title: Upf1 and Upf2 proteins mediate normal yeast mRNA degradation when translation initiation is limited.
abstract: mRNA degradation is coupled with the process of mRNA translation. For example, an mRNA molecule, on which translation is prematurely terminated because of a nonsense codon, may be rapidly degraded. This nonsense-mediated mRNA decay in the yeast Saccharomyces cerevisiae is mediated by the Upf1 and Upf2 proteins. Yeast mRNAs can also be selectively destabilized by limiting the rate of translation initiation. Two such destabilized mRNAs, from the SSA1 and SSA2 genes, have been identified using temperature-sensitive mutations affecting the Prt1 component of eukaryotic initiation factor 3. For SSA1 and SSA2 mRNAs, and for structurally modified SSA mRNA derivatives, I show here that degradation is triggered when translation initiation is limited but ongoing. This initiation-dependent mRNA degradation is limited to a subset of mRNAs that includes at least those from the SSA1 and SSA2 genes, and occurs through Upf1- and Upf2-mediated processes, although sequence elements characteristic of nonsense-mediated decay are not evident in these mRNAs.
authors.affiliation: Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia B3H 4H7, Canada. cabarnes@is.dal.ca
authors.forename: C A
authors.initials: CA
authors.lastname: Barnes
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000251:Adenosine Triphosphatases; D015852:Eukaryotic Initiation Factor-2 / Q000235:genetics / Q000502:physiology; D039621:Eukaryotic Initiation Factor-3; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology*; D015966:Gene Expression Regulation, Fungal / Q000502:physiology; D005800:Genes, Fungal / Q000235:genetics; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000502:physiology; D009154:Mutation; D010442:Peptide Chain Initiation, Translational / Q000502:physiology*; D010448:Peptide Initiation Factors / Q000235:genetics; D020365:RNA Helicases; D012331:RNA, Fungal / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D015852:Eukaryotic Initiation Factor-2; D039621:Eukaryotic Initiation Factor-3; D005656:Fungal Proteins; D018840:HSP70 Heat-Shock Proteins; C082119:NGR1 protein, S cerevisiae; C092470:NMD2 protein, S cerevisiae; D010448:Peptide Initiation Factors; D012331:RNA, Fungal; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C542288:SSA2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D000251:Adenosine Triphosphatases; C074151:NAM7 protein, S cerevisiae; C095973:SSA1 protein, S cerevisiae; D020365:RNA Helicases