N4‐Allyldeoxycytidine: A New DNA Tag with Chemical Sequencing Power for Pinpointing Labelling Sites, Mapping Epigenetic Markers, and In Situ Imaging

Abstract DNA tagging with base analogues has found numerous applications. To precisely record the DNA labelling information, it would be highly beneficial to develop chemical sequencing tags that can be encoded into DNA as regular bases and decoded as mutant bases following a mild, efficient and bioorthogonal chemical treatment. Here we reported such a DNA tag, N 4 ‐allyldeoxycytidine (a 4 dC), for labeling and identifying DNA by in vitro assays. The iodination of a 4 dC led to fast and complete formation of 3 , N 4 ‐cyclized deoxycytidine, which induced base misincorporation during DNA replication and thus could be located at single base resolution. We explored the applications of a 4 dC in pinpointing DNA labelling sites at single base resolution, mapping epigenetic marker N 4 ‐methyldeoxycytidine, and imaging nucleic acids in situ . In addition, mammalian cellular DNA could be metabolically labelled with a 4 dC. Our study sheds light on the design of next generation DNA tags with chemical sequencing power.