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.

CiteULike

Complore

Connotea

Del.icio.us

Digg

Reddit

Technorati

This article has been cited by other articles:

				R. Esteban, L. Vega, and T. Fujimura 20S RNA Narnavirus Defies the Antiviral Activity of SKI1/XRN1 in Saccharomyces cerevisiae J. Biol. Chem., September 19, 2008; 283(38): 25812 - 25820. [Abstract] [Full Text] [PDF]

				T. Fujimura and R. Esteban Interactions of the RNA Polymerase with the Viral Genome at the 5'- and 3'-Ends Contribute to 20S RNA Narnavirus Persistence in Yeast J. Biol. Chem., June 29, 2007; 282(26): 19011 - 19019. [Abstract] [Full Text] [PDF]

				R. Esteban, L. Vega, and T. Fujimura Launching of the Yeast 20 S RNA Narnavirus by Expressing the Genomic or Antigenomic Viral RNA in Vivo J. Biol. Chem., October 7, 2005; 280(40): 33725 - 33734. [Abstract] [Full Text] [PDF]

				T. Fujimura, A. Solorzano, and R. Esteban Native Replication Intermediates of the Yeast 20 S RNA Virus Have a Single-stranded RNA Backbone J. Biol. Chem., February 25, 2005; 280(8): 7398 - 7406. [Abstract] [Full Text] [PDF]

				T. Fujimura and R. Esteban Bipartite 3'-Cis-acting Signal for Replication in Yeast 23 S RNA Virus and Its Repair J. Biol. Chem., March 26, 2004; 279(13): 13215 - 13223. [Abstract] [Full Text] [PDF]

				N. Rodriguez-Cousino, A. Solorzano, T. Fujimura, and R. Esteban Yeast Positive-stranded Virus-like RNA Replicons. 20 S AND 23 S RNA TERMINAL NUCLEOTIDE SEQUENCES AND 3' END SECONDARY STRUCTURES RESEMBLE THOSE OF RNA COLIPHAGES J. Biol. Chem., August 7, 1998; 273(32): 20363 - 20371. [Abstract] [Full Text] [PDF]

				A. Solorzano, N. Rodriguez-Cousino, R. Esteban, and T. Fujimura Persistent Yeast Single-stranded RNA Viruses Exist in Vivo as Genomic RNA{middle dot}RNA Polymerase Complexes in 1:1 Stoichiometry J. Biol. Chem., August 18, 2000; 275(34): 26428 - 26435. [Abstract] [Full Text] [PDF]