Abstract
Nonsense-mediated mRNA decay (NMD) is a surveillance mechanism that eliminates mRNAs containing premature termination codons (PTCs). The proteins UPF1, SMG5, SMG6, and SMG7 are essential NMD factors in metazoa. SMG5 and SMG7 form a complex with UPF1 and interact with each other via their N-terminal domains. Here we show that SMG5 and SMG7 colocalize in cytoplasmic mRNA decay bodies, while SMG6 forms separate cytoplasmic foci. When SMG7 is tethered to a reporter transcript, it elicits its degradation, bypassing the requirement for a PTC, UPF1, SMG5, or SMG6. This activity is mediated by the C-terminal domain of SMG7. In contrast, SMG5 requires SMG7 to trigger mRNA decay and to localize to decay bodies. Our findings indicate that SMG7 provides a link between the NMD and the mRNA degradation machinery by interacting with SMG5 and UPF1 via its N-terminal domain and targeting bound transcripts for decay via its C-terminal domain.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Blotting, Western
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Carbocyanines
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Carrier Proteins / physiology*
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Cytoplasm / metabolism
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Dactinomycin / pharmacology
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Frameshift Mutation
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Genes, Reporter
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HeLa Cells
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Humans
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Luciferases / metabolism
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Microscopy, Fluorescence
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Mutation
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Nucleic Acid Synthesis Inhibitors / pharmacology
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Plasmids
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Protein Structure, Tertiary
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RNA Helicases
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RNA Interference
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RNA, Messenger / genetics
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RNA, Messenger / metabolism*
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RNA, Small Interfering / metabolism
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Recombinant Fusion Proteins / metabolism
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Ribonucleoproteins, Small Nuclear / metabolism
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Templates, Genetic
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Time Factors
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Trans-Activators / metabolism
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Transfection
Substances
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Carbocyanines
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Carrier Proteins
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LSM4 protein, human
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Nucleic Acid Synthesis Inhibitors
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RNA, Messenger
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RNA, Small Interfering
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Recombinant Fusion Proteins
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Ribonucleoproteins, Small Nuclear
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SMG7 protein, human
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Trans-Activators
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cyanine dye 3
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Dactinomycin
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Luciferases
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RNA Helicases
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UPF1 protein, human