LAUSR

DNA damage plays an important role in the regulation of gene expression and disease processes. Accurate measurement of DNA damage is essential to the discovery of potential disease biomarkers for risk assessment, early clinical diagnosis and therapy moni-toring. However, the low abundance, random location in genomic elements, diversity and the incapability to specifically amplify the DNA damages hinder the accurate quantification of various DNA damages within human genomes. Herein, we demonstrate the inte-gration of enzymatic labelling with single-molecule detection for sensitive quantification of diverse DNA damages. A significant advantage of our method is that only the damaged base-containing DNA sequence can be labelled by the biotin-conjugated nucleo-tide (biotin-dNTP) and separated from the normal DNAs, which greatly improves the detection specificity. In addition, high sensitiv-ity can be achieved by the TdT-induced polymerization of multiple AF488-dUTPs and the introduction of single-molecule detection. This method can measure DNA damage with a detection limit of as low as 1.1 × 10-16 M, and it can distinguish DNA damage at low abundance down to 1.3 ×10-4 %. Importantly, it can provide the information about the occurrence of DNA damage in specific gene and ascertain the DNA damage level in different cancer cell lines, offering a new approach for studying the physiological function of various DNA damages in human diseases.