RRM1 encodes the catalytic subunit of ribonucleotide reductase, an essential enzyme that catalyzes the conversion of ribonucleoside diphosphates to deoxyribonucleoside diphosphates, providing precursors necessary for DNA synthesis and repair 1. The enzyme functions as part of a tetrameric complex with RRM2, playing a critical role in maintaining dNTP pools required for DNA replication 2. Beyond its enzymatic function, RRM1 exhibits non-enzymatic roles in DNA damage response. Upon ionizing radiation, RRM1 translocates to the nucleus where it interacts with USP11 to stabilize E2F1 transcription factor, promoting expression of RAD51AP1 and facilitating homologous recombination repair 1. RRM1 can be phosphorylated at threonine 52 by AMPK, leading to enzyme activation and increased dNTP production for DNA damage repair 3. Clinically, RRM1 expression serves as a predictive biomarker for chemotherapy response, with low expression correlating with sensitivity to gemcitabine and cisplatin-based therapies in non-small cell lung cancer and pancreatic cancer 45. Elevated RRM1 expression is associated with poor prognosis and treatment resistance in various cancers 1. Additionally, RRM1 polymorphisms have been linked to coronary artery disease risk, suggesting broader roles in disease susceptibility 6.