The role of exportin-t in selective nuclear export of mature tRNAs.
Exportin-t (Xpo-t) is a vertebrate nuclear export receptor for tRNAs that binds tRNA cooperatively with GTP-loaded Ran. Xpo-t antibodies are shown to efficiently block tRNA export from Xenopus oocyte nuclei suggesting that it is responsible for at least the majority of tRNA export in these cells. We examine the mechanism by which Xpo-t-RanGTP specifically exports mature tRNAs rather than other forms of nuclear RNA, including tRNA precursors. Chemical and enzymatic footprinting together with phosphate modification interference reveals an extensive interaction between the backbone of the TPsiC and acceptor arms of tRNAPhe and Xpo-t-RanGTP. Analysis of mutant or precursor tRNA forms demonstrates that, aside from these recognition elements, accurate 5' and 3' end-processing of tRNA affects Xpo-t-RanGTP interaction and nuclear export, while aminoacylation is not essential. Intron-containing, end-processed, pre-tRNAs can be bound by Xpo-t-RanGTP and are rapidly exported from the nucleus if Xpo-t is present in excess. These results suggest that at least two mechanisms are involved in discrimination of pre-tRNAs and mature tRNAs prior to nuclear export.
Arts
G J
GJ
European Molecular Biology Laboratory, Meyerhofstrasse 1, D-69117 Heidelberg, Germany.
Kuersten
S
S
Romby
P
P
Ehresmann
B
B
Mattaj
I W
IW
D000215:Acylation; D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D001665:Binding Sites; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000276:immunology / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D008958:Models, Molecular; D009687:Nuclear Proteins / Q000378:metabolism*; D009690:Nucleic Acid Conformation; D029543:Nucleocytoplasmic Transport Proteins; D011485:Protein Binding; D012322:RNA Precursors / Q000378:metabolism*; D012331:RNA, Fungal / Q000378:metabolism*; D012343:RNA, Transfer / Q000378:metabolism*; D012360:RNA, Transfer, Phe / Q000378:metabolism; D012441:Saccharomyces cerevisiae; D014981:Xenopus; D020931:ran GTP-Binding Protein
D000906:Antibodies; D002352:Carrier Proteins; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; D012322:RNA Precursors; D012331:RNA, Fungal; D012360:RNA, Transfer, Phe; D006160:Guanosine Triphosphate; D012343:RNA, Transfer; D020931:ran GTP-Binding Protein