Reassessment of the role of TSC, mTORC1 and microRNAs in amino acids-meditated translational control of TOP mRNAs

• Published in: PloS one Vol. 9; no. 10; p. e109410
• Main Authors: Patursky-Polischuk, Ilona, Kasir, Judith, Miloslavski, Rachel, Hayouka, Zvi, Hausner-Hanochi, Mirit, Stolovich-Rain, Miri, Tsukerman, Pinchas, Biton, Moshe, Mudhasani, Rajini, Jones, Stephen N, Meyuhas, Oded
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 22.10.2014; Public Library of Science (PLoS)
• Subjects: Activation; Active control; Amino acids; Amino Acids - genetics; Animals; Biochemistry; Biology and life sciences; Biosynthesis; Control; Deprivation; Efficiency; Gene expression; Gene Expression Regulation; Humans; Immunology; Kinases; Machinery and equipment; Mechanistic Target of Rapamycin Complex 1; Mechanistic Target of Rapamycin Complex 2; Medical research; Medical schools; Messenger RNA; Mice; Mice, Knockout; MicroRNA; MicroRNAs; MicroRNAs - genetics; miRNA; Molecular biology; mRNA; Multiprotein Complexes - genetics; Pharmacology; Phosphorylation; Protein Biosynthesis; Protein synthesis; Proteins; Ribonucleic acid; RNA; RNA, Messenger - genetics; Signal Transduction - genetics; Signaling; Titration; TOR protein; TOR Serine-Threonine Kinases - genetics; Translation; Translation (Genetics); Tuberous Sclerosis Complex 1; Tuberous Sclerosis Complex 2; Tumor Suppressor Proteins - genetics; Canada; Israel; Jerusalem Israel; United States > US; Massachusetts
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0109410

TOP mRNAs encode components of the translational apparatus, and repression of their translation comprises one mechanism, by which cells encountering amino acid deprivation downregulate the biosynthesis of the protein synthesis machinery. This mode of regulation involves TSC as knockout of TSC1 or TSC2 rescued TOP mRNAs translation in amino acid-starved cells. The involvement of mTOR in translational control of TOP mRNAs is demonstrated by the ability of constitutively active mTOR to relieve the translational repression of TOP mRNA upon amino acid deprivation. Consistently, knockdown of this kinase as well as its inhibition by pharmacological means blocked amino acid-induced translational activation of these mRNAs. The signaling of amino acids to TOP mRNAs involves RagB, as overexpression of active RagB derepressed the translation of these mRNAs in amino acid-starved cells. Nonetheless, knockdown of raptor or rictor failed to suppress translational activation of TOP mRNAs by amino acids, suggesting that mTORC1 or mTORC2 plays a minor, if any, role in this mode of regulation. Finally, miR10a has previously been suggested to positively regulate the translation of TOP mRNAs. However, we show here that titration of this microRNA failed to downregulate the basal translation efficiency of TOP mRNAs. Moreover, Drosha knockdown or Dicer knockout, which carries out the first and second processing steps in microRNAs biosynthesis, respectively, failed to block the translational activation of TOP mRNAs by amino acid or serum stimulation. Evidently, these results are questioning the positive role of microRNAs in this mode of regulation.