title: Degradation of initiator tRNAMet by Xrn1/2 via its accumulation in the nucleus of heat-treated HeLa cells.
abstract: Stress response mechanisms that modulate the dynamics of tRNA degradation and accumulation from the cytoplasm to the nucleus have been studied in yeast, the rat hepatoma and human cells. In the current study, we investigated tRNA degradation and accumulation in HeLa cells under various forms of stress. We found that initiator tRNA(Met) (tRNA(iMet)) was specifically degraded under heat stress. Two exonucleases, Xrn1 and Xrn2, are involved in the degradation of tRNA(iMet) in the cytoplasm and the nucleus, respectively. In addition to degradation, we observed accumulation of tRNA(iMet) in the nucleus. We also found that the mammalian target of rapamycin (mTOR), which regulates tRNA trafficking in yeast, is partially phosphorylated at Ser2448 in the presence of rapamycin and/or during heat stress. Our results suggest phosphorylation of mTOR may correlate with accumulation of tRNA(iMet) in heat-treated HeLa cells.
authors.affiliation: Radioisotope Center, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan. watanabe@ric.u-tokyo.ac.jp
authors.forename: Kazunori
authors.initials: K
authors.lastname: Watanabe
authors.forename: Ryu
authors.initials: R
authors.lastname: Miyagawa
authors.forename: Chie
authors.initials: C
authors.lastname: Tomikawa
authors.forename: Rie
authors.initials: R
authors.lastname: Mizuno
authors.forename: Akihisa
authors.initials: A
authors.lastname: Takahashi
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Hori
authors.forename: Kenichi
authors.initials: K
authors.lastname: Ijiri
mesh_terms: D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism*; D005095:Exoribonucleases / Q000378:metabolism*; D006367:HeLa Cells; D006358:Hot Temperature; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D012358:RNA, Transfer, Met / Q000737:chemistry / Q000378:metabolism*; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism
chemical_list: D008869:Microtubule-Associated Proteins; D012358:RNA, Transfer, Met; D058570:TOR Serine-Threonine Kinases; D005095:Exoribonucleases; C470512:XRN1 protein, human; C120903:XRN2 protein, human