| Summary: | 碩士 === 國立中興大學 === 生命科學系所 === 106 === Genetic information is ensured by proofreading of DNA polymerase and mismatch repair system. But there are still some mismatches occur. If the DNA repair system is disable to repair the mismatches, it will lead to the occurrence of genetic disease or cancer. DNA methylation plays an important role in normal organismal developmentand methylation mainly occurs by the addition of a methyl group on the carbon at position 5 of cytosine, which leads to the formation of 5-methylcytosine at CpG sites in genomic DNA. Echinomycin (Echinomycin , Echi) is an anticancer drug which functions by intercalating into DNA at CpG sites, it related to their ability to intercalate into the DNA duplex with high affinity, thereby interfering with DNA replication and transcription. In the current study, we employed biophysical experiments and X-ray crystallography to investigate the effects of echinomycin binding to methylated DNA and design the d(ACGCCGT)2 DNA duplex containing one, two or three methylated cytosines were used to carry out melting temperature (Tm) and surface plasmon resonance (SPR) studies with echinomycin. Addition of Echi increased the stability of methylated DNA compared to non-methylated DNA. we compared the Echi-bound conformations of methylated versus non-methylated DNA. The higher stability of the methylated DNA-drug complex is contributed by van der Waals contacts between the quinoxaline ring of Echi and the methylation sites of the cytosines and the mC:mC mismatch adopts a "wobble" confirmation projecting into the major groove and minor groove respectively. Our finding provides the basis to develop potential anticancer drugs against diseases involving hypermethylation.
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