title: Scyl1 facilitates nuclear tRNA export in mammalian cells by acting at the nuclear pore complex.
abstract: Scyl1 is an evolutionarily conserved N-terminal protein kinase-like domain protein that plays a role in COP1-mediated retrograde protein trafficking in mammalian cells. Furthermore, loss of Scyl1 function has been shown to result in neurodegenerative disorders in mice. Here, we report that Scyl1 is also a cytoplasmic component of the mammalian nuclear tRNA export machinery. Like exportin-t, overexpression of Scyl1 restored export of a nuclear export-defective serine amber suppressor tRNA mutant in COS-7 cells. Scyl1 binds tRNA saturably, and associates with the nuclear pore complex by interacting, in part, with Nup98. Scyl1 copurifies with the nuclear tRNA export receptors exportin-t and exportin-5, the RanGTPase, and the eukaryotic elongation factor eEF-1A, which transports aminoacyl-tRNAs to the ribosomes. Scyl1 interacts directly with exportin-t and RanGTP but not with eEF-1A or RanGDP in vitro. Moreover, exportin-t containing tRNA, Scyl1, and RanGTP form a quaternary complex in vitro. Biochemical characterization also suggests that the nuclear aminoacylation-dependent pathway is primarily responsible for tRNA export in mammalian cells. These findings together suggest that Scyl1 participates in the nuclear aminoacylation-dependent tRNA export pathway and may unload aminoacyl-tRNAs from the nuclear tRNA export receptor at the cytoplasmic side of the nuclear pore complex and channels them to eEF-1A.
authors.affiliation: Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada.
authors.forename: Shawn C
authors.initials: SC
authors.lastname: Chafe
authors.forename: Dev
authors.initials: D
authors.lastname: Mangroo
mesh_terms: D021581:Active Transport, Cell Nucleus; D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D019556:COS Cells; D002457:Cell Extracts; D002522:Chlorocebus aethiops; D018389:Codon, Nonsense / Q000235:genetics; D004268:DNA-Binding Proteins; D055785:Gene Knockdown Techniques; D006367:HeLa Cells; D006801:Humans; D028884:Karyopherins / Q000378:metabolism; D022022:Nuclear Pore / Q000378:metabolism*; D028861:Nuclear Pore Complex Proteins / Q000378:metabolism; D020648:Peptide Elongation Factor 1 / Q000302:isolation & purification / Q000378:metabolism; D011485:Protein Binding; D012343:RNA, Transfer / Q000378:metabolism*; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D013489:Suppression, Genetic; D014157:Transcription Factors / Q000302:isolation & purification / Q000378:metabolism*; D046249:Transfer RNA Aminoacylation / Q000235:genetics; D020931:ran GTP-Binding Protein / Q000378:metabolism
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D002457:Cell Extracts; D018389:Codon, Nonsense; D004268:DNA-Binding Proteins; D028884:Karyopherins; D028861:Nuclear Pore Complex Proteins; D020648:Peptide Elongation Factor 1; D012346:RNA, Transfer, Amino Acyl; C464929:SCYL1 protein, human; D014157:Transcription Factors; C093350:nuclear pore complex protein 98; D012343:RNA, Transfer; D020931:ran GTP-Binding Protein