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Title: Role of the exosome co-factor Rrp47 in RNA processing and surveillance
Author: Feigenbutz, Monika U.
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2013
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RNA surveillance by the exosome complex is remarkably conserved from yeast to humans and best studied in baker's yeast Saccharomyces cerevisiae. The multi-subunit RNA exosome is involved in the processing, maturation, quality control and general turnover of RNAs, as well as the degradation of harmful, aberrant or unwanted transcripts. To execute its distinct cytoplasmic and nuclear functions, the exosome requires compartment-specific co-factors like Rrp47, a protein directly associated with the nuclear exosome exoribonuclease Rrp6. The aim of this study was to investigate the role of Rrp47 in exosome-mediated processes based on the model that Rrp47 is an RNA binding protein that helps direct Rrp6 to its substrates. Mutational analysis of Rrp47 revealed that the Sas10 domain which Rrp47 shares with other proteins involved in RNA processing is critical for Rrp6 binding and for all in vivo Rrp47 functions. However, the less conserved C-terminus of Rrp47 functions in the final maturation of snoRNAs, and both C- and N-terminus cooperate in RNA binding in vitro. Protein and mRNA expression analyses demonstrate that the proteins critically influence each other's stability and expression levels whereby Rrp47 expression is drastically reduced when Rrp6 is absent. Studies into the assembly of Rrp47-Rrp6 suggest that the proteins are imported into the nucleus separately where Rrp47 is degraded if Rrp6 is not available for interaction. Rrp47 has less pronounced effects on Rrp6 stability and expression, yet defects in the processing of Nrd1 terminated transcripts were alleviated by Rrp6 overexpression in cells lacking Rrp47. Specifically, growth was restored by overexpressing Rrp6 in an otherwise synthetic lethal rex1? rrp47? strain, suggesting that Rrp47 is critical for maintaining adequate Rrp6 levels. Taken together this study has given crucial new insights into domains required for Rrp47 function, as well as assembly and interdependency of Rrp47 and its associated exonuclease Rrp6.
Supervisor: Mitchell, Philip J. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available