AN RNA-EXPORT MEDIATOR WITH AN ESSENTIAL NUCLEAR EXPORT SIGNAL

THE Rev protein of human immunodeficiency virus type 1 (HIV-1) mediate s the translocation of viral messenger RNAs from the nucleus to the cy toplasm. In yeast, Rev can mediate the nuclear export of Rev response element containing RNAs(1). The export of Rev itself proceeds through the nuclear pore complex and requires a nuclear export signal (NES)(2, 3) and interaction with a cellular cofactor, the protein Rip1 (refs 1, 4, 5). Endogenous RNA export mediators that interact with Rip1 and ha rbour NESs are thought to exist(6,7) but have yet to be identified, He re we report the characterization of a new and essential yeast protein , Gle1, which contains an NES and has a relative molecular mass of 62, 000. Mutation of the NES in Gle1 prevents export of polyadenylated RNA from the nucleus. Gle1 interacts with Rip1 and the nucleo-porin Nup10 0 and is localized predominantly at nuclear pore complexes. These prop erties indicate that Gle1 is an RNA-export factor and that Rev may med iate viral RNA export by mimicking the function of Gle1.