A category of non-planar, twisted polycyclic aromatic hydrocarbons (PAHs), termed fjord region compounds, are extremely potent tumorigens;they include dibenzo[a,l]pyrene which has recently been cited as the most tumorigenic PAH yet identified. These pollutants are released into the environment as combustion products of a variety of fuels, and they contaminate food crops. They are biologically active at the low concentrations present in foods and urban air and are hazardous to the population at large. The origin of the extraordinary carcinogenic potencies of fjord PAHs remains unknown. However, it has recently been shown that several of the bulky DNA adducts that they produce after metabolic activation to diol epoxides, are resistant to nucleotide excision repair (NER), the principal cellular defense against such DNA lesions. Resistance to DNA repair of these adducts is deemed a critical cause for the extraordinary tumorigenicity of the parent chemicals, as they cause the mutations which initiate cancer. However, each environmental fjord PAH gives rise to a complex mixture of stereoisomeric guanine and adenine DNA adducts. Furthermore, the NER susceptibility of each such adduct may vary with DNA base sequence. In this multitude of lesions, the key repair-resistant ones that lead to cancer remain unidentified. Our broad, long-term objective is, working in tandem with our experimental collaborator Prof. N. Geacintov, to identify the NER-resistant adducts and their characteristics using innovative and state-of-the-art modeling methods: we hypothesize that NER-resistance is governed by the structural, dynamic and thermodynamic properties of the PAH-modified DNA. The fjord PAHs selected for detailed study are dibenzo[a,l]pyrene, benzo[g]chrysene, and benzo[c]phenanthrene;we investigate their adducts produced via the well established diol epoxide metabolic activation pathway. These PAHs represent aromatic systems of 6, 5, and 4 rings, respectively, a range optimal for the induction of tumors.
We aim to investigate the many diol epoxide adducts of the three parent PAHs in selected sequences that we hypothesize will alter their NER-susceptibilities. We further aim to determine the characteristic properties and NER susceptibilities of lesions when organized within the histone protein environment of the nucleosome, the basic unit of chromatin structure in the cellular environment. This is an essential first step towards elucidating the functioning of the complex NER machinery in the context of chromatin. We will work hand-in-hand with our experimental collaborator Prof. N. Geacintov: NER data with human cell extracts and including lesion- containing nucleosomes will provide anchors for directly linking our findings with the experimental observations, and our analyses will point to important predictions that will be tested in his laboratory. Our studies will provide the next-generation of biomarkers for PAH exposure, facilitate design of better NER- resistant chemotherapeutics through our gained understanding of NER mechanisms, and advance our capability for genotoxic screening of adducts derived from PAHs present in our environment.
Our work will advance cancer prevention: it will yield novel capability for efficient screening of polycyclic aromatic hydrocarbons to determine their cancer-initiating potency, and provide next-generation biomarkers for PAH exposure that much better signal cancer susceptibility. In addition, design of more efficacious cancer chemotherapeutic agents will be facilitated.
|Fu, Iwen; Cai, Yuqin; Zhang, Yingkai et al. (2016) Entrapment of a Histone Tail by a DNA Lesion in a Nucleosome Suggests the Lesion Impacts Epigenetic Marking: A Molecular Dynamics Study. Biochemistry 55:239-42|
|Mu, Hong; Geacintov, Nicholas E; Zhang, Yingkai et al. (2015) Recognition of Damaged DNA for Nucleotide Excision Repair: A Correlated Motion Mechanism with a Mismatched cis-syn Thymine Dimer Lesion. Biochemistry 54:5263-7|
|Liu, Zhi; Ding, Shuang; Kropachev, Konstantin et al. (2015) Resistance to Nucleotide Excision Repair of Bulky Guanine Adducts Opposite Abasic Sites in DNA Duplexes and Relationships between Structure and Function. PLoS One 10:e0137124|
|Kropachev, Konstantin; Ding, Shuang; Terzidis, Michael A et al. (2014) Structural basis for the recognition of diastereomeric 5',8-cyclo-2'-deoxypurine lesions by the human nucleotide excision repair system. Nucleic Acids Res 42:5020-32|
|Lior-Hoffmann, Lee; Ding, Shuang; Geacintov, Nicholas E et al. (2014) Structural and dynamic characterization of polymerase Îº's minor groove lesion processing reveals how adduct topology impacts fidelity. Biochemistry 53:5683-91|
|RodrÃguez, FabiÃ¡n A; Liu, Zhi; Lin, Chin H et al. (2014) Nuclear magnetic resonance studies of an N2-guanine adduct derived from the tumorigen dibenzo[a,l]pyrene in DNA: impact of adduct stereochemistry, size, and local DNA sequence on solution conformations. Biochemistry 53:1827-41|
|Lee, Yuan-Cho; Cai, Yuqin; Mu, Hong et al. (2014) The relationships between XPC binding to conformationally diverse DNA adducts and their excision by the human NER system: is there a correlation? DNA Repair (Amst) 19:55-63|
|Cai, Yuqin; Geacintov, Nicholas E; Broyde, Suse (2014) Ribonucleotides as nucleotide excision repair substrates. DNA Repair (Amst) 13:55-60|
|Mu, Hong; Kropachev, Konstantin; Chen, Ying et al. (2013) Role of structural and energetic factors in regulating repair of a bulky DNA lesion with different opposite partner bases. Biochemistry 52:5517-21|
|Yang, Jin; Lior-Hoffmann, Lee; Wang, Shenglong et al. (2013) DNA cytosine methylation: structural and thermodynamic characterization of the epigenetic marking mechanism. Biochemistry 52:2828-38|
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