ANALYSIS OF NUCLEOCYTOPLASMIC TRANSPORT AND NUCLEAR-ENVELOPE STRUCTURE IN YEAST DISRUPTED FOR THE GENE ENCODING THE NUCLEAR-PORE PROTEIN NUP1P

Nup1p and Nsp1p are structurally related nuclear pore complex (NPC) pr oteins which contain many degenerate repeat sequences of the FSFG type in their central domains. To find out whether this similarity also re flects a functional overlap at the NPC, rye analyzed Delta nup1 cells in comparison to ts nsp1 cells for defects in nucleocytoplasmic transp ort. When the NUP1 gene was disrupted in two different laboratory yeas t strains, haploid Delta nup1 progeny was viable, showing that NUP1 is not essential for vegetative cell growth; Delta nup1 strains, however , exhibited a strongly reduced growth rate at 37 degrees C as compared to 23 degrees C. When analyzed by thin section electron microscopy, D elta nup1 cells show a normal nuclear envelope morphology and the numb er and appearance of nuclear pore complexes apparently was not altered . Whereas Delta nup1 cells grown at 37 degrees C could still accumulat e a lacZ reporter protein carrying a nuclear localization sequence (NL S) inside the nucleus, poly(A)(+) RNA export was significantly inhibit ed. Our data suggest that Nup1p which is not physically associated wit h Nsp1p, is required for efficient nucleocytoplasmic transport reactio ns.