a, Western analysis of ING2 expression in the indicated cell lines. *, endogenous ING2. b, ING2 is required for repression of cyclin D1 expression in response to doxorubicin (dox). Quantitative PCR of cyclin D1 mRNA, with or without doxorubicin (0.2μg ml−1, 24 h), in wild-type (“WT”), knockdown (“KD”) and knockdown reconstituted with ING2 (“KD+ING2”) cell lines. c, Impaired activity of mutant ING2 proteins in reconstitution of doxorubicin-dependent cyclin D1 repression, as in b, relative to wild-type ING2 (“KD+ING2”). In b and c, error bars indicate the s.e.m. of triplicate experiments; P-values < 0.01. d-f, DNA-damage-dependent increase of ING2-HDAC1 occupancy at the cyclin D1 promoter requires methylated H3K4-binding. ChIPs with antibodies to Flag (d), HDAC1 (e) and H4K8ac (f) at the cyclin D1 promoter in the indicated cell lines, with or without doxorubicin (2μM, 1 h). Error bars indicate the s.e.m. of at least three independent experiments. P-values < 0.05. g, Western analysis of cyclin D1 protein in the indicated cell lines with or without doxorubicin (0.2μg ml−1, 24 h). h, Impaired doxorubicin sensitivity following ING2 knockdown or reconstitution with H3K4me3-binding-defective ING2. Relative cell viability is normalized to untreated cells. Error bars indicate the s.e.m. of 3–6 independent experiments.