Electron attachment dynamics to the guanine (G)-cytosine (C) base pair has been studied from a theoretical viewpoint. The BH&HLYP-level calculations show that the dipole-bound planar (G-C)(-) base pair anion can convert into the nonplanar valence-bound anion with a relatively small barrier. This nonplanar valence-bound anion can further convert into a more stable form via proton-transfer through the N-H center dot center dot center dot N hydrogen-bond from the guanine to cytosine moiety. This excess electron induced proton-transfer process has been studied using quantized ring-polymer molecular dynamics simulations (RPMD) on an interpolated potential energy surface developed on the basis of the B3LYP-level calculations. We compare the RPMD results to the results of classical MD simulations and found that proton-transfer more effectively occurs in quantum RPMD simulations. Both vibrational quantization and corner-cutting mechanism are playing important roles in this proton-transfer process. We have also analyzed the correlation between the proton-transfer motion and other vibrational motions including ring-ring deformation motions using the reactive RPMD trajectories.