Dynamic refolding of IFN-γ mRNA enables it to function as PKR activator and translation template

Smadar Cohen-Chalamish, Anat Hasson, Dahlia Weinberg, Lise Sarah Namer, Yona Banai, Farhat Osman, Raymond Kaempfer

Research output: Contribution to journalArticlepeer-review

66 Scopus citations

Abstract

Interferon-γ mRNA activates the RNA-dependent protein kinase PKR, which in turn strongly attenuates translation of interferon-γ mRNA. Unlike riboswitches restricted to noncoding regions, the interferon-γ RNA domain that activates PKR comprises the 5′ UTR and 26 translated codons. Extensive interferon-γ coding sequence is thus dedicated to activating PKR and blocking interferon-γ synthesis. This implies that the PKR activator is disrupted by ribosomes during translation initiation and must refold promptly to restore PKR activation. The activator structure harbors an essential kink-turn, probably to allow formation of a pseudoknot that is critical for PKR activation. Three indispensable short helices, bordered by orientation-sensitive base pairs, align with the pseudoknot stem, generating RNA helix of sufficient length to activate PKR. Through gain-of-function mutations, we show that the RNA activator can adopt alternative conformations that activate PKR. This flexibility promotes efficient refolding of interferon-γ mRNA, which is necessary for its dual function as translation template and activator of PKR, and which thus prevents overexpression of this inflammatory cytokine.

Original languageEnglish
Pages (from-to)896-903
Number of pages8
JournalNature Chemical Biology
Volume5
Issue number12
DOIs
StatePublished - Dec 2009
Externally publishedYes

Bibliographical note

Funding Information:
We thank E. Westhof for valuable suggestions and V. Bafna for bioinformatic analysis of the rodent IFN-γ genes. We thank A. Billiau (Catholic University of Leuven) for porcine IFN-γ cDNA. This work was supported by grants from the Israel Science Foundation and the German Research Foundation (DFG).

Funding

We thank E. Westhof for valuable suggestions and V. Bafna for bioinformatic analysis of the rodent IFN-γ genes. We thank A. Billiau (Catholic University of Leuven) for porcine IFN-γ cDNA. This work was supported by grants from the Israel Science Foundation and the German Research Foundation (DFG).

FundersFunder number
Deutsche Forschungsgemeinschaft
Israel Science Foundation

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