Ribonucleotide reductase large subunit M1 (RRM1) forms a holoenzyme with small subunits to provide deoxyribonucleotides for DNA synthesis and cell proliferation.Here,we reported a non-RR role of the catalytic subunit protein RRM1 and related pathway in inhibiting colorectal cancer (CRC) metastasis.Ectopic overexpression of the wild-type RRM 1,and importantly,its Y738F mutant that lacks RR enzymatic activity,prevented the migration and invasion of CRC cells by promoting PTEN transactivation.