Senescence-associated loss of histones is V-ATPase dependent. (A) Bafilomycin A1 (BafA1) blocks the loss of nuclear histone H3 content in cells undergoing OIS. BafA1 was added to cells at 50 nM on day 5 after RASG12V induction. Cells were harvested 24 h later, and stained for histone H3. Bars, 10 µm. (B) Quantitative histone H3 immunofluorescence in cells from A. Single representative experiment out of three repeats. (C) RASG12V-induced OIS cells were treated with BafA1 as described in A and then assessed for histones by Western blot. LC3 I/II has been used as a control for BafA1 activity. Lysates from 10,000 cells were loaded per well. (D) BafA1 blocks the accumulation of H3cs.1 in cells undergoing OIS. (E) BafA1 and concanamycin A (Con A) block the accumulation of H3cs.1 in RS cells.