AIM: p53-Inducible ribonucleotide reductase small subunit 2 (p53R2) encodes a 351-amino-acid peptide, which catalyzes conversion of ribonucleoside diphosphates to the corresponding deoxyribonucleotides required for DNA replication and repair. A recent study reported that a point mutation (G/T) in the p53 binding sequence in a colon cancer cell line completely impaired p53R2 protein activity.METHODS: We screened the p53R2 gene coding regions and a regulatory region which contains a p53 binding sequence in 100 patients with colorectal adenoma and 100 control subjects using PCR, cold SSCP, and direct DNA sequencing.RESULTS: Although we did not identify genetic variation in all nine exons, four regulatory-region variants were found,of which three were single nucleotide polymorphisms (SNPs) (nt 1 789 C/G, nt 1 928 A/G, 1 933 T/C), and one was 20 bp insertion which replaced a ATTTT between nt 1 831 and 1 835. Additionally, we determined the frequency of these p53R2 variants in a recently concluded case-control study of incident sporadic colorectal adenomas (163 cases and 210 controls).CONCLUSION: Although more detailed functional characterizations of these polymorphisms remain to be undertaken, these polymorphic sites may be useful for identifying alleles associated with mis-splicing, additional transcript factors and, more generally, in cancer-susceptibility association studies.