DNA damages induced by chemical exposure and environmental contaminations have been found to cause significant biological effects in mammalian cells, where cytotoxic and mutagenic DNA lesions caused by alkylating agents had been liked to disease formation and aroused the concerns of public health. In particular, DNA-Protein crosslink (DPC) is classified as a kind of damages that would lead to human diseases, including cancers. Among the DNA lesions, the abasic (AP) sites formed by spontaneous hydrolysis of N-glycosidic bonds linking to modified and native nucleobases are the most abundant and mutagenic ones. Accumulating evidence suggests that lesion-induced interstrand DNA-DNA and DNA-Protein cross-links have intensive biological effects. For instance, interstrand cross-links would int...[ Read more ]

DNA damages induced by chemical exposure and environmental contaminations have been found to cause significant biological effects in mammalian cells, where cytotoxic and mutagenic DNA lesions caused by alkylating agents had been liked to disease formation and aroused the concerns of public health. In particular, DNA-Protein crosslink (DPC) is classified as a kind of damages that would lead to human diseases, including cancers. Among the DNA lesions, the abasic (AP) sites formed by spontaneous hydrolysis of N-glycosidic bonds linking to modified and native nucleobases are the most abundant and mutagenic ones. Accumulating evidence suggests that lesion-induced interstrand DNA-DNA and DNA-Protein cross-links have intensive biological effects. For instance, interstrand cross-links would interrupt the normal DNA metabolic processes such as transcription, replication and repair, resulting in the abnormal growth of unusual genomic DNA that leads to the high possibility of suffering from cancer or aging. Although AP sites are the predominant DNA lesions and are in close proximity with the histone proteins wrapped in the nucleosomes, there is only limited knowledge about the details of DPCs, such as their chemical structures or biological consequences. Therefore, understanding the biological consequences of these damage products would allow a better comprehension of disease evolution and the associated risk assessment methodology. This proposed study addressed the chemical and biological properties of AP site–associated DPCs using a chemical approach. In this study, an HR-MS characterization on peptide for the identification of reaction site of protein and DNA was conducted, followed by LC-MS/MS detection coupled with isotope dilution method on quantitating the number of MMS-induced DNA-Protein crosslinks in E.coli matrix, which was expected to provide an accurate and sensitive method for assessing the role of DPCs in the development of oxidative stress associated with human diseases. The results revealed that the frequency of the proposed DPCs were measured at 0.11-0.12 DPCs/ AP in CT-DNA whereas the results obtained by toxicant-exposure assay in E.coli was 4-time lower (i.e. 0.03 DPCs/AP). This study provided novel information on DNA-Protein crosslinks that could be induced by reactive abasic sites and cysteine residue other than lysine residue, thus suggesting new insights on the structures and formation mechanism of DPCs.