Recognition of the base pair-mimic nucleosides by DNA polymerases.

We previously reported that the deoxyadenosine derivative tethering the phenyl group at the N6 position of deoxyadenosine, A(phe) stacked efficiently with the adjacent nucleotide bases at a DNA duplex terminus and in the middle of a DNA duplex. In contrast with the observations for A(phe), this study revealed that the phenyl group of the deoxycytidine derivative, C(phe) located outside the helix and allowed the base pair formation with guanine in a DNA duplex, although its phenyl group could stack with the adjacent DNA bases as efficient as A(phe). Klenow fragment of DNA polymerase I and T7 DNA polymerase selectively incorporated dTTP and dGTP opposite A(phe) and C(phe) in the template DNA, respectively, implying that the conformation of A(phe) differs between in the DNA polymerase and in solution.