Nop5 interacts with the archaeal RNA exosome.
The archaeal exosome, a protein complex responsible for phosphorolytic degradation and tailing of RNA, has an RNA-binding platform containing Rrp4, Csl4, and DnaG. Aiming to detect novel interaction partners of the exosome, we copurified Nop5, which is a part of an rRNA methylating ribonucleoprotein complex, with the exosome of Sulfolobus solfataricus grown to a late stationary phase. We demonstrated the capability of Nop5 to bind to the exosome with a homotrimeric Rrp4-cap and to increase the proportion of polyadenylated RNAin vitro, suggesting that Nop5 is a dual-function protein. Since tailing of RNA probably serves to enhance RNA degradation, association of Nop5 with the archaeal exosome in the stationary phase may enhance tailing and degradation of RNA as survival strategy.