title: Crystal structure of Cex1p reveals the mechanism of tRNA trafficking between nucleus and cytoplasm.
abstract: In all eukaryotes, transcribed precursor tRNAs are maturated by processing and modification processes in nucleus and are transported to the cytoplasm. The cytoplasmic export protein (Cex1p) captures mature tRNAs from the nuclear export receptor (Los1p) on the cytoplasmic side of the nuclear pore complex, and it delivers them to eukaryotic elongation factor 1α. This conserved Cex1p function is essential for the quality control of mature tRNAs to ensure accurate translation. However, the structural basis of how Cex1p recognizes tRNAs and shuttles them to the translational apparatus remains unclear. Here, we solved the 2.2 Å resolution crystal structure of Saccharomyces cerevisiae Cex1p with C-terminal 197 disordered residues truncated. Cex1p adopts an elongated architecture, consisting of N-terminal kinase-like and a C-terminal α-helical HEAT repeat domains. Structure-based biochemical analyses suggested that Cex1p binds tRNAs on its inner side, using the positively charged HEAT repeat surface and the C-terminal disordered region. The N-terminal kinase-like domain acts as a scaffold to interact with the Ran-exportin (Los1p·Gsp1p) machinery. These results provide the structural basis of Los1p·Gsp1p·Cex1p·tRNA complex formation, thus clarifying the dynamic mechanism of tRNA shuttling from exportin to the translational apparatus.
authors: Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, 113-0032 Tokyo, Japan.
authors: Kayo
authors: K
authors: Nozawa
authors: Ryuichiro
authors: R
authors: Ishitani
authors: Tohru
authors: T
authors: Yoshihisa
authors: Mamoru
authors: M
authors: Sato
authors: Fumio
authors: F
authors: Arisaka
authors: Shuji
authors: S
authors: Kanamaru
authors: Naoshi
authors: N
authors: Dohmae
authors: Dev
authors: D
authors: Mangroo
authors: Bruno
authors: B
authors: Senger
authors: Hubert D
authors: HD
authors: Becker
authors: Osamu
authors: O
authors: Nureki
mesh_terms: D021581:Active Transport, Cell Nucleus; D002467:Cell Nucleus / Q000378:metabolism; D018360:Crystallography, X-Ray; D003593:Cytoplasm / Q000378:metabolism; D008958:Models, Molecular; D020559:Monomeric GTP-Binding Proteins / Q000378:metabolism; D028861:Nuclear Pore Complex Proteins / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D029543:Nucleocytoplasmic Transport Proteins / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D012343:RNA, Transfer / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000378:metabolism
chemical_list: C518290:Cex1 protein, S cerevisiae; C080324:GSP1 protein, S cerevisiae; C408090:Los1 protein, S cerevisiae; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; D012343:RNA, Transfer; D020559:Monomeric GTP-Binding Proteins
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