E2F1 is a transcription factor which paradoxically has major influence on both apoptosis and cell cycle progression. One of the most important questions in E2F1 biology therefore is the mechanism underlying regulation of these opposing physiological outcomes. Post-translational modifications (PTM) provide proteins with an additional layer of complexity, potentially altering interactions with partner DNA and protein. The importance of arginine methylation has recently been implicated in modulating the activity of the tumour suppression pathway proteins, p53 and E2F1. Previous studies have established that the methyltransferase, PRMT5, is responsible for the symmetrical dimethylation of E2F1, which inhibits its pro-apoptotic activity. In this thesis, E2F1 was found to be a substrate of PRMT1, which catalysed asymmetrical dimethylation of E2F1 at arginine 109. In addition, a positive correlation was found between the percentage of apoptotic cells and levels of PRMT1. Conversely, an increase in cancer cell colony formation was shown when the site of PRMT1 methylation on E2F1 was changed from arginine to lysine at position 109. These findings suggested a growth inhibition effect by PRMT1 methylation on E2F1. At the transcriptional level, depletion of PRMT1 increased E2F1 binding to the promoter region of Cdc6, a cell cycle regulator, and decreased binding to the promoter region of Apaf1, which has a pro- apoptotic role. Genome-wide ChIP-sequencing technology was undertaken and results further clarified that the depletion of PRMT1 preferably enriched E2F1 binding to promoters of positive regulators of cell proliferation and promoters of the cell cycle. Collectively, the findings of this thesis suggested that the opposing roles E2F1 demonstrated in promoting both cell proliferation and apoptosis was due to different types of arginine methylation which trigger E2F1 binding to different promoters. Lastly, arginine methylation was shown to influence protein-protein interactions. PRMT5 induction resulted in the identification by mass spectrometry of β-catenin as an E2F1 interacting partner. As the Wnt/β-catenin signalling pathway is broadly recognised as having pro- cell proliferation activity, this finding is consistent with previous reports that suggest the oncogenic role PRMT5 methylation has on E2F1.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:644704 |
| Date | January 2014 |
| Creators | Lu, Yi-Chien |
| Contributors | La Thangue, Nick |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://ora.ox.ac.uk/objects/uuid:5e8cbf54-31d5-4b45-823c-52dbf82131d5 |
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