Fig. 1.

EGFP inhibits cell proliferation and induces cell death in DNA repair protein Ku80-deficient hamster cells, xrs-6. (A) Xrs-6 cells were transfected with pEGFP (upper panel) or pEYFP (lower panel). Two days following transfection, the cells were fixed and stained with DAPI. Three representative fields (more than 300 cells, each) were scored for each transfection and data represent the mean ± standard deviations. A significant difference is represented by * (P < 0.05, t test). Arrows indicate the cells showing an abnormal morphology. White panel: an enlarged image of the typical cell. (B) Comparison of EGFP or EYFP expression levels in xrs-6 and CHO-K1 cells 2 days after transfection. Total cell lysates from each cell line following transfection were analyzed by Western blot analysis using an anti-Ku70, anti-Ku80, anti-GFP or anti-β-actin antibody. Both EGFP and EYFP were detected by the anti-GFP antibody used. Short, short exposure; long, long exposure. (C) Imaging of living EYFP- (a, a’, c, c’) or EGFP-transfected (b, b’, d, d’, e, e’, f, f’) xrs-6 (c–f, c’–f’) or CHO-K1 (a, a’, b, b’) cells. Typical images of cells that underwent division (a–d’), nondividing cells with normal nucleus (e, e’) or nondividing cells with a condensed nucleus (f, f’) are shown. (D) The graph shows the percentage of EGFP-positive divided xrs-6 cells 2 days after transfection with pEGFP or pEGFP-Ku80. (E) The graph shows the percentage of cells with apoptosis-like morphology in the non-divided xrs-6 cells 2 days after transfection with pEGFP or pEGFP-Ku80. Error bars represent SD.