RRM2 also known as R2 is a subunit of ribonucleotide reductase, an essential enzyme complex responsible for the synthesis and maintenance of deoxyribonucleoside triphosphates (dNTPs), which are vital for DNA replication and repair. RRM2 is localized in the cytoplasm and acts as the limiting factor for the catalytic activity of ribonucleotide reductase, with expression tightly correlated to the S-phase of the cell cycle. This regulation ensures a sufficient supply of dNTPs necessary for DNA synthesis, thereby maintaining genomic stability and enabling proper cell division. RRM2 interacts with the RRM1 subunit to form the active ribonucleotide reductase complex, facilitating efficient dNTP production during periods of rapid cell proliferation and in response to DNA damage.