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Proc Natl Acad Sci U S A. 2018 Oct 2;115(40):E9325-E9332. doi: 10.1073/pnas.1805782115. Epub 2018 Sep 17.

Targeted profiling of RNA translation reveals mTOR-4EBP1/2-independent translation regulation of mRNAs encoding ribosomal proteins.

Li BB1,2,3, Qian C1,2, Gameiro PA2, Liu CC1,2, Jiang T1,2, Roberts TM1,2, Struhl K4,3, Zhao JJ5,2,3.

Author information

1
Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215.
2
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115.
3
Broad Institute of MIT and Harvard, Cambridge, MA 02142.
4
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115; kevin@hms.harvard.edu jean_zhao@dfci.harvard.edu.
5
Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215; kevin@hms.harvard.edu jean_zhao@dfci.harvard.edu.

Abstract

The PI3K-Akt-mTOR signaling pathway is a master regulator of RNA translation. Pharmacological inhibition of this pathway preferentially and coordinately suppresses, in a 4EBP1/2-dependent manner, translation of mRNAs encoding ribosomal proteins. However, it is unclear whether mechanistic target of rapamycin (mTOR)-4EBP1/2 is the exclusive translation regulator of this group of genes, and furthermore, systematic searches for novel translation modulators have been immensely challenging because of difficulties in scaling existing RNA translation profiling assays. Here, we developed a rapid and highly scalable approach for gene-specific quantitation of RNA translation, termed Targeted Profiling of RNA Translation (TPRT). We applied this technique in a chemical screen for translation modulators, and identified numerous preclinical and clinical therapeutic compounds, with diverse nominal targets, that preferentially suppress translation of ribosomal proteins. Surprisingly, some of these compounds act in a manner that bypasses canonical regulation by mTOR-4EBP1/2. Instead, these compounds exert their translation effects in a manner that is dependent on GCN2-eIF2α, a central signaling axis within the integrated stress response. Furthermore, we were also able to identify metabolic perturbations that also suppress ribosomal protein translation in an mTOR-independent manner. Together, we describe a translation assay that is directly applicable to large-scale RNA translation studies, and that enabled us to identify a noncanonical, mTOR-independent mode for translation regulation of ribosomal proteins.

KEYWORDS:

GCN2-eIF2α; mTOR; ribosomal proteins; translation control; translation profiling

PMID:
30224479
PMCID:
PMC6176620
[Available on 2019-04-02]
DOI:
10.1073/pnas.1805782115
[Indexed for MEDLINE]

Conflict of interest statement

Conflict of interest statement: B.B.L. and J.J.Z. are coinventors on patent application PCT/US2017/039001. All other authors declare no conflict of interest.

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