Assays of the helicase, ATPase, and exoribonuclease activities of the yeast mitochondrial degradosome.

The mitochondrial degradosome (mtEXO) is the main enzymatic complex in RNA degradation, processing, and surveillance in Saccharomyces cerevisiae mitochondria. It consists of two nuclear-encoded subunits: the ATP-dependent RNA helicase Suv3p and the 3' to 5' exoribonuclease Dss1p. The two subunits depend on each other for their activity; the complex can therefore be considered as a model system for the cooperation of RNA helicases and exoribonucleases in RNA degradation. All the three activities of the complex (helicase, ATPase, and exoribonuclease) can be studied in vitro using recombinant proteins and protocols presented in this chapter.