| The transport of macromolecules across the nuclear envelope requires soluble factors. The Saccharomyces cerevisiae rna1-1 mutant was found to have nuclear import defects both in vivo and in vitro. Addition of recombinant Rna1p to cytosol prepared from rna1-1 cells rescued the in vitro import defect in a dose-dependent manner, indicating that Rna1p is required for nuclear protein import. In addition, Rna1p stimulated GTP hydrolysis by the guanine-nucleotide binding protein Ran in vitro whereas the mutant Rna1-1p could not, suggesting that Rna1p functions as a GTPase activating protein in nuclear protein import.;To identify proteins that interact with Rna1p, a synthetic lethal screen with the rna1-1 mutant was performed. Two rsl (rna1 synthetic lethal) mutants were identified, both in the same complementation group. The complementing gene is essential for viability and encodes yeast importin-;Temperature-sensitive mutants of importin-;The HIV Vpr protein is required for the nuclear import of the HIV preintegration complex in non-dividing cells. In both yeast and human cells, Vpr localizes to the nuclear envelope in a manner similar to importin-... |
