title: Dual role of methionyl-tRNA synthetase in the regulation of translation and tumor suppressor activity of aminoacyl-tRNA synthetase-interacting multifunctional protein-3.
abstract: Mammalian methionyl-tRNA synthetase (MRS) plays an essential role in initiating translation by transferring Met to initiator tRNA (tRNA(i)(Met)). MRS also provides a cytosolic anchoring site for aminoacyl-tRNA synthetase-interacting multifunctional protein-3 (AIMP3)/p18, a potent tumor suppressor that is translocated to the nucleus for DNA repair upon DNA damage. However, the mechanism by which this enzyme mediates these two seemingly unrelated functions is unknown. Here we demonstrate that AIMP3 is released from MRS by UV irradiation-induced stress. Dissociation was induced by phosphorylation of MRS at Ser662 by general control nonrepressed-2 (GCN2) following UV irradiation. Substitution of Ser662 to Asp (S662D) induced a conformational change in MRS and significantly reduced its interaction with AIMP3. This mutant possessed significantly reduced MRS catalytic activity because of loss of tRNA(Met) binding, resulting in down-regulation of global translation. According to the Met incorporation assay using stable HeLa cells expressing MRS S662A or eukaryotic initiation factor-2 subunit-α (eIF2α) S51A, inactivation of GCN2-induced phosphorylation at eIF2α or MRS augmented the role of the other, suggesting a cross-talk between MRS and eIF2α for efficient translational inhibition. This work reveals a unique mode of regulation of global translation as mediated by aminoacyl-tRNA synthetase, specifically MRS, which we herein identified as a previously unidentified GCN2 substrate. In addition, our research suggests a dual role for MRS: (i) as a coregulator with eIF2α for GCN2-mediated translational inhibition; and (ii) as a coupler of translational inhibition and DNA repair following DNA damage by releasing bound tumor suppressor AIMP3 for its nuclear translocation.
authors: Medicinal Bioconvergence Research Center,  Seoul National University, Seoul 151-742,  Korea.
authors: Nam Hoon
authors: NH
authors: Kwon
authors: Taehee
authors: T
authors: Kang
authors: Jin Young
authors: JY
authors: Lee
authors: Hyo Hyun
authors: HH
authors: Kim
authors: Hye Rim
authors: HR
authors: Kim
authors: Jeena
authors: J
authors: Hong
authors: Young Sun
authors: YS
authors: Oh
authors: Jung Min
authors: JM
authors: Han
authors: Min Jeong
authors: MJ
authors: Ku
authors: Sang Yeol
authors: SY
authors: Lee
authors: Sunghoon
authors: S
authors: Kim
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000528:radiation effects; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D004249:DNA Damage; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism; D005786:Gene Expression Regulation; D045325:HCT116 Cells; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D008718:Methionine-tRNA Ligase / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008856:Microscopy, Fluorescence; D009154:Mutation; D010445:Peptide Elongation Factors / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000528:radiation effects; D011485:Protein Binding / Q000528:radiation effects; D014176:Protein Biosynthesis; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D034622:RNA Interference; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*; D014466:Ultraviolet Rays
chemical_list: C529799:EEF1E1 protein, human; D015852:Eukaryotic Initiation Factor-2; D010445:Peptide Elongation Factors; D025521:Tumor Suppressor Proteins; C529271:EIF2AK4 protein, human; D017346:Protein Serine-Threonine Kinases; D008718:Methionine-tRNA Ligase