Launching of the yeast 20 s RNA narnavirus by expressing the genomic or antigenomic viral RNA in vivo.
20 S RNA virus is a persistent positive strand RNA virus found in Saccharomyces cerevisiae. The viral genome encodes only its RNA polymerase, p91, and resides in the cytoplasm in the form of a ribonucleoprotein complex with p91. We succeeded in generating 20 S RNA virus in vivo by expressing, from a vector, genomic strands fused at the 3'-ends to the hepatitis delta virus antigenomic ribozyme. Using this launching system, we analyzed 3'-cis-signals present in the genomic strand for replication. The viral genome has five-nucleotide inverted repeats at both termini (5'-GGGGC... GCCCC-OH). The fifth G from the 3'-end was dispensable for replication, whereas the third and fourth Cs were essential. The 3'-terminal and penultimate Cs could be eliminated or modified to other nucleotides; however, the generated viruses recovered these terminal Cs. Furthermore, extra nucleotides added at the viral 3'-end were eliminated in the launched viruses. Therefore, 20 S RNA virus has a mechanism(s) to maintain the correct size and sequence of the viral 3'-end. This may contribute to its persistent infection in yeast. We also succeeded in generating 20 S RNA virus similarly from antigenomic strands provided active p91 was supplied from a second vector in trans. Again, a cluster of four Cs at the 3'-end in the antigenomic strand was essential for replication. In this work, we also present the first conclusive evidence that 20 S and 23 S RNA viruses are independent replicons.
Esteban
Rosa
R
Instituto de Microbiología Bioquímica/Departamento de Microbiología y Genética, Consejo Superior de Investigaciones Científicas/Universidad de Salamanca, Salamanca 37007, Spain. mrosagugu.usal.es
Vega
Lorena
L
Fujimura
Tsutomu
T
D004279:DNA, Viral; D012328:RNA Viruses / Q000235:genetics* / Q000502:physiology; D012335:RNA, Ribosomal; D012367:RNA, Viral; D012093:Replicon; D012441:Saccharomyces cerevisiae / Q000502:physiology / Q000821:virology*; D017423:Sequence Analysis, RNA; D014779:Virus Replication
D004279:DNA, Viral; D012335:RNA, Ribosomal; D012367:RNA, Viral