We hypothesize that a group of oxidative DNA damages, including 8-oxoguanine, formamidopyrimidines and tandem lesions, play important roles in the etiology of human cancer via the mutagenic and genotoxic effects of these lesions in certain important sequences of cancer genes. In this application, we propose to study the biological effects of a subset of these lesions. We have three specific aims.
In aim 1, synthesis and characterization of oligonucleotides containing tandem base lesions in DNA will be carried out. Tandem lesions formed by ionizing radiation, transition metal/H2O2, or other radical- mediated processes include abasic site adjacent to 8-oxoguanine, S- and R-8,5'-cyclo-2'- deoxyguanosine, and intrastrand vicinal guanine-thymine cross-link. We shall determine the structural effects of these damages in DNA by thermal melting, circular dichroism, and NMR.
In aim 2, single stranded plasmid or viral vectors containing these lesions will be constructed. Mutagenicity and repair studies of the site-specific lesions will be carried out in Escherichia coli and in mammalian cells. For example, we shall determine how mutagenicity of 8-oxoguanine might be influenced when it is present as part of a tandem DNA damage. We shall investigate if Fapy.dG, the guanine-thymine vicinal cross- link, S- and R-8, 5'-cyclo-2'-deoxyguanosine are mutagenic, genotoxic, or both in mammalian cells.
In aim 3, we shall construct duplex plasmid vectors with these lesions, which will be used to examine the extent of lesion bypass by extracts of normal and repair- or replication-altered mammalian cells (e.g., isogenic mouse embryonic fibroblasts and cells that express modulated levels of DNA polymerases encoded by REV1, REV3, RAD18, etc. genes). We hope to contribute toward a deeper insight of the effects of oxidative DNA damages.

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National Institute of Environmental Health Sciences (NIEHS)
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Special Emphasis Panel (ZRG1-ONC-L (02))
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Reinlib, Leslie J
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University of Connecticut
Schools of Arts and Sciences
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Malik, Chanchal K; Das, Rajat S; Basu, Ashis K (2013) Synthesis of [1,3, NH2-(15)N3] (5'S)-8,5'-cyclo-2'-deoxyguanosine. J Labelled Comp Radiopharm 56:376-81
Pande, Paritosh; Das, Rajat S; Sheppard, Clayton et al. (2012) Repair efficiency of (5'S)-8,5'-cyclo-2'-deoxyguanosine and (5'S)-8,5'-cyclo-2'-deoxyadenosine depends on the complementary base. DNA Repair (Amst) 11:926-31
Huang, Hai; Das, Rajat S; Basu, Ashis K et al. (2012) Structures of (5'S)-8,5'-Cyclo-2'-deoxyguanosine Mismatched with dA or dT. Chem Res Toxicol 25:478-90
Das, Rajat S; Samaraweera, Milinda; Morton, Martha et al. (2012) Stability of N-glycosidic bond of (5'S)-8,5'-cyclo-2'-deoxyguanosine. Chem Res Toxicol 25:2451-61
Huang, Hai; Das, Rajat S; Basu, Ashis K et al. (2011) Structure of (5'S)-8,5'-cyclo-2'-deoxyguanosine in DNA. J Am Chem Soc 133:20357-68
Raychaudhury, Paromita; Basu, Ashis K (2011) Genetic requirement for mutagenesis of the G[8,5-Me]T cross-link in Escherichia coli: DNA polymerases IV and V compete for error-prone bypass. Biochemistry 50:2330-8
Jasti, Vijay P; Das, Rajat S; Hilton, Benjamin A et al. (2011) (5'S)-8,5'-cyclo-2'-deoxyguanosine is a strong block to replication, a potent pol V-dependent mutagenic lesion, and is inefficiently repaired in Escherichia coli. Biochemistry 50:3862-5
Jasti, Vijay P; Spratt, Thomas E; Basu, Ashis K (2011) Tobacco-specific nitrosamine-derived O2-alkylthymidines are potent mutagenic lesions in SOS-induced Escherichia coli. Chem Res Toxicol 24:1833-5
Brown, Kyle L; Roginskaya, Marina; Zou, Yue et al. (2010) Binding of the human nucleotide excision repair proteins XPA and XPC/HR23B to the 5R-thymine glycol lesion and structure of the cis-(5R,6S) thymine glycol epimer in the 5'-GTgG-3' sequence: destabilization of two base pairs at the lesion site. Nucleic Acids Res 38:428-40
Weng, Mao-wen; Zheng, Yi; Jasti, Vijay P et al. (2010) Repair of mitomycin C mono- and interstrand cross-linked DNA adducts by UvrABC: a new model. Nucleic Acids Res 38:6976-84

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