Ribosomal frameshifting efficiency and gag/gag-pol ratio are critical for yeast M1 double-stranded RNA virus propagation.
About 1.9% of ribosomes translating the gag open reading frame of the yeast L-A double-stranded RNA virus positive strand undergo a -1 frameshift and continue translating in the pol open reading frame to make a 170-kDa gag-pol fusion protein. The importance of frameshifting efficiency for viral propagation was tested in a system where the M1 (killer toxin-encoding) satellite RNA is supported by a full-length L-A cDNA clone. Either increasing or decreasing the frameshift efficiency more than twofold by alterations in the slippery site disrupted viral propagation. A threefold increase caused by a chromosomal mutation, hsh1 (high shifter), had the same effect. Substituting a +1 ribosomal frameshift site from Ty1 with the correct efficiency also allowed support of M1 propagation. The normal -1 frameshift efficiency is similar to the observed molar ratio in viral particles of the 170-kDa gag-pol protein to the 70-kDa gag gene product, the major coat protein. The results are interpreted in terms of a packaging model for L-A.
Dinman
J D
JD
Section on the Genetics of Simple Eukaryotes, National Institute of Diabetes, Digestive and Kidney Diseases, Bethesda, Maryland 20892.
Wickner
R B
RB
D001483:Base Sequence; D016368:Frameshift Mutation / Q000187:drug effects; D005656:Fungal Proteins / Q000494:pharmacology; D015685:Fusion Proteins, gag-pol / Q000378:metabolism; D015683:Gene Products, gag / Q000378:metabolism; D006790:Host-Parasite Interactions; D055646:Killer Factors, Yeast; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D009690:Nucleic Acid Conformation; D011506:Proteins / Q000494:pharmacology; D012328:RNA Viruses / Q000187:drug effects / Q000254:growth & development*; D012330:RNA, Double-Stranded / Q000378:metabolism; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism; D012367:RNA, Viral / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D014779:Virus Replication
D005656:Fungal Proteins; D015685:Fusion Proteins, gag-pol; D015683:Gene Products, gag; D055646:Killer Factors, Yeast; D011506:Proteins; D012330:RNA, Double-Stranded; D012346:RNA, Transfer, Amino Acyl; D012367:RNA, Viral