Dss1 (or Rpn15) is a recently identified subunit of the 26S proteasome. regulatory particle. In addition to its function in the protein degradation. machinery, it has been linked to BRCA2 (breast cancer susceptibility gene 2. product) and homologous DNA recombination, mRNA export, and exocytosis.. While the fungal orthologues of Dss1 are not essential for viability, the. significance of Dss1 in metazoans has remained unknown due to a lack of. knockout animal models. We have studied the deletion of
dss-1 in. Caenorhabditis elegans with a
dss-1 loss-of-function mutant and
dss-1. directed RNAi. The analysis revealed an essential role for
dss-1 in. oogenesis, with defects partially mimicking the oogenesis phenotype of the. BRCA2 homologue
brc-2 mutant worms.
dss-1 RNAi caused, in addition,. embryonic lethality and larval arrest, presumably due to loss of the
dss-1. mRNA maternal contribution. DSS-1::GFP fusion protein localised primarily. in the nucleus. No apparent effect on proteasome function was found in dss-. 1 RNAi treated worms. However, expression of the C. elegans
dss-1 in yeast. cells deleted for its orthologue SEM1 rescued their temperature-sensitive. growth phenotype, and mildly rescued the accumulation of polyubiquitinated. proteins in these cells. This study of the first knockout animal model for. DSS-1/Rpn15/Sem1 shows that in contrast to unicellular eukaryotes, the C.. elegans
dss-1 encodes an essential protein, which is required for. embryogenesis, larval growth, and oogenesis, and which is functionally. conserved with its yeast and human homologues.