The DNA of all living organisms is persistently damaged and requires continuous surveillance and repair. Unrepaired damage can lead to cancer and degenerative diseases. Most of the work published by our laboratory and others has focused upon DNA damage and repair in duplex DNA. However, many regions of human chromosomes assume unusual structures (non B-form) under physiological conditions as a consequence of their primary DNA sequence, and these structures likely contribute to the biological function of these regions. Currently, very little is known about the structural consequences of damage in these regions and how the damage is repaired. The focus of this renewal application will be on structural and potential biological consequences of DNA damage and repair in unusual DNA structures in human telomeric sequences. The ends of all human telomeres contain a repeating sequence, 5'TTAGGG, that is duplex for several thousand bases and ends with the G-rich strand for several hundred bases. Multiple structures, including loops and G-quadruplex structures form under physiological conditions, and these unusual structures interact with several proteins, forming the "shelterin" complex. The DNA within these regions must be able to dynamically form unusual structures to protect the ends of the chromosomes from enzymatic degradation and illegitimate chromosome fusions, but the DNA structures must also be disassembled for chromosome replication and telomere maintenance. Our preliminary data, in conjunction with published studies, indicate that some forms of DNA damage prevent the formation or relaxation of important unusual structures, and in some cases prevent the binding of critical binding proteins. Furthermore, we have observed that damaged bases within telomeric structures can create significant challenges for the base excision repair pathway. Failure to maintain telomeres can lead to telomere erosion and cellular senescence, chromosome translocations, and other potentially catastrophic biochemical events. In the four aims of this renewal application we propose to examine: 1) the impact of endogenous lesions on the capacity of telomeric sequences to form unusual structures, 2) the impact of endogenous lesions on the interaction of telomeres with telomere-binding proteins, 3) the repair of endogenous lesions within telomeric sequences, and 4) damage and repair of telomeres in mammalian cells. The proposed studies are innovative in that we are forging into a relatively unexplored area, and we are developing new experimental methods through the integration of multiple basic science disciplines. The results of the proposed studies will reveal critical aspects of chromosome maintenance, potentially explain mechanisms for some genetic alterations observed in human tumors, and provide new insights into the mechanisms of action of some currently used chemotherapy agents.
Human DNA is persistently damaged and must be repaired to prevent degenerative diseases and cancer. The DNA at the ends of human chromosomes is contained in structures called telomeres, and currently, very little is known about the consequences of telomere damage and how telomeres are repaired. The studies proposed here will lead to a better understanding of cancer etiology and suggest new strategies for cancer chemotherapy.
|Theruvathu, Jacob A; Darwanto, Agus; Hsu, Chia Wei et al. (2014) The effect of Pot1 binding on the repair of thymine analogs in a telomeric DNA sequence. Nucleic Acids Res 42:9063-73|
|Liu, Pingfang; Theruvathu, Jacob A; Darwanto, Agus et al. (2008) Mechanisms of base selection by the Escherichia coli mispaired uracil glycosylase. J Biol Chem 283:8829-36|
|Valinluck, Victoria; Sowers, Lawrence C (2007) Inflammation-mediated cytosine damage: a mechanistic link between inflammation and the epigenetic alterations in human cancers. Cancer Res 67:5583-6|
|Valinluck, Victoria; Sowers, Lawrence C (2007) Endogenous cytosine damage products alter the site selectivity of human DNA maintenance methyltransferase DNMT1. Cancer Res 67:946-50|
|Rogstad, Daniel K; Darwanto, Agus; Herring, Jason L et al. (2007) Measurement of the incorporation and repair of exogenous 5-hydroxymethyl-2'-deoxyuridine in human cells in culture using gas chromatography-negative chemical ionization-mass spectrometry. Chem Res Toxicol 20:1787-96|
|Valinluck, Victoria; Liu, Pingfang; Kang Jr, Joseph I et al. (2005) 5-halogenated pyrimidine lesions within a CpG sequence context mimic 5-methylcytosine by enhancing the binding of the methyl-CpG-binding domain of methyl-CpG-binding protein 2 (MeCP2). Nucleic Acids Res 33:3057-64|
|Valinluck, Victoria; Tsai, Hsin-Hao; Rogstad, Daniel K et al. (2004) Oxidative damage to methyl-CpG sequences inhibits the binding of the methyl-CpG binding domain (MBD) of methyl-CpG binding protein 2 (MeCP2). Nucleic Acids Res 32:4100-8|
|Rogstad, Daniel K; Heo, Jiyoung; Vaidehi, Nagarajan et al. (2004) 5-Formyluracil-induced perturbations of DNA function. Biochemistry 43:5688-97|
|Johnson, N A; McKenzie, R; McLean, L et al. (2004) 8-oxo-7,8-dihydroguanine is removed by a nucleotide excision repair-like mechanism in Porphyromonas gingivalis W83. J Bacteriol 186:7697-703|
|Liu, Pingfang; Burdzy, Artur; Sowers, Lawrence C (2003) Repair of the mutagenic DNA oxidation product, 5-formyluracil. DNA Repair (Amst) 2:199-210|
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