Silver(I)-Ion-Mediated Cytosine-Containing Base Pairs: Metal Ion Specificity for Duplex Stabilization and Susceptibility toward DNA Polymerases

Spectroscopic characterization of Ag-I-ion-mediated C-Ag-I-A and C-Ag-I-T base pairs found in primer extension reactions catalyzed by DNA polymerases was conducted. UV melting experiments revealed that C-A and C-T mismatched base pairs in oligodeoxynucleotide duplexes are specifically stabilized by Ag-I ions in 1:1 stoichiometry in the same manner as a C-C mismatched base pair. Although the stability of the mismatched base pairs in the absence of Ag-I ions is in the order C-AC-T>C-C, the stabilizing effect of Ag-I ions follows the order C-C>C-AC-T. However, the comparative susceptibility of dNTPs to Ag-I-mediated enzymatic incorporation into the site opposite templating C is dATP>dTTPdCTP, as reported. The net charge, as well as the size and/or shape complementarity of the metal-mediated base pairs, or the stabilities of mismatched base pairs in the absence of metal ions, would be more important than the stability of the metallo-base pairs in the replicating reaction catalyzed by DNA polymerases.