Transcription by Infectious Subviral Particles of Reovirus

Abstract

Digestion of purified reovirus with chymotrypsin in the presence of 0.15 M NaCl converts virions to infectious subviral particles (SVP i ). The SVP i have an active ribonucleic acid (RNA) polymerase and are similar in composition to the partially uncoated virions which have been isolated from infected L cells. SVP i have a buoyant density of 1.40 g/ml in CsCl and sediment at 420 S as compared to 1.37 g/ml and 630 S for virions. They consist of 30% less protein and include the polypeptides of the inner structural layer, λ 1 , λ 2 , and σ 3 , and a polypeptide derived by cleavage of μ 2 , a constituent of the outer shell. The genome RNA is retained within SVP i , but more than 60% of the “adenine-rich,” single-stranded RNA is released by the proteolytic treatment. Infection of L cells with SVP i or virions results in the transcription of all 10 genome segments. In cycloheximide-treated SVP i -infected cells, transcription occurs predominantly from one medium and two small genome segments, the same pattern of early messenger RNA (mRNA) observed in virion-infected cells. In contrast, SVP i incubated in vitro synthesize mRNA corresponding to all genome segments.