title: Yeast viral 20 S RNA is associated with its cognate RNA-dependent RNA polymerase.
abstract: Most Saccharomyces cerevisiae strains carry in their cytoplasm 20 S RNA, a linear single-stranded RNA molecule of 2.5 kilobases in size. 20 S RNA copy number is greatly induced in stress conditions such as starvation, with up to 100,000 copies per cell. 20 S RNA has coding capacity for a protein of 91 kDa (p91) with sequences diagnostic of RNA-dependent RNA polymerases of (+) strand and double-stranded RNA viruses. We detected p91 in 20 S RNA-carrying strains with specific antisera. The amount of p91 in growing cells is higher than that of stationary cells and similar to the one in 20 S RNA-induced cells. Although 20 S RNA is not encapsidated into viral particles, p91 non-covalently forms a ribonucleoprotein complex with 20 S RNA. This suggests a role of p91 in the RNA to RNA synthesis processes required for 20 S RNA replication. Although the strain analyzed also harbors 23 S RNA, a closely related single-stranded RNA, 23 S RNA is not associated with p91 but with its putative RNA polymerase, p104. Similarly, 20 S RNA is not associated with p104 but with p91. These results suggest that 20 S RNA and 23 S RNA replicate independently using their respective cognate RNA polymerases.
authors.affiliation: Instituto de Microbiología Bioquímica/Departamento de Microbiología y Genética, Consejo Superior de Investigaciones Científicas/Universidad de Salamanca, Spain.
authors.forename: M P
authors.initials: MP
authors.lastname: García-Cuéllar
authors.forename: L M
authors.initials: LM
authors.lastname: Esteban
authors.forename: T
authors.initials: T
authors.lastname: Fujimura
authors.forename: N
authors.initials: N
authors.lastname: Rodríguez-Cousiño
authors.forename: R
authors.initials: R
authors.lastname: Esteban
mesh_terms: D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D012328:RNA Viruses / Q000235:genetics; D012331:RNA, Fungal / Q000235:genetics / Q000378:metabolism*; D012367:RNA, Viral / Q000235:genetics / Q000378:metabolism*; D012324:RNA-Dependent RNA Polymerase / Q000235:genetics / Q000378:metabolism*; D012261:Ribonucleoproteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism* / Q000821:virology*; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D005656:Fungal Proteins; D012331:RNA, Fungal; D012367:RNA, Viral; D012261:Ribonucleoproteins; D014764:Viral Proteins; D012324:RNA-Dependent RNA Polymerase