N2-Substituted 2′-Deoxyguanosine Triphosphate Derivatives as Selective Substrates for Human DNA Polymerase κ

N-2-Alkyl-2'-deoxyguanosine triphosphate (N-2-alkyl-dGTP) derivatives with methyl, butyl, benzyl, or 4-ethynyl-benzyl substituents were prepared and tested as substrates for human DNA polymerases. N-2-Benzyl-dGTP was equal to dGTP as a substrate for DNA polymerase k (pol k), but was a poor substrate for pols beta, delta, eta, iota, or nu. In vivo reactivity was evaluated through incubation of N-2-4-ethynylbenzyl-dG with wild-type and pol k deficient mouse embryonic fibroblasts. CuAAC reaction with 5(6)-FAM-azide demonstrated that only cells containing pol k were able to incorporate N2-4-ethynyl-benzyl-dG into the nucleus. This is the first instance of a Y-family-polymerase-specific dNTP, and this method could be used to probe the activity of pol k in vivo.