Sporulation in Saccharomyces cerevisiae includes the processes of meiosis and spore formation. The genes involved in this developmental process are tightly regulated at the level of transcription to ensure that genes are expressed at the correct time and level. The co-ordinated expression of middle sporulation genes is mediated by a key timing promoter element called the middle sporulation element (MSE). While this element sets the timing of gene expression to middle sporulation, in some cases, the level of expression is mediated by cis-acting auxiliary promoter elements. This study has addressed the role that auxiliary transcription factors play in fine-tuning of timing and level of expression of the MSE-regulated middle sporulation genes SPS18 and SPS19 and the mid-late sporulation genes DIT1 and DIT2. The MSE*SPS18/19 was shown previously to set the timing of expression of SPS18 and SPS19 to middle sporulation. In order to achieve the full level of meiotic activation, a novel bipartite auxiliary promoter element called the MAE (MSE-associated element) was required (Dalton, 2004). This study has revealed that proteins bind to specific regions of the MAE motif during sporulation in vitro and has attempted to isolate the proteins by affinity chromatography and identify them by mass spectrometry. The timing of expression of DIT1 and DIT2 during sporulation was of particular interest since two MSE-like elements had been identified in the promoter of the these genes (Hepworth et al., 1995). If these MSEs were functional, it was thought that auxiliary elements may delay expression of these genes until mid-late sporulation. This study has shown that the MSE*NRE confers a normal middle sporulation pattern of expression on a reporter gene. The DRE (DIT repressor element) previously identified by Bogengruber et al. (1998) was further characterised as an element that alters the level of expression conferred by an MSE without altering the timing. Several proteins were shown to bind to specific regions of the DIT promoter surrounding the DRE motif in vitro, with a different set of proteins binding during vegetative growth and sporulation. Attempts to isolate and identify these proteins by affinity chromatography and mass spectrometry are discussed.
| Identifer | oai:union.ndltd.org:ADTP/187943 |
| Date | January 2005 |
| Creators | Lenardon, Megan Denise, Biotechnology & Biomolecular Sciences, Faculty of Science, UNSW |
| Publisher | Awarded by:University of New South Wales. Biotechnology and Biomolecular Sciences |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Copyright Megan Denise Lenardon, http://unsworks.unsw.edu.au/copyright |
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