Research

Many carcinogens and DNA-modifying drugs contain two reactive groups capable of consecutively modifying two sites within the DNA duplex. Carcinogen-DNA adducts can interfere with DNA structure and affect the accuracy of DNA replication, leading to heritable genetic changes and cancer. We employ solid phase synthesis to construct DNA molecules containing site- and stereospecific DNA adducts. These synthetic substrates are subjected to polymerase bypass assays in order to investigate the effects of novel DNA adducts discovered in our lab on DNA replication.

Epigenetics is the mechanism by which cells control the levels of expression of specific genes without changing DNA sequence. Epigenetic regulation is disrupted in many diseases such as cancer and asthma. One examples of an epigenetic mark is 5-methylcytosine. We work to develop inhibitors of the TET proteins, which play a key role in epigenetic regulation of gene expression. Specifically, they oxidize the methyl groups of 5-methylcytosine in DNA, ultimately leading to the removal of these repressive DNA methylation marks and gene reactivation. We employ mass spectrometry to identify protein "readers" of epigenetic marks in DNA and to test how environmental exposures influence epigenetic mechanisms in affected cells and tissues.

Exposure to common antitumor drugs, environmental toxins, transition metals, UV light, ionizing radiation, and free radical-generating systems can result in cellular proteins becoming covalently trapped on DNA. The resulting DNA-protein cross-links (DPCs) are hypothesized to be toxic and mutagenic. Our lab has successfully synthesized site specific DPCs, which we then use to study DPC repair and have developed novel bioanalytical methods to detect and characterize these DPCs in cells and tissues.

Using mass spectrometry tools, we can develop sensitive and specific biomarkers of exposure to carcinogens, which can be used in risk assessment and can provide insight into interethnic and inter-individual differences in carcinogen metabolism. By employing isotope dilution analysis, we are able to accurately quantify carcinogen metabolites or carcinogen-DNA adducts from a variety of matrices, including urine, blood, and cells. Comparing levels of these metabolites or adducts between individuals who are exposed to carcinogens versus those who are not—such as smokers and nonsmokers—gives us a deeper understanding of the mechanisms by which specific carcinogens cause cancer.