title: Reassessment of the role of TSC, mTORC1 and microRNAs in amino acids-meditated translational control of TOP mRNAs.
abstract: 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.
authors.affiliation: Department of Biochemistry and Molecular Biology, The Institute for Medical Research - Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem, Israel.
authors.forename: Ilona
authors.initials: I
authors.lastname: Patursky-Polischuk
authors.affiliation: Department of Biochemistry and Molecular Biology, The Institute for Medical Research - Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem, Israel.
authors.forename: Judith
authors.initials: J
authors.lastname: Kasir
authors.affiliation: Department of Biochemistry and Molecular Biology, The Institute for Medical Research - Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem, Israel.
authors.forename: Rachel
authors.initials: R
authors.lastname: Miloslavski
authors.affiliation: Department of Biochemistry and Molecular Biology, The Institute for Medical Research - Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem, Israel.
authors.forename: Zvi
authors.initials: Z
authors.lastname: Hayouka
authors.affiliation: Department of Biochemistry and Molecular Biology, The Institute for Medical Research - Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem, Israel.
authors.forename: Mirit
authors.initials: M
authors.lastname: Hausner-Hanochi
authors.affiliation: Department of Biochemistry and Molecular Biology, The Institute for Medical Research - Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem, Israel.
authors.forename: Miri
authors.initials: M
authors.lastname: Stolovich-Rain
authors.affiliation: Lautenberg Center for General and Tumor Immunology, The Institute for Medical Research - Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem, Israel.
authors.forename: Pinchas
authors.initials: P
authors.lastname: Tsukerman
authors.affiliation: Lautenberg Center for General and Tumor Immunology, The Institute for Medical Research - Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem, Israel.
authors.forename: Moshe
authors.initials: M
authors.lastname: Biton
authors.affiliation: Department of Cell Biology, University of Massachusetts Medical School, North Worcester, Massachusetts, United States of America.
authors.forename: Rajini
authors.initials: R
authors.lastname: Mudhasani
authors.affiliation: Department of Cell Biology, University of Massachusetts Medical School, North Worcester, Massachusetts, United States of America.
authors.forename: Stephen N
authors.initials: SN
authors.lastname: Jones
authors.affiliation: Department of Biochemistry and Molecular Biology, The Institute for Medical Research - Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem, Israel.
authors.forename: Oded
authors.initials: O
authors.lastname: Meyuhas
mesh_terms: D000596:Amino Acids / Q000235:genetics; D000818:Animals; D005786:Gene Expression Regulation; D006801:Humans; D000076222:Mechanistic Target of Rapamycin Complex 1; D000076225:Mechanistic Target of Rapamycin Complex 2; D051379:Mice; D018345:Mice, Knockout; D035683:MicroRNAs / Q000235:genetics*; D046912:Multiprotein Complexes / Q000235:genetics*; D010766:Phosphorylation; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics*; D058570:TOR Serine-Threonine Kinases / Q000235:genetics*; D000077004:Tuberous Sclerosis Complex 1 Protein; D025521:Tumor Suppressor Proteins / Q000235:genetics*
chemical_list: D000596:Amino Acids; D035683:MicroRNAs; D046912:Multiprotein Complexes; D012333:RNA, Messenger; C000624650:TSC1 protein, human; C000624651:Tsc1 protein, mouse; D000077004:Tuberous Sclerosis Complex 1 Protein; D025521:Tumor Suppressor Proteins; D000076222:Mechanistic Target of Rapamycin Complex 1; D000076225:Mechanistic Target of Rapamycin Complex 2; D058570:TOR Serine-Threonine Kinases