Dss1 associating with the proteasome functions in selective nuclear mRNA export in yeast

Dss1p is an evolutionarily conserved small protein that interacts with BRCA2, a tumor suppressor protein, in humans. The Schizosaccharomyces pombe strain lacking the dss1(+) gene (Delta dss1) shows a temperature-sensitive growth defect and accumulation of bulk poly(A)(divided by) RNA in the nucleus at a nonpermissive temperature. In situ hybridization using probes for several specific mRNAs, however, revealed that the analyzed mRNAs were exported normally to the cytoplasm in Delta dss1, suggesting that Dss1p is required for export of some subsets of mRNAs. We identified the pud1(+) gene, which encodes a component of the 26S proteasome, as a suppressor for the ts(-) phenotype of Delta dss1. Unexpectedly, overexpression of Pad1p could suppress neither the defect in nuclear mRNA export nor a defect in proteasome function. In addition, loss of proteasome functions does not cause defective nuclear mRNA export. Dss1p seems to be a multifunctional protein involved in nuclear export of specific sets of mRNAs and the ubiquitin-proteasome pathway in fission yeast. (c) 2007 Elsevier Inc. All rights reserved.