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8-oxo guanine DNA glycosylase (8-oxoG DNA glycosylase), a crucial DNA repair enzyme, is essential for maintaining genome integrity and preventing diseases caused by DNA oxidative damage. Imaging 8-oxoG DNA glycosylase in living cells requires a dependable technique. In this study, we designed a DNAzyme-modified DNA tetrahedral nanomachine (DTDN) powered by 8-oxoG restoration. Incorporating a molecular beacon probe (MB), the constructed platform was used for amplified in situ monitoring of 8-oxoG DNA glycosylase. Under normal conditions, duplexing with a complementary strand modified with two 8-oxoG sites inhibited the activity of DNAzyme. The restoration of DNAzyme activity by the repair of intracellular 8-oxoG DNA glycosylase on 8-oxoG bases can initiate a signal amplification reaction. This detection system can detect 8-oxoG DNA glycosylase activity linearly between 0 and 20 U mL−1, with a detection limit as low as 0.52 U mL−1. Using this method, we were able to screen 14 natural compounds and identify 6 of them as 8-oxoG DNA glycosylase inhibitors. In addition, a novel approach was utilized to assess the activity of 8-oxoG DNA glycosylase in living cells. In conclusion, this method provides a universal tool for monitoring the activity of 8-oxoG DNA glycosylase in vitro and in living cells, which holds great promise for elucidating the enzyme's functionality and facilitating drug screening endeavors. [ABSTRACT FROM AUTHOR]

The nucleus is considered the ideal target for anti‐tumor therapy because DNA and some enzymes in the nucleus are the main causes of cell canceration and malignant proliferation. However, nuclear target drugs with good biosafety and high efficiency in cancer treatment are rare. Herein, a nuclear‐targeted material MeTPAE with aggregation‐induced emission (AIE) characteristics was developed based on a triphenylamine structure skeleton. MeTPAE can not only interact with histone deacetylases (HDACs) to inhibit cell proliferation but also damage telomere and nucleic acids precisely through photodynamic treatment (PDT). The cocktail strategy of MeTPAE caused obvious cell cycle arrest and showed excellent PDT anti‐tumor activity, which offered new opportunities for the effective treatment of malignant tumors. [ABSTRACT FROM AUTHOR]

As a highly conserved damage repair protein, Fpg can specifically recognize and digest 8-oxoG from a damaged DNA backbone. Meanwhile, DNAzyme, a single-stranded DNA with enzymatic activity, can cleave RNA in the presence of cofactors. In this study, we established a highly sensitive method for Fpg assay using a DNAzyme-mediated signal cascade amplification strategy. Based on the Fpg-dependent fluorescence response of the “turn-on” manner, we could reliably determine Fpg activity down to 0.14 U mL−1 with a linear response from 0.10 to 40 U mL−1 under optimal conditions. In addition, this strategy was successfully applied to analyze the kinetic parameter of Fpg with Km of 0.061 μM. Furthermore, the developed sensing system was used to screen the regulators of Fpg from natural compounds and antibiotics. These results indicated that all of the 14 natural compounds and 6 kinds of antibiotics deferentially showed an active effect on Fpg in vitro. In summary, these results show that the method not only provides an alternative for monitoring Fpg activity but also shows great potential for drug screening in the future. [ABSTRACT FROM AUTHOR]

As a highly conserved damage repair protein, RNase H can specifically hydrolyze RNA in DNA-RNA chimeric strands. DNAzyme, a synthetic single-stranded DNA consisting of binding and catalytic sites, can cleave RNA in the presence of cofactors. In this study, we establish a highly sensitive RNase H assay assisted with DNAzyme's cleavage property. A DNA-RNA chimeric strand, which contains DNAzyme sequences, is used as the hydrolysis substrate of RNase H. The RNase H hydrolysis of the chimeric substrate results in the release of DNAzyme. Subsegment DNAzyme digest, a molecular beacon, causes a "turn-on" fluorescence signal by disrupting its hairpin structure. Furthermore, the fluorescence signal is amplified by cyclic digestion of DNAzyme to the substrate of molecular beacon. Under the optimal conditions, the detection limit of RNase H is 0.01 U/mL, which is superior to those of several alternative approaches. Additionally, the method was further used for RNase H detection in heterogeneous biological samples as well as to investigate the effects of natural compounds on this enzyme. In summary, these results show that the method not only provides a universal platform for monitoring RNase H activity but also shows great potential in biomedical studies and drug screening. [ABSTRACT FROM AUTHOR]

A label-free, ultra-sensitive and turn-on method for detecting RNase A has been developed using enhanced DNA-templated silver nanoclusters (DNA-AgNCs) as the fluorescence probe. In this system, an RNA strand, which can perfectly hybridize with DNA template of nanocluster synthesis, was applied to lock the fluorescent signal of DNA-AgNCs by forming an RNA/DNA duplex. Meanwhile, the hybridized RNA/DNA duplex was used as the substrate of RNase A. The fluorescence signal of AgNCs was restored due to the degradation of RNA by RNase A. From the fluorescence signal change of this system caused by RNase A, it was found that the fluorescence signal showed a positive linear relation with RNase A concentration in the range from 0.2 pg/μL to 10 pg/μL with a detection limit of 0.098 pg/μL. Except for potential inhibitor screening and the kinetic study of this enzyme, this strategy was further used for monitoring dynamic change of RNase A in living cells successfully. In summary, the simple and sensitive method for RNase A assay can be hopefully used for drug screening in vitro and in vivo. Image 1 • Synthetic DNA-enhanced silver nanoclusters display high and stable fluorescence optical properties. • This method demonstrates the high sensitivity and specificity of RNase A detection. • This strategy was successfully used to monitor dynamic changes of RNase A in living cells after screening for the potential inhibitor. [ABSTRACT FROM AUTHOR]