Autophagy is an evolutionarily conserved process that is important for the maintenance of cellular homeostasis and also genomic integrity. Autophagy is a self-digestive process that takes place in the cytoplasm, however recent studies by Eileen White and colleagues demonstrated that defective autophagy leads to accumulation of DNA damage in vitro and in vivo [1] [2]. This discovery leads to a question: whether there is increased DNA damage incidences or defective DNA damage repair in autophagy deficient cells. Autophagy and DNA damage are two important areas for cancer research. The aim of this project is to provide a better understanding of the role of autophagy plays in DNA damage and DNA damage response. The activation of Chk1 facilitates its degradation. The results presented in this project illustrate that autophagy deficient cells exhibit elevated proteasomal activities and autophagy inhibition leads to activation of Chk1. These combined factors contribute to increased degradation of Chk1 in autophagy deficient cells. This was manifested first as decreased phospho-Chk1 in response to DNA damage, later on when the loss of autophagy effect is more pronounced; decrease in total Chk1 protein level was observed. Chk1 is a crucial DNA damage response mediator that plays roles in cell cycle checkpoints and DNA damage repair. Cells without autophagy appear to have intact cell cycle checkpoints in response to starvation or DNA damaging agents; however they show deficiency in homologous recombination (HR) repair pathways. Autophagy deficient cells display increased spontaneous cell death and formation of micronuclei. Defective HR pathways in autophagy deficient cells lead to hyper-dependency on non-homologous end-joining (NHEJ) process. Since HR and NHEJ are the two main ways of repairing double strand breaks (DSB), it is not surprising that inhibition of NHEJ following DSB inducing agents in autophagy deficient cells results in persistence of damage lesions and increased cell death. 3 This project demonstrated that loss or inhibition of autophagy leads to defective DNA damage response pathways. We established that Chk1 is de-regulated in autophagy deficient cells and this has differential downstream effects on DNA damage response. These findings potentially provide a novel synthetic lethal strategy to selectively kill autophagy-deficient cells, which are implicated in a number of diseases including certain cancers.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:630969 |
| Date | January 2014 |
| Creators | Liu, Emma Yu |
| Publisher | University of Glasgow |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://theses.gla.ac.uk/5204/ |
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