Loss of H4-K16 acetylation is specific to senescent cells and correlates with DNA compaction. A) DNA content by flow cytometry. The percentage of cells incorporating bromodeoxy-uridine (BrdU) after 24 hours of incubation is indicated. B) DNA 4',6'-diamidino-2-phenylindole (DAPI) staining of representative nuclei and corresponding DAPI coefficient of variation (CV) values. C) Boxplots of DAPI CV (n > 70, from one representative experiment of two biological replicates). *DNA compaction statistically different from Prolif. or PD 43 (P < 10-5, Welch t-test). D) Relative abundance of H4 acetylation states measured at the protein level on deconvoluted mass spectra (Figure 3). Error bars show SD of at least three biological replicates. Prolif.: proliferating WI-38hTERT/GFP-RAF-ER; SenRAF: WI-38hTERT/GFP-RAF-ER + 20 nM 4-HT (5 days); Quiescent: serum-starved WI-38hTERT/GFP-RAF-ER (5 days); SenETO: WI-38hTERT/GFP-RAF-ER + 20 μM etoposide (5 days); Control 4-HT: WI-38hTERT + 20 nM 4-HT (5 days); PD 43: population doubling 43, proliferating WI-38 cells; PD 65: replicatively senescent WI-38 population.