Conceptually, export of most of nuclear RNA follows a similar mechanism to that described above for protein trafficking. This process also involves cargo receptors, export factors, and nucleoporins to deliver mature RNA to the cytoplasm, but in this case, structure and function of nuclear export signals are not well understood. Aminoacylated tRNAs are necessary in the cytoplasm for protein synthesis, but tRNAs are transcribed in the nucleus. tRNA export to the cytoplasm is mediated by exportin-t, which belongs to the karyopherin family. Exportin-t forms a complex together with RanGTP in the nucleus, and once the exportin-t-RanGTP-tRNA complex reaches the cytoplasm, RanGAP induces the hydrolysis of the Ran-associated GTP and the release of the tRNA [175, 176] . It has been proposed that exportin-5 could act as an auxiliary protein in this process [177] . However, later reports in yeast have opened the possibility of alternative pathways for tRNA nuclear export [163] .