Replication of Sindbis Virus V. Polyribosomes and mRNA in Infected Cells

Abstract

Cells infected with wild-type Sindbis virus contain at least two forms of mRNA, 26 S and 49 S RNA. Sindbis 26 S RNA (molecular weight 1.6 × 10 6 ) constitutes 90% by weight of the mRNA in infected cells, and is thought to specify the structural proteins of the virus. Sindbis 49 S RNA, the viral genome (molecular weight 4.3 × 10 6 ), constitutes approximately 10% of the mRNA in infected cells and is thought to supply the remaining viral functions. In cells infected with ts2 , a temperature-sensitive mutant of Sindbis virus, the messenger forms also include a third species of RNA with a sedimentation coefficient of 33 S and an apparent molecular weight of 2.3 × 10 6 . Hybridization-competition experiments showed that 90% of the base sequences in 33 S RNA from these cells are also present in 26 S RNA. Sindbis 33 S RNA was also isolated from cells infected with wild-type virus. After reaction with formaldehyde, this species of 33 S RNA appeared to be completely converted to 26 S RNA. These results indicate that 33 S RNA isolated from cells infected with either wild-type Sindbis or ts2 is not a unique and separate form of Sindbis RNA.