A MUTATION IN THE SCHIZOSACCHAROMYCES-POMBE RAE1 GENE CAUSES DEFECTS IN POLY(A)(+) RNA EXPORT AND IN THE CYTOSKELETON

A collection of fission yeast Schizosaccharomyces pombe conditional mutants was screened for defective nucleocytoplasmic transport of poly(A)(+) RNA by fluorescence in situ hybridization, We identified a temperature-sensitive mutant that accumulated poly(A)(+) RNA in the nucleus and have named it rae1-1, for ribonucleic acid export. All rae1-1 cells exhibit the defect in poly(A)(+) RNA export within 30 min following a shift to the nonpermissive temperature, In addition, in the rae1-1 mutant, actin and tubulin become disorganized, and cells undergo an irreversible cycle arrest, Results from experiments in which rae1-1 cells were arrested in various phases of the cell division cycle and then shifted to nonpermissive temperature suggest that cells are particularly vulnerable to loss of rae1 function during G(2)/M. However, the inability to export RNA from the nucleus to the cytoplasm was not limited to a particular phase of the cell division cycle, The rae1 gene was isolated by complementation and encodes a predicted protein of 352 amino acids with four beta-transducin/WD40 repeats.