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Title: DEAH-box helicase Prp43p and its co-factors
Author: Auchynnikava, Tatsiana
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2008
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Prp43p is a DEAH-box RNA helicase that participates in both splicing and ribosomal RNA (rRNA) processing in Saccharomyces cerevisiae.  In splicing, Prp43p was implicated in spliceosome disassembly. New splicing factor Spp382p was shown to interact with Prp43p in yeast two-hybrid screen. Additionally, Spp382p was confirmed to be a part of the post-splicing complex. Spp382p stimulates RNA unwinding activity of Prp43p in vitro. In this thesis I show that Ntr2p is also associated with the post-splicing complex. Ntr2p, like Spp382p, co-precipitates U2, U5 and U6 snRNAs and excised intron from in vitro splicing reactions. Spp382p and Ntr2p co-sediment in glycerol gradients, which suggests that they are part of the same protein sub-complex(es). Depletion of Spp382p does not affect the association of Ntr2p with the spliceosome. This suggests that Ntr2p has other uncharacterized interactions within the spliceosome. In contrast, depletion of Spp382p affects stable association of Prp43p with the post-splicing complex, which can be reconstituted upon addition of Spp382p to the in vitro splicing reaction. Mutants of Prp43p showed increased U6 snRNA co-precipitation, indicating that these mutants affect release of U6 snRNA from the post-splicing complex. I provide evidence that the C-terminal of Prp43p might regulate its ATPase activity, possibly via interaction with Spp382p. I show that Spp382p, but not Ntr2p, is associated with pre-rRNA precursors, which indicates function for Spp382p in pre-rRNA processing. In the absence of Spp382p, Prop43p accumulates in pre-rRNA particles as do ATPase deficient mutants of Prp43p. This finding suggests that the presence of Spp382p is necessary for the release of Prp43p from pre-ribosomes, and/or for stimulation of ATPase activity of Prp43p in pre-rRNA processing. Prp43p requires Spp382p for stable association with the spliceosome, whereas in pre-rRNA processing, Spp382p (or the G-patch domain of Spp382p only) serves as a release factor for Prp43p. This suggests that these proteins form a complex with dual functions.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available