The RNA processing exosome contains ribonucleases that degrade aberrant RNAs in archael and eukaryotic cells. In Saccharomyces cerevisiae, the nuclear/nucleolar 3-5 exoribonuclease Rrp6 distinguishes the nuclear exosome from the cytoplasmic exosome. In vivo the TRAMP complex enhances the ability of the nuclear exosome to destroy some aberrant RNAs. Previous reports showed that purified TRAMP enhanced RNA degradation by the nuclear exosome in vitro. However, the exoribonucleolytic component(s) of the nuclear exosome enhanced by TRAMP remain unidentified. We show that TRAMP does not significantly enhance RNA degradation by purified exosomes lacking Rrp6 in vitro, suggesting that TRAMP activation experiments with nuclear exosome preparations reflect, in part, effects on the activity of Rrp6. Consistent with this, we show that incubation of purified TRAMP with recombinant Rrp6 results in a ten-fold enhancement of the rate of RNA degradation. This increased activity results from enhancement of the hydrolytic activity of Rrp6, since TRAMP cannot enhance the activity of an Rrp6 mutant lacking a key amino acid side chain in its active site. We observed no ATP, or polyadenylation dependence for the enhancement of Rrp6 activity by TRAMP, suggesting that neither the poly(A) polymerase activity of Trf4, nor the helicase activity of Mtr4 play roles in the enhancement. These findings identify TRAMP as an exosome-independent enhancer of Rrp6 activity.
|Evidence ID||Analyze ID||Interactor||Interactor Systematic Name||Interactor||Interactor Systematic Name||Type||Assay||Annotation||Action||Modification||Phenotype||Source||Reference||Note|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Gene Ontology Term||Gene Ontology Term ID||Qualifier||Aspect||Method||Evidence||Source||Assigned On||Annotation Extension||Reference|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Phenotype||Experiment Type||Experiment Type Category||Mutant Information||Strain Background||Chemical||Details||Reference|
|Evidence ID||Analyze ID||Regulator||Regulator Systematic Name||Target||Target Systematic Name||Experiment||Assay||Construct||Conditions||Strain Background||Reference|