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Genetic analyses of XLF and KU and their functional impacts on DNA-double strand break repair in human cells

Al-Emam, Ahmed Mohamed Ahmed (2011)
Ph.D. thesis, University of Birmingham.

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Restricted to Repository staff only until 31 December 2018.


XRCC4-like factor (XLF) is the most recently discovered core member of the nonhomologous end joining (NHEJ) machinery. XLF enhances ligation of DNA ends by DNA ligase IV (LIG4) and functionally interacts with KU70. Previous results showed that some polymorphic changes in LIG4 impact on the efficiency of double strand breaks (DSBs) repair. A random Caucasian population sample was screened for XLF polymorphic mutations with similar functional impact. This analysis identified two novel noncoding single nucleotide polymorphisms (SNPs). To address the regulation of XLF and KU70, the acetylation status of both proteins were analysed. It has been found that XLF undergoes acetylation both in vitro and in vivo and the acetylation sites were mapped in vitro by mass spectrometry. Preliminary analysis has indicated that XLF deacetylation might be histone-deacetylase (HDAC3) dependent. For KU70, it has been found that lysine residues K317, K331 and K338 are critical for NHEJ. Cells overexpressing aceto-mimicking or aceto-blocking mutants of these residues are radiosensitive and defective in DSBs repair (DSBR). This indicates that the dynamic regulation of the acetylation/deacetylation status of these residues is critical for DSBR in response to ionizing radiation. These findings establish the importance of non-histone repair protein acetylation in the regulation of NHEJ and define new possible therapeutic targets for cancer treatment.

Type of Work:Ph.D. thesis.
Supervisor(s):Kysela, Boris
School/Faculty:Colleges (2008 onwards) > College of Medical & Dental Sciences
Department:School of Clinicial and Experimental Medicine
Subjects:RB Pathology
Institution:University of Birmingham
ID Code:3110
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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