DSS1/Sem1, a Multifunctional and Intrinsically Disordered Protein

DSS1/Sem1 is a versatile intrinsically disordered protein. Besides being a bona fide subunit of the 26S proteasome, DSS1 associates with other protein complexes, including BRCA2–RPA, involved in homologous recombination; the Csn12–Thp3 complex, involved in RNA splicing; the integrator, involved in transcription; and the TREX-2 complex, involved in nuclear export of mRNA and transcription elongation. As a subunit of the proteasome, DSS1 functions both in complex assembly and possibly as a ubiquitin receptor. Here, we summarise structural and functional aspects of DSS1/Sem1 with particular emphasis on its multifunctional and disordered properties. We suggest that DSS1/Sem1 can act as a polyanionic adhesive to prevent nonproductive interactions during construction of protein assemblies, uniquely employing different structures when associating with the diverse multisubunit complexes.

TrendsDss1 is a conserved, intrinsically disordered and multifunctional protein.Dss1 is a component of multiple structurally and functionally diverse protein complexes.While several disordered proteins have been shown to change shape depending on the binding partner, Dss1 adapts this capability as it associates with different multisubunit protein complexes.Dss1 molecular functions include targeting, complex assembly, stabilisation, and protection.Dss1 cellular functions include regulating proteasome assembly, ubiquitin binding, transcription, mRNA export, and DNA repair.