The double-stranded RNA genome of yeast virus L-A encodes its own putative RNA polymerase by fusing two open reading frames.
The L-A double-stranded RNA virus of Saccharomyces cerevisiae encodes its major coat protein (80 kDa) and a minor single-stranded RNA binding protein (180 kDa) that has immunological cross-reactivity with the major coat protein. The sequence of L-A cDNA clones revealed two open reading frames (ORF), ORF1 and ORF2. These two reading frames overlap by 130 base pairs and ORF2 is in the -1 reading frame with respect to ORF1. Although the major coat protein of the viral particles is encoded by ORF1, the 180-kDa protein is derived from the entire double-stranded RNA genome by fusing ORF1 and ORF2, probably by a -1 translational frameshift. Within the overlapping region is a sequence similar to that producing a -1 frameshift by "simultaneous slippage" in retroviruses. The coding sequence of ORF2 shows a pattern characteristic of viral RNA-dependent RNA polymerases of icosahedral (+)-strand RNA viruses. Thus, the 180-kDa protein is analogous to gag-pol fusion proteins.
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Section on Genetics of Simple Eukaryotes, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland 20892.
Wickner
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D000595:Amino Acid Sequence; D001483:Base Sequence; D002213:Capsid / Q000235:genetics; D012321:DNA-Directed RNA Polymerases / Q000235:genetics*; D005796:Genes; D005814:Genes, Viral; D006860:Hydrogen Bonding; D008969:Molecular Sequence Data; D008970:Molecular Weight; D012330:RNA, Double-Stranded / Q000235:genetics* / Q000648:ultrastructure; D012367:RNA, Viral / Q000235:genetics*; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000235:genetics*
D012330:RNA, Double-Stranded; D012367:RNA, Viral; D012321:DNA-Directed RNA Polymerases