mTORC1 Balances Cellular Amino Acid Supply with Demand for Protein Synthesis through Post-transcriptional Control of ATF4

• Published in: Cell reports (Cambridge) 2017-05, Vol.19 (6), p.1083-1090
• Main Authors: Park, Yeonwoo, Reyna-Neyra, Andrea, Philippe, Lucas, Thoreen, Carson C.
• Format: Article
• Language: English
• Subjects: 5' Untranslated Regions; Activating Transcription Factor 4 - genetics; Activating Transcription Factor 4 - metabolism; Amino Acid Transport Systems - metabolism; amino acid uptake; Animals; ATF4; Eukaryotic Initiation Factor-2 - metabolism; HEK293 Cells; Humans; Mechanistic Target of Rapamycin Complex 1 - metabolism; Mice; mTOR; mTORC1; Open Reading Frames; RNA Processing, Post-Transcriptional; RNA Stability; RNA, Messenger - genetics; RNA, Messenger - metabolism
• ISSN: 2211-1247; 2211-1247
• DOI: 10.1016/j.celrep.2017.04.042

The mammalian target of rapamycin complex 1 (mTORC1) is a master regulator of cell growth that is commonly deregulated in human diseases. Here we find that mTORC1 controls a transcriptional program encoding amino acid transporters and metabolic enzymes through a mechanism also used to regulate protein synthesis. Bioinformatic analysis of mTORC1-responsive mRNAs identified a promoter element recognized by activating transcription factor 4 (ATF4), a key effector of the integrated stress response. ATF4 translation is normally induced by the phosphorylation of eukaryotic initiation factor 2 alpha (eIF2α) through a mechanism that requires upstream open reading frames (uORFs) in the ATF4 5′ UTR. mTORC1 also controls ATF4 translation through uORFs, but independently of changes in eIF2α phosphorylation. mTORC1 instead employs the 4E-binding protein (4E-BP) family of translation repressors. These results link mTORC1-regulated demand for protein synthesis with an ATF4-regulated transcriptional program that controls the supply of amino acids to the translation machinery. [Display omitted] •mTORC1 transcriptionally regulates amino acid transporters and enzymes via ATF4•mTORC1 controls ATF4 by regulating the translation and stability of its mRNA•Control of ATF4 translation requires uORFs, but not changes in eIF2α phosphorylation•mTORC1 control of ATF4 translation instead employs the 4E-BP translation repressors Park et al. show that mTORC1 transcriptionally regulates amino acid transporters, metabolic enzymes, and aminoacyl-tRNA synthetases. This program is mediated through post-transcriptional control of the ATF4 transcription factor. Regulation of ATF4 translation still requires upstream ORFs, but it is independent of eIF2α phosphorylation. mTORC1 instead employs the 4E-BP translation repressors.