Senescent cells in vitro and in vivo contain reduced histone content. (A) Immunofluorescent confocal images of histone H3 in control or OIS cells (11 d after activation of ER-RASG12V). Yellow arrows indicate cells with most pronounced SAHF. (B) Quantitative immunofluorescence analysis of histone H3 in RS and OIS cells. Representative of two independent experiments. 