Defective Interfering Passages of Sindbis Virus: Nature of the Intracellular Defective Viral RNA

BHK cells infected with defective-interfering passages of Sindbis virus accumulate a species of RNA (20S) that is about half the molecular weight of the major viral mRNA (26S). We have performed competitive hybridization experiments with these species of RNA and have established that 20S RNA contains approximately 50% of the nucleotide sequences present in 26S RNA. Our further studies, however, demonstrate that 20S RNA is unable to carry out the messenger function of 26S RNA. We found very little of the defective RNA associated with polysomes in vivo. In addition, it was unable to stimulate protein synthesis in vitro under conditions in which 26S RNA was translated. We have also examined viral RNA synthesis in BHK cells infected with standard or defective-interfering passages of Sindbis virus. This comparison suggests that defective partioles do not synthesize a functional replicase.