Prions and RNA viruses of Saccharomyces cerevisiae.
Saccharomyces cerevisiae is host to the dsRNA viruses L-A (including its killer toxin-encoding satellite, M) and L-BC, the 20S and 23S ssRNA replicons, and the putative prions, [URE3] and [PSI]. review the genetic and biochemical evidence indicating that [URE3] and [PSI] are prion forms of Ure2p and Sup35p, respectively. Each has an N-terminal domain involved in propagation or generation of the prion state and a C-terminal domain responsible for the protein's normal function, nitrogen regulation, or translation termination, respectively. The L-A dsRNA virus expression, replication, and RNA packaging are reviewed. L-A uses a -1 ribosomal frameshift to produce a Gag-Pol fusion protein. The host SK12, SK13 and SK18 proteins block translation of nonpoly(A) mRNAs (such as viral mRNA). Mutants deficient in 60S ribosomal subunits replicate L-A poorly, but not if cells are also ski-. Interaction of 60S subunits with the 3' polyA is suggested. SKI1/XRN1 is a 5'--> 3' exoribonuclease that degrades uncapped mRNAs. The viral Gag protein decapitates cellular mRNAs apparently to decoy this enzyme from working on viral mRNA.
Wickner
R B
RB
National Institute of Diabetes, Digestive and Kidney Disease, National Institute of Health, Bethesda, Maryland 20892-0830, USA.
D000595:Amino Acid Sequence; D000818:Animals; D001927:Brain Diseases / Q000821:virology; D008969:Molecular Sequence Data; D011328:Prions / Q000235:genetics*; D012328:RNA Viruses / Q000235:genetics / Q000502:physiology*; D012330:RNA, Double-Stranded; D012441:Saccharomyces cerevisiae / Q000821:virology*
D011328:Prions; D012330:RNA, Double-Stranded