Cell
Volume 106, Issue 5, 7 September 2001, Pages 607-617
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Article
Evidence for a Pioneer Round of mRNA Translation: mRNAs Subject to Nonsense-Mediated Decay in Mammalian Cells Are Bound by CBP80 and CBP20

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Abstract

Nonsense-mediated decay (NMD) eliminates mRNAs that prematurely terminate translation. We used antibody to the nuclear cap binding protein CBP80 or its cytoplasmic counterpart eIF4E to immunopurify RNP containing nonsense-free or nonsense-containing transcripts. Data indicate that NMD takes place in association with CBP80. We defined other components of NMD-susceptible mRNP as CBP20, PABP2, eIF4G, and the NMD factors Upf2 and Upf3. Consistent with the dependence of NMD on translation, the NMD of CBP80-bound mRNA is blocked by cycloheximide or suppressor tRNA. These findings provide evidence that translation can take place in association with CBP80. They also indicate that CBP80-bound mRNA undergoes a “pioneer” round of translation, before CBP80-CBP20 are replaced by eIF4E, and Upf2 and Upf3 proteins dissociate from upstream of exon-exon junctions.

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Present address: Division of Radiation Biology, Faculty of Pharmaceutical Science, Kanazawa University, Takana-machi 13-1, Kanazawa 920-0934 Japan.