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 mu tants was screened for defective nucleocytoplasmic transport of poly(A )(+) RNA by fluorescence in situ hybridization, We identified a temper ature-sensitive mutant that accumulated poly(A)(+) RNA in the nucleus and have named it rae1-1, for ribonucleic acid export. All rae1-1 cell s exhibit the defect in poly(A)(+) RNA export within 30 min following a shift to the nonpermissive temperature, In addition, in the rae1-1 m utant, actin and tubulin become disorganized, and cells undergo an irr eversible cycle arrest, Results from experiments in which rae1-1 cells were arrested in various phases of the cell division cycle and then s hifted to nonpermissive temperature suggest that cells are particularl y vulnerable to loss of rae1 function during G(2)/M. However, the inab ility 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 is olated by complementation and encodes a predicted protein of 352 amino acids with four beta-transducin/WD40 repeats.