Chromate Reductase Yief From Escherichia Coli Enhances Hexavalent Chromium Resistance Of Human HepG2Cells

Ulike microorganisms which contain chromate reducing agents and therefore mammalian cells are sensitive to Cr(VI). Exposure to high level of Cr(VI) mutagenic and carcinogenic for mammalian cells.In this study, we amplified gene yieF encoding a chromate reductase from Escherichia coli to construct recombined mammalian expression vectors pCI-neo-yieF and pEGFP-Nl-yieF. Vectors were transfected into human HepG2cells in vitro. Stable transfectants HepG2-YieF were established after HepG2cells were transfected by pCI-neo-yieF and screened in G418(400mg/ml) for eight weeks. MTT assay showed that survival rate of recombinant HepG2-YieF was10%higher than that of wild-type HepG2cells after treated with5μM Cr(VI) for48hours. HepG2-YieF also showed significantly higher reducing ability of Cr(VI) than than wild-type HepG2. qRT-PCR results indicated that with the presence of Cr(VI) in cell culture medium, the relative expression of YieF was up-regulated by3.89folds compared with that in medium without Cr(Ⅵ), suggesting that expression of YieF might be induced by Cr(VI) and therefore facilitated Cr(Ⅵ) reduction. The localization of YieF-EGFP fusion protein in HepG2tranfected with pEGFP-Nl-yieF was visualized by confocal microscopy, showing that the fusion protein was distributed in both nucleus and cytoplasm.Our study established a YieF expression model in mammalian cells.