Sindbis virus-induced viral ribonucleic acid polymerase.

A cytoplasmic structure containing the viral ribonucleic acid (RNA) polymerase has been isolated by sucrose density centrifugation from cells infected with Sindbis virus. Uninfected cells did not contain any such structure. Preliminary experiments indicated that the structure may be associated with membranes. This structure incorporated (3)H-guanosine triphosphate in vitro in the absence of added template. The RNA synthesized in vitro by the enzyme consisted of single-stranded 40S RNA, the ribonuclease-resistant replicative form, and possibly the replicative intermediate form of viral RNA. The products formed in vitro by the enzyme are identical in sedimentation rates to those formed in the infected cells in vivo.