Tobacco-smoking is the single major cause of cancer mortality in the US, and is a risk factor for a number of cancers including lung, upper aero-digestive tract, bladder and pancreas. One of the most powerful carcinogens in tobacco smoke is 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). NNK is bioactivated to potent electrophiles that react to form methyl and 4-(3-pyridyl)-4-oxobutyl (POB) DNA adducts. Role of methyl-DNA adducts in carcinogenesis have been well characterized and the current paradigm is that methyl- DNA adducts are more important than POB-DNA adducts in the etiology of tobacco-induced cancers. However, recently it was found that O2-POB-dT adduct is the most persistent POB adduct in NNK-treated rodents. Our preliminary results show that O2-POB-dT is inefficiently repaired in human cells and is mutagenic in SOS-induced E. coli and mammalian cells. The objective of this application is to determine the mechanisms by which O2-POB-dT forms mutations and is repaired in mammalian cells. These goals will be examined in two specific aims: (1) to determine the polymerases involved in accurate and mutagenic bypass of O2-POB-dT and (2) to determine the mechanisms by which the POB-adducts are repaired. The polymerases involved in the bypass will be determined in cells in which specific polymerases are down regulated by siRNA, and in vitro with purified polymerases. The role of strand switching during translesion synthesis will be examined with cell- free extracts. The repair mechanisms will be evaluated by a combination of ex vivo and in vitro experiments. The roles of NER and BER will be evaluated ex vivo using cells with deficient repair proteins using a HPLC- MS/MS assay to measure levels of DNA adducts. The repair of O2-POB-dT via NER and BER will examined in vitro using synthetic oligodeoxynucleotides. The role of transcription-coupled NER for O6-POB-dG and O2- POB-dT will be probed with a novel modified host cell reactivation.

Public Health Relevance

One way by which tobacco smoke causes cancer is by damaging the DNA in the cell. If the damage is not repaired then when the cell replicates its DNA mistakes (mutations) are made that can lead to cancer. The goal of this project is to understand how the cell repairs and replicates an important class of DNA damage.

National Institute of Health (NIH)
National Institute of Environmental Health Sciences (NIEHS)
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Cancer Etiology Study Section (CE)
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Shaughnessy, Daniel
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Pennsylvania State University
Schools of Medicine
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Prakasha Gowda, A S; Spratt, Thomas E (2017) Active Site Interactions Impact Phosphoryl Transfer during Replication of Damaged and Undamaged DNA by Escherichia coli DNA Polymerase I. Chem Res Toxicol 30:2033-2043
Basu, Ashis K; Pande, Paritosh; Bose, Arindam (2017) Translesion Synthesis of 2'-Deoxyguanosine Lesions by Eukaryotic DNA Polymerases. Chem Res Toxicol 30:61-72
Gowda, A S Prakasha; Krzeminski, Jacek; Amin, Shantu et al. (2017) Mutagenic Replication of N2-Deoxyguanosine Benzo[a]pyrene Adducts by Escherichia coli DNA Polymerase I and Sulfolobus solfataricus DNA Polymerase IV. Chem Res Toxicol 30:1168-1176
Gowda, A S Prakasha; Suo, Zucai; Spratt, Thomas E (2017) Honokiol Inhibits DNA Polymerases ? and ? and Increases Bleomycin Sensitivity of Human Cancer Cells. Chem Res Toxicol 30:715-725
Gowda, A S Prakasha; Lee, Marietta; Spratt, Thomas E (2017) N2 -Substituted 2'-Deoxyguanosine Triphosphate Derivatives as Selective Substrates for Human DNA Polymerase ?. Angew Chem Int Ed Engl 56:2628-2631
Patra, Amritraj; Politica, Dustin A; Chatterjee, Arindom et al. (2016) Mechanism of Error-Free Bypass of the Environmental Carcinogen N-(2'-Deoxyguanosin-8-yl)-3-aminobenzanthrone Adduct by Human DNA Polymerase??. Chembiochem 17:2033-2037
Gowda, A S Prakasha; Spratt, Thomas E (2016) DNA Polymerase ? Rapidly Bypasses O6-Methyl-dG but Not O6-[4-(3-Pyridyl)-4-oxobutyl-dG and O2-Alkyl-dTs. Chem Res Toxicol 29:1894-1900
Gowda, A S Prakasha; Spratt, Thomas E (2016) DNA Polymerases ? and ? Combine to Bypass O(2)-[4-(3-Pyridyl)-4-oxobutyl]thymine, a DNA Adduct Formed from Tobacco Carcinogens. Chem Res Toxicol 29:303-16
Bose, Arindam; Pande, Paritosh; Jasti, Vijay P et al. (2015) DNA polymerases ? and ? cooperatively perform mutagenic translesion synthesis of the C8-2'-deoxyguanosine adduct of the dietary mutagen IQ in human cells. Nucleic Acids Res 43:8340-51
Pattammattel, Ajith; Williams, Christina L; Pande, Paritosh et al. (2015) Biological relevance of oxidative debris present in as-prepared graphene oxide. RSC Adv 5:59364-59372

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