Ribonucleoside-Diphosphate Reductase Subunit M2 (RRM2) belongs to the ribonucleoside diphosphate reductase small chain family. The reductase of RRM2 catalyzes the formation of deoxyribonucleotides from ribonucleotides. Synthesis of the encoded protein (M2) is regulated in a cell-cycle dependent fashion. RRM2 supplies the precursors essential for DNA synthesis. RRM2 catalyzes the biosynthesis of deoxyribonucleotides from the corresponding ribonucleotides. Phosphorylation on Ser-20 relieves the inhibitory effect on Wnt signaling.