Figure 7.

Multiple cellular factors are involved in nuclear export. eIF-5A is required for nuclear export mediated by the leucine-rich NES of the HIV-1 Rev and HTLV-I Rex trans-activator proteins, but not for nucleocytoplasmic translocation mediated by the PKI NES. CRM1/exportin 1 is a general export receptor that mediates together with RanGTP the translocation of all export cargoes containing leucine-rich NESs through the NPC. The data presented in this work suggest that eIF-5A either acts before CRM1/exportin 1 in the nuclear export of specific export substrates or, alternatively, forms a complex with the respective NES and CRM1/exportin 1 (for details, see text).