Effect of NS5B on cell cycle progression. A, cell cycle analysis in U-2 OS cells. U-2 OS cells were grown in 6-well plates and transfected with 1 μg of pcDNA3.1/myc-His-3×FLAG-NS5B or related empty vectors. Forty-eight hours later, cell cycle distribution was monitored by flow cytometry, and protein expression was detected by Western blot using an anti-FLAG antibody. B and C, establishment of a HepG2 Tet-On NS5B stable cell line. The successful construction of a stable cell line was confirmed by Western blot. Cells induced by 0, 0.01, 0.1, 0.2, 0.5, 1, or 2 μg/ml Dox (B) and cells 0, 2, 4, 8, 12, 24, and 48 h after 1 μg/ml Dox induction (C) were examined using an anti-FLAG antibody or anti-NS5B antibody. D, after induction with different concentrations of Dox for 48 h, the expression of NS5B in HepG2 Tet-On NS5B stable cells was compared with that of the replicon cells (R) using an anti-NS5B antibody. E, cell cycle analysis of a HepG2 Tet-On NS5B stable cell line. Cells were induced with and without 1 μg/ml Dox for 48 h and treated with 200 ng/ml nocodazole 7 h before harvesting and cell cycle analysis. Each experiment was repeated three times. Error bars indicate the S.D.