Ribonucleotide reductase regulatory subunit M2 (RRM2) protein regulates the activity of ribonucleotide reductase (RR) during the G1/early S phase of the cell cycle when DNA replication takes place. This protein provides the essential precursors for DNA synthesis. RRM2 protein catalyzes the biogenesis of deoxyribonucleotides from their corresponding ribonucleotides. RRM2 protein acts as a biomarker for various human cancers. Overexpression of RRM2 gene is observed during tumor progression, cellular response to DNA damage and increased cellular invasiveness.