An RNA-export mediator with an essential nuclear export signal

Abstract

THE Rev protein of human immunodeficiency virus type 1 (HIV-1) mediates the translocation of viral messenger RNAs from the nucleus to the cytoplasm. In yeast, Rev can mediate the nuclear export of Rev response-element-containing RNAs¹. 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 Ripl (refs 1,4,5). Endogenous RNA export mediators that interact with Ripl and harbour NESs are thought to exist^6,7 but have yet to be identified. Here we report the characterization of a new and essential yeast protein, Glel, which contains an NES and has a relative molecular mass of 62,000. Mutation of the NES in Glel prevents export of polyadenylated RNA from the nucleus. Glel interacts with Ripl and the nucleoporin Nup100 and is localized predominantly at nuclear pore complexes. These properties indicate that Glel is an RNA-export factor and that Rev may mediate viral RNA export by mimicking the function of Glel.