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Adenovirus-specific translation by displacement of kinase Mnk1 from cap-initiation complex eIF4F
R Cuesta1, Q Xi, R J Schneider
1Department of Microbiology, New York University School of Medicine, 550 First Avenue, New York, NY 10016, USA.
Abstract:
Translation of cellular mRNAs involves formation of a cap-binding translation initiation complex known as eIF4F, containing phosphorylated cap-binding protein eIF4E, eIF4E kinase Mnk1, eIF4A, poly(A)-binding protein and eIF4G. Adenovirus is shown to prevent cellular translation by displacing Mnk1 from eIF4F, thereby blocking phosphorylation of eIF4E. Over expression of an eIF4E mutant that cannot be phosphorylated by Mnk1 impairs translation of cellular but not viral late mRNAs. Adenovirus 100k protein is shown to bind the C-terminus of eIF4G in vivo and in vitro, the same region bound by Mnk1. In vivo, 100k protein displaces Mnk1 from eIF4G during adenovirus infection, or in transfected cells. Purified 100k protein also evicts Mnk1 from isolated eIF4F complexes in vitro. A mutant adenovirus with a temperature-sensitive 100k protein that cannot inhibit cellular protein synthesis at restrictive temperature no longer blocks Mnk1 binding to eIF4G, or phosphorylation of eIF4E. We describe a mechanism whereby adenovirus selectively inhibits the translation of cellular but not viral mRNAs by displacement of Mnk1 from eIF4G and inhibition of eIF4E phosphorylation.
Insights
Adenovirus selectively inhibits cellular mRNA translation by displacing Mnk1 kinase from the eIF4F complex, preventing eIF4E phosphorylation. This mechanism allows viral protein synthesis to proceed during infection.
Area of Science:
- Molecular Biology
- Virology
- Biochemistry
Background:
- Cellular mRNA translation initiation relies on the eIF4F complex, which includes eIF4E, Mnk1, eIF4A, PABP, and eIF4G.
- Phosphorylation of eIF4E by Mnk1 is crucial for efficient cap-dependent translation.
- Viruses often manipulate host cell machinery to favor their own replication.
Purpose of the Study:
- To elucidate the mechanism by which adenovirus inhibits cellular translation.
- To investigate the role of the adenovirus 100k protein in this process.
- To understand how viral translation is selectively preserved.
Main Methods:
- In vivo and in vitro binding assays to study protein-protein interactions.
- Expression of wild-type and mutant eIF4E proteins.
- Use of a temperature-sensitive adenovirus mutant to assess protein function.
Main Results:
- Adenovirus infection displaces Mnk1 from the eIF4F complex, inhibiting eIF4E phosphorylation.
- The adenovirus 100k protein binds eIF4G, competing with Mnk1 binding.
- A temperature-sensitive 100k mutant fails to inhibit cellular translation at restrictive temperatures.
Conclusions:
- Adenovirus employs a specific mechanism to inhibit cellular mRNA translation.
- The 100k protein is key to displacing Mnk1 and blocking eIF4E phosphorylation.
- This selective inhibition ensures viral mRNA translation proceeds during infection.