Cell cycle events are the basis of cell duplication and division. Control of the cell cycle involves various mechanisms, which appear conserved throughout eukaryotic evolution. Among them, transcription plays a major part. Studies on gene expression in two yeast model organisms, Schizosaccharomyces pombe and Saccharomyces cerevisiae. Identified waves of transcription through the cell cycle, which require specific transcription factor complexes binding to promoter sequences. These periodic expression patterns are clustered corresponding to the four main cell cycle transitions, suggesting that their serial regulation is interdependent. Cytokinesis occurs at the end of the cell cycle, and includes formation of the actomyosin ring, synthesis of a membrane barrier and the eventual splitting of mother- daughter cells. In S. pombe, genes that are transcriptionally regulated during the M/G1 transition encode many of the components required for cytokinesis. Previously, we identified a transcription factor complex, which we named the PBF, and a promoter motif, the PCB, that together control M/G1 gene expression in S. pombe. In this thesis, we provide evidence for three transcription factors, Fkh2p, Sep1p and Mbx1p, as components of PBF and describe the isolation a Fkh2p-interacting protein, which we named Lyn1p. We also show that Fkh2p and Mbx1p are both hosphoproteins and present data that a polo-like kinase, Plo1p, phosphorylates Mbx1p In vitro. Furthermore, we show that Plo1p controls M/G1 gene expression, and is itself regulated by the PBF-PCB complex. Recent reports identified a glycolytic enzyme, Tdh1p, as a component of the Mediator complex, which bridges the transcription activating proteins to the RNA polymerase II (RNAP II) machinery that controls RNA production. Here, we present evidence that Sep1p interacts with Tdh1p, therefore suggesting a mechanism by which PBF regulates M/G1- specific gene expression, through direct interaction with the RNAP II machinery. In summary, we have characterised the molecular mechanism that controls M/G1 transcription in S. pombe. This involves Plo1p phosphorylating and controlling the PBF transcription factor complex, which in turn interacts with RNAP II machinery to control specific gene expression, and eventually cytokinesis and cell separation.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:425120 |
| Date | January 2006 |
| Creators | Ng, Szu Shien |
| Publisher | University of Glasgow |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://theses.gla.ac.uk/39023/ |
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