Genetic alterations such as mutations, genomic rearrangements and aneuploidy, are commonly observed in tumors. To counteract this cells have multiple genome maintenance and surveillance systems to... Show moreGenetic alterations such as mutations, genomic rearrangements and aneuploidy, are commonly observed in tumors. To counteract this cells have multiple genome maintenance and surveillance systems to minimize the rate at which genomic alterations arise. The aim of the thesis is to gain understanding of processes and pathways that contribute to the maintenance of genome stability and to establish how defects in these processes and pathways abrogate the DNA damage response and consequently may promote genomic instability and development of cancer. The work described in this thesis addresses various aspects of the cellular response of mammalian cells to DNA damaging agents including changes in post translational modifications that occur after genotoxic stress. The role of poly-adenosyl ribose modification in nucleotide excision repair is investigated and found to be important for the recruitment of a chromatin remodeling protein and repair. Phosphoproteomic analysis identified changes in the global phosphorylation state of proteins following genotoxic stress. Key kinases responding to DNA damage are ATR and related kinases. A detailed study into the requirements for ATR activation after UV exposure indicates that at least two distinct modes of activation exist. Finally we describe the profound sensitivity of Cornelia de Lange Syndrome cells to DNA damage. Show less
The results presented in this thesis provide new information on the role of the p53.S389A point mutation in chemical-induced tumorigenesis. After DNA damage, p53 protein levels increase due to... Show moreThe results presented in this thesis provide new information on the role of the p53.S389A point mutation in chemical-induced tumorigenesis. After DNA damage, p53 protein levels increase due to several post-translational activation processes. Phosphorylation of p53.S389 seems to be partly required for optimal induction of these p53 protein levels. Next, target genes are either induced or repressed, and phosphorylation of p53.S389 seems essential for an optimal p53-related transcriptional response both endogenously (especially repressed genes) as well as after the induction of DNA damage. Than as a read-out system for the activation of different genes, several cellular responses (apoptosis, cell cycle arrest etc.) can be observed, which again seems partly dependent on p53.S389 phosphorylation. When these processes are adversely affected due to inadequate functioning of p53, like is the case in p53.S389A mutant mice, this might lead to increased risks of developing tumors. Indeed, two chronic carcinogenicity experiments revealed an increased sensitivity of the p53.S389A mutant mice for tumor development upon exposure to DNA damaging agents. In conclusion, knowledge about the in vivo relationship between DNA damage induction, regulation of p53 activity (in terms of cell cycle control and/or apoptosis), DNA repair (NER) and the development of cancer was obtained. Show less
