Cancer is caused by an accumulation of mutations (formed when cells attempt to replicate damaged DNA) that lead to unchecked cell growth and proliferation. The first chapter of this thesis gives an... Show moreCancer is caused by an accumulation of mutations (formed when cells attempt to replicate damaged DNA) that lead to unchecked cell growth and proliferation. The first chapter of this thesis gives an overview of the major DNA-damaging agents and the opposing repair pathways, subsequently nucleotide excision repair (NER), able to repair a wide range of damages, is discussed. The second chapter thoroughly discusses the assembly of the NER complex, subsequent incision and repair synthesis. The recently elucidated regulation of NER is also discussed in detail whereas DNA-damage induced signalling is discussed briefly. Perspectives in respect to NER related research are discussed in the third chapter. Chapter four concerns the regulation of NER, preventing dual incision when gaps, formed by previously excised damages, cannot be filled. Chapter five and six concern the recruitment and activity of replication factors after dual incision. Finally, chapter seven describes UV-damage mediated incision and signalling in NER deficient cells. The main focus of this thesis is the sequence of events following dual incision, as much was known about the steps leading to incision yet little was known about the handover from pre- to post-incision complexes, the recruitment of post-incision factors and how they function in NER Show less
DNA is continuously exposed to exogenous and genotoxic insults including ionizing and ultraviolet radiation as well as chemical agents. DNA damage can compromise the integrity of the genome and... Show moreDNA is continuously exposed to exogenous and genotoxic insults including ionizing and ultraviolet radiation as well as chemical agents. DNA damage can compromise the integrity of the genome and have potentially deleterious effects. Ultraviolet light (UV) can induce the formation of helix distorting lesions such as 6-4 photoproducts (6-4PP) and cyclopyrimidine dimers (CPD). In humans, the nucleotide excision repair (NER) pathway is solely responsible for the repair of these lesions. A defect in NER can lead to extreme sun sensitivity and an elevated risk of developing skin cancer as observed in patients with the inherited disorder xeroderma pigmentosum. The work described in this thesis focuses on NER in human cells. Findings include: 1) UV-DDB stimulates the repair of photolesions, 2) UV-DDB binds to UV lesions independently of XPC suggesting it may have a role in chromatin priming, 3) the sealing of DNA nicks during NER are entirely on XRCC1-DNA ligase III_ complex in quiescent cells, 4) RPA couples NER mediated incision to DNA repair synthesis and ligation, 5) Arsenic induces its co-carcinogenic effects at least in part by disrupting the sealing of DNA nicks that arise during NER. Show less
