Identification of four complementary RNA species in Akabane virus-infected cells

Abstract

The analysis of RNA extracted from purified Akabane virus demonstrated the presence of three size classes of single-stranded RNAs with sedimentation coefficients of 31S (large, L), 26S (medium, M), and 13S (small, S). Molecular weights of these RNA species were estimated to be 2.15 X 10(6), 1.5 X 10(6), and 0.48 X 10(6) for the L, M, and S RNAs, respectively. Hybridization analysis involving viral genomic RNA and RNA from virus-infected cells resulted in the identification of four virus-specific cRNA species in infected cells. These cRNAs were found to be nonpolyadenylated by their inability to bind to oligodeoxythymidylate-cellulose. Kinetic analysis of cRNA synthesis in infected cells at various times postinfection suggested that cRNA synthesis could be detected as early as 2 h postinfection and that maximal synthesis occurred at 4 to 6 h postinfection. The RNAs synthesized in infected cells could be partially resolved by sucrose density gradient centrifugation. The RNA fraction that cosedimented with the S segment of viral genomic RNA yielded two duplex RNA species when hybridized with viral genomic RNA, suggesting the presence of two small cRNA species. Specific hybridization with individual viral genomic RNAs confirmed that two species of cRNA are coded by the S RNA segment. Analysis of cRNA synthesis in the presence of the protein synthesis inhibitors cycloheximide and puromycin indicated that cycloheximide completely inhibited virus-specific RNA synthesis early and late in infection, whereas a very low level of synthesis occurred in the presence of puromycin. The inhibitory effects of these drugs were found to be reversible when the drugs were washed from the cells. It is concluded that continued protein synthesis is required for cRNA synthesis to proceed in Akabane virus-infected cells.