Abstract
The generation of 8-oxo-7,8-dihydroguanine (8-oxoG) in DNA is a common type of DNA damage after exposure to reactive oxygen species or drugs. Human 8-oxoG DNA glycosylase/AP lyase (hOGG1) is a kind of base excision repair enzyme specifically used to repair the base excision of 8-oxoG. In this paper, we develop a novel, simple and sensitive strategy for the detection of hOGG1 activity based on the self-assembly of the active HRP-mimicking DNAzyme coupled with lambda exonuclease (λ exo) cleavage. We designed two DNA oligonucleotides that are fully complementary to each other. One is modified with 8-oxoG, the other contains the G-quadruplex DNAzyme sequence. The two single-stranded DNA (ssDNA) firstly hybridize to form a DNA duplex containing an 8-oxoG. In the presence of hOGG1, the formed DNA duplex is selectively cleaved at the 8-oxoG site, yielding a new DNA duplex with a recessed 5′-phosphate terminus. Upon treatment with λ exo, the 5′-phosphoryl ssDNA of the new DNA duplex is digested by λ exo, releasing the G-quadruplex DNAzyme sequence. After addition of hemin, the G-quadruplex–hemin complex is used as a peroxidase-mimicking DNAzyme, catalyzing H2O2-mediated oxidation of 2,2′-azinobis(3-ethylbenzothiozoline)-6-sulfonic acid (ABTS2−) to generate a colorimetric signal. The activity of hOGG1 is directly related to UV/Vis absorption intensity. The results revealed that the method allowed a sensitive quantitative assay of the hOGG1 concentration with a wide range from 0.05–32 U mL−1 and a low detection limit of 0.01 U mL−1.
Published Version
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