RRM1 is a subunit of ribonucleoside-diphosphate reductase which is constituted by two subunits. Ribonucleoside-diphosphate reductase is an enzyme essential for the production of deoxyribonucleotides prior to DNA synthesis in S phase of dividing cells. RRM1 is one of several genes located in the imprinted gene domain of 11p15.5, an important tumor-suppressor gene region. Alterations in this region have been associated with the Beckwith-Wiedemann syndrome, Wilms tumor, rhabdomyosarcoma, adrenocortical carcinoma, and lung, ovarian, and breast cancer. RRM1 may play a role in malignancies and disease that involve this region.