(a) Relative acetylation (normalized to controls at each day) of indicated histone H3 Lys residues determined by quantification of immunoblot analysis. A representative blot using site specific antibodies is shown in b. Data represent means ± s.e.m. (n = 3). Serial dilutions of protein extracts were applied in western blots to verify linearity before quantification (examples are shown in Supplementary Information, Fig. S4). For calculation details see section on Methods. P values indicate the result of a two-factor ANOVA corrected by Bonferroni post hoc test. (b) Immunoblot of whole-cell extracts of wild-type cells chronologically aged to designated time-points with (+) or without (−) spermidine application. Blots were probed with antibodies against total histone H3 or H3 acetylation sites at the indicated Lys residues. Full scans of blots are available in Supplementary Information, Fig. S5. 