Structural characterization of yeast exosome using SAXS

The exosome is a large protein complex conserved in all eukaryotes that possesses 3’-5’ exoribonuclease activity [1]. It is playing a major role in RNA turnover and surveillance as well as processing of stable RNA species [2,3,1,4,5]. The exosome is composed of six distinct subunits homologous to the catalytic domains of ring shaped phosphorolytic bacterial RNase PH and PNPase (Rrp41, Rrp42, Rrp43, Rrp45, Rrp46, Mtr3), three subunits (Rrp40, Rrp4 and Csl4) with RNA binding motifs homologous to PNPase RNA binding domain and one large subunit (Dis3 / Rrp44) belonging to the RNase R family of hydrolytic RNases [6]. In addition nuclear form of exosome contains two additional subunits (Rrp6, Rrp47). The former one, Rrp6, belongs to the RNase D family of RNases. In cytoplasm the exosome contains instead the Ski7 factor that has homology to translation elongation factor (TEF) family of GTPases. It is believed that different exosome substrates are recruited by different exosome RNA binding domains and/or exosome associated proteins.