Linking the 3' poly(A) tail to the subunit joining step of translation initiation: relations of Pab1p, eukaryotic translation initiation factor 5b (Fun12p), and Ski2p-Slh1p.
The 3' poly(A) structure improves translation of a eukaryotic mRNA by 50-fold in vivo. This enhancement has been suggested to be due to an interaction of the poly(A) binding protein, Pab1p, with eukaryotic translation initiation factor 4G (eIF4G). However, we find that mutation of eIF4G eliminating its interaction with Pab1p does not diminish the preference for poly(A)(+) mRNA in vivo, indicating another role for poly(A). We show that either the absence of Fun12p (eIF5B), or a defect in eIF5, proteins involved in 60S ribosomal subunit joining, specifically reduces the translation of poly(A)(+) mRNA, suggesting that poly(A) may have a role in promoting the joining step. Deletion of two nonessential putative RNA helicases (genes SKI2 and SLH1) makes poly(A) dispensable for translation. However, in the absence of Fun12p, eliminating Ski2p and Slh1p shows little enhancement of expression of non-poly(A) mRNA. This suggests that Ski2p and Slh1p block translation of non-poly(A) mRNA by an effect on Fun12p, possibly by affecting 60S subunit joining.
Searfoss
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Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0830, USA.
Dever
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Wickner
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D053487:DEAD-box RNA Helicases; D018274:Electroporation; D040061:Eukaryotic Initiation Factor-5; D005656:Fungal Proteins / Q000378:metabolism*; D017353:Gene Deletion; D017930:Genes, Reporter; D007700:Kinetics; D008954:Models, Biological; D009154:Mutation; D010448:Peptide Initiation Factors / Q000378:metabolism*; D011061:Poly A / Q000235:genetics*; D039102:Poly(A)-Binding Proteins; D014176:Protein Biosynthesis; D020365:RNA Helicases / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D013489:Suppression, Genetic; D013997:Time Factors
D040061:Eukaryotic Initiation Factor-5; D005656:Fungal Proteins; D010448:Peptide Initiation Factors; D039102:Poly(A)-Binding Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C081929:SKI2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D011061:Poly A; C432685:SLH1 protein, S cerevisiae; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases