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Nat Struct Mol Biol. 2004 Oct;11(10):992-1000. Epub 2004 Sep 7.

eIF4G is required for the pioneer round of translation in mammalian cells.

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  • 1Department of Biochemistry and Biophysics, School of Medicine and Dentistry, 601 Elmwood Avenue, Box 712, University of Rochester, Rochester, New York, 14642 USA.

Abstract

Nonsense-mediated mRNA decay (NMD) in mammalian cells targets cap-binding protein 80 (CBP80)-bound mRNA during or after a pioneer round of translation. It is unknown whether eukaryotic translation initiation factor 4G (eIF4G) functions in the pioneer round. We show that baculovirus-produced CBP80 and CBP20 independently interact with eIF4GI. The interactions between eIF4G and the heterodimer CBP80/20 suggest that eIF4G has a function in the pioneer initiation complex rather than merely a presence during remodeling to the steady-state complex. First, NMD is inhibited upon eIF4G cleavage by HIV-2 or poliovirus 2A protease. Second, eIF4GI coimmunopurifies with pre-mRNA, indicating that it associates with transcripts before the pioneer round. Third, eIF4G immunopurifies with Upf NMD factors and eIF4AIII, which are constituents of the pioneer translation initiation complex. We propose a model in which eIF4G serves to connect CBP80/20 with other initiation factors during the pioneer round of translation.

PMID:
15361857
[PubMed - indexed for MEDLINE]
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