ABSTRACT
RNA extracted from purified rinderpest virus was characterised by sucrose gradient sedimentation and polyacrylamide gel electrophoresis. The predominant virion RNA species had a sedimentation constant of 46S and its estimated molecular weight was 4·8 × 106 daltons. Consistently high amounts of UMP and AMP were detected. The melting-temperature profile of the virion RNA suggested absence of secondary structure. The effect of actionomycin D on the replication of rinderpest virus in Vero cells was studied by following the viral RNA synthesis using labelled uridine as well as by infectivity titration. The viral RNA synthesis was not affected until 12 h following infection and was inhibited thereafter between 18 and 48 h to an extent of 25% at 5 and 10 μg levels of the drug. A 100 to 1000-fold reduction in the infectivity titres was observed in the presence of the drug. These results suggest that actinomycin D inhibits rinderpest viral RNA replication. Sedimentation analysis of viral RNA extracted from drug-treated cultures showed inhibition of the genome RNA of rinderpest virus.