miR-34a -induced cell cycle arrest depends on the expression of Rb. (A, D), DNA content distribution by flow cytometry of H2009 (A) and A549 cells (D) treated for 18 h with nocodazole beginning 48 h post-transfection. The percent cells in G1-G0 is shown in the upper panel (n = 3) and a representative histogram of the cell cycle profile is shown in the lower panel. (B, C), Western blot analysis of H2009 (B) and A549 cells (C) subjected to the same conditions as in (A) and (D) using antibodies directed against Rb or phospho-Rb. Protein levels were normalised to α-tubulin.