• DNA demethylation;
  • DNA methylation;
  • DNA replication;
  • modified nucleotides


5-Ethynyl-2′-deoxycytidine triphosphate (EdCTP) was synthesized as a probe to be used in conjunction with fluorescent labeling to facilitate the analysis of the in vivo dynamics of DNA-centered processes (DNA replication, repair and cytosine demethylation). Kinetic analysis showed that EdCTP is accepted as a substrate by Klenow exo and DNA polymerase β. Incorporation of 5-ethynyl-2′-deoxycytidine (EdC) into DNA by these enzymes is, at most, modestly less efficient than native dC. EdC-containing DNA was visualized by using a click reaction with a fluorescent azide, following polymerase incorporation and T4 DNA ligase mediated ligation. Subsequent experiments in mouse male germ cells and zygotes demonstrated that EdC is a specific and reliable reporter of DNA replication, in vivo.