A Methyl-Engineered DNAzyme for Endogenous Alkyltransferase Monitoring and Self-Sufficient Gene Regulation.

The on-demand gene regulation is crucial for extensively exploring specific gene functions and developing personalized gene therapeutics, which shows great promise in precision medicines. Although some nucleic acid-based gene regulatory tools (antisense oligonucleotides and small interfering RNAs) are devised for achieving on-demand activation, the introduction of chemical modifications may cause undesired side effects, thereby impairing the gene regulatory efficacy. Herein, a methyl-engineered DNAzyme (MeDz) is developed for the visualization of endogenous alkyltransferase (AGT) and the simultaneous self-sufficiently on-demand gene regulation. The catalytic activity of DNAzyme can be efficiently blocked by O-methylguanine (OMeG) modification and specifically restored via the AGT-mediated DNA-repairing pathway. This simply designed MeDz is demonstrated to reveal AGT of varying expression levels in different cells, opening the possibility to explore the AGT-related biological processes. Moreover, the AGT-guided MeDz exhibits cell-selective regulation on the human early growth response-1 (EGR-1) gene, with efficient gene repression in breast cancer cells and low effectiveness in normal cells. The proposed MeDz offers an attractive strategy for on-demand gene regulation, displaying great potential in biomedical applications.