THE YEAST NUCLEOPORIN RIP1P CONTRIBUTES TO MULTIPLE EXPORT PATHWAYS WITH NO ESSENTIAL ROLE FOR ITS FG-REPEAT REGION

The FG-repeat domain of the yeast Rip1 protein (Rip1p) was identified initially as a possible target for the nuclear export signal (NES) of the HIV-1 Rev protein in a yeast two-hybrid assay. Rip1p is inessentia l, associated with nuclear pore complexes, and structurally related to the FG-nucleoporin family of pore proteins. It contributes to HIV-1 R ev-mediated RNA export and is also important for the export of heat sh ock RNAs at 42 degrees C. We show here that Rip1p is essential for the export of heat shock RNAs, and this function is fulfilled by the uniq ue carboxyl terminus of Rip1p with no substantial contribution from th e FG-repeat region. Genetic interactions between Rip1p and the RNA exp ort mediator Gle1p are described, which support a role of the carboxyl terminus of Rip1p in poly(A)(+) RNA export. Finally, this domain of R ip1p also contributes to Rev-mediated RNA export. The data suggest tha t Rip1p promotes the nuclear export of different classes of substrates by contributing to optimal pore function.