Ribonucleotide reductase M1 polypeptide (RRM1) is one of two non-identical subunits for ribonucleoside-diphosphase, an enzyme which catalyzes the biosynthesis of deoxyribonucleotides from the corresponding ribonucleotide. It provides the precursors necessary for DNA synthesis. RRM1 is present throughout the cell division cycle but downregulated in quiescent cells. RRM1 is involved in carcinogenesis, tumor progression, and the response of non-small-cell lung cancer (NSCLC) to chemotherapy.