Nonsense-mediated mRNA decay (NMD) in mammalian cells is restricted to newly synthesized mRNA that is bound at the 5' cap by the major nuclear cap-binding complex and at splicing-generated exon-exon junctions by exon junction complexes. This messenger ribonucleoprotein has been called the pioneer translation initiation complex and, accordingly, NMD occurs as a consequence of nonsense codon recognition during a pioneer round of translation. Here, we characterize the nature of messenger ribonucleoprotein that is targeted for NMD in Saccharomyces cerevisiae. Data indicate that NMD targets both cap-binding complex (Cbc)1p- and eukaryotic translation initiation factor (eIF)4E-bound mRNAs, unlike in mammalian cells, where NMD does not detectably target eIF4E-bound mRNA. First, intron-containing pre-mRNAs in yeast are detectably bound by either Cbc1p, or, unlike in mammalian cells, eIF4E, indicating that mRNAs can be derived from either Cbc1p- or eIF4E-bound pre-mRNAs. Second, the ratio of nonsense-containing Cbc1p-bound mRNA to nonsense-free Cbc1p-bound mRNA, which was < 0.4 for those mRNAs tested here, is essentially identical to the ratio of the corresponding nonsense-containing eIF4E-bound mRNA to nonsense-free eIF4E-bound mRNA, and both ratios increase in cells treated with the translational inhibitor cycloheximide (CHX). These data, together with data presented here and elsewhere showing that Cbc1p-bound transcripts are precursors to eIF4E-bound transcripts, demonstrate that Cbc1p-bound mRNA is targeted for NMD. In support of the idea that eIF4E-bound mRNA is also targeted for NMD, eIF4E-bound mRNA is targeted for NMD in strains that lack Cbc1p. These results suggest that both Cbc1p- and eIF4E-mediated pioneer rounds of translation occur in yeast.
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Evidence ID | Analyze ID | Gene/Complex | Systematic Name/Complex Accession | Qualifier | Gene Ontology Term ID | Gene Ontology Term | Aspect | Annotation Extension | Evidence | Method | Source | Assigned On | Reference |
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Evidence ID | Analyze ID | Gene | Gene Systematic Name | Phenotype | Experiment Type | Experiment Type Category | Mutant Information | Strain Background | Chemical | Details | Reference |
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Evidence ID | Analyze ID | Gene | Gene Systematic Name | Disease Ontology Term | Disease Ontology Term ID | Qualifier | Evidence | Method | Source | Assigned On | Reference |
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Evidence ID | Analyze ID | Regulator | Regulator Systematic Name | Target | Target Systematic Name | Direction | Regulation of | Happens During | Regulator Type | Direction | Regulation Of | Happens During | Method | Evidence | Strain Background | Reference |
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Site | Modification | Modifier | Source | Reference |
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Evidence ID | Analyze ID | Interactor | Interactor Systematic Name | Interactor | Interactor Systematic Name | Allele | Assay | Annotation | Action | Phenotype | SGA score | P-value | Source | Reference | Note |
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Evidence ID | Analyze ID | Interactor | Interactor Systematic Name | Interactor | Interactor Systematic Name | Assay | Annotation | Action | Modification | Source | Reference | Note |
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Complement ID | Locus ID | Gene | Species | Gene ID | Strain background | Direction | Details | Source | Reference |
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Evidence ID | Analyze ID | Dataset | Description | Keywords | Number of Conditions | Reference |
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Evidence ID | Analyze ID | File | Description |
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