Figure 5.

miR-300 reduces p53-dependent senescence induced by IR. (A) High dose irradiation actives cell cycle suspension in A549 cells. A549 cells were exposed to 10 Gy of X-rays, the cell cycle phase was analyzed at 24, 48 and 72 h post-irradiation. (B) miR-300 abolishes cell cycle suspension. The cell cycle phase of A549 cells transfected with miRNA mimics was analyzed at 48 h after irradiation. (C) Representative cell cycle distribution of cells in (B), the data were analyzed with IDEAS Application v6.0. (D) Growth curves of A549 cells treated with 10 Gy of X-rays. Cells were transfected with P300 or NC before irradiation. Graphs represent mean of a triplicate experiment, error bars represent SD. (E) Colonies were formed 8 days after irradiation in miR-300 overexpression (P300) or p53 inhibition (si-p53) group and photographed using a phase contrast microscope. The arrows indicate colonies. Scale bar, 100 μm. (F) Quantitation of SA-β-gal staining A549 cells with miR-300 overexpression (P300) or p53 inhibition (si-p53) 8 days after treated with 10 Gy of X-rays. Ctrl, control, cells exposed to IR but no transfection; NC, pre-miRNA negative control; P300, pre-miR-300; si-p53, p53 siRNA. *P < 0.05, ** P < 0.01, compared to Ctrl.