title: Initiation-mediated mRNA decay in yeast affects heat-shock mRNAs, and works through decapping and 5'-to-3' hydrolysis.
abstract: The degradation of mRNA in the yeast Saccharomyces cerevisiae takes place through several related pathways. In the most general mRNA-decay pathway, that of poly(A)-dependent decay, the normal shortening of the poly(A) tail on an mRNA molecule by deadenylation triggers mRNA decapping by the enzyme Dcp1p, followed by exonucleolytic digestion by Xrn1p. A specialized mRNA-decay pathway, termed nonsense-mediated decay, comes into play for mRNAs that contain an early nonsense codon. This pathway operates through the Upf proteins in addition to Dcp1p and Xrn1p. Previously, we identified a different specialized mRNA-decay pathway, the initiation-mediated decay pathway, and showed that it affects two Hsp70 heat-shock mRNAs under conditions of slowed translation initiation. Here we report that initiation-mediated mRNA decay also works through the Dcp1 and Xrn1 enzymes, and requires ongoing transcription by RNA polymerase II. We show that several other heat-shock mRNAs, including two from the Hsp90 gene family and three more from the Hsp70 gene family, are also subject to initiation-mediated decay, whereas a variety of non-heat-shock mRNAs are not affected.
authors.affiliation: Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada B3H 1X5.
authors.forename: Heather L
authors.initials: HL
authors.lastname: Heikkinen
authors.forename: Sara A
authors.initials: SA
authors.lastname: Llewellyn
authors.forename: Christine A
authors.initials: CA
authors.lastname: Barnes
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D004722:Endoribonucleases / Q000235:genetics; D005095:Exoribonucleases / Q000235:genetics; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics; D018841:HSP90 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000235:genetics*; D006868:Hydrolysis; D014176:Protein Biosynthesis / Q000235:genetics*; D039381:RNA Cap-Binding Proteins; D012315:RNA Caps / Q000235:genetics; D020365:RNA Helicases / Q000235:genetics; D020871:RNA Stability; D012331:RNA, Fungal / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics; D015534:Trans-Activators / Q000235:genetics; D014158:Transcription, Genetic / Q000235:genetics
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D018840:HSP70 Heat-Shock Proteins; C074510:HSP82 protein, S cerevisiae; D018841:HSP90 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C092470:NMD2 protein, S cerevisiae; D039381:RNA Cap-Binding Proteins; D012315:RNA Caps; D012331:RNA, Fungal; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C090869:SSA3 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; C100868:DCP1 protein, S cerevisiae; D004722:Endoribonucleases; D005095:Exoribonucleases; C068398:XRN1 protein, S cerevisiae; C074151:NAM7 protein, S cerevisiae; D020365:RNA Helicases