Rubella virus 40S genome RNA specifies a 24S subgenomic mRNA that codes for a precursor to structural proteins

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Abstract
Th structure of the rubella virus genome RNA and the virus-specific RNA species synthesized in African green monkey kidney B-Vero cells infected with rubella virus were analyzed. A single-stranded, capped and polyadenylated RNA species sedimenting at 40S in a sucrose gradient was released from purified virions treated with sodium dodecyl sulfate. This RNA species migrated with a MW of .apprx. 3.8 .times. 106 in an agarose gel after denaturation with glyoxal and dimethyl sulfoxide. Infected cells labeled with [3H]uridine in the presence of actinomycin D contained, in addition to the 40S RNA, a single-stranded polyadenylated 24S RNA species as shown by sucrose gradient analysis. In a Northern blot analysis, this RNA hybridized to a c[complementary]DNA probe derived from the 3'' portion of the genomic 40S RNA. In vitro translation of the 24S RNA species yielded a 110,000-dalton polypeptide, in addition to some smaller products which were immunoprecipitated with an antiserum prepared against the structural proteins E1, E2a, E2b and C. Since the sum of the MW of the nonglycosylated envelope proteins and the capsid protein has been estimated to be .apprx. 116,000, these results suggest that the 24S RNA species represents a subgenomic mRNA coding for a precursor (p110) to the structural proteins of rubella virus. Thus, the strategy of gene expression of rubella virus appears to be similar to that of the alphaviruses.