Export and transport of tRNA are coupled to a multi-protein complex

Vigilin is a ubiquitous multi heterogeneous nuclear ribonucleoprotein (hnRN P) K homologous (KH)-domain protein. Here we demonstrate that purified reco mbinant human vigilin binds tRNA molecules with high affinity, although wit h limited specificity. Nuclear microinjection experiments revealed for the first time that the immuno-affinity-purified nuclear vigilin core complex ( VCCN) as well as recombinant vigilin accelerate tRNA export from the nucleu s in human cells. The nuclear tRNA receptor exportin-t is part of the VCCN. Elongation factor (EF)Icc. is enriched in VCCN and its cytoplasmic counter part VCCC, whereas EF-1 beta, EF-1 gamma and EF-1 delta are basically confi ned to the VCCC. Our results suggest further that vigilin and exportin-t mi ght interact during tRNA export, provide evidence that the channeled tRNA c ycle is already initiated in the nucleus, and illustrate that intracellular tRNA trafficking is associated with discrete changes in the composition of cellular cytoplasmic multiprotein complexes containing tRNA.