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Title: Mutational analysis and function of the 18S rRNA synthesis factor Utp3/Sas10
Author: Hussien, Shler
ISNI:       0000 0004 6350 4484
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2017
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The transcription, modification, processing and assembly of the pre-rRNA into ribosomes requires more than 200 proteins and 79 small RNAs in yeast, and involves most of the transcriptional activity of a cell. A large complex termed the processome is responsible for early cleavage events that lead to 18S rRNA synthesis. The processome subunit Utp3 shares sequence homology with the C1D protein interaction domain of Rrp47. Two hybrid analyses suggest Utp3 interacts with multiple processome components, including the Utp6 and Utp21 components of the Utp-B complex, Mpp10 of the Mpp10 subcomplex and Utp25. Utp3 also interacts with U3 snoRNA. This project aimed to (i) determine the regions within Utp3 that are required for its function in vivo; (ii) to map the sites of interaction between Utp3 and the processome components Utp6, Utp21, and Utp25, and (iii) to analyse molecular contacts between Utp3 and the pre-rRNA and/or U3 snoRNA in growing yeast cells. Mutants lacking the central region of Utp3 (which includes the C1D domain) complemented a GAL::UTP3 but caused dissociation of Utp3 from 90S complexes. In contrast, deletion of either the N- or C-terminal regions did not complement the GAL::UTP3 and caused depletion of 18S rRNA. Pull-down reactions suggest that interactions between the C1D domain of Utp3 and the processome may be mediated, at least in part, through Utp25. In contrast, interactions with the Utp-B complex are dependent upon both the C1D and CTD domains. Crosslinking and cloning (CRAC) analyses of Utp3/RNA complexes reveals that Utp3 interacts with 35S pre-rRNA and U3 snoRNA directly in vivo. These interactions are probably mediated by the CTD domain, since this region of Utp3 can bind nucleic acids in vitro. The nature of the critical role of the Nterminal region of Utp3 remains unclear. Cumulatively, the data supports the model that Utp3 is involved in multiple protein-protein and protein-RNA interactions and provides a molecular platform for interactions within the processome complex.
Supervisor: Mitchell, Philip Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available