNA, 50 and 18S, was synthesized and encapsidated in the presence of cycloheximide. The latter observation is in apparent contrast to reports that cycloheximide inhibits replication of RNA of classical paramyxoviruses, and may indicate that mechanisms for replicating RNA of measles virus are different from those for replicating RNA of paramyxoviruses.