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proteasome complex subunit DSS1/Sem1 The evolutionarily conserved deleted in split hand/split foot protein 1 (DSS1)/Sem1 is a subunit of the regulatory particle (RP) of the proteasome. It is implicated in ubiquitin-mediated proteolysis, is required for the maintenance of genomic stability, and functions in DNA damage response. DSS1/Sem1 also displays RP-independent functions; it serves as a functional component of the nuclear pore associated TREX-2 transcription-export complex and is required for proper nuclear export of mRNA. In mammalian cells, DSS1 binds and stabilizes the tumor suppressor BRCA2, and contributes to its function in mediating homologous recombinational repair. In yeast, Sem1 also complexes with the COP9 signalosome, which is involved in de-neddylation. DSS1/Sem1 may be a versatile protein which contributes to the functional integrity of multiple protein complexes involved in various biological processes.
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