Association of yeast viral 23 S RNA with its putative RNA-dependent RNA polymerase.
T double-stranded RNA (dsRNA) and its single-stranded RNA (ssRNA) counterpart, 23 S RNA, are present in some strains of the yeast Saccharomyces cerevisiae. 23 S RNA is identical with the T (+)-strand, and both are cytoplasmically inherited. The T (+)-strand encodes a protein of 104 kilodaltons (kDa) (p104) that has sequences diagnostic of RNA-dependent RNA polymerases from (+)-strand and double-stranded RNA viruses. Here we show that p104 is expressed only in yeast strains carrying T dsRNA (and 23 S RNA) and that the ability to produce p104 is co-transmitted from one strain to another by cytoplasmic mixing (cytoduction) along with T dsRNA. Neither T nor 23 S RNA is encapsidated into viral particles; however, the latter was found to be non-covalently associated with p104. This finding was based on the evidence that: (i) both 23 S RNA and p104 cosedimented in sucrose gradients and that (ii) 23 S RNA was immunoprecipitated by a p104-specific polyclonal antiserum. Consistent with this association, p104 shows single-stranded RNA-binding activity in Northwestern blots. We have localized the RNA-binding domain of p104 within its C terminus 234 amino acids.
Instituto de Microbiología Bioquímica/Departamento de Microbiología y Genética, Consejo Superior de Investigaciones Científicas/Universidad de Salamanca, Spain.
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Esteban
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Fujimura
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García-Cuéllar
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Esteban
D005656:Fungal Proteins / Q000378:metabolism; D007106:Immune Sera; D011233:Precipitin Tests; D011485:Protein Binding; D012328:RNA Viruses / Q000378:metabolism*; D012338:RNA, Ribosomal, 23S / Q000378:metabolism*; D012367:RNA, Viral / Q000378:metabolism*; D012324:RNA-Dependent RNA Polymerase / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000821:virology*; D013395:Sucrose
D005656:Fungal Proteins; D007106:Immune Sera; D012338:RNA, Ribosomal, 23S; D012367:RNA, Viral; D013395:Sucrose; D012324:RNA-Dependent RNA Polymerase