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Principal Investigator: Seongmin Lee
Organization: UNIVERSITY OF TEXAS AT AUSTIN
Fiscal Year: 2024
Award: $343,610
Funding agency: National Institute of Environmental Health Sciences
ABSTRACT
Alkylation DNA damage caused by alkylating agents promotes mutations and cancer development. Guanine N7
is targeted by a wide range of alkylating mutagens, carcinogens, and anticancer agents, producing the cationic
N7-alkylguanine (N7-alkylG) adducts as major lesions. These lesions have half-lives of several hours to days in
DNA and thus can affect DNA replication and transcription. The positively charged N7-alkylG lesions can also
undergo further modification to generate secondary lesions such as alkyl-formamidopyrimidine (alkyl-FapyG)
adducts. The recognition, repair, and mutagenesis mechanisms of many mutagen/carcinogen-induced N7-
alkylG and alkyl-FapyG lesions, except for a few lesions such as N7-aflatoxin B1-G and aflatoxin B1-FapyG
adducts, remain poorly characterized, thereby precluding a complete understanding of the contribution of these
major lesions to mutations and cancer development. For example, the mutagenic properties of the predominant
N7-alkylG adducts produced by the cancer-promoting styrene oxide are unknown. This knowledge gap has
been due in part to the technical difficulty in preparing a site-specific N7-alkylG- and alkyl-FapyG-containing
DNA, which is ascribed to the rapid depurination of N7-alkylG nucleosides and the facile isomerization of alkyl-
FapyG during solid-phase DNA synthesis. To overcome the stability issue of N7-alkylG nucleosides, we have
developed a 2’-fluorine technology that prevents spontaneous depurination by increasing the stability of N7-
alkylG nucleosides. To solve the isomerization problem of alkyl-FapyG, we have taken a post-synthetic
approach that produces alkyl-FapyG-containing DNA from N7-alkylG-containing DNA. Our preliminary studies
show that guanine N7 alkylation can influence base-pairing properties by facilitating the formation of the rare
enol tautomer, syn base conformation, and/or intercalation. Our central hypothesis is that N7-alkylG and alkyl-
FapyG adducts promote mutations and cancer development by altering the base-pairing properties of the
damaged guanine. Our long-term research goal is to elucidate the biological impacts of chemically labile
alkylation damages and their secondary lesions using innovative approaches such as the 2’-F chemistry, the
polβ host-guest-complex system, and post-synthetic DNA modification. The objective is to dissect the biological
consequences of N7-alkylG and alkyl-FapyG lesions induced by potent alkylating mutagens and anticancer
agents such as nicotine-specific nitrosamine, styrene oxide, nitrogen mustards, and N-methylbenzyl nitrosamine.
To accomplish this objective, we will characterize the base-pairing properties and the recognition, mutagenesis,
and repair mechanisms of N7-alkylG and alkyl-FapyG adducts using combined tools of synthetic, biochemical,
structural biology, and cellular approaches. The successful execution of the proposed programs will greatly
advance our knowledge of the impact of carcinogen/drug-induced N7-alkylG and alkyl-FapyG lesions on the
base pair conformation, stability, tautomerism, mutagenesis, recognition, and repair, thereby providing important
insights into the alkylation damage-induced mutations and cancer development.
Terms: <Abscission><Affect><Aflatoxin B1><Alkylating Agents><Alkylation><Alkylators><Anti-Cancer Agents><Antineoplastic Agents><Antineoplastic Drugs><Antineoplastics><Assay><Base Excision Repairs><Base Pairing><Bioassay><Biochemical><Biological><Biological Assay><Bypass><Cancer Causing Agents><Cancer Drug><Cancer Induction><Cancers><Candidate Disease Gene><Candidate Gene><Carcinogens><Catalysis><Causality><Cell Body><Cells><Charge><Chemicals><Chemistry><Chloramin><Chlorethazine><Chlormethine><Complex><DNA><DNA Alkylation><DNA Base Excision Repair><DNA Damage><DNA Injury><DNA Maintenance><DNA Modification><DNA Modification Process><DNA N-glycosidase><DNA Polymerases><DNA Replication><DNA Stability><DNA Structure><DNA Synthesis><DNA biosynthesis><DNA glycosylase><DNA-Dependent DNA Polymerases><DNA-Directed DNA Polymerase><Deoxyribonucleic Acid><Depurination><Development><Dissociation><Drugs><Equilibrium><Etiology><Excision><Extirpation><F element><Fluorine><Frequencies><Gene Transcription><Genes><Genetic Alteration><Genetic Change><Genetic Transcription><Genetic defect><Genetics-Mutagenesis><Genotoxins><Goals><Guanine><HN-2><HN2><Heterogeneity><Hour><Human><Imidazole><In Vitro><Individual><Induced DNA Alteration><Induced Mutation><Induced Sequence Alteration><Isomerism><Ketones><Kinetics><Knowledge><Lesion><Light><Malignant Neoplasms><Malignant Tumor><Mechlorethamine><Mediating><Medication><Methylchlorethamine><Modern Man><Modification><Molecular Configuration><Molecular Conformation><Molecular Stereochemistry><Mustine><Mutagenesis><Mutagenesis Molecular Biology><Mutagens><Mutation><Neoplastic Disease Chemotherapeutic Agents><Nicotine><Nitrogen Mustard><Nitrosamines><Nucleosides><Nucleotide Synthesis><Nucleotides><Oncogens><Pharmaceutical Preparations><Phase><Photoradiation><Plasmids><Polymerase><Process><Property><Public Health><Publishing><Purines/Pyrimidines/Nucleotides/Nucleic Acids Metabolism><RNA Expression><Relaxation><Removal><Reporter><Reporting><Research><Role><Secondary Lesion><Site><Solid><Structure><Surgical Removal><System><Technology><Testing><Tobacco><Transcription><Tumor-Specific Treatment Agents><adduct><anomer><anti-cancer drug><anti-tumor agent><balance><balance function><base><bases><biologic><carcinogenesis><causation><chloromethine><conformation><conformational><conformational state><conformationally><conformations><developmental><disease causation><drug/agent><endonuclease><enol><genome mutation><genotoxic agent><genotoxicity><in vivo><innovate><innovation><innovative><insight><intercalation><ionization><isomer><knock-down><knockdown><malignancy><melting><mutation assay><neoplasm/cancer><nucleotide metabolism><oncogenic agent><phenyloxirane><prevent><preventing><programs><repair><repair model><repaired><resection><social role><structural biology><styrene 7,8-oxide><styrene oxide><success><synthetic DNA><synthetic construct><tautomer><tool>