Abstract: Objective: To construct a RNAi expression vector aimed at human Nuclear factor E2 p45related factor 2 (Nrf2) gene and it to study the chemoprevention for colon cancer. Methods：Two sequences targeting the ORF of Nrf2 were cloned into the RNA polymerase III based expression vector pSUPER. These recombinants were transfected into HT29 cells. Fluorescence microscope and flow cytometry were used to determine the lipfectin transfection efficiency after being transfected with pEGFPN1 plasmids. The stable cells were selected in medium 48hours after pEGFPN1cotransfected with G418. The expression of Nrf2 was assayed using RTPCR and Western blotting. RTPCR analysis of UGT1A mRNA was performed on the stable cells. Results：The construction of the recombinant expression vector pSUPERNrf2A1，B1 and its control vector pSUPERNrf2A2，B2 was successfully confirmed by the results of enzyme digestion, electrophoresis and sequencing. The transfection efficiency was 30％～75%. The ability of these vectors inhibiting Nrf2 in a transient and stable expression experiment in HT29 cells was compared.Importantly, pSUPER Nrf2B1 was able to significantly knockdown Nrf2 expression. pSUPERNrf2A1 only had a moderate activity, whereas pSUPER Nrf2A2，B2 were inactive in this assay. Moreover, activities of UGT1A was reduced by 20％～30％ in the stable cells transfected with pSUPERNrf2A1，B1 vector. Conclusion：siRNA expression mediated by the pSUPER vector causes efficient, stable, and specific downregulation of Nrf2 gene expression，suggesting the suppression of Nrf2 gene expression results in downregulation of the constructive expression of UGT1A gene.

Key words: Genes, nuclear factor E2 p45related factor 2, Uridine 5′diphosphateglucuronosyltransferase 1A, RNA interference, Colonic neoplasms